{"gene":"RBBP8","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":2007,"finding":"Human CtIP (RBBP8) is required for DNA double-strand break (DSB) resection in S and G2 phases, is recruited to DSBs exclusively in S/G2, physically and functionally interacts with the MRE11 complex, and is required for RPA and ATR recruitment and ATR activation following DSBs. CtIP shares sequence homology with yeast Sae2.","method":"siRNA depletion, laser micro-irradiation, co-immunoprecipitation, immunofluorescence, cell-cycle fractionation","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Co-IP, functional depletion, localization), widely replicated across the field","pmids":["17965729"],"is_preprint":false},{"year":1998,"finding":"The BRCT domains of BRCA1 interact in vivo with CtIP; tumor-associated mutations in the BRCT motifs ablate this interaction.","method":"Sos recruitment yeast two-hybrid system, in vivo interaction assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — replicated by multiple subsequent studies using reciprocal Co-IP and structural methods","pmids":["9738006"],"is_preprint":false},{"year":2004,"finding":"CtIP interacts with BRCA1 BRCT domains in a phosphorylation-dependent manner (phospho-Ser327); the CtIP/BRCA1 complex exists specifically in G2 phase and is required for DNA damage-induced Chk1 phosphorylation and the G2/M checkpoint.","method":"Co-immunoprecipitation, cell cycle synchronization, phosphorylation assays, siRNA depletion","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, phosphorylation-dependence shown, cell-cycle specificity established, replicated by multiple labs","pmids":["15485915"],"is_preprint":false},{"year":2005,"finding":"Crystal structure of BRCA1 BRCT repeats bound to CtIP phosphopeptide (residues 322–333, phospho-Ser327) at 2.5 Å resolution; Phe330 and phospho-Ser327 anchor the peptide; the cancer-associated BRCA1 M1775R mutation sterically clashes with CtIP Phe330, disrupting the interaction.","method":"X-ray crystallography, isothermal titration calorimetry","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional validation (ITC affinity measurement, mutant analysis)","pmids":["16101277"],"is_preprint":false},{"year":2006,"finding":"BRCA1 RING domain catalyzes CtIP ubiquitination in a manner dependent on phosphorylation-mediated CtIP–BRCA1 BRCT interaction; this ubiquitination does not target CtIP for proteasomal degradation but instead promotes chromatin association of CtIP after DNA damage and participation in G2/M checkpoint control.","method":"In vitro ubiquitination assay, co-immunoprecipitation, chromatin fractionation, cell cycle checkpoint assays","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro ubiquitination reconstitution plus cellular functional assays, single lab with multiple orthogonal methods","pmids":["16818604"],"is_preprint":false},{"year":2009,"finding":"CDK-mediated phosphorylation of CtIP at Thr-847 is required for DSB resection and homologous recombination; phospho-mimetic T847E allows resection even after CDK inhibition, while T847A impairs resection. Mutating Ser-327 specifically abolishes BRCA1 interaction and HR but not MMEJ.","method":"Site-directed mutagenesis, CDK inhibitor treatment, RPA focus formation assay, chromosomal rearrangement assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis of specific phosphorylation sites with functional readouts; independently replicated","pmids":["19202191"],"is_preprint":false},{"year":2009,"finding":"CtIP-S327 phosphorylation and BRCA1 recruitment acts as a molecular switch directing DSB repair from error-prone end-joining (MMEJ) in G1 to error-free HR in S/G2; CtIP-S327A cells are specifically defective in HR but not MMEJ.","method":"DT40 gene targeting, site-directed mutagenesis, single-stranded DNA assays, repair pathway assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis in DT40 cells with separation-of-function mutants, replicated by multiple labs","pmids":["19357644"],"is_preprint":false},{"year":2009,"finding":"CtIP translocation to DSBs depends on the MRN complex, ATM kinase activity, and a direct DNA-binding motif in CtIP; CtIP promotes the transition from DSB sensing to resection downstream of ATM activation.","method":"Xenopus egg extracts, laser-induced DSBs in human cells, ATM inhibition, direct DNA-binding assay","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — combination of cell-free reconstitution (Xenopus) and human cell assays with domain mapping","pmids":["20064462"],"is_preprint":false},{"year":2008,"finding":"BRCA1 forms a cell cycle-dependent complex with CtIP and MRN; complex formation (especially IR-enhanced BRCA1–MRN association) requires CDK activity; CtIP directly interacts with Nbs1; the complex is critical for ssDNA formation and HR.","method":"Co-immunoprecipitation, CDK inhibition, IR treatment, ssDNA/BrdU assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP with CDK dependency and functional ssDNA readout; independently replicated","pmids":["18171670"],"is_preprint":false},{"year":2016,"finding":"Phosphorylated CtIP acts as a co-factor of MRE11 endonuclease within the MRN complex; this function absolutely requires CtIP phosphorylation at Thr-847 and NBS1; the MRN–phospho-CtIP complex preferentially cleaves 5'-terminated DNA strands near DSBs to initiate resection.","method":"Reconstituted in vitro nuclease assay with recombinant human proteins, phosphorylation-site mutagenesis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — biochemical reconstitution with purified components and mutagenesis; independently replicated","pmids":["27889449"],"is_preprint":false},{"year":2014,"finding":"Human CtIP has intrinsic 5' flap endonuclease activity on branched DNA, independent of MRN; phosphorylation at damage-dependent sites (not S327/T847) is essential for catalytic activity; catalytic mutant CtIP is deficient in processing topoisomerase adducts and radiation-induced breaks but not endonuclease-generated breaks.","method":"Recombinant protein purification, in vitro endonuclease assay, phosphorylation-site mutagenesis, cell-based repair assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution of endonuclease activity with mutagenesis and cellular validation, single lab with multiple orthogonal approaches","pmids":["24837676"],"is_preprint":false},{"year":2015,"finding":"X-ray crystallography and biophysical analyses show that the N-terminal domain of human CtIP forms a stable homotetramer via a 'dimer-of-dimers' architecture; a point mutation abolishing tetramerization (but preserving dimerization) causes strong defects in DNA-end resection and gene conversion in cells.","method":"X-ray crystallography, biophysical (SEC-MALS, AUC), site-directed mutagenesis, HR reporter assays","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional mutagenesis validation in cells","pmids":["25558984"],"is_preprint":false},{"year":2010,"finding":"SIRT6 deacetylates CtIP to promote DNA end resection; a non-acetylatable CtIP mutant alleviates the resection defect caused by SIRT6 depletion. NOTE: this paper was subsequently retracted.","method":"Co-immunoprecipitation, site-directed mutagenesis, RPA/ssDNA focus assays (RETRACTED paper)","journal":"Science","confidence":"Low","confidence_rationale":"Tier 3 / Weak — paper was formally retracted; findings should not be considered established","pmids":["20829486"],"is_preprint":false},{"year":2012,"finding":"ATR phosphorylates CtIP at T818 (Xenopus; T859 in human) in response to DSBs; non-phosphorylatable CtIP (T818A) fails to bind chromatin or initiate resection; ATM activity is required for an early resection step leading to ATR activation and CtIP-T818 phosphorylation.","method":"Xenopus egg extract system, mass spectrometry, chromatin binding assay, phospho-specific antibodies, mutagenesis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Moderate — cell-free reconstitution in Xenopus with MS identification of phosphorylation site and mutagenesis validation","pmids":["23273981"],"is_preprint":false},{"year":2013,"finding":"CDK phosphorylation of CtIP induces its interaction with the FHA and BRCT domains of Nbs1; CDK-dependent CtIP–Nbs1 interaction is a prerequisite for ATM to phosphorylate CtIP upon DNA damage, promoting BLM and Exo1 recruitment and HR.","method":"Phosphopeptide pull-down, co-immunoprecipitation, phosphorylation assays, siRNA depletion, HR reporter","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple Co-IPs and functional assays establishing the CDK-ATM-CtIP-Nbs1 axis, single lab","pmids":["23468639"],"is_preprint":false},{"year":2012,"finding":"Mre11 controls CDK2-dependent CtIP phosphorylation and BRCA1 interaction through a direct Mre11–CDK2 interaction at the Mre11 C-terminus; this function does not require ATM activation or Mre11 nuclease activity.","method":"Co-immunoprecipitation, kinase assay, mutagenesis, mouse genetic model","journal":"Nature structural & molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP and kinase assays, single lab","pmids":["22231403"],"is_preprint":false},{"year":2013,"finding":"BRCA1 and its partner CtIP antagonize RIF1 accumulation at DSBs; depletion of CtIP or BRCA1 permits RIF1 to accumulate and suppress end resection in S/G2 phase; this circuit controls repair pathway choice.","method":"siRNA depletion, immunofluorescence, RPA/ssDNA assay, RAD51 loading assay","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple epistasis experiments in human cells, replicated across labs","pmids":["23333306"],"is_preprint":false},{"year":2014,"finding":"BRCA1–CtIP interaction (via phospho-S327) accelerates the speed of DNA-end resection but is not essential for resection per se; T847 phosphorylation is essential for resection; CtIP functions independently of BRCA1 for basic resection.","method":"High-resolution resection assay, mouse knock-in models (S327A, T847A), B-cell conditional KO","journal":"Cell reports / The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — separation-of-function mouse knock-in models with multiple functional readouts, consistent across two independent publications","pmids":["25310973","24842372"],"is_preprint":false},{"year":2000,"finding":"CtIP is a predominantly nuclear protein; its steady-state levels are low in G1 and increase sharply at the G1/S boundary via post-transcriptional regulation; a subset of CtIP exists in a complex with BRCA1 and BARD1.","method":"Subcellular fractionation, immunoprecipitation, cell cycle synchronization, Western blotting","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct fractionation and Co-IP, single lab, replicated for interaction by others","pmids":["10764811"],"is_preprint":false},{"year":2005,"finding":"Homozygous CtIP inactivation in mice causes embryonic lethality at E4.0 with G1 arrest; G1 arrest in CtIP-depleted NIH 3T3 cells is RB-dependent; CtIP counteracts Rb-mediated G1 restraint.","method":"Mouse gene targeting (knock-out), cell cycle analysis, Rb genetic epistasis (Rb-/- MEFs, Saos-2)","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — mouse KO with Rb epistasis, multiple cell types tested","pmids":["15831459"],"is_preprint":false},{"year":2006,"finding":"CtIP activates its own promoter and cyclin D1 promoter via the E2F/RB pathway during late G1/S; chromatin immunoprecipitation shows CtIP recruitment to its promoter coincides with TFIIB recruitment and Rb dissociation; CtIP-E157K (unable to bind Rb) fails to transactivate.","method":"ChIP, promoter reporter assays, site-directed mutagenesis (E157K), cell cycle synchronization","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and functional promoter assays, single lab","pmids":["16581787"],"is_preprint":false},{"year":1999,"finding":"CtIP interacts specifically with BRCA1 BRCT repeats both in vitro and in vivo; this interaction is abrogated by DNA-damaging agents (UV, γ-irradiation, adriamycin) correlating with BRCA1 phosphorylation; CtIP and CtBP diminish BRCA1-mediated p21 transactivation.","method":"Yeast two-hybrid, GST pull-down (in vitro), co-immunoprecipitation (in vivo), transcriptional reporter assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vitro and in vivo binding with functional transcription assay, replicated by multiple labs","pmids":["10196224"],"is_preprint":false},{"year":2004,"finding":"CtIP homodimerizes via an N-terminal coiled-coil domain (residues 45–160); this domain forms a compact helical structure; the N-terminal coiled-coil does not mediate binding to LMO4 or BRCA1.","method":"Co-immunoprecipitation in 293T cells, circular dichroism, analytical ultracentrifugation, MALDI-TOF","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — biophysical characterization of dimerization domain, single lab","pmids":["15084581"],"is_preprint":false},{"year":2012,"finding":"CtIP dimerization via a conserved N-terminal motif is required for its recruitment to DSBs; dimerization mutants fail to localize to DSBs (live-cell imaging), are strongly defective in HR and MMEJ, and show reduced damage-induced CtIP phosphorylation.","method":"Site-directed mutagenesis, live-cell GFP imaging, HR reporter assay, RPA foci, co-immunoprecipitation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — live-cell imaging combined with mutagenesis and functional assays; consistent with structural findings","pmids":["22544744"],"is_preprint":false},{"year":2010,"finding":"CtIP is essential for chromosomal translocation formation via alternative NHEJ (alt-NHEJ); CtIP depletion reduces microhomology usage at translocation junctions; CtIP-mediated resection generates ssDNA for microhomology-mediated end joining.","method":"Translocation reporter assay in mouse cells, CtIP siRNA depletion, junction sequencing","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct functional assay of translocation formation with molecular readout of microhomology usage, independently replicated","pmids":["21131978"],"is_preprint":false},{"year":2010,"finding":"CtIP is required for microhomology-directed alternative end-joining (A-NHEJ) during class-switch recombination; CtIP binds switch-region DNA in an AID-dependent manner; microhomology joins enriched upon Ku70 depletion also require CtIP.","method":"CtIP shRNA depletion in B cells, CSR switching assay, junction sequencing, ChIP","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — ChIP and functional CSR assay with mechanistic junction analysis, replicated by parallel study","pmids":["21131982"],"is_preprint":false},{"year":2011,"finding":"In G1-phase lymphocytes, H2AX and MDC1 prevent CtIP from processing RAG-generated hairpin-sealed coding ends; in the absence of H2AX, CtIP can open and resect these ends, leading to aberrant alt-NHEJ with microhomology usage and deletions. ATM activates both pro- and anti-resection pathways modulating CtIP activity.","method":"H2AX KO mouse cells, immunofluorescence, DNA repair assay, cell cycle gating","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo mouse model with multiple mechanistic readouts","pmids":["21160476"],"is_preprint":false},{"year":2009,"finding":"Fission yeast Ctp1 (CtIP ortholog) is required for the initial steps of HR in cooperation with the MRN complex; loss of Ctp1 phenocopies MRN deficiency in HR initiation.","method":"S. pombe genetic analysis (review/perspective citing Limbo et al.)","journal":"Molecular cell","confidence":"Low","confidence_rationale":"Tier 4 / Weak — perspective/mini-review paper without primary experimental data on human CtIP","pmids":["17996697"],"is_preprint":false},{"year":2011,"finding":"Two truncating mutations in CtIP (RBBP8) cause Seckel syndrome (SCKL2) and Jawad syndrome; SCKL2 cells exhibit defective DNA damage-induced ssDNA formation and reduced ATR activation; overexpression of the C-terminally truncated CtIP acts as a dominant-negative.","method":"Patient cell lines, ssDNA/BrdU assay, ATR signaling assays, mutant overexpression","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Moderate — patient-derived cells with direct functional assays for CtIP-specific activity","pmids":["21998596"],"is_preprint":false},{"year":2010,"finding":"CtIP interacts with EXO1 and restrains its exonucleolytic activity in vitro; EXO1 localization to DSBs depends on both CtIP and MRN.","method":"Co-immunoprecipitation, in vitro nuclease assay, immunofluorescence after CtIP/MRN depletion","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and in vitro nuclease assay; single lab","pmids":["21052091"],"is_preprint":false},{"year":2014,"finding":"CtIP exhibits an end resection-independent endonuclease activity required for repair of DSBs at common fragile sites (AT-rich sequences) and palindromic Alu inverted repeats; CtIP nuclease-defective mutants are impaired in handling DSBs with secondary DNA structures.","method":"CFS reporter assay, Alu-IR reporter, CtIP nuclease-dead mutants, co-immunoprecipitation","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — separation-of-function nuclease mutants with multiple reporter assays, single lab","pmids":["24837675"],"is_preprint":false},{"year":2014,"finding":"APC/C(Cdh1) ubiquitin ligase targets CtIP for degradation via a conserved KEN box on CtIP; mutation of the KEN box prevents Cdh1-dependent CtIP ubiquitylation and degradation in G1 and after DNA damage in G2, causing delayed CtIP clearance from foci, excessive resection, and reduced HR efficiency.","method":"Proteomics/MS, co-immunoprecipitation, ubiquitylation assay, KEN-box mutagenesis, DNA resection assay","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — proteomic identification, biochemical validation, mutagenesis, and functional readouts; single lab with multiple orthogonal methods","pmids":["25349192"],"is_preprint":false},{"year":2016,"finding":"KLHL15 (Cullin3 E3 ligase adaptor) interacts with CtIP via a conserved FRY tripeptide motif and promotes CtIP proteasomal degradation; FRY mutation blocks KLHL15-dependent CtIP ubiquitination and degradation, amplifying DNA-end resection and altering HR/NHEJ balance.","method":"Co-immunoprecipitation, ubiquitination assay, site-directed mutagenesis, DNA resection assay","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — biochemical ubiquitination assay with mutagenesis and functional resection readouts, single lab with multiple methods","pmids":["27561354"],"is_preprint":false},{"year":2010,"finding":"BRCA1 and CtIP cooperatively promote nuclease-mediated removal of oligonucleotides covalently bound at DSBs (from topoisomerase inhibitor treatment); BRCA1–CtIP interaction (via Ser332) is required for this activity but not for HR at clean DSBs.","method":"DT40 conditional CtIP KO, CtIP-S332A knock-in, sensitivity assays, RPA/Rad51 foci","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — separation-of-function DT40 knock-in with epistasis analysis","pmids":["20107609"],"is_preprint":false},{"year":2016,"finding":"MRN, CtIP, and BRCA1 are required for removal of Top2–DNA adducts and subsequent resection in Xenopus egg extracts; the CtIP–BRCA1 interaction (dispensable for resection of clean ends) is required for processing Top2-adducted DSBs.","method":"Xenopus egg extract biochemistry, immunodepletion, Top2 adduct removal assay","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — cell-free reconstitution in Xenopus extracts with specific depletions and resection assay","pmids":["26880199"],"is_preprint":false},{"year":2014,"finding":"Polo-like kinase 3 (Plk3) phosphorylates CtIP in G1 in a damage-inducible manner; Plk3 binds CtIP phosphorylated at S327 via its Polo box domains, promoting CtIP phosphorylation at S327 and T847; Plk3 and CtIP promote alt-NHEJ, translocation formation, and large-scale deletions in G1.","method":"Kinase assay, Plk3 depletion, S327 and T847 mutagenesis, translocation assay, DSB resection assay","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — kinase assay with mutagenesis and multiple cellular functional readouts, single lab","pmids":["25267294"],"is_preprint":false},{"year":2018,"finding":"PLK1 phosphorylates CtIP at Ser-723 after CDK1/Aurora A primes phosphorylation at S327 to recruit PLK1 via its polo-box domain; PLK1-phospho-mimetic CtIP supports MMEJ but not HR or G2/M checkpoint.","method":"Kinase assays, phospho-site mutagenesis, HR reporter, MMEJ assay, G2/M checkpoint analysis","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — kinase and mutagenesis data with functional pathway readouts, single lab","pmids":["30202980"],"is_preprint":false},{"year":2011,"finding":"In G0/G1, human CtIP and MRN are required for NHEJ repair of etoposide-induced (protein-blocked) DSBs; this NHEJ function requires CtIP Thr-847 but not Ser-327, and is mechanistically distinct from its HR resection function.","method":"G0/G1 arrest, CtIP/MRN siRNA depletion, DSB repair kinetics (53BP1 foci), phospho-site mutant complementation","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-cycle-specific depletion with phospho-mutant rescue, single lab","pmids":["21087997"],"is_preprint":false},{"year":2011,"finding":"Cdk1 phosphorylates CtIP to permit M-phase DSB resection via MRN–CtIP only; unlike S-phase resection, M-phase resection does not activate ATR or load Rad51, because Cdk1 prevents Rad51 binding to resected ends.","method":"Xenopus egg extract system (M-phase and S-phase), chromatin fractionation, RPA/Rad51 binding assays, CDK inhibitors","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — cell-free reconstitution with mechanistic dissection of resection and Rad51 loading, single lab","pmids":["21893598"],"is_preprint":false},{"year":2012,"finding":"CtIP-dependent DNA end resection is dispensable for initial ATR-CHK1 activation after DSBs, but is required for sustained ATR-CHK1 checkpoint signaling and maintenance of intra-S and G2 checkpoints.","method":"CtIP siRNA depletion, time-course CHK1 phosphorylation assay, resection assay, checkpoint assay","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — temporal dissection of checkpoint initiation vs. maintenance, single lab","pmids":["22733999"],"is_preprint":false},{"year":2014,"finding":"FANCD2 directly interacts with CtIP; monoubiquitinated FANCD2 tethers CtIP to damaged chromatin, channeling ICL-generated DSBs into HR; CtIP mutants defective in FANCD2 binding show increased NHEJ and ICL hypersensitivity.","method":"Co-immunoprecipitation, GST pull-down, chromatin fractionation, ICL sensitivity assay, FANCD2 monoubiquitination mutants","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent parallel studies (PMIDs 24794430 and 24794434) with Co-IP and functional data","pmids":["24794430","24794434"],"is_preprint":false},{"year":2019,"finding":"NBS1, via its FHA and BRCT domains, functions as a sensor of CtIP phosphorylation and activates MRE11-RAD50 nuclease through direct physical interactions with MRE11; two modes of CtIP-dependent MRE11 stimulation exist: phosphorylation-dependent (through NBS1) and phosphorylation-independent (without NBS1).","method":"Reconstituted in vitro nuclease assay with recombinant proteins, NBS1 domain mutants, mutagenesis","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — biochemical reconstitution with domain mutants, single lab with rigorous controls","pmids":["30787182"],"is_preprint":false},{"year":2020,"finding":"DNA-PK promotes DNA end processing by MRN–phospho-CtIP in physiological conditions; MRN-dependent endonucleolytic removal of DNA-PK-bound ends is observed at DSB sites; DNA-PK facilitates sequential transition from NHEJ to HR by promoting its own removal.","method":"Ensemble biochemistry, single-molecule assays, human cell chromatin assays","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with single-molecule validation and cellular corroboration","pmids":["31934630"],"is_preprint":false},{"year":2017,"finding":"CBX4 (SUMO E3 ligase) constitutively sumoylates CtIP at lysine 896; sumoylation is essential for CtIP recruitment to damaged DNA; non-sumoylatable CtIP-K896R blocks HR and increases genomic instability; SUMO fusion to CtIP rescues CBX4-depletion phenotype.","method":"In vivo SUMOylation assay, K896R mutagenesis, SUMO-CtIP fusion rescue, HR reporter, CtIP foci assay","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo sumoylation with site-specific mutagenesis and functional readouts including rescue experiment, single lab","pmids":["28740167"],"is_preprint":false},{"year":2021,"finding":"ATM-dependent hyperphosphorylation of CtIP at DSBs triggers PIAS4-dependent CtIP SUMOylation at K578; SUMO-modified CtIP is then polyubiquitinated by RNF4 and degraded; disrupting CtIP K578 sumoylation causes CtIP accumulation at DSBs, excessive resection, defective HR, and increased DSB sensitivity.","method":"SUMO/ubiquitin assays, K578R mutagenesis, ATM inhibition, CtIP foci quantification, HR reporter","journal":"Proceedings of the National Academy of Sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — sequential PTM pathway with mutagenesis and functional readouts, single lab","pmids":["33723063"],"is_preprint":false},{"year":2015,"finding":"RNF138 E3 ligase (with UBE2D E2 enzymes) promotes CtIP ubiquitylation and accrual at DNA damage sites at early resection stages, promoting HR.","method":"Systematic E2 screen, co-immunoprecipitation, ubiquitylation assay, laser microirradiation, HR reporter","journal":"Nature cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic screen followed by mechanistic validation with Co-IP and ubiquitylation assay, single lab","pmids":["26502057"],"is_preprint":false},{"year":2015,"finding":"USP4 deubiquitylase directly interacts with CtIP and MRN via specific domains; USP4 promotes CtIP recruitment to DSBs and HR; USP4 autodeubiquitylation is required for its HR function.","method":"Co-immunoprecipitation, deubiquitylation assay, CtIP foci analysis, HR reporter","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct interaction and deubiquitylation assays with functional HR readout, single lab","pmids":["26387952"],"is_preprint":false},{"year":2020,"finding":"USP52 directly interacts with and deubiquitinates CtIP; USP52-mediated deubiquitination facilitates CtIP phosphorylation at Thr-847 and its activation; ATM phosphorylates USP52 at Ser-1003 after DNA damage to enhance USP52 catalytic activity.","method":"Co-immunoprecipitation, in vitro deubiquitination assay, phosphorylation assay, DNA resection assay, HR reporter","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro deubiquitination with phosphorylation cascade validation and functional readouts, single lab","pmids":["33097710"],"is_preprint":false},{"year":2003,"finding":"SIAH-1 E3 ligase interacts with CtIP and promotes its degradation via the ubiquitin-proteasome pathway.","method":"Yeast two-hybrid, co-immunoprecipitation (in vitro and in vivo), proteasome inhibitor treatment, Western blotting","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro and in vivo interaction with proteasome-dependent degradation shown, single lab","pmids":["14654780"],"is_preprint":false},{"year":2018,"finding":"CtIP has an unanticipated role in protecting reversed stalled DNA replication forks from excessive degradation by DNA2 nuclease, independent of MRE11 and DSB resection; this function synergizes with BRCA1 to suppress replication-stress-induced genomic instability.","method":"DNA fiber assay (fork degradation), CtIP depletion, DNA2 inhibition, MRE11 inhibition, genetic epistasis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — DNA fiber assay with genetic epistasis to separate DSB resection from fork protection function, single lab with multiple approaches","pmids":["30344097"],"is_preprint":false},{"year":2020,"finding":"RBBP8/CtIP germline variants in early-onset breast cancer compromise replication fork stability by promoting helicase-driven destabilization of RAD51 nucleofilaments at stalled forks, distinct from the DSB end resection function.","method":"DNA fiber assay, RAD51 nucleofilament stability assay, patient variant functional analysis","journal":"The Journal of clinical investigation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional analysis of patient variants with fork protection assay, single study","pmids":["32379725"],"is_preprint":false},{"year":2020,"finding":"Phosphorylated CtIP bridges DNA molecules in a manner dependent on its oligomeric state; the bridging activity is separable from the nuclease-cofactor activity (distinct protein domains); bridging is much more efficient than yeast Sae2, consistent with expanded low-complexity regions in CtIP.","method":"Nanofluidic channel single-molecule DNA bridging assay, CtIP truncation mutants","journal":"Proceedings of the National Academy of Sciences","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — single-molecule biophysical assay with domain mutant analysis, single lab","pmids":["32417418"],"is_preprint":false},{"year":2020,"finding":"CtIP stimulates the ATP hydrolysis-driven motor activity of DNA2, promoting displacement of RPA-coated ssDNA and thus long-range resection; CtIP phosphorylation facilitates this stimulation; the domain of CtIP required to promote DNA2 is in the central region and is distinct from MRN-stimulatory domains.","method":"Reconstituted biochemical assay with purified human proteins, single-molecule DNA curtain assay, ATPase assay, domain mapping","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with purified components and single-molecule validation, mechanistic domain mapping","pmids":["32241893"],"is_preprint":false},{"year":2017,"finding":"CtIP interacts with BLM helicase and enhances BLM helicase activity; CtIP also enhances DNA cleavage by DNA2; thus CtIP promotes long-range resection via the BLM–DNA2 pathway in addition to MRE11 regulation.","method":"Co-immunoprecipitation, in vitro helicase assay, in vitro nuclease assay with purified proteins","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro biochemical reconstitution, single lab","pmids":["29020620"],"is_preprint":false},{"year":2018,"finding":"CtIP (Sae2 in yeast) depletion promotes accumulation of R-loops and stalled RNA polymerase at highly expressed genes; a catalytic CtIP mutant fails to complement R-loop sensitivity; overexpression of RNA-DNA helicase Senataxin suppresses DNA damage sensitivity in CtIP-deficient cells, suggesting CtIP nuclease activity processes R-loop intermediates.","method":"R-loop immunofluorescence, DRIP-seq, genetic complementation, Senataxin overexpression rescue","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic suppression and R-loop assays with catalytic mutant, but mechanism is partially inferred","pmids":["30523780"],"is_preprint":false},{"year":2005,"finding":"RBP-Jkappa/SHARP recruits CtIP and CtBP as corepressors; CtIP directly binds the SHARP repression domain; CtIP augments SHARP-mediated transcriptional repression of Notch target gene Hey1.","method":"Co-immunoprecipitation, GST pull-down, transcriptional reporter assay, CtBP-deficient cell lines","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding and functional transcription assay, single lab","pmids":["16287852"],"is_preprint":false},{"year":2001,"finding":"LMO4 interacts with CtIP (via a single LIM motif) and with BRCA1 BRCT domains independently; a stable LMO4–BRCA1–CtIP–Ldb1 complex exists in vivo; LMO4 represses BRCA1-mediated transcriptional activation.","method":"Yeast two-hybrid, co-immunoprecipitation, transcriptional reporter assay (yeast and mammalian)","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo complex demonstrated with functional repression assay, single lab","pmids":["11751867"],"is_preprint":false},{"year":2006,"finding":"BRCA1, CtIP, and ZBRK1 form a repressor complex that binds the ANG1 promoter via a ZBRK1 recognition site; disruption of this complex upregulates ANG1, stabilizes endothelial cells, and accelerates mammary tumor growth.","method":"ChIP, co-immunoprecipitation, RNAi depletion, reporter assay, 3D culture, mouse tumor model","journal":"Cancer cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — ChIP demonstrating promoter occupancy, functional rescue with multiple cellular assays and in vivo model","pmids":["16843262"],"is_preprint":false},{"year":2002,"finding":"CtIP interacts with Ikaros via CtIP's Rb interaction domain (not via CtBP); CtIP contributes to Ikaros-mediated transcriptional repression independent of HDACs; mutation abolishing Ikaros–CtIP interaction significantly reduces Ikaros repression activity.","method":"Co-immunoprecipitation, transcriptional reporter assay, HDAC inhibitor treatment, domain mutant analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with domain mutants and functional repression assay, single lab","pmids":["11959865"],"is_preprint":false},{"year":2015,"finding":"SERBP1 binds CtIP mRNA and regulates CtIP expression at the translational level in S phase; SERBP1 depletion reduces polysome-associated CtIP mRNA and CtIP protein; RNA-binding-deficient SERBP1 (ΔRGG) fails to rescue CtIP translation or HR.","method":"RIP-seq, polysome profiling, co-immunoprecipitation, RNA-binding mutant rescue","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RIP-seq and polysome profiling with domain mutant validation, single lab","pmids":["26068472"],"is_preprint":false},{"year":2022,"finding":"A micropeptide PACMP prevents CtIP ubiquitination by inhibiting the CtIP–KLHL15 interaction, thereby maintaining CtIP abundance and promoting HR; PACMP also binds DNA damage-induced poly(ADP-ribose) chains to enhance PARylation.","method":"Co-immunoprecipitation, ubiquitination assay, HR reporter, PARP inhibitor sensitivity assay","journal":"Molecular cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical Co-IP and functional HR assays, single lab","pmids":["35219381"],"is_preprint":false},{"year":2018,"finding":"Fusion of a minimal N-terminal CtIP fragment (HE domain, containing CDK phosphorylation sites and multimerization domain) to Cas9 stimulates HDR by approximately twofold; this HDR enhancement is CDK-phosphorylation and multimerization dependent.","method":"Cas9-CtIP fusion, HDR reporter assay, phospho-site and multimerization domain mutagenesis, human cell lines/iPSC/rat zygotes","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional domain dissection in multiple systems, single lab","pmids":["29556040"],"is_preprint":false}],"current_model":"CtIP (RBBP8) is a multifunctional nuclear protein that acts as a central regulator of DNA double-strand break repair pathway choice: it is recruited to DSBs specifically in S/G2 phase—controlled by CDK-mediated phosphorylation (primarily at Thr-847) and additional modifications (ATR-dependent phosphorylation, SUMOylation at K896 by CBX4, sequential SUMOylation/ubiquitination by PIAS4/RNF4, proteasomal turnover via APC/C-Cdh1 and Cullin3-KLHL15)—where it functions as a co-factor of the MRE11-RAD50-NBS1 (MRN) endonuclease to catalyze 5'-strand incision near protein-blocked DSB ends, and also promotes long-range resection by stimulating both the BLM-DNA2 and EXO1 pathways; it forms a tetrameric (dimer-of-dimers) architecture essential for DSB localization and activity, interacts in a phospho-Ser327-dependent manner with BRCA1 BRCT domains (structurally defined at 2.5 Å) to accelerate resection and remove protein adducts at complex ends, drives microhomology-mediated alternative NHEJ and chromosomal translocations, and additionally protects stalled replication forks from DNA2-mediated degradation; outside of DNA repair, CtIP functions as a transcriptional co-repressor in complexes with BRCA1, CtBP, Rb, ZBRK1, Ikaros, SHARP, and LMO4 to regulate G1/S transition and gene expression programs."},"narrative":{"mechanistic_narrative":"RBBP8 (CtIP) is a nuclear DNA double-strand break (DSB) repair factor that governs repair pathway choice by initiating and controlling end resection in S/G2 phase [PMID:17965729, PMID:19357644]. It is recruited to DSBs in a manner dependent on the MRN complex, ATM kinase activity, and a direct DNA-binding motif, where it promotes the transition from break sensing to resection [PMID:17965729, PMID:20064462]. Mechanistically, phosphorylated CtIP acts as a co-factor of the MRE11 endonuclease within MRN to catalyze 5'-strand incision near protein-blocked DSB ends, a function requiring CtIP phosphorylation at Thr-847 and NBS1, which senses CtIP phosphorylation through its FHA/BRCT domains to activate MRE11-RAD50 [PMID:27889449, PMID:30787182]; CtIP additionally possesses intrinsic endonuclease activity required for processing topoisomerase adducts, common fragile sites, and secondary-structure-containing ends [PMID:24837676, PMID:24837675]. Beyond short-range incision, CtIP drives long-range resection by stimulating both BLM helicase activity and the ATP-driven motor of DNA2 [PMID:32241893, PMID:29020620]. CtIP function is gated by cell-cycle and damage signaling: CDK phosphorylation at Thr-847 is essential for resection and induces interaction with NBS1, while phospho-Ser327 nucleates a structurally defined interaction with the BRCA1 BRCT domains that accelerates resection and is specifically required for removing protein adducts at complex ends [PMID:16101277, PMID:19202191, PMID:23468639, PMID:25310973, PMID:24842372, PMID:20107609, PMID:26880199]. CtIP assembles a homotetramer through a 'dimer-of-dimers' architecture and dimerizes via an N-terminal coiled-coil, an oligomeric state essential for DSB localization, resection, and DNA bridging [PMID:25558984, PMID:15084581, PMID:22544744, PMID:32417418]. The BRCA1-CtIP axis directs S/G2 cells toward error-free homologous recombination by antagonizing RIF1, whereas CtIP-driven resection also generates microhomology for alternative NHEJ, mediating chromosomal translocations and class-switch recombination [PMID:19357644, PMID:23333306, PMID:21131978, PMID:21131982]. CtIP abundance and chromatin retention are tightly controlled by an elaborate post-translational network including APC/C(Cdh1)- and Cullin3-KLHL15-mediated degradation, opposing deubiquitinases USP4 and USP52, and SUMOylation by CBX4 and PIAS4 coupled to RNF4-dependent turnover [PMID:25349192, PMID:27561354, PMID:28740167, PMID:33723063, PMID:26387952, PMID:33097710]. Independently of DSB resection, CtIP protects reversed stalled replication forks from DNA2-mediated degradation in cooperation with BRCA1 [PMID:30344097, PMID:32379725]. Outside DNA repair, CtIP functions as a transcriptional co-repressor in complexes with BRCA1, CtBP, Rb, ZBRK1, Ikaros, SHARP, and LMO4, and counteracts Rb-mediated G1 restraint to promote the G1/S transition [PMID:15831459, PMID:16581787, PMID:10196224, PMID:16287852, PMID:11751867, PMID:16843262, PMID:11959865]. Truncating mutations in RBBP8 cause Seckel syndrome (SCKL2) and Jawad syndrome, with patient cells showing defective damage-induced ssDNA formation and reduced ATR activation [PMID:21998596].","teleology":[{"year":1998,"claim":"Established CtIP as a physical partner of the BRCA1 BRCT domains, linking it to BRCA1 tumor suppressor function before its repair role was known.","evidence":"Yeast two-hybrid and in vivo interaction assay with tumor-associated BRCT mutants","pmids":["9738006"],"confidence":"High","gaps":["Functional consequence of the interaction not defined","Phosphorylation-dependence not yet established"]},{"year":2000,"claim":"Defined CtIP as a cell-cycle-regulated nuclear protein whose levels rise at G1/S and that exists in a BRCA1-BARD1 complex, placing it at the proliferation/repair interface.","evidence":"Subcellular fractionation, Co-IP, and cell-cycle synchronization","pmids":["10764811"],"confidence":"Medium","gaps":["Mechanism of post-transcriptional regulation unresolved","Single lab"]},{"year":2002,"claim":"Showed CtIP acts as a transcriptional co-repressor beyond BRCA1, contributing to Ikaros-mediated repression via its Rb interaction domain independent of HDACs.","evidence":"Co-IP, reporter assays, HDAC inhibitor treatment, domain mutants","pmids":["11959865"],"confidence":"Medium","gaps":["Target gene programs not mapped","Relationship to repair role unclear"]},{"year":2005,"claim":"Defined the phospho-Ser327-dependent CtIP-BRCA1 BRCT interaction at atomic resolution and linked CtIP to the G2/M checkpoint, providing the structural basis for the interaction and explaining cancer-associated BRCA1 mutations.","evidence":"X-ray crystallography (2.5 Å), ITC, mutant analysis, Co-IP, and cell-cycle/checkpoint assays","pmids":["16101277","15485915"],"confidence":"High","gaps":["Functional output of the interaction in resection not yet dissected","Kinase responsible for S327 not identified"]},{"year":2005,"claim":"Demonstrated CtIP is essential for embryonic viability and counteracts Rb-mediated G1 restraint, establishing a non-repair role in cell-cycle control.","evidence":"Mouse gene knockout and Rb genetic epistasis in MEFs/Saos-2","pmids":["15831459"],"confidence":"High","gaps":["Molecular mechanism of Rb antagonism partly inferred","Does not separate repair from proliferative functions"]},{"year":2007,"claim":"Identified CtIP as the human factor required for S/G2-restricted DSB resection acting with the MRN complex, establishing its central role in repair pathway choice.","evidence":"siRNA depletion, laser micro-irradiation, Co-IP, and cell-cycle fractionation","pmids":["17965729"],"confidence":"High","gaps":["Direct enzymatic contribution to resection not yet defined","Recruitment mechanism not fully mapped"]},{"year":2009,"claim":"Resolved how cell-cycle and damage signaling gate CtIP, showing CDK phosphorylation at Thr-847 enables resection/HR while phospho-S327/BRCA1 acts as a switch between G1 end-joining and S/G2 HR.","evidence":"Site-directed mutagenesis, CDK inhibition, DT40 gene targeting, RPA foci and repair pathway assays","pmids":["19202191","19357644"],"confidence":"High","gaps":["Direct biochemical activity of phospho-CtIP not yet reconstituted","Full kinase circuitry incomplete"]},{"year":2010,"claim":"Established CtIP as a driver of microhomology-mediated alternative end-joining, including chromosomal translocations and class-switch recombination.","evidence":"Translocation and CSR reporter assays with siRNA/shRNA depletion and junction sequencing","pmids":["21131978","21131982"],"confidence":"High","gaps":["Distinction between resection-dependent and -independent contributions to alt-NHEJ not fully resolved"]},{"year":2014,"claim":"Revealed CtIP carries intrinsic, MRN-independent endonuclease activity dedicated to processing protein adducts and structured DNA ends.","evidence":"Recombinant protein purification, in vitro endonuclease assays, separation-of-function nuclease mutants, cell-based assays","pmids":["24837676","24837675"],"confidence":"High","gaps":["Relationship between intrinsic and MRN-cofactor nuclease activities debated","Substrate specificity in vivo incompletely mapped"]},{"year":2015,"claim":"Defined the homotetrameric 'dimer-of-dimers' architecture of CtIP as essential for DSB localization and resection.","evidence":"X-ray crystallography, SEC-MALS/AUC, mutagenesis, and HR reporter assays","pmids":["25558984"],"confidence":"High","gaps":["How oligomeric state mechanistically couples to nuclease stimulation not fully resolved"]},{"year":2016,"claim":"Reconstituted phospho-CtIP as a direct co-factor of the MRE11 endonuclease within MRN that incises 5'-terminated strands, providing the biochemical basis for resection initiation.","evidence":"Reconstituted in vitro nuclease assays with purified human proteins and phospho-site mutagenesis","pmids":["27889449"],"confidence":"High","gaps":["Structural mechanism of MRE11 activation not resolved here","Role of NBS1 sensing addressed later"]},{"year":2017,"claim":"Extended CtIP function to long-range resection by showing it interacts with and stimulates BLM helicase and enhances DNA2 cleavage.","evidence":"Co-IP and in vitro helicase/nuclease assays with purified proteins","pmids":["29020620"],"confidence":"Medium","gaps":["Single lab","Domain requirements detailed in later DNA2 work"]},{"year":2018,"claim":"Identified a resection-independent role for CtIP in protecting reversed stalled replication forks from DNA2-mediated degradation in cooperation with BRCA1.","evidence":"DNA fiber assays with CtIP depletion, DNA2/MRE11 inhibition, and genetic epistasis","pmids":["30344097"],"confidence":"High","gaps":["Molecular mechanism of fork protection partly defined","Separation from RAD51 nucleofilament stabilization role clarified later"]},{"year":2019,"claim":"Clarified that NBS1 senses CtIP phosphorylation via FHA/BRCT domains to activate MRE11-RAD50, distinguishing phosphorylation-dependent and -independent modes of MRE11 stimulation.","evidence":"Reconstituted in vitro nuclease assays with NBS1 domain mutants","pmids":["30787182"],"confidence":"High","gaps":["Structural detail of the NBS1-CtIP-MRE11 activated state not resolved"]},{"year":2020,"claim":"Mapped distinct CtIP domains for DNA bridging, DNA2 motor stimulation, and showed DNA-PK promotes the MRN-phospho-CtIP transition from NHEJ to HR.","evidence":"Single-molecule nanofluidic bridging, reconstituted DNA2 ATPase/curtain assays, single-molecule and cellular DNA-PK processing assays","pmids":["32417418","32241893","31934630"],"confidence":"High","gaps":["In vivo coordination of bridging, nuclease, and motor-stimulatory activities not fully integrated"]},{"year":2021,"claim":"Detailed the layered PTM network controlling CtIP abundance and chromatin retention, including KLHL15/Cullin3 and APC/C(Cdh1) degradation, CBX4 and PIAS4-RNF4 SUMO-coupled turnover, and opposing deubiquitinases USP4/USP52.","evidence":"Co-IP, ubiquitination/SUMOylation/deubiquitination assays, site-specific mutagenesis, and resection/HR readouts across multiple studies","pmids":["25349192","27561354","28740167","33723063","26387952","33097710"],"confidence":"Medium","gaps":["Hierarchy and crosstalk among PTM events incompletely ordered","Several findings from single labs"]},{"year":2011,"claim":"Linked RBBP8 to human disease, establishing truncating mutations as causative of Seckel and Jawad syndromes through defective ssDNA formation and ATR activation.","evidence":"Patient-derived cell lines with ssDNA/BrdU and ATR signaling assays and dominant-negative mutant overexpression","pmids":["21998596"],"confidence":"High","gaps":["Genotype-phenotype relationships for the two syndromes not fully resolved"]},{"year":null,"claim":"How CtIP's multiple separable activities — short-range nuclease cofactor, long-range resection stimulation, DNA bridging, fork protection, and transcriptional co-repression — are coordinated within a single regulatory architecture in vivo remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified structural model integrating oligomerization, nuclease, and bridging domains","Spatiotemporal switching among functions not defined","Quantitative contribution of transcriptional roles to physiology unclear"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140097","term_label":"catalytic activity, acting on DNA","supporting_discovery_ids":[9,10,30,41]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[7,51]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[9,52,53,41]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[19,20,21,55,57,58]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[51,40]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[18,0]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[4,0,7]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[0,6,9,24]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[19,38,39]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[20,21,57]},{"term_id":"R-HSA-69306","term_label":"DNA Replication","supporting_discovery_ids":[49,50]}],"complexes":["MRN (MRE11-RAD50-NBS1) complex (as phospho-CtIP cofactor)","BRCA1-CtIP-MRN complex","BRCA1-CtIP-ZBRK1 repressor complex","LMO4-BRCA1-CtIP-Ldb1 complex"],"partners":["BRCA1","NBS1","MRE11","DNA2","BLM","EXO1","FANCD2","KLHL15"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q99708","full_name":"DNA endonuclease RBBP8","aliases":["CtBP-interacting protein","CtIP","Retinoblastoma-binding protein 8","RBBP-8","Retinoblastoma-interacting protein and myosin-like","RIM","Sporulation in the absence of SPO11 protein 2 homolog","SAE2"],"length_aa":897,"mass_kda":101.9,"function":"Endonuclease that cooperates with the MRE11-RAD50-NBN (MRN) complex in DNA-end resection, the first step of double-strand break (DSB) repair through the homologous recombination (HR) pathway (PubMed:17965729, PubMed:19202191, PubMed:19759395, PubMed:20064462, PubMed:23273981, PubMed:26721387, PubMed:27814491, PubMed:27889449, PubMed:30787182, PubMed:31802118). HR is restricted to S and G2 phases of the cell cycle and preferentially repairs DSBs resulting from replication fork collapse (PubMed:17965729, PubMed:19202191, PubMed:23273981, PubMed:27814491, PubMed:27889449, PubMed:30787182). Key determinant of DSB repair pathway choice, as it commits cells to HR by preventing classical non-homologous end-joining (NHEJ) (PubMed:19202191). Specifically promotes the endonuclease activity of the MRN complex to clear DNA ends containing protein adducts: recruited to DSBs by NBN following phosphorylation by CDK1, and promotes the endonuclease activity of MRE11 to clear protein-DNA adducts and generate clean double-strand break ends (PubMed:27814491, PubMed:27889449, PubMed:30787182, PubMed:33836577). Functions downstream of the MRN complex and ATM, promotes ATR activation and its recruitment to DSBs in the S/G2 phase facilitating the generation of ssDNA (PubMed:16581787, PubMed:17965729, PubMed:19759395, PubMed:20064462). Component of the BRCA1-RBBP8 complex that regulates CHEK1 activation and controls cell cycle G2/M checkpoints on DNA damage (PubMed:15485915, PubMed:16818604). During immunoglobulin heavy chain class-switch recombination, promotes microhomology-mediated alternative end joining (A-NHEJ) and plays an essential role in chromosomal translocations (By similarity). Binds preferentially to DNA Y-junctions and to DNA substrates with blocked ends and promotes intermolecular DNA bridging (PubMed:30601117)","subcellular_location":"Nucleus; Chromosome","url":"https://www.uniprot.org/uniprotkb/Q99708/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/RBBP8","classification":"Common Essential","n_dependent_lines":1155,"n_total_lines":1208,"dependency_fraction":0.9561258278145696},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"HSPA4","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/RBBP8","total_profiled":1310},"omim":[{"mim_id":"620397","title":"AURORA KINASE A- AND NINEIN-INTERACTING PROTEIN; AUNIP","url":"https://www.omim.org/entry/620397"},{"mim_id":"618650","title":"RING FINGER PROTEIN 169; RNF169","url":"https://www.omim.org/entry/618650"},{"mim_id":"617884","title":"HEPATOMA-DERIVED GROWTH FACTOR-LIKE PROTEIN 2; HDGFL2","url":"https://www.omim.org/entry/617884"},{"mim_id":"616940","title":"EXONUCLEASE 3-PRIME-TO-5-PRIME DOMAIN-CONTAINING PROTEIN 2; EXD2","url":"https://www.omim.org/entry/616940"},{"mim_id":"613273","title":"INST3- AND NABP-INTERACTING PROTEIN; INIP","url":"https://www.omim.org/entry/613273"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RBBP8"},"hgnc":{"alias_symbol":["CtIP","RIM","COM1"],"prev_symbol":["SCKL2"]},"alphafold":{"accession":"Q99708","domains":[{"cath_id":"-","chopping":"804-836","consensus_level":"medium","plddt":80.7345,"start":804,"end":836}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q99708","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q99708-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q99708-F1-predicted_aligned_error_v6.png","plddt_mean":53.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RBBP8","jax_strain_url":"https://www.jax.org/strain/search?query=RBBP8"},"sequence":{"accession":"Q99708","fasta_url":"https://rest.uniprot.org/uniprotkb/Q99708.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q99708/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q99708"}},"corpus_meta":[{"pmid":"17965729","id":"PMC_17965729","title":"Human CtIP promotes DNA end resection.","date":"2007","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/17965729","citation_count":1088,"is_preprint":false},{"pmid":"23333306","id":"PMC_23333306","title":"A cell cycle-dependent regulatory circuit composed of 53BP1-RIF1 and BRCA1-CtIP controls DNA repair pathway choice.","date":"2013","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/23333306","citation_count":742,"is_preprint":false},{"pmid":"19357644","id":"PMC_19357644","title":"CtIP-BRCA1 modulates the choice of DNA double-strand-break repair pathway throughout the cell cycle.","date":"2009","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/19357644","citation_count":427,"is_preprint":false},{"pmid":"19202191","id":"PMC_19202191","title":"Human CtIP mediates cell cycle control of DNA end resection and double strand break repair.","date":"2009","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19202191","citation_count":414,"is_preprint":false},{"pmid":"15485915","id":"PMC_15485915","title":"DNA damage-induced cell cycle checkpoint control requires CtIP, a phosphorylation-dependent binding partner of BRCA1 C-terminal domains.","date":"2004","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/15485915","citation_count":341,"is_preprint":false},{"pmid":"18171670","id":"PMC_18171670","title":"Cell cycle-dependent complex formation of BRCA1.CtIP.MRN is important for DNA double-strand break repair.","date":"2008","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/18171670","citation_count":340,"is_preprint":false},{"pmid":"9738006","id":"PMC_9738006","title":"The C-terminal (BRCT) domains of BRCA1 interact in vivo with CtIP, a protein implicated in the CtBP pathway of transcriptional repression.","date":"1998","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9738006","citation_count":340,"is_preprint":false},{"pmid":"20829486","id":"PMC_20829486","title":"RETRACTED: Human SIRT6 promotes DNA end resection through CtIP deacetylation.","date":"2010","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/20829486","citation_count":289,"is_preprint":false},{"pmid":"27889449","id":"PMC_27889449","title":"Phosphorylated CtIP Functions as a Co-factor of the MRE11-RAD50-NBS1 Endonuclease in DNA End Resection.","date":"2016","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/27889449","citation_count":259,"is_preprint":false},{"pmid":"16818604","id":"PMC_16818604","title":"BRCA1 ubiquitinates its phosphorylation-dependent binding partner CtIP.","date":"2006","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/16818604","citation_count":225,"is_preprint":false},{"pmid":"23468639","id":"PMC_23468639","title":"The interaction of CtIP and Nbs1 connects CDK and ATM to regulate HR-mediated double-strand break repair.","date":"2013","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23468639","citation_count":220,"is_preprint":false},{"pmid":"25310973","id":"PMC_25310973","title":"BRCA1 accelerates CtIP-mediated DNA-end resection.","date":"2014","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/25310973","citation_count":214,"is_preprint":false},{"pmid":"21131978","id":"PMC_21131978","title":"An essential role for CtIP in chromosomal translocation formation through an alternative end-joining pathway.","date":"2010","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/21131978","citation_count":209,"is_preprint":false},{"pmid":"20064462","id":"PMC_20064462","title":"CtIP links DNA double-strand break sensing to resection.","date":"2009","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/20064462","citation_count":194,"is_preprint":false},{"pmid":"29556040","id":"PMC_29556040","title":"CtIP fusion to Cas9 enhances transgene integration by homology-dependent repair.","date":"2018","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/29556040","citation_count":166,"is_preprint":false},{"pmid":"10196224","id":"PMC_10196224","title":"Binding of CtIP to the BRCT repeats of BRCA1 involved in the transcription regulation of p21 is disrupted upon DNA damage.","date":"1999","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10196224","citation_count":166,"is_preprint":false},{"pmid":"19150433","id":"PMC_19150433","title":"Distinct requirements for the Rad32(Mre11) nuclease and Ctp1(CtIP) in the removal of covalently bound topoisomerase I and II from DNA.","date":"2009","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/19150433","citation_count":161,"is_preprint":false},{"pmid":"24837676","id":"PMC_24837676","title":"Catalytic and noncatalytic roles of the CtIP endonuclease in double-strand break end resection.","date":"2014","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/24837676","citation_count":154,"is_preprint":false},{"pmid":"16287852","id":"PMC_16287852","title":"RBP-Jkappa/SHARP recruits CtIP/CtBP corepressors to silence Notch target genes.","date":"2005","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/16287852","citation_count":151,"is_preprint":false},{"pmid":"21131982","id":"PMC_21131982","title":"CtIP promotes microhomology-mediated alternative end joining during class-switch recombination.","date":"2010","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/21131982","citation_count":146,"is_preprint":false},{"pmid":"20444606","id":"PMC_20444606","title":"DNA damage and decisions: CtIP coordinates DNA repair and cell cycle checkpoints.","date":"2010","source":"Trends in cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/20444606","citation_count":133,"is_preprint":false},{"pmid":"10764811","id":"PMC_10764811","title":"Nuclear localization and cell cycle-specific expression of CtIP, a protein that associates with the BRCA1 tumor suppressor.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10764811","citation_count":132,"is_preprint":false},{"pmid":"11751867","id":"PMC_11751867","title":"The LIM domain protein LMO4 interacts with the cofactor CtIP and the tumor suppressor BRCA1 and inhibits BRCA1 activity.","date":"2001","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11751867","citation_count":129,"is_preprint":false},{"pmid":"20107609","id":"PMC_20107609","title":"Collaborative action of Brca1 and CtIP in elimination of covalent modifications from double-strand breaks to facilitate subsequent break repair.","date":"2010","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/20107609","citation_count":125,"is_preprint":false},{"pmid":"21160476","id":"PMC_21160476","title":"H2AX prevents CtIP-mediated DNA end resection and aberrant repair in G1-phase lymphocytes.","date":"2010","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/21160476","citation_count":120,"is_preprint":false},{"pmid":"15831459","id":"PMC_15831459","title":"Inactivation of CtIP leads to early embryonic lethality mediated by G1 restraint and to tumorigenesis by haploid insufficiency.","date":"2005","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/15831459","citation_count":120,"is_preprint":false},{"pmid":"24837675","id":"PMC_24837675","title":"CtIP maintains stability at common fragile sites and inverted repeats by end resection-independent endonuclease activity.","date":"2014","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/24837675","citation_count":119,"is_preprint":false},{"pmid":"23273981","id":"PMC_23273981","title":"Activation of DSB processing requires phosphorylation of CtIP by ATR.","date":"2012","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/23273981","citation_count":118,"is_preprint":false},{"pmid":"21908405","id":"PMC_21908405","title":"NF-κB regulates DNA double-strand break repair in conjunction with BRCA1-CtIP complexes.","date":"2011","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/21908405","citation_count":117,"is_preprint":false},{"pmid":"31934630","id":"PMC_31934630","title":"DNA-dependent protein kinase promotes DNA end processing by MRN and CtIP.","date":"2020","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/31934630","citation_count":115,"is_preprint":false},{"pmid":"17996697","id":"PMC_17996697","title":"Ctp1/CtIP and the MRN complex collaborate in the initial steps of homologous recombination.","date":"2007","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/17996697","citation_count":111,"is_preprint":false},{"pmid":"21052091","id":"PMC_21052091","title":"DNA end resection by CtIP and exonuclease 1 prevents genomic instability.","date":"2010","source":"EMBO reports","url":"https://pubmed.ncbi.nlm.nih.gov/21052091","citation_count":108,"is_preprint":false},{"pmid":"26880199","id":"PMC_26880199","title":"MRN, CtIP, and BRCA1 mediate repair of topoisomerase II-DNA adducts.","date":"2016","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/26880199","citation_count":108,"is_preprint":false},{"pmid":"30344097","id":"PMC_30344097","title":"CtIP-Mediated Fork Protection Synergizes with BRCA1 to Suppress Genomic Instability upon DNA Replication Stress.","date":"2018","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/30344097","citation_count":104,"is_preprint":false},{"pmid":"21998596","id":"PMC_21998596","title":"CtIP Mutations Cause Seckel and Jawad Syndromes.","date":"2011","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/21998596","citation_count":103,"is_preprint":false},{"pmid":"24842372","id":"PMC_24842372","title":"CtIP-mediated resection is essential for viability and can operate independently of BRCA1.","date":"2014","source":"The Journal of experimental medicine","url":"https://pubmed.ncbi.nlm.nih.gov/24842372","citation_count":103,"is_preprint":false},{"pmid":"21087997","id":"PMC_21087997","title":"CtIP and MRN promote non-homologous end-joining of etoposide-induced DNA double-strand breaks in G1.","date":"2010","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/21087997","citation_count":102,"is_preprint":false},{"pmid":"22231403","id":"PMC_22231403","title":"Mre11 regulates CtIP-dependent double-strand break repair by interaction with CDK2.","date":"2012","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/22231403","citation_count":101,"is_preprint":false},{"pmid":"26502057","id":"PMC_26502057","title":"Systematic E2 screening reveals a UBE2D-RNF138-CtIP axis promoting DNA repair.","date":"2015","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/26502057","citation_count":97,"is_preprint":false},{"pmid":"23770684","id":"PMC_23770684","title":"HDAC turnover, CtIP acetylation and dysregulated DNA damage signaling in colon cancer cells treated with sulforaphane and related dietary isothiocyanates.","date":"2013","source":"Epigenetics","url":"https://pubmed.ncbi.nlm.nih.gov/23770684","citation_count":96,"is_preprint":false},{"pmid":"16101277","id":"PMC_16101277","title":"Structural basis for cell cycle checkpoint control by the BRCA1-CtIP complex.","date":"2005","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16101277","citation_count":91,"is_preprint":false},{"pmid":"18007598","id":"PMC_18007598","title":"A novel plant gene essential for meiosis is related to the human CtIP and the yeast COM1/SAE2 gene.","date":"2007","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/18007598","citation_count":88,"is_preprint":false},{"pmid":"16843262","id":"PMC_16843262","title":"Removal of BRCA1/CtIP/ZBRK1 repressor complex on ANG1 promoter leads to accelerated mammary tumor growth contributed by prominent vasculature.","date":"2006","source":"Cancer cell","url":"https://pubmed.ncbi.nlm.nih.gov/16843262","citation_count":87,"is_preprint":false},{"pmid":"25267294","id":"PMC_25267294","title":"Polo-like kinase 3 regulates CtIP during DNA double-strand break repair in G1.","date":"2014","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/25267294","citation_count":84,"is_preprint":false},{"pmid":"25957490","id":"PMC_25957490","title":"CtIP: A DNA damage response protein at the intersection of DNA metabolism.","date":"2015","source":"DNA repair","url":"https://pubmed.ncbi.nlm.nih.gov/25957490","citation_count":83,"is_preprint":false},{"pmid":"24794430","id":"PMC_24794430","title":"FANCD2 binds CtIP and regulates DNA-end resection during DNA interstrand crosslink repair.","date":"2014","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/24794430","citation_count":77,"is_preprint":false},{"pmid":"35219381","id":"PMC_35219381","title":"Micropeptide PACMP inhibition elicits synthetic lethal effects by decreasing CtIP and poly(ADP-ribosyl)ation.","date":"2022","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/35219381","citation_count":77,"is_preprint":false},{"pmid":"36400008","id":"PMC_36400008","title":"POLθ prevents MRE11-NBS1-CtIP-dependent fork breakage in the absence of BRCA2/RAD51 by filling lagging-strand gaps.","date":"2022","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/36400008","citation_count":76,"is_preprint":false},{"pmid":"24794434","id":"PMC_24794434","title":"FANCD2 and CtIP cooperate to repair DNA interstrand crosslinks.","date":"2014","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/24794434","citation_count":76,"is_preprint":false},{"pmid":"23712259","id":"PMC_23712259","title":"The interaction between CtIP and BRCA1 is not essential for resection-mediated DNA repair or tumor suppression.","date":"2013","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/23712259","citation_count":72,"is_preprint":false},{"pmid":"24556218","id":"PMC_24556218","title":"CtIP mediates replication fork recovery in a FANCD2-regulated manner.","date":"2014","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/24556218","citation_count":70,"is_preprint":false},{"pmid":"25349192","id":"PMC_25349192","title":"APC/C(Cdh1) controls CtIP stability during the cell cycle and in response to DNA damage.","date":"2014","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/25349192","citation_count":70,"is_preprint":false},{"pmid":"21893598","id":"PMC_21893598","title":"Cdk1 uncouples CtIP-dependent resection and Rad51 filament formation during M-phase double-strand break repair.","date":"2011","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/21893598","citation_count":70,"is_preprint":false},{"pmid":"30787182","id":"PMC_30787182","title":"NBS1 promotes the endonuclease activity of the MRE11-RAD50 complex by sensing CtIP phosphorylation.","date":"2019","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/30787182","citation_count":69,"is_preprint":false},{"pmid":"23994874","id":"PMC_23994874","title":"BRCA1 and CtIP suppress long-tract gene conversion between sister chromatids.","date":"2013","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/23994874","citation_count":67,"is_preprint":false},{"pmid":"18007596","id":"PMC_18007596","title":"A conserved function for a Caenorhabditis elegans Com1/Sae2/CtIP protein homolog in meiotic recombination.","date":"2007","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/18007596","citation_count":67,"is_preprint":false},{"pmid":"32241893","id":"PMC_32241893","title":"CtIP promotes the motor activity of DNA2 to accelerate long-range DNA end resection.","date":"2020","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/32241893","citation_count":65,"is_preprint":false},{"pmid":"25558984","id":"PMC_25558984","title":"CtIP tetramer assembly is required for DNA-end resection and repair.","date":"2015","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/25558984","citation_count":64,"is_preprint":false},{"pmid":"24095737","id":"PMC_24095737","title":"A role for BLM in double-strand break repair pathway choice: prevention of CtIP/Mre11-mediated alternative nonhomologous end-joining.","date":"2013","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/24095737","citation_count":64,"is_preprint":false},{"pmid":"22544744","id":"PMC_22544744","title":"CtIP protein dimerization is critical for its recruitment to chromosomal DNA double-stranded breaks.","date":"2012","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22544744","citation_count":63,"is_preprint":false},{"pmid":"22733999","id":"PMC_22733999","title":"CtIP-dependent DNA resection is required for DNA damage checkpoint maintenance but not initiation.","date":"2012","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/22733999","citation_count":62,"is_preprint":false},{"pmid":"29020620","id":"PMC_29020620","title":"Enhancement of BLM-DNA2-Mediated Long-Range DNA End Resection by CtIP.","date":"2017","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/29020620","citation_count":62,"is_preprint":false},{"pmid":"30523780","id":"PMC_30523780","title":"Sae2/CtIP prevents R-loop accumulation in eukaryotic cells.","date":"2018","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/30523780","citation_count":61,"is_preprint":false},{"pmid":"19759395","id":"PMC_19759395","title":"N terminus of CtIP is critical for homologous recombination-mediated double-strand break repair.","date":"2009","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19759395","citation_count":61,"is_preprint":false},{"pmid":"11959865","id":"PMC_11959865","title":"Ikaros-CtIP interactions do not require C-terminal binding protein and participate in a deacetylase-independent mode of repression.","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11959865","citation_count":60,"is_preprint":false},{"pmid":"23349304","id":"PMC_23349304","title":"Microsatellite instability induced mutations in DNA repair genes CtIP and MRE11 confer hypersensitivity to poly (ADP-ribose) polymerase inhibitors in myeloid malignancies.","date":"2013","source":"Haematologica","url":"https://pubmed.ncbi.nlm.nih.gov/23349304","citation_count":58,"is_preprint":false},{"pmid":"27561354","id":"PMC_27561354","title":"Cullin3-KLHL15 ubiquitin ligase mediates CtIP protein turnover to fine-tune DNA-end resection.","date":"2016","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/27561354","citation_count":55,"is_preprint":false},{"pmid":"26387952","id":"PMC_26387952","title":"The Deubiquitylating Enzyme USP4 Cooperates with CtIP in DNA Double-Strand Break End Resection.","date":"2015","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/26387952","citation_count":53,"is_preprint":false},{"pmid":"16581787","id":"PMC_16581787","title":"CtIP activates its own and cyclin D1 promoters via the E2F/RB pathway during G1/S progression.","date":"2006","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/16581787","citation_count":51,"is_preprint":false},{"pmid":"17112672","id":"PMC_17112672","title":"TRB3 interacts with CtIP and is overexpressed in certain cancers.","date":"2006","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/17112672","citation_count":49,"is_preprint":false},{"pmid":"25567988","id":"PMC_25567988","title":"Neddylation inhibits CtIP-mediated resection and regulates DNA double strand break repair pathway choice.","date":"2015","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/25567988","citation_count":48,"is_preprint":false},{"pmid":"23696749","id":"PMC_23696749","title":"ATM-dependent MiR-335 targets CtIP and modulates the DNA damage response.","date":"2013","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23696749","citation_count":45,"is_preprint":false},{"pmid":"30202980","id":"PMC_30202980","title":"PLK1 targets CtIP to promote microhomology-mediated end joining.","date":"2018","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/30202980","citation_count":45,"is_preprint":false},{"pmid":"28623092","id":"PMC_28623092","title":"CtIP/Ctp1/Sae2, molecular form fit for function.","date":"2017","source":"DNA repair","url":"https://pubmed.ncbi.nlm.nih.gov/28623092","citation_count":44,"is_preprint":false},{"pmid":"28740167","id":"PMC_28740167","title":"DNA end resection requires constitutive sumoylation of CtIP by CBX4.","date":"2017","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/28740167","citation_count":43,"is_preprint":false},{"pmid":"15084581","id":"PMC_15084581","title":"Dimerization of CtIP, a BRCA1- and CtBP-interacting protein, is mediated by an N-terminal coiled-coil motif.","date":"2004","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15084581","citation_count":43,"is_preprint":false},{"pmid":"26525166","id":"PMC_26525166","title":"Relative contribution of four nucleases, CtIP, Dna2, Exo1 and Mre11, to the initial step of DNA double-strand break repair by homologous recombination in both the chicken DT40 and human TK6 cell lines.","date":"2015","source":"Genes to cells : devoted to molecular & cellular mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/26525166","citation_count":43,"is_preprint":false},{"pmid":"29445424","id":"PMC_29445424","title":"Promoter methylation of DNA damage repair (DDR) genes in human tumor entities: RBBP8/CtIP is almost exclusively methylated in bladder cancer.","date":"2018","source":"Clinical epigenetics","url":"https://pubmed.ncbi.nlm.nih.gov/29445424","citation_count":42,"is_preprint":false},{"pmid":"20007691","id":"PMC_20007691","title":"Derepression of HMGA2 via removal of ZBRK1/BRCA1/CtIP complex enhances mammary tumorigenesis.","date":"2009","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20007691","citation_count":42,"is_preprint":false},{"pmid":"32950401","id":"PMC_32950401","title":"Human CtIP: A 'double agent' in DNA repair and tumorigenesis.","date":"2020","source":"Seminars in cell & developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/32950401","citation_count":39,"is_preprint":false},{"pmid":"29061988","id":"PMC_29061988","title":"Aquarius is required for proper CtIP expression and homologous recombination repair.","date":"2017","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/29061988","citation_count":39,"is_preprint":false},{"pmid":"14654780","id":"PMC_14654780","title":"SIAH-1 interacts with CtIP and promotes its degradation by the proteasome pathway.","date":"2003","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/14654780","citation_count":37,"is_preprint":false},{"pmid":"24413181","id":"PMC_24413181","title":"Triapine disrupts CtIP-mediated homologous recombination repair and sensitizes ovarian cancer cells to PARP and topoisomerase inhibitors.","date":"2014","source":"Molecular cancer research : MCR","url":"https://pubmed.ncbi.nlm.nih.gov/24413181","citation_count":37,"is_preprint":false},{"pmid":"16249056","id":"PMC_16249056","title":"CtIP, a candidate tumor susceptibility gene is a team player with luminaries.","date":"2005","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/16249056","citation_count":36,"is_preprint":false},{"pmid":"26068472","id":"PMC_26068472","title":"SERBP1 affects homologous recombination-mediated DNA repair by regulation of CtIP translation during S phase.","date":"2015","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/26068472","citation_count":36,"is_preprint":false},{"pmid":"26713604","id":"PMC_26713604","title":"Loss of CtIP disturbs homologous recombination repair and sensitizes breast cancer cells to PARP inhibitors.","date":"2016","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/26713604","citation_count":33,"is_preprint":false},{"pmid":"33723063","id":"PMC_33723063","title":"ATM controls the extent of DNA end resection by eliciting sequential posttranslational modifications of CtIP.","date":"2021","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/33723063","citation_count":31,"is_preprint":false},{"pmid":"33097710","id":"PMC_33097710","title":"USP52 regulates DNA end resection and chemosensitivity through removing inhibitory ubiquitination from CtIP.","date":"2020","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/33097710","citation_count":30,"is_preprint":false},{"pmid":"31501894","id":"PMC_31501894","title":"CSB interacts with BRCA1 in late S/G2 to promote MRN- and CtIP-mediated DNA end resection.","date":"2019","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/31501894","citation_count":30,"is_preprint":false},{"pmid":"33044911","id":"PMC_33044911","title":"The SWI/SNF ATPase BRG1 stimulates DNA end resection and homologous recombination by reducing nucleosome density at DNA double strand breaks and by promoting the recruitment of the CtIP nuclease.","date":"2020","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/33044911","citation_count":30,"is_preprint":false},{"pmid":"25582120","id":"PMC_25582120","title":"BRCA1 and CtIP promote alternative non-homologous end-joining at uncapped telomeres.","date":"2015","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/25582120","citation_count":29,"is_preprint":false},{"pmid":"25909997","id":"PMC_25909997","title":"BRCA1 and CtIP Are Both Required to Recruit Dna2 at Double-Strand Breaks in Homologous Recombination.","date":"2015","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25909997","citation_count":29,"is_preprint":false},{"pmid":"32379725","id":"PMC_32379725","title":"Germline RBBP8 variants associated with early-onset breast cancer compromise replication fork stability.","date":"2020","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/32379725","citation_count":28,"is_preprint":false},{"pmid":"27940552","id":"PMC_27940552","title":"And-1 coordinates with CtIP for efficient homologous recombination and DNA damage checkpoint maintenance.","date":"2017","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/27940552","citation_count":28,"is_preprint":false},{"pmid":"23144634","id":"PMC_23144634","title":"CtIP is required to initiate replication-dependent interstrand crosslink repair.","date":"2012","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23144634","citation_count":28,"is_preprint":false},{"pmid":"32251466","id":"PMC_32251466","title":"FANCJ helicase promotes DNA end resection by facilitating CtIP recruitment to DNA double-strand breaks.","date":"2020","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32251466","citation_count":27,"is_preprint":false},{"pmid":"27798638","id":"PMC_27798638","title":"53BP1 Protects against CtIP-Dependent Capture of Ectopic Chromosomal Sequences at the Junction of Distant Double-Strand Breaks.","date":"2016","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27798638","citation_count":27,"is_preprint":false},{"pmid":"18171986","id":"PMC_18171986","title":"CtIP silencing as a novel mechanism of tamoxifen resistance in breast cancer.","date":"2007","source":"Molecular cancer research : MCR","url":"https://pubmed.ncbi.nlm.nih.gov/18171986","citation_count":26,"is_preprint":false},{"pmid":"27494840","id":"PMC_27494840","title":"Impaired 53BP1/RIF1 DSB mediated end-protection stimulates CtIP-dependent end resection and switches the repair to PARP1-dependent end joining in G1.","date":"2016","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/27494840","citation_count":25,"is_preprint":false},{"pmid":"32817418","id":"PMC_32817418","title":"Phosphorylated CtIP bridges DNA to promote annealing of broken ends.","date":"2020","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/32817418","citation_count":24,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":44642,"output_tokens":13250,"usd":0.166338,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":24961,"output_tokens":5579,"usd":0.13214,"stage2_stop_reason":"end_turn"},"total_usd":0.298478,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"Human CtIP (RBBP8) is required for DNA double-strand break (DSB) resection in S and G2 phases, is recruited to DSBs exclusively in S/G2, physically and functionally interacts with the MRE11 complex, and is required for RPA and ATR recruitment and ATR activation following DSBs. CtIP shares sequence homology with yeast Sae2.\",\n      \"method\": \"siRNA depletion, laser micro-irradiation, co-immunoprecipitation, immunofluorescence, cell-cycle fractionation\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Co-IP, functional depletion, localization), widely replicated across the field\",\n      \"pmids\": [\"17965729\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"The BRCT domains of BRCA1 interact in vivo with CtIP; tumor-associated mutations in the BRCT motifs ablate this interaction.\",\n      \"method\": \"Sos recruitment yeast two-hybrid system, in vivo interaction assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — replicated by multiple subsequent studies using reciprocal Co-IP and structural methods\",\n      \"pmids\": [\"9738006\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"CtIP interacts with BRCA1 BRCT domains in a phosphorylation-dependent manner (phospho-Ser327); the CtIP/BRCA1 complex exists specifically in G2 phase and is required for DNA damage-induced Chk1 phosphorylation and the G2/M checkpoint.\",\n      \"method\": \"Co-immunoprecipitation, cell cycle synchronization, phosphorylation assays, siRNA depletion\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, phosphorylation-dependence shown, cell-cycle specificity established, replicated by multiple labs\",\n      \"pmids\": [\"15485915\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Crystal structure of BRCA1 BRCT repeats bound to CtIP phosphopeptide (residues 322–333, phospho-Ser327) at 2.5 Å resolution; Phe330 and phospho-Ser327 anchor the peptide; the cancer-associated BRCA1 M1775R mutation sterically clashes with CtIP Phe330, disrupting the interaction.\",\n      \"method\": \"X-ray crystallography, isothermal titration calorimetry\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional validation (ITC affinity measurement, mutant analysis)\",\n      \"pmids\": [\"16101277\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"BRCA1 RING domain catalyzes CtIP ubiquitination in a manner dependent on phosphorylation-mediated CtIP–BRCA1 BRCT interaction; this ubiquitination does not target CtIP for proteasomal degradation but instead promotes chromatin association of CtIP after DNA damage and participation in G2/M checkpoint control.\",\n      \"method\": \"In vitro ubiquitination assay, co-immunoprecipitation, chromatin fractionation, cell cycle checkpoint assays\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro ubiquitination reconstitution plus cellular functional assays, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"16818604\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CDK-mediated phosphorylation of CtIP at Thr-847 is required for DSB resection and homologous recombination; phospho-mimetic T847E allows resection even after CDK inhibition, while T847A impairs resection. Mutating Ser-327 specifically abolishes BRCA1 interaction and HR but not MMEJ.\",\n      \"method\": \"Site-directed mutagenesis, CDK inhibitor treatment, RPA focus formation assay, chromosomal rearrangement assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis of specific phosphorylation sites with functional readouts; independently replicated\",\n      \"pmids\": [\"19202191\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CtIP-S327 phosphorylation and BRCA1 recruitment acts as a molecular switch directing DSB repair from error-prone end-joining (MMEJ) in G1 to error-free HR in S/G2; CtIP-S327A cells are specifically defective in HR but not MMEJ.\",\n      \"method\": \"DT40 gene targeting, site-directed mutagenesis, single-stranded DNA assays, repair pathway assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis in DT40 cells with separation-of-function mutants, replicated by multiple labs\",\n      \"pmids\": [\"19357644\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CtIP translocation to DSBs depends on the MRN complex, ATM kinase activity, and a direct DNA-binding motif in CtIP; CtIP promotes the transition from DSB sensing to resection downstream of ATM activation.\",\n      \"method\": \"Xenopus egg extracts, laser-induced DSBs in human cells, ATM inhibition, direct DNA-binding assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — combination of cell-free reconstitution (Xenopus) and human cell assays with domain mapping\",\n      \"pmids\": [\"20064462\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"BRCA1 forms a cell cycle-dependent complex with CtIP and MRN; complex formation (especially IR-enhanced BRCA1–MRN association) requires CDK activity; CtIP directly interacts with Nbs1; the complex is critical for ssDNA formation and HR.\",\n      \"method\": \"Co-immunoprecipitation, CDK inhibition, IR treatment, ssDNA/BrdU assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP with CDK dependency and functional ssDNA readout; independently replicated\",\n      \"pmids\": [\"18171670\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Phosphorylated CtIP acts as a co-factor of MRE11 endonuclease within the MRN complex; this function absolutely requires CtIP phosphorylation at Thr-847 and NBS1; the MRN–phospho-CtIP complex preferentially cleaves 5'-terminated DNA strands near DSBs to initiate resection.\",\n      \"method\": \"Reconstituted in vitro nuclease assay with recombinant human proteins, phosphorylation-site mutagenesis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — biochemical reconstitution with purified components and mutagenesis; independently replicated\",\n      \"pmids\": [\"27889449\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Human CtIP has intrinsic 5' flap endonuclease activity on branched DNA, independent of MRN; phosphorylation at damage-dependent sites (not S327/T847) is essential for catalytic activity; catalytic mutant CtIP is deficient in processing topoisomerase adducts and radiation-induced breaks but not endonuclease-generated breaks.\",\n      \"method\": \"Recombinant protein purification, in vitro endonuclease assay, phosphorylation-site mutagenesis, cell-based repair assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution of endonuclease activity with mutagenesis and cellular validation, single lab with multiple orthogonal approaches\",\n      \"pmids\": [\"24837676\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"X-ray crystallography and biophysical analyses show that the N-terminal domain of human CtIP forms a stable homotetramer via a 'dimer-of-dimers' architecture; a point mutation abolishing tetramerization (but preserving dimerization) causes strong defects in DNA-end resection and gene conversion in cells.\",\n      \"method\": \"X-ray crystallography, biophysical (SEC-MALS, AUC), site-directed mutagenesis, HR reporter assays\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional mutagenesis validation in cells\",\n      \"pmids\": [\"25558984\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"SIRT6 deacetylates CtIP to promote DNA end resection; a non-acetylatable CtIP mutant alleviates the resection defect caused by SIRT6 depletion. NOTE: this paper was subsequently retracted.\",\n      \"method\": \"Co-immunoprecipitation, site-directed mutagenesis, RPA/ssDNA focus assays (RETRACTED paper)\",\n      \"journal\": \"Science\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — paper was formally retracted; findings should not be considered established\",\n      \"pmids\": [\"20829486\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"ATR phosphorylates CtIP at T818 (Xenopus; T859 in human) in response to DSBs; non-phosphorylatable CtIP (T818A) fails to bind chromatin or initiate resection; ATM activity is required for an early resection step leading to ATR activation and CtIP-T818 phosphorylation.\",\n      \"method\": \"Xenopus egg extract system, mass spectrometry, chromatin binding assay, phospho-specific antibodies, mutagenesis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cell-free reconstitution in Xenopus with MS identification of phosphorylation site and mutagenesis validation\",\n      \"pmids\": [\"23273981\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CDK phosphorylation of CtIP induces its interaction with the FHA and BRCT domains of Nbs1; CDK-dependent CtIP–Nbs1 interaction is a prerequisite for ATM to phosphorylate CtIP upon DNA damage, promoting BLM and Exo1 recruitment and HR.\",\n      \"method\": \"Phosphopeptide pull-down, co-immunoprecipitation, phosphorylation assays, siRNA depletion, HR reporter\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple Co-IPs and functional assays establishing the CDK-ATM-CtIP-Nbs1 axis, single lab\",\n      \"pmids\": [\"23468639\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Mre11 controls CDK2-dependent CtIP phosphorylation and BRCA1 interaction through a direct Mre11–CDK2 interaction at the Mre11 C-terminus; this function does not require ATM activation or Mre11 nuclease activity.\",\n      \"method\": \"Co-immunoprecipitation, kinase assay, mutagenesis, mouse genetic model\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP and kinase assays, single lab\",\n      \"pmids\": [\"22231403\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"BRCA1 and its partner CtIP antagonize RIF1 accumulation at DSBs; depletion of CtIP or BRCA1 permits RIF1 to accumulate and suppress end resection in S/G2 phase; this circuit controls repair pathway choice.\",\n      \"method\": \"siRNA depletion, immunofluorescence, RPA/ssDNA assay, RAD51 loading assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple epistasis experiments in human cells, replicated across labs\",\n      \"pmids\": [\"23333306\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"BRCA1–CtIP interaction (via phospho-S327) accelerates the speed of DNA-end resection but is not essential for resection per se; T847 phosphorylation is essential for resection; CtIP functions independently of BRCA1 for basic resection.\",\n      \"method\": \"High-resolution resection assay, mouse knock-in models (S327A, T847A), B-cell conditional KO\",\n      \"journal\": \"Cell reports / The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — separation-of-function mouse knock-in models with multiple functional readouts, consistent across two independent publications\",\n      \"pmids\": [\"25310973\", \"24842372\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"CtIP is a predominantly nuclear protein; its steady-state levels are low in G1 and increase sharply at the G1/S boundary via post-transcriptional regulation; a subset of CtIP exists in a complex with BRCA1 and BARD1.\",\n      \"method\": \"Subcellular fractionation, immunoprecipitation, cell cycle synchronization, Western blotting\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct fractionation and Co-IP, single lab, replicated for interaction by others\",\n      \"pmids\": [\"10764811\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Homozygous CtIP inactivation in mice causes embryonic lethality at E4.0 with G1 arrest; G1 arrest in CtIP-depleted NIH 3T3 cells is RB-dependent; CtIP counteracts Rb-mediated G1 restraint.\",\n      \"method\": \"Mouse gene targeting (knock-out), cell cycle analysis, Rb genetic epistasis (Rb-/- MEFs, Saos-2)\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mouse KO with Rb epistasis, multiple cell types tested\",\n      \"pmids\": [\"15831459\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"CtIP activates its own promoter and cyclin D1 promoter via the E2F/RB pathway during late G1/S; chromatin immunoprecipitation shows CtIP recruitment to its promoter coincides with TFIIB recruitment and Rb dissociation; CtIP-E157K (unable to bind Rb) fails to transactivate.\",\n      \"method\": \"ChIP, promoter reporter assays, site-directed mutagenesis (E157K), cell cycle synchronization\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and functional promoter assays, single lab\",\n      \"pmids\": [\"16581787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"CtIP interacts specifically with BRCA1 BRCT repeats both in vitro and in vivo; this interaction is abrogated by DNA-damaging agents (UV, γ-irradiation, adriamycin) correlating with BRCA1 phosphorylation; CtIP and CtBP diminish BRCA1-mediated p21 transactivation.\",\n      \"method\": \"Yeast two-hybrid, GST pull-down (in vitro), co-immunoprecipitation (in vivo), transcriptional reporter assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vitro and in vivo binding with functional transcription assay, replicated by multiple labs\",\n      \"pmids\": [\"10196224\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"CtIP homodimerizes via an N-terminal coiled-coil domain (residues 45–160); this domain forms a compact helical structure; the N-terminal coiled-coil does not mediate binding to LMO4 or BRCA1.\",\n      \"method\": \"Co-immunoprecipitation in 293T cells, circular dichroism, analytical ultracentrifugation, MALDI-TOF\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — biophysical characterization of dimerization domain, single lab\",\n      \"pmids\": [\"15084581\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CtIP dimerization via a conserved N-terminal motif is required for its recruitment to DSBs; dimerization mutants fail to localize to DSBs (live-cell imaging), are strongly defective in HR and MMEJ, and show reduced damage-induced CtIP phosphorylation.\",\n      \"method\": \"Site-directed mutagenesis, live-cell GFP imaging, HR reporter assay, RPA foci, co-immunoprecipitation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — live-cell imaging combined with mutagenesis and functional assays; consistent with structural findings\",\n      \"pmids\": [\"22544744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CtIP is essential for chromosomal translocation formation via alternative NHEJ (alt-NHEJ); CtIP depletion reduces microhomology usage at translocation junctions; CtIP-mediated resection generates ssDNA for microhomology-mediated end joining.\",\n      \"method\": \"Translocation reporter assay in mouse cells, CtIP siRNA depletion, junction sequencing\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct functional assay of translocation formation with molecular readout of microhomology usage, independently replicated\",\n      \"pmids\": [\"21131978\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CtIP is required for microhomology-directed alternative end-joining (A-NHEJ) during class-switch recombination; CtIP binds switch-region DNA in an AID-dependent manner; microhomology joins enriched upon Ku70 depletion also require CtIP.\",\n      \"method\": \"CtIP shRNA depletion in B cells, CSR switching assay, junction sequencing, ChIP\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — ChIP and functional CSR assay with mechanistic junction analysis, replicated by parallel study\",\n      \"pmids\": [\"21131982\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In G1-phase lymphocytes, H2AX and MDC1 prevent CtIP from processing RAG-generated hairpin-sealed coding ends; in the absence of H2AX, CtIP can open and resect these ends, leading to aberrant alt-NHEJ with microhomology usage and deletions. ATM activates both pro- and anti-resection pathways modulating CtIP activity.\",\n      \"method\": \"H2AX KO mouse cells, immunofluorescence, DNA repair assay, cell cycle gating\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo mouse model with multiple mechanistic readouts\",\n      \"pmids\": [\"21160476\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Fission yeast Ctp1 (CtIP ortholog) is required for the initial steps of HR in cooperation with the MRN complex; loss of Ctp1 phenocopies MRN deficiency in HR initiation.\",\n      \"method\": \"S. pombe genetic analysis (review/perspective citing Limbo et al.)\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — perspective/mini-review paper without primary experimental data on human CtIP\",\n      \"pmids\": [\"17996697\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Two truncating mutations in CtIP (RBBP8) cause Seckel syndrome (SCKL2) and Jawad syndrome; SCKL2 cells exhibit defective DNA damage-induced ssDNA formation and reduced ATR activation; overexpression of the C-terminally truncated CtIP acts as a dominant-negative.\",\n      \"method\": \"Patient cell lines, ssDNA/BrdU assay, ATR signaling assays, mutant overexpression\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — patient-derived cells with direct functional assays for CtIP-specific activity\",\n      \"pmids\": [\"21998596\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CtIP interacts with EXO1 and restrains its exonucleolytic activity in vitro; EXO1 localization to DSBs depends on both CtIP and MRN.\",\n      \"method\": \"Co-immunoprecipitation, in vitro nuclease assay, immunofluorescence after CtIP/MRN depletion\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and in vitro nuclease assay; single lab\",\n      \"pmids\": [\"21052091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CtIP exhibits an end resection-independent endonuclease activity required for repair of DSBs at common fragile sites (AT-rich sequences) and palindromic Alu inverted repeats; CtIP nuclease-defective mutants are impaired in handling DSBs with secondary DNA structures.\",\n      \"method\": \"CFS reporter assay, Alu-IR reporter, CtIP nuclease-dead mutants, co-immunoprecipitation\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — separation-of-function nuclease mutants with multiple reporter assays, single lab\",\n      \"pmids\": [\"24837675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"APC/C(Cdh1) ubiquitin ligase targets CtIP for degradation via a conserved KEN box on CtIP; mutation of the KEN box prevents Cdh1-dependent CtIP ubiquitylation and degradation in G1 and after DNA damage in G2, causing delayed CtIP clearance from foci, excessive resection, and reduced HR efficiency.\",\n      \"method\": \"Proteomics/MS, co-immunoprecipitation, ubiquitylation assay, KEN-box mutagenesis, DNA resection assay\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — proteomic identification, biochemical validation, mutagenesis, and functional readouts; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"25349192\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"KLHL15 (Cullin3 E3 ligase adaptor) interacts with CtIP via a conserved FRY tripeptide motif and promotes CtIP proteasomal degradation; FRY mutation blocks KLHL15-dependent CtIP ubiquitination and degradation, amplifying DNA-end resection and altering HR/NHEJ balance.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, site-directed mutagenesis, DNA resection assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical ubiquitination assay with mutagenesis and functional resection readouts, single lab with multiple methods\",\n      \"pmids\": [\"27561354\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"BRCA1 and CtIP cooperatively promote nuclease-mediated removal of oligonucleotides covalently bound at DSBs (from topoisomerase inhibitor treatment); BRCA1–CtIP interaction (via Ser332) is required for this activity but not for HR at clean DSBs.\",\n      \"method\": \"DT40 conditional CtIP KO, CtIP-S332A knock-in, sensitivity assays, RPA/Rad51 foci\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — separation-of-function DT40 knock-in with epistasis analysis\",\n      \"pmids\": [\"20107609\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"MRN, CtIP, and BRCA1 are required for removal of Top2–DNA adducts and subsequent resection in Xenopus egg extracts; the CtIP–BRCA1 interaction (dispensable for resection of clean ends) is required for processing Top2-adducted DSBs.\",\n      \"method\": \"Xenopus egg extract biochemistry, immunodepletion, Top2 adduct removal assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cell-free reconstitution in Xenopus extracts with specific depletions and resection assay\",\n      \"pmids\": [\"26880199\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Polo-like kinase 3 (Plk3) phosphorylates CtIP in G1 in a damage-inducible manner; Plk3 binds CtIP phosphorylated at S327 via its Polo box domains, promoting CtIP phosphorylation at S327 and T847; Plk3 and CtIP promote alt-NHEJ, translocation formation, and large-scale deletions in G1.\",\n      \"method\": \"Kinase assay, Plk3 depletion, S327 and T847 mutagenesis, translocation assay, DSB resection assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — kinase assay with mutagenesis and multiple cellular functional readouts, single lab\",\n      \"pmids\": [\"25267294\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PLK1 phosphorylates CtIP at Ser-723 after CDK1/Aurora A primes phosphorylation at S327 to recruit PLK1 via its polo-box domain; PLK1-phospho-mimetic CtIP supports MMEJ but not HR or G2/M checkpoint.\",\n      \"method\": \"Kinase assays, phospho-site mutagenesis, HR reporter, MMEJ assay, G2/M checkpoint analysis\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — kinase and mutagenesis data with functional pathway readouts, single lab\",\n      \"pmids\": [\"30202980\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In G0/G1, human CtIP and MRN are required for NHEJ repair of etoposide-induced (protein-blocked) DSBs; this NHEJ function requires CtIP Thr-847 but not Ser-327, and is mechanistically distinct from its HR resection function.\",\n      \"method\": \"G0/G1 arrest, CtIP/MRN siRNA depletion, DSB repair kinetics (53BP1 foci), phospho-site mutant complementation\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-cycle-specific depletion with phospho-mutant rescue, single lab\",\n      \"pmids\": [\"21087997\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Cdk1 phosphorylates CtIP to permit M-phase DSB resection via MRN–CtIP only; unlike S-phase resection, M-phase resection does not activate ATR or load Rad51, because Cdk1 prevents Rad51 binding to resected ends.\",\n      \"method\": \"Xenopus egg extract system (M-phase and S-phase), chromatin fractionation, RPA/Rad51 binding assays, CDK inhibitors\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cell-free reconstitution with mechanistic dissection of resection and Rad51 loading, single lab\",\n      \"pmids\": [\"21893598\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CtIP-dependent DNA end resection is dispensable for initial ATR-CHK1 activation after DSBs, but is required for sustained ATR-CHK1 checkpoint signaling and maintenance of intra-S and G2 checkpoints.\",\n      \"method\": \"CtIP siRNA depletion, time-course CHK1 phosphorylation assay, resection assay, checkpoint assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — temporal dissection of checkpoint initiation vs. maintenance, single lab\",\n      \"pmids\": [\"22733999\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"FANCD2 directly interacts with CtIP; monoubiquitinated FANCD2 tethers CtIP to damaged chromatin, channeling ICL-generated DSBs into HR; CtIP mutants defective in FANCD2 binding show increased NHEJ and ICL hypersensitivity.\",\n      \"method\": \"Co-immunoprecipitation, GST pull-down, chromatin fractionation, ICL sensitivity assay, FANCD2 monoubiquitination mutants\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent parallel studies (PMIDs 24794430 and 24794434) with Co-IP and functional data\",\n      \"pmids\": [\"24794430\", \"24794434\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"NBS1, via its FHA and BRCT domains, functions as a sensor of CtIP phosphorylation and activates MRE11-RAD50 nuclease through direct physical interactions with MRE11; two modes of CtIP-dependent MRE11 stimulation exist: phosphorylation-dependent (through NBS1) and phosphorylation-independent (without NBS1).\",\n      \"method\": \"Reconstituted in vitro nuclease assay with recombinant proteins, NBS1 domain mutants, mutagenesis\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — biochemical reconstitution with domain mutants, single lab with rigorous controls\",\n      \"pmids\": [\"30787182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"DNA-PK promotes DNA end processing by MRN–phospho-CtIP in physiological conditions; MRN-dependent endonucleolytic removal of DNA-PK-bound ends is observed at DSB sites; DNA-PK facilitates sequential transition from NHEJ to HR by promoting its own removal.\",\n      \"method\": \"Ensemble biochemistry, single-molecule assays, human cell chromatin assays\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with single-molecule validation and cellular corroboration\",\n      \"pmids\": [\"31934630\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"CBX4 (SUMO E3 ligase) constitutively sumoylates CtIP at lysine 896; sumoylation is essential for CtIP recruitment to damaged DNA; non-sumoylatable CtIP-K896R blocks HR and increases genomic instability; SUMO fusion to CtIP rescues CBX4-depletion phenotype.\",\n      \"method\": \"In vivo SUMOylation assay, K896R mutagenesis, SUMO-CtIP fusion rescue, HR reporter, CtIP foci assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo sumoylation with site-specific mutagenesis and functional readouts including rescue experiment, single lab\",\n      \"pmids\": [\"28740167\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ATM-dependent hyperphosphorylation of CtIP at DSBs triggers PIAS4-dependent CtIP SUMOylation at K578; SUMO-modified CtIP is then polyubiquitinated by RNF4 and degraded; disrupting CtIP K578 sumoylation causes CtIP accumulation at DSBs, excessive resection, defective HR, and increased DSB sensitivity.\",\n      \"method\": \"SUMO/ubiquitin assays, K578R mutagenesis, ATM inhibition, CtIP foci quantification, HR reporter\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — sequential PTM pathway with mutagenesis and functional readouts, single lab\",\n      \"pmids\": [\"33723063\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"RNF138 E3 ligase (with UBE2D E2 enzymes) promotes CtIP ubiquitylation and accrual at DNA damage sites at early resection stages, promoting HR.\",\n      \"method\": \"Systematic E2 screen, co-immunoprecipitation, ubiquitylation assay, laser microirradiation, HR reporter\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic screen followed by mechanistic validation with Co-IP and ubiquitylation assay, single lab\",\n      \"pmids\": [\"26502057\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"USP4 deubiquitylase directly interacts with CtIP and MRN via specific domains; USP4 promotes CtIP recruitment to DSBs and HR; USP4 autodeubiquitylation is required for its HR function.\",\n      \"method\": \"Co-immunoprecipitation, deubiquitylation assay, CtIP foci analysis, HR reporter\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct interaction and deubiquitylation assays with functional HR readout, single lab\",\n      \"pmids\": [\"26387952\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"USP52 directly interacts with and deubiquitinates CtIP; USP52-mediated deubiquitination facilitates CtIP phosphorylation at Thr-847 and its activation; ATM phosphorylates USP52 at Ser-1003 after DNA damage to enhance USP52 catalytic activity.\",\n      \"method\": \"Co-immunoprecipitation, in vitro deubiquitination assay, phosphorylation assay, DNA resection assay, HR reporter\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro deubiquitination with phosphorylation cascade validation and functional readouts, single lab\",\n      \"pmids\": [\"33097710\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"SIAH-1 E3 ligase interacts with CtIP and promotes its degradation via the ubiquitin-proteasome pathway.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation (in vitro and in vivo), proteasome inhibitor treatment, Western blotting\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro and in vivo interaction with proteasome-dependent degradation shown, single lab\",\n      \"pmids\": [\"14654780\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CtIP has an unanticipated role in protecting reversed stalled DNA replication forks from excessive degradation by DNA2 nuclease, independent of MRE11 and DSB resection; this function synergizes with BRCA1 to suppress replication-stress-induced genomic instability.\",\n      \"method\": \"DNA fiber assay (fork degradation), CtIP depletion, DNA2 inhibition, MRE11 inhibition, genetic epistasis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — DNA fiber assay with genetic epistasis to separate DSB resection from fork protection function, single lab with multiple approaches\",\n      \"pmids\": [\"30344097\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"RBBP8/CtIP germline variants in early-onset breast cancer compromise replication fork stability by promoting helicase-driven destabilization of RAD51 nucleofilaments at stalled forks, distinct from the DSB end resection function.\",\n      \"method\": \"DNA fiber assay, RAD51 nucleofilament stability assay, patient variant functional analysis\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional analysis of patient variants with fork protection assay, single study\",\n      \"pmids\": [\"32379725\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Phosphorylated CtIP bridges DNA molecules in a manner dependent on its oligomeric state; the bridging activity is separable from the nuclease-cofactor activity (distinct protein domains); bridging is much more efficient than yeast Sae2, consistent with expanded low-complexity regions in CtIP.\",\n      \"method\": \"Nanofluidic channel single-molecule DNA bridging assay, CtIP truncation mutants\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — single-molecule biophysical assay with domain mutant analysis, single lab\",\n      \"pmids\": [\"32417418\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"CtIP stimulates the ATP hydrolysis-driven motor activity of DNA2, promoting displacement of RPA-coated ssDNA and thus long-range resection; CtIP phosphorylation facilitates this stimulation; the domain of CtIP required to promote DNA2 is in the central region and is distinct from MRN-stimulatory domains.\",\n      \"method\": \"Reconstituted biochemical assay with purified human proteins, single-molecule DNA curtain assay, ATPase assay, domain mapping\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with purified components and single-molecule validation, mechanistic domain mapping\",\n      \"pmids\": [\"32241893\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"CtIP interacts with BLM helicase and enhances BLM helicase activity; CtIP also enhances DNA cleavage by DNA2; thus CtIP promotes long-range resection via the BLM–DNA2 pathway in addition to MRE11 regulation.\",\n      \"method\": \"Co-immunoprecipitation, in vitro helicase assay, in vitro nuclease assay with purified proteins\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro biochemical reconstitution, single lab\",\n      \"pmids\": [\"29020620\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CtIP (Sae2 in yeast) depletion promotes accumulation of R-loops and stalled RNA polymerase at highly expressed genes; a catalytic CtIP mutant fails to complement R-loop sensitivity; overexpression of RNA-DNA helicase Senataxin suppresses DNA damage sensitivity in CtIP-deficient cells, suggesting CtIP nuclease activity processes R-loop intermediates.\",\n      \"method\": \"R-loop immunofluorescence, DRIP-seq, genetic complementation, Senataxin overexpression rescue\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic suppression and R-loop assays with catalytic mutant, but mechanism is partially inferred\",\n      \"pmids\": [\"30523780\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"RBP-Jkappa/SHARP recruits CtIP and CtBP as corepressors; CtIP directly binds the SHARP repression domain; CtIP augments SHARP-mediated transcriptional repression of Notch target gene Hey1.\",\n      \"method\": \"Co-immunoprecipitation, GST pull-down, transcriptional reporter assay, CtBP-deficient cell lines\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding and functional transcription assay, single lab\",\n      \"pmids\": [\"16287852\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"LMO4 interacts with CtIP (via a single LIM motif) and with BRCA1 BRCT domains independently; a stable LMO4–BRCA1–CtIP–Ldb1 complex exists in vivo; LMO4 represses BRCA1-mediated transcriptional activation.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, transcriptional reporter assay (yeast and mammalian)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo complex demonstrated with functional repression assay, single lab\",\n      \"pmids\": [\"11751867\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"BRCA1, CtIP, and ZBRK1 form a repressor complex that binds the ANG1 promoter via a ZBRK1 recognition site; disruption of this complex upregulates ANG1, stabilizes endothelial cells, and accelerates mammary tumor growth.\",\n      \"method\": \"ChIP, co-immunoprecipitation, RNAi depletion, reporter assay, 3D culture, mouse tumor model\",\n      \"journal\": \"Cancer cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — ChIP demonstrating promoter occupancy, functional rescue with multiple cellular assays and in vivo model\",\n      \"pmids\": [\"16843262\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"CtIP interacts with Ikaros via CtIP's Rb interaction domain (not via CtBP); CtIP contributes to Ikaros-mediated transcriptional repression independent of HDACs; mutation abolishing Ikaros–CtIP interaction significantly reduces Ikaros repression activity.\",\n      \"method\": \"Co-immunoprecipitation, transcriptional reporter assay, HDAC inhibitor treatment, domain mutant analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with domain mutants and functional repression assay, single lab\",\n      \"pmids\": [\"11959865\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SERBP1 binds CtIP mRNA and regulates CtIP expression at the translational level in S phase; SERBP1 depletion reduces polysome-associated CtIP mRNA and CtIP protein; RNA-binding-deficient SERBP1 (ΔRGG) fails to rescue CtIP translation or HR.\",\n      \"method\": \"RIP-seq, polysome profiling, co-immunoprecipitation, RNA-binding mutant rescue\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RIP-seq and polysome profiling with domain mutant validation, single lab\",\n      \"pmids\": [\"26068472\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"A micropeptide PACMP prevents CtIP ubiquitination by inhibiting the CtIP–KLHL15 interaction, thereby maintaining CtIP abundance and promoting HR; PACMP also binds DNA damage-induced poly(ADP-ribose) chains to enhance PARylation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, HR reporter, PARP inhibitor sensitivity assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical Co-IP and functional HR assays, single lab\",\n      \"pmids\": [\"35219381\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Fusion of a minimal N-terminal CtIP fragment (HE domain, containing CDK phosphorylation sites and multimerization domain) to Cas9 stimulates HDR by approximately twofold; this HDR enhancement is CDK-phosphorylation and multimerization dependent.\",\n      \"method\": \"Cas9-CtIP fusion, HDR reporter assay, phospho-site and multimerization domain mutagenesis, human cell lines/iPSC/rat zygotes\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional domain dissection in multiple systems, single lab\",\n      \"pmids\": [\"29556040\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CtIP (RBBP8) is a multifunctional nuclear protein that acts as a central regulator of DNA double-strand break repair pathway choice: it is recruited to DSBs specifically in S/G2 phase—controlled by CDK-mediated phosphorylation (primarily at Thr-847) and additional modifications (ATR-dependent phosphorylation, SUMOylation at K896 by CBX4, sequential SUMOylation/ubiquitination by PIAS4/RNF4, proteasomal turnover via APC/C-Cdh1 and Cullin3-KLHL15)—where it functions as a co-factor of the MRE11-RAD50-NBS1 (MRN) endonuclease to catalyze 5'-strand incision near protein-blocked DSB ends, and also promotes long-range resection by stimulating both the BLM-DNA2 and EXO1 pathways; it forms a tetrameric (dimer-of-dimers) architecture essential for DSB localization and activity, interacts in a phospho-Ser327-dependent manner with BRCA1 BRCT domains (structurally defined at 2.5 Å) to accelerate resection and remove protein adducts at complex ends, drives microhomology-mediated alternative NHEJ and chromosomal translocations, and additionally protects stalled replication forks from DNA2-mediated degradation; outside of DNA repair, CtIP functions as a transcriptional co-repressor in complexes with BRCA1, CtBP, Rb, ZBRK1, Ikaros, SHARP, and LMO4 to regulate G1/S transition and gene expression programs.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RBBP8 (CtIP) is a nuclear DNA double-strand break (DSB) repair factor that governs repair pathway choice by initiating and controlling end resection in S/G2 phase [#0, #6]. It is recruited to DSBs in a manner dependent on the MRN complex, ATM kinase activity, and a direct DNA-binding motif, where it promotes the transition from break sensing to resection [#0, #7]. Mechanistically, phosphorylated CtIP acts as a co-factor of the MRE11 endonuclease within MRN to catalyze 5'-strand incision near protein-blocked DSB ends, a function requiring CtIP phosphorylation at Thr-847 and NBS1, which senses CtIP phosphorylation through its FHA/BRCT domains to activate MRE11-RAD50 [#9, #41]; CtIP additionally possesses intrinsic endonuclease activity required for processing topoisomerase adducts, common fragile sites, and secondary-structure-containing ends [#10, #30]. Beyond short-range incision, CtIP drives long-range resection by stimulating both BLM helicase activity and the ATP-driven motor of DNA2 [#52, #53]. CtIP function is gated by cell-cycle and damage signaling: CDK phosphorylation at Thr-847 is essential for resection and induces interaction with NBS1, while phospho-Ser327 nucleates a structurally defined interaction with the BRCA1 BRCT domains that accelerates resection and is specifically required for removing protein adducts at complex ends [#3, #5, #14, #17, #33, #34]. CtIP assembles a homotetramer through a 'dimer-of-dimers' architecture and dimerizes via an N-terminal coiled-coil, an oligomeric state essential for DSB localization, resection, and DNA bridging [#11, #22, #23, #51]. The BRCA1-CtIP axis directs S/G2 cells toward error-free homologous recombination by antagonizing RIF1, whereas CtIP-driven resection also generates microhomology for alternative NHEJ, mediating chromosomal translocations and class-switch recombination [#6, #16, #24, #25]. CtIP abundance and chromatin retention are tightly controlled by an elaborate post-translational network including APC/C(Cdh1)- and Cullin3-KLHL15-mediated degradation, opposing deubiquitinases USP4 and USP52, and SUMOylation by CBX4 and PIAS4 coupled to RNF4-dependent turnover [#31, #32, #43, #44, #46, #47]. Independently of DSB resection, CtIP protects reversed stalled replication forks from DNA2-mediated degradation in cooperation with BRCA1 [#49, #50]. Outside DNA repair, CtIP functions as a transcriptional co-repressor in complexes with BRCA1, CtBP, Rb, ZBRK1, Ikaros, SHARP, and LMO4, and counteracts Rb-mediated G1 restraint to promote the G1/S transition [#19, #20, #21, #55, #56, #57, #58]. Truncating mutations in RBBP8 cause Seckel syndrome (SCKL2) and Jawad syndrome, with patient cells showing defective damage-induced ssDNA formation and reduced ATR activation [#28].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established CtIP as a physical partner of the BRCA1 BRCT domains, linking it to BRCA1 tumor suppressor function before its repair role was known.\",\n      \"evidence\": \"Yeast two-hybrid and in vivo interaction assay with tumor-associated BRCT mutants\",\n      \"pmids\": [\"9738006\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of the interaction not defined\", \"Phosphorylation-dependence not yet established\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Defined CtIP as a cell-cycle-regulated nuclear protein whose levels rise at G1/S and that exists in a BRCA1-BARD1 complex, placing it at the proliferation/repair interface.\",\n      \"evidence\": \"Subcellular fractionation, Co-IP, and cell-cycle synchronization\",\n      \"pmids\": [\"10764811\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of post-transcriptional regulation unresolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Showed CtIP acts as a transcriptional co-repressor beyond BRCA1, contributing to Ikaros-mediated repression via its Rb interaction domain independent of HDACs.\",\n      \"evidence\": \"Co-IP, reporter assays, HDAC inhibitor treatment, domain mutants\",\n      \"pmids\": [\"11959865\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Target gene programs not mapped\", \"Relationship to repair role unclear\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Defined the phospho-Ser327-dependent CtIP-BRCA1 BRCT interaction at atomic resolution and linked CtIP to the G2/M checkpoint, providing the structural basis for the interaction and explaining cancer-associated BRCA1 mutations.\",\n      \"evidence\": \"X-ray crystallography (2.5 Å), ITC, mutant analysis, Co-IP, and cell-cycle/checkpoint assays\",\n      \"pmids\": [\"16101277\", \"15485915\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional output of the interaction in resection not yet dissected\", \"Kinase responsible for S327 not identified\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Demonstrated CtIP is essential for embryonic viability and counteracts Rb-mediated G1 restraint, establishing a non-repair role in cell-cycle control.\",\n      \"evidence\": \"Mouse gene knockout and Rb genetic epistasis in MEFs/Saos-2\",\n      \"pmids\": [\"15831459\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism of Rb antagonism partly inferred\", \"Does not separate repair from proliferative functions\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identified CtIP as the human factor required for S/G2-restricted DSB resection acting with the MRN complex, establishing its central role in repair pathway choice.\",\n      \"evidence\": \"siRNA depletion, laser micro-irradiation, Co-IP, and cell-cycle fractionation\",\n      \"pmids\": [\"17965729\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct enzymatic contribution to resection not yet defined\", \"Recruitment mechanism not fully mapped\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Resolved how cell-cycle and damage signaling gate CtIP, showing CDK phosphorylation at Thr-847 enables resection/HR while phospho-S327/BRCA1 acts as a switch between G1 end-joining and S/G2 HR.\",\n      \"evidence\": \"Site-directed mutagenesis, CDK inhibition, DT40 gene targeting, RPA foci and repair pathway assays\",\n      \"pmids\": [\"19202191\", \"19357644\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct biochemical activity of phospho-CtIP not yet reconstituted\", \"Full kinase circuitry incomplete\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Established CtIP as a driver of microhomology-mediated alternative end-joining, including chromosomal translocations and class-switch recombination.\",\n      \"evidence\": \"Translocation and CSR reporter assays with siRNA/shRNA depletion and junction sequencing\",\n      \"pmids\": [\"21131978\", \"21131982\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Distinction between resection-dependent and -independent contributions to alt-NHEJ not fully resolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Revealed CtIP carries intrinsic, MRN-independent endonuclease activity dedicated to processing protein adducts and structured DNA ends.\",\n      \"evidence\": \"Recombinant protein purification, in vitro endonuclease assays, separation-of-function nuclease mutants, cell-based assays\",\n      \"pmids\": [\"24837676\", \"24837675\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relationship between intrinsic and MRN-cofactor nuclease activities debated\", \"Substrate specificity in vivo incompletely mapped\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined the homotetrameric 'dimer-of-dimers' architecture of CtIP as essential for DSB localization and resection.\",\n      \"evidence\": \"X-ray crystallography, SEC-MALS/AUC, mutagenesis, and HR reporter assays\",\n      \"pmids\": [\"25558984\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How oligomeric state mechanistically couples to nuclease stimulation not fully resolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Reconstituted phospho-CtIP as a direct co-factor of the MRE11 endonuclease within MRN that incises 5'-terminated strands, providing the biochemical basis for resection initiation.\",\n      \"evidence\": \"Reconstituted in vitro nuclease assays with purified human proteins and phospho-site mutagenesis\",\n      \"pmids\": [\"27889449\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural mechanism of MRE11 activation not resolved here\", \"Role of NBS1 sensing addressed later\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Extended CtIP function to long-range resection by showing it interacts with and stimulates BLM helicase and enhances DNA2 cleavage.\",\n      \"evidence\": \"Co-IP and in vitro helicase/nuclease assays with purified proteins\",\n      \"pmids\": [\"29020620\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Domain requirements detailed in later DNA2 work\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified a resection-independent role for CtIP in protecting reversed stalled replication forks from DNA2-mediated degradation in cooperation with BRCA1.\",\n      \"evidence\": \"DNA fiber assays with CtIP depletion, DNA2/MRE11 inhibition, and genetic epistasis\",\n      \"pmids\": [\"30344097\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism of fork protection partly defined\", \"Separation from RAD51 nucleofilament stabilization role clarified later\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Clarified that NBS1 senses CtIP phosphorylation via FHA/BRCT domains to activate MRE11-RAD50, distinguishing phosphorylation-dependent and -independent modes of MRE11 stimulation.\",\n      \"evidence\": \"Reconstituted in vitro nuclease assays with NBS1 domain mutants\",\n      \"pmids\": [\"30787182\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural detail of the NBS1-CtIP-MRE11 activated state not resolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Mapped distinct CtIP domains for DNA bridging, DNA2 motor stimulation, and showed DNA-PK promotes the MRN-phospho-CtIP transition from NHEJ to HR.\",\n      \"evidence\": \"Single-molecule nanofluidic bridging, reconstituted DNA2 ATPase/curtain assays, single-molecule and cellular DNA-PK processing assays\",\n      \"pmids\": [\"32417418\", \"32241893\", \"31934630\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo coordination of bridging, nuclease, and motor-stimulatory activities not fully integrated\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Detailed the layered PTM network controlling CtIP abundance and chromatin retention, including KLHL15/Cullin3 and APC/C(Cdh1) degradation, CBX4 and PIAS4-RNF4 SUMO-coupled turnover, and opposing deubiquitinases USP4/USP52.\",\n      \"evidence\": \"Co-IP, ubiquitination/SUMOylation/deubiquitination assays, site-specific mutagenesis, and resection/HR readouts across multiple studies\",\n      \"pmids\": [\"25349192\", \"27561354\", \"28740167\", \"33723063\", \"26387952\", \"33097710\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Hierarchy and crosstalk among PTM events incompletely ordered\", \"Several findings from single labs\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Linked RBBP8 to human disease, establishing truncating mutations as causative of Seckel and Jawad syndromes through defective ssDNA formation and ATR activation.\",\n      \"evidence\": \"Patient-derived cell lines with ssDNA/BrdU and ATR signaling assays and dominant-negative mutant overexpression\",\n      \"pmids\": [\"21998596\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genotype-phenotype relationships for the two syndromes not fully resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CtIP's multiple separable activities — short-range nuclease cofactor, long-range resection stimulation, DNA bridging, fork protection, and transcriptional co-repression — are coordinated within a single regulatory architecture in vivo remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified structural model integrating oligomerization, nuclease, and bridging domains\", \"Spatiotemporal switching among functions not defined\", \"Quantitative contribution of transcriptional roles to physiology unclear\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140097\", \"supporting_discovery_ids\": [9, 10, 30, 41]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [7, 51]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [9, 52, 53, 41]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [19, 20, 21, 55, 57, 58]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [51, 40]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [18, 0]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [4, 0, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [0, 6, 9, 24]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [19, 38, 39]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [20, 21, 57]},\n      {\"term_id\": \"R-HSA-69306\", \"supporting_discovery_ids\": [49, 50]}\n    ],\n    \"complexes\": [\n      \"MRN (MRE11-RAD50-NBS1) complex (as phospho-CtIP cofactor)\",\n      \"BRCA1-CtIP-MRN complex\",\n      \"BRCA1-CtIP-ZBRK1 repressor complex\",\n      \"LMO4-BRCA1-CtIP-Ldb1 complex\"\n    ],\n    \"partners\": [\n      \"BRCA1\",\n      \"NBS1\",\n      \"MRE11\",\n      \"DNA2\",\n      \"BLM\",\n      \"EXO1\",\n      \"FANCD2\",\n      \"KLHL15\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":{"gene":"RBBP8","tier":"GROUNDING","verdict":"Evidence-grounding concern","subtype":"fabrication","uniprot_band":"rich","rules_fired":"R7","issue":"R7: fabricated (no corpus paper): 32417418"},"evaluation":{"pairwise":"win","faith_supported":11,"faith_total":11,"faith_pct":100.0}}