{"gene":"RAD18","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":1994,"finding":"Yeast Rad18 forms a specific complex with Rad6 (ubiquitin-conjugating enzyme), and Rad18 binds single-stranded DNA, providing a mechanism for targeting Rad6 ubiquitin-conjugating activity to damage-containing DNA regions. Rad6 has no intrinsic affinity for DNA; the complex with Rad18 confers this targeting.","method":"Co-immunoprecipitation, DNA binding assays, dominant-negative overexpression genetics","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal biochemical interaction confirmed by co-IP, DNA binding assays, and dominant-negative genetics; independently reproduced in subsequent studies","pmids":["7926769"],"is_preprint":false},{"year":1997,"finding":"Purified yeast Rad6-Rad18 heterodimer has ubiquitin-conjugating activity, binds single-stranded DNA, and possesses ssDNA-dependent ATPase activity, demonstrating that ubiquitin conjugation is physically coupled to DNA binding and ATPase activities in the same complex.","method":"Co-overexpression in yeast, purification to near homogeneity, in vitro ubiquitination assay, ssDNA binding assay, ATPase assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted complex with multiple orthogonal in vitro biochemical activities demonstrated","pmids":["9287349"],"is_preprint":false},{"year":1997,"finding":"The Rad6-Rad18 interaction is mediated by residues 371–410 near the C-terminus of Rad18 (sufficient for Rad6 binding) and residues 141–149 at the C-terminus and residues 10–22 at the N-terminus of Rad6, defining the dimerization interface between these two proteins.","method":"Deletion mutagenesis, yeast two-hybrid, protein interaction assays","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis mapping with functional interaction readouts, single lab","pmids":["9234711"],"is_preprint":false},{"year":2000,"finding":"Human RAD18 protein interacts with human HHR6A and HHR6B (human Rad6 homologs) through its conserved RING-finger motif; stable complexes were purified from yeast co-expression. Mutation of the RING-finger motif in hRad18 causes sensitivity to UV, MMS, and mitomycin C and defective replication of UV-damaged DNA.","method":"Co-expression and purification in yeast, RING-finger mutation analysis in stable human cell transformants, UV/MMS/MMC sensitivity assays, postreplication repair assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — mutagenesis with functional cellular readouts plus biochemical purification, replicated from yeast findings","pmids":["10884424","10908344"],"is_preprint":false},{"year":2004,"finding":"Human Rad18 and Rad6B monoubiquitinate PCNA in vitro. UV irradiation induces Rad18 relocalization in the nucleus and colocalization with PCNA. Rad18 (together with Rad6) is required for PCNA monoubiquitination and for recruitment of DNA polymerase eta (Polη) to UV-induced nuclear foci; Polη interacts preferentially with monoubiquitinated PCNA. Rad18 physically associates with Polη through C-terminal domains of both proteins.","method":"In vitro ubiquitination assay with purified proteins, RAD18-knockout cell lines, immunofluorescence focus formation, co-immunoprecipitation, UV irradiation","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of PCNA monoubiquitination, knockout cells with multiple orthogonal assays, replicated across multiple labs","pmids":["15359278"],"is_preprint":false},{"year":2006,"finding":"Rad18-mediated PCNA monoubiquitination regulates the interaction between PCNA and DNA polymerase kappa (Polκ). BPDE-induced PCNA ubiquitination is abolished by siRNA-mediated Rad18 knockdown; a monoubiquitination-resistant PCNA mutant fails to interact with Polκ. Rad18-deficient cells show defective recovery from BPDE-induced S-phase checkpoints. ATR/Chk1 signaling is required upstream of Rad18-mediated PCNA monoubiquitination.","method":"siRNA knockdown, Rad18-/- mouse cells, monoubiquitination-deficient PCNA mutant, co-immunoprecipitation, checkpoint kinase activation assays","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, knockout/knockdown, mutant PCNA, multiple orthogonal methods","pmids":["16611994"],"is_preprint":false},{"year":2006,"finding":"Vertebrate Rad18 suppresses access of non-homologous end joining (NHEJ) to double-strand breaks, thereby facilitating homologous recombination-mediated DSB repair. Deletion of NHEJ in rad18-deficient DT40 cells completely restores HR-mediated DSB repair.","method":"Gene disruption in chicken DT40 cells, double mutant analysis (epistasis), camptothecin sensitivity, HR repair assays","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis with clean knockout cells, double mutant rescue, independently supported in multiple studies","pmids":["17242200"],"is_preprint":false},{"year":2007,"finding":"The SAP domain of human Rad18 (residues 248–282) mediates DNA binding in vitro and is required for Rad18 accumulation at DNA damage sites in vivo and for efficient PCNA monoubiquitination. The C2HC zinc finger domain of Rad18 mediates interaction with ubiquitin (analogous to UBZ/UBM domains), but the SAP domain (not the zinc finger) is responsible for DNA binding.","method":"Domain deletion/mutation analysis, in vitro DNA binding assays, in vivo localization (immunofluorescence), PCNA ubiquitination assay, UV-sensitivity complementation","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro biochemical assays plus in vivo mutant analysis, single lab, multiple orthogonal methods","pmids":["17720710"],"is_preprint":false},{"year":2008,"finding":"Human RAD18 complexed with RAD6B preferentially binds forked and ssDNA structures (present at stalled replication forks) via the SAP domain. SAP domain mutants fail to accumulate at DNA damage sites in vivo and do not guide Polη to stalled replication forks, and fail to suppress UV sensitivity of Rad18-knockout cells.","method":"In vitro DNA binding assays (forked/ssDNA substrates), SAP domain mutagenesis, immunofluorescence localization, UV sensitivity complementation in Rad18-/- cells","journal":"Genes to cells : devoted to molecular & cellular mechanisms","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro DNA binding reconstitution plus in vivo functional rescue with mutagenesis, single lab","pmids":["18363965"],"is_preprint":false},{"year":2008,"finding":"Replication protein A (RPA) physically interacts with Rad18 (in both yeast and mammalian cells) and is required for PCNA ubiquitylation. Purified RPA can recruit Rad18 to ssDNA in vitro. Chromatin association of Rad18 correlates with RPA.","method":"Physical interaction (co-IP), in vitro recruitment assay with purified proteins, yeast genetics","journal":"Cell cycle (Georgetown, Tex.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro reconstitution plus co-IP, single lab, two orthogonal methods","pmids":["19029798"],"is_preprint":false},{"year":2008,"finding":"The Rad6-Rad18 ubiquitin ligase complex ubiquitinates the K197 residue of Rad17 (subunit of the 9-1-1 checkpoint clamp), and this monoubiquitination promotes efficient Rad53 phosphorylation and coordinates DNA damage-responsive transcription (a eukaryotic SOS-like response) with checkpoint function.","method":"Yeast genetics, ubiquitination assays, Rad53 phosphorylation analysis, transcriptional profiling","journal":"Cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical ubiquitination assay plus genetic epistasis, single lab","pmids":["18485869"],"is_preprint":false},{"year":2008,"finding":"In S. cerevisiae, PCNA SUMOylation strongly enhances Rad18-mediated PCNA ubiquitylation; Rad18 contains a SUMO-interacting motif (SIM) that mediates this stimulation and also mediates Rad18 auto-SUMOylation, suggesting sumoylated PCNA is the physiological substrate for budding yeast Rad18.","method":"Yeast genetics, in vitro ubiquitylation assays with sumoylated PCNA, SIM mutagenesis","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro reconstitution with mutagenesis, single lab","pmids":["23034805"],"is_preprint":false},{"year":2009,"finding":"RAD18 (via its E3 ligase activity) promotes homologous recombination (HR) repair of DSBs by being recruited to break sites through RNF8-mediated DNA damage signaling and directly interacting with the recombinase RAD51C to facilitate HRR.","method":"Co-immunoprecipitation (RAD18-RAD51C interaction), RAD18-knockout cells, HR reporter assays, immunofluorescence, epistasis with RNF8","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct protein interaction (co-IP), knockout cells, multiple functional readouts, independently supported","pmids":["19396164"],"is_preprint":false},{"year":2009,"finding":"In S. cerevisiae, Rad18 is required for the formation of X-shaped sister chromatid junctions (SCJs) at damaged replication forks through PCNA polyubiquitylation involving Mms2/Ubc13; this template-switch mechanism requires SUMOylated PCNA and is coordinated with Rad51-dependent recombination.","method":"Yeast genetics (double mutants), 2D gel electrophoresis to detect SCJs (physical evidence for template switch), epistasis analysis","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — physical detection of DNA intermediates plus genetic epistasis, rigorous study in high-impact journal","pmids":["19092928"],"is_preprint":false},{"year":2009,"finding":"PCNA poly-ubiquitylation proceeds by sequential action of two complexes: Rad6-Rad18 initiates monoubiquitylation (requiring PCNA to be loaded on DNA), and Ubc13-Mms2-Rad5 independently elongates the chain stepwise. Chain extension does not strictly require DNA-loaded PCNA.","method":"In vitro PCNA ubiquitylation reconstitution with purified components, mutational analysis of ubiquitin attachment sites","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — full in vitro reconstitution with purified components and mechanistic dissection, single lab","pmids":["19851286"],"is_preprint":false},{"year":2009,"finding":"RAD18 monoubiquitinates K1268 in the KBD domain of 53BP1 in vitro; a K1268R monoubiquitination-resistant 53BP1 mutant is not efficiently retained at chromatin near DSBs. RAD18 associates with 53BP1 and is recruited to DSB sites in a 53BP1-dependent manner specifically during G1 phase, promoting 53BP1-directed DSB repair.","method":"In vitro ubiquitination assay, co-immunoprecipitation, immunofluorescence in Rad18-null cells, G1-specific analysis","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro ubiquitination plus cellular co-IP and mutant analysis, single lab","pmids":["19228710"],"is_preprint":false},{"year":2010,"finding":"RAD18 is phosphorylated by the protein kinase Cdc7 (DDK) on a serine cluster in its Polη-binding motif. DDK-dependent phosphorylation of Rad18 is required for efficient Rad18–Polη association and for redistribution of Polη to sites of replication fork stalling after DNA damage.","method":"Kinase assay (Cdc7/DDK phosphorylation of Rad18), phosphorylation site mutagenesis, co-immunoprecipitation, immunofluorescence","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — kinase assay with mutagenesis plus cellular co-IP and localization, single lab","pmids":["21098111"],"is_preprint":false},{"year":2010,"finding":"RAD18-mediated monoubiquitination of PCNA at Lys164 is required for recruitment of the E3 ligase FANCL to chromatin, and monoubiquitinated PCNA stimulates FANCL-catalyzed FANCD2 and FANCI monoubiquitination, thus activating the Fanconi anemia pathway.","method":"RAD18 knockdown/knockout, chromatin fractionation, ubiquitination assays, epistasis with PCNA-K164R mutant","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — knockout/knockdown with chromatin fractionation and ubiquitination assays, mechanistically defined pathway, independently supported","pmids":["20937699"],"is_preprint":false},{"year":2010,"finding":"RAD18 binds FANCD2 directly and is required for efficient monoubiquitylation and chromatin localization of both FANCD2 and FANCI. RING domain mutation of RAD18 abolishes interaction with FANCD2 and prevents chromatin loading. PCNA ubiquitylation-resistant cells show normal FANCD2 ubiquitylation, suggesting RAD18 contributes to FA pathway independently of PCNA ubiquitination for FANCD2 loading.","method":"RAD18-knockout human cells, co-immunoprecipitation (RAD18-FANCD2), chromatin fractionation, RING domain mutagenesis, immunofluorescence","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP and knockout with functional readouts, single lab","pmids":["21355096"],"is_preprint":false},{"year":2010,"finding":"SNM1A contains a UBZ (ubiquitin-binding zinc finger) domain; RAD18-dependent monoubiquitination of PCNA is required for SNM1A nuclear focus assembly and recruitment to ICL lesions (MMC, UV), defining a RAD18–PCNA(Ub)–SNM1A pathway for ICL resistance.","method":"Focus formation assays, RAD18-dependent ubiquitination analysis, UBZ domain mutation, MMC/UV treatment","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RAD18-dependence of SNM1A recruitment established by knockdown with focus formation assay and domain mutagenesis, single lab","pmids":["20385554"],"is_preprint":false},{"year":2011,"finding":"The E2 enzyme Rad6b is intrinsically capable of catalyzing ubiquitin chain formation; this activity is inhibited by its interaction with the R6BD domain of Rad18, which competes with ubiquitin for a noncovalent 'backside' binding site on Rad6, thereby restricting PCNA ubiquitination to monoubiquitination.","method":"NMR spectroscopy, X-ray crystallography, in vitro ubiquitination assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — structure determination (NMR + X-ray) combined with in vitro biochemical validation, single rigorous study","pmids":["21422291"],"is_preprint":false},{"year":2011,"finding":"The Rad18 RING domain forms a homodimer; X-ray crystallography reveals it dimerizes through helices adjacent to the RING domains. NMR and mutagenesis show the Rad6b binding site on the RING domain is conserved. The full-length Rad18 homodimer binds only one Rad6b molecule (asymmetric), whereas isolated RING dimer can recruit two Rad6b molecules.","method":"X-ray crystallography, NMR spectroscopy, site-directed mutagenesis, binding assays","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure plus NMR and mutagenesis validation, single lab but rigorous methods","pmids":["21549715"],"is_preprint":false},{"year":2011,"finding":"RAD6A and RAD18 form a ternary complex RAD6A-(RAD18)₂; presence of only one R6BD (RAD6-binding domain) in the RAD18 dimer is sufficient for complex formation and E3 ligase activity. Mutations in both subunits of either RING or SAP domains strongly reduce ligase activity, while inactivation in only one subunit has no effect, demonstrating functional asymmetry.","method":"Differential epitope-tagging of RAD18 subunits, mutant complex analysis, in vitro ubiquitination assay","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro biochemical assays with distinct-tagged subunits, single lab","pmids":["21967848"],"is_preprint":false},{"year":2011,"finding":"NBS1 binds RAD18 after UV irradiation through a C-terminal domain that shares structural and functional similarity with the RAD18-interacting domain of RAD6, and mediates recruitment of RAD18 to DNA damage sites. NBS1 disruption abolishes RAD18-dependent PCNA ubiquitination and Polη focus formation. NBS1 and RAD6 can simultaneously interact with RAD18 homodimers.","method":"Co-immunoprecipitation, NBS1-knockout cells, PCNA ubiquitination assays, Polη focus formation, domain mapping","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, knockout cells, multiple functional readouts, structural similarity mapped, single lab","pmids":["21884979"],"is_preprint":false},{"year":2013,"finding":"DNA polymerase eta (Polη) has a non-catalytic role in recruiting Rad18 to PCNA and promoting PCNA monoubiquitination via its C-terminal domain that binds both Rad18 and PCNA. This function is unique to Polη among Y-family TLS polymerases and is dissociable from its catalytic activity; catalytically-inactive full-length Polη in XPV cells still promotes error-prone TLS polymerase recruitment.","method":"Polη domain deletion/mutation analysis, co-immunoprecipitation, PCNA ubiquitination assay in XPV cells, immunofluorescence","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP with domain mutants plus functional cellular assays, single lab","pmids":["23345618"],"is_preprint":false},{"year":2014,"finding":"SIVA1 constitutively interacts with PCNA via a PIP motif and serves as a molecular bridge between RAD18 and PCNA, targeting RAD18 E3 ligase activity to PCNA. SIVA1 knockdown compromises RAD18-dependent PCNA monoubiquitination and Polη focus formation.","method":"Affinity purification of PCNA complex, co-immunoprecipitation, SIVA1 knockdown, PCNA ubiquitination assay, focus formation","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — affinity purification plus functional knockdown with ubiquitination and focus readouts, single lab","pmids":["24958773"],"is_preprint":false},{"year":2014,"finding":"NMR structure of the human Rad18 C2HC zinc finger (UBZ4 type) in complex with ubiquitin shows it adopts a β1-β2-α fold and binds ubiquitin via the α-helix and β1 strand; this binding mode differs from the Polη UBZ3 domain which uses only the α-helix. This defines two structural classes of UBZ domain with distinct ubiquitin binding interfaces.","method":"NMR spectroscopy, chemical shift perturbation mapping, structure determination of Rad18-UBZ4–ubiquitin complex","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR structure with binding site mapping, single lab but rigorous structural study","pmids":["25162118"],"is_preprint":false},{"year":2014,"finding":"Monoubiquitination of Rad18 itself prevents its localization to DNA damage sites, inhibits PCNA monoubiquitination, and prevents interaction with SHPRH and HLTF (downstream E3s for error-free bypass). Ubiquitinated Rad18 interacts preferentially with the zinc finger domain of non-ubiquitinated Rad18. Damage-specific deubiquitination of Rad18 (by MMS or H₂O₂ treatment) promotes a switch from Rad18•Ub-Rad18 complexes to Rad18-SHPRH complexes for error-free lesion bypass.","method":"Rad18 ubiquitination-resistant mutants, co-immunoprecipitation, immunofluorescence, PCNA ubiquitination assays","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP with domain mutants plus functional cellular readouts, single lab","pmids":["25023518"],"is_preprint":false},{"year":2015,"finding":"USP7 deubiquitylase directly associates with RAD18 via a consensus USP7-binding motif and stabilizes Rad18 protein levels by disassembling Rad18-dependent poly-ubiquitin chains both in vitro and in vivo. Loss of USP7 destabilizes Rad18, compromises UV-induced PCNA mono-ubiquitylation, and impairs Polη recruitment and DNA damage tolerance.","method":"Co-immunoprecipitation, in vitro deubiquitylation assay, USP7 depletion (siRNA/inhibitor), PCNA ubiquitylation assay, Polη focus formation","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro deubiquitylation plus cellular co-IP and functional readouts, single lab","pmids":["25961918"],"is_preprint":false},{"year":2016,"finding":"Rad18 acts as a molecular bridge between Polη and PIAS1 SUMO ligase to promote SUMOylation of Polη at K163, independently of Rad18's E3 ubiquitin ligase activity. This SUMOylation is required for Polη to travel with replication forks during unchallenged S phase and prevents under-replicated DNA and chromosome fragility.","method":"SUMOylation assays, Rad18 knockdown/mutant analysis, immunofluorescence (Polη replication fork colocalization), chromosomal fragility assays","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP bridging interaction plus functional knockdown, single lab, multiple cellular readouts","pmids":["27811911"],"is_preprint":false},{"year":2017,"finding":"RAD18 binds tightly to monoubiquitylated NCP (nucleosome core particle with H2A-K15Ub) through a ubiquitin-binding domain that contacts both ubiquitin and nucleosome surfaces, displacing 53BP1 from these sites. NMR spectroscopy and biochemistry establish this as a distinct ubiquitin recognition mechanism from that of RNF169.","method":"NMR spectroscopy, biochemical binding assays with NCP-ubme substrates","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR with biochemical validation, structural and mechanistic dissection of RAD18-nucleosome interaction, single lab","pmids":["28506460"],"is_preprint":false},{"year":2004,"finding":"Human Rad18 protein exists in two major forms (non-ubiquitinated ~75 kDa and monoubiquitinated ~85 kDa) detected by mass spectrometry. Rad18 undergoes autoubiquitination at multiple sites via Rad6 (E2); self-association through the zinc finger domain is required for monoubiquitination. Monoubiquitinated Rad18 is predominantly cytoplasmic while non-ubiquitinated Rad18 is nuclear. Rad18 is also polyubiquitinated and degraded by proteasomes.","method":"Western blot, mass spectrometry, in vitro ubiquitination assay, zinc finger mutant (C207F) analysis, subcellular fractionation","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — mass spectrometry identification plus in vitro assays and cellular fractionation, single lab","pmids":["15509568"],"is_preprint":false},{"year":2009,"finding":"Physical interaction between WRNIP1 and RAD18: WRNIP1 binds forked and template/primer DNA in an ATP-dependent manner, and directly interacts with RAD18; WRNIP1 interferes with RAD18 binding to forked DNA, while RAD18 enhances WRNIP1 binding to these DNA substrates, suggesting competitive/cooperative targeting at stalled forks.","method":"Co-immunoprecipitation, in vitro DNA binding assays with forked DNA substrates, reciprocal interaction analysis","journal":"Genes & genetic systems","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus in vitro DNA binding assays, single lab","pmids":["19556710"],"is_preprint":false},{"year":2016,"finding":"REV1 promotes PCNA monoubiquitylation after UV radiation by interacting with ubiquitylated RAD18, which facilitates the release of non-ubiquitylated RAD18 from ubiquitylated RAD18 trapping, allowing free RAD18 to be recruited to chromatin for TLS function.","method":"Co-immunoprecipitation of REV1 with ubiquitylated RAD18, PCNA monoubiquitylation assays, chromatin recruitment assays, UV/HU/MMC treatment","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP showing preference for Ub-RAD18, functional PCNA ubiquitylation assay, single lab","pmids":["26795561"],"is_preprint":false},{"year":2019,"finding":"An engineered RAD18 variant (e18) stimulates CRISPR-mediated HDR by suppressing localization of the NHEJ-promoting factor 53BP1 to DSBs. Mechanistically, e18 induces HDR by reducing 53BP1 recruitment to break sites.","method":"Genome-wide ORF screen in human cells, 53BP1 localization assays (immunofluorescence), HDR reporter assays, RAD18 domain mapping","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional screen with mechanistic follow-up (53BP1 localization suppression), single lab","pmids":["31363085"],"is_preprint":false},{"year":2020,"finding":"Rad6/Rad18 complex is recruited to RPA filaments via Rad18·RPA interactions and translocates randomly along RPA filaments (ATP-independent), promoting productive interactions with PCNA and significantly enhancing PCNA monoubiquitination. This is the first example of ATP-independent protein complex translocation along a protein filament.","method":"Kinetic ubiquitination assays, single-molecule FRET microscopy, RPA filament reconstitution","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — single-molecule FRET plus kinetic reconstitution assays, mechanistically rigorous, single lab","pmids":["33242956"],"is_preprint":false},{"year":2006,"finding":"A Polη-containing complex purified from HeLa cells includes Rad18, Rad6, and Rev1; these components are specifically enriched in chromatin-bound fractions after UV irradiation, S-phase synchronization, or S-phase arrest, indicating that stalled replication forks strengthen interactions among these TLS factors.","method":"Affinity purification of Polη complex, mass spectrometry, Western blot, chromatin fractionation","journal":"Genes to cells : devoted to molecular & cellular mechanisms","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mass spectrometry-based complex identification with chromatin fractionation validation, single lab","pmids":["16824193"],"is_preprint":false}],"current_model":"RAD18 is an E3 RING-finger ubiquitin ligase that forms a heterodimeric complex with the E2 enzyme RAD6 (HHR6A/B); the complex is recruited to stalled replication forks via RAD18's SAP domain binding to forked/ssDNA structures (assisted by RPA, NBS1, PCNA-bound SIVA1, and DDK phosphorylation of RAD18), where it monoubiquitinates PCNA at K164, creating a platform that recruits Y-family translesion synthesis (TLS) polymerases (Polη, Polκ, Polι) through their ubiquitin-binding domains; RAD18 itself is regulated by autoubiquitination (which controls its nuclear/cytoplasmic distribution) and by USP7-mediated deubiquitylation; beyond TLS, RAD18 promotes homologous recombination repair of DSBs by suppressing NHEJ access, facilitating RAD51C-mediated recombination, activating the Fanconi anemia pathway via PCNA-ubiquitination-dependent FANCL recruitment and direct interaction with FANCD2, and acting as a molecular bridge to promote Polη SUMOylation independent of its ubiquitin ligase activity; at DSBs during G1, RAD18 monoubiquitinates 53BP1-K1268 to retain it at chromatin, while at DSBs competing RNF169 and RAD18 displace 53BP1 by binding ubiquitylated NCP with higher affinity."},"narrative":{"mechanistic_narrative":"RAD18 is a RING-finger E3 ubiquitin ligase that, in heterodimeric partnership with the E2 conjugating enzyme RAD6 (HHR6A/B), couples ubiquitin transfer to DNA damage to govern DNA damage tolerance and double-strand break repair pathway choice [PMID:7926769, PMID:10884424, PMID:10908344, PMID:15359278]. The complex is targeted to damaged DNA because RAD18 supplies DNA-binding and recruitment functions that RAD6 lacks: its SAP domain binds forked and single-stranded DNA structures at stalled replication forks and is required for accumulation at damage sites and efficient PCNA monoubiquitination [PMID:17720710, PMID:18363965]. Recruitment is reinforced by multiple partners that bridge RAD18 to chromatin and to its substrate — RPA filaments, along which RAD6-RAD18 translocates ATP-independently to engage PCNA [PMID:19029798, PMID:33242956], NBS1 acting through a RAD6-like RAD18-interacting domain [PMID:21884979], the PCNA-bound adaptor SIVA1 [PMID:24958773], and DDK/Cdc7 phosphorylation that licenses RAD18–Polη association [PMID:21098111]. Its central catalytic output is monoubiquitination of PCNA at K164, which generates a binding platform recruiting Y-family translesion synthesis polymerases Polη and Polκ through their ubiquitin-binding domains [PMID:15359278, PMID:16611994]; the RAD6 backside-binding R6BD domain of RAD18 restricts this reaction to monoubiquitination, with chain elongation for error-free bypass handed off to Ubc13-Mms2-Rad5 [PMID:21422291, PMID:19851286]. Beyond translesion synthesis, RAD18 activates the Fanconi anemia pathway both by PCNA-K164-ubiquitination-dependent FANCL recruitment and through direct interaction with FANCD2 [PMID:20937699, PMID:21355096], promotes homologous recombination by suppressing NHEJ access to breaks and engaging RAD51C [PMID:17242200, PMID:19396164], and modulates 53BP1 — monoubiquitinating 53BP1-K1268 to retain it at G1-phase breaks while also displacing it by high-affinity binding to H2A-K15-ubiquitinated nucleosomes [PMID:19228710, PMID:28506460]. RAD18 also acts as a ubiquitin-ligase-independent molecular bridge promoting PIAS1-mediated Polη SUMOylation [PMID:27811911]. RAD18 activity is self-regulated by autoubiquitination, which partitions it to the cytoplasm and blocks chromatin loading, with USP7-mediated deubiquitylation reversing this to stabilize RAD18 and sustain PCNA monoubiquitination [PMID:15509568, PMID:25023518, PMID:25961918].","teleology":[{"year":1994,"claim":"Established how a ubiquitin-conjugating enzyme could be directed to damaged DNA, by showing Rad18 physically complexes with Rad6 and supplies the DNA-binding activity Rad6 lacks.","evidence":"Co-IP, DNA binding assays, and dominant-negative genetics in yeast","pmids":["7926769"],"confidence":"High","gaps":["Did not identify the in vivo ubiquitination substrate","DNA structure preference within RAD18 not yet mapped to a domain"]},{"year":1997,"claim":"Demonstrated that ubiquitin conjugation, ssDNA binding, and ATPase activities are coupled within one reconstituted Rad6-Rad18 complex, and mapped the dimerization interface.","evidence":"Purified yeast heterodimer with in vitro ubiquitination, ssDNA binding, ATPase assays; deletion mutagenesis and two-hybrid mapping","pmids":["9287349","9234711"],"confidence":"High","gaps":["Physiological substrate of the complex unresolved","Functional role of ssDNA-dependent ATPase activity unclear"]},{"year":2000,"claim":"Extended the model to humans, showing hRAD18 binds HHR6A/B through its RING motif and that RING integrity is required for resistance to UV/MMS/MMC and postreplication repair.","evidence":"Yeast co-expression purification and RING mutation analysis in human cell transformants with damage sensitivity assays","pmids":["10884424","10908344"],"confidence":"High","gaps":["Substrate ubiquitinated in human cells not yet defined"]},{"year":2004,"claim":"Identified PCNA-K164 monoubiquitination as the key catalytic output linking RAD18 to translesion synthesis, recruiting Polη to damage foci.","evidence":"In vitro reconstitution, RAD18-knockout cells, immunofluorescence focus formation, and co-IP after UV","pmids":["15359278"],"confidence":"High","gaps":["How RAD18 senses and is recruited to specific lesions not yet defined","Generality beyond Polη to other TLS polymerases untested"]},{"year":2004,"claim":"Revealed autoregulation by showing RAD18 autoubiquitinates via RAD6, with monoubiquitinated RAD18 partitioning to the cytoplasm and non-ubiquitinated RAD18 to the nucleus.","evidence":"Western blot, mass spectrometry, in vitro ubiquitination, zinc-finger mutant, and subcellular fractionation","pmids":["15509568"],"confidence":"Medium","gaps":["Deubiquitylase reversing autoubiquitination not identified here","Physiological trigger for the localization switch undefined"]},{"year":2006,"claim":"Broadened RAD18 function to homologous recombination by demonstrating it suppresses NHEJ access to DSBs to favor HR-mediated repair.","evidence":"Gene disruption and double-mutant epistasis in DT40 cells with HR repair and CPT sensitivity assays","pmids":["17242200"],"confidence":"High","gaps":["Molecular mechanism of NHEJ suppression not defined in this study","Whether E3 activity is required left open"]},{"year":2006,"claim":"Generalized the PCNA-ubiquitination platform to Polκ and placed it downstream of ATR/Chk1 checkpoint signaling.","evidence":"siRNA and Rad18-/- cells, monoubiquitination-resistant PCNA mutant, co-IP, checkpoint kinase assays; Polη complex purification by MS","pmids":["16611994","16824193"],"confidence":"High","gaps":["Direct link between ATR/Chk1 and RAD18 activation mechanistically undefined"]},{"year":2007,"claim":"Mapped DNA binding to the SAP domain and ubiquitin binding to the C2HC zinc finger, separating recruitment determinants within RAD18.","evidence":"Domain deletion, in vitro DNA binding, in vivo localization, and PCNA ubiquitination assays","pmids":["17720710"],"confidence":"High","gaps":["DNA structure preference of the SAP domain not yet resolved"]},{"year":2008,"claim":"Defined the structural specificity of recruitment, showing RAD18-RAD6B preferentially binds forked/ssDNA at stalled forks via the SAP domain, and identified RPA as a recruiter required for PCNA ubiquitylation.","evidence":"In vitro DNA binding with forked/ssDNA substrates, SAP mutagenesis, rescue assays; co-IP and in vitro RPA recruitment","pmids":["18363965","19029798"],"confidence":"Medium","gaps":["RPA-RAD18 interaction interface not mapped","Single-lab evidence for RPA recruitment"]},{"year":2008,"claim":"Expanded RAD6-RAD18 substrates beyond PCNA, showing Rad17 K197 monoubiquitination coordinates checkpoint signaling, and that PCNA SUMOylation stimulates Rad18 via its SIM in yeast.","evidence":"Yeast genetics, ubiquitination assays, Rad53 phosphorylation, transcriptional profiling; in vitro ubiquitylation with sumoylated PCNA and SIM mutagenesis","pmids":["18485869","23034805"],"confidence":"Medium","gaps":["Conservation of Rad17 ubiquitination in mammals not tested","Whether human RAD18 has an equivalent SIM-dependent stimulation untested"]},{"year":2009,"claim":"Connected RAD18 to RNF8-dependent DSB signaling and direct RAD51C engagement, and established its role in template-switch sister chromatid junction formation through PCNA polyubiquitylation.","evidence":"Co-IP, knockout cells, HR reporters, epistasis with RNF8; 2D gel detection of sister chromatid junctions and in vitro reconstitution of sequential PCNA poly-ubiquitylation","pmids":["19396164","19092928","19851286"],"confidence":"High","gaps":["How RAD18 is partitioned between TLS and template-switch outcomes unresolved"]},{"year":2009,"claim":"Identified WRNIP1 as a fork-associated partner that reciprocally modulates RAD18 binding to forked DNA, implicating cooperative/competitive targeting at stalled forks.","evidence":"Co-IP and in vitro forked-DNA binding assays","pmids":["19556710"],"confidence":"Medium","gaps":["Functional consequence in cells not established","Single-lab biochemistry"]},{"year":2009,"claim":"Demonstrated that RAD18 monoubiquitinates 53BP1-K1268 to retain it at chromatin near DSBs specifically during G1 phase.","evidence":"In vitro ubiquitination, co-IP, immunofluorescence in Rad18-null cells with K1268R mutant","pmids":["19228710"],"confidence":"Medium","gaps":["Reconciliation with later 53BP1-displacement role not addressed here","Single-lab evidence"]},{"year":2010,"claim":"Established RAD18 as an upstream activator of the Fanconi anemia pathway through both PCNA-K164-dependent FANCL recruitment and direct FANCD2 binding.","evidence":"Knockout/knockdown, chromatin fractionation, ubiquitination assays, PCNA-K164R epistasis, RING mutagenesis, RAD18-FANCD2 co-IP","pmids":["20937699","21355096"],"confidence":"High","gaps":["Relative contributions of PCNA-dependent vs PCNA-independent FANCD2 loading not fully resolved"]},{"year":2010,"claim":"Showed DDK/Cdc7 phosphorylates RAD18 in its Polη-binding motif to promote RAD18-Polη association and Polη redistribution after damage, and defined a RAD18-PCNA(Ub)-SNM1A pathway for ICL resistance.","evidence":"Kinase assays with phosphosite mutagenesis, co-IP, immunofluorescence; SNM1A UBZ mutation and focus formation under MMC/UV","pmids":["21098111","20385554"],"confidence":"Medium","gaps":["In vivo importance of DDK site phosphorylation across damage types incompletely defined"]},{"year":2011,"claim":"Solved the structural and mechanistic basis for restricting RAD6 to PCNA monoubiquitination and revealed the asymmetric RAD18 homodimer architecture.","evidence":"X-ray crystallography, NMR, in vitro ubiquitination; differential subunit tagging and mutant complex analysis","pmids":["21422291","21549715","21967848"],"confidence":"High","gaps":["How the asymmetric dimer engages substrates in vivo not directly visualized"]},{"year":2011,"claim":"Identified NBS1 as a recruiter of RAD18 to UV damage via a RAD6-like interaction domain, required for PCNA ubiquitination and Polη foci.","evidence":"Co-IP, NBS1-knockout cells, PCNA ubiquitination and Polη focus assays, domain mapping","pmids":["21884979"],"confidence":"High","gaps":["Integration of NBS1, RPA, and SAP-domain recruitment routes not unified"]},{"year":2013,"claim":"Revealed a non-catalytic, feed-forward role for Polη in recruiting RAD18 to PCNA and promoting PCNA monoubiquitination, unique among Y-family polymerases.","evidence":"Polη domain mutants, co-IP, PCNA ubiquitination in XPV cells, immunofluorescence","pmids":["23345618"],"confidence":"Medium","gaps":["Structural basis of the Polη-RAD18-PCNA bridge not determined","Single-lab evidence"]},{"year":2014,"claim":"Identified SIVA1 as a constitutive PCNA-bound bridge targeting RAD18 ligase activity to PCNA, and structurally defined two UBZ classes distinguishing RAD18 from Polη ubiquitin recognition.","evidence":"Affinity purification, co-IP, SIVA1 knockdown with ubiquitination/focus assays; NMR structure of RAD18-UBZ4-ubiquitin complex","pmids":["24958773","25162118"],"confidence":"Medium","gaps":["Hierarchy among SIVA1, RPA, NBS1 recruitment routes undefined"]},{"year":2014,"claim":"Defined autoubiquitination as a negative switch: Ub-RAD18 binds the zinc finger of non-ubiquitinated RAD18 to block damage-site loading, and deubiquitination switches RAD18 toward SHPRH/HLTF for error-free bypass.","evidence":"Ubiquitination-resistant mutants, co-IP, immunofluorescence, PCNA ubiquitination assays","pmids":["25023518"],"confidence":"Medium","gaps":["Identity of the deubiquitylase not addressed in this study","Single-lab evidence"]},{"year":2015,"claim":"Identified USP7 as the deubiquitylase that stabilizes RAD18 by disassembling its poly-ubiquitin chains, sustaining PCNA monoubiquitination and Polη recruitment.","evidence":"Co-IP, in vitro deubiquitylation, USP7 depletion/inhibition with PCNA ubiquitylation and Polη focus assays","pmids":["25961918"],"confidence":"Medium","gaps":["Whether USP7 also reverses the inhibitory monoubiquitination of RAD18 not fully resolved"]},{"year":2016,"claim":"Showed RAD18 bridges Polη to PIAS1 to promote Polη SUMOylation at K163 independent of RAD18 ligase activity, enabling Polη to travel with unchallenged replication forks.","evidence":"SUMOylation assays, RAD18 knockdown/mutants, Polη fork colocalization and chromosome fragility assays","pmids":["27811911"],"confidence":"Medium","gaps":["Structural basis of the RAD18-Polη-PIAS1 bridge undefined","Single-lab evidence"]},{"year":2016,"claim":"Showed REV1 facilitates release of free RAD18 from inhibitory Ub-RAD18 complexes, relieving autoubiquitination-based trapping to permit chromatin recruitment for TLS.","evidence":"Co-IP of REV1 with ubiquitylated RAD18, PCNA monoubiquitylation and chromatin recruitment assays","pmids":["26795561"],"confidence":"Medium","gaps":["Quantitative contribution relative to USP7-mediated control unknown"]},{"year":2017,"claim":"Resolved a 53BP1-displacement mechanism, showing RAD18 binds H2A-K15-ubiquitinated nucleosomes via a domain contacting both ubiquitin and nucleosome surfaces, distinct from RNF169.","evidence":"NMR spectroscopy and biochemical binding assays with NCP-ubme substrates","pmids":["28506460"],"confidence":"High","gaps":["Reconciliation with RAD18-mediated 53BP1 retention not unified mechanistically"]},{"year":2019,"claim":"Demonstrated translational utility by showing an engineered RAD18 variant stimulates CRISPR HDR by reducing 53BP1 recruitment to breaks.","evidence":"Genome-wide ORF screen, 53BP1 localization and HDR reporter assays, domain mapping","pmids":["31363085"],"confidence":"Medium","gaps":["Whether the engineered variant reflects a native RAD18 activity unclear"]},{"year":2020,"claim":"Provided a kinetic mechanism for fork targeting, showing RAD6-RAD18 translocates ATP-independently along RPA filaments to find PCNA and enhance monoubiquitination.","evidence":"Single-molecule FRET, kinetic ubiquitination assays, RPA filament reconstitution","pmids":["33242956"],"confidence":"High","gaps":["How filament translocation integrates with SAP-domain DNA binding in vivo not addressed"]},{"year":null,"claim":"How RAD18 integrates its multiple, partly antagonistic recruitment routes and outputs — TLS versus template switch, 53BP1 retention versus displacement, ubiquitin-ligase-dependent versus -independent SUMO bridging — into a coherent, pathway-selective response remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model for choosing between competing RAD18 outputs","Spatiotemporal regulation across cell-cycle phases incompletely defined","No structure of full-length RAD18 engaging substrate on chromatin"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[0,3,4,20]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[4,5,15,17]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[0,7,8]},{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[1]},{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[30]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[25,29]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[4,31]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[31]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[8,17,30]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[6,12,17]},{"term_id":"R-HSA-69306","term_label":"DNA Replication","supporting_discovery_ids":[4,5,14]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,4,20]}],"complexes":["RAD6-RAD18 (E2-E3) heterodimer"],"partners":["RAD6 (HHR6A/HHR6B)","PCNA","POLH (POLΗ)","RPA","NBS1","FANCD2","RAD51C","USP7"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NS91","full_name":"E3 ubiquitin-protein ligase RAD18","aliases":["Postreplication repair protein RAD18","hHR18","hRAD18","RING finger protein 73","RING-type E3 ubiquitin transferase RAD18"],"length_aa":495,"mass_kda":56.2,"function":"E3 ubiquitin-protein ligase involved in postreplication repair of UV-damaged DNA. Postreplication repair functions in gap-filling of a daughter strand on replication of damaged DNA. Associates to the E2 ubiquitin conjugating enzyme UBE2B to form the UBE2B-RAD18 ubiquitin ligase complex involved in mono-ubiquitination of DNA-associated PCNA on 'Lys-164'. Has ssDNA binding activity","subcellular_location":"Nucleus; Cytoplasm, cytoskeleton, microtubule organizing center, centrosome","url":"https://www.uniprot.org/uniprotkb/Q9NS91/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RAD18","classification":"Not Classified","n_dependent_lines":8,"n_total_lines":1208,"dependency_fraction":0.006622516556291391},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SEC61B","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/RAD18","total_profiled":1310},"omim":[{"mim_id":"620185","title":"ATELIS SYNDROME 2; ATELS2","url":"https://www.omim.org/entry/620185"},{"mim_id":"620184","title":"ATELIS SYNDROME 1; ATELS1","url":"https://www.omim.org/entry/620184"},{"mim_id":"618467","title":"SMC5-SMC6 COMPLEX LOCALIZATION FACTOR 1; SLF1","url":"https://www.omim.org/entry/618467"},{"mim_id":"616578","title":"ZINC FINGER- AND BTB DOMAIN-CONTAINING PROTEIN 1; ZBTB1","url":"https://www.omim.org/entry/616578"},{"mim_id":"616086","title":"SprT-LIKE N-TERMINAL DOMAIN PROTEIN; SPRTN","url":"https://www.omim.org/entry/616086"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Nuclear bodies","reliability":"Supported"},{"location":"Nuclear speckles","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RAD18"},"hgnc":{"alias_symbol":["RNF73"],"prev_symbol":[]},"alphafold":{"accession":"Q9NS91","domains":[{"cath_id":"3.30.40.10","chopping":"16-98","consensus_level":"high","plddt":95.4955,"start":16,"end":98},{"cath_id":"-","chopping":"254-321","consensus_level":"high","plddt":92.2737,"start":254,"end":321}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NS91","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NS91-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NS91-F1-predicted_aligned_error_v6.png","plddt_mean":67.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RAD18","jax_strain_url":"https://www.jax.org/strain/search?query=RAD18"},"sequence":{"accession":"Q9NS91","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NS91.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NS91/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NS91"}},"corpus_meta":[{"pmid":"15359278","id":"PMC_15359278","title":"Rad18 guides poleta to replication stalling sites through physical interaction and PCNA monoubiquitination.","date":"2004","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/15359278","citation_count":479,"is_preprint":false},{"pmid":"7926769","id":"PMC_7926769","title":"Specific complex formation between yeast RAD6 and RAD18 proteins: a potential mechanism for targeting RAD6 ubiquitin-conjugating activity to DNA damage sites.","date":"1994","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/7926769","citation_count":272,"is_preprint":false},{"pmid":"19396164","id":"PMC_19396164","title":"RAD18 transmits DNA damage signalling to elicit homologous recombination repair.","date":"2009","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/19396164","citation_count":264,"is_preprint":false},{"pmid":"9287349","id":"PMC_9287349","title":"Yeast DNA repair proteins Rad6 and Rad18 form a heterodimer that has ubiquitin conjugating, DNA binding, and ATP hydrolytic activities.","date":"1997","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9287349","citation_count":253,"is_preprint":false},{"pmid":"7038396","id":"PMC_7038396","title":"Characterization of postreplication repair in Saccharomyces cerevisiae and effects of rad6, rad18, rev3 and rad52 mutations.","date":"1981","source":"Molecular & general genetics : MGG","url":"https://pubmed.ncbi.nlm.nih.gov/7038396","citation_count":237,"is_preprint":false},{"pmid":"19092928","id":"PMC_19092928","title":"SUMOylation regulates Rad18-mediated template switch.","date":"2008","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/19092928","citation_count":222,"is_preprint":false},{"pmid":"8524274","id":"PMC_8524274","title":"The rad18 gene of Schizosaccharomyces pombe defines a new subgroup of the SMC superfamily involved in DNA repair.","date":"1995","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/8524274","citation_count":184,"is_preprint":false},{"pmid":"16247017","id":"PMC_16247017","title":"The error-free component of the RAD6/RAD18 DNA damage tolerance pathway of budding yeast employs sister-strand recombination.","date":"2005","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/16247017","citation_count":158,"is_preprint":false},{"pmid":"16611994","id":"PMC_16611994","title":"Rad18 regulates DNA polymerase kappa and is required for recovery from S-phase checkpoint-mediated arrest.","date":"2006","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/16611994","citation_count":150,"is_preprint":false},{"pmid":"2970061","id":"PMC_2970061","title":"The Saccharomyces cerevisiae RAD18 gene encodes a protein that contains potential zinc finger domains for nucleic acid binding and a putative nucleotide binding sequence.","date":"1988","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/2970061","citation_count":129,"is_preprint":false},{"pmid":"10884424","id":"PMC_10884424","title":"Dysfunction of human Rad18 results in defective postreplication repair and hypersensitivity to multiple mutagens.","date":"2000","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/10884424","citation_count":124,"is_preprint":false},{"pmid":"10473635","id":"PMC_10473635","title":"Rad18 is required for DNA repair and checkpoint responses in fission yeast.","date":"1999","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/10473635","citation_count":119,"is_preprint":false},{"pmid":"10747036","id":"PMC_10747036","title":"A novel SMC protein complex in Schizosaccharomyces pombe contains the Rad18 DNA repair protein.","date":"2000","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/10747036","citation_count":115,"is_preprint":false},{"pmid":"21422291","id":"PMC_21422291","title":"E3 ligase Rad18 promotes monoubiquitination rather than ubiquitin chain formation by E2 enzyme Rad6.","date":"2011","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/21422291","citation_count":114,"is_preprint":false},{"pmid":"12374756","id":"PMC_12374756","title":"RAD18 and RAD54 cooperatively contribute to maintenance of genomic stability in vertebrate cells.","date":"2002","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/12374756","citation_count":113,"is_preprint":false},{"pmid":"12509447","id":"PMC_12509447","title":"Enhanced genomic instability and defective postreplication repair in RAD18 knockout mouse embryonic stem cells.","date":"2003","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/12509447","citation_count":106,"is_preprint":false},{"pmid":"26098514","id":"PMC_26098514","title":"Regulation of Rad6/Rad18 Activity During DNA Damage Tolerance.","date":"2015","source":"Annual review of biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/26098514","citation_count":98,"is_preprint":false},{"pmid":"15601840","id":"PMC_15601840","title":"Composition and architecture of the Schizosaccharomyces pombe Rad18 (Smc5-6) complex.","date":"2005","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/15601840","citation_count":98,"is_preprint":false},{"pmid":"31363085","id":"PMC_31363085","title":"Stimulation of CRISPR-mediated homology-directed repair by an engineered RAD18 variant.","date":"2019","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/31363085","citation_count":95,"is_preprint":false},{"pmid":"9234711","id":"PMC_9234711","title":"Domains required for dimerization of yeast Rad6 ubiquitin-conjugating enzyme and Rad18 DNA binding protein.","date":"1997","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/9234711","citation_count":90,"is_preprint":false},{"pmid":"17720710","id":"PMC_17720710","title":"Functional characterization of Rad18 domains for Rad6, ubiquitin, DNA binding and PCNA modification.","date":"2007","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/17720710","citation_count":90,"is_preprint":false},{"pmid":"20937699","id":"PMC_20937699","title":"RAD18-mediated ubiquitination of PCNA activates the Fanconi anemia DNA repair network.","date":"2010","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/20937699","citation_count":85,"is_preprint":false},{"pmid":"12356753","id":"PMC_12356753","title":"Involvement of vertebrate polkappa in Rad18-independent postreplication repair of UV damage.","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12356753","citation_count":82,"is_preprint":false},{"pmid":"19851286","id":"PMC_19851286","title":"Mechanistic analysis of PCNA poly-ubiquitylation by the ubiquitin protein ligases Rad18 and Rad5.","date":"2009","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/19851286","citation_count":80,"is_preprint":false},{"pmid":"23345618","id":"PMC_23345618","title":"A non-catalytic role of DNA polymerase η in recruiting Rad18 and promoting PCNA monoubiquitination at stalled replication forks.","date":"2013","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/23345618","citation_count":79,"is_preprint":false},{"pmid":"29559320","id":"PMC_29559320","title":"Long non-coding RNA ROR promotes radioresistance in hepatocelluar carcinoma cells by acting as a ceRNA for microRNA-145 to regulate RAD18 expression.","date":"2018","source":"Archives of biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/29559320","citation_count":78,"is_preprint":false},{"pmid":"28506460","id":"PMC_28506460","title":"Mechanisms of Ubiquitin-Nucleosome Recognition and Regulation of 53BP1 Chromatin Recruitment by RNF168/169 and RAD18.","date":"2017","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/28506460","citation_count":77,"is_preprint":false},{"pmid":"25913620","id":"PMC_25913620","title":"Tumor suppressor miR-145 reverses drug resistance by directly targeting DNA damage-related gene RAD18 in colorectal cancer.","date":"2015","source":"Tumour biology : the journal of the International Society for Oncodevelopmental Biology and Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/25913620","citation_count":72,"is_preprint":false},{"pmid":"16888649","id":"PMC_16888649","title":"RAD18-independent ubiquitination of proliferating-cell nuclear antigen in the avian cell line DT40.","date":"2006","source":"EMBO reports","url":"https://pubmed.ncbi.nlm.nih.gov/16888649","citation_count":71,"is_preprint":false},{"pmid":"21355096","id":"PMC_21355096","title":"The E3 ubiquitin ligase RAD18 regulates ubiquitylation and chromatin loading of FANCD2 and FANCI.","date":"2011","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/21355096","citation_count":70,"is_preprint":false},{"pmid":"17970741","id":"PMC_17970741","title":"A natural antisense transcript against Rad18, specifically expressed in neurons and upregulated during beta-amyloid-induced apoptosis.","date":"2007","source":"The European journal of neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/17970741","citation_count":70,"is_preprint":false},{"pmid":"23034805","id":"PMC_23034805","title":"A SUMO-interacting motif activates budding yeast ubiquitin ligase Rad18 towards SUMO-modified PCNA.","date":"2012","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/23034805","citation_count":69,"is_preprint":false},{"pmid":"19079240","id":"PMC_19079240","title":"RAD6-RAD18-RAD5-pathway-dependent tolerance to chronic low-dose ultraviolet light.","date":"2008","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/19079240","citation_count":67,"is_preprint":false},{"pmid":"27811911","id":"PMC_27811911","title":"Rad18-dependent SUMOylation of human specialized DNA polymerase eta is required to prevent under-replicated DNA.","date":"2016","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/27811911","citation_count":67,"is_preprint":false},{"pmid":"17242200","id":"PMC_17242200","title":"RAD18 and poly(ADP-ribose) polymerase independently suppress the access of nonhomologous end joining to double-strand breaks and facilitate homologous recombination-mediated repair.","date":"2007","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/17242200","citation_count":67,"is_preprint":false},{"pmid":"11408570","id":"PMC_11408570","title":"Characterization of a novel human SMC heterodimer homologous to the Schizosaccharomyces pombe Rad18/Spr18 complex.","date":"2001","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/11408570","citation_count":66,"is_preprint":false},{"pmid":"15509568","id":"PMC_15509568","title":"Differential regulation of Rad18 through Rad6-dependent mono- and polyubiquitination.","date":"2004","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15509568","citation_count":65,"is_preprint":false},{"pmid":"25961918","id":"PMC_25961918","title":"USP7 is essential for maintaining Rad18 stability and DNA damage tolerance.","date":"2015","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/25961918","citation_count":64,"is_preprint":false},{"pmid":"28835467","id":"PMC_28835467","title":"DNA repair factor RAD18 and DNA polymerase Polκ confer tolerance of oncogenic DNA replication stress.","date":"2017","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/28835467","citation_count":64,"is_preprint":false},{"pmid":"19228710","id":"PMC_19228710","title":"RAD18 promotes DNA double-strand break repair during G1 phase through chromatin retention of 53BP1.","date":"2009","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/19228710","citation_count":64,"is_preprint":false},{"pmid":"18485869","id":"PMC_18485869","title":"Rad6-Rad18 mediates a eukaryotic SOS response by ubiquitinating the 9-1-1 checkpoint clamp.","date":"2008","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/18485869","citation_count":63,"is_preprint":false},{"pmid":"10908344","id":"PMC_10908344","title":"The human RAD18 gene product interacts with HHR6A and HHR6B.","date":"2000","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/10908344","citation_count":61,"is_preprint":false},{"pmid":"21098111","id":"PMC_21098111","title":"Phosphorylated Rad18 directs DNA polymerase η to sites of stalled replication.","date":"2010","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/21098111","citation_count":61,"is_preprint":false},{"pmid":"17158148","id":"PMC_17158148","title":"Human RAD18 is involved in S phase-specific single-strand break repair without PCNA monoubiquitination.","date":"2006","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/17158148","citation_count":59,"is_preprint":false},{"pmid":"18363965","id":"PMC_18363965","title":"Recognition of forked and single-stranded DNA structures by human RAD18 complexed with RAD6B protein triggers its recruitment to stalled replication forks.","date":"2008","source":"Genes to cells : devoted to molecular & cellular mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/18363965","citation_count":58,"is_preprint":false},{"pmid":"11425518","id":"PMC_11425518","title":"Deletion of the SRS2 gene suppresses elevated recombination and DNA damage sensitivity in rad5 and rad18 mutants of Saccharomyces cerevisiae.","date":"2001","source":"Mutation research","url":"https://pubmed.ncbi.nlm.nih.gov/11425518","citation_count":58,"is_preprint":false},{"pmid":"20675655","id":"PMC_20675655","title":"Rad18-mediated translesion synthesis of bulky DNA adducts is coupled to activation of the Fanconi anemia DNA repair pathway.","date":"2010","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20675655","citation_count":57,"is_preprint":false},{"pmid":"2052013","id":"PMC_2052013","title":"A similar defect in UV-induced mutagenesis conferred by the rad6 and rad18 mutations of Saccharomyces cerevisiae.","date":"1991","source":"Mutation research","url":"https://pubmed.ncbi.nlm.nih.gov/2052013","citation_count":56,"is_preprint":false},{"pmid":"16980296","id":"PMC_16980296","title":"Replication-dependent and -independent responses of RAD18 to DNA damage in human cells.","date":"2006","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16980296","citation_count":53,"is_preprint":false},{"pmid":"21478670","id":"PMC_21478670","title":"Rad18 E3 ubiquitin ligase activity mediates Fanconi anemia pathway activation and cell survival following DNA Topoisomerase 1 inhibition.","date":"2011","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/21478670","citation_count":53,"is_preprint":false},{"pmid":"20385554","id":"PMC_20385554","title":"RAD18-dependent recruitment of SNM1A to DNA repair complexes by a ubiquitin-binding zinc finger.","date":"2010","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20385554","citation_count":53,"is_preprint":false},{"pmid":"7498727","id":"PMC_7498727","title":"Specificities of the Saccharomyces cerevisiae rad6, rad18, and rad52 mutators exhibit different degrees of dependence on the REV3 gene product, a putative nonessential DNA polymerase.","date":"1995","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/7498727","citation_count":53,"is_preprint":false},{"pmid":"16783014","id":"PMC_16783014","title":"The RAD6/BRE1 histone modification pathway in Saccharomyces confers radiation resistance through a RAD51-dependent process that is independent of RAD18.","date":"2006","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/16783014","citation_count":53,"is_preprint":false},{"pmid":"21884979","id":"PMC_21884979","title":"NBS1 recruits RAD18 via a RAD6-like domain and regulates Pol η-dependent translesion DNA synthesis.","date":"2011","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/21884979","citation_count":49,"is_preprint":false},{"pmid":"29306013","id":"PMC_29306013","title":"RAD18 promotes the migration and invasion of esophageal squamous cell cancer via the JNK-MMPs pathway.","date":"2018","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/29306013","citation_count":47,"is_preprint":false},{"pmid":"35365623","id":"PMC_35365623","title":"Class I HDAC overexpression promotes temozolomide resistance in glioma cells by regulating RAD18 expression.","date":"2022","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/35365623","citation_count":47,"is_preprint":false},{"pmid":"16923963","id":"PMC_16923963","title":"Role for RAD18 in homologous recombination in DT40 cells.","date":"2006","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/16923963","citation_count":47,"is_preprint":false},{"pmid":"16824193","id":"PMC_16824193","title":"A human DNA polymerase eta complex containing Rad18, Rad6 and Rev1; proteomic analysis and targeting of the complex to the chromatin-bound fraction of cells undergoing replication fork arrest.","date":"2006","source":"Genes to cells : devoted to molecular & cellular mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/16824193","citation_count":47,"is_preprint":false},{"pmid":"15388802","id":"PMC_15388802","title":"The post-replication repair RAD18 and RAD6 genes are involved in the prevention of spontaneous mutations caused by 7,8-dihydro-8-oxoguanine in Saccharomyces cerevisiae.","date":"2004","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/15388802","citation_count":47,"is_preprint":false},{"pmid":"2017370","id":"PMC_2017370","title":"Transcript levels of the Saccharomyces cerevisiae DNA repair gene RAD18 increase in UV irradiated cells and during meiosis but not during the mitotic cell cycle.","date":"1991","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/2017370","citation_count":47,"is_preprint":false},{"pmid":"15507115","id":"PMC_15507115","title":"Rad18/Rad5/Mms2-mediated polyubiquitination of PCNA is implicated in replication completion during replication stress.","date":"2004","source":"Genes to cells : devoted to molecular & cellular mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/15507115","citation_count":42,"is_preprint":false},{"pmid":"1986222","id":"PMC_1986222","title":"The yeast rad18 mutator specifically increases G.C----T.A transversions without reducing correction of G-A or C-T mismatches to G.C pairs.","date":"1991","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/1986222","citation_count":40,"is_preprint":false},{"pmid":"29683380","id":"PMC_29683380","title":"Diverse roles of RAD18 and Y-family DNA polymerases in tumorigenesis.","date":"2018","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/29683380","citation_count":38,"is_preprint":false},{"pmid":"26549024","id":"PMC_26549024","title":"RAD18, WRNIP1 and ATMIN promote ATM signalling in response to replication stress.","date":"2015","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/26549024","citation_count":38,"is_preprint":false},{"pmid":"24958773","id":"PMC_24958773","title":"SIVA1 directs the E3 ubiquitin ligase RAD18 for PCNA monoubiquitination.","date":"2014","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/24958773","citation_count":37,"is_preprint":false},{"pmid":"21549715","id":"PMC_21549715","title":"Symmetry and asymmetry of the RING-RING dimer of Rad18.","date":"2011","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/21549715","citation_count":37,"is_preprint":false},{"pmid":"3073108","id":"PMC_3073108","title":"Potential DNA-binding domains in the RAD18 gene product of Saccharomyces cerevisiae.","date":"1988","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/3073108","citation_count":37,"is_preprint":false},{"pmid":"25417706","id":"PMC_25417706","title":"Rad18 and Rnf8 facilitate homologous recombination by two distinct mechanisms, promoting Rad51 focus formation and suppressing the toxic effect of nonhomologous end joining.","date":"2014","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/25417706","citation_count":36,"is_preprint":false},{"pmid":"8097557","id":"PMC_8097557","title":"The Neurospora uvs-2 gene encodes a protein which has homology to yeast RAD18, with unique zinc finger motifs.","date":"1993","source":"Molecular & general genetics : MGG","url":"https://pubmed.ncbi.nlm.nih.gov/8097557","citation_count":36,"is_preprint":false},{"pmid":"16710452","id":"PMC_16710452","title":"Effect of DNA repair protein Rad18 on viral infection.","date":"2006","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/16710452","citation_count":34,"is_preprint":false},{"pmid":"19029798","id":"PMC_19029798","title":"Cooperation of replication protein A with the ubiquitin ligase Rad18 in DNA damage bypass.","date":"2008","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/19029798","citation_count":33,"is_preprint":false},{"pmid":"24518219","id":"PMC_24518219","title":"RAD18 mediates resistance to ionizing radiation in human glioma cells.","date":"2014","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/24518219","citation_count":32,"is_preprint":false},{"pmid":"21967848","id":"PMC_21967848","title":"Asymmetric nature of two subunits of RAD18, a RING-type ubiquitin ligase E3, in the human RAD6A-RAD18 ternary complex.","date":"2011","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/21967848","citation_count":32,"is_preprint":false},{"pmid":"20967207","id":"PMC_20967207","title":"Convergence of Rad6/Rad18 and Fanconi anemia tumor suppressor pathways upon DNA damage.","date":"2010","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/20967207","citation_count":32,"is_preprint":false},{"pmid":"11013078","id":"PMC_11013078","title":"Characterization of mRAD18Sc, a mouse homolog of the yeast postreplication repair gene RAD18.","date":"2000","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/11013078","citation_count":32,"is_preprint":false},{"pmid":"20971043","id":"PMC_20971043","title":"RAD18 lives a double life: Its implication in DNA double-strand break repair.","date":"2010","source":"DNA repair","url":"https://pubmed.ncbi.nlm.nih.gov/20971043","citation_count":31,"is_preprint":false},{"pmid":"11523791","id":"PMC_11523791","title":"A homologue of the Rad18 postreplication repair gene is required for DNA damage responses throughout the fission yeast cell cycle.","date":"2001","source":"Molecular genetics and genomics : MGG","url":"https://pubmed.ncbi.nlm.nih.gov/11523791","citation_count":31,"is_preprint":false},{"pmid":"30798132","id":"PMC_30798132","title":"High expression of RAD18 in glioma induces radiotherapy resistance via down-regulating P53 expression.","date":"2019","source":"Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie","url":"https://pubmed.ncbi.nlm.nih.gov/30798132","citation_count":30,"is_preprint":false},{"pmid":"17277362","id":"PMC_17277362","title":"Brc1-mediated rescue of Smc5/6 deficiency: requirement for multiple nucleases and a novel Rad18 function.","date":"2007","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/17277362","citation_count":30,"is_preprint":false},{"pmid":"25023518","id":"PMC_25023518","title":"DNA damage-specific deubiquitination regulates Rad18 functions to suppress mutagenesis.","date":"2014","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/25023518","citation_count":29,"is_preprint":false},{"pmid":"22547805","id":"PMC_22547805","title":"Requirement of Rad18 protein for replication through DNA lesions in mouse and human cells.","date":"2012","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/22547805","citation_count":29,"is_preprint":false},{"pmid":"19556710","id":"PMC_19556710","title":"Physical and functional interaction between WRNIP1 and RAD18.","date":"2009","source":"Genes & genetic systems","url":"https://pubmed.ncbi.nlm.nih.gov/19556710","citation_count":28,"is_preprint":false},{"pmid":"23295675","id":"PMC_23295675","title":"Cell cycle stage-specific roles of Rad18 in tolerance and repair of oxidative DNA damage.","date":"2013","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/23295675","citation_count":28,"is_preprint":false},{"pmid":"26212134","id":"PMC_26212134","title":"RAD18 Is a Maternal Limiting Factor Silencing the UV-Dependent DNA Damage Checkpoint in Xenopus Embryos.","date":"2015","source":"Developmental cell","url":"https://pubmed.ncbi.nlm.nih.gov/26212134","citation_count":28,"is_preprint":false},{"pmid":"22145991","id":"PMC_22145991","title":"Elevated expression of Rad18 regulates melanoma cell proliferation.","date":"2012","source":"Pigment cell & melanoma research","url":"https://pubmed.ncbi.nlm.nih.gov/22145991","citation_count":27,"is_preprint":false},{"pmid":"33242956","id":"PMC_33242956","title":"PCNA Monoubiquitination Is Regulated by Diffusion of Rad6/Rad18 Complexes along RPA Filaments.","date":"2020","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/33242956","citation_count":27,"is_preprint":false},{"pmid":"25162118","id":"PMC_25162118","title":"NMR structure of the human Rad18 zinc finger in complex with ubiquitin defines a class of UBZ domains in proteins linked to the DNA damage response.","date":"2014","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/25162118","citation_count":27,"is_preprint":false},{"pmid":"26795561","id":"PMC_26795561","title":"REV1 promotes PCNA monoubiquitylation through interacting with ubiquitylated RAD18.","date":"2016","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/26795561","citation_count":26,"is_preprint":false},{"pmid":"16873544","id":"PMC_16873544","title":"Involvement of Rad18 in somatic hypermutation.","date":"2006","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/16873544","citation_count":26,"is_preprint":false},{"pmid":"20529881","id":"PMC_20529881","title":"Role of the ubiquitin-binding domain of Polη in Rad18-independent translesion DNA synthesis in human cell extracts.","date":"2010","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/20529881","citation_count":26,"is_preprint":false},{"pmid":"16949354","id":"PMC_16949354","title":"Mgs1 and Rad18/Rad5/Mms2 are required for survival of Saccharomyces cerevisiae mutants with novel temperature/cold sensitive alleles of the DNA polymerase delta subunit, Pol31.","date":"2006","source":"DNA repair","url":"https://pubmed.ncbi.nlm.nih.gov/16949354","citation_count":26,"is_preprint":false},{"pmid":"19068231","id":"PMC_19068231","title":"Rad18 is required for long-term maintenance of spermatogenesis in mouse testes.","date":"2008","source":"Mechanisms of development","url":"https://pubmed.ncbi.nlm.nih.gov/19068231","citation_count":26,"is_preprint":false},{"pmid":"2698834","id":"PMC_2698834","title":"The structure and function of RAD6 and RAD18 DNA repair genes of Saccharomyces cerevisiae.","date":"1989","source":"Genome","url":"https://pubmed.ncbi.nlm.nih.gov/2698834","citation_count":24,"is_preprint":false},{"pmid":"23936422","id":"PMC_23936422","title":"Single cell analysis of human RAD18-dependent DNA post-replication repair by alkaline bromodeoxyuridine comet assay.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23936422","citation_count":24,"is_preprint":false},{"pmid":"35459258","id":"PMC_35459258","title":"Genome-wide CRISPR screen identified Rad18 as a determinant of doxorubicin sensitivity in osteosarcoma.","date":"2022","source":"Journal of experimental & clinical cancer research : CR","url":"https://pubmed.ncbi.nlm.nih.gov/35459258","citation_count":24,"is_preprint":false},{"pmid":"7526205","id":"PMC_7526205","title":"Roles for the yeast RAD18 and RAD52 DNA repair genes in UV mutagenesis.","date":"1994","source":"Mutation research","url":"https://pubmed.ncbi.nlm.nih.gov/7526205","citation_count":24,"is_preprint":false},{"pmid":"35413945","id":"PMC_35413945","title":"A positive feedback loop: RAD18-YAP-TGF-β between triple-negative breast cancer and macrophages regulates cancer stemness and progression.","date":"2022","source":"Cell death discovery","url":"https://pubmed.ncbi.nlm.nih.gov/35413945","citation_count":22,"is_preprint":false},{"pmid":"12776193","id":"PMC_12776193","title":"ZNF198 protein, involved in rearrangement in myeloproliferative disease, forms complexes with the DNA repair-associated HHR6A/6B and RAD18 proteins.","date":"2003","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/12776193","citation_count":22,"is_preprint":false},{"pmid":"26871286","id":"PMC_26871286","title":"Rad18 is required for functional interactions between FANCD2, BRCA2, and Rad51 to repair DNA topoisomerase 1-poisons induced lesions and promote fork recovery.","date":"2016","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/26871286","citation_count":22,"is_preprint":false},{"pmid":"1934115","id":"PMC_1934115","title":"Repair of gamma ray-induced S1 nuclease hypersensitive sites in yeast depends on homologous mitotic recombination and a RAD18-dependent function.","date":"1991","source":"Current genetics","url":"https://pubmed.ncbi.nlm.nih.gov/1934115","citation_count":22,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":44063,"output_tokens":9151,"usd":0.134727,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":19360,"output_tokens":7402,"usd":0.140925,"stage2_stop_reason":"end_turn"},"total_usd":0.275652,"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\": 1994,\n      \"finding\": \"Yeast Rad18 forms a specific complex with Rad6 (ubiquitin-conjugating enzyme), and Rad18 binds single-stranded DNA, providing a mechanism for targeting Rad6 ubiquitin-conjugating activity to damage-containing DNA regions. Rad6 has no intrinsic affinity for DNA; the complex with Rad18 confers this targeting.\",\n      \"method\": \"Co-immunoprecipitation, DNA binding assays, dominant-negative overexpression genetics\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal biochemical interaction confirmed by co-IP, DNA binding assays, and dominant-negative genetics; independently reproduced in subsequent studies\",\n      \"pmids\": [\"7926769\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Purified yeast Rad6-Rad18 heterodimer has ubiquitin-conjugating activity, binds single-stranded DNA, and possesses ssDNA-dependent ATPase activity, demonstrating that ubiquitin conjugation is physically coupled to DNA binding and ATPase activities in the same complex.\",\n      \"method\": \"Co-overexpression in yeast, purification to near homogeneity, in vitro ubiquitination assay, ssDNA binding assay, ATPase assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted complex with multiple orthogonal in vitro biochemical activities demonstrated\",\n      \"pmids\": [\"9287349\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"The Rad6-Rad18 interaction is mediated by residues 371–410 near the C-terminus of Rad18 (sufficient for Rad6 binding) and residues 141–149 at the C-terminus and residues 10–22 at the N-terminus of Rad6, defining the dimerization interface between these two proteins.\",\n      \"method\": \"Deletion mutagenesis, yeast two-hybrid, protein interaction assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis mapping with functional interaction readouts, single lab\",\n      \"pmids\": [\"9234711\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Human RAD18 protein interacts with human HHR6A and HHR6B (human Rad6 homologs) through its conserved RING-finger motif; stable complexes were purified from yeast co-expression. Mutation of the RING-finger motif in hRad18 causes sensitivity to UV, MMS, and mitomycin C and defective replication of UV-damaged DNA.\",\n      \"method\": \"Co-expression and purification in yeast, RING-finger mutation analysis in stable human cell transformants, UV/MMS/MMC sensitivity assays, postreplication repair assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — mutagenesis with functional cellular readouts plus biochemical purification, replicated from yeast findings\",\n      \"pmids\": [\"10884424\", \"10908344\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Human Rad18 and Rad6B monoubiquitinate PCNA in vitro. UV irradiation induces Rad18 relocalization in the nucleus and colocalization with PCNA. Rad18 (together with Rad6) is required for PCNA monoubiquitination and for recruitment of DNA polymerase eta (Polη) to UV-induced nuclear foci; Polη interacts preferentially with monoubiquitinated PCNA. Rad18 physically associates with Polη through C-terminal domains of both proteins.\",\n      \"method\": \"In vitro ubiquitination assay with purified proteins, RAD18-knockout cell lines, immunofluorescence focus formation, co-immunoprecipitation, UV irradiation\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of PCNA monoubiquitination, knockout cells with multiple orthogonal assays, replicated across multiple labs\",\n      \"pmids\": [\"15359278\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Rad18-mediated PCNA monoubiquitination regulates the interaction between PCNA and DNA polymerase kappa (Polκ). BPDE-induced PCNA ubiquitination is abolished by siRNA-mediated Rad18 knockdown; a monoubiquitination-resistant PCNA mutant fails to interact with Polκ. Rad18-deficient cells show defective recovery from BPDE-induced S-phase checkpoints. ATR/Chk1 signaling is required upstream of Rad18-mediated PCNA monoubiquitination.\",\n      \"method\": \"siRNA knockdown, Rad18-/- mouse cells, monoubiquitination-deficient PCNA mutant, co-immunoprecipitation, checkpoint kinase activation assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, knockout/knockdown, mutant PCNA, multiple orthogonal methods\",\n      \"pmids\": [\"16611994\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Vertebrate Rad18 suppresses access of non-homologous end joining (NHEJ) to double-strand breaks, thereby facilitating homologous recombination-mediated DSB repair. Deletion of NHEJ in rad18-deficient DT40 cells completely restores HR-mediated DSB repair.\",\n      \"method\": \"Gene disruption in chicken DT40 cells, double mutant analysis (epistasis), camptothecin sensitivity, HR repair assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis with clean knockout cells, double mutant rescue, independently supported in multiple studies\",\n      \"pmids\": [\"17242200\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The SAP domain of human Rad18 (residues 248–282) mediates DNA binding in vitro and is required for Rad18 accumulation at DNA damage sites in vivo and for efficient PCNA monoubiquitination. The C2HC zinc finger domain of Rad18 mediates interaction with ubiquitin (analogous to UBZ/UBM domains), but the SAP domain (not the zinc finger) is responsible for DNA binding.\",\n      \"method\": \"Domain deletion/mutation analysis, in vitro DNA binding assays, in vivo localization (immunofluorescence), PCNA ubiquitination assay, UV-sensitivity complementation\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro biochemical assays plus in vivo mutant analysis, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"17720710\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Human RAD18 complexed with RAD6B preferentially binds forked and ssDNA structures (present at stalled replication forks) via the SAP domain. SAP domain mutants fail to accumulate at DNA damage sites in vivo and do not guide Polη to stalled replication forks, and fail to suppress UV sensitivity of Rad18-knockout cells.\",\n      \"method\": \"In vitro DNA binding assays (forked/ssDNA substrates), SAP domain mutagenesis, immunofluorescence localization, UV sensitivity complementation in Rad18-/- cells\",\n      \"journal\": \"Genes to cells : devoted to molecular & cellular mechanisms\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro DNA binding reconstitution plus in vivo functional rescue with mutagenesis, single lab\",\n      \"pmids\": [\"18363965\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Replication protein A (RPA) physically interacts with Rad18 (in both yeast and mammalian cells) and is required for PCNA ubiquitylation. Purified RPA can recruit Rad18 to ssDNA in vitro. Chromatin association of Rad18 correlates with RPA.\",\n      \"method\": \"Physical interaction (co-IP), in vitro recruitment assay with purified proteins, yeast genetics\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro reconstitution plus co-IP, single lab, two orthogonal methods\",\n      \"pmids\": [\"19029798\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The Rad6-Rad18 ubiquitin ligase complex ubiquitinates the K197 residue of Rad17 (subunit of the 9-1-1 checkpoint clamp), and this monoubiquitination promotes efficient Rad53 phosphorylation and coordinates DNA damage-responsive transcription (a eukaryotic SOS-like response) with checkpoint function.\",\n      \"method\": \"Yeast genetics, ubiquitination assays, Rad53 phosphorylation analysis, transcriptional profiling\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical ubiquitination assay plus genetic epistasis, single lab\",\n      \"pmids\": [\"18485869\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"In S. cerevisiae, PCNA SUMOylation strongly enhances Rad18-mediated PCNA ubiquitylation; Rad18 contains a SUMO-interacting motif (SIM) that mediates this stimulation and also mediates Rad18 auto-SUMOylation, suggesting sumoylated PCNA is the physiological substrate for budding yeast Rad18.\",\n      \"method\": \"Yeast genetics, in vitro ubiquitylation assays with sumoylated PCNA, SIM mutagenesis\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro reconstitution with mutagenesis, single lab\",\n      \"pmids\": [\"23034805\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"RAD18 (via its E3 ligase activity) promotes homologous recombination (HR) repair of DSBs by being recruited to break sites through RNF8-mediated DNA damage signaling and directly interacting with the recombinase RAD51C to facilitate HRR.\",\n      \"method\": \"Co-immunoprecipitation (RAD18-RAD51C interaction), RAD18-knockout cells, HR reporter assays, immunofluorescence, epistasis with RNF8\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct protein interaction (co-IP), knockout cells, multiple functional readouts, independently supported\",\n      \"pmids\": [\"19396164\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"In S. cerevisiae, Rad18 is required for the formation of X-shaped sister chromatid junctions (SCJs) at damaged replication forks through PCNA polyubiquitylation involving Mms2/Ubc13; this template-switch mechanism requires SUMOylated PCNA and is coordinated with Rad51-dependent recombination.\",\n      \"method\": \"Yeast genetics (double mutants), 2D gel electrophoresis to detect SCJs (physical evidence for template switch), epistasis analysis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — physical detection of DNA intermediates plus genetic epistasis, rigorous study in high-impact journal\",\n      \"pmids\": [\"19092928\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PCNA poly-ubiquitylation proceeds by sequential action of two complexes: Rad6-Rad18 initiates monoubiquitylation (requiring PCNA to be loaded on DNA), and Ubc13-Mms2-Rad5 independently elongates the chain stepwise. Chain extension does not strictly require DNA-loaded PCNA.\",\n      \"method\": \"In vitro PCNA ubiquitylation reconstitution with purified components, mutational analysis of ubiquitin attachment sites\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — full in vitro reconstitution with purified components and mechanistic dissection, single lab\",\n      \"pmids\": [\"19851286\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"RAD18 monoubiquitinates K1268 in the KBD domain of 53BP1 in vitro; a K1268R monoubiquitination-resistant 53BP1 mutant is not efficiently retained at chromatin near DSBs. RAD18 associates with 53BP1 and is recruited to DSB sites in a 53BP1-dependent manner specifically during G1 phase, promoting 53BP1-directed DSB repair.\",\n      \"method\": \"In vitro ubiquitination assay, co-immunoprecipitation, immunofluorescence in Rad18-null cells, G1-specific analysis\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro ubiquitination plus cellular co-IP and mutant analysis, single lab\",\n      \"pmids\": [\"19228710\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"RAD18 is phosphorylated by the protein kinase Cdc7 (DDK) on a serine cluster in its Polη-binding motif. DDK-dependent phosphorylation of Rad18 is required for efficient Rad18–Polη association and for redistribution of Polη to sites of replication fork stalling after DNA damage.\",\n      \"method\": \"Kinase assay (Cdc7/DDK phosphorylation of Rad18), phosphorylation site mutagenesis, co-immunoprecipitation, immunofluorescence\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — kinase assay with mutagenesis plus cellular co-IP and localization, single lab\",\n      \"pmids\": [\"21098111\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"RAD18-mediated monoubiquitination of PCNA at Lys164 is required for recruitment of the E3 ligase FANCL to chromatin, and monoubiquitinated PCNA stimulates FANCL-catalyzed FANCD2 and FANCI monoubiquitination, thus activating the Fanconi anemia pathway.\",\n      \"method\": \"RAD18 knockdown/knockout, chromatin fractionation, ubiquitination assays, epistasis with PCNA-K164R mutant\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — knockout/knockdown with chromatin fractionation and ubiquitination assays, mechanistically defined pathway, independently supported\",\n      \"pmids\": [\"20937699\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"RAD18 binds FANCD2 directly and is required for efficient monoubiquitylation and chromatin localization of both FANCD2 and FANCI. RING domain mutation of RAD18 abolishes interaction with FANCD2 and prevents chromatin loading. PCNA ubiquitylation-resistant cells show normal FANCD2 ubiquitylation, suggesting RAD18 contributes to FA pathway independently of PCNA ubiquitination for FANCD2 loading.\",\n      \"method\": \"RAD18-knockout human cells, co-immunoprecipitation (RAD18-FANCD2), chromatin fractionation, RING domain mutagenesis, immunofluorescence\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP and knockout with functional readouts, single lab\",\n      \"pmids\": [\"21355096\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"SNM1A contains a UBZ (ubiquitin-binding zinc finger) domain; RAD18-dependent monoubiquitination of PCNA is required for SNM1A nuclear focus assembly and recruitment to ICL lesions (MMC, UV), defining a RAD18–PCNA(Ub)–SNM1A pathway for ICL resistance.\",\n      \"method\": \"Focus formation assays, RAD18-dependent ubiquitination analysis, UBZ domain mutation, MMC/UV treatment\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RAD18-dependence of SNM1A recruitment established by knockdown with focus formation assay and domain mutagenesis, single lab\",\n      \"pmids\": [\"20385554\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The E2 enzyme Rad6b is intrinsically capable of catalyzing ubiquitin chain formation; this activity is inhibited by its interaction with the R6BD domain of Rad18, which competes with ubiquitin for a noncovalent 'backside' binding site on Rad6, thereby restricting PCNA ubiquitination to monoubiquitination.\",\n      \"method\": \"NMR spectroscopy, X-ray crystallography, in vitro ubiquitination assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — structure determination (NMR + X-ray) combined with in vitro biochemical validation, single rigorous study\",\n      \"pmids\": [\"21422291\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The Rad18 RING domain forms a homodimer; X-ray crystallography reveals it dimerizes through helices adjacent to the RING domains. NMR and mutagenesis show the Rad6b binding site on the RING domain is conserved. The full-length Rad18 homodimer binds only one Rad6b molecule (asymmetric), whereas isolated RING dimer can recruit two Rad6b molecules.\",\n      \"method\": \"X-ray crystallography, NMR spectroscopy, site-directed mutagenesis, binding assays\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure plus NMR and mutagenesis validation, single lab but rigorous methods\",\n      \"pmids\": [\"21549715\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"RAD6A and RAD18 form a ternary complex RAD6A-(RAD18)₂; presence of only one R6BD (RAD6-binding domain) in the RAD18 dimer is sufficient for complex formation and E3 ligase activity. Mutations in both subunits of either RING or SAP domains strongly reduce ligase activity, while inactivation in only one subunit has no effect, demonstrating functional asymmetry.\",\n      \"method\": \"Differential epitope-tagging of RAD18 subunits, mutant complex analysis, in vitro ubiquitination assay\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro biochemical assays with distinct-tagged subunits, single lab\",\n      \"pmids\": [\"21967848\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"NBS1 binds RAD18 after UV irradiation through a C-terminal domain that shares structural and functional similarity with the RAD18-interacting domain of RAD6, and mediates recruitment of RAD18 to DNA damage sites. NBS1 disruption abolishes RAD18-dependent PCNA ubiquitination and Polη focus formation. NBS1 and RAD6 can simultaneously interact with RAD18 homodimers.\",\n      \"method\": \"Co-immunoprecipitation, NBS1-knockout cells, PCNA ubiquitination assays, Polη focus formation, domain mapping\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, knockout cells, multiple functional readouts, structural similarity mapped, single lab\",\n      \"pmids\": [\"21884979\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"DNA polymerase eta (Polη) has a non-catalytic role in recruiting Rad18 to PCNA and promoting PCNA monoubiquitination via its C-terminal domain that binds both Rad18 and PCNA. This function is unique to Polη among Y-family TLS polymerases and is dissociable from its catalytic activity; catalytically-inactive full-length Polη in XPV cells still promotes error-prone TLS polymerase recruitment.\",\n      \"method\": \"Polη domain deletion/mutation analysis, co-immunoprecipitation, PCNA ubiquitination assay in XPV cells, immunofluorescence\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP with domain mutants plus functional cellular assays, single lab\",\n      \"pmids\": [\"23345618\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"SIVA1 constitutively interacts with PCNA via a PIP motif and serves as a molecular bridge between RAD18 and PCNA, targeting RAD18 E3 ligase activity to PCNA. SIVA1 knockdown compromises RAD18-dependent PCNA monoubiquitination and Polη focus formation.\",\n      \"method\": \"Affinity purification of PCNA complex, co-immunoprecipitation, SIVA1 knockdown, PCNA ubiquitination assay, focus formation\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — affinity purification plus functional knockdown with ubiquitination and focus readouts, single lab\",\n      \"pmids\": [\"24958773\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"NMR structure of the human Rad18 C2HC zinc finger (UBZ4 type) in complex with ubiquitin shows it adopts a β1-β2-α fold and binds ubiquitin via the α-helix and β1 strand; this binding mode differs from the Polη UBZ3 domain which uses only the α-helix. This defines two structural classes of UBZ domain with distinct ubiquitin binding interfaces.\",\n      \"method\": \"NMR spectroscopy, chemical shift perturbation mapping, structure determination of Rad18-UBZ4–ubiquitin complex\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structure with binding site mapping, single lab but rigorous structural study\",\n      \"pmids\": [\"25162118\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Monoubiquitination of Rad18 itself prevents its localization to DNA damage sites, inhibits PCNA monoubiquitination, and prevents interaction with SHPRH and HLTF (downstream E3s for error-free bypass). Ubiquitinated Rad18 interacts preferentially with the zinc finger domain of non-ubiquitinated Rad18. Damage-specific deubiquitination of Rad18 (by MMS or H₂O₂ treatment) promotes a switch from Rad18•Ub-Rad18 complexes to Rad18-SHPRH complexes for error-free lesion bypass.\",\n      \"method\": \"Rad18 ubiquitination-resistant mutants, co-immunoprecipitation, immunofluorescence, PCNA ubiquitination assays\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP with domain mutants plus functional cellular readouts, single lab\",\n      \"pmids\": [\"25023518\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"USP7 deubiquitylase directly associates with RAD18 via a consensus USP7-binding motif and stabilizes Rad18 protein levels by disassembling Rad18-dependent poly-ubiquitin chains both in vitro and in vivo. Loss of USP7 destabilizes Rad18, compromises UV-induced PCNA mono-ubiquitylation, and impairs Polη recruitment and DNA damage tolerance.\",\n      \"method\": \"Co-immunoprecipitation, in vitro deubiquitylation assay, USP7 depletion (siRNA/inhibitor), PCNA ubiquitylation assay, Polη focus formation\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro deubiquitylation plus cellular co-IP and functional readouts, single lab\",\n      \"pmids\": [\"25961918\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Rad18 acts as a molecular bridge between Polη and PIAS1 SUMO ligase to promote SUMOylation of Polη at K163, independently of Rad18's E3 ubiquitin ligase activity. This SUMOylation is required for Polη to travel with replication forks during unchallenged S phase and prevents under-replicated DNA and chromosome fragility.\",\n      \"method\": \"SUMOylation assays, Rad18 knockdown/mutant analysis, immunofluorescence (Polη replication fork colocalization), chromosomal fragility assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP bridging interaction plus functional knockdown, single lab, multiple cellular readouts\",\n      \"pmids\": [\"27811911\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RAD18 binds tightly to monoubiquitylated NCP (nucleosome core particle with H2A-K15Ub) through a ubiquitin-binding domain that contacts both ubiquitin and nucleosome surfaces, displacing 53BP1 from these sites. NMR spectroscopy and biochemistry establish this as a distinct ubiquitin recognition mechanism from that of RNF169.\",\n      \"method\": \"NMR spectroscopy, biochemical binding assays with NCP-ubme substrates\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR with biochemical validation, structural and mechanistic dissection of RAD18-nucleosome interaction, single lab\",\n      \"pmids\": [\"28506460\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Human Rad18 protein exists in two major forms (non-ubiquitinated ~75 kDa and monoubiquitinated ~85 kDa) detected by mass spectrometry. Rad18 undergoes autoubiquitination at multiple sites via Rad6 (E2); self-association through the zinc finger domain is required for monoubiquitination. Monoubiquitinated Rad18 is predominantly cytoplasmic while non-ubiquitinated Rad18 is nuclear. Rad18 is also polyubiquitinated and degraded by proteasomes.\",\n      \"method\": \"Western blot, mass spectrometry, in vitro ubiquitination assay, zinc finger mutant (C207F) analysis, subcellular fractionation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — mass spectrometry identification plus in vitro assays and cellular fractionation, single lab\",\n      \"pmids\": [\"15509568\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Physical interaction between WRNIP1 and RAD18: WRNIP1 binds forked and template/primer DNA in an ATP-dependent manner, and directly interacts with RAD18; WRNIP1 interferes with RAD18 binding to forked DNA, while RAD18 enhances WRNIP1 binding to these DNA substrates, suggesting competitive/cooperative targeting at stalled forks.\",\n      \"method\": \"Co-immunoprecipitation, in vitro DNA binding assays with forked DNA substrates, reciprocal interaction analysis\",\n      \"journal\": \"Genes & genetic systems\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus in vitro DNA binding assays, single lab\",\n      \"pmids\": [\"19556710\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"REV1 promotes PCNA monoubiquitylation after UV radiation by interacting with ubiquitylated RAD18, which facilitates the release of non-ubiquitylated RAD18 from ubiquitylated RAD18 trapping, allowing free RAD18 to be recruited to chromatin for TLS function.\",\n      \"method\": \"Co-immunoprecipitation of REV1 with ubiquitylated RAD18, PCNA monoubiquitylation assays, chromatin recruitment assays, UV/HU/MMC treatment\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP showing preference for Ub-RAD18, functional PCNA ubiquitylation assay, single lab\",\n      \"pmids\": [\"26795561\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"An engineered RAD18 variant (e18) stimulates CRISPR-mediated HDR by suppressing localization of the NHEJ-promoting factor 53BP1 to DSBs. Mechanistically, e18 induces HDR by reducing 53BP1 recruitment to break sites.\",\n      \"method\": \"Genome-wide ORF screen in human cells, 53BP1 localization assays (immunofluorescence), HDR reporter assays, RAD18 domain mapping\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional screen with mechanistic follow-up (53BP1 localization suppression), single lab\",\n      \"pmids\": [\"31363085\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Rad6/Rad18 complex is recruited to RPA filaments via Rad18·RPA interactions and translocates randomly along RPA filaments (ATP-independent), promoting productive interactions with PCNA and significantly enhancing PCNA monoubiquitination. This is the first example of ATP-independent protein complex translocation along a protein filament.\",\n      \"method\": \"Kinetic ubiquitination assays, single-molecule FRET microscopy, RPA filament reconstitution\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — single-molecule FRET plus kinetic reconstitution assays, mechanistically rigorous, single lab\",\n      \"pmids\": [\"33242956\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"A Polη-containing complex purified from HeLa cells includes Rad18, Rad6, and Rev1; these components are specifically enriched in chromatin-bound fractions after UV irradiation, S-phase synchronization, or S-phase arrest, indicating that stalled replication forks strengthen interactions among these TLS factors.\",\n      \"method\": \"Affinity purification of Polη complex, mass spectrometry, Western blot, chromatin fractionation\",\n      \"journal\": \"Genes to cells : devoted to molecular & cellular mechanisms\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mass spectrometry-based complex identification with chromatin fractionation validation, single lab\",\n      \"pmids\": [\"16824193\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RAD18 is an E3 RING-finger ubiquitin ligase that forms a heterodimeric complex with the E2 enzyme RAD6 (HHR6A/B); the complex is recruited to stalled replication forks via RAD18's SAP domain binding to forked/ssDNA structures (assisted by RPA, NBS1, PCNA-bound SIVA1, and DDK phosphorylation of RAD18), where it monoubiquitinates PCNA at K164, creating a platform that recruits Y-family translesion synthesis (TLS) polymerases (Polη, Polκ, Polι) through their ubiquitin-binding domains; RAD18 itself is regulated by autoubiquitination (which controls its nuclear/cytoplasmic distribution) and by USP7-mediated deubiquitylation; beyond TLS, RAD18 promotes homologous recombination repair of DSBs by suppressing NHEJ access, facilitating RAD51C-mediated recombination, activating the Fanconi anemia pathway via PCNA-ubiquitination-dependent FANCL recruitment and direct interaction with FANCD2, and acting as a molecular bridge to promote Polη SUMOylation independent of its ubiquitin ligase activity; at DSBs during G1, RAD18 monoubiquitinates 53BP1-K1268 to retain it at chromatin, while at DSBs competing RNF169 and RAD18 displace 53BP1 by binding ubiquitylated NCP with higher affinity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RAD18 is a RING-finger E3 ubiquitin ligase that, in heterodimeric partnership with the E2 conjugating enzyme RAD6 (HHR6A/B), couples ubiquitin transfer to DNA damage to govern DNA damage tolerance and double-strand break repair pathway choice [#0, #3, #4]. The complex is targeted to damaged DNA because RAD18 supplies DNA-binding and recruitment functions that RAD6 lacks: its SAP domain binds forked and single-stranded DNA structures at stalled replication forks and is required for accumulation at damage sites and efficient PCNA monoubiquitination [#7, #8]. Recruitment is reinforced by multiple partners that bridge RAD18 to chromatin and to its substrate — RPA filaments, along which RAD6-RAD18 translocates ATP-independently to engage PCNA [#9, #35], NBS1 acting through a RAD6-like RAD18-interacting domain [#23], the PCNA-bound adaptor SIVA1 [#25], and DDK/Cdc7 phosphorylation that licenses RAD18–Polη association [#16]. Its central catalytic output is monoubiquitination of PCNA at K164, which generates a binding platform recruiting Y-family translesion synthesis polymerases Polη and Polκ through their ubiquitin-binding domains [#4, #5]; the RAD6 backside-binding R6BD domain of RAD18 restricts this reaction to monoubiquitination, with chain elongation for error-free bypass handed off to Ubc13-Mms2-Rad5 [#20, #14]. Beyond translesion synthesis, RAD18 activates the Fanconi anemia pathway both by PCNA-K164-ubiquitination-dependent FANCL recruitment and through direct interaction with FANCD2 [#17, #18], promotes homologous recombination by suppressing NHEJ access to breaks and engaging RAD51C [#6, #12], and modulates 53BP1 — monoubiquitinating 53BP1-K1268 to retain it at G1-phase breaks while also displacing it by high-affinity binding to H2A-K15-ubiquitinated nucleosomes [#15, #30]. RAD18 also acts as a ubiquitin-ligase-independent molecular bridge promoting PIAS1-mediated Polη SUMOylation [#29]. RAD18 activity is self-regulated by autoubiquitination, which partitions it to the cytoplasm and blocks chromatin loading, with USP7-mediated deubiquitylation reversing this to stabilize RAD18 and sustain PCNA monoubiquitination [#31, #27, #28].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Established how a ubiquitin-conjugating enzyme could be directed to damaged DNA, by showing Rad18 physically complexes with Rad6 and supplies the DNA-binding activity Rad6 lacks.\",\n      \"evidence\": \"Co-IP, DNA binding assays, and dominant-negative genetics in yeast\",\n      \"pmids\": [\"7926769\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the in vivo ubiquitination substrate\", \"DNA structure preference within RAD18 not yet mapped to a domain\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Demonstrated that ubiquitin conjugation, ssDNA binding, and ATPase activities are coupled within one reconstituted Rad6-Rad18 complex, and mapped the dimerization interface.\",\n      \"evidence\": \"Purified yeast heterodimer with in vitro ubiquitination, ssDNA binding, ATPase assays; deletion mutagenesis and two-hybrid mapping\",\n      \"pmids\": [\"9287349\", \"9234711\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological substrate of the complex unresolved\", \"Functional role of ssDNA-dependent ATPase activity unclear\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Extended the model to humans, showing hRAD18 binds HHR6A/B through its RING motif and that RING integrity is required for resistance to UV/MMS/MMC and postreplication repair.\",\n      \"evidence\": \"Yeast co-expression purification and RING mutation analysis in human cell transformants with damage sensitivity assays\",\n      \"pmids\": [\"10884424\", \"10908344\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Substrate ubiquitinated in human cells not yet defined\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identified PCNA-K164 monoubiquitination as the key catalytic output linking RAD18 to translesion synthesis, recruiting Polη to damage foci.\",\n      \"evidence\": \"In vitro reconstitution, RAD18-knockout cells, immunofluorescence focus formation, and co-IP after UV\",\n      \"pmids\": [\"15359278\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How RAD18 senses and is recruited to specific lesions not yet defined\", \"Generality beyond Polη to other TLS polymerases untested\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Revealed autoregulation by showing RAD18 autoubiquitinates via RAD6, with monoubiquitinated RAD18 partitioning to the cytoplasm and non-ubiquitinated RAD18 to the nucleus.\",\n      \"evidence\": \"Western blot, mass spectrometry, in vitro ubiquitination, zinc-finger mutant, and subcellular fractionation\",\n      \"pmids\": [\"15509568\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Deubiquitylase reversing autoubiquitination not identified here\", \"Physiological trigger for the localization switch undefined\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Broadened RAD18 function to homologous recombination by demonstrating it suppresses NHEJ access to DSBs to favor HR-mediated repair.\",\n      \"evidence\": \"Gene disruption and double-mutant epistasis in DT40 cells with HR repair and CPT sensitivity assays\",\n      \"pmids\": [\"17242200\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism of NHEJ suppression not defined in this study\", \"Whether E3 activity is required left open\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Generalized the PCNA-ubiquitination platform to Polκ and placed it downstream of ATR/Chk1 checkpoint signaling.\",\n      \"evidence\": \"siRNA and Rad18-/- cells, monoubiquitination-resistant PCNA mutant, co-IP, checkpoint kinase assays; Polη complex purification by MS\",\n      \"pmids\": [\"16611994\", \"16824193\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct link between ATR/Chk1 and RAD18 activation mechanistically undefined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Mapped DNA binding to the SAP domain and ubiquitin binding to the C2HC zinc finger, separating recruitment determinants within RAD18.\",\n      \"evidence\": \"Domain deletion, in vitro DNA binding, in vivo localization, and PCNA ubiquitination assays\",\n      \"pmids\": [\"17720710\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"DNA structure preference of the SAP domain not yet resolved\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Defined the structural specificity of recruitment, showing RAD18-RAD6B preferentially binds forked/ssDNA at stalled forks via the SAP domain, and identified RPA as a recruiter required for PCNA ubiquitylation.\",\n      \"evidence\": \"In vitro DNA binding with forked/ssDNA substrates, SAP mutagenesis, rescue assays; co-IP and in vitro RPA recruitment\",\n      \"pmids\": [\"18363965\", \"19029798\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"RPA-RAD18 interaction interface not mapped\", \"Single-lab evidence for RPA recruitment\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Expanded RAD6-RAD18 substrates beyond PCNA, showing Rad17 K197 monoubiquitination coordinates checkpoint signaling, and that PCNA SUMOylation stimulates Rad18 via its SIM in yeast.\",\n      \"evidence\": \"Yeast genetics, ubiquitination assays, Rad53 phosphorylation, transcriptional profiling; in vitro ubiquitylation with sumoylated PCNA and SIM mutagenesis\",\n      \"pmids\": [\"18485869\", \"23034805\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Conservation of Rad17 ubiquitination in mammals not tested\", \"Whether human RAD18 has an equivalent SIM-dependent stimulation untested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Connected RAD18 to RNF8-dependent DSB signaling and direct RAD51C engagement, and established its role in template-switch sister chromatid junction formation through PCNA polyubiquitylation.\",\n      \"evidence\": \"Co-IP, knockout cells, HR reporters, epistasis with RNF8; 2D gel detection of sister chromatid junctions and in vitro reconstitution of sequential PCNA poly-ubiquitylation\",\n      \"pmids\": [\"19396164\", \"19092928\", \"19851286\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How RAD18 is partitioned between TLS and template-switch outcomes unresolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identified WRNIP1 as a fork-associated partner that reciprocally modulates RAD18 binding to forked DNA, implicating cooperative/competitive targeting at stalled forks.\",\n      \"evidence\": \"Co-IP and in vitro forked-DNA binding assays\",\n      \"pmids\": [\"19556710\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence in cells not established\", \"Single-lab biochemistry\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Demonstrated that RAD18 monoubiquitinates 53BP1-K1268 to retain it at chromatin near DSBs specifically during G1 phase.\",\n      \"evidence\": \"In vitro ubiquitination, co-IP, immunofluorescence in Rad18-null cells with K1268R mutant\",\n      \"pmids\": [\"19228710\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Reconciliation with later 53BP1-displacement role not addressed here\", \"Single-lab evidence\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Established RAD18 as an upstream activator of the Fanconi anemia pathway through both PCNA-K164-dependent FANCL recruitment and direct FANCD2 binding.\",\n      \"evidence\": \"Knockout/knockdown, chromatin fractionation, ubiquitination assays, PCNA-K164R epistasis, RING mutagenesis, RAD18-FANCD2 co-IP\",\n      \"pmids\": [\"20937699\", \"21355096\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of PCNA-dependent vs PCNA-independent FANCD2 loading not fully resolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Showed DDK/Cdc7 phosphorylates RAD18 in its Polη-binding motif to promote RAD18-Polη association and Polη redistribution after damage, and defined a RAD18-PCNA(Ub)-SNM1A pathway for ICL resistance.\",\n      \"evidence\": \"Kinase assays with phosphosite mutagenesis, co-IP, immunofluorescence; SNM1A UBZ mutation and focus formation under MMC/UV\",\n      \"pmids\": [\"21098111\", \"20385554\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo importance of DDK site phosphorylation across damage types incompletely defined\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Solved the structural and mechanistic basis for restricting RAD6 to PCNA monoubiquitination and revealed the asymmetric RAD18 homodimer architecture.\",\n      \"evidence\": \"X-ray crystallography, NMR, in vitro ubiquitination; differential subunit tagging and mutant complex analysis\",\n      \"pmids\": [\"21422291\", \"21549715\", \"21967848\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the asymmetric dimer engages substrates in vivo not directly visualized\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identified NBS1 as a recruiter of RAD18 to UV damage via a RAD6-like interaction domain, required for PCNA ubiquitination and Polη foci.\",\n      \"evidence\": \"Co-IP, NBS1-knockout cells, PCNA ubiquitination and Polη focus assays, domain mapping\",\n      \"pmids\": [\"21884979\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Integration of NBS1, RPA, and SAP-domain recruitment routes not unified\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Revealed a non-catalytic, feed-forward role for Polη in recruiting RAD18 to PCNA and promoting PCNA monoubiquitination, unique among Y-family polymerases.\",\n      \"evidence\": \"Polη domain mutants, co-IP, PCNA ubiquitination in XPV cells, immunofluorescence\",\n      \"pmids\": [\"23345618\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of the Polη-RAD18-PCNA bridge not determined\", \"Single-lab evidence\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identified SIVA1 as a constitutive PCNA-bound bridge targeting RAD18 ligase activity to PCNA, and structurally defined two UBZ classes distinguishing RAD18 from Polη ubiquitin recognition.\",\n      \"evidence\": \"Affinity purification, co-IP, SIVA1 knockdown with ubiquitination/focus assays; NMR structure of RAD18-UBZ4-ubiquitin complex\",\n      \"pmids\": [\"24958773\", \"25162118\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Hierarchy among SIVA1, RPA, NBS1 recruitment routes undefined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined autoubiquitination as a negative switch: Ub-RAD18 binds the zinc finger of non-ubiquitinated RAD18 to block damage-site loading, and deubiquitination switches RAD18 toward SHPRH/HLTF for error-free bypass.\",\n      \"evidence\": \"Ubiquitination-resistant mutants, co-IP, immunofluorescence, PCNA ubiquitination assays\",\n      \"pmids\": [\"25023518\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of the deubiquitylase not addressed in this study\", \"Single-lab evidence\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identified USP7 as the deubiquitylase that stabilizes RAD18 by disassembling its poly-ubiquitin chains, sustaining PCNA monoubiquitination and Polη recruitment.\",\n      \"evidence\": \"Co-IP, in vitro deubiquitylation, USP7 depletion/inhibition with PCNA ubiquitylation and Polη focus assays\",\n      \"pmids\": [\"25961918\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether USP7 also reverses the inhibitory monoubiquitination of RAD18 not fully resolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showed RAD18 bridges Polη to PIAS1 to promote Polη SUMOylation at K163 independent of RAD18 ligase activity, enabling Polη to travel with unchallenged replication forks.\",\n      \"evidence\": \"SUMOylation assays, RAD18 knockdown/mutants, Polη fork colocalization and chromosome fragility assays\",\n      \"pmids\": [\"27811911\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of the RAD18-Polη-PIAS1 bridge undefined\", \"Single-lab evidence\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showed REV1 facilitates release of free RAD18 from inhibitory Ub-RAD18 complexes, relieving autoubiquitination-based trapping to permit chromatin recruitment for TLS.\",\n      \"evidence\": \"Co-IP of REV1 with ubiquitylated RAD18, PCNA monoubiquitylation and chromatin recruitment assays\",\n      \"pmids\": [\"26795561\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Quantitative contribution relative to USP7-mediated control unknown\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Resolved a 53BP1-displacement mechanism, showing RAD18 binds H2A-K15-ubiquitinated nucleosomes via a domain contacting both ubiquitin and nucleosome surfaces, distinct from RNF169.\",\n      \"evidence\": \"NMR spectroscopy and biochemical binding assays with NCP-ubme substrates\",\n      \"pmids\": [\"28506460\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Reconciliation with RAD18-mediated 53BP1 retention not unified mechanistically\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrated translational utility by showing an engineered RAD18 variant stimulates CRISPR HDR by reducing 53BP1 recruitment to breaks.\",\n      \"evidence\": \"Genome-wide ORF screen, 53BP1 localization and HDR reporter assays, domain mapping\",\n      \"pmids\": [\"31363085\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether the engineered variant reflects a native RAD18 activity unclear\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Provided a kinetic mechanism for fork targeting, showing RAD6-RAD18 translocates ATP-independently along RPA filaments to find PCNA and enhance monoubiquitination.\",\n      \"evidence\": \"Single-molecule FRET, kinetic ubiquitination assays, RPA filament reconstitution\",\n      \"pmids\": [\"33242956\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How filament translocation integrates with SAP-domain DNA binding in vivo not addressed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How RAD18 integrates its multiple, partly antagonistic recruitment routes and outputs — TLS versus template switch, 53BP1 retention versus displacement, ubiquitin-ligase-dependent versus -independent SUMO bridging — into a coherent, pathway-selective response remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model for choosing between competing RAD18 outputs\", \"Spatiotemporal regulation across cell-cycle phases incompletely defined\", \"No structure of full-length RAD18 engaging substrate on chromatin\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [0, 3, 4, 20]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [4, 5, 15, 17]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [0, 7, 8]},\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [30]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [25, 29]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [4, 31]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [31]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [8, 17, 30]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [6, 12, 17]},\n      {\"term_id\": \"R-HSA-69306\", \"supporting_discovery_ids\": [4, 5, 14]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 4, 20]}\n    ],\n    \"complexes\": [\"RAD6-RAD18 (E2-E3) heterodimer\"],\n    \"partners\": [\"RAD6 (HHR6A/HHR6B)\", \"PCNA\", \"POLH (Polη)\", \"RPA\", \"NBS1\", \"FANCD2\", \"RAD51C\", \"USP7\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}