{"gene":"RNF168","run_date":"2026-06-10T06:43:37","timeline":{"discoveries":[{"year":2009,"finding":"RNF168 is a chromatin-associated RING finger E3 ubiquitin ligase that binds ubiquitin via MIU domains, assembles at DSBs in an RNF8-dependent manner, and amplifies K63-linked ubiquitin conjugates on H2A and H2AX to levels required for retention of 53BP1 and BRCA1 at damage sites.","method":"Co-IP, ubiquitin-binding assays, RNAi knockdown, immunofluorescence at DSB foci, in vivo and in vitro ubiquitylation assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Co-IP, in vitro ligase assay, RNAi, live-cell imaging), replicated across labs","pmids":["19203579"],"is_preprint":false},{"year":2009,"finding":"RNF168 contains two MIU (motif interacting with ubiquitin) domains whose inactivation impairs ubiquitin binding in vitro and reduces chromatin association in vivo; RNF168 ubiquitylates H2A and H2AX (but not H2B) forming K63-linked polyubiquitin chains in vitro and in vivo.","method":"In vitro ubiquitin-binding assay, in vitro/in vivo ubiquitylation assay, mutagenesis of MIU domains, immunofluorescence","journal":"BMC molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro ubiquitylation assay with mutagenesis plus in vivo validation, single lab but multiple orthogonal methods","pmids":["19500350"],"is_preprint":false},{"year":2012,"finding":"RNF168 (not RNF8) catalyzes monoubiquitination of nucleosomal H2A/H2AX specifically at K13-15; RNF8 is inactive toward nucleosomal H2A. A charged residue in the RNF168 RING domain determines nucleosomal substrate recognition. K63-linked ubiquitin chains are conjugated on top of RNF168-dependent K13-15 monoubiquitination, not K118-119.","method":"In vitro nucleosomal ubiquitylation assay, structure-based mutagenesis of RING domains, mass spectrometry to map ubiquitylation sites","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution with nucleosomes in vitro, mutagenesis, MS site mapping, replicated by independent groups","pmids":["22980979"],"is_preprint":false},{"year":2012,"finding":"RNF168 ubiquitylates JMJD2A/KDM4A, targeting it for proteasomal degradation; this removes a competitor of 53BP1 for dimethylated H4K20, thereby allowing 53BP1 recruitment to DNA damage sites.","method":"In vivo ubiquitylation assay, co-IP, RNAi knockdown epistasis, immunofluorescence at DSB foci","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, in vivo ubiquitylation, epistasis via double knockdown, single lab","pmids":["22373579"],"is_preprint":false},{"year":2012,"finding":"RNF168 ubiquitylates histone H2A at a novel N-terminal 'bidentate' site comprising K13 and K15; inactivating both N-terminal (K13/K15) and C-terminal (K118/K119) sites is required to fully abolish damage-induced ubiquitination, indicating these are unique, non-redundant acceptors.","method":"Mutagenesis of histone lysine residues, in vivo ubiquitylation assay, immunofluorescence","journal":"Cell cycle","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis combined with in vivo ubiquitylation assay, consistent with parallel Cell paper (PMID:22980979)","pmids":["22713238"],"is_preprint":false},{"year":2012,"finding":"SMARCA5/SNF2H is recruited to DSBs in a PARP1-dependent manner, interacts with RNF168 in a DNA damage- and PARP-dependent manner, and promotes RNF168 accumulation at DSBs; RNF168 itself becomes poly(ADP-ribosyl)ated after DNA damage.","method":"Co-IP, immunofluorescence, RNAi knockdown, laser micro-irradiation","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP and RNAi with functional readout, single lab, multiple supporting experiments","pmids":["23264744"],"is_preprint":false},{"year":2013,"finding":"RNF168 mediates K63-linked ubiquitylation of 53BP1, which is required for the initial recruitment of 53BP1 to DSBs and for its functions in DNA repair and checkpoint activation.","method":"In vivo ubiquitylation assay, Co-IP, K63-specific ubiquitin mutants, immunofluorescence, checkpoint assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo ubiquitylation with chain-specificity mutants, functional readouts, single lab","pmids":["24324146"],"is_preprint":false},{"year":2013,"finding":"USP44 counteracts RNF8/RNF168-mediated ubiquitylation of H2A and is specifically recruited to RNF168-generated ubiquitylation products at DSBs, acting as a negative regulator at the level of RNF168 accrual.","method":"DUB overexpression screen, H2A deubiquitylation assay, immunofluorescence, RNAi","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional screen plus in vivo H2A deubiquitylation assay, single lab","pmids":["23615962"],"is_preprint":false},{"year":2013,"finding":"USP3 removes ubiquitin at K13 and K15 of H2A/γH2AX (RNF168 target sites) as well as K118/K119 of H2AX in response to DNA damage, counteracting RNF168-mediated ubiquitination.","method":"In vitro deubiquitylation assay, co-IP, immunofluorescence, ectopic expression experiments","journal":"Cell cycle","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro DUB assay with site-specific readout, in vivo validation, single lab","pmids":["24196443"],"is_preprint":false},{"year":2013,"finding":"RNF168 forms a functional complex with RAD6A/RAD6B E2 enzymes; this RNF168-RAD6 complex ubiquitinates histone H1.2 in vitro and regulates DNA damage-induced H1.2 ubiquitination in vivo.","method":"E2 RNAi screen, Co-IP, in vitro ubiquitylation assay, immunofluorescence","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro ubiquitylation reconstitution plus in vivo co-IP, single lab","pmids":["23525009"],"is_preprint":false},{"year":2014,"finding":"The nucleosome acidic patch is required for RNF168-dependent H2A/H2AX ubiquitination at K13/15 both in vitro and in vivo; H2A/H2B dimers and nucleosomes actively stimulate E3-mediated discharge of ubiquitin from E2, redirecting the reaction toward the target lysines.","method":"In vitro ubiquitylation assay with acidic-patch mutant nucleosomes, viral LANA peptide perturbation in vivo, fluorescence-based E2~Ub discharge assay","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — reconstituted in vitro with defined nucleosome substrates and mechanistic discharge assay, single lab with multiple orthogonal methods","pmids":["24518117"],"is_preprint":false},{"year":2014,"finding":"The nucleosome acidic patch is required for both RNF168-dependent H2AX ubiquitination and DDR factor (53BP1, BRCA1) recruitment in vivo; perturbation of the acidic patch by the LANA viral peptide phenocopies RNF168 loss.","method":"In vitro ubiquitylation assay, viral LANA peptide expression, RNAi, immunofluorescence","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro plus in vivo assays, consistent with PMID:24518117, single lab","pmids":["24603765"],"is_preprint":false},{"year":2014,"finding":"RNF168 contains a novel UBD designated UMI (UIM- and MIU-related UBD); the UMI binds ubiquitin via two leucine residues and is required together with MIU domains for proper RNF168 localization and H2A ubiquitination.","method":"Mutagenesis, ubiquitin-binding assays, immunofluorescence, in vivo ubiquitylation assay","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis with in vitro binding and in vivo functional readouts, single lab","pmids":["21041483"],"is_preprint":false},{"year":2014,"finding":"RNF168 mediates NEDD8 conjugation (neddylation) to H2A and is itself neddylated; neddylation of RNF168 is required for its interaction with E2 enzyme Ubc13 and its ubiquitin ligase activity. H2A neddylation antagonizes H2A ubiquitylation.","method":"In vivo neddylation assay, Co-IP, mutagenesis, immunofluorescence","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with E2 interaction readout, in vivo neddylation assay, single lab","pmids":["24634510"],"is_preprint":false},{"year":2014,"finding":"RNF168 interacts with and ubiquitylates topoisomerase IIα (TOP2α), regulating its decatenation activity and chromatin association; USP10 counteracts this by deubiquitylating TOP2α.","method":"Co-IP, in vivo ubiquitylation assay, decatenation assay, RNAi","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus functional decatenation assay, single lab, multiple orthogonal methods","pmids":["27558965"],"is_preprint":false},{"year":2015,"finding":"RNF168 promotes K27-linked (noncanonical) ubiquitin chain formation both in vitro and in vivo; K27-ubiquitin on chromatin is the major ubiquitin mark upon DNA damage and is directly recognized by 53BP1, Rap80, RNF168, and RNF169.","method":"In vitro ubiquitylation assay with K27R ubiquitin mutants, mass spectrometry chain-linkage analysis, immunofluorescence with ubiquitin mutants in cells","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro assay plus MS linkage identification plus in vivo mutant rescue, single lab","pmids":["25578731"],"is_preprint":false},{"year":2015,"finding":"USP7 deubiquitinase physically binds RNF168, stabilizes it against DNA damage-induced degradation, and its deubiquitylase activity toward RNF168 is required to maintain H2A ubiquitination and downstream BRCA1/53BP1 foci formation.","method":"Co-IP (in vitro and in vivo), in vivo ubiquitylation assay, overexpression rescue experiments, RNAi","journal":"Cell cycle","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, in vivo ubiquitylation, functional rescue, single lab","pmids":["25894431"],"is_preprint":false},{"year":2015,"finding":"LSD1 is recruited to DSBs in an RNF168-dependent manner and interacts directly with RNF168 and 53BP1; RNF168-dependent 53BP1 ubiquitination requires CK2-mediated phosphorylation of LSD1 at S131/S137, which promotes LSD1-RNF168 interaction.","method":"Co-IP, immunofluorescence, phosphorylation assay (CK2/WIP1), mutagenesis","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with phosphorylation mutants and functional readouts, single lab","pmids":["25999347"],"is_preprint":false},{"year":2015,"finding":"RNF168 partially localizes to PML nuclear bodies via its UMI/MIU1 ubiquitin-interacting region; RNF168 binds hybrid SUMO2-K63 ubiquitin chains preferentially over K63-ubiquitin chains alone (confirmed in vitro); RNF168 overexpression increases ubiquitylation and SUMO2 modification of PML.","method":"shRNA screen, in vitro ubiquitin/SUMO chain binding assay, Co-IP, immunofluorescence","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro binding assay distinguishing chain types, in vivo Co-IP, single lab","pmids":["26675234"],"is_preprint":false},{"year":2016,"finding":"RNF168 interacts with FOXM1 and mediates its K48-linked polyubiquitination and proteasomal degradation in response to epirubicin; SUMOylation of FOXM1 is required for RNF168 recruitment to FOXM1; RNF8 recruits RNF168 to this substrate.","method":"Co-IP, in vivo ubiquitylation assay, cycloheximide chase, SUMO-defective mutant analysis, gene promoter-reporter assay","journal":"Oncogenesis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, in vivo ubiquitylation with chain-type specificity, functional rescue, single lab","pmids":["27526106"],"is_preprint":false},{"year":2017,"finding":"RNF168 directly interacts with PALB2 via a newly identified PALB2-interacting domain (PID) in RNF168 and the WD40 domain in PALB2; this interaction links H2A ubiquitylation to PALB2-dependent homologous recombination at DSBs in S/G2 cells.","method":"Co-IP, pull-down, mutagenesis of PID domain, HR assay, immunofluorescence","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP with domain mapping, domain mutagenesis, functional HR assay, multiple orthogonal approaches","pmids":["28240985"],"is_preprint":false},{"year":2017,"finding":"RNF169 (RNF168 paralog) binds ubiquitylated H2A-K13/15 on the nucleosome via a three-pronged mechanism involving a canonical ubiquitin-binding helix and two arginine-rich motifs contacting the nucleosome acidic patch; this high-affinity binding displaces 53BP1 from ubiquitylated chromatin.","method":"Methyl-TROSY NMR, molecular dynamics simulations, cryo-EM validation, biochemical binding assays","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR structure with cryo-EM validation and biochemical assays, multiple orthogonal methods","pmids":["28406400"],"is_preprint":false},{"year":2017,"finding":"53BP1 binds RNF168-mediated mono-ubiquitylated H2A-K15 in NCP dimethylated at H4K20; RNF169 stabilizes a pre-existing ubiquitin orientation on the nucleosome via a conformational selection mechanism to outcompete 53BP1; RAD18 binds tightly to ubiquitylated NCP through a domain contacting both ubiquitin and nucleosome surfaces accessed by 53BP1.","method":"NMR spectroscopy, biochemical binding assays, mutagenesis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR structure with biochemical validation and mechanistic dissection, single lab with multiple orthogonal methods","pmids":["28506460"],"is_preprint":false},{"year":2017,"finding":"HUWE1-mediated histone H1 ubiquitylation at multiple lysines is required upstream for RNF168 recruitment and 53BP1 assembly at DSBs; HUWE1 depletion reduces RNF168 foci without affecting MDC1 (upstream of H1 ubiquitylation).","method":"Quantitative di-Gly proteomics, RNAi, immunofluorescence at DSB foci","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteomics site identification plus RNAi epistasis with defined pathway placement, single lab","pmids":["29127375"],"is_preprint":false},{"year":2018,"finding":"mTORC1-S6K1 phosphorylates RNF168 at Ser60, inhibiting its E3 ligase activity and accelerating its proteasomal degradation; a phospho-deficient S60A mutant rescues DNA damage repair defects caused by LKB1 loss.","method":"In vitro kinase assay, phospho-specific antibody, co-IP, proteasome assay, mutagenesis, mouse tumor model","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay with site-specific mutagenesis, in vivo rescue, mouse model, multiple orthogonal methods","pmids":["29403037"],"is_preprint":false},{"year":2018,"finding":"L3MBTL2 is ubiquitylated by RNF8 and the resulting ubiquitylated L3MBTL2 directly recruits RNF168 to DNA damage sites, providing the mechanistic link between RNF8 and RNF168 in sequential DSB signaling.","method":"Co-IP, in vivo ubiquitylation assay, immunofluorescence, RNAi epistasis","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP, in vivo ubiquitylation, epistasis, replicated across multiple experiments in the study","pmids":["29581593"],"is_preprint":false},{"year":2018,"finding":"Crystal structures of RNF168 UDM1 and UDM2 bound to K63-linked diubiquitin reveal that both modules fold as single α-helices that simultaneously contact distal and proximal ubiquitin moieties, conferring K63-chain specificity; UDM2 interaction with ubiquitylated targets primarily drives RNF168 recruitment to DSBs.","method":"X-ray crystallography, biochemical binding assays, mutagenesis, immunofluorescence in U2OS cells","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structures with mutagenesis and in vivo functional validation, single lab with multiple orthogonal methods","pmids":["29330428"],"is_preprint":false},{"year":2018,"finding":"RNF168 ubiquitinates PARP1 via K48-linked chains on multiple lysines, accelerating PARP1 degradation in the presence of PAR chains; PAR-binding by RNF168 is required for this activity and for regulating HR/NHEJ balance.","method":"Mass spectrometry (ubiquitination site mapping), in vivo ubiquitylation assay, Co-IP, comet assay, HR/NHEJ reporter assays","journal":"Molecules and cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS-based site mapping plus in vivo ubiquitylation and functional assays, single lab","pmids":["30037213"],"is_preprint":false},{"year":2018,"finding":"RNF126 directly interacts with RNF168 and ubiquitinates it; RNF126 overexpression diminishes H2AX ubiquitination and downstream 53BP1/RAP80 foci in a catalytic activity-dependent manner, negatively regulating RNF168 function.","method":"Co-IP, in vivo ubiquitylation assay, immunofluorescence, HR reporter assay, catalytic mutant analysis","journal":"Genomics, proteomics & bioinformatics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, in vivo ubiquitylation, catalytic mutant, functional readout, single lab","pmids":["30529286"],"is_preprint":false},{"year":2019,"finding":"RNF168 directly ubiquitylates DHX9 helicase to facilitate its recruitment to R-loop-prone genomic loci; loss of RNF168 impairs DHX9 recruitment and R-loop resolution, leading to DSBs in BRCA1/2-mutant cells.","method":"Co-IP (interactome assay), in vivo ubiquitylation assay, immunofluorescence, R-loop detection (S9.6 antibody), genetic epistasis","journal":"The Journal of clinical investigation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus in vivo ubiquitylation plus functional recruitment assay, single lab","pmids":["33529165"],"is_preprint":false},{"year":2019,"finding":"RNF168 acts redundantly with BRCA1 to load PALB2 onto damaged DNA; loss of RNF168 negates the synthetic rescue of BRCA1 deficiency by 53BP1 deletion, placing RNF168 in a pathway parallel to BRCA1 for RAD51 loading.","method":"Mouse genetics (epistasis), immunofluorescence for RAD51/PALB2 foci, PARP inhibitor sensitivity assay, forced PALB2 targeting rescue","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis in mice plus cellular functional assays, multiple orthogonal methods","pmids":["30704900"],"is_preprint":false},{"year":2019,"finding":"RNF168-generated mUb-H2A recruits BARD1 through a BRCT domain ubiquitin-dependent recruitment motif (BUDR); BARD1-BRCA1 then accumulate PALB2-RAD51 at DSBs via the BRCA1 coiled-coil domain–PALB2 interaction.","method":"Co-IP, mouse genetics (Brca1CC mutant epistasis), immunofluorescence for PALB2/RAD51 foci","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — mouse epistasis combined with Co-IP and defined domain mapping, multiple orthogonal methods","pmids":["34408138"],"is_preprint":false},{"year":2019,"finding":"HPV E7 oncoprotein directly binds a regulatory domain of RNF168 without affecting its enzymatic activity, subverting RNF168 function at DSBs; RNF168 is required for viral genome amplification in differentiated keratinocytes.","method":"Co-IP (direct binding), immunofluorescence, RNAi knockdown, viral genome amplification assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct Co-IP plus functional viral assay, single lab","pmids":["31501315"],"is_preprint":false},{"year":2019,"finding":"PRMT5 sustains RNF168 expression; RNF168 and SMURF2 serve as stabilizer and destabilizer of H2AX, respectively, through dynamic interactions with H2AX; loss of PRMT5 (in MTAP-deficient cells) attenuates RNF168, leading to H2AX destabilization by SMURF2.","method":"Co-IP, in vivo ubiquitylation assay, RNAi, immunoblot","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP with functional outcome in multiple cell types, single lab","pmids":["31533041"],"is_preprint":false},{"year":2019,"finding":"NMR and biochemical studies show RNF168 binds the nucleosome acidic patch and directs the E2 enzyme UBC13 toward K13/15; the structural model defines the basis for site specificity.","method":"NMR spectroscopy, crosslinking mass spectrometry, mutagenesis, data-driven structural modelling","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR with XL-MS and mutagenesis providing structural mechanism, single lab with multiple orthogonal methods","pmids":["30988309"],"is_preprint":false},{"year":2014,"finding":"RNF168 and its cognate E2 UBC13 do not stably associate in vitro or in vivo, in contrast to the RNF8-UBC13 interaction; crystal structure of the RNF168 RING domain reveals differences at the UBC13-binding interface compared to other UBC13-binding E3s; RNF8 and RNF168 RING domains are not functionally interchangeable.","method":"X-ray crystallography, in vitro and in vivo Co-IP, domain-swap mutagenesis","journal":"Cell cycle","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with in vitro and in vivo binding assays confirming structural prediction, single lab","pmids":["23255131"],"is_preprint":false},{"year":2018,"finding":"USP14 deubiquitinase directly interacts with RNF168 via RNF168's MIU1 domain; USP14 activity negatively regulates RNF168 protein levels and RNF168-dependent H2A ubiquitination and 53BP1 recruitment; USP14 is itself a substrate of autophagy via SQSTM1.","method":"Co-IP, immunofluorescence, DUB activity assay, RNAi, domain mapping (MIU1)","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct Co-IP with domain mapping plus functional rescue, single lab","pmids":["29995557"],"is_preprint":false},{"year":2020,"finding":"RNF168 ubiquitinates H2A variants H2AZ and macroH2A1/2 at their divergent N-terminal tail lysines; the positively charged alpha1-extension helix of H2A variants and the RNF168 UMI acidic residues are essential for this reaction; a bipartite electrostatic interaction directs RNF168 orientation on the nucleosome.","method":"In vitro ubiquitylation assay, mutagenesis of nucleosome acidic patch and alpha1-extension helix, immunofluorescence","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with mutagenesis, in vivo validation of foci formation, single lab","pmids":["32424115"],"is_preprint":false},{"year":2021,"finding":"RNF8-ubiquitinated KMT5A is recruited to DSBs and binds RNF168; KMT5A promotes RNF168 catalytic activity toward H2A via its H2A acidic-patch interacting residues R188/R189, linking H4K20 monomethylation to H2A ubiquitination.","method":"In vitro ubiquitylation assay, Co-IP, mutagenesis (R188/R189), ChIP, immunofluorescence","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro ubiquitylation plus Co-IP with domain mapping, single lab","pmids":["33710666"],"is_preprint":false},{"year":2021,"finding":"RNF168 is required for SLX4/FANCP recruitment to interstrand crosslink damage sites; RNF168 is epistatic with SLX4 in promoting mitomycin C tolerance; RNF168-generated K63-linked ubiquitin chains are recognized by the tandem UBZ4 domains of SLX4.","method":"siRNA screen with GFP-SLX4, immunofluorescence, genetic epistasis (survival assays), laser-induced ICL tracks","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA screen confirmed by epistasis and localization assays, single lab","pmids":["34706224"],"is_preprint":false},{"year":2021,"finding":"RNF168 facilitates ubiquitin signaling in RNF8/RNF168-dependent pathways that both prevent and promote DNA end resection in G0/G1 lymphocytes; combined deficiency of XLF and RNF168 leads to diminished NHEJ; in 53BP1-deficient cells, loss of RNF168 diminishes resection.","method":"Genetic knockouts in lymphocytes, NHEJ reporter assays, end-resection assays","journal":"DNA repair","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with functional NHEJ and resection assays, single lab","pmids":["34481157"],"is_preprint":false},{"year":2023,"finding":"SUMOylated RNF168 undergoes liquid-liquid phase separation (LLPS), restricting its recruitment to DNA damage sites and reducing H2A ubiquitination; SENP1 deSUMOylates RNF168, preventing LLPS and promoting RNF168 activity and NHEJ repair.","method":"In vitro LLPS assay, SUMOylation assay, immunofluorescence, NHEJ reporter, SENP1 knockdown/overexpression","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro LLPS reconstitution plus in vivo functional assays, single lab","pmids":["37350666"],"is_preprint":false},{"year":2023,"finding":"HDAC6 interacts with H2A/H2A.X in unstressed cells to prevent RNF168 access; upon DSBs, RNF168 ubiquitinates HDAC6 at K116 leading to its proteasomal degradation and allowing RNF168-H2A/H2A.X interaction and subsequent H2A ubiquitination.","method":"Co-IP, in vivo ubiquitylation assay, immunofluorescence, mutagenesis (K116)","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with site-specific ubiquitylation mapping and functional readouts, single lab","pmids":["37503842"],"is_preprint":false},{"year":2024,"finding":"Cryo-EM and NMR structures reveal the full reaction cycle of RNF168 modifying the nucleosome: RNF168 engages the nucleosome via a canonical ubiquitin-binding domain that contacts both ubiquitin and the nucleosome surface, clarifying how ubiquitin recognition drives a signal amplification loop for site-specific H2A K13/15 ubiquitination.","method":"Cryo-EM, NMR spectroscopy, in vitro ubiquitylation assay, mutagenesis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structure with NMR and functional assays, multiple orthogonal methods in single study","pmids":["38242129"],"is_preprint":false},{"year":2024,"finding":"Cryo-EM structures of RNF168-UbcH5c~Ub-nucleosome complexes captured during H2A K13 and K15 monoubiquitination reveal a 'helix-anchoring' mode for monomeric RNF168 on the nucleosome, distinct from the 'compass-binding' mode of dimeric E3 ligases; both K13 and K15 can be independently monoubiquitinated (adjacent dual monoubiquitination).","method":"Cryo-EM with chemically synthesized ubiquitin-mimetic crosslinkers, in vitro ubiquitylation assay, mutagenesis","journal":"Nature chemical biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structures at near-atomic resolution with chemical biology tools and mutagenesis, single study with multiple orthogonal methods","pmids":["39394267"],"is_preprint":false},{"year":2024,"finding":"K63-linked polyubiquitin chains trigger RNF168 condensation (LLPS) in vitro and in vivo; an intrinsically disordered region (aa 460-550) is essential for RNF168 LLPS; LLPS enhances RNF168-mediated H2A.X ubiquitination, forming a positive feedback loop; LLPS deficiency delays 53BP1/BRCA1 recruitment and impairs DSB repair.","method":"In vitro LLPS assay with purified proteins, domain deletion mutagenesis, immunofluorescence, in vivo irradiation assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution plus in vivo functional assays, single lab","pmids":["38968116"],"is_preprint":false},{"year":2024,"finding":"K63-linked polyubiquitylated linker histone H1.0 directly stimulates RNF168 ubiquitylation activity on nucleosomal H2A by enhancing RNF168 affinity for the chromatosome; cryo-EM of the RNF168/UbcH5c-Ub/H1.0-K63-Ub3 chromatosome complex reveals the UDM1 domain contacts K63-ubiquitin on H1.0.","method":"Chemical synthesis of ubiquitylated H1.0 (CAEPL strategy), in vitro ubiquitylation assay, cryo-EM","journal":"Angewandte Chemie","confidence":"High","confidence_rationale":"Tier 1 / Moderate — chemically defined substrates with quantitative biochemistry and cryo-EM structural validation, multiple orthogonal methods","pmids":["39363740"],"is_preprint":false},{"year":2024,"finding":"RNF168 contains a degenerate PCNA-interacting peptide (DPIP) motif that together with MIU1 mediates binding to mono-ubiquitylated PCNA at replication factories; this PCNA interaction is required for RNF168 recruitment to replication sites and support of ongoing DNA replication, but is fully dispensable for DSB signaling (53BP1 foci).","method":"Mutagenesis (DPIP/MIU1 double mutant), Co-IP with PCNA, immunofluorescence at replication factories, DNA fiber assay, 53BP1 foci formation assay","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — domain mutagenesis with separable functional readouts (replication vs DSB), multiple orthogonal methods, single lab","pmids":["39445802"],"is_preprint":false},{"year":2024,"finding":"K63-ubiquitylated H1 at different positions (K17, K46, K64, K96) stimulates RNF168 H2A ubiquitylation in a position-dependent manner; H1K17Ub2 shows the strongest RNF168 activation; di-ubiquitin binding (not monoubiquitin) drives RNF168 recruitment to DSB sites.","method":"Click chemistry synthesis of site-specific H1-diUb, in vitro ubiquitylation assay on nucleosome arrays, introduction of H1K17Ub2 into living cells","journal":"Angewandte Chemie","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — chemically defined substrates with quantitative in vitro and in vivo assays, single lab","pmids":["39377639"],"is_preprint":false},{"year":2024,"finding":"UBE2D3 E2 enzyme promotes RNF168-dependent chromatin ubiquitination and 53BP1 recruitment for NHEJ; simultaneously, UBE2D3 limits RNF168 hyperaccumulation; defective UBE2D3 leads to RNF168 hyperaccumulation that aberrantly activates PP2A phosphatase to restrict KAP1-S824 phosphorylation and NHEJ.","method":"RNAi/CRISPR, Co-IP, immunofluorescence, telomere NHEJ assay, phosphorylation assays","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus epistasis plus functional NHEJ readouts, single lab","pmids":["38866770"],"is_preprint":false},{"year":2025,"finding":"CDK1/2 phosphorylates RNF168 at T208, enabling PIN1 isomerase binding; PIN1 promotes SUMOylation of RNF168 at K210 (adjacent to the SPaCR motif); SUMOylation leads to p97/VCP-mediated removal of RNF168 from damaged chromatin, limiting ubiquitin signaling.","method":"Mutagenesis (T208, K210), Co-IP, in vivo SUMOylation assay, immunofluorescence, radiosensitivity assay","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — site-specific mutagenesis with in vivo SUMOylation and functional readouts, single lab","pmids":["40229270"],"is_preprint":false},{"year":2025,"finding":"ZNF451 SUMO E3 ligase catalyzes SUMO2 modification of RNF168, stabilizing it and enhancing its accumulation at DSBs to increase H2A/H2AX ubiquitination; ZNF451 and RNF8 jointly regulate RNF168 recruitment in a competitive-cooperative manner.","method":"SUMOylation assay, Co-IP, immunofluorescence, mutagenesis, epistasis (double ZNF451/RNF8 depletion)","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo SUMOylation assay plus epistasis analysis, single lab","pmids":["40055579"],"is_preprint":false},{"year":2021,"finding":"RNF168 interacts with STAT1 in the nucleus, stabilizing STAT1 protein by inhibiting its poly-ubiquitination and proteasomal degradation in esophageal cancer cells.","method":"Co-IP, immunoblot, RNAi knockdown","journal":"Journal of cellular and molecular medicine","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP with no in vitro ubiquitylation or mechanistic follow-up, single lab","pmids":["30506884"],"is_preprint":false},{"year":2021,"finding":"RNF168 directly interacts with RhoC and promotes its K48-linked ubiquitylation and proteasomal degradation in NSCLC and gastric cancer cells, suppressing cancer stem cell-like traits.","method":"Co-IP, in vivo ubiquitylation assay, immunoblot, overexpression/knockdown","journal":"Environmental toxicology / Biochemical and biophysical research communications","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP plus in vivo ubiquitylation without in vitro reconstitution, single lab","pmids":["34873829","33865221"],"is_preprint":false},{"year":2018,"finding":"RNF17 E3 ligase and its cognate E2 UBE2U function upstream of RNF168 to regulate 53BP1 foci formation at DSBs; RNF17-UBE2U constitutes a new E2-E3 module regulating the RNF168 pathway.","method":"RNAi-based E2 screen, immunofluorescence for 53BP1 foci, Co-IP for UBE2U-RNF17 interaction","journal":"The Journal of biological chemistry","confidence":"Low","confidence_rationale":"Tier 3 / Weak — screen-based identification with limited mechanistic follow-up, single lab","pmids":["27903633"],"is_preprint":false},{"year":2014,"finding":"BCL10 is recruited to DSBs in an ATM- and RNF8-dependent manner; ATM-dependent BCL10 phosphorylation promotes BCL10-UBC13 interaction; RNF8-mediated BCL10 ubiquitination enhances BCL10 and UBC13 binding to RNF168, facilitating RNF168-dependent H2AX monoubiquitination.","method":"Co-IP, in vivo ubiquitylation assay, immunofluorescence, ATM inhibitor experiments","journal":"Cell cycle","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP-based mechanistic proposal with functional readouts but limited in vitro reconstitution, single lab","pmids":["24732096"],"is_preprint":false},{"year":2014,"finding":"RNF168 and SET8 methyltransferase form stable complexes in vivo; SET8 recruitment to DSBs is abolished by RNF8 or RNF168 knockdown or by proteasome inhibition that depletes free ubiquitin, placing SET8 downstream of RNF168 in the DSB pathway.","method":"Co-IP, RNAi epistasis, proteasome inhibitor, immunofluorescence","journal":"Cell cycle","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP plus epistasis without direct mechanistic assay, single lab","pmids":["31760894"],"is_preprint":false},{"year":2024,"finding":"RNF168 promotes ubiquitination and degradation of ANXA7, suppressing autophagy and inducing NLRP3 inflammasome-mediated pyroptosis; ELK1 transcription factor regulates RNF168 expression in this colitis context.","method":"Co-IP, ubiquitination assay, siRNA knockdown, in vivo mouse model","journal":"Apoptosis","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP plus in vivo ubiquitylation in a disease context, single lab, limited mechanistic depth","pmids":["41518435"],"is_preprint":false}],"current_model":"RNF168 is a RING-type E3 ubiquitin ligase that is recruited to DNA double-strand breaks downstream of RNF8 (via ubiquitylated L3MBTL2 and K63-linked ubiquitin chains on linker histone H1 recognized by its UDM1/UDM2 domains and UMI/MIU ubiquitin-binding modules), whereupon it monoubiquitylates nucleosomal H2A/H2AX specifically at K13/15 (and generates K27-linked chains) by engaging the nucleosome acidic patch—as defined by cryo-EM, NMR, and reconstitution studies—to recruit 53BP1 (which it also directly K63-ubiquitylates) and BRCA1-BARD1-PALB2-RAD51 complexes for DSB repair pathway choice; its activity is amplified by K63-polyubiquitin-triggered liquid-liquid phase separation and positively regulated by ZNF451-mediated SUMO2 modification, and is restrained by mTOR-S6K1 phosphorylation at Ser60, CDK1/2-PIN1-SUMO2-p97-mediated chromatin removal, and multiple deubiquitylases (USP3, USP7, USP14, USP44), while it also ubiquitylates non-histone substrates including 53BP1, JMJD2A, TOP2α, DHX9, PARP1, FOXM1, and RhoC to coordinate genome stability, DNA repair pathway choice, and R-loop resolution."},"narrative":{"mechanistic_narrative":"RNF168 is a RING-type E3 ubiquitin ligase that orchestrates the chromatin ubiquitylation cascade governing DNA double-strand break (DSB) repair pathway choice [PMID:19203579, PMID:22980979]. It is recruited to damage sites downstream of RNF8 through recognition of K63-linked ubiquitin conjugates by its tandem ubiquitin-binding modules (MIU and the UIM/MIU-related UMI), which fold as single α-helices that simultaneously engage distal and proximal ubiquitin to confer K63-chain specificity [PMID:19203579, PMID:21041483, PMID:29330428]; RNF8-ubiquitylated adaptors including L3MBTL2 and polyubiquitylated linker histone H1 provide the docking signal that triggers its accrual [PMID:29581593, PMID:39363740]. Once engaged, RNF168 monoubiquitylates nucleosomal H2A/H2AX specifically at the bidentate N-terminal K13/K15 site—activity that RNF8 cannot perform—and builds K63- and K27-linked chains on top of this mark [PMID:22980979, PMID:22713238, PMID:25578731]. Site selection depends on engagement of the nucleosome acidic patch, which stimulates discharge of ubiquitin from the E2 (UBC13/UbcH5c) and orients catalysis toward K13/15, as defined by reconstitution, NMR, and cryo-EM studies that established a monomeric \"helix-anchoring\" mode and a ubiquitin-recognition-driven amplification loop [PMID:24518117, PMID:30988309, PMID:38242129, PMID:39394267]. These marks recruit downstream repair effectors: RNF168 K63-ubiquitylates 53BP1 and generates the mono-ubiquitylated H2A-K15 mark read by 53BP1 in the context of H4K20 methylation, while also engaging BARD1-BRCA1-PALB2-RAD51 through a dedicated PALB2-interacting domain and the BARD1 BUDR motif to promote homologous recombination [PMID:24324146, PMID:28240985, PMID:28506460, PMID:34408138]. RNF168 thereby acts in a pathway parallel to BRCA1 for PALB2/RAD51 loading and balances end resection and NHEJ versus HR [PMID:30704900, PMID:34481157]. Its activity is amplified by K63-polyubiquitin-triggered liquid-liquid phase separation via an intrinsically disordered region [PMID:38968116] and is restrained by mTOR-S6K1 phosphorylation at Ser60, CDK1/2-PIN1-driven SUMOylation coupled to p97-mediated chromatin extraction, and multiple deubiquitylases (USP3, USP7, USP14, USP44) [PMID:29403037, PMID:40229270, PMID:23615962, PMID:24196443, PMID:25894431, PMID:29995557]. Beyond histones, RNF168 ubiquitylates non-histone substrates including JMJD2A, TOP2α, PARP1, and DHX9 to coordinate genome stability and R-loop resolution [PMID:22373579, PMID:27558965, PMID:30037213, PMID:33529165].","teleology":[{"year":2009,"claim":"Established RNF168 as the chromatin-associated amplifier of the DSB ubiquitin signal, answering how RNF8-initiated ubiquitylation is propagated to retain repair factors.","evidence":"Co-IP, ubiquitin-binding assays, RNAi, DSB foci imaging, and in vitro/in vivo ubiquitylation showing MIU-mediated ubiquitin binding and RNF8-dependent assembly amplifying K63 conjugates on H2A/H2AX","pmids":["19203579","19500350"],"confidence":"High","gaps":["Did not define the precise nucleosomal acceptor lysines","Did not resolve the direct vs adaptor-mediated recruitment cue"]},{"year":2012,"claim":"Resolved the catalytic division of labor between RNF8 and RNF168 by showing RNF168 monoubiquitylates nucleosomal H2A/H2AX at a novel bidentate K13/K15 site, defining the actual signaling mark.","evidence":"In vitro nucleosomal ubiquitylation, structure-based RING mutagenesis, MS site mapping, and histone lysine mutagenesis","pmids":["22980979","22713238"],"confidence":"High","gaps":["Did not explain the structural basis of acidic-patch engagement","Did not address how K13/15 marks are read by effectors"]},{"year":2012,"claim":"Extended RNF168 function beyond histones, showing it degrades JMJD2A/KDM4A to clear a 53BP1 competitor and links to PARP1/SMARCA5-dependent recruitment.","evidence":"In vivo ubiquitylation, reciprocal Co-IP, RNAi epistasis, laser micro-irradiation","pmids":["22373579","23264744"],"confidence":"Medium","gaps":["Single-lab Co-IP without reconstitution for JMJD2A","PARP-dependence of recruitment not structurally defined"]},{"year":2013,"claim":"Defined the E2 partnership and substrate scope, identifying RAD6 as a cognate E2 for H1.2 and 53BP1 itself as a direct K63-ubiquitylation target required for its recruitment.","evidence":"E2 RNAi screen, Co-IP, in vitro ubiquitylation, K63-specific ubiquitin mutants, checkpoint assays","pmids":["23525009","24324146"],"confidence":"Medium","gaps":["Multiple candidate E2s leave the in vivo functional E2 ambiguous","53BP1 ubiquitylation site not mapped"]},{"year":2013,"claim":"Identified the deubiquitylase layer (USP3, USP44) that counteracts RNF168 at K13/15 and K118/119, establishing reversibility of the mark.","evidence":"DUB overexpression screens, in vitro/in vivo deubiquitylation assays with site-specific readout, immunofluorescence","pmids":["23615962","24196443"],"confidence":"Medium","gaps":["Relative contribution of each DUB in vivo unresolved","Single-lab assays"]},{"year":2014,"claim":"Provided the mechanistic basis for site specificity by showing the nucleosome acidic patch stimulates E2~Ub discharge and directs ubiquitin to K13/15, with in vivo confirmation via viral acidic-patch perturbation.","evidence":"In vitro ubiquitylation with acidic-patch mutant nucleosomes, fluorescence E2~Ub discharge assay, LANA peptide perturbation in cells","pmids":["24518117","24603765"],"confidence":"High","gaps":["Atomic RNF168-nucleosome interface not yet resolved","Did not define E2 orientation on the nucleosome"]},{"year":2014,"claim":"Refined RNF168 architecture and its non-canonical E2 relationship, identifying the UMI ubiquitin-binding module and showing RNF168 (unlike RNF8) does not stably bind UBC13.","evidence":"Mutagenesis, ubiquitin-binding assays, RNF168 RING crystal structure, in vitro/in vivo Co-IP, domain swaps","pmids":["21041483","23255131"],"confidence":"High","gaps":["Functional consequence of weak UBC13 association left open","Did not explain how transient E2 engagement supports processive marking"]},{"year":2014,"claim":"Broadened RNF168's regulatory and substrate repertoire, implicating NEDD8 conjugation, TOP2α decatenation control, and downstream methyltransferase recruitment (SET8).","evidence":"In vivo neddylation/ubiquitylation assays, Co-IP, decatenation assay, RNAi epistasis","pmids":["24634510","27558965","31760894"],"confidence":"Medium","gaps":["Neddylation requirement for ligase activity not structurally validated","SET8 placement based on Co-IP/epistasis only"]},{"year":2015,"claim":"Expanded chain-type and substrate diversity, showing RNF168 builds K27-linked chains as a major damage mark and degrades FOXM1, while DUB USP7 stabilizes RNF168 itself.","evidence":"In vitro ubiquitylation with chain mutants, MS linkage analysis, Co-IP, cycloheximide chase, SUMO-defective mutant analysis","pmids":["25578731","27526106","25894431","25999347","26675234"],"confidence":"Medium","gaps":["Relative in vivo abundance of K27 vs K63 marks not quantified across systems","Most regulator interactions rest on single-lab Co-IP"]},{"year":2017,"claim":"Connected the H2A-K13/15 mark to specific downstream readers, mapping direct RNF168-PALB2 binding for HR and resolving the structural competition between 53BP1, RNF169, and RAD18 for ubiquitylated nucleosomes.","evidence":"Co-IP and domain mapping, HR assays, methyl-TROSY NMR with cryo-EM validation, molecular dynamics","pmids":["28240985","28406400","28506460"],"confidence":"High","gaps":["In vivo balance between competing readers in different cell-cycle phases not fully resolved"]},{"year":2017,"claim":"Placed RNF168 within an upstream histone H1 ubiquitylation cascade by identifying HUWE1-dependent H1 ubiquitylation as required for RNF168 recruitment.","evidence":"Quantitative di-Gly proteomics, RNAi epistasis, DSB foci imaging","pmids":["29127375"],"confidence":"Medium","gaps":["Direct biochemical reconstitution of H1-Ub-driven RNF168 recruitment not yet shown at this stage"]},{"year":2018,"claim":"Defined the recruitment adaptor (ubiquitylated L3MBTL2), the K63-chain-reading UDM1/UDM2 modules structurally, and negative regulation by RNF126, integrating recruitment with structure.","evidence":"Co-IP, in vivo ubiquitylation, RNAi epistasis, X-ray crystallography of UDM1/UDM2 with K63-diubiquitin, catalytic mutant analysis","pmids":["29581593","29330428","30529286"],"confidence":"High","gaps":["Whether L3MBTL2 is the sole RNF8-dependent docking signal not excluded"]},{"year":2018,"claim":"Established kinase and metabolic restraint of RNF168, with mTORC1-S6K1 Ser60 phosphorylation inhibiting activity and driving degradation, plus DUB control by USP14 and PRMT5-dependent expression.","evidence":"In vitro kinase assay, phospho-specific antibodies, mouse tumor model, Co-IP with domain mapping, immunoblot","pmids":["29403037","29995557","31533041"],"confidence":"High","gaps":["Integration of metabolic signaling with acute DDR kinetics not resolved","PRMT5-RNF168 axis correlative in part"]},{"year":2018,"claim":"Added PARP-coupled substrate control by showing RNF168 K48-ubiquitylates PARP1 for degradation in a PAR-dependent manner, tuning HR/NHEJ balance.","evidence":"MS site mapping, in vivo ubiquitylation, comet and HR/NHEJ reporter assays","pmids":["30037213"],"confidence":"Medium","gaps":["No in vitro reconstitution of PAR-dependent ubiquitylation","Single-lab study"]},{"year":2019,"claim":"Placed RNF168 in a BRCA1-parallel pathway for PALB2/RAD51 loading and defined the BARD1 BUDR-mediated reader mechanism downstream of mUb-H2A.","evidence":"Mouse genetic epistasis, RAD51/PALB2 foci imaging, PARP inhibitor sensitivity, Brca1 coiled-coil mutant epistasis","pmids":["30704900","34408138"],"confidence":"High","gaps":["Quantitative contribution of RNF168 vs BRCA1 routes across cell types not delineated"]},{"year":2019,"claim":"Extended RNF168 to replication-stress and R-loop biology by showing it ubiquitylates DHX9 to enable R-loop resolution and is structurally shown to direct UBC13 toward K13/15 on the nucleosome.","evidence":"Co-IP, in vivo ubiquitylation, S9.6 R-loop detection, NMR with crosslinking MS and structural modeling","pmids":["33529165","30988309"],"confidence":"High","gaps":["DHX9 ubiquitylation site/chain type not fully defined","Structural model not yet a near-atomic experimental structure"]},{"year":2020,"claim":"Generalized the substrate to H2A variants (H2AZ, macroH2A) and defined a bipartite electrostatic orientation mechanism on the nucleosome.","evidence":"In vitro ubiquitylation with acidic-patch and alpha1-extension mutants, immunofluorescence","pmids":["32424115"],"confidence":"Medium","gaps":["Functional role of variant ubiquitylation in DDR not established"]},{"year":2021,"claim":"Connected RNF168 to interstrand crosslink repair and resection control, showing SLX4 recruitment via K63-chain recognition and dual roles in promoting and restraining end resection.","evidence":"siRNA screen, genetic epistasis survival assays, NHEJ/resection assays, laser-induced ICL tracks","pmids":["34706224","34481157"],"confidence":"Medium","gaps":["Context-dependent switch between resection-promoting and -restricting roles mechanistically unresolved"]},{"year":2021,"claim":"Identified additional upstream activators, including RNF8-ubiquitylated KMT5A that stimulates RNF168 H2A activity via acidic-patch residues, linking H4K20me to H2A ubiquitylation.","evidence":"In vitro ubiquitylation, Co-IP, R188/R189 mutagenesis, ChIP","pmids":["33710666"],"confidence":"Medium","gaps":["Single-lab; quantitative contribution of KMT5A activation in vivo unclear"]},{"year":2023,"claim":"Revealed phase separation and chromatin-extraction layers of regulation, with SUMOylation-driven LLPS restricting recruitment and HDAC6 gating RNF168 access to H2A.","evidence":"In vitro LLPS and SUMOylation assays, NHEJ reporters, Co-IP, in vivo ubiquitylation, K116 mutagenesis","pmids":["37350666","37503842"],"confidence":"Medium","gaps":["Apparent opposing effects of SUMO/LLPS on activity require reconciliation across studies","Single-lab reconstitutions"]},{"year":2024,"claim":"Delivered near-atomic structural mechanism of the full reaction cycle, defining a monomeric helix-anchoring mode and how ubiquitin recognition drives site-specific K13/K15 dual monoubiquitination.","evidence":"Cryo-EM (including chemical ubiquitin-mimetic crosslinkers) and NMR with in vitro ubiquitylation and mutagenesis","pmids":["38242129","39394267"],"confidence":"High","gaps":["Dynamics of the amplification loop in chromatin context not fully captured"]},{"year":2024,"claim":"Established linker-histone-driven activation and a K63-chain-triggered LLPS feedback loop, plus a replication-specific PCNA-binding function separable from DSB signaling.","evidence":"Chemically synthesized ubiquitylated H1.0/H1, cryo-EM of chromatosome complexes, in vitro LLPS with IDR deletion, DPIP/MIU1 mutagenesis, DNA fiber assays","pmids":["39363740","39377639","38968116","39445802"],"confidence":"High","gaps":["In vivo position-specific H1 ubiquitylation patterns not mapped","Interplay of LLPS feedback with negative regulators unresolved"]},{"year":2024,"claim":"Defined the productive E2 (UBE2D3) for chromatin ubiquitination while showing it also caps RNF168 hyperaccumulation through a PP2A-KAP1 axis.","evidence":"RNAi/CRISPR, Co-IP, telomere NHEJ and phosphorylation assays","pmids":["38866770"],"confidence":"Medium","gaps":["Mechanism of UBE2D3-imposed accumulation limit not structurally defined"]},{"year":2025,"claim":"Resolved opposing SUMO-based regulatory inputs: CDK1/2-PIN1-driven SUMOylation triggers p97-mediated chromatin removal, while ZNF451-mediated SUMO2 stabilizes and enhances RNF168.","evidence":"Site-specific mutagenesis (T208/K210), in vivo SUMOylation assays, Co-IP, epistasis, radiosensitivity assays","pmids":["40229270","40055579"],"confidence":"Medium","gaps":["How distinct SUMO modifications produce opposite outcomes mechanistically unresolved","Single-lab studies"]},{"year":null,"claim":"How the many positive and negative regulatory layers (phosphorylation, SUMOylation, LLPS, DUBs, p97 extraction, competing E2s) are temporally integrated to set DSB repair pathway choice in vivo remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified quantitative model of RNF168 regulation across the DDR timeline","Non-DDR substrate roles (STAT1, RhoC, ANXA7) remain low-confidence and mechanistically thin"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,2,4,9,15,44]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[2,3,6,14,27,29]},{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[0,2,9]},{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[2,10,37,46]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[29]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[12,26]}],"localization":[{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[0,1,2]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[2,4,10]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,18,52]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[0,2,30,31,39]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[2,10,34,43,46]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[3,14,27,16,24]},{"term_id":"R-HSA-69306","term_label":"DNA Replication","supporting_discovery_ids":[47]}],"complexes":[],"partners":["RNF8","53BP1","PALB2","BARD1","USP7","L3MBTL2","UBE2D3","PARP1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8IYW5","full_name":"E3 ubiquitin-protein ligase RNF168","aliases":["RING finger protein 168","RING-type E3 ubiquitin transferase RNF168"],"length_aa":571,"mass_kda":65.0,"function":"E3 ubiquitin-protein ligase required for accumulation of repair proteins to sites of DNA damage. Acts with UBE2N/UBC13 to amplify the RNF8-dependent histone ubiquitination. Recruited to sites of DNA damage at double-strand breaks (DSBs) by binding to ubiquitinated histone H2A and H2AX and amplifies the RNF8-dependent H2A ubiquitination, promoting the formation of 'Lys-63'-linked ubiquitin conjugates. This leads to concentrate ubiquitinated histones H2A and H2AX at DNA lesions to the threshold required for recruitment of TP53BP1 and BRCA1. Also recruited at DNA interstrand cross-links (ICLs) sites and promotes accumulation of 'Lys-63'-linked ubiquitination of histones H2A and H2AX, leading to recruitment of FAAP20/C1orf86 and Fanconi anemia (FA) complex, followed by interstrand cross-link repair. H2A ubiquitination also mediates the ATM-dependent transcriptional silencing at regions flanking DSBs in cis, a mechanism to avoid collision between transcription and repair intermediates. Also involved in class switch recombination in immune system, via its role in regulation of DSBs repair. Following DNA damage, promotes the ubiquitination and degradation of JMJD2A/KDM4A in collaboration with RNF8, leading to unmask H4K20me2 mark and promote the recruitment of TP53BP1 at DNA damage sites. Not able to initiate 'Lys-63'-linked ubiquitination in vitro; possibly due to partial occlusion of the UBE2N/UBC13-binding region. Catalyzes monoubiquitination of 'Lys-13' and 'Lys-15' of nucleosomal histone H2A (H2AK13Ub and H2AK15Ub, respectively)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q8IYW5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/RNF168","classification":"Common Essential","n_dependent_lines":665,"n_total_lines":1208,"dependency_fraction":0.5504966887417219},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/RNF168","total_profiled":1310},"omim":[{"mim_id":"618650","title":"RING FINGER PROTEIN 169; RNF169","url":"https://www.omim.org/entry/618650"},{"mim_id":"618030","title":"SHIELD COMPLEX, SUBUNIT 3; SHLD3","url":"https://www.omim.org/entry/618030"},{"mim_id":"618029","title":"SHIELD COMPLEX, SUBUNIT 2; 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communications","url":"https://pubmed.ncbi.nlm.nih.gov/33865221","citation_count":7,"is_preprint":false},{"pmid":"25304081","id":"PMC_25304081","title":"The ubiquitin ligases RNF8 and RNF168 display rapid but distinct dynamics at DNA repair foci in living cells.","date":"2014","source":"The international journal of biochemistry & cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/25304081","citation_count":6,"is_preprint":false},{"pmid":"39445802","id":"PMC_39445802","title":"PCNA-binding activity separates RNF168 functions in DNA replication and DNA double-stranded break signaling.","date":"2024","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/39445802","citation_count":5,"is_preprint":false},{"pmid":"38866770","id":"PMC_38866770","title":"UBE2D3 facilitates NHEJ by orchestrating ATM signalling through multi-level control of RNF168.","date":"2024","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/38866770","citation_count":5,"is_preprint":false},{"pmid":"31225475","id":"PMC_31225475","title":"Calling RNF168 to action.","date":"2018","source":"Cell stress","url":"https://pubmed.ncbi.nlm.nih.gov/31225475","citation_count":5,"is_preprint":false},{"pmid":"30901561","id":"PMC_30901561","title":"Context Matters: RNF168 Connects with PALB2 to Rewire Homologous Recombination in BRCA1 Haploinsufficiency.","date":"2019","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/30901561","citation_count":5,"is_preprint":false},{"pmid":"40229270","id":"PMC_40229270","title":"PIN1-SUMO2/3 motif suppresses excessive RNF168 chromatin accumulation and ubiquitin signaling to promote IR resistance.","date":"2025","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/40229270","citation_count":4,"is_preprint":false},{"pmid":"34881184","id":"PMC_34881184","title":"MRE11 and UBR5 Co-Operate to Suppress RNF168-Mediated Fusion of Dysfunctional Telomeres.","date":"2021","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/34881184","citation_count":4,"is_preprint":false},{"pmid":"31760894","id":"PMC_31760894","title":"SET8 localization to chromatin flanking DNA damage is dependent on RNF168 ubiquitin ligase.","date":"2019","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/31760894","citation_count":4,"is_preprint":false},{"pmid":"28754805","id":"PMC_28754805","title":"Retroviral insertional mutagenesis implicates E3 ubiquitin ligase RNF168 in the control of cell proliferation and survival.","date":"2017","source":"Bioscience reports","url":"https://pubmed.ncbi.nlm.nih.gov/28754805","citation_count":4,"is_preprint":false},{"pmid":"41034232","id":"PMC_41034232","title":"TRIM39-mediated deubiquitination upregulates RNF168 to evade autophagy-ferroptosis in triple-negative breast cancer.","date":"2025","source":"NPJ breast cancer","url":"https://pubmed.ncbi.nlm.nih.gov/41034232","citation_count":2,"is_preprint":false},{"pmid":"32616507","id":"PMC_32616507","title":"Not Black or White but Shades of Gray: Homologous Recombination Deficiency as a Continuous Variable Modulated by RNF168.","date":"2020","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/32616507","citation_count":1,"is_preprint":false},{"pmid":"40993809","id":"PMC_40993809","title":"RNF168 dephosphorylation ameliorates cognitive decline in Aβ-based mouse models of Alzheimer's disease.","date":"2025","source":"Acta neuropathologica communications","url":"https://pubmed.ncbi.nlm.nih.gov/40993809","citation_count":0,"is_preprint":false},{"pmid":"41518435","id":"PMC_41518435","title":"RNF168 promotes chronic colitis through ANXA7-mediated autophagy and NLRP3-driven pyroptosis.","date":"2026","source":"Apoptosis : an international journal on programmed cell death","url":"https://pubmed.ncbi.nlm.nih.gov/41518435","citation_count":0,"is_preprint":false},{"pmid":"41617976","id":"PMC_41617976","title":"Targeting the USP7-PRMT6 epigenetic axis overcomes chemoresistance in breast cancer by coordinating H3R2me2a deposition and RNF168 methylation for DNA repair and ferroptosis blockade.","date":"2026","source":"Cell death and differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/41617976","citation_count":0,"is_preprint":false},{"pmid":"41555391","id":"PMC_41555391","title":"The mutual regulation of SOX12 and RNF168 modulates cisplatin resistance in esophageal squamous cell carcinoma cells by regulating DNA damage repair.","date":"2026","source":"Cell & bioscience","url":"https://pubmed.ncbi.nlm.nih.gov/41555391","citation_count":0,"is_preprint":false},{"pmid":"38462450","id":"PMC_38462450","title":"Topology of Ubiquitin Chains in the Chromatosomal Environment of the E3 Ubiquitin Ligase RNF168.","date":"2023","source":"Biochemistry. Biokhimiia","url":"https://pubmed.ncbi.nlm.nih.gov/38462450","citation_count":0,"is_preprint":false},{"pmid":"41722124","id":"PMC_41722124","title":"Lupenone regulates LOXL2-mediated PANoptosis signaling through E3 ubiquitin ligases RNF168 to improve radiation-induced lung injury.","date":"2026","source":"Phytomedicine : international journal of phytotherapy and phytopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/41722124","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":48509,"output_tokens":13313,"usd":0.172611,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":24505,"output_tokens":7444,"usd":0.154312,"stage2_stop_reason":"end_turn"},"total_usd":0.326923,"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\": 2009,\n      \"finding\": \"RNF168 is a chromatin-associated RING finger E3 ubiquitin ligase that binds ubiquitin via MIU domains, assembles at DSBs in an RNF8-dependent manner, and amplifies K63-linked ubiquitin conjugates on H2A and H2AX to levels required for retention of 53BP1 and BRCA1 at damage sites.\",\n      \"method\": \"Co-IP, ubiquitin-binding assays, RNAi knockdown, immunofluorescence at DSB foci, in vivo and in vitro ubiquitylation assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Co-IP, in vitro ligase assay, RNAi, live-cell imaging), replicated across labs\",\n      \"pmids\": [\"19203579\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"RNF168 contains two MIU (motif interacting with ubiquitin) domains whose inactivation impairs ubiquitin binding in vitro and reduces chromatin association in vivo; RNF168 ubiquitylates H2A and H2AX (but not H2B) forming K63-linked polyubiquitin chains in vitro and in vivo.\",\n      \"method\": \"In vitro ubiquitin-binding assay, in vitro/in vivo ubiquitylation assay, mutagenesis of MIU domains, immunofluorescence\",\n      \"journal\": \"BMC molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro ubiquitylation assay with mutagenesis plus in vivo validation, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"19500350\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"RNF168 (not RNF8) catalyzes monoubiquitination of nucleosomal H2A/H2AX specifically at K13-15; RNF8 is inactive toward nucleosomal H2A. A charged residue in the RNF168 RING domain determines nucleosomal substrate recognition. K63-linked ubiquitin chains are conjugated on top of RNF168-dependent K13-15 monoubiquitination, not K118-119.\",\n      \"method\": \"In vitro nucleosomal ubiquitylation assay, structure-based mutagenesis of RING domains, mass spectrometry to map ubiquitylation sites\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution with nucleosomes in vitro, mutagenesis, MS site mapping, replicated by independent groups\",\n      \"pmids\": [\"22980979\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"RNF168 ubiquitylates JMJD2A/KDM4A, targeting it for proteasomal degradation; this removes a competitor of 53BP1 for dimethylated H4K20, thereby allowing 53BP1 recruitment to DNA damage sites.\",\n      \"method\": \"In vivo ubiquitylation assay, co-IP, RNAi knockdown epistasis, immunofluorescence at DSB foci\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, in vivo ubiquitylation, epistasis via double knockdown, single lab\",\n      \"pmids\": [\"22373579\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"RNF168 ubiquitylates histone H2A at a novel N-terminal 'bidentate' site comprising K13 and K15; inactivating both N-terminal (K13/K15) and C-terminal (K118/K119) sites is required to fully abolish damage-induced ubiquitination, indicating these are unique, non-redundant acceptors.\",\n      \"method\": \"Mutagenesis of histone lysine residues, in vivo ubiquitylation assay, immunofluorescence\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis combined with in vivo ubiquitylation assay, consistent with parallel Cell paper (PMID:22980979)\",\n      \"pmids\": [\"22713238\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"SMARCA5/SNF2H is recruited to DSBs in a PARP1-dependent manner, interacts with RNF168 in a DNA damage- and PARP-dependent manner, and promotes RNF168 accumulation at DSBs; RNF168 itself becomes poly(ADP-ribosyl)ated after DNA damage.\",\n      \"method\": \"Co-IP, immunofluorescence, RNAi knockdown, laser micro-irradiation\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP and RNAi with functional readout, single lab, multiple supporting experiments\",\n      \"pmids\": [\"23264744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"RNF168 mediates K63-linked ubiquitylation of 53BP1, which is required for the initial recruitment of 53BP1 to DSBs and for its functions in DNA repair and checkpoint activation.\",\n      \"method\": \"In vivo ubiquitylation assay, Co-IP, K63-specific ubiquitin mutants, immunofluorescence, checkpoint assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo ubiquitylation with chain-specificity mutants, functional readouts, single lab\",\n      \"pmids\": [\"24324146\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"USP44 counteracts RNF8/RNF168-mediated ubiquitylation of H2A and is specifically recruited to RNF168-generated ubiquitylation products at DSBs, acting as a negative regulator at the level of RNF168 accrual.\",\n      \"method\": \"DUB overexpression screen, H2A deubiquitylation assay, immunofluorescence, RNAi\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional screen plus in vivo H2A deubiquitylation assay, single lab\",\n      \"pmids\": [\"23615962\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"USP3 removes ubiquitin at K13 and K15 of H2A/γH2AX (RNF168 target sites) as well as K118/K119 of H2AX in response to DNA damage, counteracting RNF168-mediated ubiquitination.\",\n      \"method\": \"In vitro deubiquitylation assay, co-IP, immunofluorescence, ectopic expression experiments\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro DUB assay with site-specific readout, in vivo validation, single lab\",\n      \"pmids\": [\"24196443\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"RNF168 forms a functional complex with RAD6A/RAD6B E2 enzymes; this RNF168-RAD6 complex ubiquitinates histone H1.2 in vitro and regulates DNA damage-induced H1.2 ubiquitination in vivo.\",\n      \"method\": \"E2 RNAi screen, Co-IP, in vitro ubiquitylation assay, immunofluorescence\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro ubiquitylation reconstitution plus in vivo co-IP, single lab\",\n      \"pmids\": [\"23525009\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The nucleosome acidic patch is required for RNF168-dependent H2A/H2AX ubiquitination at K13/15 both in vitro and in vivo; H2A/H2B dimers and nucleosomes actively stimulate E3-mediated discharge of ubiquitin from E2, redirecting the reaction toward the target lysines.\",\n      \"method\": \"In vitro ubiquitylation assay with acidic-patch mutant nucleosomes, viral LANA peptide perturbation in vivo, fluorescence-based E2~Ub discharge assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — reconstituted in vitro with defined nucleosome substrates and mechanistic discharge assay, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"24518117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The nucleosome acidic patch is required for both RNF168-dependent H2AX ubiquitination and DDR factor (53BP1, BRCA1) recruitment in vivo; perturbation of the acidic patch by the LANA viral peptide phenocopies RNF168 loss.\",\n      \"method\": \"In vitro ubiquitylation assay, viral LANA peptide expression, RNAi, immunofluorescence\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro plus in vivo assays, consistent with PMID:24518117, single lab\",\n      \"pmids\": [\"24603765\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"RNF168 contains a novel UBD designated UMI (UIM- and MIU-related UBD); the UMI binds ubiquitin via two leucine residues and is required together with MIU domains for proper RNF168 localization and H2A ubiquitination.\",\n      \"method\": \"Mutagenesis, ubiquitin-binding assays, immunofluorescence, in vivo ubiquitylation assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis with in vitro binding and in vivo functional readouts, single lab\",\n      \"pmids\": [\"21041483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"RNF168 mediates NEDD8 conjugation (neddylation) to H2A and is itself neddylated; neddylation of RNF168 is required for its interaction with E2 enzyme Ubc13 and its ubiquitin ligase activity. H2A neddylation antagonizes H2A ubiquitylation.\",\n      \"method\": \"In vivo neddylation assay, Co-IP, mutagenesis, immunofluorescence\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with E2 interaction readout, in vivo neddylation assay, single lab\",\n      \"pmids\": [\"24634510\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"RNF168 interacts with and ubiquitylates topoisomerase IIα (TOP2α), regulating its decatenation activity and chromatin association; USP10 counteracts this by deubiquitylating TOP2α.\",\n      \"method\": \"Co-IP, in vivo ubiquitylation assay, decatenation assay, RNAi\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus functional decatenation assay, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"27558965\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"RNF168 promotes K27-linked (noncanonical) ubiquitin chain formation both in vitro and in vivo; K27-ubiquitin on chromatin is the major ubiquitin mark upon DNA damage and is directly recognized by 53BP1, Rap80, RNF168, and RNF169.\",\n      \"method\": \"In vitro ubiquitylation assay with K27R ubiquitin mutants, mass spectrometry chain-linkage analysis, immunofluorescence with ubiquitin mutants in cells\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro assay plus MS linkage identification plus in vivo mutant rescue, single lab\",\n      \"pmids\": [\"25578731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"USP7 deubiquitinase physically binds RNF168, stabilizes it against DNA damage-induced degradation, and its deubiquitylase activity toward RNF168 is required to maintain H2A ubiquitination and downstream BRCA1/53BP1 foci formation.\",\n      \"method\": \"Co-IP (in vitro and in vivo), in vivo ubiquitylation assay, overexpression rescue experiments, RNAi\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, in vivo ubiquitylation, functional rescue, single lab\",\n      \"pmids\": [\"25894431\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"LSD1 is recruited to DSBs in an RNF168-dependent manner and interacts directly with RNF168 and 53BP1; RNF168-dependent 53BP1 ubiquitination requires CK2-mediated phosphorylation of LSD1 at S131/S137, which promotes LSD1-RNF168 interaction.\",\n      \"method\": \"Co-IP, immunofluorescence, phosphorylation assay (CK2/WIP1), mutagenesis\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with phosphorylation mutants and functional readouts, single lab\",\n      \"pmids\": [\"25999347\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"RNF168 partially localizes to PML nuclear bodies via its UMI/MIU1 ubiquitin-interacting region; RNF168 binds hybrid SUMO2-K63 ubiquitin chains preferentially over K63-ubiquitin chains alone (confirmed in vitro); RNF168 overexpression increases ubiquitylation and SUMO2 modification of PML.\",\n      \"method\": \"shRNA screen, in vitro ubiquitin/SUMO chain binding assay, Co-IP, immunofluorescence\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro binding assay distinguishing chain types, in vivo Co-IP, single lab\",\n      \"pmids\": [\"26675234\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"RNF168 interacts with FOXM1 and mediates its K48-linked polyubiquitination and proteasomal degradation in response to epirubicin; SUMOylation of FOXM1 is required for RNF168 recruitment to FOXM1; RNF8 recruits RNF168 to this substrate.\",\n      \"method\": \"Co-IP, in vivo ubiquitylation assay, cycloheximide chase, SUMO-defective mutant analysis, gene promoter-reporter assay\",\n      \"journal\": \"Oncogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, in vivo ubiquitylation with chain-type specificity, functional rescue, single lab\",\n      \"pmids\": [\"27526106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RNF168 directly interacts with PALB2 via a newly identified PALB2-interacting domain (PID) in RNF168 and the WD40 domain in PALB2; this interaction links H2A ubiquitylation to PALB2-dependent homologous recombination at DSBs in S/G2 cells.\",\n      \"method\": \"Co-IP, pull-down, mutagenesis of PID domain, HR assay, immunofluorescence\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP with domain mapping, domain mutagenesis, functional HR assay, multiple orthogonal approaches\",\n      \"pmids\": [\"28240985\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RNF169 (RNF168 paralog) binds ubiquitylated H2A-K13/15 on the nucleosome via a three-pronged mechanism involving a canonical ubiquitin-binding helix and two arginine-rich motifs contacting the nucleosome acidic patch; this high-affinity binding displaces 53BP1 from ubiquitylated chromatin.\",\n      \"method\": \"Methyl-TROSY NMR, molecular dynamics simulations, cryo-EM validation, biochemical binding assays\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR structure with cryo-EM validation and biochemical assays, multiple orthogonal methods\",\n      \"pmids\": [\"28406400\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"53BP1 binds RNF168-mediated mono-ubiquitylated H2A-K15 in NCP dimethylated at H4K20; RNF169 stabilizes a pre-existing ubiquitin orientation on the nucleosome via a conformational selection mechanism to outcompete 53BP1; RAD18 binds tightly to ubiquitylated NCP through a domain contacting both ubiquitin and nucleosome surfaces accessed by 53BP1.\",\n      \"method\": \"NMR spectroscopy, biochemical binding assays, mutagenesis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structure with biochemical validation and mechanistic dissection, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"28506460\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"HUWE1-mediated histone H1 ubiquitylation at multiple lysines is required upstream for RNF168 recruitment and 53BP1 assembly at DSBs; HUWE1 depletion reduces RNF168 foci without affecting MDC1 (upstream of H1 ubiquitylation).\",\n      \"method\": \"Quantitative di-Gly proteomics, RNAi, immunofluorescence at DSB foci\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteomics site identification plus RNAi epistasis with defined pathway placement, single lab\",\n      \"pmids\": [\"29127375\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"mTORC1-S6K1 phosphorylates RNF168 at Ser60, inhibiting its E3 ligase activity and accelerating its proteasomal degradation; a phospho-deficient S60A mutant rescues DNA damage repair defects caused by LKB1 loss.\",\n      \"method\": \"In vitro kinase assay, phospho-specific antibody, co-IP, proteasome assay, mutagenesis, mouse tumor model\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay with site-specific mutagenesis, in vivo rescue, mouse model, multiple orthogonal methods\",\n      \"pmids\": [\"29403037\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"L3MBTL2 is ubiquitylated by RNF8 and the resulting ubiquitylated L3MBTL2 directly recruits RNF168 to DNA damage sites, providing the mechanistic link between RNF8 and RNF168 in sequential DSB signaling.\",\n      \"method\": \"Co-IP, in vivo ubiquitylation assay, immunofluorescence, RNAi epistasis\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP, in vivo ubiquitylation, epistasis, replicated across multiple experiments in the study\",\n      \"pmids\": [\"29581593\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Crystal structures of RNF168 UDM1 and UDM2 bound to K63-linked diubiquitin reveal that both modules fold as single α-helices that simultaneously contact distal and proximal ubiquitin moieties, conferring K63-chain specificity; UDM2 interaction with ubiquitylated targets primarily drives RNF168 recruitment to DSBs.\",\n      \"method\": \"X-ray crystallography, biochemical binding assays, mutagenesis, immunofluorescence in U2OS cells\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structures with mutagenesis and in vivo functional validation, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"29330428\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"RNF168 ubiquitinates PARP1 via K48-linked chains on multiple lysines, accelerating PARP1 degradation in the presence of PAR chains; PAR-binding by RNF168 is required for this activity and for regulating HR/NHEJ balance.\",\n      \"method\": \"Mass spectrometry (ubiquitination site mapping), in vivo ubiquitylation assay, Co-IP, comet assay, HR/NHEJ reporter assays\",\n      \"journal\": \"Molecules and cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS-based site mapping plus in vivo ubiquitylation and functional assays, single lab\",\n      \"pmids\": [\"30037213\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"RNF126 directly interacts with RNF168 and ubiquitinates it; RNF126 overexpression diminishes H2AX ubiquitination and downstream 53BP1/RAP80 foci in a catalytic activity-dependent manner, negatively regulating RNF168 function.\",\n      \"method\": \"Co-IP, in vivo ubiquitylation assay, immunofluorescence, HR reporter assay, catalytic mutant analysis\",\n      \"journal\": \"Genomics, proteomics & bioinformatics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, in vivo ubiquitylation, catalytic mutant, functional readout, single lab\",\n      \"pmids\": [\"30529286\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"RNF168 directly ubiquitylates DHX9 helicase to facilitate its recruitment to R-loop-prone genomic loci; loss of RNF168 impairs DHX9 recruitment and R-loop resolution, leading to DSBs in BRCA1/2-mutant cells.\",\n      \"method\": \"Co-IP (interactome assay), in vivo ubiquitylation assay, immunofluorescence, R-loop detection (S9.6 antibody), genetic epistasis\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus in vivo ubiquitylation plus functional recruitment assay, single lab\",\n      \"pmids\": [\"33529165\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"RNF168 acts redundantly with BRCA1 to load PALB2 onto damaged DNA; loss of RNF168 negates the synthetic rescue of BRCA1 deficiency by 53BP1 deletion, placing RNF168 in a pathway parallel to BRCA1 for RAD51 loading.\",\n      \"method\": \"Mouse genetics (epistasis), immunofluorescence for RAD51/PALB2 foci, PARP inhibitor sensitivity assay, forced PALB2 targeting rescue\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis in mice plus cellular functional assays, multiple orthogonal methods\",\n      \"pmids\": [\"30704900\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"RNF168-generated mUb-H2A recruits BARD1 through a BRCT domain ubiquitin-dependent recruitment motif (BUDR); BARD1-BRCA1 then accumulate PALB2-RAD51 at DSBs via the BRCA1 coiled-coil domain–PALB2 interaction.\",\n      \"method\": \"Co-IP, mouse genetics (Brca1CC mutant epistasis), immunofluorescence for PALB2/RAD51 foci\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mouse epistasis combined with Co-IP and defined domain mapping, multiple orthogonal methods\",\n      \"pmids\": [\"34408138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"HPV E7 oncoprotein directly binds a regulatory domain of RNF168 without affecting its enzymatic activity, subverting RNF168 function at DSBs; RNF168 is required for viral genome amplification in differentiated keratinocytes.\",\n      \"method\": \"Co-IP (direct binding), immunofluorescence, RNAi knockdown, viral genome amplification assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct Co-IP plus functional viral assay, single lab\",\n      \"pmids\": [\"31501315\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PRMT5 sustains RNF168 expression; RNF168 and SMURF2 serve as stabilizer and destabilizer of H2AX, respectively, through dynamic interactions with H2AX; loss of PRMT5 (in MTAP-deficient cells) attenuates RNF168, leading to H2AX destabilization by SMURF2.\",\n      \"method\": \"Co-IP, in vivo ubiquitylation assay, RNAi, immunoblot\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP with functional outcome in multiple cell types, single lab\",\n      \"pmids\": [\"31533041\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"NMR and biochemical studies show RNF168 binds the nucleosome acidic patch and directs the E2 enzyme UBC13 toward K13/15; the structural model defines the basis for site specificity.\",\n      \"method\": \"NMR spectroscopy, crosslinking mass spectrometry, mutagenesis, data-driven structural modelling\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR with XL-MS and mutagenesis providing structural mechanism, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"30988309\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"RNF168 and its cognate E2 UBC13 do not stably associate in vitro or in vivo, in contrast to the RNF8-UBC13 interaction; crystal structure of the RNF168 RING domain reveals differences at the UBC13-binding interface compared to other UBC13-binding E3s; RNF8 and RNF168 RING domains are not functionally interchangeable.\",\n      \"method\": \"X-ray crystallography, in vitro and in vivo Co-IP, domain-swap mutagenesis\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with in vitro and in vivo binding assays confirming structural prediction, single lab\",\n      \"pmids\": [\"23255131\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"USP14 deubiquitinase directly interacts with RNF168 via RNF168's MIU1 domain; USP14 activity negatively regulates RNF168 protein levels and RNF168-dependent H2A ubiquitination and 53BP1 recruitment; USP14 is itself a substrate of autophagy via SQSTM1.\",\n      \"method\": \"Co-IP, immunofluorescence, DUB activity assay, RNAi, domain mapping (MIU1)\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct Co-IP with domain mapping plus functional rescue, single lab\",\n      \"pmids\": [\"29995557\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"RNF168 ubiquitinates H2A variants H2AZ and macroH2A1/2 at their divergent N-terminal tail lysines; the positively charged alpha1-extension helix of H2A variants and the RNF168 UMI acidic residues are essential for this reaction; a bipartite electrostatic interaction directs RNF168 orientation on the nucleosome.\",\n      \"method\": \"In vitro ubiquitylation assay, mutagenesis of nucleosome acidic patch and alpha1-extension helix, immunofluorescence\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with mutagenesis, in vivo validation of foci formation, single lab\",\n      \"pmids\": [\"32424115\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"RNF8-ubiquitinated KMT5A is recruited to DSBs and binds RNF168; KMT5A promotes RNF168 catalytic activity toward H2A via its H2A acidic-patch interacting residues R188/R189, linking H4K20 monomethylation to H2A ubiquitination.\",\n      \"method\": \"In vitro ubiquitylation assay, Co-IP, mutagenesis (R188/R189), ChIP, immunofluorescence\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro ubiquitylation plus Co-IP with domain mapping, single lab\",\n      \"pmids\": [\"33710666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"RNF168 is required for SLX4/FANCP recruitment to interstrand crosslink damage sites; RNF168 is epistatic with SLX4 in promoting mitomycin C tolerance; RNF168-generated K63-linked ubiquitin chains are recognized by the tandem UBZ4 domains of SLX4.\",\n      \"method\": \"siRNA screen with GFP-SLX4, immunofluorescence, genetic epistasis (survival assays), laser-induced ICL tracks\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA screen confirmed by epistasis and localization assays, single lab\",\n      \"pmids\": [\"34706224\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"RNF168 facilitates ubiquitin signaling in RNF8/RNF168-dependent pathways that both prevent and promote DNA end resection in G0/G1 lymphocytes; combined deficiency of XLF and RNF168 leads to diminished NHEJ; in 53BP1-deficient cells, loss of RNF168 diminishes resection.\",\n      \"method\": \"Genetic knockouts in lymphocytes, NHEJ reporter assays, end-resection assays\",\n      \"journal\": \"DNA repair\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with functional NHEJ and resection assays, single lab\",\n      \"pmids\": [\"34481157\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"SUMOylated RNF168 undergoes liquid-liquid phase separation (LLPS), restricting its recruitment to DNA damage sites and reducing H2A ubiquitination; SENP1 deSUMOylates RNF168, preventing LLPS and promoting RNF168 activity and NHEJ repair.\",\n      \"method\": \"In vitro LLPS assay, SUMOylation assay, immunofluorescence, NHEJ reporter, SENP1 knockdown/overexpression\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro LLPS reconstitution plus in vivo functional assays, single lab\",\n      \"pmids\": [\"37350666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"HDAC6 interacts with H2A/H2A.X in unstressed cells to prevent RNF168 access; upon DSBs, RNF168 ubiquitinates HDAC6 at K116 leading to its proteasomal degradation and allowing RNF168-H2A/H2A.X interaction and subsequent H2A ubiquitination.\",\n      \"method\": \"Co-IP, in vivo ubiquitylation assay, immunofluorescence, mutagenesis (K116)\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with site-specific ubiquitylation mapping and functional readouts, single lab\",\n      \"pmids\": [\"37503842\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Cryo-EM and NMR structures reveal the full reaction cycle of RNF168 modifying the nucleosome: RNF168 engages the nucleosome via a canonical ubiquitin-binding domain that contacts both ubiquitin and the nucleosome surface, clarifying how ubiquitin recognition drives a signal amplification loop for site-specific H2A K13/15 ubiquitination.\",\n      \"method\": \"Cryo-EM, NMR spectroscopy, in vitro ubiquitylation assay, mutagenesis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structure with NMR and functional assays, multiple orthogonal methods in single study\",\n      \"pmids\": [\"38242129\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Cryo-EM structures of RNF168-UbcH5c~Ub-nucleosome complexes captured during H2A K13 and K15 monoubiquitination reveal a 'helix-anchoring' mode for monomeric RNF168 on the nucleosome, distinct from the 'compass-binding' mode of dimeric E3 ligases; both K13 and K15 can be independently monoubiquitinated (adjacent dual monoubiquitination).\",\n      \"method\": \"Cryo-EM with chemically synthesized ubiquitin-mimetic crosslinkers, in vitro ubiquitylation assay, mutagenesis\",\n      \"journal\": \"Nature chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structures at near-atomic resolution with chemical biology tools and mutagenesis, single study with multiple orthogonal methods\",\n      \"pmids\": [\"39394267\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"K63-linked polyubiquitin chains trigger RNF168 condensation (LLPS) in vitro and in vivo; an intrinsically disordered region (aa 460-550) is essential for RNF168 LLPS; LLPS enhances RNF168-mediated H2A.X ubiquitination, forming a positive feedback loop; LLPS deficiency delays 53BP1/BRCA1 recruitment and impairs DSB repair.\",\n      \"method\": \"In vitro LLPS assay with purified proteins, domain deletion mutagenesis, immunofluorescence, in vivo irradiation assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution plus in vivo functional assays, single lab\",\n      \"pmids\": [\"38968116\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"K63-linked polyubiquitylated linker histone H1.0 directly stimulates RNF168 ubiquitylation activity on nucleosomal H2A by enhancing RNF168 affinity for the chromatosome; cryo-EM of the RNF168/UbcH5c-Ub/H1.0-K63-Ub3 chromatosome complex reveals the UDM1 domain contacts K63-ubiquitin on H1.0.\",\n      \"method\": \"Chemical synthesis of ubiquitylated H1.0 (CAEPL strategy), in vitro ubiquitylation assay, cryo-EM\",\n      \"journal\": \"Angewandte Chemie\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — chemically defined substrates with quantitative biochemistry and cryo-EM structural validation, multiple orthogonal methods\",\n      \"pmids\": [\"39363740\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"RNF168 contains a degenerate PCNA-interacting peptide (DPIP) motif that together with MIU1 mediates binding to mono-ubiquitylated PCNA at replication factories; this PCNA interaction is required for RNF168 recruitment to replication sites and support of ongoing DNA replication, but is fully dispensable for DSB signaling (53BP1 foci).\",\n      \"method\": \"Mutagenesis (DPIP/MIU1 double mutant), Co-IP with PCNA, immunofluorescence at replication factories, DNA fiber assay, 53BP1 foci formation assay\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain mutagenesis with separable functional readouts (replication vs DSB), multiple orthogonal methods, single lab\",\n      \"pmids\": [\"39445802\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"K63-ubiquitylated H1 at different positions (K17, K46, K64, K96) stimulates RNF168 H2A ubiquitylation in a position-dependent manner; H1K17Ub2 shows the strongest RNF168 activation; di-ubiquitin binding (not monoubiquitin) drives RNF168 recruitment to DSB sites.\",\n      \"method\": \"Click chemistry synthesis of site-specific H1-diUb, in vitro ubiquitylation assay on nucleosome arrays, introduction of H1K17Ub2 into living cells\",\n      \"journal\": \"Angewandte Chemie\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — chemically defined substrates with quantitative in vitro and in vivo assays, single lab\",\n      \"pmids\": [\"39377639\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"UBE2D3 E2 enzyme promotes RNF168-dependent chromatin ubiquitination and 53BP1 recruitment for NHEJ; simultaneously, UBE2D3 limits RNF168 hyperaccumulation; defective UBE2D3 leads to RNF168 hyperaccumulation that aberrantly activates PP2A phosphatase to restrict KAP1-S824 phosphorylation and NHEJ.\",\n      \"method\": \"RNAi/CRISPR, Co-IP, immunofluorescence, telomere NHEJ assay, phosphorylation assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus epistasis plus functional NHEJ readouts, single lab\",\n      \"pmids\": [\"38866770\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CDK1/2 phosphorylates RNF168 at T208, enabling PIN1 isomerase binding; PIN1 promotes SUMOylation of RNF168 at K210 (adjacent to the SPaCR motif); SUMOylation leads to p97/VCP-mediated removal of RNF168 from damaged chromatin, limiting ubiquitin signaling.\",\n      \"method\": \"Mutagenesis (T208, K210), Co-IP, in vivo SUMOylation assay, immunofluorescence, radiosensitivity assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — site-specific mutagenesis with in vivo SUMOylation and functional readouts, single lab\",\n      \"pmids\": [\"40229270\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ZNF451 SUMO E3 ligase catalyzes SUMO2 modification of RNF168, stabilizing it and enhancing its accumulation at DSBs to increase H2A/H2AX ubiquitination; ZNF451 and RNF8 jointly regulate RNF168 recruitment in a competitive-cooperative manner.\",\n      \"method\": \"SUMOylation assay, Co-IP, immunofluorescence, mutagenesis, epistasis (double ZNF451/RNF8 depletion)\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo SUMOylation assay plus epistasis analysis, single lab\",\n      \"pmids\": [\"40055579\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"RNF168 interacts with STAT1 in the nucleus, stabilizing STAT1 protein by inhibiting its poly-ubiquitination and proteasomal degradation in esophageal cancer cells.\",\n      \"method\": \"Co-IP, immunoblot, RNAi knockdown\",\n      \"journal\": \"Journal of cellular and molecular medicine\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP with no in vitro ubiquitylation or mechanistic follow-up, single lab\",\n      \"pmids\": [\"30506884\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"RNF168 directly interacts with RhoC and promotes its K48-linked ubiquitylation and proteasomal degradation in NSCLC and gastric cancer cells, suppressing cancer stem cell-like traits.\",\n      \"method\": \"Co-IP, in vivo ubiquitylation assay, immunoblot, overexpression/knockdown\",\n      \"journal\": \"Environmental toxicology / Biochemical and biophysical research communications\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP plus in vivo ubiquitylation without in vitro reconstitution, single lab\",\n      \"pmids\": [\"34873829\", \"33865221\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"RNF17 E3 ligase and its cognate E2 UBE2U function upstream of RNF168 to regulate 53BP1 foci formation at DSBs; RNF17-UBE2U constitutes a new E2-E3 module regulating the RNF168 pathway.\",\n      \"method\": \"RNAi-based E2 screen, immunofluorescence for 53BP1 foci, Co-IP for UBE2U-RNF17 interaction\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — screen-based identification with limited mechanistic follow-up, single lab\",\n      \"pmids\": [\"27903633\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"BCL10 is recruited to DSBs in an ATM- and RNF8-dependent manner; ATM-dependent BCL10 phosphorylation promotes BCL10-UBC13 interaction; RNF8-mediated BCL10 ubiquitination enhances BCL10 and UBC13 binding to RNF168, facilitating RNF168-dependent H2AX monoubiquitination.\",\n      \"method\": \"Co-IP, in vivo ubiquitylation assay, immunofluorescence, ATM inhibitor experiments\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP-based mechanistic proposal with functional readouts but limited in vitro reconstitution, single lab\",\n      \"pmids\": [\"24732096\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"RNF168 and SET8 methyltransferase form stable complexes in vivo; SET8 recruitment to DSBs is abolished by RNF8 or RNF168 knockdown or by proteasome inhibition that depletes free ubiquitin, placing SET8 downstream of RNF168 in the DSB pathway.\",\n      \"method\": \"Co-IP, RNAi epistasis, proteasome inhibitor, immunofluorescence\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP plus epistasis without direct mechanistic assay, single lab\",\n      \"pmids\": [\"31760894\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"RNF168 promotes ubiquitination and degradation of ANXA7, suppressing autophagy and inducing NLRP3 inflammasome-mediated pyroptosis; ELK1 transcription factor regulates RNF168 expression in this colitis context.\",\n      \"method\": \"Co-IP, ubiquitination assay, siRNA knockdown, in vivo mouse model\",\n      \"journal\": \"Apoptosis\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP plus in vivo ubiquitylation in a disease context, single lab, limited mechanistic depth\",\n      \"pmids\": [\"41518435\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RNF168 is a RING-type E3 ubiquitin ligase that is recruited to DNA double-strand breaks downstream of RNF8 (via ubiquitylated L3MBTL2 and K63-linked ubiquitin chains on linker histone H1 recognized by its UDM1/UDM2 domains and UMI/MIU ubiquitin-binding modules), whereupon it monoubiquitylates nucleosomal H2A/H2AX specifically at K13/15 (and generates K27-linked chains) by engaging the nucleosome acidic patch—as defined by cryo-EM, NMR, and reconstitution studies—to recruit 53BP1 (which it also directly K63-ubiquitylates) and BRCA1-BARD1-PALB2-RAD51 complexes for DSB repair pathway choice; its activity is amplified by K63-polyubiquitin-triggered liquid-liquid phase separation and positively regulated by ZNF451-mediated SUMO2 modification, and is restrained by mTOR-S6K1 phosphorylation at Ser60, CDK1/2-PIN1-SUMO2-p97-mediated chromatin removal, and multiple deubiquitylases (USP3, USP7, USP14, USP44), while it also ubiquitylates non-histone substrates including 53BP1, JMJD2A, TOP2α, DHX9, PARP1, FOXM1, and RhoC to coordinate genome stability, DNA repair pathway choice, and R-loop resolution.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RNF168 is a RING-type E3 ubiquitin ligase that orchestrates the chromatin ubiquitylation cascade governing DNA double-strand break (DSB) repair pathway choice [#0, #2]. It is recruited to damage sites downstream of RNF8 through recognition of K63-linked ubiquitin conjugates by its tandem ubiquitin-binding modules (MIU and the UIM/MIU-related UMI), which fold as single α-helices that simultaneously engage distal and proximal ubiquitin to confer K63-chain specificity [#0, #12, #26]; RNF8-ubiquitylated adaptors including L3MBTL2 and polyubiquitylated linker histone H1 provide the docking signal that triggers its accrual [#25, #46]. Once engaged, RNF168 monoubiquitylates nucleosomal H2A/H2AX specifically at the bidentate N-terminal K13/K15 site\\u2014activity that RNF8 cannot perform\\u2014and builds K63- and K27-linked chains on top of this mark [#2, #4, #15]. Site selection depends on engagement of the nucleosome acidic patch, which stimulates discharge of ubiquitin from the E2 (UBC13/UbcH5c) and orients catalysis toward K13/15, as defined by reconstitution, NMR, and cryo-EM studies that established a monomeric \\\"helix-anchoring\\\" mode and a ubiquitin-recognition-driven amplification loop [#10, #34, #43, #44]. These marks recruit downstream repair effectors: RNF168 K63-ubiquitylates 53BP1 and generates the mono-ubiquitylated H2A-K15 mark read by 53BP1 in the context of H4K20 methylation, while also engaging BARD1-BRCA1-PALB2-RAD51 through a dedicated PALB2-interacting domain and the BARD1 BUDR motif to promote homologous recombination [#6, #20, #22, #31]. RNF168 thereby acts in a pathway parallel to BRCA1 for PALB2/RAD51 loading and balances end resection and NHEJ versus HR [#30, #40]. Its activity is amplified by K63-polyubiquitin-triggered liquid-liquid phase separation via an intrinsically disordered region [#45] and is restrained by mTOR-S6K1 phosphorylation at Ser60, CDK1/2-PIN1-driven SUMOylation coupled to p97-mediated chromatin extraction, and multiple deubiquitylases (USP3, USP7, USP14, USP44) [#24, #50, #7, #8, #16, #36]. Beyond histones, RNF168 ubiquitylates non-histone substrates including JMJD2A, TOP2\\u03b1, PARP1, and DHX9 to coordinate genome stability and R-loop resolution [#3, #14, #27, #29].\",\n  \"teleology\": [\n    {\n      \"year\": 2009,\n      \"claim\": \"Established RNF168 as the chromatin-associated amplifier of the DSB ubiquitin signal, answering how RNF8-initiated ubiquitylation is propagated to retain repair factors.\",\n      \"evidence\": \"Co-IP, ubiquitin-binding assays, RNAi, DSB foci imaging, and in vitro/in vivo ubiquitylation showing MIU-mediated ubiquitin binding and RNF8-dependent assembly amplifying K63 conjugates on H2A/H2AX\",\n      \"pmids\": [\"19203579\", \"19500350\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the precise nucleosomal acceptor lysines\", \"Did not resolve the direct vs adaptor-mediated recruitment cue\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Resolved the catalytic division of labor between RNF8 and RNF168 by showing RNF168 monoubiquitylates nucleosomal H2A/H2AX at a novel bidentate K13/K15 site, defining the actual signaling mark.\",\n      \"evidence\": \"In vitro nucleosomal ubiquitylation, structure-based RING mutagenesis, MS site mapping, and histone lysine mutagenesis\",\n      \"pmids\": [\"22980979\", \"22713238\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not explain the structural basis of acidic-patch engagement\", \"Did not address how K13/15 marks are read by effectors\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Extended RNF168 function beyond histones, showing it degrades JMJD2A/KDM4A to clear a 53BP1 competitor and links to PARP1/SMARCA5-dependent recruitment.\",\n      \"evidence\": \"In vivo ubiquitylation, reciprocal Co-IP, RNAi epistasis, laser micro-irradiation\",\n      \"pmids\": [\"22373579\", \"23264744\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab Co-IP without reconstitution for JMJD2A\", \"PARP-dependence of recruitment not structurally defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined the E2 partnership and substrate scope, identifying RAD6 as a cognate E2 for H1.2 and 53BP1 itself as a direct K63-ubiquitylation target required for its recruitment.\",\n      \"evidence\": \"E2 RNAi screen, Co-IP, in vitro ubiquitylation, K63-specific ubiquitin mutants, checkpoint assays\",\n      \"pmids\": [\"23525009\", \"24324146\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Multiple candidate E2s leave the in vivo functional E2 ambiguous\", \"53BP1 ubiquitylation site not mapped\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified the deubiquitylase layer (USP3, USP44) that counteracts RNF168 at K13/15 and K118/119, establishing reversibility of the mark.\",\n      \"evidence\": \"DUB overexpression screens, in vitro/in vivo deubiquitylation assays with site-specific readout, immunofluorescence\",\n      \"pmids\": [\"23615962\", \"24196443\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative contribution of each DUB in vivo unresolved\", \"Single-lab assays\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Provided the mechanistic basis for site specificity by showing the nucleosome acidic patch stimulates E2~Ub discharge and directs ubiquitin to K13/15, with in vivo confirmation via viral acidic-patch perturbation.\",\n      \"evidence\": \"In vitro ubiquitylation with acidic-patch mutant nucleosomes, fluorescence E2~Ub discharge assay, LANA peptide perturbation in cells\",\n      \"pmids\": [\"24518117\", \"24603765\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic RNF168-nucleosome interface not yet resolved\", \"Did not define E2 orientation on the nucleosome\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Refined RNF168 architecture and its non-canonical E2 relationship, identifying the UMI ubiquitin-binding module and showing RNF168 (unlike RNF8) does not stably bind UBC13.\",\n      \"evidence\": \"Mutagenesis, ubiquitin-binding assays, RNF168 RING crystal structure, in vitro/in vivo Co-IP, domain swaps\",\n      \"pmids\": [\"21041483\", \"23255131\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of weak UBC13 association left open\", \"Did not explain how transient E2 engagement supports processive marking\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Broadened RNF168's regulatory and substrate repertoire, implicating NEDD8 conjugation, TOP2\\u03b1 decatenation control, and downstream methyltransferase recruitment (SET8).\",\n      \"evidence\": \"In vivo neddylation/ubiquitylation assays, Co-IP, decatenation assay, RNAi epistasis\",\n      \"pmids\": [\"24634510\", \"27558965\", \"31760894\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Neddylation requirement for ligase activity not structurally validated\", \"SET8 placement based on Co-IP/epistasis only\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Expanded chain-type and substrate diversity, showing RNF168 builds K27-linked chains as a major damage mark and degrades FOXM1, while DUB USP7 stabilizes RNF168 itself.\",\n      \"evidence\": \"In vitro ubiquitylation with chain mutants, MS linkage analysis, Co-IP, cycloheximide chase, SUMO-defective mutant analysis\",\n      \"pmids\": [\"25578731\", \"27526106\", \"25894431\", \"25999347\", \"26675234\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative in vivo abundance of K27 vs K63 marks not quantified across systems\", \"Most regulator interactions rest on single-lab Co-IP\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Connected the H2A-K13/15 mark to specific downstream readers, mapping direct RNF168-PALB2 binding for HR and resolving the structural competition between 53BP1, RNF169, and RAD18 for ubiquitylated nucleosomes.\",\n      \"evidence\": \"Co-IP and domain mapping, HR assays, methyl-TROSY NMR with cryo-EM validation, molecular dynamics\",\n      \"pmids\": [\"28240985\", \"28406400\", \"28506460\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo balance between competing readers in different cell-cycle phases not fully resolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Placed RNF168 within an upstream histone H1 ubiquitylation cascade by identifying HUWE1-dependent H1 ubiquitylation as required for RNF168 recruitment.\",\n      \"evidence\": \"Quantitative di-Gly proteomics, RNAi epistasis, DSB foci imaging\",\n      \"pmids\": [\"29127375\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct biochemical reconstitution of H1-Ub-driven RNF168 recruitment not yet shown at this stage\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Defined the recruitment adaptor (ubiquitylated L3MBTL2), the K63-chain-reading UDM1/UDM2 modules structurally, and negative regulation by RNF126, integrating recruitment with structure.\",\n      \"evidence\": \"Co-IP, in vivo ubiquitylation, RNAi epistasis, X-ray crystallography of UDM1/UDM2 with K63-diubiquitin, catalytic mutant analysis\",\n      \"pmids\": [\"29581593\", \"29330428\", \"30529286\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether L3MBTL2 is the sole RNF8-dependent docking signal not excluded\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Established kinase and metabolic restraint of RNF168, with mTORC1-S6K1 Ser60 phosphorylation inhibiting activity and driving degradation, plus DUB control by USP14 and PRMT5-dependent expression.\",\n      \"evidence\": \"In vitro kinase assay, phospho-specific antibodies, mouse tumor model, Co-IP with domain mapping, immunoblot\",\n      \"pmids\": [\"29403037\", \"29995557\", \"31533041\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Integration of metabolic signaling with acute DDR kinetics not resolved\", \"PRMT5-RNF168 axis correlative in part\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Added PARP-coupled substrate control by showing RNF168 K48-ubiquitylates PARP1 for degradation in a PAR-dependent manner, tuning HR/NHEJ balance.\",\n      \"evidence\": \"MS site mapping, in vivo ubiquitylation, comet and HR/NHEJ reporter assays\",\n      \"pmids\": [\"30037213\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vitro reconstitution of PAR-dependent ubiquitylation\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Placed RNF168 in a BRCA1-parallel pathway for PALB2/RAD51 loading and defined the BARD1 BUDR-mediated reader mechanism downstream of mUb-H2A.\",\n      \"evidence\": \"Mouse genetic epistasis, RAD51/PALB2 foci imaging, PARP inhibitor sensitivity, Brca1 coiled-coil mutant epistasis\",\n      \"pmids\": [\"30704900\", \"34408138\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative contribution of RNF168 vs BRCA1 routes across cell types not delineated\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Extended RNF168 to replication-stress and R-loop biology by showing it ubiquitylates DHX9 to enable R-loop resolution and is structurally shown to direct UBC13 toward K13/15 on the nucleosome.\",\n      \"evidence\": \"Co-IP, in vivo ubiquitylation, S9.6 R-loop detection, NMR with crosslinking MS and structural modeling\",\n      \"pmids\": [\"33529165\", \"30988309\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"DHX9 ubiquitylation site/chain type not fully defined\", \"Structural model not yet a near-atomic experimental structure\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Generalized the substrate to H2A variants (H2AZ, macroH2A) and defined a bipartite electrostatic orientation mechanism on the nucleosome.\",\n      \"evidence\": \"In vitro ubiquitylation with acidic-patch and alpha1-extension mutants, immunofluorescence\",\n      \"pmids\": [\"32424115\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional role of variant ubiquitylation in DDR not established\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Connected RNF168 to interstrand crosslink repair and resection control, showing SLX4 recruitment via K63-chain recognition and dual roles in promoting and restraining end resection.\",\n      \"evidence\": \"siRNA screen, genetic epistasis survival assays, NHEJ/resection assays, laser-induced ICL tracks\",\n      \"pmids\": [\"34706224\", \"34481157\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Context-dependent switch between resection-promoting and -restricting roles mechanistically unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified additional upstream activators, including RNF8-ubiquitylated KMT5A that stimulates RNF168 H2A activity via acidic-patch residues, linking H4K20me to H2A ubiquitylation.\",\n      \"evidence\": \"In vitro ubiquitylation, Co-IP, R188/R189 mutagenesis, ChIP\",\n      \"pmids\": [\"33710666\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab; quantitative contribution of KMT5A activation in vivo unclear\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed phase separation and chromatin-extraction layers of regulation, with SUMOylation-driven LLPS restricting recruitment and HDAC6 gating RNF168 access to H2A.\",\n      \"evidence\": \"In vitro LLPS and SUMOylation assays, NHEJ reporters, Co-IP, in vivo ubiquitylation, K116 mutagenesis\",\n      \"pmids\": [\"37350666\", \"37503842\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Apparent opposing effects of SUMO/LLPS on activity require reconciliation across studies\", \"Single-lab reconstitutions\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Delivered near-atomic structural mechanism of the full reaction cycle, defining a monomeric helix-anchoring mode and how ubiquitin recognition drives site-specific K13/K15 dual monoubiquitination.\",\n      \"evidence\": \"Cryo-EM (including chemical ubiquitin-mimetic crosslinkers) and NMR with in vitro ubiquitylation and mutagenesis\",\n      \"pmids\": [\"38242129\", \"39394267\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Dynamics of the amplification loop in chromatin context not fully captured\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established linker-histone-driven activation and a K63-chain-triggered LLPS feedback loop, plus a replication-specific PCNA-binding function separable from DSB signaling.\",\n      \"evidence\": \"Chemically synthesized ubiquitylated H1.0/H1, cryo-EM of chromatosome complexes, in vitro LLPS with IDR deletion, DPIP/MIU1 mutagenesis, DNA fiber assays\",\n      \"pmids\": [\"39363740\", \"39377639\", \"38968116\", \"39445802\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo position-specific H1 ubiquitylation patterns not mapped\", \"Interplay of LLPS feedback with negative regulators unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Defined the productive E2 (UBE2D3) for chromatin ubiquitination while showing it also caps RNF168 hyperaccumulation through a PP2A-KAP1 axis.\",\n      \"evidence\": \"RNAi/CRISPR, Co-IP, telomere NHEJ and phosphorylation assays\",\n      \"pmids\": [\"38866770\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of UBE2D3-imposed accumulation limit not structurally defined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Resolved opposing SUMO-based regulatory inputs: CDK1/2-PIN1-driven SUMOylation triggers p97-mediated chromatin removal, while ZNF451-mediated SUMO2 stabilizes and enhances RNF168.\",\n      \"evidence\": \"Site-specific mutagenesis (T208/K210), in vivo SUMOylation assays, Co-IP, epistasis, radiosensitivity assays\",\n      \"pmids\": [\"40229270\", \"40055579\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How distinct SUMO modifications produce opposite outcomes mechanistically unresolved\", \"Single-lab studies\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the many positive and negative regulatory layers (phosphorylation, SUMOylation, LLPS, DUBs, p97 extraction, competing E2s) are temporally integrated to set DSB repair pathway choice in vivo remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified quantitative model of RNF168 regulation across the DDR timeline\", \"Non-DDR substrate roles (STAT1, RhoC, ANXA7) remain low-confidence and mechanistically thin\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 2, 4, 9, 15, 44]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2, 3, 6, 14, 27, 29]},\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [0, 2, 9]},\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [2, 10, 37, 46]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [29]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [12, 26]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [2, 4, 10]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 18, 52]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [0, 2, 30, 31, 39]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [2, 10, 34, 43, 46]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [3, 14, 27, 16, 24]},\n      {\"term_id\": \"R-HSA-69306\", \"supporting_discovery_ids\": [47]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"RNF8\", \"53BP1\", \"PALB2\", \"BARD1\", \"USP7\", \"L3MBTL2\", \"UBE2D3\", \"PARP1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}