{"gene":"UBE2V2","run_date":"2026-06-10T10:51:56","timeline":{"discoveries":[{"year":1999,"finding":"Mms2p (yeast ortholog of UBE2V2) forms a specific heteromeric complex with Ubc13p (E2) and is required for Ubc13p-dependent assembly of Lys63-linked polyubiquitin chains. A ubc13 strain is UV sensitive, and single, double, and triple mutants of UBC13, MMS2, and ubiquitin ubiK63R display comparable UV sensitivity, establishing the Mms2p/Ubc13p complex as essential for assembling K63-linked polyubiquitin chains used in DNA repair signaling.","method":"In vitro ubiquitin chain assembly assay with purified components; yeast genetics (epistasis with ubc13, mms2, ubiK63R mutants); UV sensitivity phenotyping","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted in vitro chain assembly, paired with rigorous yeast genetic epistasis; foundational study replicated by multiple subsequent labs","pmids":["10089880"],"is_preprint":false},{"year":1998,"finding":"MMS2 encodes a Ubc-like protein that lacks E2 (ubiquitin-conjugating) activity but functions specifically in the error-free postreplication repair (PRR) pathway in yeast. Genetic analysis showed mms2 is hypostatic to rad6 and rad18, synergistic with rev3, and proficient in UV mutagenesis, placing MMS2 in the error-free branch of the RAD6 pathway parallel to the REV3 mutagenesis pathway.","method":"Functional complementation cloning; genetic epistasis analysis (double/triple mutant UV sensitivity); UV-induced mutagenesis assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic epistasis with multiple pathway members, replicated in subsequent studies","pmids":["9576943"],"is_preprint":false},{"year":2001,"finding":"Crystal structure of the Mms2/Ubc13 heterodimer reveals the Ubc13 active site at the intersection of two channels that are potential binding sites for two substrate ubiquitins. Mutations destabilizing the heterodimer interface confer marked UV sensitivity, demonstrating the intact heterodimer is necessary for DNA repair.","method":"X-ray crystallography; site-directed mutagenesis of heterodimer interface; yeast UV sensitivity assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with mutagenesis and in vivo functional validation","pmids":["11440714"],"is_preprint":false},{"year":2001,"finding":"Human Mms2 and Ubc13 form a stable heterodimer capable of transferring ubiquitin specifically to Lys63 of an untethered ubiquitin, producing diubiquitin. NMR mapping identified a surface of the acceptor ubiquitin that interacts with Mms2 in both monomeric and heterodimeric forms, with the C-terminal tail of ubiquitin not participating, supporting the model that Mms2 orients acceptor ubiquitin to position Lys63 proximal to the Ubc13 active site.","method":"In vitro ubiquitin chain assembly with purified human Mms2 and Ubc13; 1H-15N HSQC NMR mapping of ubiquitin-Mms2 and ubiquitin-Ubc13 interaction surfaces","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with purified human proteins plus NMR structural mapping, multiple orthogonal methods","pmids":["11504715"],"is_preprint":false},{"year":2003,"finding":"NMR-based structural model of the human Ubc13·Mms2 heterodimer bound to acceptor and donor ubiquitin reveals the molecular basis of K63-specific chain synthesis: Mms2 binds acceptor ubiquitin non-covalently while Ubc13 carries donor ubiquitin as a thioester, positioning Lys63 of acceptor ubiquitin at the Ubc13 active site.","method":"2D 1H-15N NMR chemical shift mapping of subunit-subunit and subunit-ubiquitin interactions; unbiased computational docking using NMR-derived restraints","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR-based structural model with multiple interaction surfaces mapped using orthogonal approaches; consistent with crystal structure from separate lab","pmids":["12569095"],"is_preprint":false},{"year":2005,"finding":"Mms2-Ile57 and ubiquitin-Ile44 are critical molecular determinants of the Mms2–acceptor ubiquitin interaction. Mutating either side chain to alanine causes 10–20-fold inhibition of K63-linked chain synthesis in vitro by compromising acceptor ubiquitin binding to Mms2, and abolishes error-free lesion bypass in vivo in yeast.","method":"Site-directed mutagenesis; in vitro K63-linked chain assembly assay; yeast error-free bypass assay (DNA damage sensitivity)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro mutagenesis combined with quantitative binding and in vivo functional data; single lab but multiple orthogonal methods","pmids":["15772086"],"is_preprint":false},{"year":2005,"finding":"A single 'key' residue of Mms2 inserts into a complementary pocket of Ubc13 to determine interface specificity. Structure-based mutagenesis identified critical residues at the Ubc13–Mms2 interface; disrupting these contacts abrogates heterodimer formation, ubiquitin conjugation, and functional complementation of DNA repair, explaining why Mms2 forms a specific complex with Ubc13 but not other E2s.","method":"Structure-based mutagenesis; yeast two-hybrid; GST pulldown; surface plasmon resonance; functional complementation of yeast mms2 mutant; in vitro ubiquitin conjugation assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — multiple orthogonal binding assays (Y2H, pulldown, SPR) combined with in vitro activity and in vivo complementation","pmids":["15749714"],"is_preprint":false},{"year":2005,"finding":"The two mammalian UEV proteins, Mms2 and Uev1A, differentially modulate the length of Ubc13-mediated K63-linked polyubiquitin chains. Ubc13–Mms2 is required for DNA damage repair but not NF-κB activation, whereas Ubc13–Uev1A is involved in NF-κB activation but not DNA repair, demonstrating that alternative UEV pairing directs Ubc13 to distinct cellular processes.","method":"Structural comparison; in vitro ubiquitin chain length assays; siRNA knockdown with functional assays (UV sensitivity/DNA repair; NF-κB reporter assays)","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal functional assays (repair + NF-κB) combined with biochemical chain assembly; directly distinguishes the two paralogs","pmids":["16129784"],"is_preprint":false},{"year":2006,"finding":"Crystal structure of Mms2–Ubc13 covalently linked to donor ubiquitin (UEV-E2-Ub intermediate) reveals that an acceptor-ubiquitin binding site on Mms2 (from an adjacent complex in the crystal) positions Lys63 of acceptor ubiquitin at the Ubc13 active site, providing the structural basis for K63 linkage specificity in polyubiquitin chain elongation.","method":"X-ray crystallography of covalent Mms2–Ubc13–ubiquitin intermediate","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structure of catalytic intermediate, independently consistent with prior NMR and crystal structures from other labs","pmids":["16980971"],"is_preprint":false},{"year":2006,"finding":"Human SHPRH physically interacts with the Mms2–Ubc13 complex and acts as the E3 ubiquitin ligase indispensable for Mms2–Ubc13-dependent K63-linked polyubiquitylation of PCNA, placing SHPRH as the E3 partner of Mms2–Ubc13 in human error-free PRR.","method":"Co-immunoprecipitation; in vitro ubiquitylation assay with purified components; siRNA knockdown of SHPRH with PCNA ubiquitylation readout","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro reconstitution of PCNA polyubiquitylation plus reciprocal co-IP and siRNA knockdown; multiple orthogonal methods","pmids":["17108083"],"is_preprint":false},{"year":2006,"finding":"NMR solution structure of human Mms2 bound to ubiquitin reveals the molecular basis for the non-covalent Mms2–ubiquitin interaction that positions acceptor ubiquitin for K63-linked chain synthesis.","method":"Solution-state NMR spectroscopy (structure determination of Mms2–ubiquitin complex)","journal":"Journal of biomolecular NMR","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR structure determination providing atomic-resolution view of the interface; consistent with prior crystal and NMR data","pmids":["16518696"],"is_preprint":false},{"year":2006,"finding":"AT2 receptor signaling in neurons induces MMS2 (UBE2V2) expression via the ATIP–SHP-1 cascade. ATIP and SHP-1 translocate to the nucleus after forming a complex upon AT2 receptor stimulation; increased MMS2 expression mediates inhibitor of DNA binding 1 (Id1) proteolysis and promotes DNA repair, and siRNA knockdown of MMS2 abolishes neurite outgrowth and synapse formation.","method":"siRNA knockdown of MMS2; overexpression and dominant-negative SHP-1; co-immunoprecipitation of ATIP–SHP-1 complex; nuclear fractionation; RT-PCR of MMS2 expression; neurite outgrowth assay; synapse formation assay","journal":"Molecular endocrinology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — siRNA knockdown with clear phenotypic readouts (no neurite outgrowth) and Co-IP of upstream partners; single lab, functional link is indirect","pmids":["17068200"],"is_preprint":false},{"year":2003,"finding":"Chfr ubiquitin ligase catalyzes formation of non-canonical K63-linked polyubiquitin chains using Ubc13–Mms2 as the ubiquitin-conjugating enzyme, rather than targeting proteins for proteasomal degradation; this activity is proposed to signal mitotic stress.","method":"In vitro ubiquitin ligase assay; ubiquitin chain linkage characterization","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — in vitro reconstitution of K63-chain formation, single lab, single method for the chain linkage characterization","pmids":["14562038"],"is_preprint":false},{"year":2007,"finding":"Two residues of human Mms2 cooperatively interact with ubiquitin to promote Ubc13-mediated K63-linked polyubiquitin chain formation: each single mutation reduces binding affinity, but the double mutation severely reduces ubiquitin binding and abolishes polyubiquitin chain formation in vitro and in vivo (yeast double mutant shows complete loss of MMS2 function).","method":"Site-directed mutagenesis; in vitro polyubiquitin chain assembly assay; binding assays; yeast functional complementation","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis combined with in vitro chain assembly and in vivo yeast functional assays; consistent with prior structural data","pmids":["17964296"],"is_preprint":false},{"year":2012,"finding":"RNF8 dimerizes and binds to Ubc13/Mms2, stimulating K63-linked ubiquitin chain formation at DNA double-strand breaks; the crystal structure of the RNF8/Ubc13/Mms2 ternary complex reveals that an RNF8 coiled-coil mediates dimerization and that disrupting RNF8/Ubc13 binding surfaces or truncating the coiled-coil reduces ubiquitylation. In contrast, RNF168 RING domain is monomeric and does not catalyze K63 polyubiquitylation with Ubc13/Mms2.","method":"X-ray crystallography of RNF8/Ubc13/Mms2 ternary complex; site-directed mutagenesis; in vitro ubiquitylation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure of ternary complex plus mutagenesis and in vitro activity assays; single lab but multiple orthogonal methods","pmids":["22589545"],"is_preprint":false},{"year":2018,"finding":"Ube2V2 contains a functionally privileged sensor cysteine that can be modified by reactive electrophiles in a non-enzyme-catalyzed manner. This modification allosterically hyperactivates Ube2V2's binding partner Ube2N (Ubc13), promoting K63-linked client ubiquitination and stimulating H2AX-dependent DNA damage response.","method":"G-REX electrophile-release technology for in vivo cysteine identification; mass spectrometry; in vitro K63-linked ubiquitination assays; γH2AX DNA damage response readout","journal":"ACS central science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — novel chemical biology approach (G-REX) combined with in vitro ubiquitination activity assays and cellular DDR readout; single lab, multiple methods","pmids":["29532025"],"is_preprint":false},{"year":2002,"finding":"Rad5 protein and the Mms2–Ubc13 ubiquitin-conjugating enzyme complex are both required for postreplication repair of UV-damaged DNA in yeast: discontinuities in newly synthesized DNA strands from UV-damaged templates are not repaired in rad5Δ or mms2Δ mutants, indicating these components act in the same pathway for error-free gap filling.","method":"Yeast genetic analysis; alkaline sucrose gradient sedimentation to detect DNA discontinuities in rad5Δ and mms2Δ strains","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct biochemical measurement of DNA repair intermediates combined with genetic epistasis; replicated in subsequent studies","pmids":["11884624"],"is_preprint":false},{"year":2004,"finding":"The Rad18/Rad5/Mms2 polyubiquitination pathway is important for replication completion in yeast: PCNA-K164R (blocking ubiquitination) and mms2Δ/rad5Δ mutations impair replication in rfc5-1 mutants, indicating Mms2-dependent PCNA polyubiquitination promotes a template-switch type of DNA synthesis during replication stress.","method":"Yeast genetics; PCNA mutant (K164R) analysis; epistasis analysis combining mms2Δ, rad5Δ, siz1Δ, rad18Δ mutations with replication-defective alleles; growth assays","journal":"Genes to cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with defined alleles and replication readout; single lab, no direct biochemical confirmation of mechanism","pmids":["15507115"],"is_preprint":false},{"year":1998,"finding":"Human MMS2 (hMMS2/UBE2V2) and its close paralog CROC-1 functionally complement yeast mms2 mutations for DNA damage sensitivity and spontaneous mutagenesis, demonstrating conservation of Mms2 function. Both yeast MMS2 and human hMMS2 also transactivate a c-fos–CAT reporter gene in Rat-1 cells.","method":"Functional complementation of yeast mms2 mutant; DNA damage sensitivity assays; mutagenesis assays; transient co-transfection reporter assay (c-fos–CAT)","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional complementation across species with DNA repair and mutagenesis assays; single lab","pmids":["9705497"],"is_preprint":false},{"year":2007,"finding":"Yeast Chfr homologs Chf1/Chf2 require Ubc13/Mms2 for G2 cell-cycle delay but not for Chf protein turnover; Ubc4 mediates G1 delay and Chf protein turnover. Reconstituted in vitro ubiquitination and tandem MS characterization of ubiquitin chain linkages showed that Ubc13/Mms2-dependent modifications are a distinct subset of those catalyzed by Ubc4, with site-specific mutagenesis confirming different functional consequences.","method":"Genetic analysis in yeast; in vitro ubiquitination reconstitution with purified components; tandem mass spectrometry linkage analysis; site-directed mutagenesis of ubiquitination sites","journal":"Cell cycle","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — in vitro reconstitution + MS linkage analysis + genetic validation; single lab","pmids":["18202552"],"is_preprint":false},{"year":2011,"finding":"Zebrafish Mms2 (DrMms2) forms a stable complex with DrUbc13 and promotes K63-linked polyubiquitination in vitro. Morpholino knockdown of DrMms2 (but not DrUev1) enhances spontaneous and DNA-damage-induced expression of p53 effectors p21 and mdm2 in zebrafish embryos. Additionally, DrUbc13 specifically binds p53 in vitro, linking the Mms2–Ubc13 complex to the p53-mediated DNA damage response.","method":"Zebrafish morpholino knockdown; in vitro K63-linked polyubiquitination assay; in vitro GST pulldown (DrUbc13–p53 binding); RT-PCR of p53 target genes (p21, mdm2)","journal":"DNA repair","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — morpholino KD with molecular readout plus in vitro binding assay; single lab, vertebrate model","pmids":["22055568"],"is_preprint":false},{"year":2020,"finding":"Ubc13–Mms2 contributes to K63-linked polyubiquitylation in membrane protein sorting to the yeast vacuole via the multivesicular body (MVB) pathway. Genetic analysis identified FYVE-RING finger E3 proteins (including Pib1) as cognate E3 partners for Ubc13–Mms2 in membrane trafficking, revealing a role for Ubc13–Mms2 in membrane protein sorting beyond DNA repair.","method":"Yeast genetics (deletion analysis, epistasis); fluorescence microscopy of membrane protein trafficking; identification of E3 partners by genetic interaction screening","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with clear pathway placement in MVB sorting; single lab, genetic methods without in vitro reconstitution of the new pathway","pmids":["32265276"],"is_preprint":false},{"year":2023,"finding":"Mms2 overproduction in yeast causes a spontaneous mutator effect that is independent of Ubc13 but requires Ubc4, the HECT E3 Rsp5, and RING E3 Not4, as well as error-prone polymerases ζ and Rev1 and PCNA K164 ubiquitination. Mms2 abundance also influences Pol3 (Polδ catalytic subunit) cellular levels: loss of Mms2 increases Pol3 abundance, while Mms2 overproduction decreases Pol3 levels.","method":"Yeast genetics; Western blotting for Pol3 levels; epistasis analysis with ubc13Δ, ubc4Δ, rsp5, not4, rev3Δ, rev1Δ, and pcna-K164R mutants; spontaneous mutagenesis assays","journal":"DNA repair","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic genetic epistasis combined with protein level measurements; single lab, no in vitro reconstitution of the Ubc4-dependent pathway","pmids":["36934633"],"is_preprint":false},{"year":2025,"finding":"In Drosophila, Uev1A (ortholog of UBE2V2) collaborates with the E3 APC/C complex to mediate proteasomal degradation of Cyclin A, thereby protecting polyploid cells from aberrant division stress induced by oncogenic Ras. Overexpression of human UBE2V2 mitigates oncogenic Ras-induced nurse cell death, and UBE2V2 counteracts oncogenic Ras-driven tumorigenesis in human colorectal tumor xenografts in nude mice.","method":"Drosophila genome-wide genetic screen; Drosophila knockdown/overexpression with oncogenic Ras; human colorectal tumor xenograft in nude mice; Cyclin A degradation assay (Uev1A + APC/C reconstitution implied by genetic and xenograft evidence)","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — preprint; Drosophila genetic screen with xenograft validation; APC/C-Cyclin A degradation mechanism is supported genetically but biochemical reconstitution details are not described in abstract","pmids":[],"is_preprint":true}],"current_model":"UBE2V2 (Mms2) is a catalytically inactive ubiquitin-conjugating enzyme variant (UEV) that forms a stable heterodimer with the E2 enzyme Ubc13 (UBE2N); within this complex, UBE2V2 non-covalently binds acceptor ubiquitin and orients its Lys63 toward the Ubc13 active site, thereby directing exclusive synthesis of K63-linked polyubiquitin chains that serve as non-proteolytic signals in error-free postreplication DNA repair (via PCNA polyubiquitylation with E3s SHPRH/Rad5) and DNA double-strand break response (via RNF8); in contrast to its paralog Uev1A/UBE2V1, which directs Ubc13 toward NF-κB activation, UBE2V2 specifically supports DNA damage tolerance; additionally, an allosteric sensor cysteine on UBE2V2 can be modified by electrophiles to hyperactivate Ubc13 and stimulate H2AX-dependent DNA damage signaling."},"narrative":{"mechanistic_narrative":"UBE2V2 (Mms2) is a catalytically inactive ubiquitin-conjugating enzyme variant (UEV) that functions as the specificity-determining partner of the E2 enzyme Ubc13/UBE2N in the assembly of Lys63-linked polyubiquitin chains used as non-proteolytic DNA repair signals [PMID:10089880, PMID:9576943]. UBE2V2 forms an obligate, specific heterodimer with Ubc13: a single key Mms2 residue inserts into a complementary Ubc13 pocket to enforce pairing exclusivity, and disrupting this interface abolishes heterodimer formation, ubiquitin conjugation, and DNA repair function [PMID:15749714, PMID:11440714]. Within the complex UBE2V2 binds an acceptor ubiquitin non-covalently while Ubc13 carries the donor ubiquitin as a thioester, orienting acceptor Lys63 at the Ubc13 active site to dictate strict K63 linkage; this geometry was resolved through NMR and crystal structures of the heterodimer and its covalent UEV-E2-Ub intermediate, and the Mms2-Ile57/ubiquitin-Ile44 contact is a critical determinant of acceptor binding and chain synthesis [PMID:12569095, PMID:16980971, PMID:15772086, PMID:16518696]. The Ubc13-Mms2 complex operates in the error-free branch of postreplication repair, where it acts with the E3 ligases SHPRH and Rad5 to catalyze K63-linked polyubiquitylation of PCNA, promoting template-switch DNA synthesis during replication stress [PMID:17108083, PMID:11884624, PMID:15507115], and at DNA double-strand breaks it pairs with the dimeric E3 RNF8 to generate K63 chains [PMID:22589545]. UEV partner choice routes Ubc13 to distinct outcomes: Mms2/UBE2V2 supports DNA repair but not NF-κB activation, the reverse of its paralog Uev1A/UBE2V1 [PMID:16129784]. A privileged sensor cysteine on UBE2V2 can be covalently modified by reactive electrophiles to allosterically hyperactivate Ubc13 and stimulate H2AX-dependent DNA damage signaling [PMID:29532025].","teleology":[{"year":1998,"claim":"Established that MMS2 is a Ubc-like protein lacking E2 activity that acts specifically in the error-free postreplication repair branch, distinguishing it from mutagenic lesion bypass.","evidence":"Complementation cloning and genetic epistasis (hypostatic to rad6/rad18, synergistic with rev3) with UV mutagenesis assays in yeast","pmids":["9576943"],"confidence":"High","gaps":["Did not define the molecular partner or biochemical activity of Mms2","No chain-linkage information"]},{"year":1999,"claim":"Identified that Mms2 acts through a heteromeric complex with Ubc13 to assemble K63-linked chains, linking the genetic repair phenotype to a specific biochemical activity.","evidence":"Reconstituted in vitro chain assembly with purified components plus yeast genetic epistasis (ubc13/mms2/ubiK63R) and UV sensitivity phenotyping","pmids":["10089880"],"confidence":"High","gaps":["Structural basis of K63 specificity not yet known","E3 ligase partners and physiological substrates unidentified"]},{"year":1998,"claim":"Showed human MMS2 functionally conserves yeast Mms2 repair activity, extending the pathway to mammals.","evidence":"Cross-species functional complementation of yeast mms2 with DNA damage/mutagenesis assays and a c-fos–CAT reporter in Rat-1 cells","pmids":["9705497"],"confidence":"Medium","gaps":["c-fos transactivation link is correlative and mechanistically undefined","Single lab"]},{"year":2001,"claim":"Resolved the heterodimer architecture and demonstrated the intact interface is required for repair, and that the human complex builds K63-specific diubiquitin by orienting acceptor ubiquitin.","evidence":"X-ray crystallography of Mms2/Ubc13 with interface mutagenesis and UV assays; in vitro chain assembly and NMR mapping of human Mms2/Ubc13/ubiquitin surfaces","pmids":["11440714","11504715"],"confidence":"High","gaps":["Donor-ubiquitin positioning during catalysis not yet visualized","E3 partners still unidentified"]},{"year":2002,"claim":"Placed Rad5 together with Mms2-Ubc13 in the same error-free gap-filling pathway, connecting the complex to repair of replication discontinuities.","evidence":"Yeast genetics and alkaline sucrose gradient detection of DNA discontinuities in rad5Δ/mms2Δ strains","pmids":["11884624"],"confidence":"High","gaps":["Direct biochemical demonstration of Rad5 as the E3 not shown here","PCNA as substrate not yet established in this study"]},{"year":2003,"claim":"Provided a complete structural model of how acceptor and donor ubiquitin are jointly positioned to enforce K63 linkage, defining the catalytic logic of the complex.","evidence":"NMR chemical-shift mapping and restraint-driven computational docking of the Ubc13·Mms2 complex with both ubiquitins","pmids":["12569095"],"confidence":"High","gaps":["Model from docking restraints rather than a single crystallized ternary intermediate","Catalytic transition state not captured"]},{"year":2003,"claim":"Identified Chfr as an E3 that uses Ubc13-Mms2 to build non-degradative K63 chains, broadening the complex's role to mitotic stress signaling.","evidence":"In vitro ubiquitin ligase assay with chain-linkage characterization","pmids":["14562038"],"confidence":"Medium","gaps":["Single method for linkage determination","Physiological mitotic substrate not defined"]},{"year":2004,"claim":"Connected Mms2-dependent PCNA polyubiquitination to template-switch DNA synthesis under replication stress.","evidence":"Yeast genetics with PCNA-K164R and mms2Δ/rad5Δ/rad18Δ epistasis in replication-defective backgrounds","pmids":["15507115"],"confidence":"Medium","gaps":["No direct biochemical confirmation of the template-switch mechanism","Single lab"]},{"year":2005,"claim":"Defined the molecular determinants of acceptor-ubiquitin recognition and interface specificity, explaining both K63 fidelity and exclusive Ubc13 pairing.","evidence":"Site-directed mutagenesis (Mms2-Ile57/Ub-Ile44; the 'key' interface residue) with in vitro chain assembly, SPR/Y2H/pulldown binding, and yeast complementation","pmids":["15772086","15749714"],"confidence":"High","gaps":["Single-lab mutagenesis studies","Quantitative kinetics of chain elongation not fully resolved"]},{"year":2005,"claim":"Established that UEV partner identity (Mms2 vs Uev1A) routes Ubc13 to distinct cellular pathways, separating DNA repair from NF-κB activation.","evidence":"In vitro chain-length assays plus siRNA knockdown with UV/DNA-repair and NF-κB reporter readouts","pmids":["16129784"],"confidence":"High","gaps":["Mechanism by which partner choice alters chain length not defined","Mammalian E3 specificity for each pathway not detailed here"]},{"year":2006,"claim":"Captured the catalytic intermediate by crystallography and an NMR Mms2-ubiquitin structure, confirming how acceptor Lys63 is positioned at the active site during elongation.","evidence":"X-ray structure of covalent Mms2-Ubc13-ubiquitin intermediate; solution NMR structure of Mms2-ubiquitin","pmids":["16980971","16518696"],"confidence":"High","gaps":["Acceptor positioning inferred from adjacent crystal complex","Dynamics of processive elongation not addressed"]},{"year":2006,"claim":"Identified SHPRH as the human E3 partner of Mms2-Ubc13 for K63-linked PCNA polyubiquitylation, completing the mammalian error-free PRR enzyme set.","evidence":"Co-IP, in vitro ubiquitylation reconstitution, and SHPRH siRNA knockdown with PCNA ubiquitylation readout","pmids":["17108083"],"confidence":"High","gaps":["Relative contributions of SHPRH versus other E3s in cells not quantified","Downstream polymerase-switch step not directly reconstituted"]},{"year":2006,"claim":"Linked UBE2V2 to neuronal AT2 receptor signaling, where induced MMS2 promotes Id1 proteolysis, DNA repair, and neurite/synapse formation.","evidence":"siRNA knockdown of MMS2 with neurite/synapse phenotyping, Co-IP of the ATIP-SHP-1 complex, nuclear fractionation, and RT-PCR","pmids":["17068200"],"confidence":"Medium","gaps":["Functional link between MMS2 and the neuronal phenotype is indirect","Single lab"]},{"year":2007,"claim":"Demonstrated cooperative two-residue ubiquitin binding by Mms2 is essential, where the double mutant abolishes chain formation and yeast function.","evidence":"Site-directed mutagenesis with in vitro chain assembly, binding assays, and yeast complementation","pmids":["17964296"],"confidence":"High","gaps":["Single-lab study","Energetic basis of cooperativity not dissected"]},{"year":2007,"claim":"Distinguished Ubc13/Mms2-dependent ubiquitination as a separate functional subset from Ubc4-mediated turnover in Chfr-homolog cell-cycle control.","evidence":"Yeast genetics, in vitro ubiquitination reconstitution, tandem-MS linkage analysis, and site-directed mutagenesis","pmids":["18202552"],"confidence":"Medium","gaps":["Single lab","Direct cell-cycle substrates of the K63 chains not identified"]},{"year":2011,"claim":"Extended the complex to vertebrate p53-mediated DNA damage signaling, showing Mms2 (not Uev1) restrains p53 effector expression.","evidence":"Zebrafish morpholino knockdown with RT-PCR of p21/mdm2, in vitro K63 chain assembly, and GST pulldown of Ubc13-p53","pmids":["22055568"],"confidence":"Medium","gaps":["Mechanistic link between K63 chains and p53 effector regulation undefined","Single vertebrate model"]},{"year":2012,"claim":"Defined RNF8 as a dimeric E3 partner that engages Ubc13/Mms2 to build K63 chains at double-strand breaks, contrasting with monomeric RNF168.","evidence":"Crystal structure of the RNF8/Ubc13/Mms2 ternary complex with mutagenesis and in vitro ubiquitylation","pmids":["22589545"],"confidence":"High","gaps":["Single lab","In-cell choreography of RNF8 versus other E3s not resolved structurally"]},{"year":2018,"claim":"Revealed a privileged sensor cysteine on Ube2V2 that, when electrophile-modified, allosterically hyperactivates Ubc13 and amplifies H2AX-dependent DNA damage signaling.","evidence":"G-REX in vivo cysteine profiling, mass spectrometry, in vitro K63 ubiquitination, and γH2AX DDR readout","pmids":["29532025"],"confidence":"Medium","gaps":["Single lab","Physiological electrophile(s) and in vivo significance not established"]},{"year":2020,"claim":"Uncovered a non-repair role for Ubc13-Mms2 in K63-dependent membrane protein sorting via the MVB pathway with FYVE-RING E3 partners.","evidence":"Yeast deletion/epistasis genetics, fluorescence trafficking microscopy, and genetic E3-partner identification (Pib1)","pmids":["32265276"],"confidence":"Medium","gaps":["No in vitro reconstitution of the trafficking pathway","Conservation in mammals untested here"]},{"year":2023,"claim":"Showed Mms2 abundance drives Ubc13-independent, Ubc4/Rsp5/Not4-dependent mutagenesis and modulates Polδ catalytic subunit levels, revealing dosage-dependent functions beyond the canonical complex.","evidence":"Yeast genetic epistasis with ubc13Δ/ubc4Δ/rsp5/not4/rev3Δ/rev1Δ/pcna-K164R, Western blotting for Pol3, and spontaneous mutagenesis assays","pmids":["36934633"],"confidence":"Medium","gaps":["Ubc4-dependent pathway not reconstituted in vitro","Mechanism controlling Pol3 levels undefined"]},{"year":2025,"claim":"Proposed a tumor-relevant role in which the UBE2V2 ortholog cooperates with APC/C to degrade Cyclin A and counteract oncogenic Ras-driven division stress.","evidence":"Drosophila genetic screen with Ras, knockdown/overexpression, and human colorectal xenografts in nude mice (preprint)","pmids":[],"confidence":"Low","gaps":["Preprint; biochemical APC/C-Cyclin A degradation not reconstituted","Direct human UBE2V2 mechanism in this pathway not demonstrated"]},{"year":null,"claim":"How UBE2V2's dosage-dependent, Ubc13-independent activities and its electrophile sensor cysteine are regulated and integrated with canonical K63 repair signaling in mammalian cells remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No mammalian reconstitution of the Ubc4/Rsp5-dependent or APC/C-linked activities","Physiological electrophile triggers of the sensor cysteine unknown","Quantitative partitioning of UBE2V2 among PRR, DSB, trafficking, and cell-cycle roles undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,3,9,14]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[3,4,8]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[7,15]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[9,11]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[0,1,9,14]},{"term_id":"R-HSA-69306","term_label":"DNA Replication","supporting_discovery_ids":[16,17]}],"complexes":["Ubc13-Mms2 (UBE2N-UBE2V2) heterodimer","RNF8/Ubc13/Mms2 ternary complex"],"partners":["UBE2N","SHPRH","RNF8","RAD5","CHFR","TP53"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q15819","full_name":"Ubiquitin-conjugating enzyme E2 variant 2","aliases":["DDVit 1","Enterocyte differentiation-associated factor 1","EDAF-1","Enterocyte differentiation-promoting factor 1","EDPF-1","MMS2 homolog","Vitamin D3-inducible protein"],"length_aa":145,"mass_kda":16.4,"function":"Has no ubiquitin ligase activity on its own. The UBE2V2/UBE2N heterodimer catalyzes the synthesis of non-canonical poly-ubiquitin chains that are linked through 'Lys-63'. This type of poly-ubiquitination does not lead to protein degradation by the proteasome. Mediates transcriptional activation of target genes. Plays a role in the control of progress through the cell cycle and differentiation. Plays a role in the error-free DNA repair pathway and contributes to the survival of cells after DNA damage","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q15819/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/UBE2V2","classification":"Not Classified","n_dependent_lines":13,"n_total_lines":1208,"dependency_fraction":0.01076158940397351},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/UBE2V2","total_profiled":1310},"omim":[{"mim_id":"608048","title":"SNF2, LINKER HISTONE, PHD FINGER, RING FINGER, AND HELICASE DOMAINS-CONTAINING PROTEIN; SHPRH","url":"https://www.omim.org/entry/608048"},{"mim_id":"603679","title":"UBIQUITIN-CONJUGATING ENZYME E2 N; UBE2N","url":"https://www.omim.org/entry/603679"},{"mim_id":"603001","title":"UBIQUITIN-CONJUGATING ENZYME E2 V2; UBE2V2","url":"https://www.omim.org/entry/603001"},{"mim_id":"602995","title":"UBIQUITIN-CONJUGATING ENZYME E2 V1; UBE2V1","url":"https://www.omim.org/entry/602995"},{"mim_id":"602355","title":"TNF RECEPTOR-ASSOCIATED FACTOR 6; TRAF6","url":"https://www.omim.org/entry/602355"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/UBE2V2"},"hgnc":{"alias_symbol":["UEV-2","DDVit-1","EDPF-1","MMS2","UEV2","EDPF1","DDVIT1","EDAF-1"],"prev_symbol":[]},"alphafold":{"accession":"Q15819","domains":[{"cath_id":"3.10.110.10","chopping":"10-126","consensus_level":"high","plddt":97.0134,"start":10,"end":126}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15819","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q15819-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q15819-F1-predicted_aligned_error_v6.png","plddt_mean":94.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=UBE2V2","jax_strain_url":"https://www.jax.org/strain/search?query=UBE2V2"},"sequence":{"accession":"Q15819","fasta_url":"https://rest.uniprot.org/uniprotkb/Q15819.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q15819/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15819"}},"corpus_meta":[{"pmid":"10089880","id":"PMC_10089880","title":"Noncanonical MMS2-encoded ubiquitin-conjugating enzyme functions in assembly of novel polyubiquitin chains for DNA repair.","date":"1999","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/10089880","citation_count":673,"is_preprint":false},{"pmid":"16980971","id":"PMC_16980971","title":"Mms2-Ubc13 covalently bound to ubiquitin reveals the structural basis of linkage-specific polyubiquitin chain formation.","date":"2006","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/16980971","citation_count":290,"is_preprint":false},{"pmid":"11440714","id":"PMC_11440714","title":"Molecular insights into polyubiquitin chain assembly: crystal structure of the Mms2/Ubc13 heterodimer.","date":"2001","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/11440714","citation_count":270,"is_preprint":false},{"pmid":"9576943","id":"PMC_9576943","title":"MMS2, encoding a ubiquitin-conjugating-enzyme-like protein, is a member of the yeast error-free postreplication repair pathway.","date":"1998","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/9576943","citation_count":224,"is_preprint":false},{"pmid":"17108083","id":"PMC_17108083","title":"Human SHPRH is a ubiquitin ligase for Mms2-Ubc13-dependent polyubiquitylation of proliferating cell nuclear antigen.","date":"2006","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/17108083","citation_count":200,"is_preprint":false},{"pmid":"16129784","id":"PMC_16129784","title":"Distinct regulation of Ubc13 functions by the two ubiquitin-conjugating enzyme variants Mms2 and Uev1A.","date":"2005","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/16129784","citation_count":151,"is_preprint":false},{"pmid":"11884624","id":"PMC_11884624","title":"Requirement of RAD5 and MMS2 for postreplication repair of UV-damaged DNA in Saccharomyces cerevisiae.","date":"2002","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/11884624","citation_count":144,"is_preprint":false},{"pmid":"11504715","id":"PMC_11504715","title":"Noncovalent interaction between ubiquitin and the human DNA repair protein Mms2 is required for Ubc13-mediated polyubiquitination.","date":"2001","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11504715","citation_count":115,"is_preprint":false},{"pmid":"16908531","id":"PMC_16908531","title":"Mms2-Ubc13-dependent and -independent roles of Rad5 ubiquitin ligase in postreplication repair and translesion DNA synthesis in Saccharomyces cerevisiae.","date":"2006","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/16908531","citation_count":93,"is_preprint":false},{"pmid":"9705497","id":"PMC_9705497","title":"The products of the yeast MMS2 and two human homologs (hMMS2 and CROC-1) define a structurally and functionally conserved Ubc-like protein family.","date":"1998","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/9705497","citation_count":90,"is_preprint":false},{"pmid":"12569095","id":"PMC_12569095","title":"An NMR-based model of the ubiquitin-bound human ubiquitin conjugation complex Mms2.Ubc13. 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A ubc13 strain is UV sensitive, and single, double, and triple mutants of UBC13, MMS2, and ubiquitin ubiK63R display comparable UV sensitivity, establishing the Mms2p/Ubc13p complex as essential for assembling K63-linked polyubiquitin chains used in DNA repair signaling.\",\n      \"method\": \"In vitro ubiquitin chain assembly assay with purified components; yeast genetics (epistasis with ubc13, mms2, ubiK63R mutants); UV sensitivity phenotyping\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted in vitro chain assembly, paired with rigorous yeast genetic epistasis; foundational study replicated by multiple subsequent labs\",\n      \"pmids\": [\"10089880\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"MMS2 encodes a Ubc-like protein that lacks E2 (ubiquitin-conjugating) activity but functions specifically in the error-free postreplication repair (PRR) pathway in yeast. Genetic analysis showed mms2 is hypostatic to rad6 and rad18, synergistic with rev3, and proficient in UV mutagenesis, placing MMS2 in the error-free branch of the RAD6 pathway parallel to the REV3 mutagenesis pathway.\",\n      \"method\": \"Functional complementation cloning; genetic epistasis analysis (double/triple mutant UV sensitivity); UV-induced mutagenesis assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic epistasis with multiple pathway members, replicated in subsequent studies\",\n      \"pmids\": [\"9576943\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Crystal structure of the Mms2/Ubc13 heterodimer reveals the Ubc13 active site at the intersection of two channels that are potential binding sites for two substrate ubiquitins. Mutations destabilizing the heterodimer interface confer marked UV sensitivity, demonstrating the intact heterodimer is necessary for DNA repair.\",\n      \"method\": \"X-ray crystallography; site-directed mutagenesis of heterodimer interface; yeast UV sensitivity assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with mutagenesis and in vivo functional validation\",\n      \"pmids\": [\"11440714\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Human Mms2 and Ubc13 form a stable heterodimer capable of transferring ubiquitin specifically to Lys63 of an untethered ubiquitin, producing diubiquitin. NMR mapping identified a surface of the acceptor ubiquitin that interacts with Mms2 in both monomeric and heterodimeric forms, with the C-terminal tail of ubiquitin not participating, supporting the model that Mms2 orients acceptor ubiquitin to position Lys63 proximal to the Ubc13 active site.\",\n      \"method\": \"In vitro ubiquitin chain assembly with purified human Mms2 and Ubc13; 1H-15N HSQC NMR mapping of ubiquitin-Mms2 and ubiquitin-Ubc13 interaction surfaces\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with purified human proteins plus NMR structural mapping, multiple orthogonal methods\",\n      \"pmids\": [\"11504715\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"NMR-based structural model of the human Ubc13·Mms2 heterodimer bound to acceptor and donor ubiquitin reveals the molecular basis of K63-specific chain synthesis: Mms2 binds acceptor ubiquitin non-covalently while Ubc13 carries donor ubiquitin as a thioester, positioning Lys63 of acceptor ubiquitin at the Ubc13 active site.\",\n      \"method\": \"2D 1H-15N NMR chemical shift mapping of subunit-subunit and subunit-ubiquitin interactions; unbiased computational docking using NMR-derived restraints\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR-based structural model with multiple interaction surfaces mapped using orthogonal approaches; consistent with crystal structure from separate lab\",\n      \"pmids\": [\"12569095\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Mms2-Ile57 and ubiquitin-Ile44 are critical molecular determinants of the Mms2–acceptor ubiquitin interaction. Mutating either side chain to alanine causes 10–20-fold inhibition of K63-linked chain synthesis in vitro by compromising acceptor ubiquitin binding to Mms2, and abolishes error-free lesion bypass in vivo in yeast.\",\n      \"method\": \"Site-directed mutagenesis; in vitro K63-linked chain assembly assay; yeast error-free bypass assay (DNA damage sensitivity)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro mutagenesis combined with quantitative binding and in vivo functional data; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"15772086\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"A single 'key' residue of Mms2 inserts into a complementary pocket of Ubc13 to determine interface specificity. Structure-based mutagenesis identified critical residues at the Ubc13–Mms2 interface; disrupting these contacts abrogates heterodimer formation, ubiquitin conjugation, and functional complementation of DNA repair, explaining why Mms2 forms a specific complex with Ubc13 but not other E2s.\",\n      \"method\": \"Structure-based mutagenesis; yeast two-hybrid; GST pulldown; surface plasmon resonance; functional complementation of yeast mms2 mutant; in vitro ubiquitin conjugation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple orthogonal binding assays (Y2H, pulldown, SPR) combined with in vitro activity and in vivo complementation\",\n      \"pmids\": [\"15749714\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The two mammalian UEV proteins, Mms2 and Uev1A, differentially modulate the length of Ubc13-mediated K63-linked polyubiquitin chains. Ubc13–Mms2 is required for DNA damage repair but not NF-κB activation, whereas Ubc13–Uev1A is involved in NF-κB activation but not DNA repair, demonstrating that alternative UEV pairing directs Ubc13 to distinct cellular processes.\",\n      \"method\": \"Structural comparison; in vitro ubiquitin chain length assays; siRNA knockdown with functional assays (UV sensitivity/DNA repair; NF-κB reporter assays)\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal functional assays (repair + NF-κB) combined with biochemical chain assembly; directly distinguishes the two paralogs\",\n      \"pmids\": [\"16129784\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Crystal structure of Mms2–Ubc13 covalently linked to donor ubiquitin (UEV-E2-Ub intermediate) reveals that an acceptor-ubiquitin binding site on Mms2 (from an adjacent complex in the crystal) positions Lys63 of acceptor ubiquitin at the Ubc13 active site, providing the structural basis for K63 linkage specificity in polyubiquitin chain elongation.\",\n      \"method\": \"X-ray crystallography of covalent Mms2–Ubc13–ubiquitin intermediate\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structure of catalytic intermediate, independently consistent with prior NMR and crystal structures from other labs\",\n      \"pmids\": [\"16980971\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Human SHPRH physically interacts with the Mms2–Ubc13 complex and acts as the E3 ubiquitin ligase indispensable for Mms2–Ubc13-dependent K63-linked polyubiquitylation of PCNA, placing SHPRH as the E3 partner of Mms2–Ubc13 in human error-free PRR.\",\n      \"method\": \"Co-immunoprecipitation; in vitro ubiquitylation assay with purified components; siRNA knockdown of SHPRH with PCNA ubiquitylation readout\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro reconstitution of PCNA polyubiquitylation plus reciprocal co-IP and siRNA knockdown; multiple orthogonal methods\",\n      \"pmids\": [\"17108083\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"NMR solution structure of human Mms2 bound to ubiquitin reveals the molecular basis for the non-covalent Mms2–ubiquitin interaction that positions acceptor ubiquitin for K63-linked chain synthesis.\",\n      \"method\": \"Solution-state NMR spectroscopy (structure determination of Mms2–ubiquitin complex)\",\n      \"journal\": \"Journal of biomolecular NMR\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structure determination providing atomic-resolution view of the interface; consistent with prior crystal and NMR data\",\n      \"pmids\": [\"16518696\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"AT2 receptor signaling in neurons induces MMS2 (UBE2V2) expression via the ATIP–SHP-1 cascade. ATIP and SHP-1 translocate to the nucleus after forming a complex upon AT2 receptor stimulation; increased MMS2 expression mediates inhibitor of DNA binding 1 (Id1) proteolysis and promotes DNA repair, and siRNA knockdown of MMS2 abolishes neurite outgrowth and synapse formation.\",\n      \"method\": \"siRNA knockdown of MMS2; overexpression and dominant-negative SHP-1; co-immunoprecipitation of ATIP–SHP-1 complex; nuclear fractionation; RT-PCR of MMS2 expression; neurite outgrowth assay; synapse formation assay\",\n      \"journal\": \"Molecular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — siRNA knockdown with clear phenotypic readouts (no neurite outgrowth) and Co-IP of upstream partners; single lab, functional link is indirect\",\n      \"pmids\": [\"17068200\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Chfr ubiquitin ligase catalyzes formation of non-canonical K63-linked polyubiquitin chains using Ubc13–Mms2 as the ubiquitin-conjugating enzyme, rather than targeting proteins for proteasomal degradation; this activity is proposed to signal mitotic stress.\",\n      \"method\": \"In vitro ubiquitin ligase assay; ubiquitin chain linkage characterization\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — in vitro reconstitution of K63-chain formation, single lab, single method for the chain linkage characterization\",\n      \"pmids\": [\"14562038\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Two residues of human Mms2 cooperatively interact with ubiquitin to promote Ubc13-mediated K63-linked polyubiquitin chain formation: each single mutation reduces binding affinity, but the double mutation severely reduces ubiquitin binding and abolishes polyubiquitin chain formation in vitro and in vivo (yeast double mutant shows complete loss of MMS2 function).\",\n      \"method\": \"Site-directed mutagenesis; in vitro polyubiquitin chain assembly assay; binding assays; yeast functional complementation\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis combined with in vitro chain assembly and in vivo yeast functional assays; consistent with prior structural data\",\n      \"pmids\": [\"17964296\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"RNF8 dimerizes and binds to Ubc13/Mms2, stimulating K63-linked ubiquitin chain formation at DNA double-strand breaks; the crystal structure of the RNF8/Ubc13/Mms2 ternary complex reveals that an RNF8 coiled-coil mediates dimerization and that disrupting RNF8/Ubc13 binding surfaces or truncating the coiled-coil reduces ubiquitylation. In contrast, RNF168 RING domain is monomeric and does not catalyze K63 polyubiquitylation with Ubc13/Mms2.\",\n      \"method\": \"X-ray crystallography of RNF8/Ubc13/Mms2 ternary complex; site-directed mutagenesis; in vitro ubiquitylation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure of ternary complex plus mutagenesis and in vitro activity assays; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"22589545\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Ube2V2 contains a functionally privileged sensor cysteine that can be modified by reactive electrophiles in a non-enzyme-catalyzed manner. This modification allosterically hyperactivates Ube2V2's binding partner Ube2N (Ubc13), promoting K63-linked client ubiquitination and stimulating H2AX-dependent DNA damage response.\",\n      \"method\": \"G-REX electrophile-release technology for in vivo cysteine identification; mass spectrometry; in vitro K63-linked ubiquitination assays; γH2AX DNA damage response readout\",\n      \"journal\": \"ACS central science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — novel chemical biology approach (G-REX) combined with in vitro ubiquitination activity assays and cellular DDR readout; single lab, multiple methods\",\n      \"pmids\": [\"29532025\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Rad5 protein and the Mms2–Ubc13 ubiquitin-conjugating enzyme complex are both required for postreplication repair of UV-damaged DNA in yeast: discontinuities in newly synthesized DNA strands from UV-damaged templates are not repaired in rad5Δ or mms2Δ mutants, indicating these components act in the same pathway for error-free gap filling.\",\n      \"method\": \"Yeast genetic analysis; alkaline sucrose gradient sedimentation to detect DNA discontinuities in rad5Δ and mms2Δ strains\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct biochemical measurement of DNA repair intermediates combined with genetic epistasis; replicated in subsequent studies\",\n      \"pmids\": [\"11884624\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The Rad18/Rad5/Mms2 polyubiquitination pathway is important for replication completion in yeast: PCNA-K164R (blocking ubiquitination) and mms2Δ/rad5Δ mutations impair replication in rfc5-1 mutants, indicating Mms2-dependent PCNA polyubiquitination promotes a template-switch type of DNA synthesis during replication stress.\",\n      \"method\": \"Yeast genetics; PCNA mutant (K164R) analysis; epistasis analysis combining mms2Δ, rad5Δ, siz1Δ, rad18Δ mutations with replication-defective alleles; growth assays\",\n      \"journal\": \"Genes to cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with defined alleles and replication readout; single lab, no direct biochemical confirmation of mechanism\",\n      \"pmids\": [\"15507115\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Human MMS2 (hMMS2/UBE2V2) and its close paralog CROC-1 functionally complement yeast mms2 mutations for DNA damage sensitivity and spontaneous mutagenesis, demonstrating conservation of Mms2 function. Both yeast MMS2 and human hMMS2 also transactivate a c-fos–CAT reporter gene in Rat-1 cells.\",\n      \"method\": \"Functional complementation of yeast mms2 mutant; DNA damage sensitivity assays; mutagenesis assays; transient co-transfection reporter assay (c-fos–CAT)\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional complementation across species with DNA repair and mutagenesis assays; single lab\",\n      \"pmids\": [\"9705497\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Yeast Chfr homologs Chf1/Chf2 require Ubc13/Mms2 for G2 cell-cycle delay but not for Chf protein turnover; Ubc4 mediates G1 delay and Chf protein turnover. Reconstituted in vitro ubiquitination and tandem MS characterization of ubiquitin chain linkages showed that Ubc13/Mms2-dependent modifications are a distinct subset of those catalyzed by Ubc4, with site-specific mutagenesis confirming different functional consequences.\",\n      \"method\": \"Genetic analysis in yeast; in vitro ubiquitination reconstitution with purified components; tandem mass spectrometry linkage analysis; site-directed mutagenesis of ubiquitination sites\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro reconstitution + MS linkage analysis + genetic validation; single lab\",\n      \"pmids\": [\"18202552\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Zebrafish Mms2 (DrMms2) forms a stable complex with DrUbc13 and promotes K63-linked polyubiquitination in vitro. Morpholino knockdown of DrMms2 (but not DrUev1) enhances spontaneous and DNA-damage-induced expression of p53 effectors p21 and mdm2 in zebrafish embryos. Additionally, DrUbc13 specifically binds p53 in vitro, linking the Mms2–Ubc13 complex to the p53-mediated DNA damage response.\",\n      \"method\": \"Zebrafish morpholino knockdown; in vitro K63-linked polyubiquitination assay; in vitro GST pulldown (DrUbc13–p53 binding); RT-PCR of p53 target genes (p21, mdm2)\",\n      \"journal\": \"DNA repair\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — morpholino KD with molecular readout plus in vitro binding assay; single lab, vertebrate model\",\n      \"pmids\": [\"22055568\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Ubc13–Mms2 contributes to K63-linked polyubiquitylation in membrane protein sorting to the yeast vacuole via the multivesicular body (MVB) pathway. Genetic analysis identified FYVE-RING finger E3 proteins (including Pib1) as cognate E3 partners for Ubc13–Mms2 in membrane trafficking, revealing a role for Ubc13–Mms2 in membrane protein sorting beyond DNA repair.\",\n      \"method\": \"Yeast genetics (deletion analysis, epistasis); fluorescence microscopy of membrane protein trafficking; identification of E3 partners by genetic interaction screening\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with clear pathway placement in MVB sorting; single lab, genetic methods without in vitro reconstitution of the new pathway\",\n      \"pmids\": [\"32265276\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Mms2 overproduction in yeast causes a spontaneous mutator effect that is independent of Ubc13 but requires Ubc4, the HECT E3 Rsp5, and RING E3 Not4, as well as error-prone polymerases ζ and Rev1 and PCNA K164 ubiquitination. Mms2 abundance also influences Pol3 (Polδ catalytic subunit) cellular levels: loss of Mms2 increases Pol3 abundance, while Mms2 overproduction decreases Pol3 levels.\",\n      \"method\": \"Yeast genetics; Western blotting for Pol3 levels; epistasis analysis with ubc13Δ, ubc4Δ, rsp5, not4, rev3Δ, rev1Δ, and pcna-K164R mutants; spontaneous mutagenesis assays\",\n      \"journal\": \"DNA repair\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic genetic epistasis combined with protein level measurements; single lab, no in vitro reconstitution of the Ubc4-dependent pathway\",\n      \"pmids\": [\"36934633\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In Drosophila, Uev1A (ortholog of UBE2V2) collaborates with the E3 APC/C complex to mediate proteasomal degradation of Cyclin A, thereby protecting polyploid cells from aberrant division stress induced by oncogenic Ras. Overexpression of human UBE2V2 mitigates oncogenic Ras-induced nurse cell death, and UBE2V2 counteracts oncogenic Ras-driven tumorigenesis in human colorectal tumor xenografts in nude mice.\",\n      \"method\": \"Drosophila genome-wide genetic screen; Drosophila knockdown/overexpression with oncogenic Ras; human colorectal tumor xenograft in nude mice; Cyclin A degradation assay (Uev1A + APC/C reconstitution implied by genetic and xenograft evidence)\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — preprint; Drosophila genetic screen with xenograft validation; APC/C-Cyclin A degradation mechanism is supported genetically but biochemical reconstitution details are not described in abstract\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"UBE2V2 (Mms2) is a catalytically inactive ubiquitin-conjugating enzyme variant (UEV) that forms a stable heterodimer with the E2 enzyme Ubc13 (UBE2N); within this complex, UBE2V2 non-covalently binds acceptor ubiquitin and orients its Lys63 toward the Ubc13 active site, thereby directing exclusive synthesis of K63-linked polyubiquitin chains that serve as non-proteolytic signals in error-free postreplication DNA repair (via PCNA polyubiquitylation with E3s SHPRH/Rad5) and DNA double-strand break response (via RNF8); in contrast to its paralog Uev1A/UBE2V1, which directs Ubc13 toward NF-κB activation, UBE2V2 specifically supports DNA damage tolerance; additionally, an allosteric sensor cysteine on UBE2V2 can be modified by electrophiles to hyperactivate Ubc13 and stimulate H2AX-dependent DNA damage signaling.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"UBE2V2 (Mms2) is a catalytically inactive ubiquitin-conjugating enzyme variant (UEV) that functions as the specificity-determining partner of the E2 enzyme Ubc13/UBE2N in the assembly of Lys63-linked polyubiquitin chains used as non-proteolytic DNA repair signals [#0, #1]. UBE2V2 forms an obligate, specific heterodimer with Ubc13: a single key Mms2 residue inserts into a complementary Ubc13 pocket to enforce pairing exclusivity, and disrupting this interface abolishes heterodimer formation, ubiquitin conjugation, and DNA repair function [#6, #2]. Within the complex UBE2V2 binds an acceptor ubiquitin non-covalently while Ubc13 carries the donor ubiquitin as a thioester, orienting acceptor Lys63 at the Ubc13 active site to dictate strict K63 linkage; this geometry was resolved through NMR and crystal structures of the heterodimer and its covalent UEV-E2-Ub intermediate, and the Mms2-Ile57/ubiquitin-Ile44 contact is a critical determinant of acceptor binding and chain synthesis [#4, #8, #5, #10]. The Ubc13-Mms2 complex operates in the error-free branch of postreplication repair, where it acts with the E3 ligases SHPRH and Rad5 to catalyze K63-linked polyubiquitylation of PCNA, promoting template-switch DNA synthesis during replication stress [#9, #16, #17], and at DNA double-strand breaks it pairs with the dimeric E3 RNF8 to generate K63 chains [#14]. UEV partner choice routes Ubc13 to distinct outcomes: Mms2/UBE2V2 supports DNA repair but not NF-\\u03baB activation, the reverse of its paralog Uev1A/UBE2V1 [#7]. A privileged sensor cysteine on UBE2V2 can be covalently modified by reactive electrophiles to allosterically hyperactivate Ubc13 and stimulate H2AX-dependent DNA damage signaling [#15].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established that MMS2 is a Ubc-like protein lacking E2 activity that acts specifically in the error-free postreplication repair branch, distinguishing it from mutagenic lesion bypass.\",\n      \"evidence\": \"Complementation cloning and genetic epistasis (hypostatic to rad6/rad18, synergistic with rev3) with UV mutagenesis assays in yeast\",\n      \"pmids\": [\"9576943\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the molecular partner or biochemical activity of Mms2\", \"No chain-linkage information\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Identified that Mms2 acts through a heteromeric complex with Ubc13 to assemble K63-linked chains, linking the genetic repair phenotype to a specific biochemical activity.\",\n      \"evidence\": \"Reconstituted in vitro chain assembly with purified components plus yeast genetic epistasis (ubc13/mms2/ubiK63R) and UV sensitivity phenotyping\",\n      \"pmids\": [\"10089880\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of K63 specificity not yet known\", \"E3 ligase partners and physiological substrates unidentified\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Showed human MMS2 functionally conserves yeast Mms2 repair activity, extending the pathway to mammals.\",\n      \"evidence\": \"Cross-species functional complementation of yeast mms2 with DNA damage/mutagenesis assays and a c-fos\\u2013CAT reporter in Rat-1 cells\",\n      \"pmids\": [\"9705497\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"c-fos transactivation link is correlative and mechanistically undefined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Resolved the heterodimer architecture and demonstrated the intact interface is required for repair, and that the human complex builds K63-specific diubiquitin by orienting acceptor ubiquitin.\",\n      \"evidence\": \"X-ray crystallography of Mms2/Ubc13 with interface mutagenesis and UV assays; in vitro chain assembly and NMR mapping of human Mms2/Ubc13/ubiquitin surfaces\",\n      \"pmids\": [\"11440714\", \"11504715\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Donor-ubiquitin positioning during catalysis not yet visualized\", \"E3 partners still unidentified\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Placed Rad5 together with Mms2-Ubc13 in the same error-free gap-filling pathway, connecting the complex to repair of replication discontinuities.\",\n      \"evidence\": \"Yeast genetics and alkaline sucrose gradient detection of DNA discontinuities in rad5\\u0394/mms2\\u0394 strains\",\n      \"pmids\": [\"11884624\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct biochemical demonstration of Rad5 as the E3 not shown here\", \"PCNA as substrate not yet established in this study\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Provided a complete structural model of how acceptor and donor ubiquitin are jointly positioned to enforce K63 linkage, defining the catalytic logic of the complex.\",\n      \"evidence\": \"NMR chemical-shift mapping and restraint-driven computational docking of the Ubc13\\u00b7Mms2 complex with both ubiquitins\",\n      \"pmids\": [\"12569095\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Model from docking restraints rather than a single crystallized ternary intermediate\", \"Catalytic transition state not captured\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identified Chfr as an E3 that uses Ubc13-Mms2 to build non-degradative K63 chains, broadening the complex's role to mitotic stress signaling.\",\n      \"evidence\": \"In vitro ubiquitin ligase assay with chain-linkage characterization\",\n      \"pmids\": [\"14562038\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single method for linkage determination\", \"Physiological mitotic substrate not defined\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Connected Mms2-dependent PCNA polyubiquitination to template-switch DNA synthesis under replication stress.\",\n      \"evidence\": \"Yeast genetics with PCNA-K164R and mms2\\u0394/rad5\\u0394/rad18\\u0394 epistasis in replication-defective backgrounds\",\n      \"pmids\": [\"15507115\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct biochemical confirmation of the template-switch mechanism\", \"Single lab\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Defined the molecular determinants of acceptor-ubiquitin recognition and interface specificity, explaining both K63 fidelity and exclusive Ubc13 pairing.\",\n      \"evidence\": \"Site-directed mutagenesis (Mms2-Ile57/Ub-Ile44; the 'key' interface residue) with in vitro chain assembly, SPR/Y2H/pulldown binding, and yeast complementation\",\n      \"pmids\": [\"15772086\", \"15749714\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Single-lab mutagenesis studies\", \"Quantitative kinetics of chain elongation not fully resolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Established that UEV partner identity (Mms2 vs Uev1A) routes Ubc13 to distinct cellular pathways, separating DNA repair from NF-\\u03baB activation.\",\n      \"evidence\": \"In vitro chain-length assays plus siRNA knockdown with UV/DNA-repair and NF-\\u03baB reporter readouts\",\n      \"pmids\": [\"16129784\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which partner choice alters chain length not defined\", \"Mammalian E3 specificity for each pathway not detailed here\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Captured the catalytic intermediate by crystallography and an NMR Mms2-ubiquitin structure, confirming how acceptor Lys63 is positioned at the active site during elongation.\",\n      \"evidence\": \"X-ray structure of covalent Mms2-Ubc13-ubiquitin intermediate; solution NMR structure of Mms2-ubiquitin\",\n      \"pmids\": [\"16980971\", \"16518696\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Acceptor positioning inferred from adjacent crystal complex\", \"Dynamics of processive elongation not addressed\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Identified SHPRH as the human E3 partner of Mms2-Ubc13 for K63-linked PCNA polyubiquitylation, completing the mammalian error-free PRR enzyme set.\",\n      \"evidence\": \"Co-IP, in vitro ubiquitylation reconstitution, and SHPRH siRNA knockdown with PCNA ubiquitylation readout\",\n      \"pmids\": [\"17108083\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of SHPRH versus other E3s in cells not quantified\", \"Downstream polymerase-switch step not directly reconstituted\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Linked UBE2V2 to neuronal AT2 receptor signaling, where induced MMS2 promotes Id1 proteolysis, DNA repair, and neurite/synapse formation.\",\n      \"evidence\": \"siRNA knockdown of MMS2 with neurite/synapse phenotyping, Co-IP of the ATIP-SHP-1 complex, nuclear fractionation, and RT-PCR\",\n      \"pmids\": [\"17068200\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional link between MMS2 and the neuronal phenotype is indirect\", \"Single lab\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Demonstrated cooperative two-residue ubiquitin binding by Mms2 is essential, where the double mutant abolishes chain formation and yeast function.\",\n      \"evidence\": \"Site-directed mutagenesis with in vitro chain assembly, binding assays, and yeast complementation\",\n      \"pmids\": [\"17964296\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Single-lab study\", \"Energetic basis of cooperativity not dissected\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Distinguished Ubc13/Mms2-dependent ubiquitination as a separate functional subset from Ubc4-mediated turnover in Chfr-homolog cell-cycle control.\",\n      \"evidence\": \"Yeast genetics, in vitro ubiquitination reconstitution, tandem-MS linkage analysis, and site-directed mutagenesis\",\n      \"pmids\": [\"18202552\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Direct cell-cycle substrates of the K63 chains not identified\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Extended the complex to vertebrate p53-mediated DNA damage signaling, showing Mms2 (not Uev1) restrains p53 effector expression.\",\n      \"evidence\": \"Zebrafish morpholino knockdown with RT-PCR of p21/mdm2, in vitro K63 chain assembly, and GST pulldown of Ubc13-p53\",\n      \"pmids\": [\"22055568\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic link between K63 chains and p53 effector regulation undefined\", \"Single vertebrate model\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defined RNF8 as a dimeric E3 partner that engages Ubc13/Mms2 to build K63 chains at double-strand breaks, contrasting with monomeric RNF168.\",\n      \"evidence\": \"Crystal structure of the RNF8/Ubc13/Mms2 ternary complex with mutagenesis and in vitro ubiquitylation\",\n      \"pmids\": [\"22589545\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Single lab\", \"In-cell choreography of RNF8 versus other E3s not resolved structurally\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Revealed a privileged sensor cysteine on Ube2V2 that, when electrophile-modified, allosterically hyperactivates Ubc13 and amplifies H2AX-dependent DNA damage signaling.\",\n      \"evidence\": \"G-REX in vivo cysteine profiling, mass spectrometry, in vitro K63 ubiquitination, and \\u03b3H2AX DDR readout\",\n      \"pmids\": [\"29532025\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Physiological electrophile(s) and in vivo significance not established\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Uncovered a non-repair role for Ubc13-Mms2 in K63-dependent membrane protein sorting via the MVB pathway with FYVE-RING E3 partners.\",\n      \"evidence\": \"Yeast deletion/epistasis genetics, fluorescence trafficking microscopy, and genetic E3-partner identification (Pib1)\",\n      \"pmids\": [\"32265276\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vitro reconstitution of the trafficking pathway\", \"Conservation in mammals untested here\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showed Mms2 abundance drives Ubc13-independent, Ubc4/Rsp5/Not4-dependent mutagenesis and modulates Pol\\u03b4 catalytic subunit levels, revealing dosage-dependent functions beyond the canonical complex.\",\n      \"evidence\": \"Yeast genetic epistasis with ubc13\\u0394/ubc4\\u0394/rsp5/not4/rev3\\u0394/rev1\\u0394/pcna-K164R, Western blotting for Pol3, and spontaneous mutagenesis assays\",\n      \"pmids\": [\"36934633\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubc4-dependent pathway not reconstituted in vitro\", \"Mechanism controlling Pol3 levels undefined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Proposed a tumor-relevant role in which the UBE2V2 ortholog cooperates with APC/C to degrade Cyclin A and counteract oncogenic Ras-driven division stress.\",\n      \"evidence\": \"Drosophila genetic screen with Ras, knockdown/overexpression, and human colorectal xenografts in nude mice (preprint)\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Preprint; biochemical APC/C-Cyclin A degradation not reconstituted\", \"Direct human UBE2V2 mechanism in this pathway not demonstrated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How UBE2V2's dosage-dependent, Ubc13-independent activities and its electrophile sensor cysteine are regulated and integrated with canonical K63 repair signaling in mammalian cells remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No mammalian reconstitution of the Ubc4/Rsp5-dependent or APC/C-linked activities\", \"Physiological electrophile triggers of the sensor cysteine unknown\", \"Quantitative partitioning of UBE2V2 among PRR, DSB, trafficking, and cell-cycle roles undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 3, 9, 14]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [3, 4, 8]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [7, 15]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [9, 11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [0, 1, 9, 14]},\n      {\"term_id\": \"R-HSA-69306\", \"supporting_discovery_ids\": [16, 17]}\n    ],\n    \"complexes\": [\"Ubc13-Mms2 (UBE2N-UBE2V2) heterodimer\", \"RNF8/Ubc13/Mms2 ternary complex\"],\n    \"partners\": [\"UBE2N\", \"SHPRH\", \"RNF8\", \"RAD5\", \"CHFR\", \"TP53\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}