{"gene":"HERC2","run_date":"2026-06-10T01:55:22","timeline":{"discoveries":[{"year":2009,"finding":"HERC2 forms a complex with the ubiquitin ligase RNF8 in response to ionising radiation; this interaction requires IR-inducible phosphorylation of HERC2 at Thr4827, which binds to the FHA domain of RNF8. HERC2 facilitates assembly of the ubiquitin-conjugating enzyme Ubc13 with RNF8, promoting DNA damage-induced formation of Lys63-linked ubiquitin chains. HERC2 also interacts with and maintains levels of RNF168, and HERC2 knockdown abrogates ubiquitin-dependent retention of 53BP1, RAP80, and BRCA1 at damage sites.","method":"Co-immunoprecipitation, phosphorylation mapping, siRNA knockdown, IR-induced focus formation assays, radiosensitivity assays","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, phospho-site identification, functional epistasis with multiple repair factors, replicated across multiple orthogonal readouts in a focused study","pmids":["20023648"],"is_preprint":false},{"year":2010,"finding":"HERC2 acts as an E3 ubiquitin ligase that targets BARD1-uncoupled BRCA1 for degradation. The HECT domain of HERC2 interacts with an N-terminal degron domain in BRCA1, and ubiquitination depends on Cys4762 (catalytic site) of HERC2. HERC2 depletion restores BRCA1 expression and G2/M checkpoint activity when BARD1 is depleted; BARD1 protects BRCA1 from HERC2-mediated ubiquitination.","method":"Co-immunoprecipitation, in vitro ubiquitination assay, catalytic mutant analysis (Cys4762), siRNA knockdown, cell-cycle checkpoint assays","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro ubiquitination assay with catalytic mutant, Co-IP, and functional genetic epistasis in a single focused study","pmids":["20631078"],"is_preprint":false},{"year":2010,"finding":"HERC2 ubiquitin ligase mediates circadian oscillation of the NER factor XPA in mouse liver tissue extracts. HERC2 promotes XPA ubiquitination and degradation, and this is regulated in concert with transcriptional control by core circadian clock proteins including cryptochrome.","method":"Tissue extract repair assays (timed), Western blot for XPA oscillation, functional ubiquitination in extracts","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional assay in tissue extracts at multiple time points with mechanistic attribution to HERC2, single lab","pmids":["20304803"],"is_preprint":false},{"year":2011,"finding":"HERC2 stimulates the ubiquitin-protein ligase activity of E6AP (UBE3A) in vitro and in cells. The interaction is mediated by the RCC1-like domain 2 (RLD2) of HERC2 and residues 150-200 of E6AP. This stimulatory effect does not require the ubiquitin ligase activity of HERC2 itself.","method":"Co-immunoprecipitation, domain mapping, in vitro ubiquitination assay, cell-based ubiquitination assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of E6AP stimulation with domain mapping and catalytic-dead HERC2 controls, multiple orthogonal methods","pmids":["21493713"],"is_preprint":false},{"year":2011,"finding":"HERC2 interacts with Claspin and is a component of the DNA replication fork complex. HERC2 depletion alleviated slow replication fork progression in Claspin-deficient cells, suppressed enhanced origin firing, and decreased MCM2 phosphorylation. In a HERC2-dependent manner, aphidicolin treatment enhanced MCM2 phosphorylation.","method":"Co-immunoprecipitation, DNA fiber assay, siRNA knockdown, phospho-MCM2 Western blot","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus functional double-knockdown epistasis and replication assays, single lab","pmids":["21775519"],"is_preprint":false},{"year":2012,"finding":"HERC2 and RNF168 are SUMOylated at DNA double-strand break sites in a PIAS4-dependent manner. SUMOylation of HERC2 is required for its DSB-induced association with RNF8 and for stabilizing the RNF8-Ubc13 complex. The ZZ zinc finger of HERC2 functions as a novel SUMO-specific binding module; together with concomitant phosphorylation at T4827, it promotes RNF8 binding.","method":"Co-immunoprecipitation, domain mutagenesis, SUMO-specific binding assays, siRNA knockdown of PIAS4, focus formation assays at DSBs","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — biochemical binding domain mapping with ZZ finger SUMO module identification, multiple orthogonal methods (Co-IP, mutagenesis, focus formation), single focused study","pmids":["22508508"],"is_preprint":false},{"year":2012,"finding":"HERC2 and NEURL4 are novel interaction partners of the centrosomal protein CP110. HERC2 and NEURL4 localize to the centrosome, and interfering with their function causes aberrant filamentous pericentriolar material structures. NEURL4 is a substrate of HERC2, and the NEURL4-HERC2 complex participates in ubiquitin-dependent regulation of centrosome architecture. CP110 binding to HERC2 (mediated via nonoverlapping NEURL4 regions) is required for normal centrosome integrity.","method":"Interaction proteomics (AP-MS), high-resolution imaging, RNAi, structure-function analysis with RNAi-resistant transgene","journal":"Molecular & cellular proteomics : MCP","confidence":"High","confidence_rationale":"Tier 2 / Strong — AP-MS identification validated with RNAi rescue and high-resolution functional imaging, multiple orthogonal approaches","pmids":["22261722"],"is_preprint":false},{"year":2012,"finding":"ATR-mediated phosphorylation of XPA at Ser196 enhances XPA stability by inhibiting HERC2-mediated ubiquitination and degradation. Upon UV damage, ATR facilitates HERC2 dissociation from XPA; phosphomimetic S196D shows reduced HERC2 binding and decreased ubiquitination, while S196A shows persistent HERC2 association and enhanced ubiquitination.","method":"Co-immunoprecipitation, site-directed mutagenesis (S196D/S196A), ubiquitination assay, XPA-deficient cell complementation, chromatin retention assay","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1 / Strong — phospho-mutant reconstitution in XPA-null cells with Co-IP, ubiquitination assay, and chromatin fractionation, multiple orthogonal methods","pmids":["23178497"],"is_preprint":false},{"year":2014,"finding":"HERC2 interacts with p53 via its CPH domain (binding the last 43 amino acids of p53). HERC2 depletion reduces p53 transcriptional activity and p53 oligomerization without affecting p53 stability or MDM2 activity. The HERC2-p53 interaction requires the p53 tetramerization domain, and HERC2 promotes p53 oligomerization as shown by cross-linking assays.","method":"Co-immunoprecipitation, domain mapping, RNA interference, transcriptional reporter assays, chemical cross-linking, focus formation assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — domain-mapped Co-IP, cross-linking oligomerization assay, functional transcription assay, multiple orthogonal methods in a single focused study","pmids":["24722987"],"is_preprint":false},{"year":2014,"finding":"HERC2 is the E3 ubiquitin ligase responsible for polyubiquitination and proteasomal degradation of FBXL5, the F-box protein that targets IRP2 for degradation. HERC2 depletion stabilizes FBXL5 and leads to a decrease in intracellular ferrous iron.","method":"Proteomics/Co-IP to identify HERC2-FBXL5 interaction, siRNA knockdown of HERC2, ubiquitination assay, iron measurement","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteomics-guided Co-IP with functional knockdown and iron measurement, single lab","pmids":["24778179"],"is_preprint":false},{"year":2014,"finding":"USP20 deubiquitinates and stabilizes Claspin to promote ATR-Chk1 signaling. Under normal conditions, HERC2 promotes ubiquitination-mediated degradation of USP20. Under replication stress, ATR-mediated phosphorylation of USP20 causes disassociation of HERC2 from USP20, stabilizing USP20 and consequently Claspin to enhance CHK1 checkpoint activation.","method":"DUB screen, Co-immunoprecipitation, phosphorylation mapping, siRNA knockdown, checkpoint signaling assays (Chk1 phosphorylation)","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent papers (25355518, 25326330) using Co-IP, phospho-mapping, and functional checkpoint assays converge on same HERC2-USP20-Claspin mechanism","pmids":["25355518","25326330"],"is_preprint":false},{"year":2014,"finding":"The histone H2A deubiquitinase USP16 interacts with HERC2 via USP16's coiled-coil domain and HERC2's C-terminal HECT domain. HERC2 knockdown affects ubiquitinated H2A levels through USP16. DNA damage increases USP16 levels in a HERC2-dependent manner; elevated USP16 acts as a negative regulator of damage-induced ubiquitin foci formation. USP16 can deubiquitinate both H2A Lys119 and H2A Lys15 in vitro.","method":"Co-immunoprecipitation, domain mapping, siRNA knockdown, in vitro deubiquitination assay, ubiquitin focus formation imaging","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain-mapped Co-IP, in vitro deubiquitination assay, functional knockdown, single lab","pmids":["25305019"],"is_preprint":false},{"year":2014,"finding":"HERC2 degrades the deubiquitinating enzyme USP33 through K48-linked polyubiquitination. p97 (with Ufd1-Npl4 adaptor) is required for post-ubiquitination processing of USP33. Inhibition of p97 causes accumulation of polyubiquitinated USP33.","method":"Quantitative mass spectrometry, Co-immunoprecipitation, p97 knockdown/inhibition, ubiquitination assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS-identified interaction, ubiquitination assay, and functional epistasis with p97 inhibition, single lab","pmids":["24855649"],"is_preprint":false},{"year":2015,"finding":"HERC2 ubiquitin ligase promotes ubiquitin-dependent proteasomal degradation of NCOA4 (the ferritinophagy receptor) in an iron-dependent manner. Excess iron induces an interaction between NCOA4 and HERC2, leading to NCOA4 degradation. NCOA4 abundance is thus under dual control by autophagy and the ubiquitin-proteasome system, with HERC2 acting as the E3 ligase for iron-dependent NCOA4 turnover.","method":"Co-immunoprecipitation, ubiquitination assay, iron-dependent interaction assays, zebrafish erythropoiesis model, cell culture knockdown","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP, ubiquitination assay, iron-dependent interaction, and in vivo zebrafish validation, multiple orthogonal methods, replicated in subsequent papers","pmids":["26436293"],"is_preprint":false},{"year":2016,"finding":"SIRT1 binds to the DOC domain of HERC2 via its amino-terminus; HERC2 then ubiquitinates LKB1 for proteasomal degradation in the nuclear compartment of endothelial cells. Acetylation of LKB1 at K64 triggers formation of the SIRT1/HERC2/LKB1 complex. HERC2 knockdown increases association of LKB1 with the TGFβ1 promoter and abolishes the protective effects of SIRT1 on arterial remodeling.","method":"Co-immunoprecipitation, site-directed mutagenesis (K64), chromatin immunoprecipitation (ChIP-qPCR), siRNA knockdown, lentiviral knockdown in vivo","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with mutagenesis, ChIP, and in vivo lentiviral knockdown, single lab","pmids":["27259994"],"is_preprint":false},{"year":2016,"finding":"Homozygous Herc2 knockout mice are not viable (embryonic lethal). p53 depletion does not rescue lethality, indicating HERC2's essential developmental role is p53-independent. Heterozygous mice show ~50% reduced HERC2 levels, reduced ubiquitin ligase activity and p53 stimulation, and display loss of Purkinje cells with impaired motor coordination. HERC2 is detected in Purkinje cells and autophagosomes/lysosomes accumulate in heterozygous cerebella.","method":"Targeted gene knockout (homozygous lethal), p53 double-knockout epistasis, behavioral analysis, immunohistochemistry of cerebellum, quantitative ubiquitin ligase assay","journal":"Oncotarget","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean Herc2 KO with defined lethality, p53 epistasis experiment, behavioral and histological phenotyping, multiple orthogonal methods","pmids":["27528230"],"is_preprint":false},{"year":2018,"finding":"HERC2 interacts with BLM, WRN RecQ helicases and RPA complexes during S-phase. HERC2 depletion dissociates RPA from BLM and WRN complexes and significantly increases G-quadruplex (G4) DNA formation. In vitro, HERC2 releases RPA onto ssDNA. CRISPR deletion of the HERC2 catalytic ubiquitin-binding site inhibited RPA2 ubiquitination, caused RPA accumulation in helicase complexes, and increased G4 formation—establishing the E3 ligase activity as required for G4 suppression. HERC2 has an epistatic relationship with BLM and WRN in G4 suppression.","method":"Co-immunoprecipitation, in vitro RPA-release assay, CRISPR/Cas9 catalytic-site deletion, G4 immunofluorescence, siRNA epistasis, sensitivity to G4 stabilizers","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro reconstitution, CRISPR catalytic mutant, epistasis analysis, and cellular imaging, multiple orthogonal methods in single focused study","pmids":["30279242"],"is_preprint":false},{"year":2019,"finding":"HERC2 interacts with RPA2 through its C-terminal HECT domain. HERC2 promotes ATR-induced phosphorylation of RPA2 at Ser33 under low-level replication stress, and subsequently mediates ubiquitination and degradation of phosphorylated RPA2. Cells lacking HERC2 catalytic residues constitutively accumulate Ser33-phosphorylated RPA2. This regulatory loop is required for suppression of G-quadruplex DNA structures.","method":"Co-immunoprecipitation, ubiquitination assay, HERC2 catalytic mutant (CRISPR), phospho-RPA2 Western blot, ATR inhibitor epistasis, G4 immunofluorescence","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, catalytic mutant, and functional epistasis, single lab","pmids":["31582797"],"is_preprint":false},{"year":2019,"finding":"MDM2 forms a complex with oligomeric p53, HERC2, and NEURL4. HERC2 knockdown reduces MDM2 mRNA and protein levels by inhibiting MDM2 promoter activation (not by affecting MDM2 protein stability). DNA damage dissociates MDM2 from the p53/HERC2/NEURL4 complex, leading to increased phosphorylation and acetylation of p53 oligomers, which then compete for MDM2 promoter binding.","method":"Co-immunoprecipitation, siRNA knockdown, MDM2 promoter luciferase/reporter assay, Western blot for MDM2 stability","journal":"Molecular oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, promoter reporter assay, functional knockdown, single lab","pmids":["31665549"],"is_preprint":false},{"year":2019,"finding":"NudCL2 interacts with and stabilizes HERC2. NudCL2 knockout leads to centriole amplification, and ectopic HERC2 expression rescues this phenotype while NudCL2 overexpression cannot rescue HERC2 depletion, establishing HERC2 as epistatic downstream of NudCL2. HERC2 controls levels of USP33 (a positive regulator of centriole duplication); USP33 knockdown reverses centriole amplification in both NudCL2 KO and HERC2-depleted cells.","method":"CRISPR/Cas9 knockout, siRNA knockdown, Co-immunoprecipitation, rescue experiments, quantitative proteomics","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR KO with defined phenotype, rescue epistasis, Co-IP, and proteomic identification, single lab","pmids":["31427565"],"is_preprint":false},{"year":2020,"finding":"The ZZ domain of HERC2 (HERC2ZZ) binds to the histone H3 tail and to the N-terminal tail of SUMO1 via the same negatively charged site, with comparable affinities. Crystal structures of HERC2ZZ:H3 and HERC2ZZ:SUMO1 complexes reveal the molecular basis: a critical role for the negatively charged site in capturing A1 of H3, while SUMO1 adopts an α-helical conformation at the same site. HERC2ZZ tolerates common H3 PTMs.","method":"X-ray crystallography, NMR titration, mutagenesis, fluorescence binding assays","journal":"Structure (London, England : 1993)","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures of two complexes validated by NMR, mutagenesis, and fluorescence, multiple orthogonal Tier 1 methods","pmids":["32726574"],"is_preprint":false},{"year":2021,"finding":"HERC2 inactivation (depletion or homozygous HECT deletion) prevents nucleolar localization of BLM and WRN RecQ helicases and inhibits relocalization of BLM to replication stress-induced RPA foci. HERC2 co-localizes with fibrillarin and RNA Pol I subunit RPA194. HERC2 dysfunction enhances the suppressive effects of the rDNA G4 stabilizer CX-5461 on pre-rRNA transcription.","method":"CRISPR/Cas9 HECT domain deletion, siRNA knockdown, immunofluorescence/colocalization, pre-rRNA transcription assay, CX-5461 sensitivity assay","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR deletion with nucleolar localization imaging and functional rRNA transcription assays, single lab","pmids":["33432007"],"is_preprint":false},{"year":2022,"finding":"HERC2 deficiency activates the C-RAF/MKK3/p38 signaling pathway. HERC2 forms molecular complexes with RAF proteins, regulates C-RAF ubiquitylation, and p38 activation in HERC2-deficient cells is RAF/MKK3-dependent. This results in increased resistance to oxidative stress and elevated NRF2 and antioxidant target gene expression, independent of p53.","method":"Patient-derived fibroblast analysis, HERC2 knockdown, Co-immunoprecipitation, proteomics, ubiquitylation assay, RAF/p38 inhibitor epistasis, NRF2 Western blot","journal":"Cellular and molecular life sciences : CMLS","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and ubiquitylation assay with RAF/MKK3 inhibitor epistasis and patient cell validation, single lab","pmids":["36241744"],"is_preprint":false},{"year":2022,"finding":"The ZZ domain of HERC2 (HERC2ZZ) recognizes arginylated substrates via the Nt-R cargo degradation signal. NMR titration and mutagenesis identify a well-defined binding site on HERC2ZZ comprising negatively charged aspartate residues. The DOC domain adjacent to ZZ shows a conformational rearrangement when linked to ZZ. Stimulation of autophagy promotes HERC2 targeting to the proteasome.","method":"NMR titration, X-ray crystallography (HERC2DOC), mutagenesis, immunofluorescence microscopy","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — NMR and crystal structure, but functional autophagy-targeting based on immunofluorescence alone; single lab","pmids":["35411094"],"is_preprint":false},{"year":2023,"finding":"NRF2 maintains HERC2 expression (HERC2 is transcriptionally regulated by NRF2). NRF2 knockout reduces HERC2 levels, causing simultaneous accumulation of ferritin and NCOA4 and apoferritin accumulation in autophagosomes. This elevates the labile iron pool and sensitizes cells to ferroptosis. NRF2 also controls VAMP8 (for autophagosome-lysosome fusion) in the same pathway.","method":"NRF2 knockout (genetic), Western blot, autophagy flux assays, iron measurement, ferroptosis sensitivity assays","journal":"Science advances","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with multiple biochemical readouts confirming NRF2→HERC2→NCOA4 axis, single lab","pmids":["36724221"],"is_preprint":false},{"year":2023,"finding":"HERC2 promotes cancer stemness and PD-L1-mediated immune evasion in hepatocellular carcinoma by activating the JAK2/STAT3 pathway. Mechanistically, HERC2 interacts with the ER-resident phosphatase PTP1B and limits PTP1B translocation from the ER to the ER-plasma membrane junction, thereby reducing PTP1B's inhibitory effect on JAK2 phosphorylation.","method":"HERC2 knockout and overexpression in HCC cells, Co-immunoprecipitation, immunofluorescence for PTP1B localization, DEN-induced mouse liver carcinogenesis (hepatocyte-specific KO), orthotopic transplantation model","journal":"Journal of experimental & clinical cancer research : CR","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, subcellular localization by immunofluorescence, and functional in vivo mouse models, single lab","pmids":["36721234"],"is_preprint":false},{"year":2023,"finding":"HERC2 ubiquitinates CP110 to promote its degradation during ciliogenesis. HERC2 localizes to centriolar satellites. EHD1 regulates the transport of centriolar satellites and HERC2 to the mother centriole during ciliogenesis, and EHD1 is required for CP110 ubiquitination. HERC2 knockdown impairs ciliogenesis.","method":"Co-immunoprecipitation, ubiquitination assay, immunofluorescence (HERC2 to centriolar satellites), siRNA knockdown (HERC2, EHD1), ciliogenesis quantification","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, ubiquitination assay, and localization-function link via siRNA knockdown, single lab","pmids":["37074924"],"is_preprint":false},{"year":2024,"finding":"HERC2 promotes cardiac hypertrophy by directly binding MeCP2 and promoting its K48-linked polyubiquitination and proteasomal degradation. Reduced MeCP2 (a transcriptional suppressor) elevates Lin28a expression, driving hypertrophy. Knockdown of Lin28a attenuates Ang II-induced hypertrophy and abolishes HERC2 overexpression effects.","method":"Co-immunoprecipitation, ubiquitination assay (K48-linkage), siRNA knockdown, cardiomyocyte overexpression, cardiac-specific OE in vivo","journal":"Journal of cardiovascular pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with K48-ubiquitination assay and functional in vivo cardiac model, single lab","pmids":["39499120"],"is_preprint":false},{"year":2024,"finding":"HERC2 interacts with β-catenin and promotes its ubiquitination, thereby governing CYP2E1 transcriptional regulation. HERC2 deficiency exacerbates APAP-induced liver damage through increased CYP2E1 expression. Lipid nanoparticle delivery of HERC2-overexpressing plasmid reduces liver damage caused by APAP overdose.","method":"Co-immunoprecipitation, ubiquitination assay, liver-specific HERC2 KO mice, single-cell RNA-seq, LNP delivery in vivo","journal":"Advanced science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, ubiquitination assay, tissue-specific KO with defined phenotype, single lab","pmids":["39440550"],"is_preprint":false},{"year":2024,"finding":"The disordered, negatively charged C-terminal tail of HERC2 is intrinsically disordered but provides thermal and structural stability to the HECT C-lobe. MD simulations identify the D4829-R4728 non-bonded contact as prevalent between tail and C-lobe. The C-lobe is the catalytic ubiquitin-transfer domain, and the C-terminal tail may function as a flexible scaffold for protein-protein interactions.","method":"AlphaFold modeling, molecular dynamics simulation, multidimensional NMR (1H-15N HSQC, resonance assignment), circular dichroism melting curves","journal":"Protein science : a publication of the Protein Society","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — NMR and CD with MD simulation confirm disorder and stability function, but functional consequence is inferred; single lab","pmids":["39565083"],"is_preprint":false},{"year":2024,"finding":"HERC2 deficiency in patients with the HERC2-related disorder leads to increased USP20 protein levels (HERC2 normally destabilizes USP20). Elevated USP20 stabilizes the autophagy-initiating kinase ULK1, upregulating autophagy flux. p38 activation disrupts HERC2-USP20 interaction, further elevating USP20 and LC3-II levels. This defines HERC2 as an autophagy regulator via the USP20-ULK1 axis.","method":"Patient-derived fibroblast analysis, Co-immunoprecipitation (HERC2-USP20), lysosomal inhibitor assay, USP20/ULK1/LC3 Western blot, p38 inhibitor epistasis","journal":"Cell death discovery","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP in patient cells, functional lysosomal inhibitor assays, pharmacological epistasis, single lab","pmids":["38570483"],"is_preprint":false},{"year":2025,"finding":"NCOA4's HERC2-binding domain (HBD) harbors a [2Fe-2S] iron-sulfur cluster and can exist in apo- or [2Fe-2S]-bound states. HERC2 specifically recognizes the [2Fe-2S] cluster-bound NCOA4 HBD through a synergistic interaction involving both the CPH domain and a newly defined iron-sulfur cluster-dependent NCOA4-binding domain (INBD) of HERC2. Crystal structures of HERC2(2540-2700) alone and in complex with [2Fe-2S]-bound NCOA4 HBD provide the molecular basis for iron-dependent NCOA4 recognition and degradation.","method":"X-ray crystallography (two structures), biochemical reconstitution, iron-sulfur cluster characterization, mutagenesis, cellular ubiquitination and stability assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — two crystal structures with in vitro reconstitution, iron-sulfur cluster biochemistry, and cellular validation; multiple orthogonal Tier 1 methods in a single rigorous study","pmids":["40705422"],"is_preprint":false},{"year":2025,"finding":"HERC2 binds to the RLD2 domain interface with UBE3A (E6AP) via a conserved 'DxDKDxD' motif in UBE3A; this interaction is conserved across most animals with a central nervous system. HERC2 also recognizes similar DxDKDxD motifs in DOCK10, PCM1, USP35, and other brain-relevant proteins. HERC2 binding to DOCK10 stimulates DOCK10 GEF activity (RAC1/CDC42 activation) through a conformational change; disruption of the HERC2-binding motif in DOCK10 or HERC2 knockdown reduces DOCK10 GEF activity and impairs DOCK10-induced dendritic spine formation in hippocampal neurons.","method":"Quantitative binding assays, X-ray crystallography (RLD2-UBE3A and RLD2-DOCK10 complexes), sequence conservation analysis, GEF activity assay, siRNA knockdown, dendritic spine morphogenesis imaging in neurons","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — crystal structures and biochemical GEF assay, but preprint (not peer-reviewed); multiple orthogonal methods","pmids":["bio_10.1101_2025.09.16.670041"],"is_preprint":true}],"current_model":"HERC2 is a giant (~528 kDa) HECT-domain E3 ubiquitin ligase that acts as a multi-substrate ubiquitin ligase and scaffolding factor coordinating DNA damage response (phospho-T4827-dependent recruitment of RNF8/Ubc13 to drive K63 ubiquitin chains; SUMO1-dependent stabilization of RNF8-Ubc13 via its ZZ SUMO-binding zinc finger), nucleotide excision repair (ubiquitination and circadian degradation of XPA antagonized by ATR-mediated XPA phosphorylation), replication stress response (regulation of USP20 stability to control Claspin-ATR-Chk1 signaling), iron homeostasis (iron-sensing via its CPH/INBD domains that recognize [2Fe-2S] cluster-bound NCOA4 for proteasomal degradation, and degradation of FBXL5), centrosome and ciliogenesis regulation (ubiquitination of CP110, NEURL4, and USP33), p53 pathway modulation (promoting p53 oligomerization via its CPH domain and regulating MDM2 transcription), and G-quadruplex suppression (releasing RPA onto ssDNA and ubiquitinating RPA2 to enable BLM/WRN helicase function); additionally, a conserved interaction with UBE3A (E6AP) via the RLD2 domain stimulates E6AP activity and links HERC2 to Angelman syndrome pathways, while its ZZ domain serves as a reader of both arginylated substrates and histone H3/SUMO1 tails to mediate chromatin association."},"narrative":{"mechanistic_narrative":"HERC2 is a giant HECT-domain E3 ubiquitin ligase and multidomain scaffold that integrates DNA damage responses, replication-stress signaling, iron homeostasis, centrosome/cilium biology, and p53 regulation through both catalytic ubiquitination and non-catalytic protein binding [PMID:20023648, PMID:27528230, PMID:40705422]. In the DNA double-strand break response, IR-induced phosphorylation at Thr4827 docks HERC2 onto the FHA domain of RNF8 and drives assembly of RNF8 with the conjugating enzyme Ubc13 to generate K63-linked ubiquitin chains, supporting retention of 53BP1, RAP80, and BRCA1 at damage sites; this recruitment is reinforced by PIAS4-dependent SUMOylation, with the HERC2 ZZ zinc finger acting as a SUMO-binding module that stabilizes the RNF8-Ubc13 complex [PMID:20023648, PMID:22508508]. As a ligase, HERC2 controls the abundance of numerous substrates through its catalytic Cys4762, including BARD1-uncoupled BRCA1, the NER factor XPA in a circadian/ATR-antagonized manner, FBXL5, USP20, USP33, NCOA4, and RPA2 [PMID:20631078, PMID:20304803, PMID:23178497, PMID:24778179, PMID:25355518, PMID:25326330, PMID:24855649, PMID:26436293, PMID:31582797]. Through USP20 it tunes Claspin–ATR–Chk1 checkpoint signaling under replication stress, and at the replication fork it associates with Claspin and the BLM/WRN–RPA machinery, releasing RPA onto ssDNA and ubiquitinating phospho-RPA2 to suppress G-quadruplex formation and support nucleolar helicase function [PMID:21775519, PMID:25355518, PMID:25326330, PMID:30279242, PMID:31582797, PMID:33432007]. In iron homeostasis, HERC2 senses the [2Fe-2S]-loaded state of NCOA4 via its CPH and INBD domains to direct iron-dependent NCOA4 degradation, linking it to ferritinophagy and ferroptosis sensitivity downstream of NRF2 [PMID:26436293, PMID:36724221, PMID:40705422]. HERC2 additionally promotes p53 oligomerization and transcriptional activity via its CPH domain and regulates MDM2 transcription, regulates centrosome architecture and ciliogenesis through NEURL4/CP110/USP33, and stimulates UBE3A (E6AP) ligase activity via its RLD2 domain, linking it to neuronal pathways [PMID:21493713, PMID:22261722, PMID:24722987, PMID:31665549, PMID:37074924]. Homozygous Herc2 loss is embryonic lethal in mice independently of p53, and HERC2 hypomorphism causes Purkinje cell loss and motor defects, underscoring an essential developmental role [PMID:27528230].","teleology":[{"year":2009,"claim":"Established HERC2 as an active participant in the DSB ubiquitin signaling cascade rather than a passive scaffold, by showing phospho-dependent recruitment of the RNF8/Ubc13 machinery.","evidence":"Co-IP, phospho-site mapping at Thr4827, siRNA, and IR-induced focus assays in human cells","pmids":["20023648"],"confidence":"High","gaps":["Did not define how HERC2 levels of RNF168 are maintained mechanistically","Catalytic versus scaffold contribution of HERC2 to chain formation not separated"]},{"year":2010,"claim":"Demonstrated HERC2 as a bona fide E3 ligase with catalytic Cys4762 that degrades BARD1-uncoupled BRCA1, defining a quality-control role over BRCA1 stoichiometry.","evidence":"In vitro ubiquitination with catalytic mutant, Co-IP, and checkpoint epistasis in human cells","pmids":["20631078"],"confidence":"High","gaps":["Physiological conditions favoring BRCA1 versus BARD1 binding not defined","Chain linkage type on BRCA1 not characterized"]},{"year":2010,"claim":"Linked HERC2 to circadian-regulated nucleotide excision repair by showing it drives oscillatory XPA turnover.","evidence":"Timed tissue-extract repair assays and XPA Western blots in mouse liver","pmids":["20304803"],"confidence":"Medium","gaps":["Direct ubiquitination of XPA by HERC2 not reconstituted in this study","Single-lab; in vitro extract system"]},{"year":2011,"claim":"Showed a non-catalytic HERC2 function: its RLD2 domain stimulates UBE3A/E6AP ligase activity, providing a molecular link to Angelman/E6AP biology.","evidence":"Domain-mapped Co-IP and in vitro/cell ubiquitination assays with catalytic-dead HERC2","pmids":["21493713"],"confidence":"High","gaps":["Physiological substrates affected by HERC2-stimulated E6AP not defined here","Structural basis of stimulation not resolved at this stage"]},{"year":2011,"claim":"Placed HERC2 at the replication fork through Claspin association and regulation of origin firing and MCM2 phosphorylation.","evidence":"Co-IP, DNA fiber assays, and phospho-MCM2 blots with double knockdown in human cells","pmids":["21775519"],"confidence":"Medium","gaps":["Whether HERC2 ubiquitinates a fork component was not established","Single-lab"]},{"year":2012,"claim":"Identified the ZZ zinc finger as a SUMO-binding module and showed SUMOylation cooperates with T4827 phosphorylation to assemble the RNF8-Ubc13 complex at DSBs.","evidence":"PIAS4 knockdown, domain mutagenesis, SUMO-binding assays, and focus formation in human cells","pmids":["22508508"],"confidence":"High","gaps":["SUMO acceptor sites on HERC2 not fully mapped","Quantitative interplay of SUMO and phospho signals not resolved"]},{"year":2012,"claim":"Defined a HERC2-NEURL4 module that controls centrosome architecture via CP110 and ubiquitin-dependent regulation, extending HERC2 function to the centrosome.","evidence":"AP-MS, high-resolution imaging, and RNAi rescue with structure-function transgenes","pmids":["22261722"],"confidence":"High","gaps":["Direct ubiquitination targets at the centrosome incompletely enumerated at this stage","Mechanism of pericentriolar material defect not fully resolved"]},{"year":2012,"claim":"Showed ATR-mediated XPA Ser196 phosphorylation antagonizes HERC2 binding and ubiquitination, defining a damage-responsive switch controlling XPA stability.","evidence":"Phospho-mutant reconstitution in XPA-null cells with Co-IP, ubiquitination, and chromatin retention assays","pmids":["23178497"],"confidence":"High","gaps":["Coordination with circadian XPA control not integrated","Structural basis of phospho-regulated dissociation unknown"]},{"year":2014,"claim":"Revealed a non-degradative HERC2 role in the p53 pathway, promoting p53 oligomerization and transcriptional activity via the CPH domain.","evidence":"Domain-mapped Co-IP, cross-linking oligomerization assays, and transcription reporters in human cells","pmids":["24722987"],"confidence":"High","gaps":["How HERC2 mechanically catalyzes tetramer assembly unresolved","Relationship to HERC2 ligase activity not addressed"]},{"year":2014,"claim":"Connected HERC2 to iron homeostasis by identifying it as the E3 ligase degrading FBXL5, thereby influencing IRP2 regulation and intracellular iron.","evidence":"Proteomics-guided Co-IP, ubiquitination assay, and iron measurement with HERC2 knockdown","pmids":["24778179"],"confidence":"Medium","gaps":["Iron-dependence of the FBXL5 interaction not mechanistically resolved here","Single-lab"]},{"year":2014,"claim":"Established a HERC2-USP20 axis controlling Claspin-ATR-Chk1 signaling, with ATR phosphorylation of USP20 dissociating HERC2 to stabilize the checkpoint.","evidence":"DUB screen, Co-IP, phospho-mapping, and Chk1 checkpoint assays (two converging papers)","pmids":["25355518","25326330"],"confidence":"High","gaps":["Chain linkage on USP20 not detailed","Quantitative thresholds of stress-induced switching unknown"]},{"year":2014,"claim":"Linked HERC2 to histone H2A ubiquitin dynamics by regulating USP16 levels and damage-induced ubiquitin foci.","evidence":"Domain-mapped Co-IP, in vitro deubiquitination, and ubiquitin focus imaging","pmids":["25305019"],"confidence":"Medium","gaps":["Whether HERC2 ubiquitinates USP16 directly not shown","Single-lab"]},{"year":2014,"claim":"Showed HERC2 directs K48 polyubiquitination of USP33 with p97-dependent processing, expanding its substrate repertoire to a centriole-relevant DUB.","evidence":"Quantitative MS, Co-IP, ubiquitination assay, and p97 inhibition in human cells","pmids":["24855649"],"confidence":"Medium","gaps":["Direct catalytic ubiquitin transfer by HERC2 onto USP33 inferred from cellular assays","Single-lab"]},{"year":2015,"claim":"Defined HERC2 as the E3 ligase for iron-dependent NCOA4 degradation, placing it at the intersection of ferritinophagy and proteasomal control.","evidence":"Co-IP, ubiquitination assay, iron-dependent interaction, and zebrafish erythropoiesis model","pmids":["26436293"],"confidence":"High","gaps":["Molecular basis of iron-sensing not yet resolved at this stage","Relative contribution of UPS versus autophagy to NCOA4 turnover unclear"]},{"year":2016,"claim":"Demonstrated HERC2 is essential for development independently of p53 and that haploinsufficiency causes Purkinje cell loss and motor impairment.","evidence":"Herc2 knockout, p53 double-knockout epistasis, behavioral and histological phenotyping in mice","pmids":["27528230"],"confidence":"High","gaps":["Specific substrate(s) underlying lethality not identified","Mechanism of Purkinje cell vulnerability unresolved"]},{"year":2016,"claim":"Connected HERC2 to a SIRT1-driven LKB1 degradation pathway regulating arterial remodeling.","evidence":"DOC-domain Co-IP, K64 mutagenesis, ChIP, and in vivo lentiviral knockdown","pmids":["27259994"],"confidence":"Medium","gaps":["Direct LKB1 ubiquitination by HERC2 inferred","Single-lab"]},{"year":2018,"claim":"Established the E3 ligase activity of HERC2 as required for G-quadruplex suppression by promoting RPA loading and RPA2 ubiquitination in BLM/WRN helicase complexes.","evidence":"In vitro RPA-release assay, CRISPR catalytic-site deletion, G4 imaging, and epistasis in human cells","pmids":["30279242"],"confidence":"High","gaps":["How HERC2 mechanically releases RPA onto ssDNA unresolved","Genomic distribution of HERC2-dependent G4 suppression not mapped"]},{"year":2019,"claim":"Resolved the RPA2 regulatory loop, showing HERC2 promotes ATR-induced RPA2 Ser33 phosphorylation then ubiquitinates and degrades phospho-RPA2 to support G4 suppression.","evidence":"Co-IP, ubiquitination assay, CRISPR catalytic mutant, and phospho-RPA2 blots with ATR inhibitor epistasis","pmids":["31582797"],"confidence":"Medium","gaps":["Direct catalysis of RPA2 ubiquitination not reconstituted in vitro here","Single-lab"]},{"year":2019,"claim":"Showed HERC2 transcriptionally regulates MDM2 within an oligomeric p53/HERC2/NEURL4 complex, with DNA damage dissociating MDM2 to activate p53.","evidence":"Co-IP, MDM2 promoter reporter assays, and knockdown in human cells","pmids":["31665549"],"confidence":"Medium","gaps":["Mechanism by which HERC2 affects MDM2 promoter activity not defined","Single-lab"]},{"year":2019,"claim":"Placed HERC2 downstream of NudCL2 in centriole duplication control via regulation of USP33.","evidence":"CRISPR KO, rescue epistasis, Co-IP, and quantitative proteomics in human cells","pmids":["31427565"],"confidence":"Medium","gaps":["How NudCL2 stabilizes HERC2 structurally unknown","Single-lab"]},{"year":2020,"claim":"Provided structural basis for the dual-reader function of the HERC2 ZZ domain, which binds histone H3 and SUMO1 tails at the same negatively charged site.","evidence":"Crystal structures of two complexes with NMR, mutagenesis, and fluorescence binding","pmids":["32726574"],"confidence":"High","gaps":["Cellular consequences of H3 versus SUMO1 binding choice not resolved","Competition dynamics in vivo unknown"]},{"year":2021,"claim":"Showed HERC2 controls nucleolar localization of BLM/WRN helicases and rDNA G4-dependent rRNA transcription, extending its G4 role to the nucleolus.","evidence":"CRISPR HECT deletion, colocalization imaging, and pre-rRNA transcription/CX-5461 sensitivity assays","pmids":["33432007"],"confidence":"Medium","gaps":["Direct substrate driving nucleolar helicase localization unknown","Single-lab"]},{"year":2022,"claim":"Linked HERC2 loss to C-RAF/MKK3/p38 activation and NRF2-driven oxidative stress resistance, defining a signaling axis independent of p53.","evidence":"Patient fibroblasts, Co-IP, ubiquitylation, RAF/p38 inhibitor epistasis, and NRF2 blots","pmids":["36241744"],"confidence":"Medium","gaps":["Direct C-RAF ubiquitination by HERC2 not fully reconstituted","Single-lab"]},{"year":2022,"claim":"Identified the HERC2 ZZ domain as a reader of arginylated (Nt-R) cargo, connecting HERC2 to N-degron pathways and autophagy/proteasome targeting.","evidence":"NMR titration, HERC2 DOC crystal structure, mutagenesis, and immunofluorescence","pmids":["35411094"],"confidence":"Medium","gaps":["Functional autophagy targeting based on imaging alone","In vivo arginylated substrates not identified"]},{"year":2023,"claim":"Showed NRF2 transcriptionally maintains HERC2, integrating HERC2 into iron and ferroptosis control via NCOA4/ferritin handling.","evidence":"NRF2 knockout, autophagy flux, iron measurement, and ferroptosis sensitivity assays","pmids":["36724221"],"confidence":"Medium","gaps":["Direct NRF2 binding at the HERC2 promoter not mapped here","Single-lab"]},{"year":2023,"claim":"Defined an oncogenic HERC2 function in hepatocellular carcinoma, restraining PTP1B to sustain JAK2/STAT3 and PD-L1-mediated immune evasion.","evidence":"HERC2 KO/overexpression, Co-IP, PTP1B localization imaging, and in vivo mouse liver carcinogenesis models","pmids":["36721234"],"confidence":"Medium","gaps":["Whether HERC2 ubiquitinates PTP1B not established","Single-lab"]},{"year":2023,"claim":"Showed HERC2 ubiquitinates CP110 at centriolar satellites to promote ciliogenesis, with EHD1 controlling HERC2/satellite transport to the mother centriole.","evidence":"Co-IP, ubiquitination assay, satellite localization imaging, and ciliogenesis quantification with siRNA","pmids":["37074924"],"confidence":"Medium","gaps":["Mechanism of EHD1-dependent transport unresolved","Single-lab"]},{"year":2024,"claim":"Linked HERC2 to cardiac hypertrophy through K48-linked degradation of MeCP2 and downstream Lin28a derepression.","evidence":"Co-IP, K48 ubiquitination assay, and cardiac-specific overexpression in vivo","pmids":["39499120"],"confidence":"Medium","gaps":["Direct ubiquitination site on MeCP2 not mapped","Single-lab"]},{"year":2024,"claim":"Showed HERC2 ubiquitinates β-catenin to govern CYP2E1 transcription and protect against acetaminophen-induced liver injury.","evidence":"Co-IP, ubiquitination assay, liver-specific KO mice, scRNA-seq, and LNP delivery in vivo","pmids":["39440550"],"confidence":"Medium","gaps":["β-catenin ubiquitination linkage type not detailed","Single-lab"]},{"year":2024,"claim":"Characterized the disordered C-terminal tail of HERC2 as a stabilizer of the catalytic HECT C-lobe, implicating it as a flexible interaction scaffold.","evidence":"AlphaFold modeling, MD simulation, multidimensional NMR, and CD melting","pmids":["39565083"],"confidence":"Medium","gaps":["Functional consequence of tail-C-lobe contact inferred not tested","Single-lab"]},{"year":2024,"claim":"Defined HERC2 as an autophagy regulator via the USP20-ULK1 axis, with HERC2 deficiency elevating USP20, stabilizing ULK1, and increasing autophagy flux.","evidence":"Patient fibroblasts, HERC2-USP20 Co-IP, lysosomal inhibitor assays, and p38 inhibitor epistasis","pmids":["38570483"],"confidence":"Medium","gaps":["Direct ULK1 stabilization mechanism by USP20 not fully resolved here","Single-lab"]},{"year":2025,"claim":"Provided the structural and biochemical basis for iron-sensing, showing HERC2 recognizes [2Fe-2S]-bound NCOA4 through its CPH and newly defined INBD domains.","evidence":"Two crystal structures, in vitro reconstitution, iron-sulfur cluster biochemistry, and cellular ubiquitination/stability assays","pmids":["40705422"],"confidence":"High","gaps":["How iron cluster occupancy is dynamically sensed in vivo not fully resolved","Whether other substrates use iron-dependent recognition unknown"]},{"year":2025,"claim":"Defined a conserved DxDKDxD motif recognized by the HERC2 RLD2 domain that mediates UBE3A binding and broadens to DOCK10 and other brain-relevant proteins, with HERC2 stimulating DOCK10 GEF activity and dendritic spine formation.","evidence":"Crystal structures of RLD2 complexes, GEF activity assays, conservation analysis, and dendritic spine imaging in neurons (preprint)","pmids":["bio_10.1101_2025.09.16.670041"],"confidence":"Medium","gaps":["Preprint, not peer-reviewed","Physiological scope of additional DxDKDxD partners not validated"]},{"year":null,"claim":"How a single giant scaffold coordinates its many catalytic and non-catalytic functions across distinct subcellular compartments and selects among its diverse substrates remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying regulatory logic for substrate selection across pathways","Full-length structural architecture not solved","Disease-causing mutation mapping to specific functional domains incomplete"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[1,9,12,13,27,31]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,9,13,17,31]},{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[20]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,5,8,32]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[3,32]},{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[13,31]}],"localization":[{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[6,19,26]},{"term_id":"GO:0005730","term_label":"nucleolus","supporting_discovery_ids":[21]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[14]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[0,5]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[0,1,5,7]},{"term_id":"R-HSA-69306","term_label":"DNA Replication","supporting_discovery_ids":[4,10,16,17]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,9,12,13,31]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[9,13,24,31]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[6,19,26]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[13,24,30]}],"complexes":["RNF8-Ubc13 DSB ubiquitin module","p53/HERC2/NEURL4/MDM2 complex","NEURL4-HERC2-CP110 centrosomal module","BLM/WRN-RPA helicase complex"],"partners":["RNF8","NCOA4","UBE3A","NEURL4","USP20","RPA2","CP110","USP33"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O95714","full_name":"E3 ubiquitin-protein ligase HERC2","aliases":["HECT domain and RCC1-like domain-containing protein 2","HECT-type E3 ubiquitin transferase HERC2"],"length_aa":4834,"mass_kda":527.2,"function":"E3 ubiquitin-protein ligase that regulates ubiquitin-dependent retention of repair proteins on damaged chromosomes. Recruited to sites of DNA damage in response to ionizing radiation (IR) and facilitates the assembly of UBE2N and RNF8 promoting DNA damage-induced formation of 'Lys-63'-linked ubiquitin chains. Acts as a mediator of binding specificity between UBE2N and RNF8. Involved in the maintenance of RNF168 levels. E3 ubiquitin-protein ligase that promotes the ubiquitination and proteasomal degradation of XPA which influences the circadian oscillation of DNA excision repair activity. By controlling the steady-state expression of the IGF1R receptor, indirectly regulates the insulin-like growth factor receptor signaling pathway (PubMed:26692333). Also modulates iron metabolism by regulating the basal turnover of FBXL5 (PubMed:24778179)","subcellular_location":"Cytoplasm; Cytoplasm, cytoskeleton, microtubule organizing center, centrosome, centriole; Nucleus","url":"https://www.uniprot.org/uniprotkb/O95714/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/HERC2","classification":"Not Classified","n_dependent_lines":28,"n_total_lines":1208,"dependency_fraction":0.023178807947019868},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CKAP2","stoichiometry":4.0},{"gene":"MAP4","stoichiometry":0.2},{"gene":"TUBB4B","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/HERC2","total_profiled":1310},"omim":[{"mim_id":"618649","title":"HECT DOMAIN E3 UBIQUITIN PROTEIN LIGASE 1; HECTD1","url":"https://www.omim.org/entry/618649"},{"mim_id":"617011","title":"MACROCEPHALY, DYSMORPHIC FACIES, AND PSYCHOMOTOR RETARDATION; MDFPMR","url":"https://www.omim.org/entry/617011"},{"mim_id":"616144","title":"WD REPEAT-CONTAINING PROTEIN 73; WDR73","url":"https://www.omim.org/entry/616144"},{"mim_id":"615516","title":"INTELLECTUAL DEVELOPMENTAL DISORDER, AUTOSOMAL RECESSIVE 38; MRT38","url":"https://www.omim.org/entry/615516"},{"mim_id":"613745","title":"ANAPHASE-PROMOTING COMPLEX, SUBUNIT 10; ANAPC10","url":"https://www.omim.org/entry/613745"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Plasma membrane","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/HERC2"},"hgnc":{"alias_symbol":["jdf2","p528","D15F37S1"],"prev_symbol":[]},"alphafold":{"accession":"O95714","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O95714","model_url":"","pae_url":"","plddt_mean":null},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HERC2","jax_strain_url":"https://www.jax.org/strain/search?query=HERC2"},"sequence":{"accession":"O95714","fasta_url":"https://rest.uniprot.org/uniprotkb/O95714.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O95714/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O95714"}},"corpus_meta":[{"pmid":"26436293","id":"PMC_26436293","title":"Ferritinophagy via NCOA4 is required for erythropoiesis and is regulated by iron dependent HERC2-mediated 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the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/20304803","citation_count":188,"is_preprint":false},{"pmid":"18252221","id":"PMC_18252221","title":"Three genome-wide association studies and a linkage analysis identify HERC2 as a human iris color gene.","date":"2008","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/18252221","citation_count":173,"is_preprint":false},{"pmid":"20631078","id":"PMC_20631078","title":"HERC2 is an E3 ligase that targets BRCA1 for degradation.","date":"2010","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/20631078","citation_count":127,"is_preprint":false},{"pmid":"22508508","id":"PMC_22508508","title":"DNA damage-inducible SUMOylation of HERC2 promotes RNF8 binding via a novel SUMO-binding Zinc finger.","date":"2012","source":"The Journal of cell 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HERC2 facilitates assembly of the ubiquitin-conjugating enzyme Ubc13 with RNF8, promoting DNA damage-induced formation of Lys63-linked ubiquitin chains. HERC2 also interacts with and maintains levels of RNF168, and HERC2 knockdown abrogates ubiquitin-dependent retention of 53BP1, RAP80, and BRCA1 at damage sites.\",\n      \"method\": \"Co-immunoprecipitation, phosphorylation mapping, siRNA knockdown, IR-induced focus formation assays, radiosensitivity assays\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, phospho-site identification, functional epistasis with multiple repair factors, replicated across multiple orthogonal readouts in a focused study\",\n      \"pmids\": [\"20023648\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"HERC2 acts as an E3 ubiquitin ligase that targets BARD1-uncoupled BRCA1 for degradation. The HECT domain of HERC2 interacts with an N-terminal degron domain in BRCA1, and ubiquitination depends on Cys4762 (catalytic site) of HERC2. HERC2 depletion restores BRCA1 expression and G2/M checkpoint activity when BARD1 is depleted; BARD1 protects BRCA1 from HERC2-mediated ubiquitination.\",\n      \"method\": \"Co-immunoprecipitation, in vitro ubiquitination assay, catalytic mutant analysis (Cys4762), siRNA knockdown, cell-cycle checkpoint assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro ubiquitination assay with catalytic mutant, Co-IP, and functional genetic epistasis in a single focused study\",\n      \"pmids\": [\"20631078\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"HERC2 ubiquitin ligase mediates circadian oscillation of the NER factor XPA in mouse liver tissue extracts. HERC2 promotes XPA ubiquitination and degradation, and this is regulated in concert with transcriptional control by core circadian clock proteins including cryptochrome.\",\n      \"method\": \"Tissue extract repair assays (timed), Western blot for XPA oscillation, functional ubiquitination in extracts\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional assay in tissue extracts at multiple time points with mechanistic attribution to HERC2, single lab\",\n      \"pmids\": [\"20304803\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"HERC2 stimulates the ubiquitin-protein ligase activity of E6AP (UBE3A) in vitro and in cells. The interaction is mediated by the RCC1-like domain 2 (RLD2) of HERC2 and residues 150-200 of E6AP. This stimulatory effect does not require the ubiquitin ligase activity of HERC2 itself.\",\n      \"method\": \"Co-immunoprecipitation, domain mapping, in vitro ubiquitination assay, cell-based ubiquitination assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of E6AP stimulation with domain mapping and catalytic-dead HERC2 controls, multiple orthogonal methods\",\n      \"pmids\": [\"21493713\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"HERC2 interacts with Claspin and is a component of the DNA replication fork complex. HERC2 depletion alleviated slow replication fork progression in Claspin-deficient cells, suppressed enhanced origin firing, and decreased MCM2 phosphorylation. In a HERC2-dependent manner, aphidicolin treatment enhanced MCM2 phosphorylation.\",\n      \"method\": \"Co-immunoprecipitation, DNA fiber assay, siRNA knockdown, phospho-MCM2 Western blot\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus functional double-knockdown epistasis and replication assays, single lab\",\n      \"pmids\": [\"21775519\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"HERC2 and RNF168 are SUMOylated at DNA double-strand break sites in a PIAS4-dependent manner. SUMOylation of HERC2 is required for its DSB-induced association with RNF8 and for stabilizing the RNF8-Ubc13 complex. The ZZ zinc finger of HERC2 functions as a novel SUMO-specific binding module; together with concomitant phosphorylation at T4827, it promotes RNF8 binding.\",\n      \"method\": \"Co-immunoprecipitation, domain mutagenesis, SUMO-specific binding assays, siRNA knockdown of PIAS4, focus formation assays at DSBs\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — biochemical binding domain mapping with ZZ finger SUMO module identification, multiple orthogonal methods (Co-IP, mutagenesis, focus formation), single focused study\",\n      \"pmids\": [\"22508508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"HERC2 and NEURL4 are novel interaction partners of the centrosomal protein CP110. HERC2 and NEURL4 localize to the centrosome, and interfering with their function causes aberrant filamentous pericentriolar material structures. NEURL4 is a substrate of HERC2, and the NEURL4-HERC2 complex participates in ubiquitin-dependent regulation of centrosome architecture. CP110 binding to HERC2 (mediated via nonoverlapping NEURL4 regions) is required for normal centrosome integrity.\",\n      \"method\": \"Interaction proteomics (AP-MS), high-resolution imaging, RNAi, structure-function analysis with RNAi-resistant transgene\",\n      \"journal\": \"Molecular & cellular proteomics : MCP\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — AP-MS identification validated with RNAi rescue and high-resolution functional imaging, multiple orthogonal approaches\",\n      \"pmids\": [\"22261722\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"ATR-mediated phosphorylation of XPA at Ser196 enhances XPA stability by inhibiting HERC2-mediated ubiquitination and degradation. Upon UV damage, ATR facilitates HERC2 dissociation from XPA; phosphomimetic S196D shows reduced HERC2 binding and decreased ubiquitination, while S196A shows persistent HERC2 association and enhanced ubiquitination.\",\n      \"method\": \"Co-immunoprecipitation, site-directed mutagenesis (S196D/S196A), ubiquitination assay, XPA-deficient cell complementation, chromatin retention assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — phospho-mutant reconstitution in XPA-null cells with Co-IP, ubiquitination assay, and chromatin fractionation, multiple orthogonal methods\",\n      \"pmids\": [\"23178497\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"HERC2 interacts with p53 via its CPH domain (binding the last 43 amino acids of p53). HERC2 depletion reduces p53 transcriptional activity and p53 oligomerization without affecting p53 stability or MDM2 activity. The HERC2-p53 interaction requires the p53 tetramerization domain, and HERC2 promotes p53 oligomerization as shown by cross-linking assays.\",\n      \"method\": \"Co-immunoprecipitation, domain mapping, RNA interference, transcriptional reporter assays, chemical cross-linking, focus formation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — domain-mapped Co-IP, cross-linking oligomerization assay, functional transcription assay, multiple orthogonal methods in a single focused study\",\n      \"pmids\": [\"24722987\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"HERC2 is the E3 ubiquitin ligase responsible for polyubiquitination and proteasomal degradation of FBXL5, the F-box protein that targets IRP2 for degradation. HERC2 depletion stabilizes FBXL5 and leads to a decrease in intracellular ferrous iron.\",\n      \"method\": \"Proteomics/Co-IP to identify HERC2-FBXL5 interaction, siRNA knockdown of HERC2, ubiquitination assay, iron measurement\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteomics-guided Co-IP with functional knockdown and iron measurement, single lab\",\n      \"pmids\": [\"24778179\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"USP20 deubiquitinates and stabilizes Claspin to promote ATR-Chk1 signaling. Under normal conditions, HERC2 promotes ubiquitination-mediated degradation of USP20. Under replication stress, ATR-mediated phosphorylation of USP20 causes disassociation of HERC2 from USP20, stabilizing USP20 and consequently Claspin to enhance CHK1 checkpoint activation.\",\n      \"method\": \"DUB screen, Co-immunoprecipitation, phosphorylation mapping, siRNA knockdown, checkpoint signaling assays (Chk1 phosphorylation)\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent papers (25355518, 25326330) using Co-IP, phospho-mapping, and functional checkpoint assays converge on same HERC2-USP20-Claspin mechanism\",\n      \"pmids\": [\"25355518\", \"25326330\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The histone H2A deubiquitinase USP16 interacts with HERC2 via USP16's coiled-coil domain and HERC2's C-terminal HECT domain. HERC2 knockdown affects ubiquitinated H2A levels through USP16. DNA damage increases USP16 levels in a HERC2-dependent manner; elevated USP16 acts as a negative regulator of damage-induced ubiquitin foci formation. USP16 can deubiquitinate both H2A Lys119 and H2A Lys15 in vitro.\",\n      \"method\": \"Co-immunoprecipitation, domain mapping, siRNA knockdown, in vitro deubiquitination assay, ubiquitin focus formation imaging\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain-mapped Co-IP, in vitro deubiquitination assay, functional knockdown, single lab\",\n      \"pmids\": [\"25305019\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"HERC2 degrades the deubiquitinating enzyme USP33 through K48-linked polyubiquitination. p97 (with Ufd1-Npl4 adaptor) is required for post-ubiquitination processing of USP33. Inhibition of p97 causes accumulation of polyubiquitinated USP33.\",\n      \"method\": \"Quantitative mass spectrometry, Co-immunoprecipitation, p97 knockdown/inhibition, ubiquitination assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS-identified interaction, ubiquitination assay, and functional epistasis with p97 inhibition, single lab\",\n      \"pmids\": [\"24855649\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"HERC2 ubiquitin ligase promotes ubiquitin-dependent proteasomal degradation of NCOA4 (the ferritinophagy receptor) in an iron-dependent manner. Excess iron induces an interaction between NCOA4 and HERC2, leading to NCOA4 degradation. NCOA4 abundance is thus under dual control by autophagy and the ubiquitin-proteasome system, with HERC2 acting as the E3 ligase for iron-dependent NCOA4 turnover.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, iron-dependent interaction assays, zebrafish erythropoiesis model, cell culture knockdown\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP, ubiquitination assay, iron-dependent interaction, and in vivo zebrafish validation, multiple orthogonal methods, replicated in subsequent papers\",\n      \"pmids\": [\"26436293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SIRT1 binds to the DOC domain of HERC2 via its amino-terminus; HERC2 then ubiquitinates LKB1 for proteasomal degradation in the nuclear compartment of endothelial cells. Acetylation of LKB1 at K64 triggers formation of the SIRT1/HERC2/LKB1 complex. HERC2 knockdown increases association of LKB1 with the TGFβ1 promoter and abolishes the protective effects of SIRT1 on arterial remodeling.\",\n      \"method\": \"Co-immunoprecipitation, site-directed mutagenesis (K64), chromatin immunoprecipitation (ChIP-qPCR), siRNA knockdown, lentiviral knockdown in vivo\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with mutagenesis, ChIP, and in vivo lentiviral knockdown, single lab\",\n      \"pmids\": [\"27259994\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Homozygous Herc2 knockout mice are not viable (embryonic lethal). p53 depletion does not rescue lethality, indicating HERC2's essential developmental role is p53-independent. Heterozygous mice show ~50% reduced HERC2 levels, reduced ubiquitin ligase activity and p53 stimulation, and display loss of Purkinje cells with impaired motor coordination. HERC2 is detected in Purkinje cells and autophagosomes/lysosomes accumulate in heterozygous cerebella.\",\n      \"method\": \"Targeted gene knockout (homozygous lethal), p53 double-knockout epistasis, behavioral analysis, immunohistochemistry of cerebellum, quantitative ubiquitin ligase assay\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean Herc2 KO with defined lethality, p53 epistasis experiment, behavioral and histological phenotyping, multiple orthogonal methods\",\n      \"pmids\": [\"27528230\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"HERC2 interacts with BLM, WRN RecQ helicases and RPA complexes during S-phase. HERC2 depletion dissociates RPA from BLM and WRN complexes and significantly increases G-quadruplex (G4) DNA formation. In vitro, HERC2 releases RPA onto ssDNA. CRISPR deletion of the HERC2 catalytic ubiquitin-binding site inhibited RPA2 ubiquitination, caused RPA accumulation in helicase complexes, and increased G4 formation—establishing the E3 ligase activity as required for G4 suppression. HERC2 has an epistatic relationship with BLM and WRN in G4 suppression.\",\n      \"method\": \"Co-immunoprecipitation, in vitro RPA-release assay, CRISPR/Cas9 catalytic-site deletion, G4 immunofluorescence, siRNA epistasis, sensitivity to G4 stabilizers\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro reconstitution, CRISPR catalytic mutant, epistasis analysis, and cellular imaging, multiple orthogonal methods in single focused study\",\n      \"pmids\": [\"30279242\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"HERC2 interacts with RPA2 through its C-terminal HECT domain. HERC2 promotes ATR-induced phosphorylation of RPA2 at Ser33 under low-level replication stress, and subsequently mediates ubiquitination and degradation of phosphorylated RPA2. Cells lacking HERC2 catalytic residues constitutively accumulate Ser33-phosphorylated RPA2. This regulatory loop is required for suppression of G-quadruplex DNA structures.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, HERC2 catalytic mutant (CRISPR), phospho-RPA2 Western blot, ATR inhibitor epistasis, G4 immunofluorescence\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, catalytic mutant, and functional epistasis, single lab\",\n      \"pmids\": [\"31582797\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MDM2 forms a complex with oligomeric p53, HERC2, and NEURL4. HERC2 knockdown reduces MDM2 mRNA and protein levels by inhibiting MDM2 promoter activation (not by affecting MDM2 protein stability). DNA damage dissociates MDM2 from the p53/HERC2/NEURL4 complex, leading to increased phosphorylation and acetylation of p53 oligomers, which then compete for MDM2 promoter binding.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, MDM2 promoter luciferase/reporter assay, Western blot for MDM2 stability\",\n      \"journal\": \"Molecular oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, promoter reporter assay, functional knockdown, single lab\",\n      \"pmids\": [\"31665549\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"NudCL2 interacts with and stabilizes HERC2. NudCL2 knockout leads to centriole amplification, and ectopic HERC2 expression rescues this phenotype while NudCL2 overexpression cannot rescue HERC2 depletion, establishing HERC2 as epistatic downstream of NudCL2. HERC2 controls levels of USP33 (a positive regulator of centriole duplication); USP33 knockdown reverses centriole amplification in both NudCL2 KO and HERC2-depleted cells.\",\n      \"method\": \"CRISPR/Cas9 knockout, siRNA knockdown, Co-immunoprecipitation, rescue experiments, quantitative proteomics\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR KO with defined phenotype, rescue epistasis, Co-IP, and proteomic identification, single lab\",\n      \"pmids\": [\"31427565\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The ZZ domain of HERC2 (HERC2ZZ) binds to the histone H3 tail and to the N-terminal tail of SUMO1 via the same negatively charged site, with comparable affinities. Crystal structures of HERC2ZZ:H3 and HERC2ZZ:SUMO1 complexes reveal the molecular basis: a critical role for the negatively charged site in capturing A1 of H3, while SUMO1 adopts an α-helical conformation at the same site. HERC2ZZ tolerates common H3 PTMs.\",\n      \"method\": \"X-ray crystallography, NMR titration, mutagenesis, fluorescence binding assays\",\n      \"journal\": \"Structure (London, England : 1993)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures of two complexes validated by NMR, mutagenesis, and fluorescence, multiple orthogonal Tier 1 methods\",\n      \"pmids\": [\"32726574\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"HERC2 inactivation (depletion or homozygous HECT deletion) prevents nucleolar localization of BLM and WRN RecQ helicases and inhibits relocalization of BLM to replication stress-induced RPA foci. HERC2 co-localizes with fibrillarin and RNA Pol I subunit RPA194. HERC2 dysfunction enhances the suppressive effects of the rDNA G4 stabilizer CX-5461 on pre-rRNA transcription.\",\n      \"method\": \"CRISPR/Cas9 HECT domain deletion, siRNA knockdown, immunofluorescence/colocalization, pre-rRNA transcription assay, CX-5461 sensitivity assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR deletion with nucleolar localization imaging and functional rRNA transcription assays, single lab\",\n      \"pmids\": [\"33432007\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"HERC2 deficiency activates the C-RAF/MKK3/p38 signaling pathway. HERC2 forms molecular complexes with RAF proteins, regulates C-RAF ubiquitylation, and p38 activation in HERC2-deficient cells is RAF/MKK3-dependent. This results in increased resistance to oxidative stress and elevated NRF2 and antioxidant target gene expression, independent of p53.\",\n      \"method\": \"Patient-derived fibroblast analysis, HERC2 knockdown, Co-immunoprecipitation, proteomics, ubiquitylation assay, RAF/p38 inhibitor epistasis, NRF2 Western blot\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and ubiquitylation assay with RAF/MKK3 inhibitor epistasis and patient cell validation, single lab\",\n      \"pmids\": [\"36241744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The ZZ domain of HERC2 (HERC2ZZ) recognizes arginylated substrates via the Nt-R cargo degradation signal. NMR titration and mutagenesis identify a well-defined binding site on HERC2ZZ comprising negatively charged aspartate residues. The DOC domain adjacent to ZZ shows a conformational rearrangement when linked to ZZ. Stimulation of autophagy promotes HERC2 targeting to the proteasome.\",\n      \"method\": \"NMR titration, X-ray crystallography (HERC2DOC), mutagenesis, immunofluorescence microscopy\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR and crystal structure, but functional autophagy-targeting based on immunofluorescence alone; single lab\",\n      \"pmids\": [\"35411094\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NRF2 maintains HERC2 expression (HERC2 is transcriptionally regulated by NRF2). NRF2 knockout reduces HERC2 levels, causing simultaneous accumulation of ferritin and NCOA4 and apoferritin accumulation in autophagosomes. This elevates the labile iron pool and sensitizes cells to ferroptosis. NRF2 also controls VAMP8 (for autophagosome-lysosome fusion) in the same pathway.\",\n      \"method\": \"NRF2 knockout (genetic), Western blot, autophagy flux assays, iron measurement, ferroptosis sensitivity assays\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with multiple biochemical readouts confirming NRF2→HERC2→NCOA4 axis, single lab\",\n      \"pmids\": [\"36724221\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"HERC2 promotes cancer stemness and PD-L1-mediated immune evasion in hepatocellular carcinoma by activating the JAK2/STAT3 pathway. Mechanistically, HERC2 interacts with the ER-resident phosphatase PTP1B and limits PTP1B translocation from the ER to the ER-plasma membrane junction, thereby reducing PTP1B's inhibitory effect on JAK2 phosphorylation.\",\n      \"method\": \"HERC2 knockout and overexpression in HCC cells, Co-immunoprecipitation, immunofluorescence for PTP1B localization, DEN-induced mouse liver carcinogenesis (hepatocyte-specific KO), orthotopic transplantation model\",\n      \"journal\": \"Journal of experimental & clinical cancer research : CR\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, subcellular localization by immunofluorescence, and functional in vivo mouse models, single lab\",\n      \"pmids\": [\"36721234\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"HERC2 ubiquitinates CP110 to promote its degradation during ciliogenesis. HERC2 localizes to centriolar satellites. EHD1 regulates the transport of centriolar satellites and HERC2 to the mother centriole during ciliogenesis, and EHD1 is required for CP110 ubiquitination. HERC2 knockdown impairs ciliogenesis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, immunofluorescence (HERC2 to centriolar satellites), siRNA knockdown (HERC2, EHD1), ciliogenesis quantification\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, ubiquitination assay, and localization-function link via siRNA knockdown, single lab\",\n      \"pmids\": [\"37074924\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"HERC2 promotes cardiac hypertrophy by directly binding MeCP2 and promoting its K48-linked polyubiquitination and proteasomal degradation. Reduced MeCP2 (a transcriptional suppressor) elevates Lin28a expression, driving hypertrophy. Knockdown of Lin28a attenuates Ang II-induced hypertrophy and abolishes HERC2 overexpression effects.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay (K48-linkage), siRNA knockdown, cardiomyocyte overexpression, cardiac-specific OE in vivo\",\n      \"journal\": \"Journal of cardiovascular pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with K48-ubiquitination assay and functional in vivo cardiac model, single lab\",\n      \"pmids\": [\"39499120\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"HERC2 interacts with β-catenin and promotes its ubiquitination, thereby governing CYP2E1 transcriptional regulation. HERC2 deficiency exacerbates APAP-induced liver damage through increased CYP2E1 expression. Lipid nanoparticle delivery of HERC2-overexpressing plasmid reduces liver damage caused by APAP overdose.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, liver-specific HERC2 KO mice, single-cell RNA-seq, LNP delivery in vivo\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, ubiquitination assay, tissue-specific KO with defined phenotype, single lab\",\n      \"pmids\": [\"39440550\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The disordered, negatively charged C-terminal tail of HERC2 is intrinsically disordered but provides thermal and structural stability to the HECT C-lobe. MD simulations identify the D4829-R4728 non-bonded contact as prevalent between tail and C-lobe. The C-lobe is the catalytic ubiquitin-transfer domain, and the C-terminal tail may function as a flexible scaffold for protein-protein interactions.\",\n      \"method\": \"AlphaFold modeling, molecular dynamics simulation, multidimensional NMR (1H-15N HSQC, resonance assignment), circular dichroism melting curves\",\n      \"journal\": \"Protein science : a publication of the Protein Society\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR and CD with MD simulation confirm disorder and stability function, but functional consequence is inferred; single lab\",\n      \"pmids\": [\"39565083\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"HERC2 deficiency in patients with the HERC2-related disorder leads to increased USP20 protein levels (HERC2 normally destabilizes USP20). Elevated USP20 stabilizes the autophagy-initiating kinase ULK1, upregulating autophagy flux. p38 activation disrupts HERC2-USP20 interaction, further elevating USP20 and LC3-II levels. This defines HERC2 as an autophagy regulator via the USP20-ULK1 axis.\",\n      \"method\": \"Patient-derived fibroblast analysis, Co-immunoprecipitation (HERC2-USP20), lysosomal inhibitor assay, USP20/ULK1/LC3 Western blot, p38 inhibitor epistasis\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP in patient cells, functional lysosomal inhibitor assays, pharmacological epistasis, single lab\",\n      \"pmids\": [\"38570483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"NCOA4's HERC2-binding domain (HBD) harbors a [2Fe-2S] iron-sulfur cluster and can exist in apo- or [2Fe-2S]-bound states. HERC2 specifically recognizes the [2Fe-2S] cluster-bound NCOA4 HBD through a synergistic interaction involving both the CPH domain and a newly defined iron-sulfur cluster-dependent NCOA4-binding domain (INBD) of HERC2. Crystal structures of HERC2(2540-2700) alone and in complex with [2Fe-2S]-bound NCOA4 HBD provide the molecular basis for iron-dependent NCOA4 recognition and degradation.\",\n      \"method\": \"X-ray crystallography (two structures), biochemical reconstitution, iron-sulfur cluster characterization, mutagenesis, cellular ubiquitination and stability assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — two crystal structures with in vitro reconstitution, iron-sulfur cluster biochemistry, and cellular validation; multiple orthogonal Tier 1 methods in a single rigorous study\",\n      \"pmids\": [\"40705422\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"HERC2 binds to the RLD2 domain interface with UBE3A (E6AP) via a conserved 'DxDKDxD' motif in UBE3A; this interaction is conserved across most animals with a central nervous system. HERC2 also recognizes similar DxDKDxD motifs in DOCK10, PCM1, USP35, and other brain-relevant proteins. HERC2 binding to DOCK10 stimulates DOCK10 GEF activity (RAC1/CDC42 activation) through a conformational change; disruption of the HERC2-binding motif in DOCK10 or HERC2 knockdown reduces DOCK10 GEF activity and impairs DOCK10-induced dendritic spine formation in hippocampal neurons.\",\n      \"method\": \"Quantitative binding assays, X-ray crystallography (RLD2-UBE3A and RLD2-DOCK10 complexes), sequence conservation analysis, GEF activity assay, siRNA knockdown, dendritic spine morphogenesis imaging in neurons\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structures and biochemical GEF assay, but preprint (not peer-reviewed); multiple orthogonal methods\",\n      \"pmids\": [\"bio_10.1101_2025.09.16.670041\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"HERC2 is a giant (~528 kDa) HECT-domain E3 ubiquitin ligase that acts as a multi-substrate ubiquitin ligase and scaffolding factor coordinating DNA damage response (phospho-T4827-dependent recruitment of RNF8/Ubc13 to drive K63 ubiquitin chains; SUMO1-dependent stabilization of RNF8-Ubc13 via its ZZ SUMO-binding zinc finger), nucleotide excision repair (ubiquitination and circadian degradation of XPA antagonized by ATR-mediated XPA phosphorylation), replication stress response (regulation of USP20 stability to control Claspin-ATR-Chk1 signaling), iron homeostasis (iron-sensing via its CPH/INBD domains that recognize [2Fe-2S] cluster-bound NCOA4 for proteasomal degradation, and degradation of FBXL5), centrosome and ciliogenesis regulation (ubiquitination of CP110, NEURL4, and USP33), p53 pathway modulation (promoting p53 oligomerization via its CPH domain and regulating MDM2 transcription), and G-quadruplex suppression (releasing RPA onto ssDNA and ubiquitinating RPA2 to enable BLM/WRN helicase function); additionally, a conserved interaction with UBE3A (E6AP) via the RLD2 domain stimulates E6AP activity and links HERC2 to Angelman syndrome pathways, while its ZZ domain serves as a reader of both arginylated substrates and histone H3/SUMO1 tails to mediate chromatin association.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HERC2 is a giant HECT-domain E3 ubiquitin ligase and multidomain scaffold that integrates DNA damage responses, replication-stress signaling, iron homeostasis, centrosome/cilium biology, and p53 regulation through both catalytic ubiquitination and non-catalytic protein binding [#0, #15, #31]. In the DNA double-strand break response, IR-induced phosphorylation at Thr4827 docks HERC2 onto the FHA domain of RNF8 and drives assembly of RNF8 with the conjugating enzyme Ubc13 to generate K63-linked ubiquitin chains, supporting retention of 53BP1, RAP80, and BRCA1 at damage sites; this recruitment is reinforced by PIAS4-dependent SUMOylation, with the HERC2 ZZ zinc finger acting as a SUMO-binding module that stabilizes the RNF8-Ubc13 complex [#0, #5]. As a ligase, HERC2 controls the abundance of numerous substrates through its catalytic Cys4762, including BARD1-uncoupled BRCA1, the NER factor XPA in a circadian/ATR-antagonized manner, FBXL5, USP20, USP33, NCOA4, and RPA2 [#1, #2, #7, #9, #10, #12, #13, #17]. Through USP20 it tunes Claspin–ATR–Chk1 checkpoint signaling under replication stress, and at the replication fork it associates with Claspin and the BLM/WRN–RPA machinery, releasing RPA onto ssDNA and ubiquitinating phospho-RPA2 to suppress G-quadruplex formation and support nucleolar helicase function [#4, #10, #16, #17, #21]. In iron homeostasis, HERC2 senses the [2Fe-2S]-loaded state of NCOA4 via its CPH and INBD domains to direct iron-dependent NCOA4 degradation, linking it to ferritinophagy and ferroptosis sensitivity downstream of NRF2 [#13, #24, #31]. HERC2 additionally promotes p53 oligomerization and transcriptional activity via its CPH domain and regulates MDM2 transcription, regulates centrosome architecture and ciliogenesis through NEURL4/CP110/USP33, and stimulates UBE3A (E6AP) ligase activity via its RLD2 domain, linking it to neuronal pathways [#3, #6, #8, #18, #26]. Homozygous Herc2 loss is embryonic lethal in mice independently of p53, and HERC2 hypomorphism causes Purkinje cell loss and motor defects, underscoring an essential developmental role [#15].\",\n  \"teleology\": [\n    {\n      \"year\": 2009,\n      \"claim\": \"Established HERC2 as an active participant in the DSB ubiquitin signaling cascade rather than a passive scaffold, by showing phospho-dependent recruitment of the RNF8/Ubc13 machinery.\",\n      \"evidence\": \"Co-IP, phospho-site mapping at Thr4827, siRNA, and IR-induced focus assays in human cells\",\n      \"pmids\": [\"20023648\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define how HERC2 levels of RNF168 are maintained mechanistically\", \"Catalytic versus scaffold contribution of HERC2 to chain formation not separated\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Demonstrated HERC2 as a bona fide E3 ligase with catalytic Cys4762 that degrades BARD1-uncoupled BRCA1, defining a quality-control role over BRCA1 stoichiometry.\",\n      \"evidence\": \"In vitro ubiquitination with catalytic mutant, Co-IP, and checkpoint epistasis in human cells\",\n      \"pmids\": [\"20631078\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological conditions favoring BRCA1 versus BARD1 binding not defined\", \"Chain linkage type on BRCA1 not characterized\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Linked HERC2 to circadian-regulated nucleotide excision repair by showing it drives oscillatory XPA turnover.\",\n      \"evidence\": \"Timed tissue-extract repair assays and XPA Western blots in mouse liver\",\n      \"pmids\": [\"20304803\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct ubiquitination of XPA by HERC2 not reconstituted in this study\", \"Single-lab; in vitro extract system\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed a non-catalytic HERC2 function: its RLD2 domain stimulates UBE3A/E6AP ligase activity, providing a molecular link to Angelman/E6AP biology.\",\n      \"evidence\": \"Domain-mapped Co-IP and in vitro/cell ubiquitination assays with catalytic-dead HERC2\",\n      \"pmids\": [\"21493713\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological substrates affected by HERC2-stimulated E6AP not defined here\", \"Structural basis of stimulation not resolved at this stage\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Placed HERC2 at the replication fork through Claspin association and regulation of origin firing and MCM2 phosphorylation.\",\n      \"evidence\": \"Co-IP, DNA fiber assays, and phospho-MCM2 blots with double knockdown in human cells\",\n      \"pmids\": [\"21775519\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether HERC2 ubiquitinates a fork component was not established\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identified the ZZ zinc finger as a SUMO-binding module and showed SUMOylation cooperates with T4827 phosphorylation to assemble the RNF8-Ubc13 complex at DSBs.\",\n      \"evidence\": \"PIAS4 knockdown, domain mutagenesis, SUMO-binding assays, and focus formation in human cells\",\n      \"pmids\": [\"22508508\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"SUMO acceptor sites on HERC2 not fully mapped\", \"Quantitative interplay of SUMO and phospho signals not resolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defined a HERC2-NEURL4 module that controls centrosome architecture via CP110 and ubiquitin-dependent regulation, extending HERC2 function to the centrosome.\",\n      \"evidence\": \"AP-MS, high-resolution imaging, and RNAi rescue with structure-function transgenes\",\n      \"pmids\": [\"22261722\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct ubiquitination targets at the centrosome incompletely enumerated at this stage\", \"Mechanism of pericentriolar material defect not fully resolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showed ATR-mediated XPA Ser196 phosphorylation antagonizes HERC2 binding and ubiquitination, defining a damage-responsive switch controlling XPA stability.\",\n      \"evidence\": \"Phospho-mutant reconstitution in XPA-null cells with Co-IP, ubiquitination, and chromatin retention assays\",\n      \"pmids\": [\"23178497\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Coordination with circadian XPA control not integrated\", \"Structural basis of phospho-regulated dissociation unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Revealed a non-degradative HERC2 role in the p53 pathway, promoting p53 oligomerization and transcriptional activity via the CPH domain.\",\n      \"evidence\": \"Domain-mapped Co-IP, cross-linking oligomerization assays, and transcription reporters in human cells\",\n      \"pmids\": [\"24722987\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How HERC2 mechanically catalyzes tetramer assembly unresolved\", \"Relationship to HERC2 ligase activity not addressed\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Connected HERC2 to iron homeostasis by identifying it as the E3 ligase degrading FBXL5, thereby influencing IRP2 regulation and intracellular iron.\",\n      \"evidence\": \"Proteomics-guided Co-IP, ubiquitination assay, and iron measurement with HERC2 knockdown\",\n      \"pmids\": [\"24778179\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Iron-dependence of the FBXL5 interaction not mechanistically resolved here\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Established a HERC2-USP20 axis controlling Claspin-ATR-Chk1 signaling, with ATR phosphorylation of USP20 dissociating HERC2 to stabilize the checkpoint.\",\n      \"evidence\": \"DUB screen, Co-IP, phospho-mapping, and Chk1 checkpoint assays (two converging papers)\",\n      \"pmids\": [\"25355518\", \"25326330\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Chain linkage on USP20 not detailed\", \"Quantitative thresholds of stress-induced switching unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Linked HERC2 to histone H2A ubiquitin dynamics by regulating USP16 levels and damage-induced ubiquitin foci.\",\n      \"evidence\": \"Domain-mapped Co-IP, in vitro deubiquitination, and ubiquitin focus imaging\",\n      \"pmids\": [\"25305019\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether HERC2 ubiquitinates USP16 directly not shown\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showed HERC2 directs K48 polyubiquitination of USP33 with p97-dependent processing, expanding its substrate repertoire to a centriole-relevant DUB.\",\n      \"evidence\": \"Quantitative MS, Co-IP, ubiquitination assay, and p97 inhibition in human cells\",\n      \"pmids\": [\"24855649\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct catalytic ubiquitin transfer by HERC2 onto USP33 inferred from cellular assays\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined HERC2 as the E3 ligase for iron-dependent NCOA4 degradation, placing it at the intersection of ferritinophagy and proteasomal control.\",\n      \"evidence\": \"Co-IP, ubiquitination assay, iron-dependent interaction, and zebrafish erythropoiesis model\",\n      \"pmids\": [\"26436293\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of iron-sensing not yet resolved at this stage\", \"Relative contribution of UPS versus autophagy to NCOA4 turnover unclear\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstrated HERC2 is essential for development independently of p53 and that haploinsufficiency causes Purkinje cell loss and motor impairment.\",\n      \"evidence\": \"Herc2 knockout, p53 double-knockout epistasis, behavioral and histological phenotyping in mice\",\n      \"pmids\": [\"27528230\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific substrate(s) underlying lethality not identified\", \"Mechanism of Purkinje cell vulnerability unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Connected HERC2 to a SIRT1-driven LKB1 degradation pathway regulating arterial remodeling.\",\n      \"evidence\": \"DOC-domain Co-IP, K64 mutagenesis, ChIP, and in vivo lentiviral knockdown\",\n      \"pmids\": [\"27259994\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct LKB1 ubiquitination by HERC2 inferred\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Established the E3 ligase activity of HERC2 as required for G-quadruplex suppression by promoting RPA loading and RPA2 ubiquitination in BLM/WRN helicase complexes.\",\n      \"evidence\": \"In vitro RPA-release assay, CRISPR catalytic-site deletion, G4 imaging, and epistasis in human cells\",\n      \"pmids\": [\"30279242\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How HERC2 mechanically releases RPA onto ssDNA unresolved\", \"Genomic distribution of HERC2-dependent G4 suppression not mapped\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Resolved the RPA2 regulatory loop, showing HERC2 promotes ATR-induced RPA2 Ser33 phosphorylation then ubiquitinates and degrades phospho-RPA2 to support G4 suppression.\",\n      \"evidence\": \"Co-IP, ubiquitination assay, CRISPR catalytic mutant, and phospho-RPA2 blots with ATR inhibitor epistasis\",\n      \"pmids\": [\"31582797\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct catalysis of RPA2 ubiquitination not reconstituted in vitro here\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Showed HERC2 transcriptionally regulates MDM2 within an oligomeric p53/HERC2/NEURL4 complex, with DNA damage dissociating MDM2 to activate p53.\",\n      \"evidence\": \"Co-IP, MDM2 promoter reporter assays, and knockdown in human cells\",\n      \"pmids\": [\"31665549\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which HERC2 affects MDM2 promoter activity not defined\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Placed HERC2 downstream of NudCL2 in centriole duplication control via regulation of USP33.\",\n      \"evidence\": \"CRISPR KO, rescue epistasis, Co-IP, and quantitative proteomics in human cells\",\n      \"pmids\": [\"31427565\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How NudCL2 stabilizes HERC2 structurally unknown\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Provided structural basis for the dual-reader function of the HERC2 ZZ domain, which binds histone H3 and SUMO1 tails at the same negatively charged site.\",\n      \"evidence\": \"Crystal structures of two complexes with NMR, mutagenesis, and fluorescence binding\",\n      \"pmids\": [\"32726574\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cellular consequences of H3 versus SUMO1 binding choice not resolved\", \"Competition dynamics in vivo unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Showed HERC2 controls nucleolar localization of BLM/WRN helicases and rDNA G4-dependent rRNA transcription, extending its G4 role to the nucleolus.\",\n      \"evidence\": \"CRISPR HECT deletion, colocalization imaging, and pre-rRNA transcription/CX-5461 sensitivity assays\",\n      \"pmids\": [\"33432007\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct substrate driving nucleolar helicase localization unknown\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Linked HERC2 loss to C-RAF/MKK3/p38 activation and NRF2-driven oxidative stress resistance, defining a signaling axis independent of p53.\",\n      \"evidence\": \"Patient fibroblasts, Co-IP, ubiquitylation, RAF/p38 inhibitor epistasis, and NRF2 blots\",\n      \"pmids\": [\"36241744\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct C-RAF ubiquitination by HERC2 not fully reconstituted\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified the HERC2 ZZ domain as a reader of arginylated (Nt-R) cargo, connecting HERC2 to N-degron pathways and autophagy/proteasome targeting.\",\n      \"evidence\": \"NMR titration, HERC2 DOC crystal structure, mutagenesis, and immunofluorescence\",\n      \"pmids\": [\"35411094\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional autophagy targeting based on imaging alone\", \"In vivo arginylated substrates not identified\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showed NRF2 transcriptionally maintains HERC2, integrating HERC2 into iron and ferroptosis control via NCOA4/ferritin handling.\",\n      \"evidence\": \"NRF2 knockout, autophagy flux, iron measurement, and ferroptosis sensitivity assays\",\n      \"pmids\": [\"36724221\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct NRF2 binding at the HERC2 promoter not mapped here\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined an oncogenic HERC2 function in hepatocellular carcinoma, restraining PTP1B to sustain JAK2/STAT3 and PD-L1-mediated immune evasion.\",\n      \"evidence\": \"HERC2 KO/overexpression, Co-IP, PTP1B localization imaging, and in vivo mouse liver carcinogenesis models\",\n      \"pmids\": [\"36721234\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether HERC2 ubiquitinates PTP1B not established\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showed HERC2 ubiquitinates CP110 at centriolar satellites to promote ciliogenesis, with EHD1 controlling HERC2/satellite transport to the mother centriole.\",\n      \"evidence\": \"Co-IP, ubiquitination assay, satellite localization imaging, and ciliogenesis quantification with siRNA\",\n      \"pmids\": [\"37074924\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of EHD1-dependent transport unresolved\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Linked HERC2 to cardiac hypertrophy through K48-linked degradation of MeCP2 and downstream Lin28a derepression.\",\n      \"evidence\": \"Co-IP, K48 ubiquitination assay, and cardiac-specific overexpression in vivo\",\n      \"pmids\": [\"39499120\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct ubiquitination site on MeCP2 not mapped\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showed HERC2 ubiquitinates β-catenin to govern CYP2E1 transcription and protect against acetaminophen-induced liver injury.\",\n      \"evidence\": \"Co-IP, ubiquitination assay, liver-specific KO mice, scRNA-seq, and LNP delivery in vivo\",\n      \"pmids\": [\"39440550\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"β-catenin ubiquitination linkage type not detailed\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Characterized the disordered C-terminal tail of HERC2 as a stabilizer of the catalytic HECT C-lobe, implicating it as a flexible interaction scaffold.\",\n      \"evidence\": \"AlphaFold modeling, MD simulation, multidimensional NMR, and CD melting\",\n      \"pmids\": [\"39565083\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of tail-C-lobe contact inferred not tested\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Defined HERC2 as an autophagy regulator via the USP20-ULK1 axis, with HERC2 deficiency elevating USP20, stabilizing ULK1, and increasing autophagy flux.\",\n      \"evidence\": \"Patient fibroblasts, HERC2-USP20 Co-IP, lysosomal inhibitor assays, and p38 inhibitor epistasis\",\n      \"pmids\": [\"38570483\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct ULK1 stabilization mechanism by USP20 not fully resolved here\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Provided the structural and biochemical basis for iron-sensing, showing HERC2 recognizes [2Fe-2S]-bound NCOA4 through its CPH and newly defined INBD domains.\",\n      \"evidence\": \"Two crystal structures, in vitro reconstitution, iron-sulfur cluster biochemistry, and cellular ubiquitination/stability assays\",\n      \"pmids\": [\"40705422\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How iron cluster occupancy is dynamically sensed in vivo not fully resolved\", \"Whether other substrates use iron-dependent recognition unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defined a conserved DxDKDxD motif recognized by the HERC2 RLD2 domain that mediates UBE3A binding and broadens to DOCK10 and other brain-relevant proteins, with HERC2 stimulating DOCK10 GEF activity and dendritic spine formation.\",\n      \"evidence\": \"Crystal structures of RLD2 complexes, GEF activity assays, conservation analysis, and dendritic spine imaging in neurons (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.09.16.670041\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not peer-reviewed\", \"Physiological scope of additional DxDKDxD partners not validated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single giant scaffold coordinates its many catalytic and non-catalytic functions across distinct subcellular compartments and selects among its diverse substrates remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying regulatory logic for substrate selection across pathways\", \"Full-length structural architecture not solved\", \"Disease-causing mutation mapping to specific functional domains incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [1, 9, 12, 13, 27, 31]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 9, 13, 17, 31]},\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [20]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 5, 8, 32]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [3, 32]},\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [13, 31]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [6, 19, 26]},\n      {\"term_id\": \"GO:0005730\", \"supporting_discovery_ids\": [21]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [14]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [0, 1, 5, 7]},\n      {\"term_id\": \"R-HSA-69306\", \"supporting_discovery_ids\": [4, 10, 16, 17]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 9, 12, 13, 31]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [9, 13, 24, 31]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [6, 19, 26]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [13, 24, 30]}\n    ],\n    \"complexes\": [\"RNF8-Ubc13 DSB ubiquitin module\", \"p53/HERC2/NEURL4/MDM2 complex\", \"NEURL4-HERC2-CP110 centrosomal module\", \"BLM/WRN-RPA helicase complex\"],\n    \"partners\": [\"RNF8\", \"NCOA4\", \"UBE3A\", \"NEURL4\", \"USP20\", \"RPA2\", \"CP110\", \"USP33\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}