{"gene":"ERCC3","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":1990,"finding":"ERCC3 encodes a predicted DNA helicase containing seven consecutive helicase motifs conserved between two superfamilies of DNA and RNA helicases, and specifically corrects the nucleotide excision repair (NER) defect in xeroderma pigmentosum complementation group B (XP-B) rodent mutants.","method":"cDNA cloning, transfection complementation assay, sequence analysis","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — cloning and direct functional complementation of NER defect; foundational paper replicated widely","pmids":["2167179"],"is_preprint":false},{"year":1990,"finding":"ERCC3 cDNA transfection corrects UV sensitivity and unscheduled DNA synthesis (UDS) in complementation group 3 rodent mutants, establishing its role in early steps of the nucleotide excision repair pathway.","method":"Transfection/complementation assay, UDS measurement","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct functional reconstitution of NER activity, replicated in multiple studies","pmids":["2111438"],"is_preprint":false},{"year":1992,"finding":"SSL2 (yeast homolog of ERCC3/XPB) encodes an essential 95 kDa protein with ATP-dependent helicase motifs; an SSL2 allele mimicking the defective ERCC3 gene confers UV hypersensitivity, establishing it as the functional yeast homolog.","method":"Gene cloning, mutant allele construction, UV sensitivity assay","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic complementation and allele analysis in yeast, replicated across multiple labs","pmids":["1318786"],"is_preprint":false},{"year":1992,"finding":"RAD25 (SSL2) is an essential gene in S. cerevisiae; a mutation in the Walker type A nucleotide-binding motif (K392R) is lethal, indicating an essential role of its ATPase/helicase activity in viability. The gene functions in excision repair (epistasis with excision repair group genes), but not in other repair pathways.","method":"Gene deletion, site-directed mutagenesis, epistasis analysis, UV sensitivity assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis and mutagenesis of essential catalytic residue, replicated","pmids":["1333609"],"is_preprint":false},{"year":1992,"finding":"The Drosophila haywire gene encodes a protein with 66% identity to ERCC3; haywire mutants are recessive lethal or UV-sensitive, and flies with marginal haywire expression display motor defects and reduced lifespan, establishing the fly ortholog's function in NER and essential cellular processes.","method":"Genetic analysis, mutant characterization, UV sensitivity assay","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — ortholog identification with multiple alleles and phenotypic characterization","pmids":["1458540"],"is_preprint":false},{"year":1992,"finding":"Cell-free extracts from CHO ERCC3-deficient (complementation group 3) cells are defective in in vitro DNA excision repair; complementation by mixing with group 1 extracts demonstrates that ERCC3 protein is directly required for enzymatic incision of damaged DNA or preincision reactions.","method":"Cell-free excision repair assay, in vitro complementation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution in vitro with cell extracts, direct biochemical evidence","pmids":["1551896"],"is_preprint":false},{"year":1993,"finding":"A temperature-sensitive rad25 (SSL2) mutant shows rapid cessation of growth and large decrease in poly(A)+ RNA synthesis at the restrictive temperature, demonstrating a general and direct requirement of RAD25 (XPB ortholog) in RNA polymerase II transcription.","method":"Conditional lethal mutant, poly(A)+ RNA measurement, gene-specific Northern blot","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional lethal mutant with direct measurement of transcription defect, replicated","pmids":["7693549"],"is_preprint":false},{"year":1994,"finding":"Purified RAD25 (yeast XPB/ERCC3 ortholog) exhibits single-stranded DNA-dependent ATPase and DNA helicase activities. A thermolabile rad25 extract shows transcriptional defect correctable by adding RAD25 protein. The rad25-799am allele (repair-defective) is proficient in RNA Pol II transcription, separating DNA repair from transcription functions. The Arg-392 ATP-binding motif mutant is defective in transcription, implicating helicase activity in promoter opening.","method":"Protein purification, in vitro ATPase/helicase assay, in vitro transcription complementation, site-directed mutagenesis","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — purified protein with in vitro biochemical reconstitution, mutagenesis, multiple orthogonal methods","pmids":["8202161"],"is_preprint":false},{"year":1994,"finding":"The COOH terminus of SSL2/RAD25 is essential for overall genomic NER and transcription-coupled repair; the SSL2-XP allele (resembling the mutated ERCC3 from XP-B/CS-C patients) causes complete deficiency in cyclobutane pyrimidine dimer removal from the overall genome and transcription-coupled repair.","method":"Dimer removal assay in expressed genes and genome overall, UV sensitivity","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct measurement of NER in specific genomic contexts using well-defined allele","pmids":["8294433"],"is_preprint":false},{"year":1994,"finding":"Mutations in the ATPase motif (helicase domain I), other helicase domains, and the potential helix-turn-helix DNA-binding motif of ERCC3 abolish NER complementation activity; C-terminal deletions implicate a distinct determinant for DNA repair. A functional epitope-tagged ERCC3 accumulates in the nucleus, and deletion of the putative NLS does not impair nuclear localization.","method":"Site-directed mutagenesis, deletion mutagenesis, UV complementation assay, immunofluorescence","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic mutagenesis with multiple constructs and functional readout","pmids":["8196650"],"is_preprint":false},{"year":1994,"finding":"Recombinant XPB/ERCC3 protein produced in baculovirus system exhibits DNA helicase activity, directly demonstrating that XPB itself is a DNA helicase.","method":"Baculovirus expression, protein purification, in vitro helicase assay","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro helicase reconstitution with purified recombinant protein","pmids":["7937133"],"is_preprint":false},{"year":1994,"finding":"Yeast RAD3 protein directly binds to SSL2 (RAD25/XPB) protein in vitro via an N-terminal, potentially non-catalytic domain of SSL2. A DNA repair-defective allele of SSL2 is not defective in binding to transcription factor b (TFIIH), genetically separating the repair and transcription-binding functions.","method":"In vitro immunoprecipitation, yeast two-hybrid, genetic analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal in vitro binding with genetic separation of function","pmids":["8171014"],"is_preprint":false},{"year":1994,"finding":"HBX (hepatitis B virus X protein) complexes with wild-type p53 and inhibits the in vitro association of p53 with ERCC3, as well as p53-mediated transcriptional activation, revealing ERCC3 as a p53-interacting transcription factor.","method":"In vitro protein-protein interaction assay, transcription assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single-lab in vitro binding assay; indirect (HBX inhibits p53-ERCC3 interaction)","pmids":["8134379"],"is_preprint":false},{"year":1996,"finding":"TFIIH isolated from XP-B patient cells (XP11BE) carrying a frameshift mutation in XPB shows reduced 3'→5' XPB helicase activity and DNA-dependent ATPase activity, and causes a severe NER defect and decreased basal transcription activity in vitro, establishing that XPB's helicase activity is required for both NER and transcription.","method":"Immunopurification of TFIIH, helicase/ATPase assays, in vitro transcription, NER assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — purified patient-derived TFIIH with multiple biochemical assays demonstrating mechanistic link","pmids":["8663148"],"is_preprint":false},{"year":1996,"finding":"XPB and XPD are components of the p53-dependent apoptosis pathway: primary fibroblasts from XP-B or XP-D patients (but not XP-A or XP-C) are deficient in p53-mediated apoptosis; this deficiency is rescued by transfer of the wild-type XPB or XPD gene, and the carboxy-terminus of p53 is required for apoptosis.","method":"Microinjection of expression vectors, retroviral infection, complementation assay, apoptosis measurement","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic complementation with specific rescue, multiple cell types tested","pmids":["8675009"],"is_preprint":false},{"year":1996,"finding":"Reconstituted yeast TFIIH requires both Rad3 and Rad25 (XPB ortholog) helicase subunits for in vitro NER-mediated incision of UV-damaged DNA; the Rad25 Arg-392 (ATP-binding motif) mutant abolishes NER but not CTD kinase activity, which is dispensable for incision.","method":"TFIIH reconstitution, in vitro NER incision assay, mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted in vitro NER system with purified proteins and mutagenesis","pmids":["8631896"],"is_preprint":false},{"year":1997,"finding":"XPB directly interacts with SUG1 (a subunit of the 26S proteasome), validated by yeast two-hybrid, baculovirus co-expression, co-purification with TFIIH holocomplex, and co-immunoprecipitation; overexpression of SUG1 arrests transcription; a mutant XPB (XP-B patient mutation) shows diminished interaction with SUG1.","method":"Yeast two-hybrid, baculovirus co-expression, co-purification, co-immunoprecipitation","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods confirming interaction, including functional consequence of overexpression","pmids":["9173976"],"is_preprint":false},{"year":1999,"finding":"Reconstituted baculovirus-expressed TFIIH with mutated XPB (helicase-dead) is unable to initiate transcription; XPB helicase is absolutely required for promoter opening at the transcription start site, whereas XPD helicase is dispensable but stimulates transcription and anchors CAK to TFIIH.","method":"TFIIH reconstitution from recombinant subunits, in vitro transcription, mutagenesis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — full reconstitution of TFIIH from recombinant proteins with mutagenesis and functional assay","pmids":["10024882"],"is_preprint":false},{"year":1999,"finding":"Mutations in XPB found in XP-B/CS patients decrease the transcriptional activity of immunopurified TFIIH by preventing promoter opening; this defect can be circumvented by artificial opening of the promoter, demonstrating that XPB is specifically required for the promoter-opening step in transcription.","method":"Immunopurification of patient TFIIH, in vitro transcription, promoter opening assay","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — purified patient TFIIH with multiple biochemical assays and functional rescue","pmids":["10064601"],"is_preprint":false},{"year":1999,"finding":"XPB helicase activity of TFIIH is primarily responsible for preventing premature arrest of early elongation intermediates during RNA polymerase II promoter escape, demonstrated with TFIIH mutants in a reconstituted minimal transcription system.","method":"Reconstituted in vitro transcription system, TFIIH mutant analysis, promoter escape assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted system with purified factors and defined mutants","pmids":["10428772"],"is_preprint":false},{"year":2002,"finding":"The p52 subunit of TFIIH physically interacts with XPB and is required to anchor XPB within TFIIH; deletion of the C-terminal region of p52 prevents promoter opening and abolishes NER and transcription activities, demonstrating p52 regulates XPB function through direct interaction.","method":"Reconstituted in vitro transcription/NER, deletion mutagenesis, co-immunoprecipitation, domain mapping","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted in vitro system with mutagenesis and multiple functional assays","pmids":["12080057"],"is_preprint":false},{"year":2002,"finding":"The ERCC3 helicase activity of TFIIH plays a regulatory role in stimulating promoter escape during transcriptional activation; the helicase acts throughout the promoter-escape phase (up to ~10-nt RNA synthesis) to increase the proportion of productive complexes that escape the promoter.","method":"Reconstituted in vitro transcription, TFIIH helicase mutants, transcription elongation analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted transcription system with defined TFIIH mutants","pmids":["11818577"],"is_preprint":false},{"year":2002,"finding":"HCV NS5A protein inhibits the p53-ERCC3 protein-protein complex formation in vitro, as shown by co-immunoprecipitation and pull-down assays.","method":"Co-immunoprecipitation, pull-down assay","journal":"Biochimica et biophysica acta","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single-lab co-IP/pulldown, indirect disruption of p53-ERCC3 complex","pmids":["12379483"],"is_preprint":false},{"year":2003,"finding":"The ERCC3 helicase activity of TFIIH alleviates PC4-mediated transcriptional repression via beta-gamma bond hydrolysis of ATP; this requires ERCC3 helicase but not ERCC2 helicase or CDK7 kinase activity, suggesting ERCC3 relieves topological constraints imposed by PC4 at promoters.","method":"Reconstituted in vitro transcription, recombinant TFIIH with defined enzymatic mutants","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted in vitro system with specific enzymatic mutants discriminating ERCC3 from other TFIIH activities","pmids":["12590132"],"is_preprint":false},{"year":2004,"finding":"Serine 751 (S751) of XPB is phosphorylated in vivo; this phosphorylation inhibits NER (a phosphomimicking S751E mutant cannot correct NER defect in XP-B cells) without affecting TFIIH-dependent transcription. S751 phosphorylation does not impair DNA unwinding by TFIIH but prevents 5' incision by ERCC1-XPF endonuclease.","method":"In vivo phosphorylation detection, microinjection, NER and transcription assays, mutagenesis (S751E, S751A)","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — identification of phosphorylation site, mutagenesis, in vivo and in vitro functional assays with defined mechanism","pmids":["15549133"],"is_preprint":false},{"year":2005,"finding":"XPB ATPase activity (not helicase activity per se) drives promoter opening for RNA Pol II transcription; XPB helicase mutants that retain ATPase activity are proficient for promoter opening but defective in promoter escape, paralleling sigma54 bacterial transcription.","method":"XPB helicase mutant characterization, in vitro transcription assay","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — specific mutants separating ATPase from helicase activity, functional assays","pmids":["15937491"],"is_preprint":false},{"year":2005,"finding":"The beta subunit of TFIIE directly stimulates XPB helicase and ATPase activities; TFIIE beta mutants defective for XPB helicase stimulation but competent for PIC assembly are defective in in vitro transcription, establishing TFIIE beta as a co-factor that enhances XPB activity during transcription initiation and promoter escape.","method":"In vitro helicase/ATPase assay, mutagenesis of TFIIE beta, reconstituted transcription","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro assay with mutagenesis and functional consequence in transcription","pmids":["15917439"],"is_preprint":false},{"year":2006,"finding":"Crystal structures of an archaeal XPB homolog reveal two RecA-like helicase domains, a DNA damage recognition domain (DRD), a unique RED motif, and a flexible thumb motif (ThM). RED motif mutations dramatically reduce helicase activity; the substrate specificity is altered by DNA damage (AfXPB unwinds dsDNA with 3' extensions but not blunt-ended dsDNA unless it contains a lesion).","method":"X-ray crystallography, site-directed mutagenesis, in vitro helicase assay","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional validation by mutagenesis and helicase assay","pmids":["16600867"],"is_preprint":false},{"year":2006,"finding":"XPB DNA repair-deficient cells (XPB/XPD mutants but not XPA mutants) show increased HIV and MLV retroviral transduction efficiency and greater retroviral cDNA stability, establishing a role for TFIIH XPB in degradation of retroviral cDNA as a cellular defense.","method":"Retroviral transduction assay, quantitative PCR, XPB mutant cell lines","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined mutant cell lines with multiple viral systems, single lab","pmids":["16537383"],"is_preprint":false},{"year":2007,"finding":"The p52 subunit of TFIIH interacts with XPB and stimulates its ATPase activity; the XP-B patient mutation F99S weakens this interaction and the resulting ATPase stimulation, explaining the damaged DNA opening defect. Mutations in helicase motifs III (T469A) and VI (Q638A) that inhibit XPB helicase activity preserve NER function, demonstrating that XPB ATPase (not helicase) activity drives damaged DNA opening in NER.","method":"Protein-protein interaction assay, ATPase assay, mutagenesis, in vitro NER reconstitution","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with mutagenesis and ATPase/helicase dissection","pmids":["17466626"],"is_preprint":false},{"year":2007,"finding":"Archaeal XPB (from S. solfataricus) is a ssDNA-stimulated ATPase without helicase activity in vitro; XPB physically interacts with a conserved archaeal partner protein Bax1 (encoded by the adjacent gene), establishing a novel XPB-associated endonuclease complex in archaea.","method":"ATPase assay, helicase assay, in vitro co-purification/interaction assay","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct in vitro biochemical characterization, single lab","pmids":["18177890"],"is_preprint":false},{"year":2007,"finding":"XPB regulates the recruitment and redistribution of NER proteins at UV damage sites; delayed or absent XPF recruitment is a hallmark of XPB mutations, and redistribution of NER proteins after repair is dependent on functional XPB.","method":"Local UV irradiation through micropore filters, fluorescent antibody labeling, live-cell imaging","journal":"DNA repair","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with defined mutant cell lines and functional consequence","pmids":["17509950"],"is_preprint":false},{"year":2010,"finding":"XPB (p89), but not other TFIIH subunits, re-localizes to centrosomes and adjacent parts of the mitotic spindle during cell division (prophase through telophase); XPB interacts with the centrosomal protein gamma-tubulin; C-terminal truncations of XPB abolish centrosomal association.","method":"Immunofluorescence, GFP-fusion live imaging, co-immunoprecipitation, deletion constructs","journal":"Cellular oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization by live imaging and co-IP with functional consequence of truncations; single lab","pmids":["20208140"],"is_preprint":false},{"year":2011,"finding":"Triptolide covalently binds to human XPB (ERCC3), a subunit of TFIIH, and inhibits its DNA-dependent ATPase activity, leading to inhibition of RNA polymerase II-mediated transcription and NER.","method":"Chemical biology binding assay, ATPase inhibition assay, transcription inhibition assay","journal":"Nature chemical biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — covalent modification identified, ATPase inhibition demonstrated with mechanistic follow-up","pmids":["21278739"],"is_preprint":false},{"year":2011,"finding":"XPB functions in ATR kinase activation in non-replicating cells exposed to bulky DNA adducts: genetic and pharmacological inhibition of XPB prevents RPA accumulation on damaged chromatin and abrogates ATR signaling in response to NA-AAF and camptothecin, revealing a role for TFIIH in ATR activation independent of XPA.","method":"siRNA knockdown, pharmacological XPB inhibition, immunoblot for ATR substrates, RPA chromatin fractionation","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic and pharmacological inhibition with mechanistic readout; single lab","pmids":["28592488"],"is_preprint":false},{"year":2012,"finding":"Tfb6, a newly identified TFIIH subunit, forms a heterodimer with Ssl2 (XPB) and facilitates dissociation of Ssl2 from TFIIH after transcription initiation, but does not dissociate Ssl2 from the fully assembled transcription preinitiation complex.","method":"TFIIH subunit identification, co-purification, in vitro dissociation assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct biochemical characterization of new binding partner and functional consequence","pmids":["22411836"],"is_preprint":false},{"year":2013,"finding":"Crystal structure of the C-terminal half of human XPB (residues 494-782) at 1.8 Å resolution reveals HD2 and a C-terminal extension with structural similarity to RIG-I; this supports a structural model for XPF-XPB-DNA complex for 5' incision. The XP11BE patient mutation reduces XPB solubility and lowers intracellular TFIIH levels, impairing both DNA repair and transcription.","method":"X-ray crystallography, Western blot, mutant protein analysis","journal":"Acta crystallographica. Section D, Biological crystallography","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional validation of disease mutation","pmids":["23385459"],"is_preprint":false},{"year":2014,"finding":"Triptolide covalently modifies Cys342 of XPB via its 12,13-epoxide group; mutation of Cys342 to threonine (C342T) confers resistance to triptolide and replacement of endogenous wild-type XPB with C342T in HEK293T cells renders them completely resistant to triptolide, validating XPB as the physiologically relevant target.","method":"Mass spectrometry identification of modified residue, site-directed mutagenesis, CRISPR/Cas9 endogenous replacement, cell viability assay","journal":"Angewandte Chemie (International ed. in English)","confidence":"High","confidence_rationale":"Tier 1 / Strong — precise residue identification, mutagenesis, endogenous gene replacement with functional rescue","pmids":["25504624"],"is_preprint":false},{"year":2014,"finding":"XPB and XPD bind to G-quadruplex (G4) DNA genome-wide; XPB binds G4 DNA while XPD is a robust G4 helicase; 40% of XPB/XPD ChIP-Seq binding sites overlap with G4 motifs, particularly near transcription start sites of highly transcribed genes.","method":"ChIP-Seq in human cells, biochemical G4 binding/helicase assay","journal":"Nature chemical biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP-Seq with biochemical validation, single lab","pmids":["24609361"],"is_preprint":false},{"year":2018,"finding":"Spironolactone (SPL) promotes proteasome-dependent degradation of XPB (but not via mineralocorticoid receptor); proteasome blockade or XPB overexpression prevents SPL-mediated suppression of NF-κB and AP-1 inflammatory signalling; XP patient fibroblasts with N-terminal (but not C-terminal) XPB mutations are insensitive to SPL-mediated XPB degradation.","method":"Proteasome inhibitor, siRNA knockdown, XPB overexpression, chromatin immunoprecipitation, patient-derived fibroblasts","journal":"Cardiovascular research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal approaches with mechanistic follow-up; single lab","pmids":["29036418"],"is_preprint":false},{"year":2019,"finding":"Spironolactone-induced XPB degradation requires CDK7 kinase activity and SCFFBXL18 E3 ubiquitin ligase (comprising Skp1, Cul1, FBXL18, and Rbx1); CDK7 phosphorylates XPB at Ser90 to trigger recognition by SCFFBXL18 for polyubiquitination and proteasomal degradation.","method":"siRNA library screening, ubiquitination assay, co-immunoprecipitation, site-directed mutagenesis (S90)","journal":"Genes to cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional siRNA screen with biochemical validation of key components; single lab","pmids":["30762924"],"is_preprint":false},{"year":2020,"finding":"Spironolactone rapidly inhibits HIV-1 transcription by degrading XPB, reducing RNA polymerase II recruitment to the HIV-1 genome; shRNA knockdown of XPB confirmed that XPB degradation is the mechanism of action. SP also inhibits HIV reactivation from latency in resting CD4+ T cells.","method":"shRNA knockdown, RNAPII ChIP, HIV transcription assay, latency reactivation assay","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — shRNA confirmation and ChIP-based mechanistic readout; single lab","pmids":["33239456"],"is_preprint":false},{"year":2020,"finding":"p52/p8 subunits of TFIIH act as master regulators of XPB ATPase activity: XPB ATPase can be activated by DNA or p52/p8, but when both are present p52/p8 dominates and acts as a speed limiter. XPB translocase activity (within core TFIIH) is enhanced by XPA, which increases processivity without altering ATPase rate.","method":"ATPase assay, translocase assay, crystal structure of p52/p8, functional mutagenesis, cryo-EM-guided analysis","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional mutagenesis and multiple enzymatic assays","pmids":["33196848"],"is_preprint":false},{"year":2020,"finding":"EBV SM protein recruits XPB to EBV lytic promoters during lytic replication; depletion of XPB by spironolactone or siRNA inhibits SM-dependent late lytic gene transcription but not other EBV or cellular gene transcription, demonstrating XPB is specifically co-opted for EBV SM-mediated transcriptional activation.","method":"ChIP, siRNA knockdown, spironolactone treatment, gene-specific transcription assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and siRNA with functional transcription readout; single lab","pmids":["32434920"],"is_preprint":false},{"year":2021,"finding":"The XPB/Ssl2 dsDNA translocase activity drives transcription start-site (TSS) scanning in S. cerevisiae; processive translocation by holo-TFIIH requires the TFIIH kinase module as a processivity factor. Human TFIIH (holo and core) does not exhibit processive translocation, consistent with absence of TSS scanning in humans.","method":"dsDNA translocase assay, ATPase assay, holo- vs. core-TFIIH comparison across species","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct biochemical assay with human and yeast complexes, mechanistic dissection","pmids":["33453189"],"is_preprint":false},{"year":2021,"finding":"Ssl2 (XPB) ATPase activity drives TSS scanning processivity in S. cerevisiae; distinct ssl2 alleles cause upstream or downstream TSS shifts genome-wide; genetic interactions with other initiation factors are consistent with Ssl2 modulating scanning processivity through a conserved residue interaction network.","method":"Isolation of novel ssl2 alleles, TSS mapping (PRO-Seq equivalent), genetic interaction analysis","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple alleles, genome-wide TSS mapping, genetic epistasis","pmids":["34652274"],"is_preprint":false},{"year":2024,"finding":"A spirocycle acrylamide compound (ZL-12A) covalently reacts with Cys342 of ERCC3 (same residue as triptolide) and promotes ERCC3 degradation as a monofunctional degrader; spironolactone also reacts with ERCC3_C342. ZL-12A and triptolide cross-antagonize each other's protein degradation profiles, demonstrating that covalent ligands targeting the same cysteine can produce distinct functional outcomes.","method":"Activity-based protein profiling (ABPP), cysteine-directed chemoproteomics, protein degradation assay, cross-antagonism experiment","journal":"Journal of the American Chemical Society","confidence":"High","confidence_rationale":"Tier 1 / Strong — site-specific covalent modification identified, functional degradation validated, cross-antagonism experiment","pmids":["38569115"],"is_preprint":false},{"year":2007,"finding":"XPB participates in mRNA export in fission yeast (Ptr8p/XPB); a ptr8-1 temperature-sensitive mutant accumulates poly(A)+ RNA in the nucleus; human XPB rescues both UV sensitivity and mRNA export defects; functional interaction between Ptr8p and Tho2p (TREX complex) was demonstrated.","method":"Conditional mutant, poly(A)+ RNA localization, cross-species complementation, co-immunoprecipitation","journal":"Genes to cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization and functional complementation in yeast; single lab","pmids":["17212653"],"is_preprint":false},{"year":2005,"finding":"Ssl2 (XPB yeast ortholog) interacts with Hsp90 chaperone machinery; multiple SSL2 mutant alleles exhibit pronounced growth defects when co-expressed with mutant Hsp90; Ssl2 protein co-purifies with Hsp90 and Sti1, suggesting Ssl2 function depends on Hsp90.","method":"Genetic screen, co-purification, co-immunoprecipitation","journal":"Current genetics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single-lab co-purification with functional consequence only in genetic sensitized background","pmids":["15871019"],"is_preprint":false},{"year":2011,"finding":"Ssl2 (XPB) and TFIIB functionally interact in start-site selection and gene looping: an ssl2 suppressor allele (H508R) suppresses the cold-sensitive growth defect and TSS selection defect of the sua7-1 (TFIIB E62K) mutation; Ssl2 associates with both promoter and terminator regions.","method":"Genetic suppressor screen, start-site mapping, ChIP","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with ChIP evidence; single lab","pmids":["22081613"],"is_preprint":false}],"current_model":"ERCC3/XPB is a 3'→5' DNA helicase and ATPase that functions as an essential core subunit of the general transcription factor TFIIH: its ATPase activity (not helicase per se) drives promoter DNA opening during RNA polymerase II transcription initiation and damaged-DNA opening during nucleotide excision repair (NER), while its helicase activity facilitates promoter escape and TSS scanning; within TFIIH, its activity is stimulated and speed-limited by the p52/p8 subcomplex and co-activated by TFIIE-β, it is phosphorylated on S751 (selectively inhibiting NER incision) and S90 (triggering SCFFBXL18-mediated proteasomal degradation), it interacts with SUG1/26S proteasome and Hsp90 chaperone machinery, and its Cys342 is the site of covalent modification by triptolide and spironolactone-related compounds that inhibit or degrade XPB to suppress transcription and NER."},"narrative":{"mechanistic_narrative":"ERCC3/XPB is an essential 3'→5' DNA helicase and DNA-dependent ATPase that operates as a core catalytic subunit of the general transcription factor TFIIH, coupling RNA polymerase II transcription to nucleotide excision repair (NER) [PMID:2167179, PMID:1318786, PMID:7693549, PMID:8663148]. It was identified by functional complementation of the NER defect in xeroderma pigmentosum group B and rodent group-3 mutants [PMID:2167179, PMID:2111438, PMID:1551896], and its yeast ortholog SSL2/RAD25 established the gene as essential, with a lethal Walker-A (K392R) ATPase mutation [PMID:1333609] and a conditional allele that simultaneously arrests growth and poly(A)+ RNA synthesis, demonstrating a direct and general role in Pol II transcription [PMID:7693549]. Biochemical reconstitution from purified and recombinant subunits showed XPB to be a bona fide DNA helicase [PMID:8202161, PMID:7937133] whose activities are partitioned functionally: the ATPase activity—not helicase translocation per se—drives promoter opening at the transcription start site and damaged-DNA opening during NER, whereas the helicase/translocase activity governs promoter escape, prevents premature arrest of early elongation intermediates, and relieves topological constraints imposed by repressors such as PC4 [PMID:10024882, PMID:10064601, PMID:10428772, PMID:11818577, PMID:12590132, PMID:15937491, PMID:17466626]. In yeast, this same ATPase/translocase drives processive transcription start-site scanning, a function absent from human TFIIH [PMID:33453189, PMID:34652274]. Within TFIIH, XPB is anchored and its catalytic output regulated by the p52/p8 subcomplex, which stimulates and acts as a dominant speed-limiter of its ATPase, while TFIIE-β co-activates its helicase/ATPase and XPA enhances translocase processivity [PMID:12080057, PMID:15917439, PMID:17466626, PMID:33196848]. XPB function in NER requires its C-terminus and coordinates the recruitment and redistribution of downstream NER factors, including ERCC1-XPF for 5' incision [PMID:8294433, PMID:8196650, PMID:17509950, PMID:23385459]; phosphorylation of Ser751 selectively blocks NER incision without impairing transcription, separating its two roles post-translationally [PMID:15549133]. Structural studies of archaeal and human XPB define tandem RecA-like helicase domains, a DNA damage recognition domain, and the catalytic RED motif, and rationalize disease alleles that reduce XPB solubility and TFIIH levels [PMID:16600867, PMID:23385459]. Patient-derived XPB mutations underlie the combined NER/transcription deficiencies of xeroderma pigmentosum group B and XP-B/Cockayne syndrome [PMID:8663148, PMID:10064601, PMID:23385459]. XPB Cys342 is the covalent attachment site for triptolide and spironolactone-related compounds that inhibit its ATPase or trigger its degradation, shutting down transcription and NER and providing a chemically validated drug target [PMID:21278739, PMID:25504624, PMID:38569115].","teleology":[{"year":1990,"claim":"Established the molecular identity of ERCC3 as a candidate DNA helicase and its causal role in a defined repair defect, framing all subsequent mechanistic work.","evidence":"cDNA cloning and transfection complementation of the NER/UDS defect in XP-B and rodent group-3 mutants","pmids":["2167179","2111438"],"confidence":"High","gaps":["Helicase activity was predicted from sequence motifs, not yet biochemically demonstrated","Role in transcription not yet known"]},{"year":1992,"claim":"Cross-species genetics (yeast SSL2/RAD25, Drosophila haywire) established ERCC3 as an essential gene whose catalytic ATPase/helicase function is required for viability, not merely repair.","evidence":"Gene deletion, Walker-A K392R lethality, allele analysis, epistasis, and ortholog phenotyping in yeast and flies; in vitro excision-repair complementation in CHO extracts","pmids":["1318786","1333609","1458540","1551896"],"confidence":"High","gaps":["Mechanistic basis of essentiality unresolved","Whether essentiality reflects transcription versus repair not yet separated"]},{"year":1993,"claim":"Resolved why the gene is essential beyond repair by showing a direct, general requirement in RNA polymerase II transcription.","evidence":"Temperature-sensitive rad25 mutant with collapse of poly(A)+ RNA synthesis at restrictive temperature","pmids":["7693549"],"confidence":"High","gaps":["The specific transcriptional step requiring XPB not yet defined","Biochemical activity underlying transcription role unproven"]},{"year":1994,"claim":"Demonstrated XPB is itself an ATP-dependent DNA helicase and genetically separated its repair and transcription functions, anchoring its role within TFIIH.","evidence":"Purified/recombinant RAD25 and baculovirus XPB helicase and ssDNA-dependent ATPase assays; repair-defective vs transcription-defective alleles; RAD3-SSL2 in vitro binding; systematic mutagenesis with NER readout","pmids":["8202161","7937133","8294433","8196650","8171014"],"confidence":"High","gaps":["Whether ATPase or helicase activity drives each substep not yet resolved","Regulation of XPB within TFIIH undefined"]},{"year":1996,"claim":"Patient-derived TFIIH analysis linked XPB helicase/ATPase loss directly to combined NER and basal transcription defects, and reconstituted yeast TFIIH confirmed XPB is required for incision.","evidence":"Immunopurified XP-B TFIIH with helicase/ATPase, transcription and NER assays; reconstituted yeast TFIIH NER incision with Rad25 ATP-motif mutant","pmids":["8663148","8631896"],"confidence":"High","gaps":["CTD kinase activity shown dispensable for incision but its broader role unclear","Exact catalytic step of XPB in incision not yet pinned"]},{"year":1999,"claim":"Defined XPB helicase as absolutely required for promoter opening and for preventing arrest during promoter escape in fully reconstituted transcription systems.","evidence":"TFIIH reconstituted from recombinant subunits with helicase-dead XPB; patient TFIIH promoter-opening assays with artificial-bubble rescue; minimal reconstituted promoter-escape assays","pmids":["10024882","10064601","10428772"],"confidence":"High","gaps":["Whether ATP hydrolysis or strand translocation per se opens the promoter not yet distinguished"]},{"year":2005,"claim":"Dissected the catalytic logic of XPB: ATPase activity drives promoter opening while helicase translocation drives promoter escape, with TFIIE-β as a co-activator.","evidence":"XPB helicase mutants retaining ATPase activity in in vitro transcription; TFIIE-β mutagenesis and helicase/ATPase stimulation assays","pmids":["15937491","15917439"],"confidence":"High","gaps":["Structural basis of ATPase-driven opening not yet visualized","How TFIIE-β engages XPB structurally undefined"]},{"year":2007,"claim":"Extended the ATPase-versus-helicase distinction to NER, showing p52-stimulated XPB ATPase, not helicase, opens damaged DNA, and explained an XP-B patient mutation mechanistically.","evidence":"p52-XPB interaction and ATPase stimulation assays; F99S, T469A, Q638A mutants in reconstituted NER; localization of NER-factor recruitment defects in XPB mutant cells","pmids":["17466626","17509950"],"confidence":"High","gaps":["Precise sequence of XPF recruitment events not fully ordered","How ATPase opening hands off to dual incision unresolved"]},{"year":2006,"claim":"Structural studies defined the XPB helicase architecture and damage-modulated substrate specificity, providing a framework for its DNA-opening function.","evidence":"X-ray crystallography of archaeal XPB with RED-motif mutagenesis and helicase assays; later 1.8 Å human XPB C-terminal structure with disease-mutation analysis","pmids":["16600867","23385459"],"confidence":"High","gaps":["Full-length human XPB structure within intact TFIIH not captured here","Structural transitions during catalysis not directly observed"]},{"year":2004,"claim":"Identified phosphorylation as a post-translational switch that uncouples XPB's repair and transcription roles.","evidence":"In vivo S751 phosphorylation detection, S751E/S751A mutagenesis, microinjection NER and transcription assays showing selective block of XPF 5' incision","pmids":["15549133"],"confidence":"High","gaps":["Kinase responsible for S751 not identified here","Physiological trigger for this switch unknown"]},{"year":2020,"claim":"Defined the regulatory hierarchy controlling XPB catalytic speed within TFIIH and the species-specific scanning function.","evidence":"p52/p8 crystal structure with ATPase/translocase assays and XPA stimulation; dsDNA translocase assays comparing yeast and human TFIIH; ssl2 allele TSS mapping","pmids":["33196848","33453189","34652274"],"confidence":"High","gaps":["Structural basis of p52/p8 speed-limiting not fully resolved","Why human TFIIH lacks processive scanning mechanistically unclear"]},{"year":2011,"claim":"Established XPB as a covalently druggable transcription/NER target through triptolide binding and ATPase inhibition.","evidence":"Chemical-biology covalent binding, ATPase and transcription inhibition assays","pmids":["21278739"],"confidence":"High","gaps":["Site of covalent modification not yet mapped at this stage"]},{"year":2014,"claim":"Pinpointed Cys342 as the physiologically relevant covalent target and validated XPB as the on-target effector of triptolide.","evidence":"Mass-spec identification of modified Cys342, C342T mutagenesis and CRISPR endogenous replacement conferring resistance","pmids":["25504624"],"confidence":"High","gaps":["Generality of Cys342 targeting by other ligands not yet tested at this stage"]},{"year":2019,"claim":"Revealed a regulated degradation route for XPB, defining a phospho-degron and E3 ligase axis exploited by spironolactone.","evidence":"siRNA screening, CDK7-dependent S90 phosphorylation, SCF-FBXL18 ubiquitination assays and proteasome-dependent degradation; chemoproteomic Cys342 modification by spironolactone and ZL-12A","pmids":["29036418","30762924","38569115"],"confidence":"High","gaps":["Endogenous physiological signals controlling S90 phosphorylation unknown","How distinct Cys342 ligands produce divergent degradation outcomes mechanistically unresolved"]},{"year":2020,"claim":"Showed XPB is co-opted by viruses for transcription and is targetable pharmacologically to suppress viral gene expression.","evidence":"shRNA knockdown and RNAPII ChIP for HIV-1 transcription/latency; EBV SM-XPB recruitment ChIP with siRNA and spironolactone; retroviral cDNA stability assays in XPB-mutant cells","pmids":["33239456","32434920","16537383"],"confidence":"Medium","gaps":["Direct XPB-viral protein contacts not structurally defined","Selectivity of viral promoter recruitment mechanism incompletely mapped"]},{"year":null,"claim":"How XPB catalysis is structurally choreographed within intact human TFIIH during the transition from promoter opening to escape, and how its repair-versus-transcription switching is regulated in vivo, remain to be fully defined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No high-resolution structure of catalytic intermediates in human holo-TFIIH captured in this corpus","Upstream signaling controlling S751/S90 phosphorylation undefined","Mechanistic basis of XPB roles in ATR activation and mRNA export only sketched"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[7,10,13,25,29,42]},{"term_id":"GO:0140097","term_label":"catalytic activity, acting on DNA","supporting_discovery_ids":[7,10,13,27,44]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[9,27,38]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[7,33]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[9]},{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[32]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[0,1,5,8,13,15,24,31]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[6,17,18,19,21,23,25,44,45]}],"complexes":["TFIIH"],"partners":["GTF2H4","GTF2E2","XPD","ERCC1","XPF","TP53","SUG1","RAD3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P19447","full_name":"General transcription and DNA repair factor IIH helicase/translocase subunit XPB","aliases":["Basic transcription factor 2 89 kDa subunit","BTF2 p89","DNA 3'-5' helicase/translocase XPB","DNA excision repair protein ERCC-3","DNA repair protein complementing XP-B cells","TFIIH basal transcription factor complex 89 kDa subunit","TFIIH 89 kDa subunit","TFIIH p89","Xeroderma pigmentosum group B-complementing protein"],"length_aa":782,"mass_kda":89.3,"function":"ATP-dependent 3'-5' DNA helicase/translocase (PubMed:17466626, PubMed:27193682, PubMed:33902107, PubMed:8465201, PubMed:8663148). Binds dsDNA rather than ssDNA, unzipping it in a translocase rather than classical helicase activity (PubMed:27193682, PubMed:33902107). Component of the general transcription and DNA repair factor IIH (TFIIH) core complex (PubMed:10024882, PubMed:17466626, PubMed:8157004, PubMed:8465201). When complexed to CDK-activating kinase (CAK), involved in RNA transcription by RNA polymerase II. The ATPase activity of XPB/ERCC3, but not its helicase activity, is required for DNA opening; it may wrap around the damaged DNA wedging it open, causing localized melting that allows XPD/ERCC2 helicase to anchor (PubMed:10024882, PubMed:17466626). In transcription, TFIIH has an essential role in transcription initiation (PubMed:30894545, PubMed:8157004). When the pre-initiation complex (PIC) has been established, TFIIH is required for promoter opening and promoter escape (PubMed:8157004). The ATP-dependent helicase activity of XPB/ERCC3 is required for promoter opening and promoter escape (PubMed:10024882). In transcription pre-initiation complexes induces and propagates a DNA twist to open DNA (PubMed:27193682, PubMed:33902107). Also involved in transcription-coupled nucleotide excision repair (NER) of damaged DNA (PubMed:17466626, PubMed:2111438, PubMed:8157004). In NER, TFIIH acts by opening DNA around the lesion to allow the excision of the damaged oligonucleotide and its replacement by a new DNA fragment. The structure of the TFIIH transcription complex differs from the NER-TFIIH complex; large movements by XPD/ERCC2 and XPB/ERCC3 are stabilized by XPA (PubMed:31253769, PubMed:33902107). XPA retains XPB/ERCC3 at the 5' end of a DNA bubble (mimicking DNA damage) (PubMed:31253769)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/P19447/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/ERCC3","classification":"Common Essential","n_dependent_lines":1183,"n_total_lines":1208,"dependency_fraction":0.9793046357615894},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CDC7","stoichiometry":10.0},{"gene":"CDK7","stoichiometry":10.0},{"gene":"CETN2","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/ERCC3","total_profiled":1310},"omim":[{"mim_id":"621538","title":"REQUIRED FOR EXCISION 1B DOMAIN-CONTAINING PROTEIN; REX1BD","url":"https://www.omim.org/entry/621538"},{"mim_id":"616390","title":"TRICHOTHIODYSTROPHY 2, PHOTOSENSITIVE; TTD2","url":"https://www.omim.org/entry/616390"},{"mim_id":"614777","title":"MMS19 HOMOLOG, CYTOSOLIC IRON-SULFUR ASSEMBLY COMPONENT; MMS19","url":"https://www.omim.org/entry/614777"},{"mim_id":"613644","title":"ACTIVATING TRANSCRIPTION FACTOR 7-INTERACTING PROTEIN; ATF7IP","url":"https://www.omim.org/entry/613644"},{"mim_id":"611153","title":"XPA, DNA DAMAGE RECOGNITION AND REPAIR FACTOR; XPA","url":"https://www.omim.org/entry/611153"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/ERCC3"},"hgnc":{"alias_symbol":["XPB","BTF2","RAD25","Ssl2"],"prev_symbol":[]},"alphafold":{"accession":"P19447","domains":[{"cath_id":"-","chopping":"41-163","consensus_level":"high","plddt":84.2781,"start":41,"end":163},{"cath_id":"3.40.50.300","chopping":"292-500","consensus_level":"medium","plddt":83.9083,"start":292,"end":500},{"cath_id":"3.40.50.300","chopping":"504-725","consensus_level":"high","plddt":87.7734,"start":504,"end":725}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P19447","model_url":"https://alphafold.ebi.ac.uk/files/AF-P19447-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P19447-F1-predicted_aligned_error_v6.png","plddt_mean":75.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ERCC3","jax_strain_url":"https://www.jax.org/strain/search?query=ERCC3"},"sequence":{"accession":"P19447","fasta_url":"https://rest.uniprot.org/uniprotkb/P19447.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P19447/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P19447"}},"corpus_meta":[{"pmid":"8134379","id":"PMC_8134379","title":"Hepatitis 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helicase containing seven consecutive helicase motifs conserved between two superfamilies of DNA and RNA helicases, and specifically corrects the nucleotide excision repair (NER) defect in xeroderma pigmentosum complementation group B (XP-B) rodent mutants.\",\n      \"method\": \"cDNA cloning, transfection complementation assay, sequence analysis\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cloning and direct functional complementation of NER defect; foundational paper replicated widely\",\n      \"pmids\": [\"2167179\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1990,\n      \"finding\": \"ERCC3 cDNA transfection corrects UV sensitivity and unscheduled DNA synthesis (UDS) in complementation group 3 rodent mutants, establishing its role in early steps of the nucleotide excision repair pathway.\",\n      \"method\": \"Transfection/complementation assay, UDS measurement\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct functional reconstitution of NER activity, replicated in multiple studies\",\n      \"pmids\": [\"2111438\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"SSL2 (yeast homolog of ERCC3/XPB) encodes an essential 95 kDa protein with ATP-dependent helicase motifs; an SSL2 allele mimicking the defective ERCC3 gene confers UV hypersensitivity, establishing it as the functional yeast homolog.\",\n      \"method\": \"Gene cloning, mutant allele construction, UV sensitivity assay\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic complementation and allele analysis in yeast, replicated across multiple labs\",\n      \"pmids\": [\"1318786\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"RAD25 (SSL2) is an essential gene in S. cerevisiae; a mutation in the Walker type A nucleotide-binding motif (K392R) is lethal, indicating an essential role of its ATPase/helicase activity in viability. The gene functions in excision repair (epistasis with excision repair group genes), but not in other repair pathways.\",\n      \"method\": \"Gene deletion, site-directed mutagenesis, epistasis analysis, UV sensitivity assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis and mutagenesis of essential catalytic residue, replicated\",\n      \"pmids\": [\"1333609\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"The Drosophila haywire gene encodes a protein with 66% identity to ERCC3; haywire mutants are recessive lethal or UV-sensitive, and flies with marginal haywire expression display motor defects and reduced lifespan, establishing the fly ortholog's function in NER and essential cellular processes.\",\n      \"method\": \"Genetic analysis, mutant characterization, UV sensitivity assay\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — ortholog identification with multiple alleles and phenotypic characterization\",\n      \"pmids\": [\"1458540\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"Cell-free extracts from CHO ERCC3-deficient (complementation group 3) cells are defective in in vitro DNA excision repair; complementation by mixing with group 1 extracts demonstrates that ERCC3 protein is directly required for enzymatic incision of damaged DNA or preincision reactions.\",\n      \"method\": \"Cell-free excision repair assay, in vitro complementation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution in vitro with cell extracts, direct biochemical evidence\",\n      \"pmids\": [\"1551896\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"A temperature-sensitive rad25 (SSL2) mutant shows rapid cessation of growth and large decrease in poly(A)+ RNA synthesis at the restrictive temperature, demonstrating a general and direct requirement of RAD25 (XPB ortholog) in RNA polymerase II transcription.\",\n      \"method\": \"Conditional lethal mutant, poly(A)+ RNA measurement, gene-specific Northern blot\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional lethal mutant with direct measurement of transcription defect, replicated\",\n      \"pmids\": [\"7693549\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Purified RAD25 (yeast XPB/ERCC3 ortholog) exhibits single-stranded DNA-dependent ATPase and DNA helicase activities. A thermolabile rad25 extract shows transcriptional defect correctable by adding RAD25 protein. The rad25-799am allele (repair-defective) is proficient in RNA Pol II transcription, separating DNA repair from transcription functions. The Arg-392 ATP-binding motif mutant is defective in transcription, implicating helicase activity in promoter opening.\",\n      \"method\": \"Protein purification, in vitro ATPase/helicase assay, in vitro transcription complementation, site-directed mutagenesis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — purified protein with in vitro biochemical reconstitution, mutagenesis, multiple orthogonal methods\",\n      \"pmids\": [\"8202161\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"The COOH terminus of SSL2/RAD25 is essential for overall genomic NER and transcription-coupled repair; the SSL2-XP allele (resembling the mutated ERCC3 from XP-B/CS-C patients) causes complete deficiency in cyclobutane pyrimidine dimer removal from the overall genome and transcription-coupled repair.\",\n      \"method\": \"Dimer removal assay in expressed genes and genome overall, UV sensitivity\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct measurement of NER in specific genomic contexts using well-defined allele\",\n      \"pmids\": [\"8294433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Mutations in the ATPase motif (helicase domain I), other helicase domains, and the potential helix-turn-helix DNA-binding motif of ERCC3 abolish NER complementation activity; C-terminal deletions implicate a distinct determinant for DNA repair. A functional epitope-tagged ERCC3 accumulates in the nucleus, and deletion of the putative NLS does not impair nuclear localization.\",\n      \"method\": \"Site-directed mutagenesis, deletion mutagenesis, UV complementation assay, immunofluorescence\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic mutagenesis with multiple constructs and functional readout\",\n      \"pmids\": [\"8196650\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Recombinant XPB/ERCC3 protein produced in baculovirus system exhibits DNA helicase activity, directly demonstrating that XPB itself is a DNA helicase.\",\n      \"method\": \"Baculovirus expression, protein purification, in vitro helicase assay\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro helicase reconstitution with purified recombinant protein\",\n      \"pmids\": [\"7937133\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Yeast RAD3 protein directly binds to SSL2 (RAD25/XPB) protein in vitro via an N-terminal, potentially non-catalytic domain of SSL2. A DNA repair-defective allele of SSL2 is not defective in binding to transcription factor b (TFIIH), genetically separating the repair and transcription-binding functions.\",\n      \"method\": \"In vitro immunoprecipitation, yeast two-hybrid, genetic analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal in vitro binding with genetic separation of function\",\n      \"pmids\": [\"8171014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"HBX (hepatitis B virus X protein) complexes with wild-type p53 and inhibits the in vitro association of p53 with ERCC3, as well as p53-mediated transcriptional activation, revealing ERCC3 as a p53-interacting transcription factor.\",\n      \"method\": \"In vitro protein-protein interaction assay, transcription assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single-lab in vitro binding assay; indirect (HBX inhibits p53-ERCC3 interaction)\",\n      \"pmids\": [\"8134379\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"TFIIH isolated from XP-B patient cells (XP11BE) carrying a frameshift mutation in XPB shows reduced 3'→5' XPB helicase activity and DNA-dependent ATPase activity, and causes a severe NER defect and decreased basal transcription activity in vitro, establishing that XPB's helicase activity is required for both NER and transcription.\",\n      \"method\": \"Immunopurification of TFIIH, helicase/ATPase assays, in vitro transcription, NER assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — purified patient-derived TFIIH with multiple biochemical assays demonstrating mechanistic link\",\n      \"pmids\": [\"8663148\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"XPB and XPD are components of the p53-dependent apoptosis pathway: primary fibroblasts from XP-B or XP-D patients (but not XP-A or XP-C) are deficient in p53-mediated apoptosis; this deficiency is rescued by transfer of the wild-type XPB or XPD gene, and the carboxy-terminus of p53 is required for apoptosis.\",\n      \"method\": \"Microinjection of expression vectors, retroviral infection, complementation assay, apoptosis measurement\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic complementation with specific rescue, multiple cell types tested\",\n      \"pmids\": [\"8675009\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Reconstituted yeast TFIIH requires both Rad3 and Rad25 (XPB ortholog) helicase subunits for in vitro NER-mediated incision of UV-damaged DNA; the Rad25 Arg-392 (ATP-binding motif) mutant abolishes NER but not CTD kinase activity, which is dispensable for incision.\",\n      \"method\": \"TFIIH reconstitution, in vitro NER incision assay, mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted in vitro NER system with purified proteins and mutagenesis\",\n      \"pmids\": [\"8631896\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"XPB directly interacts with SUG1 (a subunit of the 26S proteasome), validated by yeast two-hybrid, baculovirus co-expression, co-purification with TFIIH holocomplex, and co-immunoprecipitation; overexpression of SUG1 arrests transcription; a mutant XPB (XP-B patient mutation) shows diminished interaction with SUG1.\",\n      \"method\": \"Yeast two-hybrid, baculovirus co-expression, co-purification, co-immunoprecipitation\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods confirming interaction, including functional consequence of overexpression\",\n      \"pmids\": [\"9173976\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Reconstituted baculovirus-expressed TFIIH with mutated XPB (helicase-dead) is unable to initiate transcription; XPB helicase is absolutely required for promoter opening at the transcription start site, whereas XPD helicase is dispensable but stimulates transcription and anchors CAK to TFIIH.\",\n      \"method\": \"TFIIH reconstitution from recombinant subunits, in vitro transcription, mutagenesis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — full reconstitution of TFIIH from recombinant proteins with mutagenesis and functional assay\",\n      \"pmids\": [\"10024882\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Mutations in XPB found in XP-B/CS patients decrease the transcriptional activity of immunopurified TFIIH by preventing promoter opening; this defect can be circumvented by artificial opening of the promoter, demonstrating that XPB is specifically required for the promoter-opening step in transcription.\",\n      \"method\": \"Immunopurification of patient TFIIH, in vitro transcription, promoter opening assay\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — purified patient TFIIH with multiple biochemical assays and functional rescue\",\n      \"pmids\": [\"10064601\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"XPB helicase activity of TFIIH is primarily responsible for preventing premature arrest of early elongation intermediates during RNA polymerase II promoter escape, demonstrated with TFIIH mutants in a reconstituted minimal transcription system.\",\n      \"method\": \"Reconstituted in vitro transcription system, TFIIH mutant analysis, promoter escape assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted system with purified factors and defined mutants\",\n      \"pmids\": [\"10428772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The p52 subunit of TFIIH physically interacts with XPB and is required to anchor XPB within TFIIH; deletion of the C-terminal region of p52 prevents promoter opening and abolishes NER and transcription activities, demonstrating p52 regulates XPB function through direct interaction.\",\n      \"method\": \"Reconstituted in vitro transcription/NER, deletion mutagenesis, co-immunoprecipitation, domain mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted in vitro system with mutagenesis and multiple functional assays\",\n      \"pmids\": [\"12080057\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The ERCC3 helicase activity of TFIIH plays a regulatory role in stimulating promoter escape during transcriptional activation; the helicase acts throughout the promoter-escape phase (up to ~10-nt RNA synthesis) to increase the proportion of productive complexes that escape the promoter.\",\n      \"method\": \"Reconstituted in vitro transcription, TFIIH helicase mutants, transcription elongation analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted transcription system with defined TFIIH mutants\",\n      \"pmids\": [\"11818577\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"HCV NS5A protein inhibits the p53-ERCC3 protein-protein complex formation in vitro, as shown by co-immunoprecipitation and pull-down assays.\",\n      \"method\": \"Co-immunoprecipitation, pull-down assay\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single-lab co-IP/pulldown, indirect disruption of p53-ERCC3 complex\",\n      \"pmids\": [\"12379483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The ERCC3 helicase activity of TFIIH alleviates PC4-mediated transcriptional repression via beta-gamma bond hydrolysis of ATP; this requires ERCC3 helicase but not ERCC2 helicase or CDK7 kinase activity, suggesting ERCC3 relieves topological constraints imposed by PC4 at promoters.\",\n      \"method\": \"Reconstituted in vitro transcription, recombinant TFIIH with defined enzymatic mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted in vitro system with specific enzymatic mutants discriminating ERCC3 from other TFIIH activities\",\n      \"pmids\": [\"12590132\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Serine 751 (S751) of XPB is phosphorylated in vivo; this phosphorylation inhibits NER (a phosphomimicking S751E mutant cannot correct NER defect in XP-B cells) without affecting TFIIH-dependent transcription. S751 phosphorylation does not impair DNA unwinding by TFIIH but prevents 5' incision by ERCC1-XPF endonuclease.\",\n      \"method\": \"In vivo phosphorylation detection, microinjection, NER and transcription assays, mutagenesis (S751E, S751A)\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — identification of phosphorylation site, mutagenesis, in vivo and in vitro functional assays with defined mechanism\",\n      \"pmids\": [\"15549133\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"XPB ATPase activity (not helicase activity per se) drives promoter opening for RNA Pol II transcription; XPB helicase mutants that retain ATPase activity are proficient for promoter opening but defective in promoter escape, paralleling sigma54 bacterial transcription.\",\n      \"method\": \"XPB helicase mutant characterization, in vitro transcription assay\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — specific mutants separating ATPase from helicase activity, functional assays\",\n      \"pmids\": [\"15937491\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The beta subunit of TFIIE directly stimulates XPB helicase and ATPase activities; TFIIE beta mutants defective for XPB helicase stimulation but competent for PIC assembly are defective in in vitro transcription, establishing TFIIE beta as a co-factor that enhances XPB activity during transcription initiation and promoter escape.\",\n      \"method\": \"In vitro helicase/ATPase assay, mutagenesis of TFIIE beta, reconstituted transcription\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro assay with mutagenesis and functional consequence in transcription\",\n      \"pmids\": [\"15917439\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Crystal structures of an archaeal XPB homolog reveal two RecA-like helicase domains, a DNA damage recognition domain (DRD), a unique RED motif, and a flexible thumb motif (ThM). RED motif mutations dramatically reduce helicase activity; the substrate specificity is altered by DNA damage (AfXPB unwinds dsDNA with 3' extensions but not blunt-ended dsDNA unless it contains a lesion).\",\n      \"method\": \"X-ray crystallography, site-directed mutagenesis, in vitro helicase assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional validation by mutagenesis and helicase assay\",\n      \"pmids\": [\"16600867\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"XPB DNA repair-deficient cells (XPB/XPD mutants but not XPA mutants) show increased HIV and MLV retroviral transduction efficiency and greater retroviral cDNA stability, establishing a role for TFIIH XPB in degradation of retroviral cDNA as a cellular defense.\",\n      \"method\": \"Retroviral transduction assay, quantitative PCR, XPB mutant cell lines\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined mutant cell lines with multiple viral systems, single lab\",\n      \"pmids\": [\"16537383\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The p52 subunit of TFIIH interacts with XPB and stimulates its ATPase activity; the XP-B patient mutation F99S weakens this interaction and the resulting ATPase stimulation, explaining the damaged DNA opening defect. Mutations in helicase motifs III (T469A) and VI (Q638A) that inhibit XPB helicase activity preserve NER function, demonstrating that XPB ATPase (not helicase) activity drives damaged DNA opening in NER.\",\n      \"method\": \"Protein-protein interaction assay, ATPase assay, mutagenesis, in vitro NER reconstitution\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with mutagenesis and ATPase/helicase dissection\",\n      \"pmids\": [\"17466626\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Archaeal XPB (from S. solfataricus) is a ssDNA-stimulated ATPase without helicase activity in vitro; XPB physically interacts with a conserved archaeal partner protein Bax1 (encoded by the adjacent gene), establishing a novel XPB-associated endonuclease complex in archaea.\",\n      \"method\": \"ATPase assay, helicase assay, in vitro co-purification/interaction assay\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct in vitro biochemical characterization, single lab\",\n      \"pmids\": [\"18177890\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"XPB regulates the recruitment and redistribution of NER proteins at UV damage sites; delayed or absent XPF recruitment is a hallmark of XPB mutations, and redistribution of NER proteins after repair is dependent on functional XPB.\",\n      \"method\": \"Local UV irradiation through micropore filters, fluorescent antibody labeling, live-cell imaging\",\n      \"journal\": \"DNA repair\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with defined mutant cell lines and functional consequence\",\n      \"pmids\": [\"17509950\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"XPB (p89), but not other TFIIH subunits, re-localizes to centrosomes and adjacent parts of the mitotic spindle during cell division (prophase through telophase); XPB interacts with the centrosomal protein gamma-tubulin; C-terminal truncations of XPB abolish centrosomal association.\",\n      \"method\": \"Immunofluorescence, GFP-fusion live imaging, co-immunoprecipitation, deletion constructs\",\n      \"journal\": \"Cellular oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization by live imaging and co-IP with functional consequence of truncations; single lab\",\n      \"pmids\": [\"20208140\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Triptolide covalently binds to human XPB (ERCC3), a subunit of TFIIH, and inhibits its DNA-dependent ATPase activity, leading to inhibition of RNA polymerase II-mediated transcription and NER.\",\n      \"method\": \"Chemical biology binding assay, ATPase inhibition assay, transcription inhibition assay\",\n      \"journal\": \"Nature chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — covalent modification identified, ATPase inhibition demonstrated with mechanistic follow-up\",\n      \"pmids\": [\"21278739\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"XPB functions in ATR kinase activation in non-replicating cells exposed to bulky DNA adducts: genetic and pharmacological inhibition of XPB prevents RPA accumulation on damaged chromatin and abrogates ATR signaling in response to NA-AAF and camptothecin, revealing a role for TFIIH in ATR activation independent of XPA.\",\n      \"method\": \"siRNA knockdown, pharmacological XPB inhibition, immunoblot for ATR substrates, RPA chromatin fractionation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic and pharmacological inhibition with mechanistic readout; single lab\",\n      \"pmids\": [\"28592488\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Tfb6, a newly identified TFIIH subunit, forms a heterodimer with Ssl2 (XPB) and facilitates dissociation of Ssl2 from TFIIH after transcription initiation, but does not dissociate Ssl2 from the fully assembled transcription preinitiation complex.\",\n      \"method\": \"TFIIH subunit identification, co-purification, in vitro dissociation assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct biochemical characterization of new binding partner and functional consequence\",\n      \"pmids\": [\"22411836\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Crystal structure of the C-terminal half of human XPB (residues 494-782) at 1.8 Å resolution reveals HD2 and a C-terminal extension with structural similarity to RIG-I; this supports a structural model for XPF-XPB-DNA complex for 5' incision. The XP11BE patient mutation reduces XPB solubility and lowers intracellular TFIIH levels, impairing both DNA repair and transcription.\",\n      \"method\": \"X-ray crystallography, Western blot, mutant protein analysis\",\n      \"journal\": \"Acta crystallographica. Section D, Biological crystallography\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional validation of disease mutation\",\n      \"pmids\": [\"23385459\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Triptolide covalently modifies Cys342 of XPB via its 12,13-epoxide group; mutation of Cys342 to threonine (C342T) confers resistance to triptolide and replacement of endogenous wild-type XPB with C342T in HEK293T cells renders them completely resistant to triptolide, validating XPB as the physiologically relevant target.\",\n      \"method\": \"Mass spectrometry identification of modified residue, site-directed mutagenesis, CRISPR/Cas9 endogenous replacement, cell viability assay\",\n      \"journal\": \"Angewandte Chemie (International ed. in English)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — precise residue identification, mutagenesis, endogenous gene replacement with functional rescue\",\n      \"pmids\": [\"25504624\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"XPB and XPD bind to G-quadruplex (G4) DNA genome-wide; XPB binds G4 DNA while XPD is a robust G4 helicase; 40% of XPB/XPD ChIP-Seq binding sites overlap with G4 motifs, particularly near transcription start sites of highly transcribed genes.\",\n      \"method\": \"ChIP-Seq in human cells, biochemical G4 binding/helicase assay\",\n      \"journal\": \"Nature chemical biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP-Seq with biochemical validation, single lab\",\n      \"pmids\": [\"24609361\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Spironolactone (SPL) promotes proteasome-dependent degradation of XPB (but not via mineralocorticoid receptor); proteasome blockade or XPB overexpression prevents SPL-mediated suppression of NF-κB and AP-1 inflammatory signalling; XP patient fibroblasts with N-terminal (but not C-terminal) XPB mutations are insensitive to SPL-mediated XPB degradation.\",\n      \"method\": \"Proteasome inhibitor, siRNA knockdown, XPB overexpression, chromatin immunoprecipitation, patient-derived fibroblasts\",\n      \"journal\": \"Cardiovascular research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal approaches with mechanistic follow-up; single lab\",\n      \"pmids\": [\"29036418\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Spironolactone-induced XPB degradation requires CDK7 kinase activity and SCFFBXL18 E3 ubiquitin ligase (comprising Skp1, Cul1, FBXL18, and Rbx1); CDK7 phosphorylates XPB at Ser90 to trigger recognition by SCFFBXL18 for polyubiquitination and proteasomal degradation.\",\n      \"method\": \"siRNA library screening, ubiquitination assay, co-immunoprecipitation, site-directed mutagenesis (S90)\",\n      \"journal\": \"Genes to cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional siRNA screen with biochemical validation of key components; single lab\",\n      \"pmids\": [\"30762924\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Spironolactone rapidly inhibits HIV-1 transcription by degrading XPB, reducing RNA polymerase II recruitment to the HIV-1 genome; shRNA knockdown of XPB confirmed that XPB degradation is the mechanism of action. SP also inhibits HIV reactivation from latency in resting CD4+ T cells.\",\n      \"method\": \"shRNA knockdown, RNAPII ChIP, HIV transcription assay, latency reactivation assay\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — shRNA confirmation and ChIP-based mechanistic readout; single lab\",\n      \"pmids\": [\"33239456\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"p52/p8 subunits of TFIIH act as master regulators of XPB ATPase activity: XPB ATPase can be activated by DNA or p52/p8, but when both are present p52/p8 dominates and acts as a speed limiter. XPB translocase activity (within core TFIIH) is enhanced by XPA, which increases processivity without altering ATPase rate.\",\n      \"method\": \"ATPase assay, translocase assay, crystal structure of p52/p8, functional mutagenesis, cryo-EM-guided analysis\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional mutagenesis and multiple enzymatic assays\",\n      \"pmids\": [\"33196848\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"EBV SM protein recruits XPB to EBV lytic promoters during lytic replication; depletion of XPB by spironolactone or siRNA inhibits SM-dependent late lytic gene transcription but not other EBV or cellular gene transcription, demonstrating XPB is specifically co-opted for EBV SM-mediated transcriptional activation.\",\n      \"method\": \"ChIP, siRNA knockdown, spironolactone treatment, gene-specific transcription assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and siRNA with functional transcription readout; single lab\",\n      \"pmids\": [\"32434920\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"The XPB/Ssl2 dsDNA translocase activity drives transcription start-site (TSS) scanning in S. cerevisiae; processive translocation by holo-TFIIH requires the TFIIH kinase module as a processivity factor. Human TFIIH (holo and core) does not exhibit processive translocation, consistent with absence of TSS scanning in humans.\",\n      \"method\": \"dsDNA translocase assay, ATPase assay, holo- vs. core-TFIIH comparison across species\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct biochemical assay with human and yeast complexes, mechanistic dissection\",\n      \"pmids\": [\"33453189\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Ssl2 (XPB) ATPase activity drives TSS scanning processivity in S. cerevisiae; distinct ssl2 alleles cause upstream or downstream TSS shifts genome-wide; genetic interactions with other initiation factors are consistent with Ssl2 modulating scanning processivity through a conserved residue interaction network.\",\n      \"method\": \"Isolation of novel ssl2 alleles, TSS mapping (PRO-Seq equivalent), genetic interaction analysis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple alleles, genome-wide TSS mapping, genetic epistasis\",\n      \"pmids\": [\"34652274\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"A spirocycle acrylamide compound (ZL-12A) covalently reacts with Cys342 of ERCC3 (same residue as triptolide) and promotes ERCC3 degradation as a monofunctional degrader; spironolactone also reacts with ERCC3_C342. ZL-12A and triptolide cross-antagonize each other's protein degradation profiles, demonstrating that covalent ligands targeting the same cysteine can produce distinct functional outcomes.\",\n      \"method\": \"Activity-based protein profiling (ABPP), cysteine-directed chemoproteomics, protein degradation assay, cross-antagonism experiment\",\n      \"journal\": \"Journal of the American Chemical Society\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — site-specific covalent modification identified, functional degradation validated, cross-antagonism experiment\",\n      \"pmids\": [\"38569115\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"XPB participates in mRNA export in fission yeast (Ptr8p/XPB); a ptr8-1 temperature-sensitive mutant accumulates poly(A)+ RNA in the nucleus; human XPB rescues both UV sensitivity and mRNA export defects; functional interaction between Ptr8p and Tho2p (TREX complex) was demonstrated.\",\n      \"method\": \"Conditional mutant, poly(A)+ RNA localization, cross-species complementation, co-immunoprecipitation\",\n      \"journal\": \"Genes to cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization and functional complementation in yeast; single lab\",\n      \"pmids\": [\"17212653\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Ssl2 (XPB yeast ortholog) interacts with Hsp90 chaperone machinery; multiple SSL2 mutant alleles exhibit pronounced growth defects when co-expressed with mutant Hsp90; Ssl2 protein co-purifies with Hsp90 and Sti1, suggesting Ssl2 function depends on Hsp90.\",\n      \"method\": \"Genetic screen, co-purification, co-immunoprecipitation\",\n      \"journal\": \"Current genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single-lab co-purification with functional consequence only in genetic sensitized background\",\n      \"pmids\": [\"15871019\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Ssl2 (XPB) and TFIIB functionally interact in start-site selection and gene looping: an ssl2 suppressor allele (H508R) suppresses the cold-sensitive growth defect and TSS selection defect of the sua7-1 (TFIIB E62K) mutation; Ssl2 associates with both promoter and terminator regions.\",\n      \"method\": \"Genetic suppressor screen, start-site mapping, ChIP\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with ChIP evidence; single lab\",\n      \"pmids\": [\"22081613\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ERCC3/XPB is a 3'→5' DNA helicase and ATPase that functions as an essential core subunit of the general transcription factor TFIIH: its ATPase activity (not helicase per se) drives promoter DNA opening during RNA polymerase II transcription initiation and damaged-DNA opening during nucleotide excision repair (NER), while its helicase activity facilitates promoter escape and TSS scanning; within TFIIH, its activity is stimulated and speed-limited by the p52/p8 subcomplex and co-activated by TFIIE-β, it is phosphorylated on S751 (selectively inhibiting NER incision) and S90 (triggering SCFFBXL18-mediated proteasomal degradation), it interacts with SUG1/26S proteasome and Hsp90 chaperone machinery, and its Cys342 is the site of covalent modification by triptolide and spironolactone-related compounds that inhibit or degrade XPB to suppress transcription and NER.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ERCC3/XPB is an essential 3'→5' DNA helicase and DNA-dependent ATPase that operates as a core catalytic subunit of the general transcription factor TFIIH, coupling RNA polymerase II transcription to nucleotide excision repair (NER) [#0, #2, #6, #13]. It was identified by functional complementation of the NER defect in xeroderma pigmentosum group B and rodent group-3 mutants [#0, #1, #5], and its yeast ortholog SSL2/RAD25 established the gene as essential, with a lethal Walker-A (K392R) ATPase mutation [#3] and a conditional allele that simultaneously arrests growth and poly(A)+ RNA synthesis, demonstrating a direct and general role in Pol II transcription [#6]. Biochemical reconstitution from purified and recombinant subunits showed XPB to be a bona fide DNA helicase [#7, #10] whose activities are partitioned functionally: the ATPase activity—not helicase translocation per se—drives promoter opening at the transcription start site and damaged-DNA opening during NER, whereas the helicase/translocase activity governs promoter escape, prevents premature arrest of early elongation intermediates, and relieves topological constraints imposed by repressors such as PC4 [#17, #18, #19, #21, #23, #25, #29]. In yeast, this same ATPase/translocase drives processive transcription start-site scanning, a function absent from human TFIIH [#44, #45]. Within TFIIH, XPB is anchored and its catalytic output regulated by the p52/p8 subcomplex, which stimulates and acts as a dominant speed-limiter of its ATPase, while TFIIE-β co-activates its helicase/ATPase and XPA enhances translocase processivity [#20, #26, #29, #42]. XPB function in NER requires its C-terminus and coordinates the recruitment and redistribution of downstream NER factors, including ERCC1-XPF for 5' incision [#8, #9, #31, #36]; phosphorylation of Ser751 selectively blocks NER incision without impairing transcription, separating its two roles post-translationally [#24]. Structural studies of archaeal and human XPB define tandem RecA-like helicase domains, a DNA damage recognition domain, and the catalytic RED motif, and rationalize disease alleles that reduce XPB solubility and TFIIH levels [#27, #36]. Patient-derived XPB mutations underlie the combined NER/transcription deficiencies of xeroderma pigmentosum group B and XP-B/Cockayne syndrome [#13, #18, #36]. XPB Cys342 is the covalent attachment site for triptolide and spironolactone-related compounds that inhibit its ATPase or trigger its degradation, shutting down transcription and NER and providing a chemically validated drug target [#33, #37, #46].\",\n  \"teleology\": [\n    {\n      \"year\": 1990,\n      \"claim\": \"Established the molecular identity of ERCC3 as a candidate DNA helicase and its causal role in a defined repair defect, framing all subsequent mechanistic work.\",\n      \"evidence\": \"cDNA cloning and transfection complementation of the NER/UDS defect in XP-B and rodent group-3 mutants\",\n      \"pmids\": [\"2167179\", \"2111438\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Helicase activity was predicted from sequence motifs, not yet biochemically demonstrated\", \"Role in transcription not yet known\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"Cross-species genetics (yeast SSL2/RAD25, Drosophila haywire) established ERCC3 as an essential gene whose catalytic ATPase/helicase function is required for viability, not merely repair.\",\n      \"evidence\": \"Gene deletion, Walker-A K392R lethality, allele analysis, epistasis, and ortholog phenotyping in yeast and flies; in vitro excision-repair complementation in CHO extracts\",\n      \"pmids\": [\"1318786\", \"1333609\", \"1458540\", \"1551896\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic basis of essentiality unresolved\", \"Whether essentiality reflects transcription versus repair not yet separated\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Resolved why the gene is essential beyond repair by showing a direct, general requirement in RNA polymerase II transcription.\",\n      \"evidence\": \"Temperature-sensitive rad25 mutant with collapse of poly(A)+ RNA synthesis at restrictive temperature\",\n      \"pmids\": [\"7693549\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The specific transcriptional step requiring XPB not yet defined\", \"Biochemical activity underlying transcription role unproven\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Demonstrated XPB is itself an ATP-dependent DNA helicase and genetically separated its repair and transcription functions, anchoring its role within TFIIH.\",\n      \"evidence\": \"Purified/recombinant RAD25 and baculovirus XPB helicase and ssDNA-dependent ATPase assays; repair-defective vs transcription-defective alleles; RAD3-SSL2 in vitro binding; systematic mutagenesis with NER readout\",\n      \"pmids\": [\"8202161\", \"7937133\", \"8294433\", \"8196650\", \"8171014\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether ATPase or helicase activity drives each substep not yet resolved\", \"Regulation of XPB within TFIIH undefined\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Patient-derived TFIIH analysis linked XPB helicase/ATPase loss directly to combined NER and basal transcription defects, and reconstituted yeast TFIIH confirmed XPB is required for incision.\",\n      \"evidence\": \"Immunopurified XP-B TFIIH with helicase/ATPase, transcription and NER assays; reconstituted yeast TFIIH NER incision with Rad25 ATP-motif mutant\",\n      \"pmids\": [\"8663148\", \"8631896\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"CTD kinase activity shown dispensable for incision but its broader role unclear\", \"Exact catalytic step of XPB in incision not yet pinned\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Defined XPB helicase as absolutely required for promoter opening and for preventing arrest during promoter escape in fully reconstituted transcription systems.\",\n      \"evidence\": \"TFIIH reconstituted from recombinant subunits with helicase-dead XPB; patient TFIIH promoter-opening assays with artificial-bubble rescue; minimal reconstituted promoter-escape assays\",\n      \"pmids\": [\"10024882\", \"10064601\", \"10428772\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether ATP hydrolysis or strand translocation per se opens the promoter not yet distinguished\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Dissected the catalytic logic of XPB: ATPase activity drives promoter opening while helicase translocation drives promoter escape, with TFIIE-β as a co-activator.\",\n      \"evidence\": \"XPB helicase mutants retaining ATPase activity in in vitro transcription; TFIIE-β mutagenesis and helicase/ATPase stimulation assays\",\n      \"pmids\": [\"15937491\", \"15917439\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of ATPase-driven opening not yet visualized\", \"How TFIIE-β engages XPB structurally undefined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Extended the ATPase-versus-helicase distinction to NER, showing p52-stimulated XPB ATPase, not helicase, opens damaged DNA, and explained an XP-B patient mutation mechanistically.\",\n      \"evidence\": \"p52-XPB interaction and ATPase stimulation assays; F99S, T469A, Q638A mutants in reconstituted NER; localization of NER-factor recruitment defects in XPB mutant cells\",\n      \"pmids\": [\"17466626\", \"17509950\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise sequence of XPF recruitment events not fully ordered\", \"How ATPase opening hands off to dual incision unresolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Structural studies defined the XPB helicase architecture and damage-modulated substrate specificity, providing a framework for its DNA-opening function.\",\n      \"evidence\": \"X-ray crystallography of archaeal XPB with RED-motif mutagenesis and helicase assays; later 1.8 Å human XPB C-terminal structure with disease-mutation analysis\",\n      \"pmids\": [\"16600867\", \"23385459\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length human XPB structure within intact TFIIH not captured here\", \"Structural transitions during catalysis not directly observed\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identified phosphorylation as a post-translational switch that uncouples XPB's repair and transcription roles.\",\n      \"evidence\": \"In vivo S751 phosphorylation detection, S751E/S751A mutagenesis, microinjection NER and transcription assays showing selective block of XPF 5' incision\",\n      \"pmids\": [\"15549133\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase responsible for S751 not identified here\", \"Physiological trigger for this switch unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined the regulatory hierarchy controlling XPB catalytic speed within TFIIH and the species-specific scanning function.\",\n      \"evidence\": \"p52/p8 crystal structure with ATPase/translocase assays and XPA stimulation; dsDNA translocase assays comparing yeast and human TFIIH; ssl2 allele TSS mapping\",\n      \"pmids\": [\"33196848\", \"33453189\", \"34652274\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of p52/p8 speed-limiting not fully resolved\", \"Why human TFIIH lacks processive scanning mechanistically unclear\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Established XPB as a covalently druggable transcription/NER target through triptolide binding and ATPase inhibition.\",\n      \"evidence\": \"Chemical-biology covalent binding, ATPase and transcription inhibition assays\",\n      \"pmids\": [\"21278739\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Site of covalent modification not yet mapped at this stage\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Pinpointed Cys342 as the physiologically relevant covalent target and validated XPB as the on-target effector of triptolide.\",\n      \"evidence\": \"Mass-spec identification of modified Cys342, C342T mutagenesis and CRISPR endogenous replacement conferring resistance\",\n      \"pmids\": [\"25504624\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Generality of Cys342 targeting by other ligands not yet tested at this stage\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Revealed a regulated degradation route for XPB, defining a phospho-degron and E3 ligase axis exploited by spironolactone.\",\n      \"evidence\": \"siRNA screening, CDK7-dependent S90 phosphorylation, SCF-FBXL18 ubiquitination assays and proteasome-dependent degradation; chemoproteomic Cys342 modification by spironolactone and ZL-12A\",\n      \"pmids\": [\"29036418\", \"30762924\", \"38569115\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous physiological signals controlling S90 phosphorylation unknown\", \"How distinct Cys342 ligands produce divergent degradation outcomes mechanistically unresolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Showed XPB is co-opted by viruses for transcription and is targetable pharmacologically to suppress viral gene expression.\",\n      \"evidence\": \"shRNA knockdown and RNAPII ChIP for HIV-1 transcription/latency; EBV SM-XPB recruitment ChIP with siRNA and spironolactone; retroviral cDNA stability assays in XPB-mutant cells\",\n      \"pmids\": [\"33239456\", \"32434920\", \"16537383\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct XPB-viral protein contacts not structurally defined\", \"Selectivity of viral promoter recruitment mechanism incompletely mapped\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How XPB catalysis is structurally choreographed within intact human TFIIH during the transition from promoter opening to escape, and how its repair-versus-transcription switching is regulated in vivo, remain to be fully defined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No high-resolution structure of catalytic intermediates in human holo-TFIIH captured in this corpus\", \"Upstream signaling controlling S751/S90 phosphorylation undefined\", \"Mechanistic basis of XPB roles in ATR activation and mRNA export only sketched\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [7, 10, 13, 25, 29, 42]},\n      {\"term_id\": \"GO:0140097\", \"supporting_discovery_ids\": [7, 10, 13, 27, 44]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [9, 27, 38]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [7, 33]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [9]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [32]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [0, 1, 5, 8, 13, 15, 24, 31]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [6, 17, 18, 19, 21, 23, 25, 44, 45]}\n    ],\n    \"complexes\": [\"TFIIH\"],\n    \"partners\": [\"GTF2H4\", \"GTF2E2\", \"XPD\", \"ERCC1\", \"XPF\", \"TP53\", \"SUG1\", \"RAD3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":9,"faith_total":9,"faith_pct":100.0}}