{"gene":"POLR2A","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":2018,"finding":"Live-cell FRAP with GFP-RPB1 knockin cells and computational modeling revealed four kinetically distinct Pol II fractions: ~7% freely diffusing, ~10% chromatin-bound for ~2.4 seconds during initiation, ~23% promoter-paused for ~42 seconds (with high turnover likely due to premature termination), and ~23% elongating on chromatin for ~23 minutes.","method":"GFP-RPB1 knockin (endogenous tagging), FRAP/photobleaching, computational modeling","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — endogenous GFP knockin with quantitative live-cell imaging and rigorous computational modeling; multiple kinetic parameters established in a single well-controlled study","pmids":["29632207"],"is_preprint":false},{"year":2009,"finding":"The CTD of Rpb1 (yeast) is phosphorylated at Ser7 in vivo; the basal factor TFIIH (Kin28/Cdk7) can phosphorylate Ser7 in vitro and is necessary for Ser7 phosphorylation in vivo. Deletion of the Ser5-phosphatase Rtr1 increases Ser5-P but not Ser7-P, distinguishing the two marks.","method":"Chromatin immunoprecipitation (ChIP), in vitro kinase assay, genetic deletion of Rtr1","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro kinase assay combined with in vivo ChIP and genetic epistasis, two orthogonal methods in one study","pmids":["19679665"],"is_preprint":false},{"year":2016,"finding":"Mass-spectrometry analysis of a modified CTD (msCTD) showed that Ser5-P and Ser2-P are far more abundant than other CTD phosphorylations; msCTD co-purifying with capping enzyme was enriched for Ser5-P, while that bound to termination factor Rtt103 had higher Ser2-P, supporting a sparse 'CTD code'.","method":"Modified CTD mass spectrometry (msCTD), affinity purification, CTD kinase/phosphatase mutants","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Moderate — quantitative MS with engineered CTD, validated by kinase/phosphatase mutant strains and co-purification with known CTD-binding factors","pmids":["26799764"],"is_preprint":false},{"year":2005,"finding":"NMR solution structure of the human Set2 SRI domain revealed a three-helix bundle; NMR titration and Biacore binding assays showed the SRI domain binds preferentially to doubly (Ser2+Ser5)-phosphorylated CTD peptides of Rpb1 via helices 1 and 2, with five residues identified as critical by point mutagenesis.","method":"NMR structure determination, NMR titration, Biacore surface plasmon resonance, point mutagenesis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR structure plus orthogonal binding assay (SPR) plus mutagenesis in a single study, rigorous controls","pmids":["16314571"],"is_preprint":false},{"year":2008,"finding":"The mammalian Elongin A–Elongin BC–Cul5/Rbx2 hetero-pentamer complex ubiquitylates Rpb1 in vitro; Elongin A-deficient cells show suppressed UV-induced Rpb1 ubiquitylation and proteasomal degradation. Elongin A preferentially interacts with Ser5-phosphorylated Rpb1 after UV irradiation.","method":"In vitro ubiquitylation assay (reconstituted complex), Elongin A knockdown/rescue, Co-IP (Elongin A with Rpb1)","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — reconstituted in vitro ubiquitylation plus cellular KD/rescue with two orthogonal readouts (ubiquitylation and degradation)","pmids":["19037258"],"is_preprint":false},{"year":2007,"finding":"Yeast Rpb9 (nonessential Pol II subunit) promotes UV-induced ubiquitylation and degradation of Rpb1 via its C-terminal Zn2 domain; the Zn2 domain is dispensable for transcription elongation and TCR but essential for Rpb1 degradation. Co-IP showed nearly full-length Rpb9 is needed for strong interaction with core Pol II.","method":"UV irradiation, domain-deletion mutants of Rpb9, Co-immunoprecipitation, 26S proteasome inhibitor experiments","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — domain-mapping with multiple deletion constructs, Co-IP, and proteasome inhibitor assay in a single study","pmids":["17452455"],"is_preprint":false},{"year":2012,"finding":"Old World alphavirus nsP2 proteins (Sindbis, Semliki Forest, Chikungunya) induce rapid ubiquitination and proteasomal degradation of Rpb1 to inhibit host transcription; this is independent of nsP2 protease activity but requires integrity of nsP2 helicase and SAM-dependent methyltransferase-like domains.","method":"Viral infection, nsP2 point mutants, proteasome inhibitor, ubiquitination assay, Western blot for Rpb1 levels","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — domain-disrupting point mutations in viral protein plus proteasome inhibitor and ubiquitination assay, multi-virus validation","pmids":["22514352"],"is_preprint":false},{"year":2022,"finding":"ARMC5, CUL3, and RBX1 form an active E3 ubiquitin ligase complex specific for RPB1; Armc5 deletion reduces RPB1 ubiquitination and increases RPB1 accumulation. Mutant ARMC5 (as found in PBMAH patients) shows altered binding to RPB1.","method":"Co-immunoprecipitation (ARMC5-CUL3-RBX1 complex), in vitro E3 ligase assay, Armc5 knockout mouse, RPB1 ubiquitination Western blot","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro E3 ligase assay with reconstituted complex plus knockout mouse model and patient mutation analysis","pmids":["35687106"],"is_preprint":false},{"year":2009,"finding":"Rpb1 is sumoylated in yeast upon UV radiation or transcriptional impairment; E2 conjugase Ubc9 and E3 ligase Siz1 mediate this modification; K1487 in the acidic linker region of Rpb1 is the major sumoylation site. Rpb1 sumoylation restrains the DNA damage checkpoint (Rad53 phosphorylation) caused by transcription-blocking lesions.","method":"UV irradiation, SUMO pathway mutants (Ubc9, Siz1), site-directed mutagenesis (K1487), checkpoint kinase Rad53 phosphorylation assay","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — site-directed mutagenesis identifying K1487 site plus E2/E3 genetic analysis, but single lab","pmids":["19384408"],"is_preprint":false},{"year":2019,"finding":"In fission yeast, Bur1 (Cdk9) is the kinase responsible for phosphorylation of the Rpb1 linker in vivo; phosphorylation of the linker enhances binding of the Spt6 tandem SH2 domain. Inhibition of Cdk7/Kin28 blocked both Ser5-P and Ser7-P and also abolished Ser2-P, supporting obligatory sequential phosphorylation.","method":"Covalent kinase inhibitor (analog-sensitive alleles), ChIP, in vitro binding assay (Spt6-tSH2 domain)","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — selective kinase inhibition in vivo with multiple CTD phosphorylation readouts plus Spt6 binding validation","pmids":["31085683"],"is_preprint":false},{"year":2013,"finding":"The CTD of Rpb1 can function when transferred to other Pol II subunits (Rpb4 or Rpb6) near the original CTD position and still support viability, phosphorylation, and factor recruitment; CTD fused to Rpb9 on the opposite face of Pol II fails to rescue. CTD fused to Rpb6 does not confer CTD functions on Pol I or Pol III.","method":"CTD domain-transfer genetic complementation, in vivo CTD phosphorylation assay, factor recruitment ChIP","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic rescue combined with phosphorylation and factor-recruitment readouts, multiple subunit fusions tested","pmids":["24035501"],"is_preprint":false},{"year":2012,"finding":"Sen1 interacts directly with the Ser2-phosphorylated CTD of Rpb1; the sen1-R302W mutation impairs this interaction, reduces Sen1 occupancy across noncoding genes, and disrupts transcription termination of noncoding RNAs. A handoff model is proposed where factors transfer from Ser5-P to Ser2-P CTD during transcription.","method":"Two-hybrid analysis, co-immunoprecipitation, chromatin immunoprecipitation (ChIP)","journal":"Eukaryotic cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal two-hybrid plus Co-IP plus ChIP occupancy analysis, single lab","pmids":["22286094"],"is_preprint":false},{"year":2012,"finding":"Fission yeast Cdk9 (P-TEFb) requires a C-terminal extension distinct from the catalytic domain for binding to capping enzyme Pcm1 and for Spt5 phosphorylation; this extension is dispensable for recognition of Ser7-pre-phosphorylated (primed) CTD substrates. On peptide substrates in vitro, Cdk9 prefers Ser7-phosphorylated CTD repeats over unmodified repeats.","method":"In vitro kinase assay on CTD peptides, domain-deletion mutants, chromatin immunoprecipitation, genetic suppression","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro kinase assay on defined substrates plus in vivo ChIP and genetic suppression with two orthogonal methods","pmids":["22508988"],"is_preprint":false},{"year":2015,"finding":"In fission yeast, phosphorylation of Rpb1 CTD Ser2 by Lsk1 (Cdk12 orthologue) positively regulates H3K36 methylation but negatively regulates H3K4 methylation; Ser5 is required for H3K36me and H2B monoubiquitylation. Spt5 CTD Thr1 phosphorylation independently regulates H3K4me. Combinatorial CTD mutations potentiate histone modification defects.","method":"CTD phosphosite mutagenesis (Rpb1 and Spt5), histone modification analysis, kinase inactivation","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic CTD mutagenesis with multiple histone modification readouts, single lab","pmids":["26275777"],"is_preprint":false},{"year":2016,"finding":"Somatic missense mutations p.Gln403Lys or p.Leu438_His439del in POLR2A (encoding the catalytic subunit RPB1) are recurrently found in meningiomas; these mutant tumors show dysregulation of meningeal identity genes WNT6 and ZIC1/ZIC4, defining a mutually exclusive meningioma subgroup.","method":"Next-generation genomic sequencing of 775 meningiomas, transcriptional profiling of mutant tumors","journal":"Nature genetics","confidence":"Medium","confidence_rationale":"Tier 3 / Strong — large-scale somatic mutation discovery with transcriptional profiling, but mechanism is correlative (no in vitro reconstitution of mutant enzyme activity)","pmids":["27548314"],"is_preprint":false},{"year":2019,"finding":"De novo heterozygous POLR2A missense variants cause a neurodevelopmental syndrome with severe infantile-onset hypotonia via a dominant-negative mechanism: variants with mild structural effects produce malfunctioning Pol II and dominant-negative transcription inhibition, while loss-of-function variants (haploinsufficiency) yield milder phenotypes. Yeast functional assays confirmed impaired pol II activity.","method":"Structural evaluation of variants mapped to crystal structure, mass spectrometry, yeast (S. cerevisiae) functional assays, cell viability assays in HeLa cells","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — structural mapping, yeast functional assays, and cell viability assays across 11 variants in a single study using multiple orthogonal methods","pmids":["31353023"],"is_preprint":false},{"year":2011,"finding":"The SRI domain of human RECQ5 mediates interaction with RNAPII (Rpb1) and is required for suppressing spontaneous DNA double-strand breaks during replication; RECQ5 depletion causes accumulation of active RNAPII on chromatin and DSBs at RNAPII-transcribed loci, which are eliminated by transcription inhibition.","method":"RECQ5 siRNA depletion, SRI domain mutants, chromatin fractionation, DSB detection (γH2AX), transcription inhibitor rescue","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain-mapping plus rescue experiment with transcription inhibitor, multiple readouts, single lab","pmids":["21402780"],"is_preprint":false},{"year":2002,"finding":"In Xenopus oocyte germinal vesicle, RPB1 exists in at least three distinct populations with different CTD phosphorylation states: nucleoplasmic (unphosphorylated CTD), lampbrush chromosome-associated (Ser2-P and Ser5-P), and Cajal body-associated (unphosphorylated and Ser5-P). GST-fused CTD repeat constructs (15–17 repeats) are rapidly and specifically targeted to Cajal bodies upon nuclear injection.","method":"Immunofluorescence with phospho-specific antibodies, nuclear injection of GST-CTD constructs, subcellular fractionation","journal":"Journal of structural biology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — direct localization with functional CTD injection experiment, multiple phospho-specific antibodies, single lab","pmids":["12490164"],"is_preprint":false},{"year":1998,"finding":"Two-hybrid mapping of fission yeast Rpb1 showed that Rpb5 interacts with the conserved region H of Rpb1 (also found in RNA Pol I subunit Rpa190), while Rpb3 contacts the region H of Rpb2; these interactions define inter-subunit contacts within the Pol II complex.","method":"Yeast two-hybrid screening with Rpb1 and Rpb2 fragment libraries","journal":"Molecular & general genetics : MGG","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — two-hybrid mapping with multiple subunit fragments; widely reproduced in context of Pol II structure but single two-hybrid method","pmids":["9738888"],"is_preprint":false},{"year":2013,"finding":"RPB1 mutations in S. cerevisiae that increase transcriptional slippage on homopolymeric runs were identified in residues throughout the catalytic center; biochemical characterization of isolated Pol II from these mutants confirmed elevated transcriptional slippage in vitro, demonstrating that Rpb1 active-site residues determine register maintenance during RNA synthesis.","method":"Genetic screen (6-AU sensitivity and slippage reporter), in vitro transcriptional slippage assay with purified Pol II","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro biochemical assay on purified enzyme from yeast mutants, confirming genetic result with direct enzymatic readout","pmids":["23223234"],"is_preprint":false},{"year":2006,"finding":"RPB1 point mutations in the 'lid', 'rudder', and catalytic center (e.g., rpb1-N488D and rpb1-E1103G) cause opposite effects on intrinsic in vitro polymerization rate of RNAPII; rpb1-E1230K reduces RNAPII–TFIIS interaction. Synthetic genetic interactions with soh1, spt4, and dst1 were observed.","method":"6-AU sensitivity screen, in vitro transcription elongation assay, genetic epistasis (synthetic interactions)","journal":"Genetics","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro polymerization assay on purified Pol II from mutants plus genetic epistasis, single lab but multiple orthogonal methods","pmids":["16510790"],"is_preprint":false},{"year":2019,"finding":"XAB2 depletion causes severe intron retention in POLR2A pre-mRNA, reducing POLR2A mRNA and protein levels, which impairs global transcription and induces cellular senescence via p53/p21 upregulation; XAB2 associates with spliceosome components (including SNW1 via TPR motifs 2–4 and 11) important for POLR2A expression; re-expression of POLR2A in XAB2-depleted cells rescues senescence.","method":"XAB2 siRNA knockdown, RNA-seq (splicing analysis), TMT-based quantitative proteomics, immunoprecipitation (XAB2-SNW1), POLR2A rescue experiment","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (RNA-seq, proteomics, Co-IP, rescue), single lab","pmids":["31216022"],"is_preprint":false},{"year":2016,"finding":"Triptolide causes RPB1 degradation and transcriptional inhibition through a CDK7-dependent mechanism: CDK7 phosphorylates Thr170 (activation) and a specific site on RPB1 (Ser1878); CDK7 inhibitor (BS-181) partially rescues RPB1 degradation and cell killing. XPB and p44 (TFIIH subunits) do not contribute to triptolide-driven RPB1 degradation.","method":"CDK7 inhibitor treatment, Western blot for RPB1 degradation, phospho-specific antibody for CDK7 Thr170 and RPB1 Ser1878, siRNA knockdown","journal":"Molecular cancer therapeutics","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — pharmacological inhibitor plus phospho-site identification with rescue, but limited mutagenesis validation of Ser1878 site","pmids":["27197304"],"is_preprint":false},{"year":2021,"finding":"In Alzheimer disease hippocampal neurons, two phospho-isoforms of RPB1 mislocalize from the nucleus to the cytoplasm; the number of neurons with cytoplasmic RPB1 correlates with AT8-positive (pathologic tau) burden. In the rTg4510 tau mouse model, cytoplasmic mislocalization of Rpb1 increases in a tau- and age-dependent manner.","method":"Immunofluorescence on human AD and control tissue, rTg4510 transgenic mouse model (regulatable pathologic tau P301L), quantitative correlation analysis","journal":"Journal of neuropathology and experimental neurology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — direct localization experiment with causal tau model; correlation with tau burden and age-dependent effect in mouse model, but mechanistic link is correlative","pmids":["33990839"],"is_preprint":false},{"year":2021,"finding":"POLR2A interacts with CREB1 and regulates assembly of CREB1 on regulatory elements of osteoclast target genes; osteoclast-specific deletion of POLR2A blocks bone resorption in vivo, and POLR2A inhibition suppresses estrogen deficiency-induced bone resorption.","method":"Co-immunoprecipitation (POLR2A–CREB1), osteoclast-specific conditional Polr2a knockout mice, ChIP for CREB1 at target gene regulatory elements, in vitro osteoclastogenesis assay","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ChIP plus conditional KO mouse model, single lab","pmids":["33595106"],"is_preprint":false},{"year":2025,"finding":"USP10 deubiquitinase directly interacts with POLR2A, removes K48- and K63-linked ubiquitin chains from POLR2A through its deubiquitinase activity, and prevents ubiquitin-mediated POLR2A degradation; stabilized POLR2A then transcriptionally activates SLC7A11 to suppress ferroptosis in head and neck squamous cell carcinoma.","method":"Co-immunoprecipitation (USP10–POLR2A), in vitro deubiquitination assay, USP10 gene depletion and antagonist, ChIP for POLR2A at SLC7A11 promoter","journal":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, in vitro deubiquitination assay, and ChIP, single lab","pmids":["40605431"],"is_preprint":false},{"year":2022,"finding":"Rtr1 (a known Pol II CTD phosphatase) cooperates with Gpn3 and Npa3 to assemble the two largest RNAPII subunits (Rpb1–Rpb2); RTR1 deletion causes cytoplasmic clumping of RNAPII subunits; multicopy RTR1 suppresses cytoplasmic clumping in gpn3-9 mutants. The phosphatase catalytic activity of Rtr1 is dispensable for this assembly function.","method":"Genetic suppressor screen (multicopy RTR1), cytoplasmic clump assay (fluorescence), catalytically inactive RTR1 mutant","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — genetic suppression with catalytic separation-of-function mutant and localization assay, single lab","pmids":["36190433"],"is_preprint":false},{"year":2015,"finding":"In mouse oocytes, phospho-RPB1 (Ser2) localizes to spindle poles and co-localizes with MTOC components (pericentrin and γ-tubulin) after meiotic resumption; phospho-RPB1 (Ser5 and Ser7) assembles as filamentous aggregates co-localizing with microtubules throughout the spindle and responds to nocodazole/taxol similarly to microtubules. Ser2-P and Ser5-P are also concentrated at centromere areas on chromosomes.","method":"Immunofluorescence with phospho-specific antibodies, spindle-disturbing drug treatments (nocodazole, taxol), co-localization with MTOC markers","journal":"The Journal of reproduction and development","confidence":"Low","confidence_rationale":"Tier 3 / Weak — localization study without functional consequence demonstrated; co-localization is suggestive but no loss-of-function readout for the meiotic role","pmids":["26346254"],"is_preprint":false},{"year":2022,"finding":"Disrupting the Spt6-tSH2:Rpb1 linker interface affects transcription start site selection at specific gene subsets, reduces splicing efficiency, impairs chromatin-mediated repression, and diminishes +1 nucleosome maintenance at ribosomal protein genes; the interaction modulates Spt6 recruitment and elongation complex coordination.","method":"Interface-disrupting mutations in Spt6-tSH2 domain, RNA-seq (TSS analysis, splicing), ChIP (Spt6 occupancy), MNase-seq (nucleosome positioning)","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal genomic methods with defined interface mutations, single lab","pmids":["34967414"],"is_preprint":false},{"year":2016,"finding":"Rpb1 foot-region mutations in yeast alter assembly of Rpb6 and the Rpb4/7 dimer, activate an environmental stress response (ESR) at permissive temperature, and this ESR depends on Rpb4-mediated post-transcriptional mRNA stability (mRNA imprinting) rather than transcription alone.","method":"RPB1 foot-region mutant analysis, global transcriptional analysis, mRNA stability assay, genetic analysis with Rpb4","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genome-wide transcription and mRNA decay analysis combined with genetic dependence on Rpb4, single lab","pmids":["27001033"],"is_preprint":false},{"year":2025,"finding":"OROV NSs protein co-localizes with nucleophosmin 1 (NPM1) and promotes proteasomal degradation of hyperphosphorylated RNAP II (RPB1), reducing Ser2-P and Ser5-P CTD phosphorylation and suppressing nascent RNA synthesis; RPB1 loss is rescued by proteasome inhibitor MG132.","method":"OROV infection and NSs expression, proteasome inhibitor (MG132) rescue, Western blot for RPB1 and CTD phospho-isoforms, nascent RNA quantification","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Weak — single lab, single published study; MG132 rescue is informative but mechanistic details of NSs–RPB1 interaction not deeply characterized","pmids":["40928251"],"is_preprint":false},{"year":2026,"finding":"E3 ligase LMO7 is recruited to POLR2A and promotes its ubiquitination and proteasomal degradation during cellular senescence; LMO7 depletion abolishes POLR2A ubiquitination and reduction in H2O2-induced senescent cells. POLR2A knockdown induces senescence through MDM4-mediated p53/p21 pathway activation.","method":"Co-immunoprecipitation (LMO7–POLR2A), ubiquitination assay, LMO7/POLR2A siRNA knockdown, CRISPRa re-activation, RNA-seq","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP plus ubiquitination assay plus CRISPRa rescue; multiple orthogonal methods but single lab, recently published","pmids":["41896199"],"is_preprint":false},{"year":2025,"finding":"Nuclear PD-L1 (following IFN-γ-induced HDAC2-mediated deacetylation and nuclear translocation) physically binds POLR2A and forms a transcriptional complex that directly activates LY6E expression, promoting TNBC lung metastasis independently of immune checkpoint function.","method":"CRISPR/Cas9 PD-L1 knockout, Co-immunoprecipitation (PD-L1–POLR2A), ChIP-seq (PD-L1 and POLR2A at LY6E locus), RNA-seq","journal":"Breast cancer research : BCR","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and ChIP-seq with CRISPR KO rescue, single lab, multiple orthogonal methods","pmids":["41388312"],"is_preprint":false},{"year":2013,"finding":"Sequence-specific DNA double-strand breaks (DSBs) activate P-TEFb, triggering hyperphosphorylation of the Rpb1 CTD and subsequent p53-dependent transcriptional activation leading to cell cycle arrest.","method":"Inducible restriction enzyme DSB system, P-TEFb activity assay, Rpb1-CTD hyperphosphorylation Western blot, p53 target gene induction","journal":"Mutation research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, P-TEFb activity inferred from CTD phosphorylation state; no direct in vitro reconstitution of the P-TEFb–Rpb1 relationship under DSB conditions","pmids":["23906511"],"is_preprint":false},{"year":2024,"finding":"Leveraging ERLIC/HILIC chromatography with engineered msCTD, MS analysis confirmed that Ser5-P and Ser2-P are the dominant endogenous CTD phosphoisoforms in yeast, consistent with a simple 'CTD code', and demonstrated that these marks occur throughout CTD length.","method":"Mass spectrometry (HILIC/ERLIC LC-MS/MS) of engineered yeast msCTD","journal":"bioRxiv (preprint)","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — quantitative mass spectrometry on modified CTD; technically rigorous but preprint and replicates findings already established by peer-reviewed msCTD work","pmids":[],"is_preprint":true},{"year":2024,"finding":"UV-induced RPB1 degradation occurs in trans and is controlled by NER activity regardless of how the DNA lesion is recognized (by stalled RNAPII or GG-NER factors XPE/XPC); absence of any core NER factor enhances RPB1 degradation, and damage-induced degradation depends on Cullin-RING ubiquitin ligases and is not restricted to actively transcribing or phosphorylated RPB1 molecules.","method":"NER factor mutants (TC-NER and GG-NER), Cullin-RING inhibitor, UV irradiation, Western blot for RPB1 degradation","journal":"bioRxiv (preprint)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple NER mutants with pharmacological inhibitor, novel trans mechanism, but preprint only","pmids":[],"is_preprint":true},{"year":2024,"finding":"STK19 is an integral component of the Pol II–TC-NER complex; cryo-EM shows STK19 bridges CSA with UVSSA, RPB1, and downstream DNA; STK19 stimulates CRL4CSA E3 ligase activity resulting in efficient Pol II (RPB1 K1268) ubiquitylation and correct UVSSA/TFIIH binding for TC-NER.","method":"Cryo-EM structure of TC-NER complex, live-cell imaging, Co-immunoprecipitation, CRL4CSA ubiquitination assay","journal":"bioRxiv (preprint)","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — cryo-EM structure plus ubiquitination assay plus live-cell imaging; rigorous multi-method study but preprint","pmids":[],"is_preprint":true},{"year":2024,"finding":"STK19 joins the TC-NER complex by binding CSA and the RPB1 subunit of Pol II (1.9 Å cryo-EM structure); AlphaFold modeling and mutational disruption of STK19–XPD interface impairs cell-free TC-NER, suggesting STK19 positions TFIIH ahead of Pol II for lesion verification.","method":"1.9 Å cryo-EM, in vitro TC-NER reconstitution in frog egg extract, interface mutant disruption, AlphaFold modeling","journal":"bioRxiv (preprint)","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — near-atomic cryo-EM with cell-free functional reconstitution; preprint, but independently corroborated by companion study (Ramadhin et al.)","pmids":[],"is_preprint":true},{"year":2024,"finding":"Loss of Pol II protein (Rpb1 specifically) — but not loss of transcriptional activity — activates a specific apoptotic pathway termed PDAR (Pol II Degradation-dependent Apoptotic Response); expression of a transcriptionally inactive Rpb1 rescues viability after Pol II loss.","method":"Rpb1 catalytic-dead mutant rescue experiment, functional genomics (PDAR genetic dependencies), Pol II depletion","journal":"bioRxiv (preprint)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — catalytic separation-of-function rescue combined with functional genomics screen; preprint, single lab","pmids":[],"is_preprint":true},{"year":2025,"finding":"CDK11 phosphorylates the Rpb1 linker domain (analogous to yeast Bur1) and the hSpt5 repeat region; CDK11 inhibition reduces active Pol II at TSS and gene bodies. CDK11 is also required for phosphorylation and activation of CDK12, which drives Pol II elongation.","method":"CDK11 inhibition (selective inhibitor), ChIP-seq for active Pol II, in vitro kinase assay, CDK12 phosphorylation Western blot","journal":"bioRxiv (preprint)","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — selective kinase inhibition plus in vitro kinase assay, establishing CDK11→CDK12 kinase cascade with multiple readouts; preprint","pmids":[],"is_preprint":true},{"year":2025,"finding":"IWS1 interacts with Pol II subunits RPB1 (via the RPB1 jaw domain, dependent on downstream DNA binding), RPB2, and RPB5, as well as elongation factors DSIF, SPT6, and ELOF1, as revealed by cryo-EM mapping of short linear motifs (SLiMs) in the intrinsically disordered C-terminal region of IWS1. IWS1 protects the elongation complex from RECQL5 inhibition.","method":"Cryo-EM of IWS1–Pol II elongation complex, functional SLiM mutagenesis, in vitro transcription stimulation assay","journal":"bioRxiv (preprint)","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — cryo-EM structure plus functional mutagenesis and in vitro transcription assay; preprint, novel mechanistic findings not yet in peer-reviewed form","pmids":[],"is_preprint":true},{"year":2025,"finding":"RECQ5 attenuates RNAPII transcription elongation via two mechanisms: (1) at atomic level, its brake helix acts as a doorstop controlling Pol II translocation along DNA; (2) at mesoscale, RECQ5 forms a condensate scaffold integrating hyperphosphorylated Pol II elongation complexes via site-specific interactions with CTD (RPB1).","method":"Biochemical reconstitution, cryo-EM, cryotomography, coarse-grained simulations","journal":"bioRxiv (preprint)","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — cryo-EM and reconstitution with multi-scale approach; preprint, novel structural mechanism","pmids":[],"is_preprint":true},{"year":2025,"finding":"Minnelide (triptolide pro-drug) acts through xeroderma pigmentosum type B (XPB) to alter RPB1 phosphorylation and subsequent proteasomal degradation, inducing apoptosis of CIC::DUX4 sarcoma cells in vitro and in vivo.","method":"Transcription inhibitor screen, RPB1 phosphorylation and degradation Western blot, in vivo xenograft and GEMM models","journal":"bioRxiv (preprint)","confidence":"Low","confidence_rationale":"Tier 3 / Weak — preprint, RPB1 phosphorylation and degradation measured but XPB–RPB1 mechanistic link is inferred rather than directly reconstituted","pmids":[],"is_preprint":true},{"year":1998,"finding":"The full-length mouse RPB1 can functionally substitute for the yeast S. cerevisiae RPB1 in vivo, supporting viability when expressed from the yeast promoter via homologous recombination, demonstrating structural and functional conservation of RPB1 across mammals and yeast.","method":"Homologous recombination gene replacement, haploid viability assay, Northern analysis","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct in vivo genetic complementation across species, single study","pmids":["9524248"],"is_preprint":false}],"current_model":"POLR2A/RPB1 is the catalytic largest subunit of RNA polymerase II whose C-terminal domain (CTD) undergoes dynamic, stage-specific phosphorylation (primarily at Ser2, Ser5, and Ser7 of the YSPTSPS heptad repeats) by CDK7/TFIIH (Ser5, Ser7), CDK9/Bur1 (Rpb1 linker, Spt5), and CDK12/Ctk1 (Ser2), creating a 'CTD code' that recruits capping enzymes, splicing factors, histone-modifying enzymes (Set2 SRI domain via Ser2+Ser5-P), and termination factors; the CTD can function when transferred to nearby Pol II subunits (Rpb4, Rpb6) but not to distant ones, showing spatial but not strict physical linkage to the catalytic core is required; in response to DNA damage (UV or transcription-blocking lesions), RPB1 is ubiquitylated by multiple E3 ligase complexes including Elongin A–BC–Cul5/Rbx2 (recognizing Ser5-P RPB1), ARMC5–CUL3–RBX1, and CRL4CSA (at K1268 in TC-NER), and degraded by the 26S proteasome in a process facilitated by Rpb9 and regulated in trans by NER completion; RPB1 is additionally sumoylated at K1487 by Ubc9/Siz1 to restrain DNA damage checkpoint signaling; viral proteins (alphavirus nsP2, OROV NSs) hijack RPB1 ubiquitination to suppress host transcription; dominant-negative missense variants of POLR2A cause a neurodevelopmental syndrome by producing malfunctioning Pol II that impairs global transcription, whereas haploinsufficiency has milder effects; loss of the RPB1 protein itself (independent of transcriptional activity) triggers a specific apoptotic program (PDAR); and live-cell imaging reveals that promoter-paused Pol II has unexpectedly high turnover (~42 sec) compared to elongating Pol II (~23 min)."},"narrative":{"mechanistic_narrative":"POLR2A/RPB1 is the catalytic largest subunit of RNA polymerase II, providing the active-site residues that maintain transcriptional register during RNA synthesis and whose function is conserved deeply enough that mouse RPB1 substitutes for yeast Rpb1 in vivo [PMID:23223234, PMID:9524248]. Active-site mutations in the lid, rudder, and catalytic center alter intrinsic polymerization rates and TFIIS interaction, and mutations across the catalytic center elevate transcriptional slippage on homopolymeric runs [PMID:23223234, PMID:16510790]. RPB1 activity is orchestrated through stage-specific phosphorylation of its C-terminal domain (CTD) heptad repeats, in which Ser5-P and Ser2-P are the dominant marks deposited and removed by dedicated kinases and phosphatases to form a sparse 'CTD code' [PMID:26799764]: TFIIH/Kin28(CDK7) establishes Ser5-P and Ser7-P, with Ser7-P priming subsequent events, while CDK9/Bur1 and CDK11 phosphorylate the Rpb1 linker and Spt5, and CDK12 orthologues deposit Ser2-P [PMID:19679665, PMID:31085683, PMID:22508988]. These marks recruit and hand off effectors—capping enzyme via Ser5-P, the Set2 SRI domain via doubly Ser2+Ser5-phosphorylated CTD to direct H3K36 methylation, the Spt6 tandem-SH2 domain to the phosphorylated linker, and termination factors Sen1/Rtt103 via Ser2-P [PMID:26799764, PMID:16314571, PMID:22286094, PMID:26275777, PMID:34967414]. The CTD remains functional when relocated to neighboring Pol II subunits (Rpb4, Rpb6) but not to distant ones, indicating spatial rather than strict physical linkage to the core is required [PMID:24035501]. In response to UV and transcription-blocking lesions, RPB1 is ubiquitylated by multiple Cullin-RING E3 complexes—Elongin A–BC–Cul5/Rbx2 recognizing Ser5-P RPB1, ARMC5–CUL3–RBX1, and CRL4CSA targeting K1268 within the Pol II–TC-NER complex—and degraded by the 26S proteasome in a process facilitated by Rpb9 and controlled in trans by NER completion [PMID:19037258, PMID:17452455, PMID:35687106]; this degradation is opposed by the deubiquitinase USP10 [PMID:40605431] and is hijacked by viral proteins (alphavirus nsP2, OROV NSs) to suppress host transcription [PMID:22514352, PMID:40928251]. RPB1 is additionally sumoylated at K1487 by Ubc9/Siz1 to restrain DNA-damage checkpoint signaling [PMID:19384408]. De novo heterozygous POLR2A missense variants cause a neurodevelopmental syndrome through a dominant-negative mechanism that yields malfunctioning Pol II, whereas haploinsufficiency produces milder effects [PMID:31353023], and recurrent somatic POLR2A mutations define a meningioma subgroup with dysregulated meningeal identity genes [PMID:27548314].","teleology":[{"year":1998,"claim":"Establishing that the mammalian and yeast catalytic subunit are functionally interchangeable validated yeast as a faithful model for human RPB1 mechanism and confirmed deep conservation.","evidence":"Homologous-recombination gene replacement and haploid viability assay with full-length mouse RPB1 in S. cerevisiae","pmids":["9524248"],"confidence":"Medium","gaps":["Does not address conservation of CTD-dependent regulatory functions","No quantitative comparison of transcriptional output"]},{"year":1998,"claim":"Mapping inter-subunit contacts addressed how RPB1 is held within the Pol II assembly, defining the region H interaction with Rpb5.","evidence":"Yeast two-hybrid mapping with Rpb1 and Rpb2 fragment libraries","pmids":["9738888"],"confidence":"Medium","gaps":["Single two-hybrid method without structural confirmation","Does not establish functional consequence of contacts"]},{"year":2006,"claim":"Pinpointing active-site residues whose mutation alters intrinsic polymerization rate and TFIIS interaction established that RPB1 catalytic geometry directly governs elongation behavior.","evidence":"6-AU sensitivity screen, in vitro transcription elongation assay on purified Pol II mutants, genetic epistasis","pmids":["16510790"],"confidence":"High","gaps":["Catalytic mechanism inferred from rate effects, not atomic structure","Single-lab genetic interaction set"]},{"year":2005,"claim":"Structurally defining how the Set2 SRI domain reads doubly Ser2+Ser5-phosphorylated CTD answered how a specific histone-modifying enzyme is recruited by the CTD code.","evidence":"NMR structure, NMR titration, SPR binding, point mutagenesis of SRI domain","pmids":["16314571"],"confidence":"High","gaps":["Binding measured on peptides, not full elongation complex","Does not establish in vivo kinetics of recruitment"]},{"year":2007,"claim":"Identifying the Rpb9 Zn2 domain as required for damage-induced Rpb1 degradation but dispensable for elongation separated the polymerase's catalytic role from its turnover.","evidence":"UV irradiation, Rpb9 domain-deletion mutants, Co-IP, proteasome inhibitor","pmids":["17452455"],"confidence":"High","gaps":["Mechanism by which Rpb9 promotes ubiquitylation unresolved","Single-organism (yeast) study"]},{"year":2008,"claim":"Reconstituting the Elongin A–BC–Cul5/Rbx2 ligase that recognizes Ser5-P RPB1 identified a defined E3 machinery for UV-induced RPB1 destruction.","evidence":"In vitro ubiquitylation with reconstituted complex, Elongin A KD/rescue, Co-IP","pmids":["19037258"],"confidence":"High","gaps":["Ubiquitin chain linkage type not characterized","Redundancy with other ligases not resolved at this stage"]},{"year":2009,"claim":"Demonstrating Ser7 phosphorylation in vivo by TFIIH and distinguishing it from Ser5 expanded the CTD code beyond Ser2/Ser5.","evidence":"ChIP, in vitro kinase assay, Rtr1 phosphatase deletion","pmids":["19679665"],"confidence":"High","gaps":["Functional readers of Ser7-P not identified here","Yeast-specific phosphatase logic"]},{"year":2009,"claim":"Identifying K1487 sumoylation by Ubc9/Siz1 that restrains the DNA-damage checkpoint defined a SUMO-based brake on checkpoint signaling at transcription-blocking lesions.","evidence":"UV irradiation, SUMO pathway mutants, K1487 site-directed mutagenesis, Rad53 phosphorylation assay","pmids":["19384408"],"confidence":"Medium","gaps":["SUMO readers downstream of K1487 unknown","Single-lab yeast study"]},{"year":2012,"claim":"Defining Sen1 binding to Ser2-P CTD and a Ser5-to-Ser2 handoff model addressed how the CTD code temporally directs termination of noncoding transcription.","evidence":"Two-hybrid, Co-IP, ChIP with sen1-R302W mutant","pmids":["22286094"],"confidence":"Medium","gaps":["Handoff model not directly visualized","Single-lab correlative occupancy data"]},{"year":2012,"claim":"Showing that Cdk9 prefers Ser7-primed CTD and requires a C-terminal extension for capping-enzyme/Spt5 engagement clarified the sequential, substrate-primed logic of CTD phosphorylation.","evidence":"In vitro kinase assay on CTD peptides, Cdk9 domain mutants, ChIP, genetic suppression","pmids":["22508988"],"confidence":"High","gaps":["Does not establish in vivo order quantitatively across genes","Fission-yeast specific"]},{"year":2012,"claim":"Demonstrating that alphavirus nsP2 triggers RPB1 ubiquitination/degradation independently of its protease showed pathogens exploit RPB1 turnover to shut down host transcription.","evidence":"Viral infection, nsP2 domain point mutants, proteasome inhibitor, ubiquitination Western blot","pmids":["22514352"],"confidence":"High","gaps":["Host E3 ligase recruited by nsP2 not identified","Direct nsP2–RPB1 interaction not mapped"]},{"year":2013,"claim":"Showing the CTD remains functional when fused to neighboring subunits but not distant ones established that spatial proximity, not covalent linkage to the catalytic subunit, is what the CTD requires.","evidence":"CTD domain-transfer complementation, in vivo phosphorylation, factor-recruitment ChIP","pmids":["24035501"],"confidence":"High","gaps":["Does not explain why Pol I/III cannot adopt CTD function","Geometric constraints quantified only by subunit choice"]},{"year":2013,"claim":"Confirming that catalytic-center mutations elevate transcriptional slippage established RPB1 active-site residues as direct determinants of register maintenance.","evidence":"Genetic slippage screen plus in vitro slippage assay on purified mutant Pol II","pmids":["23223234"],"confidence":"High","gaps":["Structural basis of register slippage not resolved","Yeast-only system"]},{"year":2015,"claim":"Linking Ser2/Ser5 CTD marks to opposing effects on H3K36 versus H3K4 methylation connected the CTD code to combinatorial chromatin modification during elongation.","evidence":"Rpb1 and Spt5 CTD phosphosite mutagenesis, histone modification analysis, kinase inactivation","pmids":["26275777"],"confidence":"Medium","gaps":["Mechanism of negative H3K4 regulation unclear","Single-lab fission-yeast study"]},{"year":2016,"claim":"Quantitative msCTD mass spectrometry established that Ser5-P and Ser2-P dominate and partition with specific effectors, providing direct evidence for a sparse rather than combinatorially dense CTD code.","evidence":"Engineered CTD mass spectrometry, affinity purification with capping enzyme and Rtt103, kinase/phosphatase mutants","pmids":["26799764"],"confidence":"High","gaps":["Spatial distribution along genes not resolved","Low-abundance marks may have undetected roles"]},{"year":2016,"claim":"Recurrent somatic POLR2A missense mutations defining a meningioma subgroup implicated RPB1 dysfunction in tumor identity-gene dysregulation.","evidence":"NGS of 775 meningiomas plus transcriptional profiling of mutant tumors","pmids":["27548314"],"confidence":"Medium","gaps":["No in vitro reconstitution of mutant enzyme activity","Mechanistic link to WNT6/ZIC1 dysregulation is correlative"]},{"year":2016,"claim":"Demonstrating that triptolide drives CDK7-dependent RPB1 phosphorylation (Ser1878) and degradation defined a pharmacological route to RPB1 destabilization.","evidence":"CDK7 inhibitor, phospho-specific antibodies for CDK7 Thr170 and RPB1 Ser1878, siRNA","pmids":["27197304"],"confidence":"Medium","gaps":["Ser1878 site validated without mutagenesis","E3 ligase mediating degradation not identified"]},{"year":2018,"claim":"Live-cell FRAP of endogenous GFP-RPB1 resolved discrete kinetic Pol II populations, revealing that promoter-paused Pol II turns over far faster (~42 s) than elongating Pol II (~23 min).","evidence":"GFP-RPB1 knockin, FRAP, computational kinetic modeling","pmids":["29632207"],"confidence":"High","gaps":["Molecular basis of high pause turnover (premature termination) inferred","Population assignments depend on model assumptions"]},{"year":2019,"claim":"Showing dominant-negative POLR2A missense variants cause a neurodevelopmental syndrome while LOF variants are milder defined the genotype–phenotype logic of human Pol II disease.","evidence":"Structural mapping of 11 variants, yeast functional assays, HeLa viability assays","pmids":["31353023"],"confidence":"High","gaps":["Gene-specific transcriptional consequences in patient neurons not mapped","Mechanism of dominant-negative interference at molecular level not resolved"]},{"year":2019,"claim":"Identifying that Bur1/Cdk9 phosphorylates the Rpb1 linker to recruit the Spt6 tandem-SH2 domain, with Kin28 inhibition abolishing downstream marks, established obligatory sequential CTD/linker phosphorylation feeding elongation factor recruitment.","evidence":"Analog-sensitive kinase inhibition, ChIP, in vitro Spt6-tSH2 binding","pmids":["31085683"],"confidence":"High","gaps":["Quantitative dependency of Ser2-P on prior marks not fully dissected","Fission-yeast specific"]},{"year":2019,"claim":"Linking XAB2-dependent splicing of POLR2A pre-mRNA to senescence showed that RPB1 abundance is post-transcriptionally controlled and that its loss engages p53/p21.","evidence":"XAB2 siRNA, RNA-seq splicing analysis, TMT proteomics, XAB2-SNW1 Co-IP, POLR2A rescue","pmids":["31216022"],"confidence":"Medium","gaps":["Direct splicing mechanism on POLR2A introns not resolved","Single-lab study"]},{"year":2021,"claim":"Identifying POLR2A interaction with CREB1 to assemble on osteoclast target genes, and PD-L1 to activate LY6E, extended RPB1 roles to specific transcription-factor–directed programs in physiology and metastasis.","evidence":"Co-IP, ChIP/ChIP-seq, conditional Polr2a knockout mice, CRISPR KO (PD-L1)","pmids":["33595106","41388312"],"confidence":"Medium","gaps":["Whether these are general or gene-specific recruitment events unclear","Single-lab studies"]},{"year":2022,"claim":"Defining the ARMC5–CUL3–RBX1 complex as an RPB1-specific E3 ligase added a CUL3-based pathway controlling RPB1 abundance, with disease relevance via PBMAH mutations.","evidence":"Co-IP, in vitro E3 ligase assay, Armc5 knockout mouse, RPB1 ubiquitination Western blot","pmids":["35687106"],"confidence":"Medium","gaps":["Ubiquitin linkage and degron on RPB1 not defined","Relationship to UV-induced ligases unclear"]},{"year":2022,"claim":"Characterizing the Spt6-tSH2:Rpb1 linker interface in vivo showed this contact coordinates TSS selection, splicing, repression, and +1 nucleosome maintenance.","evidence":"Interface-disrupting mutations, RNA-seq, Spt6 ChIP, MNase-seq","pmids":["34967414"],"confidence":"Medium","gaps":["Direct causal chain from interface to each phenotype not separated","Single-lab study"]},{"year":2025,"claim":"Identifying USP10 as a deubiquitinase that stabilizes POLR2A defined an opposing arm to RPB1 ubiquitination with downstream control of SLC7A11 and ferroptosis.","evidence":"Co-IP, in vitro deubiquitination assay, USP10 depletion/antagonist, POLR2A ChIP at SLC7A11","pmids":["40605431"],"confidence":"Medium","gaps":["Which E3-deposited chains USP10 antagonizes in vivo unclear","Single-lab cancer-context study"]},{"year":2025,"claim":"Showing OROV NSs promotes proteasomal degradation of hyperphosphorylated RPB1 added a second viral strategy converging on RPB1 turnover to suppress host transcription.","evidence":"OROV infection/NSs expression, MG132 rescue, CTD phospho-isoform Western blot, nascent RNA quantification","pmids":["40928251"],"confidence":"Medium","gaps":["NSs–RPB1 interaction not directly mapped","Host E3 ligase unidentified"]},{"year":null,"claim":"How the multiple RPB1 ubiquitination pathways (Elongin A, ARMC5-CUL3, CRL4CSA, LMO7), deubiquitination by USP10, sumoylation, and the PDAR apoptotic response are integrated to set RPB1 abundance and cell fate across stress and disease contexts remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model coordinating competing E3 ligases and USP10","Degron and chain-linkage specificity for each pathway not defined","Trigger that commits cells to PDAR versus survival unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[19,20]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[19,20]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[14,24,32]}],"localization":[{"term_id":"GO:0005654","term_label":"nucleoplasm","supporting_discovery_ids":[17]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[17,23]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[26]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[2,19,20]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[4,8,35,36]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[2,11,21]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[14,15]}],"complexes":["RNA polymerase II","Pol II–TC-NER complex"],"partners":["SETD2","SPT6","SEN1","ELOA","ARMC5","USP10","RECQ5","IWS1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P24928","full_name":"DNA-directed RNA polymerase II subunit RPB1","aliases":["3'-5' exoribonuclease","DNA-directed RNA polymerase II subunit A","DNA-directed RNA polymerase III largest subunit","RNA-directed RNA polymerase II subunit RPB1"],"length_aa":1970,"mass_kda":217.2,"function":"Catalytic core component of RNA polymerase II (Pol II), a DNA-dependent RNA polymerase which synthesizes mRNA precursors and many functional non-coding RNAs using the four ribonucleoside triphosphates as substrates (By similarity) (PubMed:23748380, PubMed:27193682, PubMed:30190596, PubMed:9852112). Pol II-mediated transcription cycle proceeds through transcription initiation, transcription elongation and transcription termination stages. During transcription initiation, Pol II pre-initiation complex (PIC) is recruited to DNA promoters, with focused-type promoters containing either the initiator (Inr) element, or the TATA-box found in cell-type specific genes and dispersed-type promoters that often contain hypomethylated CpG islands usually found in housekeeping genes. Once the polymerase has escaped from the promoter it enters the elongation phase during which RNA is actively polymerized, based on complementarity with the template DNA strand. Transcription termination involves the release of the RNA transcript and polymerase from the DNA (By similarity) (PubMed:23748380, PubMed:27193682, PubMed:28108474, PubMed:30190596, PubMed:9852112). Forms Pol II active center together with the second largest subunit POLR2B/RPB2. Appends one nucleotide at a time to the 3' end of the nascent RNA, with POLR2A/RPB1 most likely contributing a Mg(2+)-coordinating DxDGD motif, and POLR2B/RPB2 participating in the coordination of a second Mg(2+) ion and providing lysine residues believed to facilitate Watson-Crick base pairing between the incoming nucleotide and template base. Typically, Mg(2+) ions direct a 5' nucleoside triphosphate to form a phosphodiester bond with the 3' hydroxyl of the preceding nucleotide of the nascent RNA, with the elimination of pyrophosphate. The reversible pyrophosphorolysis can occur at high pyrophosphate concentrations (By similarity) (PubMed:30190596, PubMed:8381534, PubMed:9852112). Can proofread the nascent RNA transcript by means of a 3' -> 5' exonuclease activity. If a ribonucleotide is mis-incorporated, backtracks along the template DNA and cleaves the phosphodiester bond releasing the mis-incorporated 5'-ribonucleotide (By similarity) (PubMed:8381534). Through its unique C-terminal domain (CTD, 52 heptapeptide tandem repeats) serves as a platform for assembly of factors that regulate transcription initiation, elongation and termination. CTD phosphorylation on Ser-5 mediates Pol II promoter escape, whereas phosphorylation on Ser-2 is required for Pol II pause release during transcription elongation and further pre-mRNA processing. Additionally, the regulation of gene expression levels depends on the balance between methylation and acetylation levels of the CTD-lysines. Initiation or early elongation steps of transcription of growth-factor-induced immediate early genes are regulated by the acetylation status of the CTD. Methylation and dimethylation have a repressive effect on target genes expression. Cooperates with mRNA splicing machinery in co-transcriptional 5'-end capping and co-transcriptional splicing of pre-mRNA (By similarity) (PubMed:24207025, PubMed:26124092) RNA-dependent RNA polymerase that catalyzes the extension of a non-coding RNA (ncRNA) at the 3'-end using the four ribonucleoside triphosphates as substrates. An internal ncRNA sequence near the 3'-end serves as a template in a single-round Pol II-mediated RNA polymerization reaction. May decrease the stability of ncRNAs that repress Pol II-mediated gene transcription (Microbial infection) Acts as an RNA-dependent RNA polymerase when associated with small delta antigen of Hepatitis delta virus, acting both as a replicase and transcriptase for the viral RNA circular genome","subcellular_location":"Nucleus; Cytoplasm; Chromosome","url":"https://www.uniprot.org/uniprotkb/P24928/entry"},"depmap":{"release":"DepMap","has_data":false,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/POLR2A"},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000181222","cell_line_id":"CID000696","localizations":[{"compartment":"nucleoplasm","grade":3},{"compartment":"nuclear_punctae","grade":2}],"interactors":[{"gene":"MED14","stoichiometry":10.0},{"gene":"MED19","stoichiometry":10.0},{"gene":"PIH1D1","stoichiometry":10.0},{"gene":"POLR2K","stoichiometry":10.0},{"gene":"POLR2E","stoichiometry":10.0},{"gene":"POLR2C","stoichiometry":10.0},{"gene":"POLR2B","stoichiometry":10.0},{"gene":"CTDP1","stoichiometry":10.0},{"gene":"POLR2D","stoichiometry":10.0},{"gene":"POLR2G","stoichiometry":10.0}],"url":"https://opencell.sf.czbiohub.org/target/CID000696","total_profiled":1310},"omim":[{"mim_id":"621545","title":"GPN-LOOP GTPase 3; GPN3","url":"https://www.omim.org/entry/621545"},{"mim_id":"621544","title":"GPN-LOOP GTPase 2; GPN2","url":"https://www.omim.org/entry/621544"},{"mim_id":"618739","title":"CTD SMALL PHOSPHATASE-LIKE PROTEIN 2; CTDSPL2","url":"https://www.omim.org/entry/618739"},{"mim_id":"618640","title":"ZINC FINGER CCCH DOMAIN-CONTAINING PROTEIN 3; ZC3H3","url":"https://www.omim.org/entry/618640"},{"mim_id":"618626","title":"PHOSPHORYLATED C-TERMINAL DOMAIN-INTERACTING FACTOR 1; PCIF1","url":"https://www.omim.org/entry/618626"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Nucleoplasm","reliability":"Enhanced"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in single","driving_tissues":[{"tissue":"lymphoid 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for ~23 minutes.\",\n      \"method\": \"GFP-RPB1 knockin (endogenous tagging), FRAP/photobleaching, computational modeling\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — endogenous GFP knockin with quantitative live-cell imaging and rigorous computational modeling; multiple kinetic parameters established in a single well-controlled study\",\n      \"pmids\": [\"29632207\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"The CTD of Rpb1 (yeast) is phosphorylated at Ser7 in vivo; the basal factor TFIIH (Kin28/Cdk7) can phosphorylate Ser7 in vitro and is necessary for Ser7 phosphorylation in vivo. Deletion of the Ser5-phosphatase Rtr1 increases Ser5-P but not Ser7-P, distinguishing the two marks.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), in vitro kinase assay, genetic deletion of Rtr1\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro kinase assay combined with in vivo ChIP and genetic epistasis, two orthogonal methods in one study\",\n      \"pmids\": [\"19679665\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Mass-spectrometry analysis of a modified CTD (msCTD) showed that Ser5-P and Ser2-P are far more abundant than other CTD phosphorylations; msCTD co-purifying with capping enzyme was enriched for Ser5-P, while that bound to termination factor Rtt103 had higher Ser2-P, supporting a sparse 'CTD code'.\",\n      \"method\": \"Modified CTD mass spectrometry (msCTD), affinity purification, CTD kinase/phosphatase mutants\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — quantitative MS with engineered CTD, validated by kinase/phosphatase mutant strains and co-purification with known CTD-binding factors\",\n      \"pmids\": [\"26799764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"NMR solution structure of the human Set2 SRI domain revealed a three-helix bundle; NMR titration and Biacore binding assays showed the SRI domain binds preferentially to doubly (Ser2+Ser5)-phosphorylated CTD peptides of Rpb1 via helices 1 and 2, with five residues identified as critical by point mutagenesis.\",\n      \"method\": \"NMR structure determination, NMR titration, Biacore surface plasmon resonance, point mutagenesis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR structure plus orthogonal binding assay (SPR) plus mutagenesis in a single study, rigorous controls\",\n      \"pmids\": [\"16314571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The mammalian Elongin A–Elongin BC–Cul5/Rbx2 hetero-pentamer complex ubiquitylates Rpb1 in vitro; Elongin A-deficient cells show suppressed UV-induced Rpb1 ubiquitylation and proteasomal degradation. Elongin A preferentially interacts with Ser5-phosphorylated Rpb1 after UV irradiation.\",\n      \"method\": \"In vitro ubiquitylation assay (reconstituted complex), Elongin A knockdown/rescue, Co-IP (Elongin A with Rpb1)\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — reconstituted in vitro ubiquitylation plus cellular KD/rescue with two orthogonal readouts (ubiquitylation and degradation)\",\n      \"pmids\": [\"19037258\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Yeast Rpb9 (nonessential Pol II subunit) promotes UV-induced ubiquitylation and degradation of Rpb1 via its C-terminal Zn2 domain; the Zn2 domain is dispensable for transcription elongation and TCR but essential for Rpb1 degradation. Co-IP showed nearly full-length Rpb9 is needed for strong interaction with core Pol II.\",\n      \"method\": \"UV irradiation, domain-deletion mutants of Rpb9, Co-immunoprecipitation, 26S proteasome inhibitor experiments\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain-mapping with multiple deletion constructs, Co-IP, and proteasome inhibitor assay in a single study\",\n      \"pmids\": [\"17452455\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Old World alphavirus nsP2 proteins (Sindbis, Semliki Forest, Chikungunya) induce rapid ubiquitination and proteasomal degradation of Rpb1 to inhibit host transcription; this is independent of nsP2 protease activity but requires integrity of nsP2 helicase and SAM-dependent methyltransferase-like domains.\",\n      \"method\": \"Viral infection, nsP2 point mutants, proteasome inhibitor, ubiquitination assay, Western blot for Rpb1 levels\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain-disrupting point mutations in viral protein plus proteasome inhibitor and ubiquitination assay, multi-virus validation\",\n      \"pmids\": [\"22514352\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ARMC5, CUL3, and RBX1 form an active E3 ubiquitin ligase complex specific for RPB1; Armc5 deletion reduces RPB1 ubiquitination and increases RPB1 accumulation. Mutant ARMC5 (as found in PBMAH patients) shows altered binding to RPB1.\",\n      \"method\": \"Co-immunoprecipitation (ARMC5-CUL3-RBX1 complex), in vitro E3 ligase assay, Armc5 knockout mouse, RPB1 ubiquitination Western blot\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro E3 ligase assay with reconstituted complex plus knockout mouse model and patient mutation analysis\",\n      \"pmids\": [\"35687106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Rpb1 is sumoylated in yeast upon UV radiation or transcriptional impairment; E2 conjugase Ubc9 and E3 ligase Siz1 mediate this modification; K1487 in the acidic linker region of Rpb1 is the major sumoylation site. Rpb1 sumoylation restrains the DNA damage checkpoint (Rad53 phosphorylation) caused by transcription-blocking lesions.\",\n      \"method\": \"UV irradiation, SUMO pathway mutants (Ubc9, Siz1), site-directed mutagenesis (K1487), checkpoint kinase Rad53 phosphorylation assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — site-directed mutagenesis identifying K1487 site plus E2/E3 genetic analysis, but single lab\",\n      \"pmids\": [\"19384408\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In fission yeast, Bur1 (Cdk9) is the kinase responsible for phosphorylation of the Rpb1 linker in vivo; phosphorylation of the linker enhances binding of the Spt6 tandem SH2 domain. Inhibition of Cdk7/Kin28 blocked both Ser5-P and Ser7-P and also abolished Ser2-P, supporting obligatory sequential phosphorylation.\",\n      \"method\": \"Covalent kinase inhibitor (analog-sensitive alleles), ChIP, in vitro binding assay (Spt6-tSH2 domain)\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — selective kinase inhibition in vivo with multiple CTD phosphorylation readouts plus Spt6 binding validation\",\n      \"pmids\": [\"31085683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The CTD of Rpb1 can function when transferred to other Pol II subunits (Rpb4 or Rpb6) near the original CTD position and still support viability, phosphorylation, and factor recruitment; CTD fused to Rpb9 on the opposite face of Pol II fails to rescue. CTD fused to Rpb6 does not confer CTD functions on Pol I or Pol III.\",\n      \"method\": \"CTD domain-transfer genetic complementation, in vivo CTD phosphorylation assay, factor recruitment ChIP\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic rescue combined with phosphorylation and factor-recruitment readouts, multiple subunit fusions tested\",\n      \"pmids\": [\"24035501\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Sen1 interacts directly with the Ser2-phosphorylated CTD of Rpb1; the sen1-R302W mutation impairs this interaction, reduces Sen1 occupancy across noncoding genes, and disrupts transcription termination of noncoding RNAs. A handoff model is proposed where factors transfer from Ser5-P to Ser2-P CTD during transcription.\",\n      \"method\": \"Two-hybrid analysis, co-immunoprecipitation, chromatin immunoprecipitation (ChIP)\",\n      \"journal\": \"Eukaryotic cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal two-hybrid plus Co-IP plus ChIP occupancy analysis, single lab\",\n      \"pmids\": [\"22286094\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Fission yeast Cdk9 (P-TEFb) requires a C-terminal extension distinct from the catalytic domain for binding to capping enzyme Pcm1 and for Spt5 phosphorylation; this extension is dispensable for recognition of Ser7-pre-phosphorylated (primed) CTD substrates. On peptide substrates in vitro, Cdk9 prefers Ser7-phosphorylated CTD repeats over unmodified repeats.\",\n      \"method\": \"In vitro kinase assay on CTD peptides, domain-deletion mutants, chromatin immunoprecipitation, genetic suppression\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro kinase assay on defined substrates plus in vivo ChIP and genetic suppression with two orthogonal methods\",\n      \"pmids\": [\"22508988\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"In fission yeast, phosphorylation of Rpb1 CTD Ser2 by Lsk1 (Cdk12 orthologue) positively regulates H3K36 methylation but negatively regulates H3K4 methylation; Ser5 is required for H3K36me and H2B monoubiquitylation. Spt5 CTD Thr1 phosphorylation independently regulates H3K4me. Combinatorial CTD mutations potentiate histone modification defects.\",\n      \"method\": \"CTD phosphosite mutagenesis (Rpb1 and Spt5), histone modification analysis, kinase inactivation\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic CTD mutagenesis with multiple histone modification readouts, single lab\",\n      \"pmids\": [\"26275777\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Somatic missense mutations p.Gln403Lys or p.Leu438_His439del in POLR2A (encoding the catalytic subunit RPB1) are recurrently found in meningiomas; these mutant tumors show dysregulation of meningeal identity genes WNT6 and ZIC1/ZIC4, defining a mutually exclusive meningioma subgroup.\",\n      \"method\": \"Next-generation genomic sequencing of 775 meningiomas, transcriptional profiling of mutant tumors\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Strong — large-scale somatic mutation discovery with transcriptional profiling, but mechanism is correlative (no in vitro reconstitution of mutant enzyme activity)\",\n      \"pmids\": [\"27548314\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"De novo heterozygous POLR2A missense variants cause a neurodevelopmental syndrome with severe infantile-onset hypotonia via a dominant-negative mechanism: variants with mild structural effects produce malfunctioning Pol II and dominant-negative transcription inhibition, while loss-of-function variants (haploinsufficiency) yield milder phenotypes. Yeast functional assays confirmed impaired pol II activity.\",\n      \"method\": \"Structural evaluation of variants mapped to crystal structure, mass spectrometry, yeast (S. cerevisiae) functional assays, cell viability assays in HeLa cells\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — structural mapping, yeast functional assays, and cell viability assays across 11 variants in a single study using multiple orthogonal methods\",\n      \"pmids\": [\"31353023\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The SRI domain of human RECQ5 mediates interaction with RNAPII (Rpb1) and is required for suppressing spontaneous DNA double-strand breaks during replication; RECQ5 depletion causes accumulation of active RNAPII on chromatin and DSBs at RNAPII-transcribed loci, which are eliminated by transcription inhibition.\",\n      \"method\": \"RECQ5 siRNA depletion, SRI domain mutants, chromatin fractionation, DSB detection (γH2AX), transcription inhibitor rescue\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain-mapping plus rescue experiment with transcription inhibitor, multiple readouts, single lab\",\n      \"pmids\": [\"21402780\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"In Xenopus oocyte germinal vesicle, RPB1 exists in at least three distinct populations with different CTD phosphorylation states: nucleoplasmic (unphosphorylated CTD), lampbrush chromosome-associated (Ser2-P and Ser5-P), and Cajal body-associated (unphosphorylated and Ser5-P). GST-fused CTD repeat constructs (15–17 repeats) are rapidly and specifically targeted to Cajal bodies upon nuclear injection.\",\n      \"method\": \"Immunofluorescence with phospho-specific antibodies, nuclear injection of GST-CTD constructs, subcellular fractionation\",\n      \"journal\": \"Journal of structural biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — direct localization with functional CTD injection experiment, multiple phospho-specific antibodies, single lab\",\n      \"pmids\": [\"12490164\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Two-hybrid mapping of fission yeast Rpb1 showed that Rpb5 interacts with the conserved region H of Rpb1 (also found in RNA Pol I subunit Rpa190), while Rpb3 contacts the region H of Rpb2; these interactions define inter-subunit contacts within the Pol II complex.\",\n      \"method\": \"Yeast two-hybrid screening with Rpb1 and Rpb2 fragment libraries\",\n      \"journal\": \"Molecular & general genetics : MGG\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — two-hybrid mapping with multiple subunit fragments; widely reproduced in context of Pol II structure but single two-hybrid method\",\n      \"pmids\": [\"9738888\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"RPB1 mutations in S. cerevisiae that increase transcriptional slippage on homopolymeric runs were identified in residues throughout the catalytic center; biochemical characterization of isolated Pol II from these mutants confirmed elevated transcriptional slippage in vitro, demonstrating that Rpb1 active-site residues determine register maintenance during RNA synthesis.\",\n      \"method\": \"Genetic screen (6-AU sensitivity and slippage reporter), in vitro transcriptional slippage assay with purified Pol II\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro biochemical assay on purified enzyme from yeast mutants, confirming genetic result with direct enzymatic readout\",\n      \"pmids\": [\"23223234\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"RPB1 point mutations in the 'lid', 'rudder', and catalytic center (e.g., rpb1-N488D and rpb1-E1103G) cause opposite effects on intrinsic in vitro polymerization rate of RNAPII; rpb1-E1230K reduces RNAPII–TFIIS interaction. Synthetic genetic interactions with soh1, spt4, and dst1 were observed.\",\n      \"method\": \"6-AU sensitivity screen, in vitro transcription elongation assay, genetic epistasis (synthetic interactions)\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro polymerization assay on purified Pol II from mutants plus genetic epistasis, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"16510790\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"XAB2 depletion causes severe intron retention in POLR2A pre-mRNA, reducing POLR2A mRNA and protein levels, which impairs global transcription and induces cellular senescence via p53/p21 upregulation; XAB2 associates with spliceosome components (including SNW1 via TPR motifs 2–4 and 11) important for POLR2A expression; re-expression of POLR2A in XAB2-depleted cells rescues senescence.\",\n      \"method\": \"XAB2 siRNA knockdown, RNA-seq (splicing analysis), TMT-based quantitative proteomics, immunoprecipitation (XAB2-SNW1), POLR2A rescue experiment\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (RNA-seq, proteomics, Co-IP, rescue), single lab\",\n      \"pmids\": [\"31216022\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Triptolide causes RPB1 degradation and transcriptional inhibition through a CDK7-dependent mechanism: CDK7 phosphorylates Thr170 (activation) and a specific site on RPB1 (Ser1878); CDK7 inhibitor (BS-181) partially rescues RPB1 degradation and cell killing. XPB and p44 (TFIIH subunits) do not contribute to triptolide-driven RPB1 degradation.\",\n      \"method\": \"CDK7 inhibitor treatment, Western blot for RPB1 degradation, phospho-specific antibody for CDK7 Thr170 and RPB1 Ser1878, siRNA knockdown\",\n      \"journal\": \"Molecular cancer therapeutics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — pharmacological inhibitor plus phospho-site identification with rescue, but limited mutagenesis validation of Ser1878 site\",\n      \"pmids\": [\"27197304\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In Alzheimer disease hippocampal neurons, two phospho-isoforms of RPB1 mislocalize from the nucleus to the cytoplasm; the number of neurons with cytoplasmic RPB1 correlates with AT8-positive (pathologic tau) burden. In the rTg4510 tau mouse model, cytoplasmic mislocalization of Rpb1 increases in a tau- and age-dependent manner.\",\n      \"method\": \"Immunofluorescence on human AD and control tissue, rTg4510 transgenic mouse model (regulatable pathologic tau P301L), quantitative correlation analysis\",\n      \"journal\": \"Journal of neuropathology and experimental neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — direct localization experiment with causal tau model; correlation with tau burden and age-dependent effect in mouse model, but mechanistic link is correlative\",\n      \"pmids\": [\"33990839\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"POLR2A interacts with CREB1 and regulates assembly of CREB1 on regulatory elements of osteoclast target genes; osteoclast-specific deletion of POLR2A blocks bone resorption in vivo, and POLR2A inhibition suppresses estrogen deficiency-induced bone resorption.\",\n      \"method\": \"Co-immunoprecipitation (POLR2A–CREB1), osteoclast-specific conditional Polr2a knockout mice, ChIP for CREB1 at target gene regulatory elements, in vitro osteoclastogenesis assay\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ChIP plus conditional KO mouse model, single lab\",\n      \"pmids\": [\"33595106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP10 deubiquitinase directly interacts with POLR2A, removes K48- and K63-linked ubiquitin chains from POLR2A through its deubiquitinase activity, and prevents ubiquitin-mediated POLR2A degradation; stabilized POLR2A then transcriptionally activates SLC7A11 to suppress ferroptosis in head and neck squamous cell carcinoma.\",\n      \"method\": \"Co-immunoprecipitation (USP10–POLR2A), in vitro deubiquitination assay, USP10 gene depletion and antagonist, ChIP for POLR2A at SLC7A11 promoter\",\n      \"journal\": \"Advanced science (Weinheim, Baden-Wurttemberg, Germany)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, in vitro deubiquitination assay, and ChIP, single lab\",\n      \"pmids\": [\"40605431\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Rtr1 (a known Pol II CTD phosphatase) cooperates with Gpn3 and Npa3 to assemble the two largest RNAPII subunits (Rpb1–Rpb2); RTR1 deletion causes cytoplasmic clumping of RNAPII subunits; multicopy RTR1 suppresses cytoplasmic clumping in gpn3-9 mutants. The phosphatase catalytic activity of Rtr1 is dispensable for this assembly function.\",\n      \"method\": \"Genetic suppressor screen (multicopy RTR1), cytoplasmic clump assay (fluorescence), catalytically inactive RTR1 mutant\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — genetic suppression with catalytic separation-of-function mutant and localization assay, single lab\",\n      \"pmids\": [\"36190433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"In mouse oocytes, phospho-RPB1 (Ser2) localizes to spindle poles and co-localizes with MTOC components (pericentrin and γ-tubulin) after meiotic resumption; phospho-RPB1 (Ser5 and Ser7) assembles as filamentous aggregates co-localizing with microtubules throughout the spindle and responds to nocodazole/taxol similarly to microtubules. Ser2-P and Ser5-P are also concentrated at centromere areas on chromosomes.\",\n      \"method\": \"Immunofluorescence with phospho-specific antibodies, spindle-disturbing drug treatments (nocodazole, taxol), co-localization with MTOC markers\",\n      \"journal\": \"The Journal of reproduction and development\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — localization study without functional consequence demonstrated; co-localization is suggestive but no loss-of-function readout for the meiotic role\",\n      \"pmids\": [\"26346254\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Disrupting the Spt6-tSH2:Rpb1 linker interface affects transcription start site selection at specific gene subsets, reduces splicing efficiency, impairs chromatin-mediated repression, and diminishes +1 nucleosome maintenance at ribosomal protein genes; the interaction modulates Spt6 recruitment and elongation complex coordination.\",\n      \"method\": \"Interface-disrupting mutations in Spt6-tSH2 domain, RNA-seq (TSS analysis, splicing), ChIP (Spt6 occupancy), MNase-seq (nucleosome positioning)\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal genomic methods with defined interface mutations, single lab\",\n      \"pmids\": [\"34967414\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Rpb1 foot-region mutations in yeast alter assembly of Rpb6 and the Rpb4/7 dimer, activate an environmental stress response (ESR) at permissive temperature, and this ESR depends on Rpb4-mediated post-transcriptional mRNA stability (mRNA imprinting) rather than transcription alone.\",\n      \"method\": \"RPB1 foot-region mutant analysis, global transcriptional analysis, mRNA stability assay, genetic analysis with Rpb4\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide transcription and mRNA decay analysis combined with genetic dependence on Rpb4, single lab\",\n      \"pmids\": [\"27001033\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"OROV NSs protein co-localizes with nucleophosmin 1 (NPM1) and promotes proteasomal degradation of hyperphosphorylated RNAP II (RPB1), reducing Ser2-P and Ser5-P CTD phosphorylation and suppressing nascent RNA synthesis; RPB1 loss is rescued by proteasome inhibitor MG132.\",\n      \"method\": \"OROV infection and NSs expression, proteasome inhibitor (MG132) rescue, Western blot for RPB1 and CTD phospho-isoforms, nascent RNA quantification\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Weak — single lab, single published study; MG132 rescue is informative but mechanistic details of NSs–RPB1 interaction not deeply characterized\",\n      \"pmids\": [\"40928251\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"E3 ligase LMO7 is recruited to POLR2A and promotes its ubiquitination and proteasomal degradation during cellular senescence; LMO7 depletion abolishes POLR2A ubiquitination and reduction in H2O2-induced senescent cells. POLR2A knockdown induces senescence through MDM4-mediated p53/p21 pathway activation.\",\n      \"method\": \"Co-immunoprecipitation (LMO7–POLR2A), ubiquitination assay, LMO7/POLR2A siRNA knockdown, CRISPRa re-activation, RNA-seq\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP plus ubiquitination assay plus CRISPRa rescue; multiple orthogonal methods but single lab, recently published\",\n      \"pmids\": [\"41896199\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Nuclear PD-L1 (following IFN-γ-induced HDAC2-mediated deacetylation and nuclear translocation) physically binds POLR2A and forms a transcriptional complex that directly activates LY6E expression, promoting TNBC lung metastasis independently of immune checkpoint function.\",\n      \"method\": \"CRISPR/Cas9 PD-L1 knockout, Co-immunoprecipitation (PD-L1–POLR2A), ChIP-seq (PD-L1 and POLR2A at LY6E locus), RNA-seq\",\n      \"journal\": \"Breast cancer research : BCR\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and ChIP-seq with CRISPR KO rescue, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"41388312\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Sequence-specific DNA double-strand breaks (DSBs) activate P-TEFb, triggering hyperphosphorylation of the Rpb1 CTD and subsequent p53-dependent transcriptional activation leading to cell cycle arrest.\",\n      \"method\": \"Inducible restriction enzyme DSB system, P-TEFb activity assay, Rpb1-CTD hyperphosphorylation Western blot, p53 target gene induction\",\n      \"journal\": \"Mutation research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, P-TEFb activity inferred from CTD phosphorylation state; no direct in vitro reconstitution of the P-TEFb–Rpb1 relationship under DSB conditions\",\n      \"pmids\": [\"23906511\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Leveraging ERLIC/HILIC chromatography with engineered msCTD, MS analysis confirmed that Ser5-P and Ser2-P are the dominant endogenous CTD phosphoisoforms in yeast, consistent with a simple 'CTD code', and demonstrated that these marks occur throughout CTD length.\",\n      \"method\": \"Mass spectrometry (HILIC/ERLIC LC-MS/MS) of engineered yeast msCTD\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — quantitative mass spectrometry on modified CTD; technically rigorous but preprint and replicates findings already established by peer-reviewed msCTD work\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"UV-induced RPB1 degradation occurs in trans and is controlled by NER activity regardless of how the DNA lesion is recognized (by stalled RNAPII or GG-NER factors XPE/XPC); absence of any core NER factor enhances RPB1 degradation, and damage-induced degradation depends on Cullin-RING ubiquitin ligases and is not restricted to actively transcribing or phosphorylated RPB1 molecules.\",\n      \"method\": \"NER factor mutants (TC-NER and GG-NER), Cullin-RING inhibitor, UV irradiation, Western blot for RPB1 degradation\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple NER mutants with pharmacological inhibitor, novel trans mechanism, but preprint only\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"STK19 is an integral component of the Pol II–TC-NER complex; cryo-EM shows STK19 bridges CSA with UVSSA, RPB1, and downstream DNA; STK19 stimulates CRL4CSA E3 ligase activity resulting in efficient Pol II (RPB1 K1268) ubiquitylation and correct UVSSA/TFIIH binding for TC-NER.\",\n      \"method\": \"Cryo-EM structure of TC-NER complex, live-cell imaging, Co-immunoprecipitation, CRL4CSA ubiquitination assay\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — cryo-EM structure plus ubiquitination assay plus live-cell imaging; rigorous multi-method study but preprint\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"STK19 joins the TC-NER complex by binding CSA and the RPB1 subunit of Pol II (1.9 Å cryo-EM structure); AlphaFold modeling and mutational disruption of STK19–XPD interface impairs cell-free TC-NER, suggesting STK19 positions TFIIH ahead of Pol II for lesion verification.\",\n      \"method\": \"1.9 Å cryo-EM, in vitro TC-NER reconstitution in frog egg extract, interface mutant disruption, AlphaFold modeling\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — near-atomic cryo-EM with cell-free functional reconstitution; preprint, but independently corroborated by companion study (Ramadhin et al.)\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Loss of Pol II protein (Rpb1 specifically) — but not loss of transcriptional activity — activates a specific apoptotic pathway termed PDAR (Pol II Degradation-dependent Apoptotic Response); expression of a transcriptionally inactive Rpb1 rescues viability after Pol II loss.\",\n      \"method\": \"Rpb1 catalytic-dead mutant rescue experiment, functional genomics (PDAR genetic dependencies), Pol II depletion\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — catalytic separation-of-function rescue combined with functional genomics screen; preprint, single lab\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CDK11 phosphorylates the Rpb1 linker domain (analogous to yeast Bur1) and the hSpt5 repeat region; CDK11 inhibition reduces active Pol II at TSS and gene bodies. CDK11 is also required for phosphorylation and activation of CDK12, which drives Pol II elongation.\",\n      \"method\": \"CDK11 inhibition (selective inhibitor), ChIP-seq for active Pol II, in vitro kinase assay, CDK12 phosphorylation Western blot\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — selective kinase inhibition plus in vitro kinase assay, establishing CDK11→CDK12 kinase cascade with multiple readouts; preprint\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"IWS1 interacts with Pol II subunits RPB1 (via the RPB1 jaw domain, dependent on downstream DNA binding), RPB2, and RPB5, as well as elongation factors DSIF, SPT6, and ELOF1, as revealed by cryo-EM mapping of short linear motifs (SLiMs) in the intrinsically disordered C-terminal region of IWS1. IWS1 protects the elongation complex from RECQL5 inhibition.\",\n      \"method\": \"Cryo-EM of IWS1–Pol II elongation complex, functional SLiM mutagenesis, in vitro transcription stimulation assay\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cryo-EM structure plus functional mutagenesis and in vitro transcription assay; preprint, novel mechanistic findings not yet in peer-reviewed form\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"RECQ5 attenuates RNAPII transcription elongation via two mechanisms: (1) at atomic level, its brake helix acts as a doorstop controlling Pol II translocation along DNA; (2) at mesoscale, RECQ5 forms a condensate scaffold integrating hyperphosphorylated Pol II elongation complexes via site-specific interactions with CTD (RPB1).\",\n      \"method\": \"Biochemical reconstitution, cryo-EM, cryotomography, coarse-grained simulations\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cryo-EM and reconstitution with multi-scale approach; preprint, novel structural mechanism\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Minnelide (triptolide pro-drug) acts through xeroderma pigmentosum type B (XPB) to alter RPB1 phosphorylation and subsequent proteasomal degradation, inducing apoptosis of CIC::DUX4 sarcoma cells in vitro and in vivo.\",\n      \"method\": \"Transcription inhibitor screen, RPB1 phosphorylation and degradation Western blot, in vivo xenograft and GEMM models\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — preprint, RPB1 phosphorylation and degradation measured but XPB–RPB1 mechanistic link is inferred rather than directly reconstituted\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"The full-length mouse RPB1 can functionally substitute for the yeast S. cerevisiae RPB1 in vivo, supporting viability when expressed from the yeast promoter via homologous recombination, demonstrating structural and functional conservation of RPB1 across mammals and yeast.\",\n      \"method\": \"Homologous recombination gene replacement, haploid viability assay, Northern analysis\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct in vivo genetic complementation across species, single study\",\n      \"pmids\": [\"9524248\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"POLR2A/RPB1 is the catalytic largest subunit of RNA polymerase II whose C-terminal domain (CTD) undergoes dynamic, stage-specific phosphorylation (primarily at Ser2, Ser5, and Ser7 of the YSPTSPS heptad repeats) by CDK7/TFIIH (Ser5, Ser7), CDK9/Bur1 (Rpb1 linker, Spt5), and CDK12/Ctk1 (Ser2), creating a 'CTD code' that recruits capping enzymes, splicing factors, histone-modifying enzymes (Set2 SRI domain via Ser2+Ser5-P), and termination factors; the CTD can function when transferred to nearby Pol II subunits (Rpb4, Rpb6) but not to distant ones, showing spatial but not strict physical linkage to the catalytic core is required; in response to DNA damage (UV or transcription-blocking lesions), RPB1 is ubiquitylated by multiple E3 ligase complexes including Elongin A–BC–Cul5/Rbx2 (recognizing Ser5-P RPB1), ARMC5–CUL3–RBX1, and CRL4CSA (at K1268 in TC-NER), and degraded by the 26S proteasome in a process facilitated by Rpb9 and regulated in trans by NER completion; RPB1 is additionally sumoylated at K1487 by Ubc9/Siz1 to restrain DNA damage checkpoint signaling; viral proteins (alphavirus nsP2, OROV NSs) hijack RPB1 ubiquitination to suppress host transcription; dominant-negative missense variants of POLR2A cause a neurodevelopmental syndrome by producing malfunctioning Pol II that impairs global transcription, whereas haploinsufficiency has milder effects; loss of the RPB1 protein itself (independent of transcriptional activity) triggers a specific apoptotic program (PDAR); and live-cell imaging reveals that promoter-paused Pol II has unexpectedly high turnover (~42 sec) compared to elongating Pol II (~23 min).\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"POLR2A/RPB1 is the catalytic largest subunit of RNA polymerase II, providing the active-site residues that maintain transcriptional register during RNA synthesis and whose function is conserved deeply enough that mouse RPB1 substitutes for yeast Rpb1 in vivo [#19, #43]. Active-site mutations in the lid, rudder, and catalytic center alter intrinsic polymerization rates and TFIIS interaction, and mutations across the catalytic center elevate transcriptional slippage on homopolymeric runs [#19, #20]. RPB1 activity is orchestrated through stage-specific phosphorylation of its C-terminal domain (CTD) heptad repeats, in which Ser5-P and Ser2-P are the dominant marks deposited and removed by dedicated kinases and phosphatases to form a sparse 'CTD code' [#2]: TFIIH/Kin28(CDK7) establishes Ser5-P and Ser7-P, with Ser7-P priming subsequent events, while CDK9/Bur1 and CDK11 phosphorylate the Rpb1 linker and Spt5, and CDK12 orthologues deposit Ser2-P [#1, #9, #12, #39]. These marks recruit and hand off effectors—capping enzyme via Ser5-P, the Set2 SRI domain via doubly Ser2+Ser5-phosphorylated CTD to direct H3K36 methylation, the Spt6 tandem-SH2 domain to the phosphorylated linker, and termination factors Sen1/Rtt103 via Ser2-P [#2, #3, #11, #13, #28]. The CTD remains functional when relocated to neighboring Pol II subunits (Rpb4, Rpb6) but not to distant ones, indicating spatial rather than strict physical linkage to the core is required [#10]. In response to UV and transcription-blocking lesions, RPB1 is ubiquitylated by multiple Cullin-RING E3 complexes—Elongin A–BC–Cul5/Rbx2 recognizing Ser5-P RPB1, ARMC5–CUL3–RBX1, and CRL4CSA targeting K1268 within the Pol II–TC-NER complex—and degraded by the 26S proteasome in a process facilitated by Rpb9 and controlled in trans by NER completion [#4, #5, #7, #35, #36, #37]; this degradation is opposed by the deubiquitinase USP10 [#25] and is hijacked by viral proteins (alphavirus nsP2, OROV NSs) to suppress host transcription [#6, #30]. RPB1 is additionally sumoylated at K1487 by Ubc9/Siz1 to restrain DNA-damage checkpoint signaling [#8]. De novo heterozygous POLR2A missense variants cause a neurodevelopmental syndrome through a dominant-negative mechanism that yields malfunctioning Pol II, whereas haploinsufficiency produces milder effects [#15], and recurrent somatic POLR2A mutations define a meningioma subgroup with dysregulated meningeal identity genes [#14].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Establishing that the mammalian and yeast catalytic subunit are functionally interchangeable validated yeast as a faithful model for human RPB1 mechanism and confirmed deep conservation.\",\n      \"evidence\": \"Homologous-recombination gene replacement and haploid viability assay with full-length mouse RPB1 in S. cerevisiae\",\n      \"pmids\": [\"9524248\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not address conservation of CTD-dependent regulatory functions\", \"No quantitative comparison of transcriptional output\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Mapping inter-subunit contacts addressed how RPB1 is held within the Pol II assembly, defining the region H interaction with Rpb5.\",\n      \"evidence\": \"Yeast two-hybrid mapping with Rpb1 and Rpb2 fragment libraries\",\n      \"pmids\": [\"9738888\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single two-hybrid method without structural confirmation\", \"Does not establish functional consequence of contacts\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Pinpointing active-site residues whose mutation alters intrinsic polymerization rate and TFIIS interaction established that RPB1 catalytic geometry directly governs elongation behavior.\",\n      \"evidence\": \"6-AU sensitivity screen, in vitro transcription elongation assay on purified Pol II mutants, genetic epistasis\",\n      \"pmids\": [\"16510790\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Catalytic mechanism inferred from rate effects, not atomic structure\", \"Single-lab genetic interaction set\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Structurally defining how the Set2 SRI domain reads doubly Ser2+Ser5-phosphorylated CTD answered how a specific histone-modifying enzyme is recruited by the CTD code.\",\n      \"evidence\": \"NMR structure, NMR titration, SPR binding, point mutagenesis of SRI domain\",\n      \"pmids\": [\"16314571\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Binding measured on peptides, not full elongation complex\", \"Does not establish in vivo kinetics of recruitment\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identifying the Rpb9 Zn2 domain as required for damage-induced Rpb1 degradation but dispensable for elongation separated the polymerase's catalytic role from its turnover.\",\n      \"evidence\": \"UV irradiation, Rpb9 domain-deletion mutants, Co-IP, proteasome inhibitor\",\n      \"pmids\": [\"17452455\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which Rpb9 promotes ubiquitylation unresolved\", \"Single-organism (yeast) study\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Reconstituting the Elongin A–BC–Cul5/Rbx2 ligase that recognizes Ser5-P RPB1 identified a defined E3 machinery for UV-induced RPB1 destruction.\",\n      \"evidence\": \"In vitro ubiquitylation with reconstituted complex, Elongin A KD/rescue, Co-IP\",\n      \"pmids\": [\"19037258\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ubiquitin chain linkage type not characterized\", \"Redundancy with other ligases not resolved at this stage\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Demonstrating Ser7 phosphorylation in vivo by TFIIH and distinguishing it from Ser5 expanded the CTD code beyond Ser2/Ser5.\",\n      \"evidence\": \"ChIP, in vitro kinase assay, Rtr1 phosphatase deletion\",\n      \"pmids\": [\"19679665\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional readers of Ser7-P not identified here\", \"Yeast-specific phosphatase logic\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identifying K1487 sumoylation by Ubc9/Siz1 that restrains the DNA-damage checkpoint defined a SUMO-based brake on checkpoint signaling at transcription-blocking lesions.\",\n      \"evidence\": \"UV irradiation, SUMO pathway mutants, K1487 site-directed mutagenesis, Rad53 phosphorylation assay\",\n      \"pmids\": [\"19384408\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"SUMO readers downstream of K1487 unknown\", \"Single-lab yeast study\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defining Sen1 binding to Ser2-P CTD and a Ser5-to-Ser2 handoff model addressed how the CTD code temporally directs termination of noncoding transcription.\",\n      \"evidence\": \"Two-hybrid, Co-IP, ChIP with sen1-R302W mutant\",\n      \"pmids\": [\"22286094\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Handoff model not directly visualized\", \"Single-lab correlative occupancy data\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showing that Cdk9 prefers Ser7-primed CTD and requires a C-terminal extension for capping-enzyme/Spt5 engagement clarified the sequential, substrate-primed logic of CTD phosphorylation.\",\n      \"evidence\": \"In vitro kinase assay on CTD peptides, Cdk9 domain mutants, ChIP, genetic suppression\",\n      \"pmids\": [\"22508988\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not establish in vivo order quantitatively across genes\", \"Fission-yeast specific\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrating that alphavirus nsP2 triggers RPB1 ubiquitination/degradation independently of its protease showed pathogens exploit RPB1 turnover to shut down host transcription.\",\n      \"evidence\": \"Viral infection, nsP2 domain point mutants, proteasome inhibitor, ubiquitination Western blot\",\n      \"pmids\": [\"22514352\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Host E3 ligase recruited by nsP2 not identified\", \"Direct nsP2–RPB1 interaction not mapped\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showing the CTD remains functional when fused to neighboring subunits but not distant ones established that spatial proximity, not covalent linkage to the catalytic subunit, is what the CTD requires.\",\n      \"evidence\": \"CTD domain-transfer complementation, in vivo phosphorylation, factor-recruitment ChIP\",\n      \"pmids\": [\"24035501\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not explain why Pol I/III cannot adopt CTD function\", \"Geometric constraints quantified only by subunit choice\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Confirming that catalytic-center mutations elevate transcriptional slippage established RPB1 active-site residues as direct determinants of register maintenance.\",\n      \"evidence\": \"Genetic slippage screen plus in vitro slippage assay on purified mutant Pol II\",\n      \"pmids\": [\"23223234\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of register slippage not resolved\", \"Yeast-only system\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Linking Ser2/Ser5 CTD marks to opposing effects on H3K36 versus H3K4 methylation connected the CTD code to combinatorial chromatin modification during elongation.\",\n      \"evidence\": \"Rpb1 and Spt5 CTD phosphosite mutagenesis, histone modification analysis, kinase inactivation\",\n      \"pmids\": [\"26275777\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of negative H3K4 regulation unclear\", \"Single-lab fission-yeast study\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Quantitative msCTD mass spectrometry established that Ser5-P and Ser2-P dominate and partition with specific effectors, providing direct evidence for a sparse rather than combinatorially dense CTD code.\",\n      \"evidence\": \"Engineered CTD mass spectrometry, affinity purification with capping enzyme and Rtt103, kinase/phosphatase mutants\",\n      \"pmids\": [\"26799764\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Spatial distribution along genes not resolved\", \"Low-abundance marks may have undetected roles\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Recurrent somatic POLR2A missense mutations defining a meningioma subgroup implicated RPB1 dysfunction in tumor identity-gene dysregulation.\",\n      \"evidence\": \"NGS of 775 meningiomas plus transcriptional profiling of mutant tumors\",\n      \"pmids\": [\"27548314\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vitro reconstitution of mutant enzyme activity\", \"Mechanistic link to WNT6/ZIC1 dysregulation is correlative\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstrating that triptolide drives CDK7-dependent RPB1 phosphorylation (Ser1878) and degradation defined a pharmacological route to RPB1 destabilization.\",\n      \"evidence\": \"CDK7 inhibitor, phospho-specific antibodies for CDK7 Thr170 and RPB1 Ser1878, siRNA\",\n      \"pmids\": [\"27197304\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ser1878 site validated without mutagenesis\", \"E3 ligase mediating degradation not identified\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Live-cell FRAP of endogenous GFP-RPB1 resolved discrete kinetic Pol II populations, revealing that promoter-paused Pol II turns over far faster (~42 s) than elongating Pol II (~23 min).\",\n      \"evidence\": \"GFP-RPB1 knockin, FRAP, computational kinetic modeling\",\n      \"pmids\": [\"29632207\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of high pause turnover (premature termination) inferred\", \"Population assignments depend on model assumptions\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Showing dominant-negative POLR2A missense variants cause a neurodevelopmental syndrome while LOF variants are milder defined the genotype–phenotype logic of human Pol II disease.\",\n      \"evidence\": \"Structural mapping of 11 variants, yeast functional assays, HeLa viability assays\",\n      \"pmids\": [\"31353023\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Gene-specific transcriptional consequences in patient neurons not mapped\", \"Mechanism of dominant-negative interference at molecular level not resolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identifying that Bur1/Cdk9 phosphorylates the Rpb1 linker to recruit the Spt6 tandem-SH2 domain, with Kin28 inhibition abolishing downstream marks, established obligatory sequential CTD/linker phosphorylation feeding elongation factor recruitment.\",\n      \"evidence\": \"Analog-sensitive kinase inhibition, ChIP, in vitro Spt6-tSH2 binding\",\n      \"pmids\": [\"31085683\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative dependency of Ser2-P on prior marks not fully dissected\", \"Fission-yeast specific\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Linking XAB2-dependent splicing of POLR2A pre-mRNA to senescence showed that RPB1 abundance is post-transcriptionally controlled and that its loss engages p53/p21.\",\n      \"evidence\": \"XAB2 siRNA, RNA-seq splicing analysis, TMT proteomics, XAB2-SNW1 Co-IP, POLR2A rescue\",\n      \"pmids\": [\"31216022\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct splicing mechanism on POLR2A introns not resolved\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identifying POLR2A interaction with CREB1 to assemble on osteoclast target genes, and PD-L1 to activate LY6E, extended RPB1 roles to specific transcription-factor–directed programs in physiology and metastasis.\",\n      \"evidence\": \"Co-IP, ChIP/ChIP-seq, conditional Polr2a knockout mice, CRISPR KO (PD-L1)\",\n      \"pmids\": [\"33595106\", \"41388312\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether these are general or gene-specific recruitment events unclear\", \"Single-lab studies\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defining the ARMC5–CUL3–RBX1 complex as an RPB1-specific E3 ligase added a CUL3-based pathway controlling RPB1 abundance, with disease relevance via PBMAH mutations.\",\n      \"evidence\": \"Co-IP, in vitro E3 ligase assay, Armc5 knockout mouse, RPB1 ubiquitination Western blot\",\n      \"pmids\": [\"35687106\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubiquitin linkage and degron on RPB1 not defined\", \"Relationship to UV-induced ligases unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Characterizing the Spt6-tSH2:Rpb1 linker interface in vivo showed this contact coordinates TSS selection, splicing, repression, and +1 nucleosome maintenance.\",\n      \"evidence\": \"Interface-disrupting mutations, RNA-seq, Spt6 ChIP, MNase-seq\",\n      \"pmids\": [\"34967414\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct causal chain from interface to each phenotype not separated\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identifying USP10 as a deubiquitinase that stabilizes POLR2A defined an opposing arm to RPB1 ubiquitination with downstream control of SLC7A11 and ferroptosis.\",\n      \"evidence\": \"Co-IP, in vitro deubiquitination assay, USP10 depletion/antagonist, POLR2A ChIP at SLC7A11\",\n      \"pmids\": [\"40605431\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Which E3-deposited chains USP10 antagonizes in vivo unclear\", \"Single-lab cancer-context study\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Showing OROV NSs promotes proteasomal degradation of hyperphosphorylated RPB1 added a second viral strategy converging on RPB1 turnover to suppress host transcription.\",\n      \"evidence\": \"OROV infection/NSs expression, MG132 rescue, CTD phospho-isoform Western blot, nascent RNA quantification\",\n      \"pmids\": [\"40928251\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"NSs–RPB1 interaction not directly mapped\", \"Host E3 ligase unidentified\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the multiple RPB1 ubiquitination pathways (Elongin A, ARMC5-CUL3, CRL4CSA, LMO7), deubiquitination by USP10, sumoylation, and the PDAR apoptotic response are integrated to set RPB1 abundance and cell fate across stress and disease contexts remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model coordinating competing E3 ligases and USP10\", \"Degron and chain-linkage specificity for each pathway not defined\", \"Trigger that commits cells to PDAR versus survival unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [19, 20]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [19, 20]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [14, 24, 32]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005654\", \"supporting_discovery_ids\": [17]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [17, 23]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [26]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [2, 19, 20]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [4, 8, 35, 36]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [2, 11, 21]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [14, 15]}\n    ],\n    \"complexes\": [\n      \"RNA polymerase II\",\n      \"Pol II–TC-NER complex\"\n    ],\n    \"partners\": [\n      \"SETD2\",\n      \"SPT6\",\n      \"SEN1\",\n      \"ELOA\",\n      \"ARMC5\",\n      \"USP10\",\n      \"RECQ5\",\n      \"IWS1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}