{"gene":"POLR2I","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":1991,"finding":"RPB9 is a non-essential subunit of RNA polymerase II required for normal cell growth over a wide temperature range; deletion produces heat- and cold-sensitive cells but does not abolish mRNA synthesis.","method":"Gene deletion/disruption, genetic growth assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with defined growth phenotype, single lab but foundational characterization","pmids":["1918023"],"is_preprint":false},{"year":1995,"finding":"RPB9 is required for accurate transcription start site selection by RNA polymerase II; deletion causes upstream shifts to new or previously minor start sites at multiple promoters in vivo and in vitro, and addition of recombinant RPB9 fully rescues the initiation defect in vitro.","method":"RPB9 gene deletion, in vitro transcription reconstitution, recombinant protein add-back, site-directed mutagenesis of metal-binding domain","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution with recombinant protein, mutagenesis, multiple promoters in vivo and in vitro, replicated in subsequent studies","pmids":["7883169"],"is_preprint":false},{"year":1996,"finding":"RPB9 (SSU73) functionally interacts with TFIIB in transcription start site selection; the ssu73-1 allele (nonsense at codon 107, truncating the C-terminal 16 aa) suppresses both the growth defect and downstream start site shift caused by the sua7-1 TFIIB mutation, establishing a functional interaction between Rpb9 and TFIIB during preinitiation complex formation.","method":"Genetic suppressor screen, allele isolation and sequencing, in vivo start site analysis","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with defined alleles, single lab, start site phenotype confirmed in vivo","pmids":["8692696"],"is_preprint":false},{"year":1997,"finding":"RPB9 promotes transcription elongation through DNA arrest sites and is required for TFIIS-mediated read-through; RNA polymerase II lacking RPB9 (pol IIDelta9) elongates more efficiently through pause/arrest sequences but cannot be reactivated by TFIIS; addition of recombinant RPB9 to pol IIDelta9 restores wild-type elongation properties.","method":"In vitro transcription elongation assay, biochemical reconstitution with recombinant RPB9, TFIIS stimulation assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution with purified recombinant protein, multiple orthogonal in vitro assays, transcript cleavage uncoupling experiment","pmids":["9169440"],"is_preprint":false},{"year":2000,"finding":"The C-terminal zinc ribbon acidic loop of RPB9 is critical for transcription elongation activity; the conserved linker region (residues 89-95, DPTLPR) mediates interaction with RNA polymerase II; individual zinc ribbon domains in isolation cannot stimulate transcription by pol IIDelta9.","method":"Site-directed mutagenesis, deletion analysis, in vitro transcription elongation assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic mutagenesis with functional in vitro assay, multiple mutants tested, defines interaction domain","pmids":["10644677"],"is_preprint":false},{"year":2000,"finding":"RPB9 has a synthetic phenotype with the TFIIS gene (DST1) for 6-azauracil sensitivity; overexpression of TFIIS partially suppresses the 6-AU sensitivity of rpb9Δ cells; the N-terminal zinc ribbon restores wild-type initiation start sites but does not complement elongation-specific growth defects, indicating separable functions of the two domains.","method":"Genetic epistasis (double deletion), drug sensitivity assay, high-copy suppression, domain complementation in vivo, genome-wide transcription profiling","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with domain dissection in vivo, multiple methods, single lab","pmids":["10938084"],"is_preprint":false},{"year":2002,"finding":"RPB9 mediates a subpathway of transcription-coupled DNA repair (TCR) in S. cerevisiae that is independent of Rad26 and operates more effectively in the coding region; simultaneous deletion of RPB9 and RAD26 completely abolishes TCR, indicating these are the only two TCR subpathways in RNA Pol II-transcribed genes; RPB4 suppresses the RPB9-mediated TCR subpathway.","method":"Gene deletion (single and double mutants), UV-induced DNA damage repair assay (strand-specific), genetic epistasis","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean double-KO with complete abolition of TCR, strand-specific repair assay, replicated in subsequent domain-mapping studies","pmids":["12411509"],"is_preprint":false},{"year":2002,"finding":"Rpb9 physically interacts with Tfa1, the largest subunit of TFIIE, via a two-hybrid interaction; co-immunoprecipitation of TFIIE with RNA polymerase II is strongly reduced in rpb9Δ, indicating Rpb9 contributes to TFIIE recruitment to the polymerase; rpb9 mutations are synthetically lethal with loss of Elongator or SAGA histone acetyltransferase activity.","method":"Yeast two-hybrid, co-immunoprecipitation, synthetic lethality analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — two-hybrid plus co-IP for TFIIE interaction, synthetic lethality for acetyltransferase link, single lab","pmids":["11779853"],"is_preprint":false},{"year":2003,"finding":"RNA polymerase II lacking Rpb9 has an impaired interaction with TFIIF (Tfg1-Tfg2 complex), and this impaired interaction is associated with upstream shifts in mRNA 5'-end positions in reconstituted transcription assays with purified general transcription factors.","method":"Reconstituted in vitro transcription with purified factors, gel mobility shift assay, recombinant holo-TFIIF production","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — reconstituted transcription with highly purified components, gel shift for direct interaction, single lab","pmids":["14522989"],"is_preprint":false},{"year":2006,"finding":"The Zn1 and linker domains of Rpb9 are essential for both transcription elongation and TCR functions; the Zn2 domain is dispensable for these functions; impairment of transcription elongation completely abolishes Rpb9-mediated TCR, suggesting the elongation function of Rpb9 is required for TCR.","method":"Domain deletion mutagenesis, UV repair assay (strand-specific), transcription elongation assay in vivo","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic domain dissection with multiple functional readouts, single lab","pmids":["17030604"],"is_preprint":false},{"year":2006,"finding":"RPB9-mediated TCR is strictly transcription-coupled and requires both TATA and UAS sequences; its efficiency depends on the SAGA complex; Rad26-mediated repair operates differently and can function independently of transcription when transcription levels are too low.","method":"Promoter element deletion/mutation, strand-specific UV repair assay, genetic analysis of SAGA complex","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple promoter mutants with quantitative repair assays, single lab","pmids":["17023424"],"is_preprint":false},{"year":2006,"finding":"Deletion of RPB9 in yeast results in error-prone transcription in vivo, as measured by increased read-through of a nonsense allele (can1-100); rpb9Δ strains have increased steady-state levels of can1-100 mRNA and sequence analysis of cDNAs confirmed significantly increased transcriptional substitutions and insertions.","method":"In vivo transcription fidelity assay (canavanine sensitivity), cDNA sequencing, Northern blot","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo functional assay with direct cDNA sequencing confirmation, single lab","pmids":["16492753"],"is_preprint":false},{"year":2007,"finding":"In response to UV radiation, Rpb9 promotes ubiquitylation and degradation of Rpb1 (the largest Pol II subunit) via the 26S proteasome; the Zn2 domain is essential for this function while Zn1 and linker play subsidiary roles; co-immunoprecipitation shows that near-full-length Rpb9 is required for strong interaction with core Pol II.","method":"UV irradiation, western blot for ubiquitylation and degradation, domain deletion mutagenesis, co-immunoprecipitation, proteasome inhibitor treatment","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus functional degradation assay with domain dissection, single lab","pmids":["17452455"],"is_preprint":false},{"year":2009,"finding":"RPB9 controls transcription fidelity by delaying NTP sequestration in the RNA polymerase II active center; RPB9 deletion promotes premature closure of the trigger loop on incoming NTP prior to phosphodiester bond formation, enhancing NTP misincorporation and mismatch extension; this is mediated by interaction between the C-terminal domain of Rpb9 and the trigger loop of Rpb1.","method":"In vitro NTP misincorporation assay, pre-steady state kinetic analysis, synthetic lethality with rpb1-E1103G, comparison of wild-type and rpb9Δ polymerases","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — pre-steady state kinetics with mechanistic model, multiple in vitro assays, genetic validation, single lab","pmids":["19439405"],"is_preprint":false},{"year":2013,"finding":"In the absence of Rpb9, the rate of error propagation (extending a mismatched RNA 3' end) is increased 2-3 fold in multiple sequence contexts; TFIIS-mediated error excision rate and extent are also significantly compromised without Rpb9; Rpb9 facilitates formation of a conformation necessary for RNA cleavage by TFIIS. No effect of Rpb9 on NTP selectivity was observed.","method":"In vitro transcription elongation assay with mismatched RNA, competition kinetics, TFIIS-stimulated cleavage assay","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — quantitative in vitro kinetic assays with multiple sequence contexts, two orthogonal functional readouts, single lab","pmids":["24099331"],"is_preprint":false},{"year":2016,"finding":"Rpb9 indirectly modulates trigger loop (TL) mobility by anchoring the position of Rpb1 α-helix 21 (α21), which directly interacts with the TL during opening and closing; missense alleles of RPB9 that suppress rpb1-G730D (α21 substitution) confirm this structural relationship; disruption of proposed anchoring interactions in Rpb9 or Rpb1 results in increased elongation rate in vitro and phenotypes shared by rpb9Δ strains; α-amanitin (TL mobility inhibitor) suppresses the effect of Rpb9 loss on NTP misincorporation.","method":"Genetic suppressor screen, site-directed mutagenesis, in vitro elongation rate assay, NTP misincorporation assay, epistasis analysis of double mutants","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with biochemical in vitro validation, multiple alleles, single lab","pmids":["27226557"],"is_preprint":false},{"year":2021,"finding":"In C. elegans, the RNA Pol II core subunit RPB-9 is required for piRNA biogenesis by recruiting the Integrator complex to piRNA genes, thereby promoting transcriptional termination; loss of rpb-9 impairs piRNA-mediated gene silencing and heritable silencing at DNA transposon families.","method":"Genetic screen (C. elegans KO), biochemical co-immunoprecipitation, genetic epistasis, piRNA sequencing","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic and biochemical evidence in C. elegans ortholog, co-IP for Integrator recruitment, single lab","pmids":["33533030"],"is_preprint":false},{"year":2018,"finding":"Rpb9-deficient yeast cells show defective DNA damage checkpoint activation (reduced γH2A and Rad53 signaling); histone H3 N-terminal lysine acetylation becomes essential for DNA double-strand break repair and viability in the absence of Rpb9; combined loss leads to genomic instability and aberrant chromosome segregation.","method":"Genetic double-mutant analysis, western blot for checkpoint markers (γH2A, Rad53), cell viability assay, microscopy for chromosome segregation","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal readouts (checkpoint markers, viability, chromosome segregation), single lab","pmids":["29440683"],"is_preprint":false},{"year":2022,"finding":"The RNA polymerase II subunit Rpb9 specifically activates ATG1 transcription by binding to the ATG1 promoter region in a manner mediated by the transcription factor Gcn4; Rpb9 deficiency reduces autophagic activity; this function is conserved in mammalian cells where Rpb9 regulates ULK1 (ATG1 ortholog) transcription.","method":"High-throughput KO library screen, ChIP (promoter binding), qRT-PCR, autophagy flux assay, mammalian cell knockdown","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP showing direct promoter binding, multiple functional readouts, conservation validated in mammalian cells, single lab","pmids":["36102592"],"is_preprint":false},{"year":2025,"finding":"Knockdown of polr2i in zebrafish disrupts cardiac development, causing elongated heart tubes with reduced chamber overlap, pericardial edema, reduced ejection fraction and cardiac output, disrupted left-right asymmetry of heart/liver/pancreas, and impaired mitochondrial quality in myocardial cells; these phenotypes are rescued by co-injection of polr2i mRNA, confirming specificity.","method":"Morpholino-mediated knockdown in zebrafish, mRNA rescue experiments, transgenic fluorescent reporter lines, cardiac functional measurements, hemoglobin staining","journal":"Frontiers in bioscience (Landmark edition)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MO knockdown with mRNA rescue confirmation, multiple cardiac phenotype readouts, single lab","pmids":["41198546"],"is_preprint":false}],"current_model":"POLR2I (RPB9) is a conserved, non-essential subunit of RNA polymerase II that contributes to accurate transcription start site selection (via functional interactions with TFIIB and TFIIF), promotes transcription elongation fidelity by stabilizing trigger loop positioning to delay premature NTP sequestration, facilitates TFIIS-mediated transcript cleavage and proofreading, recruits TFIIE to the polymerase, mediates a distinct subpathway of transcription-coupled DNA repair (requiring its Zn1/linker domains), promotes UV-induced ubiquitylation and proteasomal degradation of Rpb1 (requiring its Zn2 domain), activates ATG1/ULK1 transcription via Gcn4 to regulate autophagy, and is required for normal cardiac development in vertebrates."},"narrative":{"mechanistic_narrative":"POLR2I (RPB9) is a conserved, non-essential subunit of RNA polymerase II that integrates transcription start site selection, elongation fidelity, and transcription-coupled DNA repair into the polymerase's catalytic cycle [PMID:7883169, PMID:9169440, PMID:12411509]. At initiation, RPB9 directs accurate start site selection, and recombinant protein add-back fully rescues the upstream start-site shifts seen on its deletion; this function reflects functional interactions with the general transcription factors TFIIB and TFIIF and contributes to recruitment of TFIIE to the polymerase [PMID:7883169, PMID:8692696, PMID:14522989, PMID:11779853]. During elongation, RPB9 controls transcriptional fidelity in the active center by delaying premature trigger-loop closure on incoming NTP—an effect mediated through its C-terminal domain contacting the Rpb1 trigger loop and anchoring of Rpb1 helix α21—so that its loss elevates misincorporation and error propagation in vivo and in vitro [PMID:19439405, PMID:27226557, PMID:16492753, PMID:24099331]. RPB9 is also required for TFIIS-mediated transcript cleavage and read-through of arrest sites, linking proofreading to elongation competence [PMID:9169440, PMID:24099331]. These elongation activities feed a dedicated, Rad26-independent subpathway of transcription-coupled DNA repair that requires the Zn1 and linker domains, while a separate Zn2-dependent activity promotes UV-induced ubiquitylation and proteasomal degradation of Rpb1 [PMID:12411509, PMID:17030604, PMID:17452455]. Beyond core transcription, RPB9 activates ATG1/ULK1 transcription through the transcription factor Gcn4 to support autophagy [PMID:36102592], and depletion of zebrafish polr2i disrupts cardiac development with phenotypes rescued by polr2i mRNA [PMID:41198546].","teleology":[{"year":1991,"claim":"Established that RPB9 is a genuine but dispensable Pol II subunit, defining the question of what specialized function a non-essential polymerase subunit serves.","evidence":"Gene deletion and genetic growth assays in yeast","pmids":["1918023"],"confidence":"Medium","gaps":["Does not identify the molecular step RPB9 acts on","Conditional growth phenotype not mechanistically explained"]},{"year":1995,"claim":"Showed RPB9 governs accurate transcription start site selection, assigning it a defined role at initiation rather than general mRNA synthesis.","evidence":"Deletion plus in vitro reconstitution with recombinant add-back and metal-binding domain mutagenesis","pmids":["7883169"],"confidence":"High","gaps":["Does not define which general factors mediate the effect","Structural basis of start-site shift unresolved"]},{"year":1996,"claim":"Placed RPB9 in a genetic circuit with TFIIB, indicating start-site selection is set by Rpb9-TFIIB cooperation in the preinitiation complex.","evidence":"Genetic suppressor screen with defined alleles and in vivo start site analysis","pmids":["8692696"],"confidence":"Medium","gaps":["Genetic interaction does not prove direct physical contact","C-terminal truncation effect not structurally mapped"]},{"year":1997,"claim":"Resolved RPB9's elongation role: it restrains read-through at arrest sites and is required for TFIIS-stimulated reactivation, coupling the subunit to proofreading.","evidence":"In vitro elongation and TFIIS stimulation assays with recombinant RPB9 reconstitution","pmids":["9169440"],"confidence":"High","gaps":["Does not define the domain or contact mediating TFIIS dependence","In vivo relevance to fidelity not yet shown"]},{"year":2000,"claim":"Dissected RPB9 domains, assigning the linker to Pol II docking and the C-terminal zinc ribbon acidic loop to elongation activity.","evidence":"Site-directed mutagenesis and deletion analysis with in vitro elongation assays","pmids":["10644677","10938084"],"confidence":"High","gaps":["Separable initiation versus elongation functions not yet linked to repair","Single-domain stimulation failure mechanism unclear"]},{"year":2002,"claim":"Defined an Rpb9-mediated transcription-coupled repair subpathway distinct from Rad26 and showed Rpb9 contributes to TFIIE recruitment, broadening its role to repair and PIC assembly.","evidence":"Single/double deletion strand-specific UV repair assays; yeast two-hybrid and co-IP for TFIIE","pmids":["12411509","11779853"],"confidence":"High","gaps":["TFIIE interaction shown by two-hybrid/co-IP without reciprocal structural validation","Mechanistic link between elongation and the TCR subpathway not yet established"]},{"year":2003,"claim":"Identified impaired Pol II-TFIIF interaction in Rpb9-deficient polymerase as the basis for upstream start-site shifts, connecting the initiation defect to a specific factor contact.","evidence":"Reconstituted transcription with purified factors and gel mobility shift assays","pmids":["14522989"],"confidence":"High","gaps":["Does not resolve whether the TFIIF contact is direct or polymerase-conformation mediated"]},{"year":2006,"claim":"Demonstrated in vivo error-prone transcription on RPB9 loss and mapped TCR and elongation to the shared Zn1/linker domains, establishing elongation competence as a prerequisite for the Rpb9 repair subpathway.","evidence":"In vivo fidelity assay with cDNA sequencing; domain-deletion UV repair and elongation assays; promoter-element mutagenesis","pmids":["16492753","17030604","17023424"],"confidence":"Medium","gaps":["Molecular signal coupling elongation to repair not defined","SAGA dependence of the subpathway not mechanistically explained"]},{"year":2007,"claim":"Assigned the Zn2 domain a distinct role in UV-triggered Rpb1 ubiquitylation and proteasomal degradation, separating a damage-response function from the elongation/repair functions.","evidence":"UV irradiation, western blot for ubiquitylation/degradation, domain deletion, co-IP and proteasome inhibition","pmids":["17452455"],"confidence":"Medium","gaps":["The ubiquitin ligase recruited via Zn2 not identified","Single-lab co-IP for Pol II interaction"]},{"year":2013,"claim":"Provided a unified active-center mechanism: RPB9 delays NTP sequestration by acting on the trigger loop, controlling both misincorporation and error propagation and enabling TFIIS cleavage.","evidence":"Pre-steady state kinetics, NTP misincorporation and TFIIS cleavage assays, genetic synthetic lethality with rpb1 trigger-loop alleles","pmids":["19439405","24099331"],"confidence":"High","gaps":["Direct structural contact between Rpb9 C-terminus and trigger loop not solved","No effect on NTP selectivity leaves selection step unexplained"]},{"year":2016,"claim":"Refined the active-center model to an indirect mechanism in which Rpb9 anchors Rpb1 helix α21 to modulate trigger-loop mobility, explaining its kinetic effects.","evidence":"Genetic suppressor screen, mutagenesis, in vitro elongation and misincorporation assays, α-amanitin epistasis","pmids":["27226557"],"confidence":"Medium","gaps":["Anchoring interaction inferred genetically/biochemically without a structure","Quantitative contribution to in vivo fidelity unclear"]},{"year":2021,"claim":"Extended RPB9 function to small-RNA biogenesis, showing the C. elegans ortholog recruits the Integrator complex to drive piRNA gene termination and silencing.","evidence":"C. elegans knockout, co-IP for Integrator recruitment, genetic epistasis and piRNA sequencing","pmids":["33533030"],"confidence":"Medium","gaps":["Whether the Integrator-recruitment role is conserved beyond C. elegans untested","Single-lab co-IP without reciprocal validation"]},{"year":2022,"claim":"Identified a promoter-specific gene-regulatory role: Rpb9 activates ATG1/ULK1 transcription via Gcn4 to control autophagy, conserved to mammalian cells.","evidence":"KO library screen, ChIP for promoter binding, qRT-PCR, autophagy flux, mammalian knockdown","pmids":["36102592"],"confidence":"Medium","gaps":["How a core Pol II subunit confers gene-selective activation not explained","Direct versus Gcn4-dependent recruitment not fully separated"]},{"year":2018,"claim":"Linked Rpb9 to genome stability through DNA damage checkpoint activation and a synthetic dependence on histone H3 acetylation for double-strand break repair.","evidence":"Double-mutant analysis, checkpoint marker western blots, viability and chromosome segregation microscopy","pmids":["29440683"],"confidence":"Medium","gaps":["Mechanism by which Rpb9 supports checkpoint signaling unresolved","Connection to its transcription/TCR roles not established"]},{"year":2025,"claim":"Established an organismal requirement for POLR2I in vertebrate cardiac development, with mRNA rescue confirming specificity.","evidence":"Morpholino knockdown with mRNA rescue and cardiac functional/imaging readouts in zebrafish","pmids":["41198546"],"confidence":"Medium","gaps":["Which transcriptional function underlies the cardiac phenotype unknown","Mitochondrial quality defect mechanistically uncharacterized"]},{"year":null,"claim":"It remains unresolved how the distinct domain-specific activities of POLR2I (initiation, elongation fidelity, TCR, Rpb1 degradation, gene-selective activation) are coordinated within an intact organism and whether the conserved cardiac and autophagy roles reflect a single underlying transcriptional defect.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of human POLR2I within Pol II in the corpus","Tissue-specific transcriptional targets in vertebrates undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[3,13,14]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[1,18]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,1]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[7,8]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[1,18]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[1,3,13]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[6,9,12]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[18]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[16]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[19]}],"complexes":["RNA polymerase II"],"partners":["TFIIB","TFIIF","TFIIE","TFIIS","RPB1","GCN4"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P36954","full_name":"DNA-directed RNA polymerase II subunit RPB9","aliases":["DNA-directed RNA polymerase II subunit I","RNA polymerase II 14.5 kDa subunit","RPB14.5"],"length_aa":125,"mass_kda":14.5,"function":"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. Pol II is the central component of the basal RNA polymerase II transcription machinery. It is composed of mobile elements that move relative to each other. POLR2I/RPB9 is part of the upper jaw surrounding the central large cleft and thought to grab the incoming DNA template","subcellular_location":"Nucleus, nucleolus","url":"https://www.uniprot.org/uniprotkb/P36954/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/POLR2I","classification":"Common Essential","n_dependent_lines":1208,"n_total_lines":1208,"dependency_fraction":1.0},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000105258","cell_line_id":"CID000704","localizations":[{"compartment":"nucleoplasm","grade":3},{"compartment":"cytoplasmic","grade":1},{"compartment":"nuclear_punctae","grade":1}],"interactors":[{"gene":"POLR2B","stoichiometry":10.0},{"gene":"POLR2C","stoichiometry":10.0},{"gene":"POLR2E","stoichiometry":10.0},{"gene":"POLR2F","stoichiometry":10.0},{"gene":"POLR2H","stoichiometry":10.0},{"gene":"POLR2D","stoichiometry":10.0},{"gene":"POLR2A","stoichiometry":10.0},{"gene":"POLR2J","stoichiometry":10.0},{"gene":"GTF2B","stoichiometry":4.0},{"gene":"POLR2G","stoichiometry":4.0}],"url":"https://opencell.sf.czbiohub.org/target/CID000704","total_profiled":1310},"omim":[{"mim_id":"602013","title":"POLYMERASE II, RNA, SUBUNIT G; POLR2G","url":"https://www.omim.org/entry/602013"},{"mim_id":"180662","title":"POLYMERASE II, RNA, SUBUNIT I; POLR2I","url":"https://www.omim.org/entry/180662"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Nucleoplasm","reliability":"Enhanced"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/POLR2I"},"hgnc":{"alias_symbol":["RPB9","hRPB14.5"],"prev_symbol":[]},"alphafold":{"accession":"P36954","domains":[{"cath_id":"2.20.25.10","chopping":"1-58","consensus_level":"medium","plddt":84.7881,"start":1,"end":58},{"cath_id":"2.20.25.10","chopping":"63-123","consensus_level":"high","plddt":88.7098,"start":63,"end":123}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P36954","model_url":"https://alphafold.ebi.ac.uk/files/AF-P36954-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P36954-F1-predicted_aligned_error_v6.png","plddt_mean":85.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=POLR2I","jax_strain_url":"https://www.jax.org/strain/search?query=POLR2I"},"sequence":{"accession":"P36954","fasta_url":"https://rest.uniprot.org/uniprotkb/P36954.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P36954/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P36954"}},"corpus_meta":[{"pmid":"12411509","id":"PMC_12411509","title":"Rpb4 and Rpb9 mediate subpathways of transcription-coupled DNA repair in Saccharomyces cerevisiae.","date":"2002","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/12411509","citation_count":109,"is_preprint":false},{"pmid":"9169440","id":"PMC_9169440","title":"Transcription elongation through DNA arrest sites. A multistep process involving both RNA polymerase II subunit RPB9 and TFIIS.","date":"1997","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9169440","citation_count":101,"is_preprint":false},{"pmid":"7883169","id":"PMC_7883169","title":"RNA polymerase II subunit RPB9 is required for accurate start site selection.","date":"1995","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/7883169","citation_count":97,"is_preprint":false},{"pmid":"1918023","id":"PMC_1918023","title":"Yeast RNA polymerase II subunit RPB9 is essential for growth at temperature extremes.","date":"1991","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/1918023","citation_count":86,"is_preprint":false},{"pmid":"10938084","id":"PMC_10938084","title":"RNA polymerase II subunit Rpb9 regulates transcription elongation in vivo.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10938084","citation_count":82,"is_preprint":false},{"pmid":"19439405","id":"PMC_19439405","title":"Rpb9 subunit controls transcription fidelity by delaying NTP sequestration in RNA polymerase II.","date":"2009","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19439405","citation_count":72,"is_preprint":false},{"pmid":"16492753","id":"PMC_16492753","title":"RNA polymerase II subunit Rpb9 is important for transcriptional fidelity in vivo.","date":"2006","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/16492753","citation_count":69,"is_preprint":false},{"pmid":"8692696","id":"PMC_8692696","title":"Functional interaction between TFIIB and the Rpb9 (Ssu73) subunit of RNA polymerase II in Saccharomyces cerevisiae.","date":"1996","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/8692696","citation_count":56,"is_preprint":false},{"pmid":"11779853","id":"PMC_11779853","title":"The Rpb9 subunit of RNA polymerase II binds transcription factor TFIIE and interferes with the SAGA and elongator histone acetyltransferases.","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11779853","citation_count":51,"is_preprint":false},{"pmid":"21450810","id":"PMC_21450810","title":"Point mutations in the Rpb9-homologous domain of Rpc11 that impair transcription termination by RNA polymerase III.","date":"2011","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/21450810","citation_count":32,"is_preprint":false},{"pmid":"17452455","id":"PMC_17452455","title":"Yeast Rpb9 plays an important role in ubiquitylation and degradation of Rpb1 in response to UV-induced DNA damage.","date":"2007","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/17452455","citation_count":30,"is_preprint":false},{"pmid":"10644677","id":"PMC_10644677","title":"Yeast RNA polymerase II subunit RPB9. Mapping of domains required for transcription elongation.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10644677","citation_count":29,"is_preprint":false},{"pmid":"24099331","id":"PMC_24099331","title":"Fidelity of RNA polymerase II transcription: Role of Rpb9 [corrected] in error detection and proofreading.","date":"2013","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/24099331","citation_count":25,"is_preprint":false},{"pmid":"33533030","id":"PMC_33533030","title":"The RNA polymerase II subunit RPB-9 recruits the integrator complex to terminate Caenorhabditis elegans piRNA transcription.","date":"2021","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/33533030","citation_count":25,"is_preprint":false},{"pmid":"14522989","id":"PMC_14522989","title":"Yeast RNA polymerase II lacking the Rpb9 subunit is impaired for interaction with transcription factor IIF.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/14522989","citation_count":24,"is_preprint":false},{"pmid":"17030604","id":"PMC_17030604","title":"Evidence that the transcription elongation function of Rpb9 is involved in transcription-coupled DNA repair in Saccharomyces cerevisiae.","date":"2006","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/17030604","citation_count":24,"is_preprint":false},{"pmid":"27226557","id":"PMC_27226557","title":"RNA Polymerase II Trigger Loop Mobility: INDIRECT EFFECTS OF Rpb9.","date":"2016","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/27226557","citation_count":17,"is_preprint":false},{"pmid":"9852944","id":"PMC_9852944","title":"Identification of the gene and the protein of RNA polymerase II subunit 9 (Rpb9) from the fission yeast Schizosacharomyces pombe.","date":"1998","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/9852944","citation_count":17,"is_preprint":false},{"pmid":"17023424","id":"PMC_17023424","title":"Modulation of Rad26- and Rpb9-mediated DNA repair by different promoter elements.","date":"2006","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17023424","citation_count":11,"is_preprint":false},{"pmid":"29440683","id":"PMC_29440683","title":"Rpb9-deficient cells are defective in DNA damage response and require histone H3 acetylation for survival.","date":"2018","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/29440683","citation_count":9,"is_preprint":false},{"pmid":"36102592","id":"PMC_36102592","title":"The RNA polymerase II subunit Rpb9 activates ATG1 transcription and autophagy.","date":"2022","source":"EMBO reports","url":"https://pubmed.ncbi.nlm.nih.gov/36102592","citation_count":5,"is_preprint":false},{"pmid":"33775921","id":"PMC_33775921","title":"Deletion of the non-essential Rpb9 subunit of RNA polymerase II results in pleiotropic phenotypes in Schizosaccharomyces pombe.","date":"2021","source":"Biochimica et biophysica acta. Proteins and proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/33775921","citation_count":3,"is_preprint":false},{"pmid":"35618649","id":"PMC_35618649","title":"Absence of the Rpb9 subunit of RNA polymerase II reduces the chronological life span in fission yeast.","date":"2022","source":"Journal of basic microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/35618649","citation_count":2,"is_preprint":false},{"pmid":"41198546","id":"PMC_41198546","title":"polr2i is Required for Zebrafish Early Cardiac Development.","date":"2025","source":"Frontiers in bioscience (Landmark edition)","url":"https://pubmed.ncbi.nlm.nih.gov/41198546","citation_count":0,"is_preprint":false},{"pmid":"11041002","id":"PMC_11041002","title":"[Chromosomal localization of rpb9+ and tfa1+ genes, coding for components of the mRNA synthesis apparatus of Schizosaccharomyces pombe].","date":"2000","source":"Bioorganicheskaia khimiia","url":"https://pubmed.ncbi.nlm.nih.gov/11041002","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.05.12.653476","title":"Reorganizing the RNA polymerase II complex for replication of an infectious noncoding RNA in vivo","date":"2025-05-12","source":"bioRxiv","url":"https://doi.org/10.1101/2025.05.12.653476","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":12957,"output_tokens":4762,"usd":0.05515,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13053,"output_tokens":4483,"usd":0.08867,"stage2_stop_reason":"end_turn"},"total_usd":0.14382,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1991,\n      \"finding\": \"RPB9 is a non-essential subunit of RNA polymerase II required for normal cell growth over a wide temperature range; deletion produces heat- and cold-sensitive cells but does not abolish mRNA synthesis.\",\n      \"method\": \"Gene deletion/disruption, genetic growth assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with defined growth phenotype, single lab but foundational characterization\",\n      \"pmids\": [\"1918023\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"RPB9 is required for accurate transcription start site selection by RNA polymerase II; deletion causes upstream shifts to new or previously minor start sites at multiple promoters in vivo and in vitro, and addition of recombinant RPB9 fully rescues the initiation defect in vitro.\",\n      \"method\": \"RPB9 gene deletion, in vitro transcription reconstitution, recombinant protein add-back, site-directed mutagenesis of metal-binding domain\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution with recombinant protein, mutagenesis, multiple promoters in vivo and in vitro, replicated in subsequent studies\",\n      \"pmids\": [\"7883169\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"RPB9 (SSU73) functionally interacts with TFIIB in transcription start site selection; the ssu73-1 allele (nonsense at codon 107, truncating the C-terminal 16 aa) suppresses both the growth defect and downstream start site shift caused by the sua7-1 TFIIB mutation, establishing a functional interaction between Rpb9 and TFIIB during preinitiation complex formation.\",\n      \"method\": \"Genetic suppressor screen, allele isolation and sequencing, in vivo start site analysis\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with defined alleles, single lab, start site phenotype confirmed in vivo\",\n      \"pmids\": [\"8692696\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"RPB9 promotes transcription elongation through DNA arrest sites and is required for TFIIS-mediated read-through; RNA polymerase II lacking RPB9 (pol IIDelta9) elongates more efficiently through pause/arrest sequences but cannot be reactivated by TFIIS; addition of recombinant RPB9 to pol IIDelta9 restores wild-type elongation properties.\",\n      \"method\": \"In vitro transcription elongation assay, biochemical reconstitution with recombinant RPB9, TFIIS stimulation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution with purified recombinant protein, multiple orthogonal in vitro assays, transcript cleavage uncoupling experiment\",\n      \"pmids\": [\"9169440\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The C-terminal zinc ribbon acidic loop of RPB9 is critical for transcription elongation activity; the conserved linker region (residues 89-95, DPTLPR) mediates interaction with RNA polymerase II; individual zinc ribbon domains in isolation cannot stimulate transcription by pol IIDelta9.\",\n      \"method\": \"Site-directed mutagenesis, deletion analysis, in vitro transcription elongation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic mutagenesis with functional in vitro assay, multiple mutants tested, defines interaction domain\",\n      \"pmids\": [\"10644677\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"RPB9 has a synthetic phenotype with the TFIIS gene (DST1) for 6-azauracil sensitivity; overexpression of TFIIS partially suppresses the 6-AU sensitivity of rpb9Δ cells; the N-terminal zinc ribbon restores wild-type initiation start sites but does not complement elongation-specific growth defects, indicating separable functions of the two domains.\",\n      \"method\": \"Genetic epistasis (double deletion), drug sensitivity assay, high-copy suppression, domain complementation in vivo, genome-wide transcription profiling\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with domain dissection in vivo, multiple methods, single lab\",\n      \"pmids\": [\"10938084\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"RPB9 mediates a subpathway of transcription-coupled DNA repair (TCR) in S. cerevisiae that is independent of Rad26 and operates more effectively in the coding region; simultaneous deletion of RPB9 and RAD26 completely abolishes TCR, indicating these are the only two TCR subpathways in RNA Pol II-transcribed genes; RPB4 suppresses the RPB9-mediated TCR subpathway.\",\n      \"method\": \"Gene deletion (single and double mutants), UV-induced DNA damage repair assay (strand-specific), genetic epistasis\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean double-KO with complete abolition of TCR, strand-specific repair assay, replicated in subsequent domain-mapping studies\",\n      \"pmids\": [\"12411509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Rpb9 physically interacts with Tfa1, the largest subunit of TFIIE, via a two-hybrid interaction; co-immunoprecipitation of TFIIE with RNA polymerase II is strongly reduced in rpb9Δ, indicating Rpb9 contributes to TFIIE recruitment to the polymerase; rpb9 mutations are synthetically lethal with loss of Elongator or SAGA histone acetyltransferase activity.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, synthetic lethality analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — two-hybrid plus co-IP for TFIIE interaction, synthetic lethality for acetyltransferase link, single lab\",\n      \"pmids\": [\"11779853\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"RNA polymerase II lacking Rpb9 has an impaired interaction with TFIIF (Tfg1-Tfg2 complex), and this impaired interaction is associated with upstream shifts in mRNA 5'-end positions in reconstituted transcription assays with purified general transcription factors.\",\n      \"method\": \"Reconstituted in vitro transcription with purified factors, gel mobility shift assay, recombinant holo-TFIIF production\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — reconstituted transcription with highly purified components, gel shift for direct interaction, single lab\",\n      \"pmids\": [\"14522989\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The Zn1 and linker domains of Rpb9 are essential for both transcription elongation and TCR functions; the Zn2 domain is dispensable for these functions; impairment of transcription elongation completely abolishes Rpb9-mediated TCR, suggesting the elongation function of Rpb9 is required for TCR.\",\n      \"method\": \"Domain deletion mutagenesis, UV repair assay (strand-specific), transcription elongation assay in vivo\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic domain dissection with multiple functional readouts, single lab\",\n      \"pmids\": [\"17030604\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"RPB9-mediated TCR is strictly transcription-coupled and requires both TATA and UAS sequences; its efficiency depends on the SAGA complex; Rad26-mediated repair operates differently and can function independently of transcription when transcription levels are too low.\",\n      \"method\": \"Promoter element deletion/mutation, strand-specific UV repair assay, genetic analysis of SAGA complex\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple promoter mutants with quantitative repair assays, single lab\",\n      \"pmids\": [\"17023424\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Deletion of RPB9 in yeast results in error-prone transcription in vivo, as measured by increased read-through of a nonsense allele (can1-100); rpb9Δ strains have increased steady-state levels of can1-100 mRNA and sequence analysis of cDNAs confirmed significantly increased transcriptional substitutions and insertions.\",\n      \"method\": \"In vivo transcription fidelity assay (canavanine sensitivity), cDNA sequencing, Northern blot\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo functional assay with direct cDNA sequencing confirmation, single lab\",\n      \"pmids\": [\"16492753\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"In response to UV radiation, Rpb9 promotes ubiquitylation and degradation of Rpb1 (the largest Pol II subunit) via the 26S proteasome; the Zn2 domain is essential for this function while Zn1 and linker play subsidiary roles; co-immunoprecipitation shows that near-full-length Rpb9 is required for strong interaction with core Pol II.\",\n      \"method\": \"UV irradiation, western blot for ubiquitylation and degradation, domain deletion mutagenesis, co-immunoprecipitation, proteasome inhibitor treatment\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus functional degradation assay with domain dissection, single lab\",\n      \"pmids\": [\"17452455\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"RPB9 controls transcription fidelity by delaying NTP sequestration in the RNA polymerase II active center; RPB9 deletion promotes premature closure of the trigger loop on incoming NTP prior to phosphodiester bond formation, enhancing NTP misincorporation and mismatch extension; this is mediated by interaction between the C-terminal domain of Rpb9 and the trigger loop of Rpb1.\",\n      \"method\": \"In vitro NTP misincorporation assay, pre-steady state kinetic analysis, synthetic lethality with rpb1-E1103G, comparison of wild-type and rpb9Δ polymerases\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — pre-steady state kinetics with mechanistic model, multiple in vitro assays, genetic validation, single lab\",\n      \"pmids\": [\"19439405\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In the absence of Rpb9, the rate of error propagation (extending a mismatched RNA 3' end) is increased 2-3 fold in multiple sequence contexts; TFIIS-mediated error excision rate and extent are also significantly compromised without Rpb9; Rpb9 facilitates formation of a conformation necessary for RNA cleavage by TFIIS. No effect of Rpb9 on NTP selectivity was observed.\",\n      \"method\": \"In vitro transcription elongation assay with mismatched RNA, competition kinetics, TFIIS-stimulated cleavage assay\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — quantitative in vitro kinetic assays with multiple sequence contexts, two orthogonal functional readouts, single lab\",\n      \"pmids\": [\"24099331\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Rpb9 indirectly modulates trigger loop (TL) mobility by anchoring the position of Rpb1 α-helix 21 (α21), which directly interacts with the TL during opening and closing; missense alleles of RPB9 that suppress rpb1-G730D (α21 substitution) confirm this structural relationship; disruption of proposed anchoring interactions in Rpb9 or Rpb1 results in increased elongation rate in vitro and phenotypes shared by rpb9Δ strains; α-amanitin (TL mobility inhibitor) suppresses the effect of Rpb9 loss on NTP misincorporation.\",\n      \"method\": \"Genetic suppressor screen, site-directed mutagenesis, in vitro elongation rate assay, NTP misincorporation assay, epistasis analysis of double mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with biochemical in vitro validation, multiple alleles, single lab\",\n      \"pmids\": [\"27226557\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In C. elegans, the RNA Pol II core subunit RPB-9 is required for piRNA biogenesis by recruiting the Integrator complex to piRNA genes, thereby promoting transcriptional termination; loss of rpb-9 impairs piRNA-mediated gene silencing and heritable silencing at DNA transposon families.\",\n      \"method\": \"Genetic screen (C. elegans KO), biochemical co-immunoprecipitation, genetic epistasis, piRNA sequencing\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic and biochemical evidence in C. elegans ortholog, co-IP for Integrator recruitment, single lab\",\n      \"pmids\": [\"33533030\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Rpb9-deficient yeast cells show defective DNA damage checkpoint activation (reduced γH2A and Rad53 signaling); histone H3 N-terminal lysine acetylation becomes essential for DNA double-strand break repair and viability in the absence of Rpb9; combined loss leads to genomic instability and aberrant chromosome segregation.\",\n      \"method\": \"Genetic double-mutant analysis, western blot for checkpoint markers (γH2A, Rad53), cell viability assay, microscopy for chromosome segregation\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal readouts (checkpoint markers, viability, chromosome segregation), single lab\",\n      \"pmids\": [\"29440683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The RNA polymerase II subunit Rpb9 specifically activates ATG1 transcription by binding to the ATG1 promoter region in a manner mediated by the transcription factor Gcn4; Rpb9 deficiency reduces autophagic activity; this function is conserved in mammalian cells where Rpb9 regulates ULK1 (ATG1 ortholog) transcription.\",\n      \"method\": \"High-throughput KO library screen, ChIP (promoter binding), qRT-PCR, autophagy flux assay, mammalian cell knockdown\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP showing direct promoter binding, multiple functional readouts, conservation validated in mammalian cells, single lab\",\n      \"pmids\": [\"36102592\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Knockdown of polr2i in zebrafish disrupts cardiac development, causing elongated heart tubes with reduced chamber overlap, pericardial edema, reduced ejection fraction and cardiac output, disrupted left-right asymmetry of heart/liver/pancreas, and impaired mitochondrial quality in myocardial cells; these phenotypes are rescued by co-injection of polr2i mRNA, confirming specificity.\",\n      \"method\": \"Morpholino-mediated knockdown in zebrafish, mRNA rescue experiments, transgenic fluorescent reporter lines, cardiac functional measurements, hemoglobin staining\",\n      \"journal\": \"Frontiers in bioscience (Landmark edition)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MO knockdown with mRNA rescue confirmation, multiple cardiac phenotype readouts, single lab\",\n      \"pmids\": [\"41198546\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"POLR2I (RPB9) is a conserved, non-essential subunit of RNA polymerase II that contributes to accurate transcription start site selection (via functional interactions with TFIIB and TFIIF), promotes transcription elongation fidelity by stabilizing trigger loop positioning to delay premature NTP sequestration, facilitates TFIIS-mediated transcript cleavage and proofreading, recruits TFIIE to the polymerase, mediates a distinct subpathway of transcription-coupled DNA repair (requiring its Zn1/linker domains), promotes UV-induced ubiquitylation and proteasomal degradation of Rpb1 (requiring its Zn2 domain), activates ATG1/ULK1 transcription via Gcn4 to regulate autophagy, and is required for normal cardiac development in vertebrates.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"POLR2I (RPB9) is a conserved, non-essential subunit of RNA polymerase II that integrates transcription start site selection, elongation fidelity, and transcription-coupled DNA repair into the polymerase's catalytic cycle [#1, #3, #6]. At initiation, RPB9 directs accurate start site selection, and recombinant protein add-back fully rescues the upstream start-site shifts seen on its deletion; this function reflects functional interactions with the general transcription factors TFIIB and TFIIF and contributes to recruitment of TFIIE to the polymerase [#1, #2, #8, #7]. During elongation, RPB9 controls transcriptional fidelity in the active center by delaying premature trigger-loop closure on incoming NTP—an effect mediated through its C-terminal domain contacting the Rpb1 trigger loop and anchoring of Rpb1 helix α21—so that its loss elevates misincorporation and error propagation in vivo and in vitro [#13, #15, #11, #14]. RPB9 is also required for TFIIS-mediated transcript cleavage and read-through of arrest sites, linking proofreading to elongation competence [#3, #14]. These elongation activities feed a dedicated, Rad26-independent subpathway of transcription-coupled DNA repair that requires the Zn1 and linker domains, while a separate Zn2-dependent activity promotes UV-induced ubiquitylation and proteasomal degradation of Rpb1 [#6, #9, #12]. Beyond core transcription, RPB9 activates ATG1/ULK1 transcription through the transcription factor Gcn4 to support autophagy [#18], and depletion of zebrafish polr2i disrupts cardiac development with phenotypes rescued by polr2i mRNA [#19].\",\n  \"teleology\": [\n    {\n      \"year\": 1991,\n      \"claim\": \"Established that RPB9 is a genuine but dispensable Pol II subunit, defining the question of what specialized function a non-essential polymerase subunit serves.\",\n      \"evidence\": \"Gene deletion and genetic growth assays in yeast\",\n      \"pmids\": [\"1918023\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not identify the molecular step RPB9 acts on\", \"Conditional growth phenotype not mechanistically explained\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Showed RPB9 governs accurate transcription start site selection, assigning it a defined role at initiation rather than general mRNA synthesis.\",\n      \"evidence\": \"Deletion plus in vitro reconstitution with recombinant add-back and metal-binding domain mutagenesis\",\n      \"pmids\": [\"7883169\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not define which general factors mediate the effect\", \"Structural basis of start-site shift unresolved\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Placed RPB9 in a genetic circuit with TFIIB, indicating start-site selection is set by Rpb9-TFIIB cooperation in the preinitiation complex.\",\n      \"evidence\": \"Genetic suppressor screen with defined alleles and in vivo start site analysis\",\n      \"pmids\": [\"8692696\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Genetic interaction does not prove direct physical contact\", \"C-terminal truncation effect not structurally mapped\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Resolved RPB9's elongation role: it restrains read-through at arrest sites and is required for TFIIS-stimulated reactivation, coupling the subunit to proofreading.\",\n      \"evidence\": \"In vitro elongation and TFIIS stimulation assays with recombinant RPB9 reconstitution\",\n      \"pmids\": [\"9169440\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not define the domain or contact mediating TFIIS dependence\", \"In vivo relevance to fidelity not yet shown\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Dissected RPB9 domains, assigning the linker to Pol II docking and the C-terminal zinc ribbon acidic loop to elongation activity.\",\n      \"evidence\": \"Site-directed mutagenesis and deletion analysis with in vitro elongation assays\",\n      \"pmids\": [\"10644677\", \"10938084\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Separable initiation versus elongation functions not yet linked to repair\", \"Single-domain stimulation failure mechanism unclear\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Defined an Rpb9-mediated transcription-coupled repair subpathway distinct from Rad26 and showed Rpb9 contributes to TFIIE recruitment, broadening its role to repair and PIC assembly.\",\n      \"evidence\": \"Single/double deletion strand-specific UV repair assays; yeast two-hybrid and co-IP for TFIIE\",\n      \"pmids\": [\"12411509\", \"11779853\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"TFIIE interaction shown by two-hybrid/co-IP without reciprocal structural validation\", \"Mechanistic link between elongation and the TCR subpathway not yet established\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identified impaired Pol II-TFIIF interaction in Rpb9-deficient polymerase as the basis for upstream start-site shifts, connecting the initiation defect to a specific factor contact.\",\n      \"evidence\": \"Reconstituted transcription with purified factors and gel mobility shift assays\",\n      \"pmids\": [\"14522989\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not resolve whether the TFIIF contact is direct or polymerase-conformation mediated\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrated in vivo error-prone transcription on RPB9 loss and mapped TCR and elongation to the shared Zn1/linker domains, establishing elongation competence as a prerequisite for the Rpb9 repair subpathway.\",\n      \"evidence\": \"In vivo fidelity assay with cDNA sequencing; domain-deletion UV repair and elongation assays; promoter-element mutagenesis\",\n      \"pmids\": [\"16492753\", \"17030604\", \"17023424\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular signal coupling elongation to repair not defined\", \"SAGA dependence of the subpathway not mechanistically explained\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Assigned the Zn2 domain a distinct role in UV-triggered Rpb1 ubiquitylation and proteasomal degradation, separating a damage-response function from the elongation/repair functions.\",\n      \"evidence\": \"UV irradiation, western blot for ubiquitylation/degradation, domain deletion, co-IP and proteasome inhibition\",\n      \"pmids\": [\"17452455\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The ubiquitin ligase recruited via Zn2 not identified\", \"Single-lab co-IP for Pol II interaction\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Provided a unified active-center mechanism: RPB9 delays NTP sequestration by acting on the trigger loop, controlling both misincorporation and error propagation and enabling TFIIS cleavage.\",\n      \"evidence\": \"Pre-steady state kinetics, NTP misincorporation and TFIIS cleavage assays, genetic synthetic lethality with rpb1 trigger-loop alleles\",\n      \"pmids\": [\"19439405\", \"24099331\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct structural contact between Rpb9 C-terminus and trigger loop not solved\", \"No effect on NTP selectivity leaves selection step unexplained\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Refined the active-center model to an indirect mechanism in which Rpb9 anchors Rpb1 helix α21 to modulate trigger-loop mobility, explaining its kinetic effects.\",\n      \"evidence\": \"Genetic suppressor screen, mutagenesis, in vitro elongation and misincorporation assays, α-amanitin epistasis\",\n      \"pmids\": [\"27226557\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Anchoring interaction inferred genetically/biochemically without a structure\", \"Quantitative contribution to in vivo fidelity unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Extended RPB9 function to small-RNA biogenesis, showing the C. elegans ortholog recruits the Integrator complex to drive piRNA gene termination and silencing.\",\n      \"evidence\": \"C. elegans knockout, co-IP for Integrator recruitment, genetic epistasis and piRNA sequencing\",\n      \"pmids\": [\"33533030\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether the Integrator-recruitment role is conserved beyond C. elegans untested\", \"Single-lab co-IP without reciprocal validation\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified a promoter-specific gene-regulatory role: Rpb9 activates ATG1/ULK1 transcription via Gcn4 to control autophagy, conserved to mammalian cells.\",\n      \"evidence\": \"KO library screen, ChIP for promoter binding, qRT-PCR, autophagy flux, mammalian knockdown\",\n      \"pmids\": [\"36102592\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How a core Pol II subunit confers gene-selective activation not explained\", \"Direct versus Gcn4-dependent recruitment not fully separated\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Linked Rpb9 to genome stability through DNA damage checkpoint activation and a synthetic dependence on histone H3 acetylation for double-strand break repair.\",\n      \"evidence\": \"Double-mutant analysis, checkpoint marker western blots, viability and chromosome segregation microscopy\",\n      \"pmids\": [\"29440683\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which Rpb9 supports checkpoint signaling unresolved\", \"Connection to its transcription/TCR roles not established\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Established an organismal requirement for POLR2I in vertebrate cardiac development, with mRNA rescue confirming specificity.\",\n      \"evidence\": \"Morpholino knockdown with mRNA rescue and cardiac functional/imaging readouts in zebrafish\",\n      \"pmids\": [\"41198546\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Which transcriptional function underlies the cardiac phenotype unknown\", \"Mitochondrial quality defect mechanistically uncharacterized\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how the distinct domain-specific activities of POLR2I (initiation, elongation fidelity, TCR, Rpb1 degradation, gene-selective activation) are coordinated within an intact organism and whether the conserved cardiac and autophagy roles reflect a single underlying transcriptional defect.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of human POLR2I within Pol II in the corpus\", \"Tissue-specific transcriptional targets in vertebrates undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [3, 13, 14]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [1, 18]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [7, 8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [1, 18]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [1, 3, 13]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [6, 9, 12]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [18]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [16]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [19]}\n    ],\n    \"complexes\": [\"RNA polymerase II\"],\n    \"partners\": [\"TFIIB\", \"TFIIF\", \"TFIIE\", \"TFIIS\", \"RPB1\", \"GCN4\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}