{"gene":"POLR2D","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":2004,"finding":"X-ray crystal structure of Rpb4/7 subcomplex determined at 2.3 Å resolution; combined with the 10-subunit Pol II core to refine a 3.8 Å atomic model of complete 12-subunit Pol II. Structural comparison revealed that core-Rpb4/7 interaction induces formation of an α-helix in the linker region of Rpb1 and folding of the Rpb7 tip loop. Details of the interface explain facilitated Rpb4/7 dissociation in a temperature-sensitive Pol II mutant.","method":"X-ray crystallography (2.3 Å for subcomplex, 3.8 Å for complete Pol II); structural comparison with core and free Rpb4/7","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structures with functional interpretation, replicated in multiple structural studies","pmids":["15591044"],"is_preprint":false},{"year":1989,"finding":"Deletion of RPB4 in S. cerevisiae produces heat- and cold-sensitive cells and markedly reduces RNA polymerase II activity in crude extracts in vitro, establishing that Rpb4 is required for normal Pol II activity especially at temperature extremes, though not essential for enzyme assembly.","method":"Gene deletion, in vitro RNA polymerase activity assay in crude extracts","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function with defined enzymatic and growth phenotype, foundational study replicated by multiple subsequent labs","pmids":["2674672"],"is_preprint":false},{"year":2001,"finding":"Crystal structure of the archaeal RPB4/7 homolog complex (Methanococcus jannaschii subunits E and F) determined; subunit E has an elongated two-domain structure with two potential RNA-binding motifs; subunit F wraps around one side of subunit E at the domain interface. A structural model was proposed in which the RNA-binding face of RPB7 is positioned to interact with the nascent RNA transcript.","method":"X-ray crystallography of archaeal E/F complex","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional model, consistent with subsequent biochemical and structural studies","pmids":["11741548"],"is_preprint":false},{"year":2000,"finding":"Purified yeast Rpb4/7 heterodimer binds single-stranded DNA and RNA via an OB-fold motif in Rpb7. A deletion in the putative OB-fold nucleic acid-binding surface of Rpb7 abolished binding without affecting Rpb4/7 complex stability or its association with polymerase, yet destroyed transcription activity. Rpb4/7 is required for a post-recruitment step in transcription initiation, not for stable promoter binding.","method":"Template competition assay, purified Rpb4/7 single-strand nucleic acid-binding assay, Rpb7 deletion mutagenesis, in vitro transcription reconstitution","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with mutagenesis and multiple functional assays in one rigorous study","pmids":["11087726"],"is_preprint":false},{"year":2005,"finding":"Crystal structure of human Rpb4/Rpb7 heterodimer determined at 2.7 Å. Site-directed mutagenesis of conserved solvent-exposed residues in the Rpb7 OB-fold (including the B4-B5 loop) identified an elongated surface region involved in RNA binding, confirmed by EMSA. The homologous archaeal E subunit uses the same surface for RNA binding.","method":"X-ray crystallography (2.7 Å), site-directed mutagenesis, electrophoretic mobility shift assay (EMSA)","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with mutagenesis and biochemical RNA-binding assays in one study","pmids":["16282592"],"is_preprint":false},{"year":1998,"finding":"3D EM structure of wild-type yeast Pol II located Rpb4 and Rpb7 at the floor of the DNA-binding cleft. Surface plasmon resonance showed that Rpb4/7 stabilize a minimal pre-initiation complex (promoter DNA, TBP, TFIIB, Pol II), suggesting a role in coupling DNA entry into the cleft to cleft closure during promoter-specific transcription.","method":"3D electron microscopy, difference mapping, surface plasmon resonance","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — structural localization plus biophysical interaction assay (SPR), single lab but two orthogonal methods","pmids":["9545247"],"is_preprint":false},{"year":2002,"finding":"Rpb4 plays a dual role in transcription-coupled DNA repair (TCR) in S. cerevisiae: it suppresses the Rpb9-dependent TCR subpathway and facilitates the Rad26-dependent TCR subpathway, demonstrating a regulatory function of Rpb4 in selecting between TCR subpathways.","method":"Genetic epistasis analysis using deletion mutants (rpb4Δ, rpb9Δ, rad26Δ combinations); repair assays","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with multiple double/triple mutant combinations providing clear pathway placement","pmids":["12411509"],"is_preprint":false},{"year":2002,"finding":"In S. pombe, Fcp1 CTD-phosphatase directly interacts with the Rpb4 subunit of Pol II, identified by chemical cross-linking, GST pulldown, and affinity chromatography. Repression of rpb4 expression reduced Fcp1 in the Pol II complex and increased CTD phosphorylation, demonstrating that Rpb4 is required for Fcp1/TFIIF/Pol II complex formation in vivo.","method":"Immunoaffinity purification, chemical cross-linking, GST pulldown, affinity chromatography, rpb4 shut-off strain","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal biochemical methods (cross-linking, pulldown, affinity chromatography) plus in vivo genetic manipulation","pmids":["11839823"],"is_preprint":false},{"year":1998,"finding":"Rpb4 is required for Pol II enzymatic activity at temperature extremes (10°C and 35°C) but not at moderate temperature (23°C). Addition of recombinant Rpb4 produced in E. coli rescues Pol II activity in extracts from postlogarithmic cells at non-optimal temperatures. Sucrose gradient and immunoprecipitation showed Rpb4 is present in excess over the Pol II complex, and only Pol II from postlogarithmic cells can be rescued, suggesting Pol II must be modified to recruit Rpb4.","method":"In vitro promoter-independent transcription assay in cell extracts, recombinant Rpb4 complementation, sucrose gradient sedimentation, immunoprecipitation","journal":"Journal of bacteriology","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro enzymatic assay with recombinant protein complementation and multiple supporting methods","pmids":["9829926"],"is_preprint":false},{"year":1999,"finding":"Rpb7 can interact with Pol II and support transcription independently of Rpb4 when overexpressed, but fewer Rpb7 molecules associate with Pol II lacking Rpb4 than with wild-type Pol II. Reciprocal coimmunoprecipitation confirmed stable interaction of overproduced Rpb7 with Pol IIΔ4. A major role of Rpb4 is to augment Rpb7 binding to Pol II.","method":"RPB7 overexpression suppressor screen, reciprocal coimmunoprecipitation","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus genetic suppression analysis, single lab","pmids":["10082533"],"is_preprint":false},{"year":2003,"finding":"A conditional mutation in the shared Rpb6 subunit (Q100R) causes selective loss of Rpb4 and Rpb7 from purified RNA Pol II. Interaction experiments demonstrated a direct association between Rpb6 and Rpb4, identifying Rpb6 as one contact point between the Rpb4/7 subcomplex and Pol II.","method":"Conditional rpb6 mutagenesis, Pol II purification, protein interaction assays","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct interaction demonstrated biochemically with genetic confirmation, single lab","pmids":["12697831"],"is_preprint":false},{"year":2008,"finding":"Chromatin immunoprecipitation of Rpb4 showed it crosslinks throughout transcribed regions genome-wide. Loss of Rpb4 reduces Pol II levels near 3' ends of mRNA genes, decreases cotranscriptional recruitment of 3'-end processing factors, and alters polyadenylation site usage at the RNA14 gene, establishing that Rpb4 contributes to cotranscriptional 3'-end processing.","method":"Chromatin immunoprecipitation (ChIP), rpb4Δ strain analysis, polyadenylation site mapping","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP with loss-of-function and defined molecular phenotype, single lab","pmids":["18195044"],"is_preprint":false},{"year":2008,"finding":"Genome-wide ChIP coupled to tiling microarray analysis showed that Rpb7 occupancy profiles across the genome are essentially identical to core subunit Rpb3, demonstrating that complete Pol II (including Rpb4/7) associates with DNA in vivo throughout the transcription cycle.","method":"Chromatin immunoprecipitation coupled to high-resolution tiling microarray (ChIP-chip)","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genome-wide ChIP-chip with quantitative comparison, single lab","pmids":["18667430"],"is_preprint":false},{"year":2013,"finding":"Quantitative proteomics showed that Rpb4/7 dissociate from RNAPII upon interaction with specific transcriptional elongation-associated proteins recruited to the hyperphosphorylated CTD. RNAPII isolated through Rpb7 is depleted in Ser2 CTD phosphorylation, indicating Rpb4/7 are dispensable during specific elongation stages.","method":"Quantitative mass spectrometry proteomics, co-immunoprecipitation with phospho-CTD isoforms","journal":"Molecular & cellular proteomics : MCP","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — quantitative proteomics with multiple conditions, single lab","pmids":["23418395"],"is_preprint":false},{"year":2014,"finding":"Metabolic RNA labeling and dynamic transcriptome analysis showed Rpb4 deletion causes a drastic defect in mRNA synthesis compensated by down-regulation of mRNA degradation (mRNA buffering). Covalent fusion of Rpb4 to Pol II core subunit Rpb2 largely restores mRNA synthesis and degradation defects, demonstrating that Rpb4 functions primarily in nuclear mRNA synthesis by Pol II.","method":"Metabolic RNA labeling, comparative dynamic transcriptome analysis, Rpb2-Rpb4 fusion protein complementation, rpb4Δ strain","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (metabolic labeling, transcriptome analysis, fusion protein rescue) establishing primary nuclear function","pmids":["24802753"],"is_preprint":false},{"year":2014,"finding":"Deletion of RPB4 or disruption of Rpb4/7 integrity increased phosphorylation of CTD residues Ser2, Ser5, Ser7, and Thr4 of Rpb1. Genetic interactions were found with CTD phosphatases SSU72 and FCP1. Rpb4 is important for association and recruitment of Ssu72 (Ser5P phosphatase) and Fcp1 (Ser2P/Thr4P phosphatase) to the CTD, placing Rpb4/7 as a facilitator of CTD dephosphorylation.","method":"rpb4Δ strain phospho-CTD analysis, genetic interaction screens, phosphatase recruitment assays (ChIP)","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple genetic and biochemical approaches, single lab","pmids":["25416796"],"is_preprint":false},{"year":2014,"finding":"The Ccr4-Not complex requires the Rpb4/7 module of Pol II to associate with elongation complexes and stimulate Pol II elongation; loss of Rpb4/7 impairs Ccr4-Not-dependent reactivation of arrested elongation complexes.","method":"In vitro elongation assays with purified Ccr4-Not complex, rpb4/7 deletion strains","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro elongation assay plus genetic analysis, single lab","pmids":["25315781"],"is_preprint":false},{"year":2019,"finding":"3C analysis showed that gene loop formation is abolished in rpb4Δ cells. RPB4 overexpression rescued gene looping and transcription termination defects of sua7-1 (TFIIB mutant) and ssu72-2, while SSU72 overexpression restored gene loops in rpb4Δ cells. Rpb4 facilitates the TFIIB-Ssu72 interaction required for gene loop formation, promoting Pol II transfer from terminator to promoter for transcription reinitiation.","method":"Chromosome conformation capture (3C) assay, genetic suppression analysis, rpb4Δ strain","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — 3C with multiple genetic suppression experiments, single lab","pmids":["31304538"],"is_preprint":false},{"year":2009,"finding":"Using wholly recombinant archaeal RNAP, the F/E complex (RPB4/7 homolog) greatly stimulates RNAP processivity, enhances full-length product formation, reduces pausing, and increases termination at weak termination signals during elongation. F/E mutants defective in RNA binding show reduced stimulatory activity, implicating F/E–RNA interactions as pivotal for elongation and termination.","method":"In vitro transcription assay with recombinant archaeal RNAP; F/E mutant variants on synthetic nucleic acid scaffolds","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Moderate — wholly recombinant in vitro reconstitution with RNA-binding mutants, single lab but rigorous biochemical analysis","pmids":["19906731"],"is_preprint":false},{"year":2001,"finding":"Rpb4 is required for activated transcription from a subset of promoters in S. cerevisiae; constitutive transcription is largely unaffected. The C-terminal 24 amino acids of Rpb4 are critical for this activation function. Transcriptional activation by artificial TBP recruitment is also defective without Rpb4.","method":"rpb4Δ strain, promoter-reporter assays, domain deletion analysis, TBP recruitment assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined promoter-specific phenotype and domain localization, single lab","pmids":["11382749"],"is_preprint":false},{"year":2007,"finding":"Pulldown and complementation assays identified two crucial contact points for Rpb4/7 subcomplex association with the Pol II core: the N-terminal RNP-like domain of Rpb7 and the partially ordered N-terminal region of Rpb4 (interacting with Rpb2). Mutations in Rpb7's N-terminal domain increase dependence on Rpb4 for polymerase interaction.","method":"RNA polymerase pulldown assay, complementation analysis, mutagenesis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pulldown and complementation with mutagenesis, single lab","pmids":["18056993"],"is_preprint":false},{"year":2021,"finding":"Rpb4/7 undergoes more than 100 combinations of post-translational modifications (PTMs); the PTM repertoire changes as the mRNA/Rpb4/7 complex progresses through stages of the mRNA life cycle (transcription, export, translation, decay). Specific PTM mutants affect Rpb4 interactions with key regulators (Pol II, eIF3, Pat1) and disrupt mRNA synthesis/decay buffering.","method":"Mass spectrometry-based PTM mapping, PTM mutant functional analysis, interaction assays","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS-based PTM identification combined with functional mutant analysis, single lab","pmids":["33440147"],"is_preprint":false},{"year":2018,"finding":"Rpb4-Rpb2 fusion protein supports normal transcription but adversely affects mRNA decay, cell proliferation, and stress response, demonstrating that dissociation of Rpb4 from Pol II is required for its cytoplasmic roles in mRNA decay regulation. A portion of the fusion protein is proteolytically cleaved to release free functional Rpb4 that binds mRNAs and polysomes.","method":"Rpb2-Rpb4 fusion protein expression, mRNA decay assays, polysome association, stress response assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — fusion protein dissociation assay with multiple functional readouts, single lab","pmids":["30359412"],"is_preprint":false},{"year":2009,"finding":"In S. pombe, Med8 mediator subunit interacts with Rpb4, and Ace2 transcriptional activator interacts with Med8; the C-terminal region of Med8 is required for its interaction with Rpb4. This defines a protein interaction chain (Ace2–Med8–Rpb4) that relays transcriptional regulatory signals to Pol II during cell separation.","method":"Yeast two-hybrid, co-immunoprecipitation, domain deletion analysis","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — two-hybrid and Co-IP with domain delineation, single lab","pmids":["19720063"],"is_preprint":false},{"year":2008,"finding":"Genome-wide ChIP-chip analysis showed Rpb4 is recruited to coding regions of most transcriptionally active genes with extent increasing with gene length. Pol II lacking Rpb4 is defective in transcribing long, GC-rich transcription units, and rpb4Δ cells are sensitive to 6-azauracil, establishing a role for Rpb4 in transcription elongation that is independent of Rpb7.","method":"ChIP-chip (genome-wide chromatin immunoprecipitation with microarray), 6-azauracil sensitivity assay, rpb4Δ strain","journal":"Eukaryotic cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genome-wide ChIP with functional phenotype, single lab","pmids":["18441121"],"is_preprint":false},{"year":2022,"finding":"Binary complementation assays revealed an interaction between the N-terminal third domain of influenza PB2 and human RPB4. This interaction was confirmed by co-immunoprecipitation and was found with influenza A, B, and C FluPols. The N-half domain of RPB4 is critical for this interaction. PB2 mutants at conserved positions showed strong transcriptional activity defects, suggesting FluPol uses RPB4 to position itself near the 5'-end of nascent host mRNA during cap-snatching.","method":"Binary complementation assay, co-immunoprecipitation, PB2 mutagenesis","journal":"Viruses","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — reciprocal interaction confirmed by two methods with functional mutagenesis, single lab","pmids":["35336925"],"is_preprint":false},{"year":2022,"finding":"RTR1 deletion increases the amount of chromatin-associated Pol II lacking Rpb4, decreases Rpb4-mRNA imprinting, and consequently increases mRNA stability. Rtr1 (CTD Ser5P phosphatase) mediates proper association of Rpb4/7 with Pol II during assembly, linking CTD phosphorylation state to Rpb4/7 incorporation and downstream mRNA decay regulation.","method":"RTR1 deletion strain, Pol II assembly analysis, ChIP, mRNA stability assays","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function with multiple biochemical readouts, single lab","pmids":["35216121"],"is_preprint":false},{"year":2020,"finding":"RIP-Seq showed Rpb4 associates genome-wide with more than 1400 mRNA targets. Rpb4 and Puf3 RNA-binding protein physically interact, genetically interact, and co-regulate mRNA stability of a shared set of transcripts. Rpb4-mRNA association depends on Puf3 and vice versa. Puf3 associates with chromatin in an Rpb4-dependent manner, establishing a co-transcriptional imprinting mechanism.","method":"RIP-Seq, co-immunoprecipitation, genetic interaction analysis, ChIP","journal":"RNA biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (RIP-Seq, Co-IP, ChIP, genetics) in a single lab study","pmids":["33094674"],"is_preprint":false},{"year":2016,"finding":"RPB1 foot mutations that impair Rpb4/7 assembly into Pol II activate an environmental stress response (ESR) under optimal growth conditions primarily through post-transcriptional regulation dependent on Rpb4-mRNA imprinting, revealing that Rpb4 globally modulates mRNA stability and coordinates transcription with mRNA decay.","method":"RPB1 foot mutant strains, global transcriptional analysis, mRNA stability assays, Rpb4/7 assembly analysis","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Pol II assembly mutants with global transcriptome and mRNA decay analysis, single lab","pmids":["27001033"],"is_preprint":false}],"current_model":"POLR2D (Rpb4) is a dissociable subunit of RNA polymerase II that forms a stable heterodimer with Rpb7 (Rpb4/7), docking onto the Pol II core through contacts with Rpb2 and Rpb6; structurally, Rpb4/7 positions an RNA-binding OB-fold near the RNA exit groove to stabilize the nascent transcript, stimulate transcription initiation (post-recruitment step), elongation processivity, and termination; Rpb4 facilitates CTD dephosphorylation by recruiting Ssu72 and Fcp1 phosphatases, promotes cotranscriptional recruitment of 3'-end processing factors, enables gene loop formation via stabilizing the TFIIB-Ssu72 interaction, and is required for transcription-coupled DNA repair through dual regulation of the Rpb9 and Rad26 TCR subpathways; beyond transcription, Rpb4 is co-transcriptionally loaded onto mRNAs ('imprinting'), accompanies them to the cytoplasm where—regulated by an extensive set of post-translational modifications—it coordinates mRNA export, translation, and decay by interacting with factors such as eIF3 and Pat1, thereby coupling nuclear mRNA synthesis to cytoplasmic mRNA stability."},"narrative":{"mechanistic_narrative":"POLR2D (Rpb4) is a dissociable subunit of RNA polymerase II that, together with Rpb7, forms a heterodimeric subcomplex docking onto the polymerase core and serving as a hub that couples nuclear transcription to cytoplasmic mRNA fate [PMID:15591044, PMID:24802753]. The Rpb4/7 subcomplex contacts the core through the N-terminal RNP-like domain of Rpb7 and the N-terminal region of Rpb4 (which engages Rpb2), with Rpb6 providing an additional docking point; Rpb4 augments Rpb7 association with the polymerase, and a major contribution of the module is to position an OB-fold RNA-binding surface near the nascent transcript [PMID:11087726, PMID:16282592, PMID:18056993, PMID:12697831, PMID:10082533]. Functionally, Rpb4/7 stabilizes the pre-initiation complex and is required for a post-recruitment step in initiation, supports elongation through long GC-rich units, and stimulates processivity, pausing suppression, and termination via direct RNA contacts [PMID:9545247, PMID:11087726, PMID:18441121, PMID:19906731]. Rpb4 facilitates CTD dephosphorylation by promoting recruitment of the Ssu72 and Fcp1 phosphatases, enables gene loop formation by stabilizing the TFIIB–Ssu72 interaction to recycle Pol II for reinitiation, and supports cotranscriptional 3'-end processing and selection between transcription-coupled DNA repair subpathways [PMID:25416796, PMID:11839823, PMID:31304538, PMID:18195044, PMID:12411509]. Metabolic labeling and Rpb4–Rpb2 fusion rescue establish that Rpb4 acts primarily in nuclear mRNA synthesis, but the protein is also co-transcriptionally loaded onto mRNAs ('imprinting') and, upon dissociation, accompanies them to the cytoplasm where—regulated by an extensive PTM repertoire and acting through partners such as Puf3 and Pat1—it globally coordinates mRNA stability and decay to buffer mRNA levels against changes in synthesis [PMID:24802753, PMID:30359412, PMID:33094674, PMID:33440147, PMID:27001033]. Deletion of RPB4 in yeast produces heat- and cold-sensitive growth and reduced Pol II activity at temperature extremes [PMID:2674672]; no human Mendelian disease connection is described in the available corpus.","teleology":[{"year":1989,"claim":"Established that Rpb4 is a non-essential but functionally important Pol II subunit by showing its loss impairs polymerase activity and growth at temperature extremes.","evidence":"RPB4 gene deletion and in vitro Pol II activity assays in yeast crude extracts","pmids":["2674672"],"confidence":"High","gaps":["Did not define the molecular step Rpb4 affects","Mechanism of temperature sensitivity unresolved"]},{"year":1998,"claim":"Localized Rpb4/7 to the Pol II cleft and showed it stabilizes the pre-initiation complex, linking the subunit to initiation rather than catalysis alone.","evidence":"3D EM difference mapping and surface plasmon resonance on yeast Pol II/PIC; in vitro complementation with recombinant Rpb4","pmids":["9545247","9829926"],"confidence":"High","gaps":["Did not identify the RNA-contacting surface","Nature of the postlogarithmic Pol II modification enabling Rpb4 recruitment unknown"]},{"year":2000,"claim":"Defined the mechanistic basis of Rpb4/7 action by showing the Rpb7 OB-fold binds single-stranded nucleic acid and is required for a post-recruitment initiation step, separating nucleic-acid binding from complex assembly.","evidence":"Purified Rpb4/7 nucleic-acid binding, OB-fold deletion mutagenesis, and in vitro transcription reconstitution","pmids":["11087726"],"confidence":"High","gaps":["Did not resolve the exact post-recruitment step in vivo","Genome-wide relevance not yet established"]},{"year":2001,"claim":"Resolved how the Rpb4/7 dimer is organized and how its RNA-binding face is oriented, providing a structural model for nascent transcript engagement, and showed promoter-selective and activation roles for Rpb4.","evidence":"X-ray structure of the archaeal E/F homolog; rpb4Δ promoter-reporter and domain-deletion assays in yeast","pmids":["11741548","11382749"],"confidence":"High","gaps":["Archaeal model required validation in eukaryotic Pol II","Which activators depend on Rpb4 C-terminus not enumerated"]},{"year":2002,"claim":"Connected Rpb4 to CTD phosphatase recruitment and to transcription-coupled DNA repair, broadening its role to post-elongation regulation.","evidence":"Fcp1–Rpb4 cross-linking/pulldown with rpb4 shut-off in S. pombe; genetic epistasis of rpb4Δ/rpb9Δ/rad26Δ TCR mutants","pmids":["11839823","12411509"],"confidence":"High","gaps":["Direct phosphatase recruitment mechanism not structurally defined","How Rpb4 discriminates between TCR subpathways unresolved"]},{"year":2005,"claim":"Provided the human Rpb4/Rpb7 structure and mapped the conserved RNA-binding surface, confirming evolutionary conservation of the OB-fold mechanism.","evidence":"X-ray crystallography of human Rpb4/7 at 2.7 Å with site-directed mutagenesis and EMSA","pmids":["16282592"],"confidence":"High","gaps":["Human in vivo functions not tested here","RNA specificity determinants not defined"]},{"year":2004,"claim":"Defined the atomic interface between Rpb4/7 and the Pol II core, explaining how core contact induces conformational changes and how dissociation occurs.","evidence":"X-ray structures of Rpb4/7 (2.3 Å) and the complete 12-subunit Pol II (3.8 Å) with comparative structural analysis","pmids":["15591044"],"confidence":"High","gaps":["Dynamics of regulated dissociation in vivo not captured","PTM influence on the interface not addressed"]},{"year":2003,"claim":"Identified Rpb6 and the Rpb7 N-terminal RNP domain plus the Rpb4 N-terminus as the physical anchors of the subcomplex on the core, and showed Rpb4 augments Rpb7 incorporation.","evidence":"Conditional rpb6 mutagenesis and direct interaction assays; RPB7 overexpression suppression with reciprocal Co-IP; pulldown/complementation mapping","pmids":["12697831","10082533","18056993"],"confidence":"Medium","gaps":["Relative contribution of each contact to assembly kinetics not quantified","Single-lab interaction data"]},{"year":2008,"claim":"Showed genome-wide that complete Pol II including Rpb4/7 traverses transcribed regions and that Rpb4 contributes to elongation of long genes and to cotranscriptional 3'-end processing.","evidence":"ChIP and ChIP-chip of Rpb4/Rpb7 vs Rpb3 in yeast; rpb4Δ poly(A) site mapping and 6-azauracil sensitivity","pmids":["18195044","18667430","18441121"],"confidence":"Medium","gaps":["Mechanism coupling Rpb4 to 3'-end factor recruitment not biochemically reconstituted","Single-lab genome-wide datasets"]},{"year":2009,"claim":"Demonstrated directly that the Rpb4/7 homolog stimulates elongation processivity and termination through RNA binding, and placed Rpb4 in a mediator-relayed regulatory chain.","evidence":"Recombinant archaeal RNAP in vitro transcription with F/E RNA-binding mutants; Ace2–Med8–Rpb4 two-hybrid and Co-IP in S. pombe","pmids":["19906731","19720063"],"confidence":"High","gaps":["Archaeal elongation findings need eukaryotic confirmation","Mediator chain shown only for cell-separation genes"]},{"year":2013,"claim":"Showed Rpb4/7 dissociates from Pol II at specific elongation stages tied to CTD phosphorylation state, refining when the module is functionally engaged.","evidence":"Quantitative mass spectrometry and Co-IP across phospho-CTD isoforms","pmids":["23418395"],"confidence":"Medium","gaps":["Functional consequence of dissociation at elongation not directly tested here","Single-lab proteomics"]},{"year":2014,"claim":"Established that Rpb4's primary role is in nuclear mRNA synthesis and that it facilitates CTD dephosphorylation and Ccr4-Not-dependent elongation, while coupling synthesis to mRNA decay via buffering.","evidence":"Metabolic RNA labeling with Rpb2-Rpb4 fusion rescue; rpb4Δ phospho-CTD analysis with SSU72/FCP1 genetics; in vitro Ccr4-Not elongation assays","pmids":["24802753","25416796","25315781"],"confidence":"High","gaps":["Structural basis for phosphatase recruitment unresolved","How nuclear synthesis defect signals to cytoplasmic decay not fully mapped"]},{"year":2016,"claim":"Linked Rpb4/7 assembly into Pol II to global post-transcriptional control, showing imprinting-dependent modulation of mRNA stability and stress responses.","evidence":"RPB1 foot mutants impairing Rpb4/7 assembly with global transcriptome and mRNA stability analysis","pmids":["27001033"],"confidence":"Medium","gaps":["Direct imprinting mechanism on individual transcripts not resolved here","Single-lab study"]},{"year":2018,"claim":"Demonstrated that physical dissociation of Rpb4 from Pol II is required for its cytoplasmic mRNA-decay functions, distinguishing nuclear from cytoplasmic roles.","evidence":"Rpb2-Rpb4 fusion expression with mRNA decay, polysome association, and stress-response assays in yeast","pmids":["30359412"],"confidence":"Medium","gaps":["Proteolytic release mechanism not fully characterized","Single-lab study"]},{"year":2020,"claim":"Identified the co-transcriptional imprinting machinery, showing Rpb4 and Puf3 mutually depend on each other to load onto mRNAs and co-regulate transcript stability.","evidence":"RIP-Seq, Co-IP, ChIP, and genetic interaction analysis of Rpb4 and Puf3 in yeast","pmids":["33094674"],"confidence":"Medium","gaps":["Generality beyond Puf3-bound transcripts unknown","Single-lab dataset"]},{"year":2021,"claim":"Revealed that a stage-specific PTM code on Rpb4/7 regulates its interactions with Pol II, eIF3, and Pat1 to control its progression through the mRNA life cycle.","evidence":"Mass spectrometry PTM mapping with PTM-mutant functional and interaction analysis","pmids":["33440147"],"confidence":"Medium","gaps":["Enzymes writing/erasing individual PTMs not identified","Causal ordering of PTM transitions not established"]},{"year":2022,"claim":"Defined an upstream determinant (Rtr1 CTD phosphatase) of Rpb4/7 incorporation and identified RPB4 as a host target hijacked by influenza polymerase, extending its mechanistic reach.","evidence":"RTR1 deletion with Pol II assembly/ChIP and mRNA stability assays; binary complementation and Co-IP of influenza PB2 with human RPB4 plus PB2 mutagenesis","pmids":["35216121","35336925"],"confidence":"Medium","gaps":["Structural details of the FluPol–RPB4 interaction not resolved","How Rtr1 mechanistically couples CTD state to assembly not defined"]},{"year":null,"claim":"How the Rpb4/7 PTM code and assembly state are integrated in metazoan cells, and whether POLR2D dysfunction underlies human disease, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No human in vivo functional study in the corpus","No Mendelian disease link characterized","Most mechanistic detail derives from yeast and archaeal systems"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[3,4,18,27]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[3]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,5,20]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[3,15,18]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[11,12,24]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[22,27]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[1,3,5,14,24]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[14,22,27,28]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[6]}],"complexes":["RNA polymerase II","Rpb4/7 subcomplex"],"partners":["POLR2G","POLR2B","POLR2F","FCP1","SSU72","PUF3","PAT1","EIF3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O15514","full_name":"DNA-directed RNA polymerase II subunit RPB4","aliases":["DNA-directed RNA polymerase II subunit D","RNA polymerase II 16 kDa subunit","RPB16"],"length_aa":142,"mass_kda":16.3,"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. POLR2D/RPB4 is part of a subcomplex with POLR2G/RPB7 that binds to a pocket formed by POLR2A/RPB1, POLR2B/RPB2 and POLR2F/RPABC2 at the base of the clamp element. The POLR2D/RPB4-POLR2G/RPB7 subcomplex seems to lock the clamp via POLR2G/RPB7 in the closed conformation thus preventing double-stranded DNA to enter the active site cleft. The POLR2D/RPB4-POLR2G/RPB7 subcomplex binds single-stranded DNA and RNA","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/O15514/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/POLR2D","classification":"Common Essential","n_dependent_lines":1208,"n_total_lines":1208,"dependency_fraction":1.0},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000144231","cell_line_id":"CID000699","localizations":[{"compartment":"nucleoplasm","grade":3},{"compartment":"cytoplasmic","grade":2}],"interactors":[{"gene":"MED14","stoichiometry":10.0},{"gene":"MED19","stoichiometry":10.0},{"gene":"POLR2A","stoichiometry":10.0},{"gene":"POLR2B","stoichiometry":10.0},{"gene":"POLR2C","stoichiometry":10.0},{"gene":"POLR2G","stoichiometry":10.0},{"gene":"POLR2E","stoichiometry":10.0},{"gene":"POLR2K","stoichiometry":10.0},{"gene":"POLR2F","stoichiometry":10.0},{"gene":"POLR2H","stoichiometry":10.0}],"url":"https://opencell.sf.czbiohub.org/target/CID000699","total_profiled":1310},"omim":[{"mim_id":"609881","title":"RNA POLYMERASE II, SUBUNIT J2; POLR2J2","url":"https://www.omim.org/entry/609881"},{"mim_id":"606121","title":"CGRP RECEPTOR COMPONENT; CRCP","url":"https://www.omim.org/entry/606121"},{"mim_id":"606017","title":"POLYMERASE II, RNA, SUBUNIT D; POLR2D","url":"https://www.omim.org/entry/606017"},{"mim_id":"602013","title":"POLYMERASE II, RNA, SUBUNIT G; POLR2G","url":"https://www.omim.org/entry/602013"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Nuclear speckles","reliability":"Supported"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"testis","ntpm":69.5}],"url":"https://www.proteinatlas.org/search/POLR2D"},"hgnc":{"alias_symbol":["RPB4"],"prev_symbol":[]},"alphafold":{"accession":"O15514","domains":[{"cath_id":"-","chopping":"33-50_57-70","consensus_level":"high","plddt":96.8538,"start":33,"end":70},{"cath_id":"1.20.1250.40","chopping":"76-139","consensus_level":"high","plddt":95.5552,"start":76,"end":139}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O15514","model_url":"https://alphafold.ebi.ac.uk/files/AF-O15514-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O15514-F1-predicted_aligned_error_v6.png","plddt_mean":91.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=POLR2D","jax_strain_url":"https://www.jax.org/strain/search?query=POLR2D"},"sequence":{"accession":"O15514","fasta_url":"https://rest.uniprot.org/uniprotkb/O15514.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O15514/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O15514"}},"corpus_meta":[{"pmid":"15591044","id":"PMC_15591044","title":"Structures of complete RNA polymerase II and its subcomplex, Rpb4/7.","date":"2004","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15591044","citation_count":187,"is_preprint":false},{"pmid":"2674672","id":"PMC_2674672","title":"RNA polymerase II subunit RPB4 is essential for high- and low-temperature yeast cell growth.","date":"1989","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/2674672","citation_count":166,"is_preprint":false},{"pmid":"19204117","id":"PMC_19204117","title":"NRPD4, a protein related to the RPB4 subunit of RNA polymerase II, is a component of RNA polymerases IV and V and is required for RNA-directed DNA methylation.","date":"2009","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/19204117","citation_count":116,"is_preprint":false},{"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":"11741548","id":"PMC_11741548","title":"Structure of an archaeal homolog of the eukaryotic RNA polymerase II RPB4/RPB7 complex.","date":"2001","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/11741548","citation_count":90,"is_preprint":false},{"pmid":"15544954","id":"PMC_15544954","title":"Rpb4 and Rpb7: subunits of RNA polymerase II and beyond.","date":"2004","source":"Trends in biochemical sciences","url":"https://pubmed.ncbi.nlm.nih.gov/15544954","citation_count":87,"is_preprint":false},{"pmid":"11839823","id":"PMC_11839823","title":"Formation of a carboxy-terminal domain phosphatase (Fcp1)/TFIIF/RNA polymerase II (pol II) complex in Schizosaccharomyces pombe involves direct interaction between Fcp1 and the Rpb4 subunit of pol II.","date":"2002","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/11839823","citation_count":83,"is_preprint":false},{"pmid":"11087726","id":"PMC_11087726","title":"Dissociable Rpb4-Rpb7 subassembly of rna polymerase II binds to single-strand nucleic acid and mediates a post-recruitment step in transcription initiation.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11087726","citation_count":73,"is_preprint":false},{"pmid":"18195044","id":"PMC_18195044","title":"The Rpb4 subunit of RNA polymerase II contributes to cotranscriptional recruitment of 3' processing factors.","date":"2008","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/18195044","citation_count":63,"is_preprint":false},{"pmid":"16282592","id":"PMC_16282592","title":"Crystal structure and RNA binding of the Rpb4/Rpb7 subunits of human RNA polymerase II.","date":"2005","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/16282592","citation_count":59,"is_preprint":false},{"pmid":"9545247","id":"PMC_9545247","title":"Structure of wild-type yeast RNA polymerase II and location of Rpb4 and Rpb7.","date":"1998","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/9545247","citation_count":56,"is_preprint":false},{"pmid":"9829926","id":"PMC_9829926","title":"Rpb4, a subunit of RNA polymerase II, enables the enzyme to transcribe at temperature extremes in vitro.","date":"1998","source":"Journal of bacteriology","url":"https://pubmed.ncbi.nlm.nih.gov/9829926","citation_count":53,"is_preprint":false},{"pmid":"10082533","id":"PMC_10082533","title":"Rpb7 can interact with RNA polymerase II and support transcription during some stresses independently of Rpb4.","date":"1999","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/10082533","citation_count":53,"is_preprint":false},{"pmid":"19906731","id":"PMC_19906731","title":"Molecular mechanisms of RNA polymerase--the F/E (RPB4/7) complex is required for high processivity in vitro.","date":"2009","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/19906731","citation_count":48,"is_preprint":false},{"pmid":"11058130","id":"PMC_11058130","title":"Archaeal RNA polymerase subunits F and P are bona fide homologs of eukaryotic RPB4 and RPB12.","date":"2000","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/11058130","citation_count":47,"is_preprint":false},{"pmid":"10523639","id":"PMC_10523639","title":"The Rpb4 subunit of fission yeast Schizosaccharomyces pombe RNA polymerase II is essential for cell viability and similar in structure to the corresponding subunits of higher eukaryotes.","date":"1999","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/10523639","citation_count":47,"is_preprint":false},{"pmid":"12407181","id":"PMC_12407181","title":"The A14-A43 heterodimer subunit in yeast RNA pol I and their relationship to Rpb4-Rpb7 pol II subunits.","date":"2002","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/12407181","citation_count":43,"is_preprint":false},{"pmid":"25974617","id":"PMC_25974617","title":"Contribution of PRS3, RPB4 and ZWF1 to the resistance of industrial Saccharomyces cerevisiae CCUG53310 and PE-2 strains to lignocellulosic hydrolysate-derived inhibitors.","date":"2015","source":"Bioresource technology","url":"https://pubmed.ncbi.nlm.nih.gov/25974617","citation_count":42,"is_preprint":false},{"pmid":"8407810","id":"PMC_8407810","title":"A growth rate-limiting process in the last growth phase of the yeast life cycle involves RPB4, a subunit of RNA polymerase II.","date":"1993","source":"Journal of bacteriology","url":"https://pubmed.ncbi.nlm.nih.gov/8407810","citation_count":39,"is_preprint":false},{"pmid":"12482973","id":"PMC_12482973","title":"An Rpb4/Rpb7-like complex in yeast RNA polymerase III contains the orthologue of mammalian CGRP-RCP.","date":"2003","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/12482973","citation_count":38,"is_preprint":false},{"pmid":"18667430","id":"PMC_18667430","title":"Genome-associated RNA polymerase II includes the dissociable Rpb4/7 subcomplex.","date":"2008","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/18667430","citation_count":38,"is_preprint":false},{"pmid":"23418395","id":"PMC_23418395","title":"Quantitative proteomics demonstrates that the RNA polymerase II subunits Rpb4 and Rpb7 dissociate during transcriptional elongation.","date":"2013","source":"Molecular & cellular proteomics : MCP","url":"https://pubmed.ncbi.nlm.nih.gov/23418395","citation_count":37,"is_preprint":false},{"pmid":"24802753","id":"PMC_24802753","title":"Rpb4 subunit functions mainly in mRNA synthesis by RNA polymerase II.","date":"2014","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/24802753","citation_count":34,"is_preprint":false},{"pmid":"31304538","id":"PMC_31304538","title":"RNA polymerase II plays an active role in the formation of gene loops through the Rpb4 subunit.","date":"2019","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/31304538","citation_count":34,"is_preprint":false},{"pmid":"11382749","id":"PMC_11382749","title":"Rpb4, a non-essential subunit of core RNA polymerase II of Saccharomyces cerevisiae is important for activated transcription of a subset of genes.","date":"2001","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11382749","citation_count":33,"is_preprint":false},{"pmid":"16036568","id":"PMC_16036568","title":"Rpb4 and Rpb7: a sub-complex integral to multi-subunit RNA polymerases performs a multitude of functions.","date":"2005","source":"IUBMB life","url":"https://pubmed.ncbi.nlm.nih.gov/16036568","citation_count":31,"is_preprint":false},{"pmid":"12697831","id":"PMC_12697831","title":"Loss of the Rpb4/Rpb7 subcomplex in a mutant form of the Rpb6 subunit shared by RNA polymerases I, II, and III.","date":"2003","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/12697831","citation_count":31,"is_preprint":false},{"pmid":"11577101","id":"PMC_11577101","title":"Deletion of the RNA polymerase subunit RPB4 acts as a global, not stress-specific, shut-off switch for RNA polymerase II transcription at high temperatures.","date":"2001","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11577101","citation_count":31,"is_preprint":false},{"pmid":"25416796","id":"PMC_25416796","title":"Rpb4/7 facilitates RNA polymerase II CTD dephosphorylation.","date":"2014","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/25416796","citation_count":29,"is_preprint":false},{"pmid":"25315781","id":"PMC_25315781","title":"The Rpb4/7 module of RNA polymerase II is required for carbon catabolite repressor protein 4-negative on TATA (Ccr4-not) complex to promote elongation.","date":"2014","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/25315781","citation_count":29,"is_preprint":false},{"pmid":"20863887","id":"PMC_20863887","title":"Cycling through transcription with the RNA polymerase F/E (RPB4/7) complex: structure, function and evolution of archaeal RNA polymerase.","date":"2010","source":"Research in microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/20863887","citation_count":26,"is_preprint":false},{"pmid":"18441121","id":"PMC_18441121","title":"Genomewide recruitment analysis of Rpb4, a subunit of polymerase II in Saccharomyces cerevisiae, reveals its involvement in transcription elongation.","date":"2008","source":"Eukaryotic cell","url":"https://pubmed.ncbi.nlm.nih.gov/18441121","citation_count":25,"is_preprint":false},{"pmid":"19492989","id":"PMC_19492989","title":"RNAP subunits F/E (RPB4/7) are stably associated with archaeal RNA polymerase: using fluorescence anisotropy to monitor RNAP assembly in vitro.","date":"2009","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/19492989","citation_count":21,"is_preprint":false},{"pmid":"22917057","id":"PMC_22917057","title":"Rpb4 and Rpb7: multifunctional subunits of RNA polymerase II.","date":"2012","source":"Critical reviews in microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/22917057","citation_count":19,"is_preprint":false},{"pmid":"16972065","id":"PMC_16972065","title":"The fission yeast Rpb4 subunit of RNA polymerase II plays a specialized role in cell separation.","date":"2006","source":"Molecular genetics and genomics : MGG","url":"https://pubmed.ncbi.nlm.nih.gov/16972065","citation_count":18,"is_preprint":false},{"pmid":"11254123","id":"PMC_11254123","title":"Multiple cellular processes affected by the absence of the Rpb4 subunit of RNA polymerase II contribute to the deficiency in the stress response of the yeast rpb4(delta) mutant.","date":"2001","source":"Molecular & general genetics : MGG","url":"https://pubmed.ncbi.nlm.nih.gov/11254123","citation_count":17,"is_preprint":false},{"pmid":"27001033","id":"PMC_27001033","title":"Rpb1 foot mutations demonstrate a major role of Rpb4 in mRNA stability during stress situations in yeast.","date":"2016","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/27001033","citation_count":17,"is_preprint":false},{"pmid":"19720063","id":"PMC_19720063","title":"The Med8 mediator subunit interacts with the Rpb4 subunit of RNA polymerase II and Ace2 transcriptional activator in Schizosaccharomyces pombe.","date":"2009","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/19720063","citation_count":13,"is_preprint":false},{"pmid":"14530281","id":"PMC_14530281","title":"The conserved and non-conserved regions of Rpb4 are involved in multiple phenotypes in Saccharomyces cerevisiae.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/14530281","citation_count":12,"is_preprint":false},{"pmid":"30359412","id":"PMC_30359412","title":"Dissociation of Rpb4 from RNA polymerase II is important for yeast functionality.","date":"2018","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/30359412","citation_count":11,"is_preprint":false},{"pmid":"33440147","id":"PMC_33440147","title":"Numerous Post-translational Modifications of RNA Polymerase II Subunit Rpb4/7 Link Transcription to Post-transcriptional Mechanisms.","date":"2021","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/33440147","citation_count":11,"is_preprint":false},{"pmid":"33094674","id":"PMC_33094674","title":"Rpb4 and Puf3 imprint and post-transcriptionally control the stability of a common set of mRNAs in yeast.","date":"2020","source":"RNA biology","url":"https://pubmed.ncbi.nlm.nih.gov/33094674","citation_count":9,"is_preprint":false},{"pmid":"18056993","id":"PMC_18056993","title":"Unstructured N terminus of the RNA polymerase II subunit Rpb4 contributes to the interaction of Rpb4.Rpb7 subcomplex with the core RNA polymerase II of Saccharomyces cerevisiae.","date":"2007","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/18056993","citation_count":8,"is_preprint":false},{"pmid":"35336925","id":"PMC_35336925","title":"The Influenza Virus RNA-Polymerase and the Host RNA-Polymerase II: RPB4 Is Targeted by a PB2 Domain That Is Involved in Viral Transcription.","date":"2022","source":"Viruses","url":"https://pubmed.ncbi.nlm.nih.gov/35336925","citation_count":7,"is_preprint":false},{"pmid":"35216121","id":"PMC_35216121","title":"The Association of Rpb4 with RNA Polymerase II Depends on CTD Ser5P Phosphatase Rtr1 and Influences mRNA Decay in Saccharomyces cerevisiae.","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/35216121","citation_count":5,"is_preprint":false},{"pmid":"24358479","id":"PMC_24358479","title":"The RNA polymerase II Rpb4/7 subcomplex regulates cellular lifespan through an mRNA decay process.","date":"2013","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/24358479","citation_count":4,"is_preprint":false},{"pmid":"19921261","id":"PMC_19921261","title":"The dissociable RPB4 subunit of RNA Pol II has vital functions in Drosophila.","date":"2009","source":"Molecular genetics and genomics : MGG","url":"https://pubmed.ncbi.nlm.nih.gov/19921261","citation_count":4,"is_preprint":false},{"pmid":"30862564","id":"PMC_30862564","title":"A comparative study of the proteome regulated by the Rpb4 and Rpb7 subunits of RNA polymerase II in fission yeast.","date":"2019","source":"Journal of proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/30862564","citation_count":4,"is_preprint":false},{"pmid":"15913559","id":"PMC_15913559","title":"Mapping the interaction site of Rpb4 and Rpb7 subunits of RNA polymerase II in Saccharomyces cerevisiae.","date":"2005","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/15913559","citation_count":3,"is_preprint":false},{"pmid":"18687406","id":"PMC_18687406","title":"RAM pathway contributes to Rpb4 dependent pseudohyphal differentiation in Saccharomyces cerevisiae.","date":"2008","source":"Fungal genetics and biology : FG & B","url":"https://pubmed.ncbi.nlm.nih.gov/18687406","citation_count":1,"is_preprint":false},{"pmid":"24780862","id":"PMC_24780862","title":"Involvement of S. cerevisiae Rpb4 in subset of pathways related to transcription elongation.","date":"2014","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/24780862","citation_count":1,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.11.20.622938","title":"RNA Polymerase II subunits overexpressions induce genome instability and deregulate transcription","date":"2024-11-20","source":"bioRxiv","url":"https://doi.org/10.1101/2024.11.20.622938","citation_count":0,"is_preprint":true},{"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},{"pmid":null,"id":"bio_10.1101_2025.02.03.636274","title":"Structural Characterization of Native RNA Polymerase II Transcription Complexes and Nucleosomes in  <i>Drosophila melanogaster</i>","date":"2025-02-03","source":"bioRxiv","url":"https://doi.org/10.1101/2025.02.03.636274","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":24477,"output_tokens":7049,"usd":0.089583,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":16381,"output_tokens":5349,"usd":0.107815,"stage2_stop_reason":"end_turn"},"total_usd":0.197398,"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\": 2004,\n      \"finding\": \"X-ray crystal structure of Rpb4/7 subcomplex determined at 2.3 Å resolution; combined with the 10-subunit Pol II core to refine a 3.8 Å atomic model of complete 12-subunit Pol II. Structural comparison revealed that core-Rpb4/7 interaction induces formation of an α-helix in the linker region of Rpb1 and folding of the Rpb7 tip loop. Details of the interface explain facilitated Rpb4/7 dissociation in a temperature-sensitive Pol II mutant.\",\n      \"method\": \"X-ray crystallography (2.3 Å for subcomplex, 3.8 Å for complete Pol II); structural comparison with core and free Rpb4/7\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structures with functional interpretation, replicated in multiple structural studies\",\n      \"pmids\": [\"15591044\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1989,\n      \"finding\": \"Deletion of RPB4 in S. cerevisiae produces heat- and cold-sensitive cells and markedly reduces RNA polymerase II activity in crude extracts in vitro, establishing that Rpb4 is required for normal Pol II activity especially at temperature extremes, though not essential for enzyme assembly.\",\n      \"method\": \"Gene deletion, in vitro RNA polymerase activity assay in crude extracts\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function with defined enzymatic and growth phenotype, foundational study replicated by multiple subsequent labs\",\n      \"pmids\": [\"2674672\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Crystal structure of the archaeal RPB4/7 homolog complex (Methanococcus jannaschii subunits E and F) determined; subunit E has an elongated two-domain structure with two potential RNA-binding motifs; subunit F wraps around one side of subunit E at the domain interface. A structural model was proposed in which the RNA-binding face of RPB7 is positioned to interact with the nascent RNA transcript.\",\n      \"method\": \"X-ray crystallography of archaeal E/F complex\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional model, consistent with subsequent biochemical and structural studies\",\n      \"pmids\": [\"11741548\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Purified yeast Rpb4/7 heterodimer binds single-stranded DNA and RNA via an OB-fold motif in Rpb7. A deletion in the putative OB-fold nucleic acid-binding surface of Rpb7 abolished binding without affecting Rpb4/7 complex stability or its association with polymerase, yet destroyed transcription activity. Rpb4/7 is required for a post-recruitment step in transcription initiation, not for stable promoter binding.\",\n      \"method\": \"Template competition assay, purified Rpb4/7 single-strand nucleic acid-binding assay, Rpb7 deletion mutagenesis, in vitro transcription reconstitution\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with mutagenesis and multiple functional assays in one rigorous study\",\n      \"pmids\": [\"11087726\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Crystal structure of human Rpb4/Rpb7 heterodimer determined at 2.7 Å. Site-directed mutagenesis of conserved solvent-exposed residues in the Rpb7 OB-fold (including the B4-B5 loop) identified an elongated surface region involved in RNA binding, confirmed by EMSA. The homologous archaeal E subunit uses the same surface for RNA binding.\",\n      \"method\": \"X-ray crystallography (2.7 Å), site-directed mutagenesis, electrophoretic mobility shift assay (EMSA)\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with mutagenesis and biochemical RNA-binding assays in one study\",\n      \"pmids\": [\"16282592\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"3D EM structure of wild-type yeast Pol II located Rpb4 and Rpb7 at the floor of the DNA-binding cleft. Surface plasmon resonance showed that Rpb4/7 stabilize a minimal pre-initiation complex (promoter DNA, TBP, TFIIB, Pol II), suggesting a role in coupling DNA entry into the cleft to cleft closure during promoter-specific transcription.\",\n      \"method\": \"3D electron microscopy, difference mapping, surface plasmon resonance\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — structural localization plus biophysical interaction assay (SPR), single lab but two orthogonal methods\",\n      \"pmids\": [\"9545247\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Rpb4 plays a dual role in transcription-coupled DNA repair (TCR) in S. cerevisiae: it suppresses the Rpb9-dependent TCR subpathway and facilitates the Rad26-dependent TCR subpathway, demonstrating a regulatory function of Rpb4 in selecting between TCR subpathways.\",\n      \"method\": \"Genetic epistasis analysis using deletion mutants (rpb4Δ, rpb9Δ, rad26Δ combinations); repair assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with multiple double/triple mutant combinations providing clear pathway placement\",\n      \"pmids\": [\"12411509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"In S. pombe, Fcp1 CTD-phosphatase directly interacts with the Rpb4 subunit of Pol II, identified by chemical cross-linking, GST pulldown, and affinity chromatography. Repression of rpb4 expression reduced Fcp1 in the Pol II complex and increased CTD phosphorylation, demonstrating that Rpb4 is required for Fcp1/TFIIF/Pol II complex formation in vivo.\",\n      \"method\": \"Immunoaffinity purification, chemical cross-linking, GST pulldown, affinity chromatography, rpb4 shut-off strain\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal biochemical methods (cross-linking, pulldown, affinity chromatography) plus in vivo genetic manipulation\",\n      \"pmids\": [\"11839823\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Rpb4 is required for Pol II enzymatic activity at temperature extremes (10°C and 35°C) but not at moderate temperature (23°C). Addition of recombinant Rpb4 produced in E. coli rescues Pol II activity in extracts from postlogarithmic cells at non-optimal temperatures. Sucrose gradient and immunoprecipitation showed Rpb4 is present in excess over the Pol II complex, and only Pol II from postlogarithmic cells can be rescued, suggesting Pol II must be modified to recruit Rpb4.\",\n      \"method\": \"In vitro promoter-independent transcription assay in cell extracts, recombinant Rpb4 complementation, sucrose gradient sedimentation, immunoprecipitation\",\n      \"journal\": \"Journal of bacteriology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro enzymatic assay with recombinant protein complementation and multiple supporting methods\",\n      \"pmids\": [\"9829926\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Rpb7 can interact with Pol II and support transcription independently of Rpb4 when overexpressed, but fewer Rpb7 molecules associate with Pol II lacking Rpb4 than with wild-type Pol II. Reciprocal coimmunoprecipitation confirmed stable interaction of overproduced Rpb7 with Pol IIΔ4. A major role of Rpb4 is to augment Rpb7 binding to Pol II.\",\n      \"method\": \"RPB7 overexpression suppressor screen, reciprocal coimmunoprecipitation\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus genetic suppression analysis, single lab\",\n      \"pmids\": [\"10082533\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"A conditional mutation in the shared Rpb6 subunit (Q100R) causes selective loss of Rpb4 and Rpb7 from purified RNA Pol II. Interaction experiments demonstrated a direct association between Rpb6 and Rpb4, identifying Rpb6 as one contact point between the Rpb4/7 subcomplex and Pol II.\",\n      \"method\": \"Conditional rpb6 mutagenesis, Pol II purification, protein interaction assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct interaction demonstrated biochemically with genetic confirmation, single lab\",\n      \"pmids\": [\"12697831\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Chromatin immunoprecipitation of Rpb4 showed it crosslinks throughout transcribed regions genome-wide. Loss of Rpb4 reduces Pol II levels near 3' ends of mRNA genes, decreases cotranscriptional recruitment of 3'-end processing factors, and alters polyadenylation site usage at the RNA14 gene, establishing that Rpb4 contributes to cotranscriptional 3'-end processing.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), rpb4Δ strain analysis, polyadenylation site mapping\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP with loss-of-function and defined molecular phenotype, single lab\",\n      \"pmids\": [\"18195044\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Genome-wide ChIP coupled to tiling microarray analysis showed that Rpb7 occupancy profiles across the genome are essentially identical to core subunit Rpb3, demonstrating that complete Pol II (including Rpb4/7) associates with DNA in vivo throughout the transcription cycle.\",\n      \"method\": \"Chromatin immunoprecipitation coupled to high-resolution tiling microarray (ChIP-chip)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide ChIP-chip with quantitative comparison, single lab\",\n      \"pmids\": [\"18667430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Quantitative proteomics showed that Rpb4/7 dissociate from RNAPII upon interaction with specific transcriptional elongation-associated proteins recruited to the hyperphosphorylated CTD. RNAPII isolated through Rpb7 is depleted in Ser2 CTD phosphorylation, indicating Rpb4/7 are dispensable during specific elongation stages.\",\n      \"method\": \"Quantitative mass spectrometry proteomics, co-immunoprecipitation with phospho-CTD isoforms\",\n      \"journal\": \"Molecular & cellular proteomics : MCP\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — quantitative proteomics with multiple conditions, single lab\",\n      \"pmids\": [\"23418395\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Metabolic RNA labeling and dynamic transcriptome analysis showed Rpb4 deletion causes a drastic defect in mRNA synthesis compensated by down-regulation of mRNA degradation (mRNA buffering). Covalent fusion of Rpb4 to Pol II core subunit Rpb2 largely restores mRNA synthesis and degradation defects, demonstrating that Rpb4 functions primarily in nuclear mRNA synthesis by Pol II.\",\n      \"method\": \"Metabolic RNA labeling, comparative dynamic transcriptome analysis, Rpb2-Rpb4 fusion protein complementation, rpb4Δ strain\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (metabolic labeling, transcriptome analysis, fusion protein rescue) establishing primary nuclear function\",\n      \"pmids\": [\"24802753\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Deletion of RPB4 or disruption of Rpb4/7 integrity increased phosphorylation of CTD residues Ser2, Ser5, Ser7, and Thr4 of Rpb1. Genetic interactions were found with CTD phosphatases SSU72 and FCP1. Rpb4 is important for association and recruitment of Ssu72 (Ser5P phosphatase) and Fcp1 (Ser2P/Thr4P phosphatase) to the CTD, placing Rpb4/7 as a facilitator of CTD dephosphorylation.\",\n      \"method\": \"rpb4Δ strain phospho-CTD analysis, genetic interaction screens, phosphatase recruitment assays (ChIP)\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple genetic and biochemical approaches, single lab\",\n      \"pmids\": [\"25416796\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The Ccr4-Not complex requires the Rpb4/7 module of Pol II to associate with elongation complexes and stimulate Pol II elongation; loss of Rpb4/7 impairs Ccr4-Not-dependent reactivation of arrested elongation complexes.\",\n      \"method\": \"In vitro elongation assays with purified Ccr4-Not complex, rpb4/7 deletion strains\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro elongation assay plus genetic analysis, single lab\",\n      \"pmids\": [\"25315781\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"3C analysis showed that gene loop formation is abolished in rpb4Δ cells. RPB4 overexpression rescued gene looping and transcription termination defects of sua7-1 (TFIIB mutant) and ssu72-2, while SSU72 overexpression restored gene loops in rpb4Δ cells. Rpb4 facilitates the TFIIB-Ssu72 interaction required for gene loop formation, promoting Pol II transfer from terminator to promoter for transcription reinitiation.\",\n      \"method\": \"Chromosome conformation capture (3C) assay, genetic suppression analysis, rpb4Δ strain\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — 3C with multiple genetic suppression experiments, single lab\",\n      \"pmids\": [\"31304538\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Using wholly recombinant archaeal RNAP, the F/E complex (RPB4/7 homolog) greatly stimulates RNAP processivity, enhances full-length product formation, reduces pausing, and increases termination at weak termination signals during elongation. F/E mutants defective in RNA binding show reduced stimulatory activity, implicating F/E–RNA interactions as pivotal for elongation and termination.\",\n      \"method\": \"In vitro transcription assay with recombinant archaeal RNAP; F/E mutant variants on synthetic nucleic acid scaffolds\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — wholly recombinant in vitro reconstitution with RNA-binding mutants, single lab but rigorous biochemical analysis\",\n      \"pmids\": [\"19906731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Rpb4 is required for activated transcription from a subset of promoters in S. cerevisiae; constitutive transcription is largely unaffected. The C-terminal 24 amino acids of Rpb4 are critical for this activation function. Transcriptional activation by artificial TBP recruitment is also defective without Rpb4.\",\n      \"method\": \"rpb4Δ strain, promoter-reporter assays, domain deletion analysis, TBP recruitment assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined promoter-specific phenotype and domain localization, single lab\",\n      \"pmids\": [\"11382749\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Pulldown and complementation assays identified two crucial contact points for Rpb4/7 subcomplex association with the Pol II core: the N-terminal RNP-like domain of Rpb7 and the partially ordered N-terminal region of Rpb4 (interacting with Rpb2). Mutations in Rpb7's N-terminal domain increase dependence on Rpb4 for polymerase interaction.\",\n      \"method\": \"RNA polymerase pulldown assay, complementation analysis, mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pulldown and complementation with mutagenesis, single lab\",\n      \"pmids\": [\"18056993\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Rpb4/7 undergoes more than 100 combinations of post-translational modifications (PTMs); the PTM repertoire changes as the mRNA/Rpb4/7 complex progresses through stages of the mRNA life cycle (transcription, export, translation, decay). Specific PTM mutants affect Rpb4 interactions with key regulators (Pol II, eIF3, Pat1) and disrupt mRNA synthesis/decay buffering.\",\n      \"method\": \"Mass spectrometry-based PTM mapping, PTM mutant functional analysis, interaction assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS-based PTM identification combined with functional mutant analysis, single lab\",\n      \"pmids\": [\"33440147\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Rpb4-Rpb2 fusion protein supports normal transcription but adversely affects mRNA decay, cell proliferation, and stress response, demonstrating that dissociation of Rpb4 from Pol II is required for its cytoplasmic roles in mRNA decay regulation. A portion of the fusion protein is proteolytically cleaved to release free functional Rpb4 that binds mRNAs and polysomes.\",\n      \"method\": \"Rpb2-Rpb4 fusion protein expression, mRNA decay assays, polysome association, stress response assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — fusion protein dissociation assay with multiple functional readouts, single lab\",\n      \"pmids\": [\"30359412\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"In S. pombe, Med8 mediator subunit interacts with Rpb4, and Ace2 transcriptional activator interacts with Med8; the C-terminal region of Med8 is required for its interaction with Rpb4. This defines a protein interaction chain (Ace2–Med8–Rpb4) that relays transcriptional regulatory signals to Pol II during cell separation.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, domain deletion analysis\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — two-hybrid and Co-IP with domain delineation, single lab\",\n      \"pmids\": [\"19720063\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Genome-wide ChIP-chip analysis showed Rpb4 is recruited to coding regions of most transcriptionally active genes with extent increasing with gene length. Pol II lacking Rpb4 is defective in transcribing long, GC-rich transcription units, and rpb4Δ cells are sensitive to 6-azauracil, establishing a role for Rpb4 in transcription elongation that is independent of Rpb7.\",\n      \"method\": \"ChIP-chip (genome-wide chromatin immunoprecipitation with microarray), 6-azauracil sensitivity assay, rpb4Δ strain\",\n      \"journal\": \"Eukaryotic cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide ChIP with functional phenotype, single lab\",\n      \"pmids\": [\"18441121\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Binary complementation assays revealed an interaction between the N-terminal third domain of influenza PB2 and human RPB4. This interaction was confirmed by co-immunoprecipitation and was found with influenza A, B, and C FluPols. The N-half domain of RPB4 is critical for this interaction. PB2 mutants at conserved positions showed strong transcriptional activity defects, suggesting FluPol uses RPB4 to position itself near the 5'-end of nascent host mRNA during cap-snatching.\",\n      \"method\": \"Binary complementation assay, co-immunoprecipitation, PB2 mutagenesis\",\n      \"journal\": \"Viruses\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — reciprocal interaction confirmed by two methods with functional mutagenesis, single lab\",\n      \"pmids\": [\"35336925\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"RTR1 deletion increases the amount of chromatin-associated Pol II lacking Rpb4, decreases Rpb4-mRNA imprinting, and consequently increases mRNA stability. Rtr1 (CTD Ser5P phosphatase) mediates proper association of Rpb4/7 with Pol II during assembly, linking CTD phosphorylation state to Rpb4/7 incorporation and downstream mRNA decay regulation.\",\n      \"method\": \"RTR1 deletion strain, Pol II assembly analysis, ChIP, mRNA stability assays\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function with multiple biochemical readouts, single lab\",\n      \"pmids\": [\"35216121\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"RIP-Seq showed Rpb4 associates genome-wide with more than 1400 mRNA targets. Rpb4 and Puf3 RNA-binding protein physically interact, genetically interact, and co-regulate mRNA stability of a shared set of transcripts. Rpb4-mRNA association depends on Puf3 and vice versa. Puf3 associates with chromatin in an Rpb4-dependent manner, establishing a co-transcriptional imprinting mechanism.\",\n      \"method\": \"RIP-Seq, co-immunoprecipitation, genetic interaction analysis, ChIP\",\n      \"journal\": \"RNA biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (RIP-Seq, Co-IP, ChIP, genetics) in a single lab study\",\n      \"pmids\": [\"33094674\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"RPB1 foot mutations that impair Rpb4/7 assembly into Pol II activate an environmental stress response (ESR) under optimal growth conditions primarily through post-transcriptional regulation dependent on Rpb4-mRNA imprinting, revealing that Rpb4 globally modulates mRNA stability and coordinates transcription with mRNA decay.\",\n      \"method\": \"RPB1 foot mutant strains, global transcriptional analysis, mRNA stability assays, Rpb4/7 assembly analysis\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Pol II assembly mutants with global transcriptome and mRNA decay analysis, single lab\",\n      \"pmids\": [\"27001033\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"POLR2D (Rpb4) is a dissociable subunit of RNA polymerase II that forms a stable heterodimer with Rpb7 (Rpb4/7), docking onto the Pol II core through contacts with Rpb2 and Rpb6; structurally, Rpb4/7 positions an RNA-binding OB-fold near the RNA exit groove to stabilize the nascent transcript, stimulate transcription initiation (post-recruitment step), elongation processivity, and termination; Rpb4 facilitates CTD dephosphorylation by recruiting Ssu72 and Fcp1 phosphatases, promotes cotranscriptional recruitment of 3'-end processing factors, enables gene loop formation via stabilizing the TFIIB-Ssu72 interaction, and is required for transcription-coupled DNA repair through dual regulation of the Rpb9 and Rad26 TCR subpathways; beyond transcription, Rpb4 is co-transcriptionally loaded onto mRNAs ('imprinting'), accompanies them to the cytoplasm where—regulated by an extensive set of post-translational modifications—it coordinates mRNA export, translation, and decay by interacting with factors such as eIF3 and Pat1, thereby coupling nuclear mRNA synthesis to cytoplasmic mRNA stability.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"POLR2D (Rpb4) is a dissociable subunit of RNA polymerase II that, together with Rpb7, forms a heterodimeric subcomplex docking onto the polymerase core and serving as a hub that couples nuclear transcription to cytoplasmic mRNA fate [#0, #14]. The Rpb4/7 subcomplex contacts the core through the N-terminal RNP-like domain of Rpb7 and the N-terminal region of Rpb4 (which engages Rpb2), with Rpb6 providing an additional docking point; Rpb4 augments Rpb7 association with the polymerase, and a major contribution of the module is to position an OB-fold RNA-binding surface near the nascent transcript [#3, #4, #20, #10, #9]. Functionally, Rpb4/7 stabilizes the pre-initiation complex and is required for a post-recruitment step in initiation, supports elongation through long GC-rich units, and stimulates processivity, pausing suppression, and termination via direct RNA contacts [#5, #3, #24, #18]. Rpb4 facilitates CTD dephosphorylation by promoting recruitment of the Ssu72 and Fcp1 phosphatases, enables gene loop formation by stabilizing the TFIIB–Ssu72 interaction to recycle Pol II for reinitiation, and supports cotranscriptional 3'-end processing and selection between transcription-coupled DNA repair subpathways [#15, #7, #17, #11, #6]. Metabolic labeling and Rpb4–Rpb2 fusion rescue establish that Rpb4 acts primarily in nuclear mRNA synthesis, but the protein is also co-transcriptionally loaded onto mRNAs ('imprinting') and, upon dissociation, accompanies them to the cytoplasm where—regulated by an extensive PTM repertoire and acting through partners such as Puf3 and Pat1—it globally coordinates mRNA stability and decay to buffer mRNA levels against changes in synthesis [#14, #22, #27, #21, #28]. Deletion of RPB4 in yeast produces heat- and cold-sensitive growth and reduced Pol II activity at temperature extremes [#1]; no human Mendelian disease connection is described in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 1989,\n      \"claim\": \"Established that Rpb4 is a non-essential but functionally important Pol II subunit by showing its loss impairs polymerase activity and growth at temperature extremes.\",\n      \"evidence\": \"RPB4 gene deletion and in vitro Pol II activity assays in yeast crude extracts\",\n      \"pmids\": [\"2674672\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the molecular step Rpb4 affects\", \"Mechanism of temperature sensitivity unresolved\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Localized Rpb4/7 to the Pol II cleft and showed it stabilizes the pre-initiation complex, linking the subunit to initiation rather than catalysis alone.\",\n      \"evidence\": \"3D EM difference mapping and surface plasmon resonance on yeast Pol II/PIC; in vitro complementation with recombinant Rpb4\",\n      \"pmids\": [\"9545247\", \"9829926\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the RNA-contacting surface\", \"Nature of the postlogarithmic Pol II modification enabling Rpb4 recruitment unknown\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Defined the mechanistic basis of Rpb4/7 action by showing the Rpb7 OB-fold binds single-stranded nucleic acid and is required for a post-recruitment initiation step, separating nucleic-acid binding from complex assembly.\",\n      \"evidence\": \"Purified Rpb4/7 nucleic-acid binding, OB-fold deletion mutagenesis, and in vitro transcription reconstitution\",\n      \"pmids\": [\"11087726\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve the exact post-recruitment step in vivo\", \"Genome-wide relevance not yet established\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Resolved how the Rpb4/7 dimer is organized and how its RNA-binding face is oriented, providing a structural model for nascent transcript engagement, and showed promoter-selective and activation roles for Rpb4.\",\n      \"evidence\": \"X-ray structure of the archaeal E/F homolog; rpb4Δ promoter-reporter and domain-deletion assays in yeast\",\n      \"pmids\": [\"11741548\", \"11382749\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Archaeal model required validation in eukaryotic Pol II\", \"Which activators depend on Rpb4 C-terminus not enumerated\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Connected Rpb4 to CTD phosphatase recruitment and to transcription-coupled DNA repair, broadening its role to post-elongation regulation.\",\n      \"evidence\": \"Fcp1–Rpb4 cross-linking/pulldown with rpb4 shut-off in S. pombe; genetic epistasis of rpb4Δ/rpb9Δ/rad26Δ TCR mutants\",\n      \"pmids\": [\"11839823\", \"12411509\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct phosphatase recruitment mechanism not structurally defined\", \"How Rpb4 discriminates between TCR subpathways unresolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Provided the human Rpb4/Rpb7 structure and mapped the conserved RNA-binding surface, confirming evolutionary conservation of the OB-fold mechanism.\",\n      \"evidence\": \"X-ray crystallography of human Rpb4/7 at 2.7 Å with site-directed mutagenesis and EMSA\",\n      \"pmids\": [\"16282592\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Human in vivo functions not tested here\", \"RNA specificity determinants not defined\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defined the atomic interface between Rpb4/7 and the Pol II core, explaining how core contact induces conformational changes and how dissociation occurs.\",\n      \"evidence\": \"X-ray structures of Rpb4/7 (2.3 Å) and the complete 12-subunit Pol II (3.8 Å) with comparative structural analysis\",\n      \"pmids\": [\"15591044\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Dynamics of regulated dissociation in vivo not captured\", \"PTM influence on the interface not addressed\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identified Rpb6 and the Rpb7 N-terminal RNP domain plus the Rpb4 N-terminus as the physical anchors of the subcomplex on the core, and showed Rpb4 augments Rpb7 incorporation.\",\n      \"evidence\": \"Conditional rpb6 mutagenesis and direct interaction assays; RPB7 overexpression suppression with reciprocal Co-IP; pulldown/complementation mapping\",\n      \"pmids\": [\"12697831\", \"10082533\", \"18056993\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative contribution of each contact to assembly kinetics not quantified\", \"Single-lab interaction data\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Showed genome-wide that complete Pol II including Rpb4/7 traverses transcribed regions and that Rpb4 contributes to elongation of long genes and to cotranscriptional 3'-end processing.\",\n      \"evidence\": \"ChIP and ChIP-chip of Rpb4/Rpb7 vs Rpb3 in yeast; rpb4Δ poly(A) site mapping and 6-azauracil sensitivity\",\n      \"pmids\": [\"18195044\", \"18667430\", \"18441121\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism coupling Rpb4 to 3'-end factor recruitment not biochemically reconstituted\", \"Single-lab genome-wide datasets\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Demonstrated directly that the Rpb4/7 homolog stimulates elongation processivity and termination through RNA binding, and placed Rpb4 in a mediator-relayed regulatory chain.\",\n      \"evidence\": \"Recombinant archaeal RNAP in vitro transcription with F/E RNA-binding mutants; Ace2–Med8–Rpb4 two-hybrid and Co-IP in S. pombe\",\n      \"pmids\": [\"19906731\", \"19720063\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Archaeal elongation findings need eukaryotic confirmation\", \"Mediator chain shown only for cell-separation genes\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed Rpb4/7 dissociates from Pol II at specific elongation stages tied to CTD phosphorylation state, refining when the module is functionally engaged.\",\n      \"evidence\": \"Quantitative mass spectrometry and Co-IP across phospho-CTD isoforms\",\n      \"pmids\": [\"23418395\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of dissociation at elongation not directly tested here\", \"Single-lab proteomics\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Established that Rpb4's primary role is in nuclear mRNA synthesis and that it facilitates CTD dephosphorylation and Ccr4-Not-dependent elongation, while coupling synthesis to mRNA decay via buffering.\",\n      \"evidence\": \"Metabolic RNA labeling with Rpb2-Rpb4 fusion rescue; rpb4Δ phospho-CTD analysis with SSU72/FCP1 genetics; in vitro Ccr4-Not elongation assays\",\n      \"pmids\": [\"24802753\", \"25416796\", \"25315781\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for phosphatase recruitment unresolved\", \"How nuclear synthesis defect signals to cytoplasmic decay not fully mapped\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Linked Rpb4/7 assembly into Pol II to global post-transcriptional control, showing imprinting-dependent modulation of mRNA stability and stress responses.\",\n      \"evidence\": \"RPB1 foot mutants impairing Rpb4/7 assembly with global transcriptome and mRNA stability analysis\",\n      \"pmids\": [\"27001033\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct imprinting mechanism on individual transcripts not resolved here\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrated that physical dissociation of Rpb4 from Pol II is required for its cytoplasmic mRNA-decay functions, distinguishing nuclear from cytoplasmic roles.\",\n      \"evidence\": \"Rpb2-Rpb4 fusion expression with mRNA decay, polysome association, and stress-response assays in yeast\",\n      \"pmids\": [\"30359412\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Proteolytic release mechanism not fully characterized\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified the co-transcriptional imprinting machinery, showing Rpb4 and Puf3 mutually depend on each other to load onto mRNAs and co-regulate transcript stability.\",\n      \"evidence\": \"RIP-Seq, Co-IP, ChIP, and genetic interaction analysis of Rpb4 and Puf3 in yeast\",\n      \"pmids\": [\"33094674\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Generality beyond Puf3-bound transcripts unknown\", \"Single-lab dataset\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Revealed that a stage-specific PTM code on Rpb4/7 regulates its interactions with Pol II, eIF3, and Pat1 to control its progression through the mRNA life cycle.\",\n      \"evidence\": \"Mass spectrometry PTM mapping with PTM-mutant functional and interaction analysis\",\n      \"pmids\": [\"33440147\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Enzymes writing/erasing individual PTMs not identified\", \"Causal ordering of PTM transitions not established\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined an upstream determinant (Rtr1 CTD phosphatase) of Rpb4/7 incorporation and identified RPB4 as a host target hijacked by influenza polymerase, extending its mechanistic reach.\",\n      \"evidence\": \"RTR1 deletion with Pol II assembly/ChIP and mRNA stability assays; binary complementation and Co-IP of influenza PB2 with human RPB4 plus PB2 mutagenesis\",\n      \"pmids\": [\"35216121\", \"35336925\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural details of the FluPol–RPB4 interaction not resolved\", \"How Rtr1 mechanistically couples CTD state to assembly not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the Rpb4/7 PTM code and assembly state are integrated in metazoan cells, and whether POLR2D dysfunction underlies human disease, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No human in vivo functional study in the corpus\", \"No Mendelian disease link characterized\", \"Most mechanistic detail derives from yeast and archaeal systems\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [3, 4, 18, 27]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 5, 20]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [3, 15, 18]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [11, 12, 24]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [22, 27]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [1, 3, 5, 14, 24]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [14, 22, 27, 28]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"complexes\": [\n      \"RNA polymerase II\",\n      \"Rpb4/7 subcomplex\"\n    ],\n    \"partners\": [\n      \"POLR2G\",\n      \"POLR2B\",\n      \"POLR2F\",\n      \"FCP1\",\n      \"SSU72\",\n      \"PUF3\",\n      \"PAT1\",\n      \"EIF3\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}