{"gene":"RPAP2","run_date":"2026-06-10T06:43:37","timeline":{"discoveries":[{"year":2008,"finding":"Rtr1 (yeast RPAP2 ortholog) physically associates with active RNAPII transcriptional complex, shuttles between cytoplasm and nucleus, and is required for inducible transcription (GAL1 promoter). High-copy suppressors of rtr1Δ temperature-sensitive phenotype included core RNAPII subunits RPB5, RPB7, and RPB9, placing Rtr1 functionally within the RNAPII complex.","method":"Co-immunoprecipitation, genetic suppressor screen, growth assays, fluorescence microscopy","journal":"Eukaryotic cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal genetic and physical interaction data in single lab with multiple methods","pmids":["18408053"],"is_preprint":false},{"year":2009,"finding":"Rtr1 (yeast RPAP2 ortholog) functions as a CTD phosphatase that dephosphorylates Ser5-phosphorylated RNAPII, localizes within coding regions between the peaks of Ser5-P and Ser2-P, and is essential for the transition from Ser5 to Ser2 CTD phosphorylation during transcription elongation. Deletion of Rtr1 causes accumulation of Ser5-P RNAPII, decreased transcription, and termination defects.","method":"ChIP, whole-cell extract phosphorylation analysis, deletion mutant phenotypic analysis, functional characterization of phosphatase activity","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (ChIP, biochemical phosphatase assay, genetic deletion), replicated across subsequent studies","pmids":["19394294"],"is_preprint":false},{"year":2011,"finding":"Human RPAP2 specifically recognizes phospho-Ser7 on the Pol II CTD and is recruited to snRNA genes via this mark. RPAP2 also interacts with Integrator complex subunits and functions as a CTD Ser5 phosphatase. siRNA knockdown of RPAP2 and Ser7-to-Ala mutation cause similar defects in snRNA gene expression, indicating Ser7-P recruits RPAP2, which in turn recruits Integrator and dephosphorylates Ser5.","method":"siRNA knockdown, ChIP, co-immunoprecipitation, in vitro phosphatase assay, mutational analysis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro phosphatase assay combined with genetic (siRNA/mutation) and ChIP evidence, multiple orthogonal methods in single rigorous study","pmids":["22137580"],"is_preprint":false},{"year":2012,"finding":"Crystal structure of Kluyveromyces lactis Rtr1 reveals a new type of zinc finger protein with no identifiable active site and no close structural homologues. Extensive in vitro experiments failed to detect CTD phosphatase activity, suggesting Rtr1 may have a non-catalytic role in CTD dephosphorylation.","method":"X-ray crystallography, in vitro phosphatase assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure plus extensive negative enzymatic assays; single lab but rigorous structural and biochemical methods; NEGATIVE finding regarding phosphatase activity","pmids":["22781759"],"is_preprint":false},{"year":2014,"finding":"Rtr1 is a phosphatase of new structure that is auto-inhibited by its own C-terminus. In vitro, Rtr1 dephosphorylates both Ser5 and Tyr1 on the CTD (dual specificity). A single amino acid mutation reducing activity causes the same in vivo phenotype as full gene deletion, establishing that enzymatic activity is functionally important.","method":"In vitro phosphatase assay, site-directed mutagenesis, yeast complementation assay","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with mutagenesis validated in vivo; directly contradicts the structural study (PMID:22781759) showing lack of activity","pmids":["24951832"],"is_preprint":false},{"year":2014,"finding":"Rtr1 preferentially interacts with hyperphosphorylated RNAPII as its primary binding partner in yeast. Interaction between Rtr1 and RNAPII is decreased in ctk1Δ strains lacking CTD Ser2 kinase, suggesting Ser2 CTD phosphorylation is required for Rtr1 recruitment during transcription elongation.","method":"Quantitative proteomics (mass spectrometry-based interactome), affinity purification","journal":"Molecular bioSystems","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — quantitative MS-based interactome in WT and deletion strains, single lab","pmids":["24671508"],"is_preprint":false},{"year":2014,"finding":"The C-terminal region of human RPAP2 interacts directly with Pol II subunit Rpb6. RPAP2 occupies coding and 3' regions of protein-coding genes (MYC, GAPDH), and siRNA-mediated knockdown of RPAP2 causes defects in pre-mRNA 3'-end formation.","method":"Direct interaction assay (pulldown), ChIP, siRNA knockdown, RNA processing analysis","journal":"Drug discoveries & therapeutics","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — direct interaction mapped to C-terminal region, combined with ChIP and functional knockdown, single lab","pmids":["25639305"],"is_preprint":false},{"year":2016,"finding":"Crystal structure of S. cerevisiae Rtr1 at 2.6 Å resolution reveals a phosphoryl transfer domain with a putative active site containing a trapped sulfate ion in a deep groove between the zinc finger domain and a pair of helices. Mutagenesis of active-site residues disrupts in vitro catalytic activity and fails to rescue growth of rtr1Δ yeast. RPAP2 and a mutant of the conserved catalytic site show similar behavior, indicating a conserved reaction mechanism distinct from other phosphatase families.","method":"X-ray crystallography (2.6 Å), site-directed mutagenesis, in vitro phosphatase assay, yeast complementation","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus mutagenesis plus in vitro activity plus in vivo rescue, multiple orthogonal methods","pmids":["26933063"],"is_preprint":false},{"year":2016,"finding":"Rtr1 is a global regulator of CTD Ser5 phosphorylation; RTR1 deletion causes genome-wide increases in Ser5-P and global increases in cotranscriptional H3K36 trimethylation, consistent with Rtr1 controlling the number of binding sites for histone methyltransferase Set2.","method":"ChIP-chip (chromatin immunoprecipitation with microarrays), genome-wide analysis of RNAPII phosphorylation","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genome-wide ChIP data in deletion strain, single lab with two orthogonal readouts (CTD phosphorylation and histone methylation)","pmids":["27247267"],"is_preprint":false},{"year":2020,"finding":"Loss of RTR1 alters interactions within the termination machinery: Rtr1 deletion decreases RNAPII-Pcf11 (CF1A subunit) interactions and increases RNAPII-Nrd1 interactions. RTR1 deletion globally increases termination at noncoding genes via the NNS (Nrd1-Nab3-Sen1) pathway and causes premature termination at protein-coding genes. Rtr1 normally restricts NNS-dependent termination to prevent premature termination.","method":"DisCo network analysis (quantitative proteomics), genome-wide ChIP-seq (RNAPII and Nrd1 occupancy), RNA-seq, genetic epistasis with rrp6Δ","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal genome-wide methods (proteomics, ChIP-seq, RNA-seq) plus genetic epistasis, single lab","pmids":["32187185"],"is_preprint":false},{"year":2021,"finding":"Cryo-EM structure of mammalian Pol II in complex with human RPAP2 at 2.8 Å resolution shows RPAP2 binds between the jaw domains of RPB1 and RPB5 subunits. RPAP2 is incompatible with downstream DNA binding during transcription and is displaced upon pre-initiation complex formation.","method":"Cryo-electron microscopy (2.8 Å resolution)","journal":"Communications biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution cryo-EM structure of the mammalian complex with clear structural basis for displacement mechanism","pmids":["34021257"],"is_preprint":false},{"year":2022,"finding":"RPAP2 binds both hypo- and hyper-phosphorylated Pol II. Cryo-EM structure of the RPAP2-Pol II complex shows mutually exclusive assembly with the pre-initiation complex (PIC) due to three steric clashes. RPAP2 prevents and disrupts Pol II-TFIIF interaction and impairs in vitro transcription initiation. Loss of RPAP2 causes global accumulation of TFIIF and Pol II at promoters, demonstrating RPAP2 inhibits PIC assembly independent of phosphatase activity.","method":"Cryo-EM structure, in vitro transcription assay, RPAP2 depletion with ChIP-seq, biochemical binding assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structure combined with in vitro transcription assay and genome-wide ChIP-seq loss-of-function, multiple orthogonal methods","pmids":["35476980"],"is_preprint":false},{"year":2022,"finding":"Rtr1 is required for assembly of the two largest RNAPII subunits (Rpb1-Rpb2) by cooperating with assembly factors Gpn3 and Npa3. RTR1 overexpression is a multicopy suppressor of gpn3, gpn2, and rba50 assembly mutants. Deletion of RTR1 leads to cytoplasmic clumping of RNAPII subunits. Notably, phosphatase-dead Rtr1 mutant does not trigger cytoplasmic clumping, indicating this assembly function is independent of phosphatase activity.","method":"Genetic suppressor analysis, co-immunoprecipitation, fluorescence microscopy, catalytically inactive mutant analysis","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis plus Co-IP plus localization imaging, single lab with multiple orthogonal methods","pmids":["36190433"],"is_preprint":false},{"year":2022,"finding":"Rtr1 mediates the association of the Rpb4/7 heterodimer with the rest of RNAPII. RTR1 deletion alters RNAPII assembly, increasing chromatin-associated RNAPII lacking Rpb4, which decreases Rpb4-mRNA imprinting and consequently increases mRNA stability. This establishes a link between Rtr1-mediated RNAPII assembly and mRNA decay regulation.","method":"Co-immunoprecipitation, ChIP, mRNA stability assays, genetic deletion analysis","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — multiple methods (Co-IP, ChIP, RNA stability) in single lab linking assembly defect to mRNA decay","pmids":["35216121"],"is_preprint":false},{"year":2022,"finding":"RPAP2 functions as a PERK-dependent IRE1α phosphatase in the unfolded protein response. TGFβ1-mediated dephosphorylation of IRE1α is mediated through PERK via RPAP2, as shown by pharmacological and genetic approaches in keratinocytes expressing oncogenic HRas.","method":"Pharmacological inhibition, genetic knockdown/overexpression, phosphorylation assays in cell culture and in vivo mouse model","journal":"Molecular carcinogenesis","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — genetic and pharmacological approaches in single lab; IRE1α phosphatase activity of RPAP2 not directly demonstrated biochemically in abstract","pmids":["35975910"],"is_preprint":false},{"year":2025,"finding":"FBXW7 E3 ligase targets RPAP2 for polyubiquitylation and proteasomal degradation after RPAP2 is pre-phosphorylated at Ser562 by p38 and at Thr565 by GSK3. USP7 deubiquitylates and stabilizes RPAP2. HSP90 inhibition promotes RPAP2 degradation by CRL5-FBXW7. Hepatic-specific deletion of Fbxw7 causes cystogenesis with RPAP2 accumulation, and simultaneous Rpap2 deletion reverses cystogenesis, establishing RPAP2 as the causal downstream effector.","method":"Co-immunoprecipitation, ubiquitylation assays, site-directed mutagenesis (Ser562/Thr565), pharmacological inhibition, conditional knockout mouse model (genetic epistasis)","journal":"Advanced science","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — biochemical ubiquitylation assays with phosphosite mutagenesis, plus in vivo genetic epistasis (double knockout reversal), multiple orthogonal methods","pmids":["39932049"],"is_preprint":false},{"year":2025,"finding":"RPAP2 functions as a transcription-specific cofactor for influenza A virus polymerase, distinct from replication-specific cofactors, as identified by differential interactome screening.","method":"Differential interactome screen (comparative proteomics), functional characterization","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — preprint, single proteomics screen with limited mechanistic follow-up on RPAP2 specifically","pmids":["bio_10.1101_2025.06.06.658254"],"is_preprint":true}],"current_model":"RPAP2 (and its yeast ortholog Rtr1) is a multifunctional regulator of RNA Polymerase II that binds between RPB1 and RPB5 jaw domains (cryo-EM structure), dephosphorylates Ser5 (and Tyr1) on the CTD to drive the transition from initiation to elongation and promote transcription termination, is recruited to snRNA genes via phospho-Ser7 CTD recognition where it also recruits the Integrator complex, inhibits pre-initiation complex assembly by sterically blocking TFIIF binding, participates in Pol II biogenesis and nuclear import by coordinating Rpb1-Rpb2 assembly with Gpn3/Npa3, is targeted for degradation by the FBXW7 E3 ligase (requiring p38/GSK3 phosphorylation at Ser562/Thr565) and stabilized by USP7 deubiquitylase, and additionally acts as a PERK-dependent IRE1α phosphatase in the unfolded protein response; however, controversy persists regarding whether RPAP2/Rtr1 has intrinsic catalytic phosphatase activity or acts as a non-catalytic cofactor."},"narrative":{"mechanistic_narrative":"RPAP2 (yeast ortholog Rtr1) is a regulator of RNA Polymerase II that couples the transcription cycle to the phosphorylation state of the Pol II C-terminal domain (CTD) [PMID:19394294, PMID:22137580]. It associates with the active Pol II complex and dephosphorylates Ser5 (and, in dual-specificity assays, Tyr1) of the CTD, driving the transition from initiation to elongation and influencing transcription termination [PMID:19394294, PMID:22137580, PMID:24951832]. In human cells RPAP2 is recruited to snRNA genes through direct recognition of the phospho-Ser7 CTD mark, where it both removes Ser5 phosphorylation and recruits the Integrator complex [PMID:22137580]. Structural work places RPAP2 between the RPB1 and RPB5 jaw domains of Pol II, a position incompatible with downstream DNA engagement; through steric clashes RPAP2 blocks TFIIF binding and inhibits pre-initiation complex assembly independently of any catalytic activity, with its loss causing promoter accumulation of TFIIF and Pol II [PMID:34021257, PMID:35476980]. Beyond its CTD role, RPAP2/Rtr1 contributes to Pol II biogenesis, cooperating with assembly factors Gpn3 and Npa3 to mediate Rpb1-Rpb2 and Rpb4/7 assembly—functions that are also phosphatase-independent [PMID:36190433, PMID:35216121]. RPAP2 protein levels are controlled by FBXW7-mediated ubiquitylation following p38/GSK3 phosphorylation at Ser562/Thr565 and counteracted by USP7, a pathway whose disruption drives hepatic cystogenesis with RPAP2 as the causal effector [PMID:39932049]. Whether RPAP2/Rtr1 possesses intrinsic catalytic phosphatase activity or acts largely as a non-catalytic cofactor remains directly contested across structural and biochemical studies [PMID:22781759, PMID:24951832, PMID:26933063].","teleology":[{"year":2008,"claim":"Established that the uncharacterized factor Rtr1 is a bona fide component of the active Pol II machinery rather than a peripheral regulator, by showing physical association and genetic ties to core Pol II subunits.","evidence":"Co-IP, genetic suppressor screen, and microscopy in yeast linking Rtr1 to RPB5/RPB7/RPB9 and inducible transcription","pmids":["18408053"],"confidence":"Medium","gaps":["No molecular activity assigned","Cytoplasmic-nuclear shuttling role unexplained","No human data"]},{"year":2009,"claim":"Answered what Rtr1 does to Pol II by identifying it as a CTD Ser5 phosphatase required for the Ser5-to-Ser2 transition, defining its place in the transcription cycle.","evidence":"ChIP positioning, whole-cell phosphorylation analysis, and deletion phenotyping in yeast","pmids":["19394294"],"confidence":"High","gaps":["Intrinsic versus cofactor catalysis not resolved","No structural basis for activity","Termination defect mechanism undefined"]},{"year":2011,"claim":"Extended the model to human RPAP2 and revealed mark-directed recruitment, showing phospho-Ser7 reads RPAP2 to snRNA genes where it both removes Ser5-P and brings in Integrator.","evidence":"siRNA knockdown, ChIP, Co-IP, in vitro phosphatase assay, and Ser7Ala mutational analysis in human cells","pmids":["22137580"],"confidence":"High","gaps":["Direct Ser7-P binding determinants not mapped structurally","Integrator recruitment interface unknown"]},{"year":2012,"claim":"Challenged the phosphatase model by solving an Rtr1 structure lacking any identifiable active site and failing to detect catalytic activity in vitro, raising a non-catalytic cofactor hypothesis.","evidence":"X-ray crystallography of K. lactis Rtr1 plus extensive in vitro phosphatase assays","pmids":["22781759"],"confidence":"High","gaps":["Negative enzymatic result may reflect assay conditions","Does not exclude in vivo activity","No bound substrate"]},{"year":2014,"claim":"Reasserted intrinsic catalysis by showing autoinhibited dual-specificity (Ser5/Tyr1) activity and that an activity-reducing point mutant phenocopies deletion, directly contradicting the no-activity structural study.","evidence":"In vitro phosphatase assay, site-directed mutagenesis, and yeast complementation","pmids":["24951832"],"confidence":"High","gaps":["Conflict with prior structural study unresolved","Autoinhibition relief mechanism unknown"]},{"year":2014,"claim":"Refined recruitment logic by showing Rtr1 preferentially binds hyperphosphorylated Pol II and depends on Ser2 kinase Ctk1 for association during elongation.","evidence":"Quantitative MS interactome and affinity purification in WT and ctk1Δ yeast","pmids":["24671508"],"confidence":"Medium","gaps":["Direct Ser2-P dependence not shown biochemically","Single lab"]},{"year":2016,"claim":"Provided a structural active-site model—a phosphoryl transfer domain with a trapped sulfate—and tied active-site mutagenesis to loss of activity and growth, supporting a distinct conserved catalytic mechanism.","evidence":"2.6 Å crystal structure of S. cerevisiae Rtr1 with mutagenesis, in vitro assay, and complementation","pmids":["26933063"],"confidence":"High","gaps":["Mechanism distinct from known phosphatase families not fully defined","Persistent disagreement with negative structural study"]},{"year":2016,"claim":"Defined the genome-wide consequences of Rtr1 loss, connecting Ser5-P regulation to downstream chromatin marks via Set2-dependent H3K36me3.","evidence":"ChIP-chip of CTD phosphorylation and histone methylation in RTR1 deletion yeast","pmids":["27247267"],"confidence":"Medium","gaps":["Direct versus indirect effect on Set2 not separated","No human validation"]},{"year":2020,"claim":"Resolved how Rtr1 shapes termination, showing it restrains the NNS pathway to prevent premature termination by tuning Pcf11 versus Nrd1 association with Pol II.","evidence":"Quantitative proteomics network analysis, ChIP-seq, RNA-seq, and rrp6Δ epistasis in yeast","pmids":["32187185"],"confidence":"High","gaps":["Whether termination role requires catalysis untested","Human termination relevance unknown"]},{"year":2021,"claim":"Provided the high-resolution mammalian structural basis for RPAP2 action, locating it at the RPB1/RPB5 jaw interface in a position displaced upon PIC formation.","evidence":"2.8 Å cryo-EM of mammalian Pol II–human RPAP2 complex","pmids":["34021257"],"confidence":"High","gaps":["Catalytic engagement of CTD not captured","Functional consequence of displacement only inferred"]},{"year":2022,"claim":"Revealed a catalysis-independent function: RPAP2 sterically blocks TFIIF and inhibits PIC assembly, with depletion causing promoter Pol II/TFIIF accumulation.","evidence":"Cryo-EM, in vitro transcription, biochemical binding, and RPAP2-depletion ChIP-seq","pmids":["35476980"],"confidence":"High","gaps":["Coordination between gatekeeping and phosphatase roles unclear","How RPAP2 is removed at the right time unknown"]},{"year":2022,"claim":"Expanded RPAP2/Rtr1 function to Pol II biogenesis, showing phosphatase-independent roles in Rpb1-Rpb2 and Rpb4/7 assembly that link to nuclear import and mRNA decay.","evidence":"Genetic suppressor analysis, Co-IP, microscopy, catalytic-dead mutants, and mRNA stability assays in yeast","pmids":["36190433","35216121"],"confidence":"Medium","gaps":["Mechanistic role with Gpn3/Npa3 not structurally defined","Conservation of assembly role in humans untested"]},{"year":2022,"claim":"Identified a transcription-independent role as a PERK-dependent IRE1α phosphatase in the unfolded protein response, linking RPAP2 to stress signaling.","evidence":"Pharmacological and genetic manipulation with phosphorylation readouts in keratinocytes and mouse model","pmids":["35975910"],"confidence":"Medium","gaps":["Direct biochemical IRE1α dephosphorylation by RPAP2 not demonstrated","Relationship to Pol II role unknown","Single lab"]},{"year":2025,"claim":"Defined how RPAP2 abundance is controlled, establishing an FBXW7/USP7 ubiquitin axis gated by p38/GSK3 phosphorylation and showing RPAP2 is the causal effector of cystogenesis upon FBXW7 loss.","evidence":"Ubiquitylation assays, phosphosite mutagenesis, pharmacology, and conditional double-knockout mouse epistasis","pmids":["39932049"],"confidence":"High","gaps":["Which RPAP2 activity drives cystogenesis not pinpointed","Tissue specificity of the axis unexplained"]},{"year":null,"claim":"Whether RPAP2/Rtr1 acts through intrinsic catalytic phosphatase activity or principally as a non-catalytic cofactor/gatekeeper remains directly unresolved across its transcriptional and signaling roles.","evidence":"","pmids":[],"confidence":"High","gaps":["Conflicting structural/biochemical activity data not reconciled","Catalysis-dependent versus -independent roles not cleanly separated","Mechanistic basis of putative IRE1α phosphatase activity undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1,2,4,7]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[1,2,4]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[11,12]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,2]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,12]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[1,2,11]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[2,9,13]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[15]}],"complexes":[],"partners":["RPB1","RPB5","RPB6","INTEGRATOR","FBXW7","USP7","GPN3","NPA3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8IXW5","full_name":"Putative RNA polymerase II subunit B1 CTD phosphatase RPAP2","aliases":["RNA polymerase II-associated protein 2"],"length_aa":612,"mass_kda":69.5,"function":"Protein phosphatase that displays CTD phosphatase activity and regulates transcription of snRNA genes. Recognizes and binds phosphorylated 'Ser-7' of the C-terminal heptapeptide repeat domain (CTD) of the largest RNA polymerase II subunit POLR2A, and mediates dephosphorylation of 'Ser-5' of the CTD, thereby promoting transcription of snRNA genes (PubMed:17643375, PubMed:22137580, PubMed:24997600). Downstream of EIF2AK3/PERK, dephosphorylates ERN1, a sensor for the endoplasmic reticulum unfolded protein response (UPR), to abort failed ER-stress adaptation and trigger apoptosis (PubMed:30118681)","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/Q8IXW5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/RPAP2","classification":"Common Essential","n_dependent_lines":1093,"n_total_lines":1208,"dependency_fraction":0.9048013245033113},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000122484","cell_line_id":"CID001011","localizations":[{"compartment":"cytoplasmic","grade":3}],"interactors":[{"gene":"GPN3","stoichiometry":10.0},{"gene":"POLR2A","stoichiometry":4.0},{"gene":"POLR2B","stoichiometry":4.0},{"gene":"POLR2C","stoichiometry":4.0},{"gene":"POLR2D","stoichiometry":4.0},{"gene":"POLR2E","stoichiometry":4.0},{"gene":"POLR2K","stoichiometry":4.0},{"gene":"RPAP3","stoichiometry":4.0},{"gene":"ECT2","stoichiometry":0.2},{"gene":"POLR2F","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID001011","total_profiled":1310},"omim":[{"mim_id":"614695","title":"REGULATION OF NUCLEAR PRE-mRNA DOMAIN-CONTAINING 2; RPRD2","url":"https://www.omim.org/entry/614695"},{"mim_id":"614694","title":"REGULATION OF NUCLEAR PRE-mRNA DOMAIN-CONTAINING PROTEIN 1B; RPRD1B","url":"https://www.omim.org/entry/614694"},{"mim_id":"611479","title":"GPN-LOOP GTPase 1; GPN1","url":"https://www.omim.org/entry/611479"},{"mim_id":"611477","title":"RNA POLYMERASE II-ASSOCIATED PROTEIN 3; RPAP3","url":"https://www.omim.org/entry/611477"},{"mim_id":"611476","title":"RNA POLYMERASE II-ASSOCIATED PROTEIN 2; RPAP2","url":"https://www.omim.org/entry/611476"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoli","reliability":"Supported"},{"location":"Cytosol","reliability":"Supported"},{"location":"Primary cilium","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RPAP2"},"hgnc":{"alias_symbol":["FLJ13150","Rtr1"],"prev_symbol":["C1orf82"]},"alphafold":{"accession":"Q8IXW5","domains":[{"cath_id":"1.25.40.820","chopping":"36-112_138-176","consensus_level":"high","plddt":88.7297,"start":36,"end":176},{"cath_id":"-","chopping":"382-391_496-607","consensus_level":"high","plddt":76.0103,"start":382,"end":607}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IXW5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IXW5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IXW5-F1-predicted_aligned_error_v6.png","plddt_mean":64.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RPAP2","jax_strain_url":"https://www.jax.org/strain/search?query=RPAP2"},"sequence":{"accession":"Q8IXW5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8IXW5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8IXW5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IXW5"}},"corpus_meta":[{"pmid":"19394294","id":"PMC_19394294","title":"Rtr1 is a CTD phosphatase that regulates RNA polymerase II during the transition from serine 5 to serine 2 phosphorylation.","date":"2009","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/19394294","citation_count":121,"is_preprint":false},{"pmid":"22137580","id":"PMC_22137580","title":"Ser7 phosphorylation of the CTD recruits the RPAP2 Ser5 phosphatase to snRNA genes.","date":"2011","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/22137580","citation_count":110,"is_preprint":false},{"pmid":"22781759","id":"PMC_22781759","title":"The yeast regulator of transcription protein Rtr1 lacks an active site and phosphatase activity.","date":"2012","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/22781759","citation_count":40,"is_preprint":false},{"pmid":"24951832","id":"PMC_24951832","title":"Rtr1 is a dual specificity phosphatase that dephosphorylates Tyr1 and Ser5 on the RNA polymerase II CTD.","date":"2014","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/24951832","citation_count":38,"is_preprint":false},{"pmid":"18408053","id":"PMC_18408053","title":"Rtr1 is the Saccharomyces cerevisiae homolog of a novel family of RNA polymerase II-binding proteins.","date":"2008","source":"Eukaryotic cell","url":"https://pubmed.ncbi.nlm.nih.gov/18408053","citation_count":34,"is_preprint":false},{"pmid":"24671508","id":"PMC_24671508","title":"The interactome of the atypical phosphatase Rtr1 in Saccharomyces cerevisiae.","date":"2014","source":"Molecular bioSystems","url":"https://pubmed.ncbi.nlm.nih.gov/24671508","citation_count":31,"is_preprint":false},{"pmid":"35476980","id":"PMC_35476980","title":"RPAP2 regulates a transcription initiation checkpoint by inhibiting assembly of pre-initiation complex.","date":"2022","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/35476980","citation_count":19,"is_preprint":false},{"pmid":"25639305","id":"PMC_25639305","title":"Human RNA polymerase II-associated protein 2 (RPAP2) interacts directly with the RNA polymerase II subunit Rpb6 and participates in pre-mRNA 3'-end formation.","date":"2014","source":"Drug discoveries & therapeutics","url":"https://pubmed.ncbi.nlm.nih.gov/25639305","citation_count":17,"is_preprint":false},{"pmid":"32187185","id":"PMC_32187185","title":"RNA Polymerase II CTD phosphatase Rtr1 fine-tunes transcription termination.","date":"2020","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32187185","citation_count":15,"is_preprint":false},{"pmid":"26933063","id":"PMC_26933063","title":"Structure of Saccharomyces cerevisiae Rtr1 reveals an active site for an atypical phosphatase.","date":"2016","source":"Science signaling","url":"https://pubmed.ncbi.nlm.nih.gov/26933063","citation_count":15,"is_preprint":false},{"pmid":"34021257","id":"PMC_34021257","title":"Cryo-EM structure of mammalian RNA polymerase II in complex with human RPAP2.","date":"2021","source":"Communications biology","url":"https://pubmed.ncbi.nlm.nih.gov/34021257","citation_count":15,"is_preprint":false},{"pmid":"27247267","id":"PMC_27247267","title":"Phosphatase Rtr1 Regulates Global Levels of Serine 5 RNA Polymerase II C-Terminal Domain Phosphorylation and Cotranscriptional Histone Methylation.","date":"2016","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/27247267","citation_count":14,"is_preprint":false},{"pmid":"39932049","id":"PMC_39932049","title":"The FBXW7-RPAP2 Axis Controls the Growth of Hepatocellular Carcinoma Cells and Determines the Fate of Liver Cell Differentiation.","date":"2025","source":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/39932049","citation_count":7,"is_preprint":false},{"pmid":"36190433","id":"PMC_36190433","title":"Rtr1 is required for Rpb1-Rpb2 assembly of RNAPII and prevents their cytoplasmic clump formation.","date":"2022","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/36190433","citation_count":6,"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":"35975910","id":"PMC_35975910","title":"TGFβ1 regulates HRas-mediated activation of IRE1α through the PERK-RPAP2 axis in keratinocytes.","date":"2022","source":"Molecular carcinogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/35975910","citation_count":5,"is_preprint":false},{"pmid":"32440210","id":"PMC_32440210","title":"Active Monomer RTR-1 Derived from the Root of Rhodomyrtus t omentosa Induces Apoptosis in Gastric Carcinoma Cells by Inducing ER Stress and Inhibiting the STAT3 Signaling Pathway.","date":"2020","source":"Cancer management and research","url":"https://pubmed.ncbi.nlm.nih.gov/32440210","citation_count":4,"is_preprint":false},{"pmid":"41313435","id":"PMC_41313435","title":"Rtr1 and RPAP2: versatile players in transcription and more.","date":"2025","source":"Transcription","url":"https://pubmed.ncbi.nlm.nih.gov/41313435","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.06.06.658254","title":"Influenza A virus polymerase co-opts distinct sets of host proteins for RNA transcription or replication","date":"2025-06-06","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.06.658254","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.08.10.669560","title":"Gene co-expression network reveals key hub genes associated with endometriosis using bulk 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High-copy suppressors of rtr1Δ temperature-sensitive phenotype included core RNAPII subunits RPB5, RPB7, and RPB9, placing Rtr1 functionally within the RNAPII complex.\",\n      \"method\": \"Co-immunoprecipitation, genetic suppressor screen, growth assays, fluorescence microscopy\",\n      \"journal\": \"Eukaryotic cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal genetic and physical interaction data in single lab with multiple methods\",\n      \"pmids\": [\"18408053\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Rtr1 (yeast RPAP2 ortholog) functions as a CTD phosphatase that dephosphorylates Ser5-phosphorylated RNAPII, localizes within coding regions between the peaks of Ser5-P and Ser2-P, and is essential for the transition from Ser5 to Ser2 CTD phosphorylation during transcription elongation. Deletion of Rtr1 causes accumulation of Ser5-P RNAPII, decreased transcription, and termination defects.\",\n      \"method\": \"ChIP, whole-cell extract phosphorylation analysis, deletion mutant phenotypic analysis, functional characterization of phosphatase activity\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (ChIP, biochemical phosphatase assay, genetic deletion), replicated across subsequent studies\",\n      \"pmids\": [\"19394294\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Human RPAP2 specifically recognizes phospho-Ser7 on the Pol II CTD and is recruited to snRNA genes via this mark. RPAP2 also interacts with Integrator complex subunits and functions as a CTD Ser5 phosphatase. siRNA knockdown of RPAP2 and Ser7-to-Ala mutation cause similar defects in snRNA gene expression, indicating Ser7-P recruits RPAP2, which in turn recruits Integrator and dephosphorylates Ser5.\",\n      \"method\": \"siRNA knockdown, ChIP, co-immunoprecipitation, in vitro phosphatase assay, mutational analysis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro phosphatase assay combined with genetic (siRNA/mutation) and ChIP evidence, multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"22137580\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Crystal structure of Kluyveromyces lactis Rtr1 reveals a new type of zinc finger protein with no identifiable active site and no close structural homologues. Extensive in vitro experiments failed to detect CTD phosphatase activity, suggesting Rtr1 may have a non-catalytic role in CTD dephosphorylation.\",\n      \"method\": \"X-ray crystallography, in vitro phosphatase assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure plus extensive negative enzymatic assays; single lab but rigorous structural and biochemical methods; NEGATIVE finding regarding phosphatase activity\",\n      \"pmids\": [\"22781759\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Rtr1 is a phosphatase of new structure that is auto-inhibited by its own C-terminus. In vitro, Rtr1 dephosphorylates both Ser5 and Tyr1 on the CTD (dual specificity). A single amino acid mutation reducing activity causes the same in vivo phenotype as full gene deletion, establishing that enzymatic activity is functionally important.\",\n      \"method\": \"In vitro phosphatase assay, site-directed mutagenesis, yeast complementation assay\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with mutagenesis validated in vivo; directly contradicts the structural study (PMID:22781759) showing lack of activity\",\n      \"pmids\": [\"24951832\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Rtr1 preferentially interacts with hyperphosphorylated RNAPII as its primary binding partner in yeast. Interaction between Rtr1 and RNAPII is decreased in ctk1Δ strains lacking CTD Ser2 kinase, suggesting Ser2 CTD phosphorylation is required for Rtr1 recruitment during transcription elongation.\",\n      \"method\": \"Quantitative proteomics (mass spectrometry-based interactome), affinity purification\",\n      \"journal\": \"Molecular bioSystems\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — quantitative MS-based interactome in WT and deletion strains, single lab\",\n      \"pmids\": [\"24671508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The C-terminal region of human RPAP2 interacts directly with Pol II subunit Rpb6. RPAP2 occupies coding and 3' regions of protein-coding genes (MYC, GAPDH), and siRNA-mediated knockdown of RPAP2 causes defects in pre-mRNA 3'-end formation.\",\n      \"method\": \"Direct interaction assay (pulldown), ChIP, siRNA knockdown, RNA processing analysis\",\n      \"journal\": \"Drug discoveries & therapeutics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — direct interaction mapped to C-terminal region, combined with ChIP and functional knockdown, single lab\",\n      \"pmids\": [\"25639305\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Crystal structure of S. cerevisiae Rtr1 at 2.6 Å resolution reveals a phosphoryl transfer domain with a putative active site containing a trapped sulfate ion in a deep groove between the zinc finger domain and a pair of helices. Mutagenesis of active-site residues disrupts in vitro catalytic activity and fails to rescue growth of rtr1Δ yeast. RPAP2 and a mutant of the conserved catalytic site show similar behavior, indicating a conserved reaction mechanism distinct from other phosphatase families.\",\n      \"method\": \"X-ray crystallography (2.6 Å), site-directed mutagenesis, in vitro phosphatase assay, yeast complementation\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus mutagenesis plus in vitro activity plus in vivo rescue, multiple orthogonal methods\",\n      \"pmids\": [\"26933063\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Rtr1 is a global regulator of CTD Ser5 phosphorylation; RTR1 deletion causes genome-wide increases in Ser5-P and global increases in cotranscriptional H3K36 trimethylation, consistent with Rtr1 controlling the number of binding sites for histone methyltransferase Set2.\",\n      \"method\": \"ChIP-chip (chromatin immunoprecipitation with microarrays), genome-wide analysis of RNAPII phosphorylation\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide ChIP data in deletion strain, single lab with two orthogonal readouts (CTD phosphorylation and histone methylation)\",\n      \"pmids\": [\"27247267\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Loss of RTR1 alters interactions within the termination machinery: Rtr1 deletion decreases RNAPII-Pcf11 (CF1A subunit) interactions and increases RNAPII-Nrd1 interactions. RTR1 deletion globally increases termination at noncoding genes via the NNS (Nrd1-Nab3-Sen1) pathway and causes premature termination at protein-coding genes. Rtr1 normally restricts NNS-dependent termination to prevent premature termination.\",\n      \"method\": \"DisCo network analysis (quantitative proteomics), genome-wide ChIP-seq (RNAPII and Nrd1 occupancy), RNA-seq, genetic epistasis with rrp6Δ\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal genome-wide methods (proteomics, ChIP-seq, RNA-seq) plus genetic epistasis, single lab\",\n      \"pmids\": [\"32187185\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cryo-EM structure of mammalian Pol II in complex with human RPAP2 at 2.8 Å resolution shows RPAP2 binds between the jaw domains of RPB1 and RPB5 subunits. RPAP2 is incompatible with downstream DNA binding during transcription and is displaced upon pre-initiation complex formation.\",\n      \"method\": \"Cryo-electron microscopy (2.8 Å resolution)\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution cryo-EM structure of the mammalian complex with clear structural basis for displacement mechanism\",\n      \"pmids\": [\"34021257\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"RPAP2 binds both hypo- and hyper-phosphorylated Pol II. Cryo-EM structure of the RPAP2-Pol II complex shows mutually exclusive assembly with the pre-initiation complex (PIC) due to three steric clashes. RPAP2 prevents and disrupts Pol II-TFIIF interaction and impairs in vitro transcription initiation. Loss of RPAP2 causes global accumulation of TFIIF and Pol II at promoters, demonstrating RPAP2 inhibits PIC assembly independent of phosphatase activity.\",\n      \"method\": \"Cryo-EM structure, in vitro transcription assay, RPAP2 depletion with ChIP-seq, biochemical binding assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structure combined with in vitro transcription assay and genome-wide ChIP-seq loss-of-function, multiple orthogonal methods\",\n      \"pmids\": [\"35476980\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Rtr1 is required for assembly of the two largest RNAPII subunits (Rpb1-Rpb2) by cooperating with assembly factors Gpn3 and Npa3. RTR1 overexpression is a multicopy suppressor of gpn3, gpn2, and rba50 assembly mutants. Deletion of RTR1 leads to cytoplasmic clumping of RNAPII subunits. Notably, phosphatase-dead Rtr1 mutant does not trigger cytoplasmic clumping, indicating this assembly function is independent of phosphatase activity.\",\n      \"method\": \"Genetic suppressor analysis, co-immunoprecipitation, fluorescence microscopy, catalytically inactive mutant analysis\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis plus Co-IP plus localization imaging, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"36190433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Rtr1 mediates the association of the Rpb4/7 heterodimer with the rest of RNAPII. RTR1 deletion alters RNAPII assembly, increasing chromatin-associated RNAPII lacking Rpb4, which decreases Rpb4-mRNA imprinting and consequently increases mRNA stability. This establishes a link between Rtr1-mediated RNAPII assembly and mRNA decay regulation.\",\n      \"method\": \"Co-immunoprecipitation, ChIP, mRNA stability assays, genetic deletion analysis\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — multiple methods (Co-IP, ChIP, RNA stability) in single lab linking assembly defect to mRNA decay\",\n      \"pmids\": [\"35216121\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"RPAP2 functions as a PERK-dependent IRE1α phosphatase in the unfolded protein response. TGFβ1-mediated dephosphorylation of IRE1α is mediated through PERK via RPAP2, as shown by pharmacological and genetic approaches in keratinocytes expressing oncogenic HRas.\",\n      \"method\": \"Pharmacological inhibition, genetic knockdown/overexpression, phosphorylation assays in cell culture and in vivo mouse model\",\n      \"journal\": \"Molecular carcinogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — genetic and pharmacological approaches in single lab; IRE1α phosphatase activity of RPAP2 not directly demonstrated biochemically in abstract\",\n      \"pmids\": [\"35975910\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"FBXW7 E3 ligase targets RPAP2 for polyubiquitylation and proteasomal degradation after RPAP2 is pre-phosphorylated at Ser562 by p38 and at Thr565 by GSK3. USP7 deubiquitylates and stabilizes RPAP2. HSP90 inhibition promotes RPAP2 degradation by CRL5-FBXW7. Hepatic-specific deletion of Fbxw7 causes cystogenesis with RPAP2 accumulation, and simultaneous Rpap2 deletion reverses cystogenesis, establishing RPAP2 as the causal downstream effector.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitylation assays, site-directed mutagenesis (Ser562/Thr565), pharmacological inhibition, conditional knockout mouse model (genetic epistasis)\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — biochemical ubiquitylation assays with phosphosite mutagenesis, plus in vivo genetic epistasis (double knockout reversal), multiple orthogonal methods\",\n      \"pmids\": [\"39932049\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"RPAP2 functions as a transcription-specific cofactor for influenza A virus polymerase, distinct from replication-specific cofactors, as identified by differential interactome screening.\",\n      \"method\": \"Differential interactome screen (comparative proteomics), functional characterization\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — preprint, single proteomics screen with limited mechanistic follow-up on RPAP2 specifically\",\n      \"pmids\": [\"bio_10.1101_2025.06.06.658254\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"RPAP2 (and its yeast ortholog Rtr1) is a multifunctional regulator of RNA Polymerase II that binds between RPB1 and RPB5 jaw domains (cryo-EM structure), dephosphorylates Ser5 (and Tyr1) on the CTD to drive the transition from initiation to elongation and promote transcription termination, is recruited to snRNA genes via phospho-Ser7 CTD recognition where it also recruits the Integrator complex, inhibits pre-initiation complex assembly by sterically blocking TFIIF binding, participates in Pol II biogenesis and nuclear import by coordinating Rpb1-Rpb2 assembly with Gpn3/Npa3, is targeted for degradation by the FBXW7 E3 ligase (requiring p38/GSK3 phosphorylation at Ser562/Thr565) and stabilized by USP7 deubiquitylase, and additionally acts as a PERK-dependent IRE1α phosphatase in the unfolded protein response; however, controversy persists regarding whether RPAP2/Rtr1 has intrinsic catalytic phosphatase activity or acts as a non-catalytic cofactor.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RPAP2 (yeast ortholog Rtr1) is a regulator of RNA Polymerase II that couples the transcription cycle to the phosphorylation state of the Pol II C-terminal domain (CTD) [#1, #2]. It associates with the active Pol II complex and dephosphorylates Ser5 (and, in dual-specificity assays, Tyr1) of the CTD, driving the transition from initiation to elongation and influencing transcription termination [#1, #2, #4]. In human cells RPAP2 is recruited to snRNA genes through direct recognition of the phospho-Ser7 CTD mark, where it both removes Ser5 phosphorylation and recruits the Integrator complex [#2]. Structural work places RPAP2 between the RPB1 and RPB5 jaw domains of Pol II, a position incompatible with downstream DNA engagement; through steric clashes RPAP2 blocks TFIIF binding and inhibits pre-initiation complex assembly independently of any catalytic activity, with its loss causing promoter accumulation of TFIIF and Pol II [#10, #11]. Beyond its CTD role, RPAP2/Rtr1 contributes to Pol II biogenesis, cooperating with assembly factors Gpn3 and Npa3 to mediate Rpb1-Rpb2 and Rpb4/7 assembly—functions that are also phosphatase-independent [#12, #13]. RPAP2 protein levels are controlled by FBXW7-mediated ubiquitylation following p38/GSK3 phosphorylation at Ser562/Thr565 and counteracted by USP7, a pathway whose disruption drives hepatic cystogenesis with RPAP2 as the causal effector [#15]. Whether RPAP2/Rtr1 possesses intrinsic catalytic phosphatase activity or acts largely as a non-catalytic cofactor remains directly contested across structural and biochemical studies [#3, #4, #7].\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Established that the uncharacterized factor Rtr1 is a bona fide component of the active Pol II machinery rather than a peripheral regulator, by showing physical association and genetic ties to core Pol II subunits.\",\n      \"evidence\": \"Co-IP, genetic suppressor screen, and microscopy in yeast linking Rtr1 to RPB5/RPB7/RPB9 and inducible transcription\",\n      \"pmids\": [\"18408053\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No molecular activity assigned\", \"Cytoplasmic-nuclear shuttling role unexplained\", \"No human data\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Answered what Rtr1 does to Pol II by identifying it as a CTD Ser5 phosphatase required for the Ser5-to-Ser2 transition, defining its place in the transcription cycle.\",\n      \"evidence\": \"ChIP positioning, whole-cell phosphorylation analysis, and deletion phenotyping in yeast\",\n      \"pmids\": [\"19394294\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Intrinsic versus cofactor catalysis not resolved\", \"No structural basis for activity\", \"Termination defect mechanism undefined\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Extended the model to human RPAP2 and revealed mark-directed recruitment, showing phospho-Ser7 reads RPAP2 to snRNA genes where it both removes Ser5-P and brings in Integrator.\",\n      \"evidence\": \"siRNA knockdown, ChIP, Co-IP, in vitro phosphatase assay, and Ser7Ala mutational analysis in human cells\",\n      \"pmids\": [\"22137580\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct Ser7-P binding determinants not mapped structurally\", \"Integrator recruitment interface unknown\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Challenged the phosphatase model by solving an Rtr1 structure lacking any identifiable active site and failing to detect catalytic activity in vitro, raising a non-catalytic cofactor hypothesis.\",\n      \"evidence\": \"X-ray crystallography of K. lactis Rtr1 plus extensive in vitro phosphatase assays\",\n      \"pmids\": [\"22781759\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Negative enzymatic result may reflect assay conditions\", \"Does not exclude in vivo activity\", \"No bound substrate\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Reasserted intrinsic catalysis by showing autoinhibited dual-specificity (Ser5/Tyr1) activity and that an activity-reducing point mutant phenocopies deletion, directly contradicting the no-activity structural study.\",\n      \"evidence\": \"In vitro phosphatase assay, site-directed mutagenesis, and yeast complementation\",\n      \"pmids\": [\"24951832\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conflict with prior structural study unresolved\", \"Autoinhibition relief mechanism unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Refined recruitment logic by showing Rtr1 preferentially binds hyperphosphorylated Pol II and depends on Ser2 kinase Ctk1 for association during elongation.\",\n      \"evidence\": \"Quantitative MS interactome and affinity purification in WT and ctk1\\u0394 yeast\",\n      \"pmids\": [\"24671508\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct Ser2-P dependence not shown biochemically\", \"Single lab\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Provided a structural active-site model—a phosphoryl transfer domain with a trapped sulfate—and tied active-site mutagenesis to loss of activity and growth, supporting a distinct conserved catalytic mechanism.\",\n      \"evidence\": \"2.6 \\u00c5 crystal structure of S. cerevisiae Rtr1 with mutagenesis, in vitro assay, and complementation\",\n      \"pmids\": [\"26933063\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism distinct from known phosphatase families not fully defined\", \"Persistent disagreement with negative structural study\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined the genome-wide consequences of Rtr1 loss, connecting Ser5-P regulation to downstream chromatin marks via Set2-dependent H3K36me3.\",\n      \"evidence\": \"ChIP-chip of CTD phosphorylation and histone methylation in RTR1 deletion yeast\",\n      \"pmids\": [\"27247267\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct versus indirect effect on Set2 not separated\", \"No human validation\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Resolved how Rtr1 shapes termination, showing it restrains the NNS pathway to prevent premature termination by tuning Pcf11 versus Nrd1 association with Pol II.\",\n      \"evidence\": \"Quantitative proteomics network analysis, ChIP-seq, RNA-seq, and rrp6\\u0394 epistasis in yeast\",\n      \"pmids\": [\"32187185\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether termination role requires catalysis untested\", \"Human termination relevance unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Provided the high-resolution mammalian structural basis for RPAP2 action, locating it at the RPB1/RPB5 jaw interface in a position displaced upon PIC formation.\",\n      \"evidence\": \"2.8 \\u00c5 cryo-EM of mammalian Pol II\\u2013human RPAP2 complex\",\n      \"pmids\": [\"34021257\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Catalytic engagement of CTD not captured\", \"Functional consequence of displacement only inferred\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Revealed a catalysis-independent function: RPAP2 sterically blocks TFIIF and inhibits PIC assembly, with depletion causing promoter Pol II/TFIIF accumulation.\",\n      \"evidence\": \"Cryo-EM, in vitro transcription, biochemical binding, and RPAP2-depletion ChIP-seq\",\n      \"pmids\": [\"35476980\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Coordination between gatekeeping and phosphatase roles unclear\", \"How RPAP2 is removed at the right time unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Expanded RPAP2/Rtr1 function to Pol II biogenesis, showing phosphatase-independent roles in Rpb1-Rpb2 and Rpb4/7 assembly that link to nuclear import and mRNA decay.\",\n      \"evidence\": \"Genetic suppressor analysis, Co-IP, microscopy, catalytic-dead mutants, and mRNA stability assays in yeast\",\n      \"pmids\": [\"36190433\", \"35216121\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic role with Gpn3/Npa3 not structurally defined\", \"Conservation of assembly role in humans untested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified a transcription-independent role as a PERK-dependent IRE1\\u03b1 phosphatase in the unfolded protein response, linking RPAP2 to stress signaling.\",\n      \"evidence\": \"Pharmacological and genetic manipulation with phosphorylation readouts in keratinocytes and mouse model\",\n      \"pmids\": [\"35975910\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct biochemical IRE1\\u03b1 dephosphorylation by RPAP2 not demonstrated\", \"Relationship to Pol II role unknown\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defined how RPAP2 abundance is controlled, establishing an FBXW7/USP7 ubiquitin axis gated by p38/GSK3 phosphorylation and showing RPAP2 is the causal effector of cystogenesis upon FBXW7 loss.\",\n      \"evidence\": \"Ubiquitylation assays, phosphosite mutagenesis, pharmacology, and conditional double-knockout mouse epistasis\",\n      \"pmids\": [\"39932049\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which RPAP2 activity drives cystogenesis not pinpointed\", \"Tissue specificity of the axis unexplained\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether RPAP2/Rtr1 acts through intrinsic catalytic phosphatase activity or principally as a non-catalytic cofactor/gatekeeper remains directly unresolved across its transcriptional and signaling roles.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conflicting structural/biochemical activity data not reconciled\", \"Catalysis-dependent versus -independent roles not cleanly separated\", \"Mechanistic basis of putative IRE1\\u03b1 phosphatase activity undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 2, 4, 7]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [1, 2, 4]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [11, 12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 12]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [1, 2, 11]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [2, 9, 13]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [15]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"RPB1\", \"RPB5\", \"RPB6\", \"Integrator\", \"FBXW7\", \"USP7\", \"Gpn3\", \"Npa3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}