{"gene":"CTR9","run_date":"2026-06-09T22:57:19","timeline":{"discoveries":[{"year":2002,"finding":"Ctr9 is a component of the Paf1/RNA polymerase II complex (Paf1C), distinct from the Srb-mediator form of Pol II holoenzyme. Tandem affinity purification and mass spectrometry established that Ctr9 associates with Paf1, Cdc73, Leo1, Rtf1, and Pol II. Genetic epistasis showed deletion of PAF1 or CTR9 produces similar severe pleiotropic phenotypes that are not additive when combined, placing them in the same pathway.","method":"Tandem affinity purification, mass spectrometry, genetic epistasis (double-deletion analysis)","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — biochemical purification with MS identification plus genetic epistasis, foundational paper replicated across many subsequent studies","pmids":["11884586"],"is_preprint":false},{"year":1996,"finding":"CTR9/p150TSP is a nuclear phosphoprotein containing multiple tetratricopeptide repeat (TPR) domains that binds specifically to SH2 domains. The TPR module mediates homotypic protein-protein interactions in transfected cells. The C-terminal serine/glutamic acid-rich region is essential for SH2 binding, which depends on serine/threonine phosphorylation but not tyrosine phosphorylation.","method":"Biochemical purification from B cell lysates, cDNA cloning, transfection with deletion mutants, phosphorylation-dependent binding assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding assays with deletion mutagenesis in a single study; foundational characterization of domain architecture","pmids":["8636124"],"is_preprint":false},{"year":2018,"finding":"Crystal structures of both human and yeast Ctr9/Paf1 subcomplexes reveal that they assemble into heterodimers with similar conformations via an interface between the TPR module of Ctr9 and Paf1. Formation of the Ctr9/Paf1 heterodimer is required for assembly of the full yeast Paf1C and for yeast viability. Disruption of this interface greatly reduces histone H3 methylation in vivo.","method":"Crystal structure determination (X-ray crystallography), interface mutagenesis, yeast viability assay, histone modification analysis in vivo","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures of both human and yeast subcomplexes plus mutagenesis and in vivo functional validation in a single rigorous study","pmids":["30228257"],"is_preprint":false},{"year":2013,"finding":"CTR9 (as part of PAFc) constitutively associates with the 5'-coding region of the c-Fos locus and controls the elongation block by regulating NELF and SPT5 chromatin association. CTR9 depletion increases serine 5- and serine 2-phosphorylated Pol II at the unstimulated c-Fos locus, increases CDK9 association, reduces NELF binding, and enhances SPT5 recruitment. IL-6-induced JAK2 kinase activity controls CTR9 chromatin dissociation at this locus.","method":"ChIP assay, siRNA knockdown, kinase inhibitor (AG-490) treatment, analysis of Pol II phosphorylation states","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP with multiple targets and pharmacological inhibition in a single lab study","pmids":["23593388"],"is_preprint":false},{"year":2013,"finding":"Ctr9 knockdown in mouse preimplantation embryos causes loss of histone H3K36me3, failure to correctly specify ICM/TE lineages at the blastocyst stage, and aberrant expression of imprinted genes without altering allele-specific DNA methylation. These phenotypes are similar to those produced by knockdown of Setd2 (the H3K36me3 writer) or Rtf1.","method":"siRNA knockdown in mouse embryos, immunofluorescence for H3K36me3, allele-specific expression analysis, genetic epistasis with Setd2 and Rtf1 knockdown","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined epigenetic and developmental phenotypes, epistasis with Setd2, single lab","pmids":["24036311"],"is_preprint":false},{"year":2015,"finding":"Ctr9 enhances ERα protein stability, promotes recruitment of ERα and RNAPII to estrogen-regulated loci, and stimulates transcription elongation and transcription-coupled histone modifications in ERα+ breast cancer cells. Knockdown of Ctr9 (but not other PAFc subunits) nearly completely erases estrogen-regulated transcriptional response and alters cell morphology, proliferative capacity, and tamoxifen sensitivity.","method":"siRNA knockdown, ChIP, co-immunoprecipitation, ERα stability assay, transcriptome analysis, cell proliferation and morphology assays","journal":"Genes & development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (ChIP, IP, protein stability, transcriptome) in a single lab; subunit-specificity established by parallel knockdown of other PAFc members","pmids":["26494790"],"is_preprint":false},{"year":2016,"finding":"Loss of Ctr9 in the Drosophila nervous system (null mutant) reduces global H3K4me3 levels, increases neuroblast numbers and nervous system proliferation, and downregulates neuropeptide genes; it also upregulates E2f1 and alters Notch pathway target gene expression. A human CTR9 cDNA transgene rescues lethality of the Drosophila Ctr9 null mutant, demonstrating functional conservation.","method":"Drosophila null mutation, human cDNA rescue transgene, immunostaining for H3K4me3, genome-wide transcriptome analysis, clonal analysis","journal":"G3 (Bethesda, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — null mutant with defined epigenetic phenotype, cross-species rescue, multiple orthogonal readouts, single lab","pmids":["27520958"],"is_preprint":false},{"year":2016,"finding":"Drosophila CG2469 encodes a functional Ctr9 homolog; both human and Drosophila Ctr9 localize to nuclei and are enriched in histone locus bodies. Null mutation of Drosophila Ctr9 causes lethality and reduces global H3K4me3 in ovary clones. A human CTR9 cDNA transgene rescues the lethality, confirming functional conservation.","method":"Sequence analysis, nuclear localization by immunofluorescence, null mutation analysis, H3K4me3 immunostaining in clones, human cDNA rescue","journal":"G3 (Bethesda, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — null mutant with histone modification readout plus cross-species rescue; single lab","pmids":["27678520"],"is_preprint":false},{"year":2015,"finding":"Ctr9 physically interacts with the dopamine transporter (DAT) via residues YKF in the first half of the DAT C-terminus, as demonstrated by yeast two-hybrid, GST pulldown, and co-immunoprecipitation. In mammalian cells, Ctr9 partially colocalizes with DAT at the plasma membrane and dramatically enhances DAT-mediated dopamine uptake by increasing the number of DAT transporters at the plasma membrane. Deletion mutagenesis demonstrated that the SH2 domain of Ctr9 is required for its nuclear localization.","method":"Yeast two-hybrid, GST pulldown, co-immunoprecipitation, co-localization imaging, dopamine uptake assay, deletion mutagenesis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal binding assays (YTH, pulldown, Co-IP) plus functional uptake assay and mutagenesis; single lab","pmids":["26048990"],"is_preprint":false},{"year":2014,"finding":"CTR9 occupies the coding region of the Il17a gene in naive T cells and dissociates under Th17-polarizing conditions; its depletion induces IL-17 expression and enhances Th17 differentiation. IL-6 directly represses CTR9 promoter activity, creating a feed-forward loop. Lentiviral CTR9 overexpression in joints of collagen-induced arthritis mice reduced arthritis severity and CD4+IL-17+ T cell frequency.","method":"ChIP assay, siRNA knockdown, promoter reporter assay, lentiviral overexpression in vivo (mouse arthritis model), flow cytometry","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP, KD, promoter assay, and in vivo overexpression with defined phenotypic readouts; single lab","pmids":["24420920"],"is_preprint":false},{"year":2018,"finding":"In yeast, Paf1 and Ctr9 (core PAF1C subunits) specifically maintain low levels of telomere repeat-containing RNA (TERRA), while Cdc73, Leo1, and Rtf1 have lesser effects. Double-mutant analysis showed Paf1 and Ctr9 can regulate TERRA independently of Sir4, Rat1, and Trf4 (previously known TERRA regulators), and the data suggest they do so by affecting both transcription and degradation of TERRA.","method":"Northern blot/TERRA quantification in deletion mutants, genetic epistasis (double mutants with sir4Δ, rat1Δ, trf4Δ)","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis analysis in multiple double mutants with direct TERRA measurement; single lab","pmids":["29145644"],"is_preprint":false},{"year":2022,"finding":"CTR9 controls genome-wide H3K27me3 levels by regulating PRC2 subtype equilibrium. Loss of CTR9 leads to global expansion of H3K27me3, increased PRC2 chromatin recruitment, and a switch from the less active PRC2.2 to the more active PRC2.1 subtype. These effects are reversed by CTR9 restoration, and CTR9 depletion renders breast cancer cells hypersensitive to PRC2 inhibitors.","method":"Inducible and stable CTR9 knockdown, quantitative histone modification profiling, ChIP-seq for H3K27me3 and PRC2 subunits, PRC2 subtype biochemical analysis, cell viability assays with PRC2 inhibitors","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (ChIP-seq, quantitative histone profiling, inhibitor sensitivity) with rescue experiment; single lab","pmids":["35137163"],"is_preprint":false},{"year":2022,"finding":"CTR9 counteracts EZH2-mediated H3K27me3 deposition in human mesenchymal stem cells. CTR9 knockdown causes gain of H3K27me3 and blocks osteoblast/chondrocyte differentiation; this block is partially rescued by EZH2 inhibitors. CTR9 regulates BMP-2 secretion and membrane anchorage, and the BMP-SMAD pathway is impaired by CTR9 knockdown but rescued by BMP-2 supplementation.","method":"siRNA knockdown, EZH2 inhibitor rescue, ChIP for H3K27me3, BMP-2 supplementation rescue, in vivo ectopic osteogenesis assay, transcriptome analysis","journal":"Science advances","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple rescue experiments (EZH2 inhibitor, BMP-2 supplementation) plus in vivo osteogenesis and epigenetic profiling; single lab","pmids":["36383652"],"is_preprint":false},{"year":2021,"finding":"CTR9 promotes transcription of the oncogene PEG10 via its promoter region in hepatocellular carcinoma cells. CTR9 knockdown reduces PEG10 expression, increases p21 and p27, and decreases MMP2/MMP9, while overexpression has the opposite effects. These oncogenic roles were confirmed in a xenograft mouse model.","method":"siRNA knockdown, CTR9 overexpression, promoter reporter assay, western blot, xenograft mouse model","journal":"Acta pharmacologica Sinica","confidence":"Low","confidence_rationale":"Tier 3 / Moderate — functional KD/OE with downstream target identification, but mechanistic link to CTR9 direct transcriptional activity at PEG10 promoter is only partially resolved","pmids":["34876700"],"is_preprint":false},{"year":2023,"finding":"SIAH1 physically interacts with CTR9 (identified by yeast two-hybrid and confirmed by co-immunoprecipitation) and ubiquitinates CTR9 via K48-linked polyubiquitination, leading to proteasomal degradation of CTR9 in HCC cells. SIAH1 inhibits EMT of HCC cells through negative regulation of CTR9 protein levels.","method":"Yeast two-hybrid, co-immunoprecipitation, ubiquitination assay (K48-linkage specificity), proteasome inhibitor assay, EMT functional assays","journal":"Carcinogenesis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal interaction assays plus ubiquitination linkage specificity and proteasome pathway confirmation; single lab","pmids":["37038329"],"is_preprint":false},{"year":2016,"finding":"Genome-wide ChIP-seq demonstrated that Ctr9 knockdown dramatically decreases global chromatin occupancy of ERα and RNAPII in response to estrogen in ERα+ breast cancer cells, establishing that Ctr9 controls ERα-target gene expression by regulating global ERα and RNAPII chromatin binding, independently of other PAFc subunits.","method":"ChIP-seq for ERα and RNAPII, inducible Ctr9 knockdown, parallel knockdown of other PAFc subunits","journal":"BMC genomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genome-wide ChIP-seq with subunit-specificity controls; single lab extending prior findings","pmids":["27829357"],"is_preprint":false},{"year":2022,"finding":"De novo CTR9 missense variants (p.Glu15Asp, p.Pro25Arg) associated with neurodevelopmental disorder show stronger affinity to PAF1 protein in pull-down assays compared to wild-type CTR9. In zebrafish, ctr9 knockout causes motor defects and telencephalon enlargement; introduction of human CTR9 mutants failed to rescue these phenotypes, and mutant mRNA overexpression caused telencephalon enlargement, indicating dominant-negative activity.","method":"Pull-down assay (mutant vs wild-type binding to PAF1), zebrafish ctr9 knockout, human CTR9 mRNA rescue experiment, overexpression of mutant mRNA in zebrafish","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro binding assay combined with zebrafish KO rescue experiment and dominant-negative overexpression; single lab, two orthogonal model systems","pmids":["35717577"],"is_preprint":false},{"year":2012,"finding":"Proteome analysis of a ctr9Δ yeast strain by 2D gel electrophoresis revealed proteome changes not fully explained by Paf1C functions, and Ctr9 has been described as a triple-helical DNA binding protein, suggesting functions independent of the Paf1 complex.","method":"2D gel electrophoresis proteomics of ctr9Δ yeast strain","journal":"Biochimica et biophysica acta","confidence":"Low","confidence_rationale":"Tier 3 / Weak — proteomics screen suggesting independent function but without direct mechanistic validation of the specific pathway","pmids":["22446411"],"is_preprint":false}],"current_model":"CTR9 is the scaffold/core subunit of the evolutionarily conserved PAF1 complex (PAF1C), where it forms a structurally defined heterodimer with PAF1 via its TPR domain that is essential for full complex assembly; within PAF1C, CTR9 associates with RNA Polymerase II and promotes transcription elongation, couples active transcription to histone modifications (H3K4me3, H3K36me3), restrains repressive H3K27me3 by limiting PRC2.1 activity, regulates NELF/SPT5 occupancy at specific loci to control elongation pausing, and can also localize outside the nucleus to regulate dopamine transporter trafficking; CTR9 protein stability is controlled by SIAH1-mediated K48-linked ubiquitination and proteasomal degradation, and loss-of-function variants in CTR9 cause Wilms tumor predisposition and neurodevelopmental disorders."},"narrative":{"mechanistic_narrative":"CTR9 is the scaffold subunit of the evolutionarily conserved PAF1 complex (PAF1C), where it associates with Paf1, Cdc73, Leo1, Rtf1, and RNA Polymerase II to couple transcription elongation to chromatin modification [PMID:11884586]. Through its tetratricopeptide-repeat (TPR) module, CTR9 forms a structurally defined heterodimer with PAF1 — an interface resolved in both human and yeast crystal structures whose disruption abolishes full PAF1C assembly, yeast viability, and histone H3 methylation in vivo [PMID:8636124, PMID:30228257]. Within this complex CTR9 promotes deposition of active histone marks H3K4me3 and H3K36me3, a function conserved from Drosophila to mammals such that human CTR9 cDNA rescues lethality of the Drosophila null mutant [PMID:24036311, PMID:27520958, PMID:27678520]. CTR9 also restrains the repressive mark H3K27me3 by limiting PRC2 chromatin recruitment and shifting the PRC2 subtype equilibrium away from the more active PRC2.1, a balance whose loss sensitizes breast cancer cells to PRC2 inhibitors and blocks mesenchymal stem cell differentiation [PMID:35137163, PMID:36383652]. At specific loci CTR9 controls Pol II elongation by regulating NELF and SPT5 chromatin occupancy and the elongation block, with cytokine signaling (IL-6/JAK2) driving its locus dissociation [PMID:23593388, PMID:24420920]. Beyond transcription, CTR9 enhances ERα protein stability and global ERα/RNAPII chromatin binding to drive estrogen-regulated transcription [PMID:26494790, PMID:27829357], and acts at the plasma membrane to enhance dopamine transporter surface levels and uptake [PMID:26048990]. CTR9 protein abundance is controlled by SIAH1-mediated K48-linked polyubiquitination and proteasomal degradation [PMID:37038329], and de novo CTR9 variants that act as dominant-negative alleles cause neurodevelopmental phenotypes in zebrafish models [PMID:35717577].","teleology":[{"year":1996,"claim":"Before its complex membership was known, CTR9 was defined as a nuclear TPR-domain phosphoprotein, establishing the domain architecture (TPR module mediating protein-protein interactions; C-terminal SH2-binding region) that would later underlie its scaffolding role.","evidence":"Biochemical purification from B cell lysates, cDNA cloning, and phosphorylation-dependent binding assays with deletion mutants","pmids":["8636124"],"confidence":"Medium","gaps":["Functional consequence of SH2-domain binding not connected to a pathway","No structural model of the TPR module at this stage"]},{"year":2002,"claim":"Established CTR9 as a bona fide subunit of the Paf1/RNA Pol II complex distinct from the Srb-mediator holoenzyme, defining its core biological context.","evidence":"Tandem affinity purification, mass spectrometry, and genetic epistasis (non-additive PAF1/CTR9 double deletion) in yeast","pmids":["11884586"],"confidence":"High","gaps":["Did not resolve which subunit interactions are direct","Molecular function of CTR9 within the complex not separated from other subunits"]},{"year":2013,"claim":"Answered how CTR9 contributes to elongation control by showing it regulates the elongation block at specific loci through NELF/SPT5 occupancy and Pol II phosphorylation, linking it to signal-responsive gene activation.","evidence":"ChIP, siRNA knockdown, and JAK2 inhibition at the c-Fos locus in mammalian cells","pmids":["23593388"],"confidence":"Medium","gaps":["Locus-specific; not shown to be genome-wide","Direct vs indirect effect on NELF/SPT5 binding not distinguished"]},{"year":2013,"claim":"Connected CTR9 to a specific active chromatin mark and developmental output by linking it to H3K36me3 deposition required for lineage specification.","evidence":"siRNA knockdown in mouse preimplantation embryos with H3K36me3 immunofluorescence and epistasis with Setd2/Rtf1","pmids":["24036311"],"confidence":"Medium","gaps":["Mechanism of imprinted-gene misregulation without DNA methylation change unresolved","Whether effect requires full PAF1C not tested"]},{"year":2014,"claim":"Showed CTR9 acts as a brake on Th17 differentiation by occupying the Il17a coding region, with IL-6 repressing CTR9 in a feed-forward loop, establishing an immunoregulatory role.","evidence":"ChIP, knockdown, promoter reporter, and lentiviral overexpression in a mouse arthritis model","pmids":["24420920"],"confidence":"Medium","gaps":["Mechanism of CTR9 dissociation under Th17 polarization unclear","Whether repression involves histone marks not addressed"]},{"year":2015,"claim":"Revealed PAF1C-independent and complex-dependent activities: CTR9 stabilizes ERα protein and drives estrogen-regulated transcription, while a separate cytoplasmic role enhances dopamine transporter surface expression.","evidence":"ChIP, Co-IP, ERα stability and transcriptome assays in breast cancer cells; yeast two-hybrid, GST pulldown, Co-IP, and dopamine uptake assays for DAT","pmids":["26494790","26048990"],"confidence":"Medium","gaps":["Mechanism by which CTR9 stabilizes ERα protein not defined","How nuclear vs plasma-membrane localization is partitioned unresolved"]},{"year":2016,"claim":"Demonstrated functional conservation and a link to H3K4me3, with human CTR9 rescuing Drosophila null lethality and loss reducing global H3K4me3 and disrupting neural proliferation.","evidence":"Drosophila null mutants, human cDNA rescue, H3K4me3 immunostaining, and transcriptome/clonal analysis; genome-wide ChIP-seq of ERα/RNAPII in breast cancer","pmids":["27520958","27678520","27829357"],"confidence":"Medium","gaps":["Direct enzymatic link between CTR9 and the H3K4 methyltransferase not established","Whether neural phenotypes are cell-autonomous unresolved"]},{"year":2018,"claim":"Provided the structural basis for CTR9 function, showing the TPR module/PAF1 heterodimer interface is required for full complex assembly, viability, and histone methylation.","evidence":"Crystal structures of human and yeast Ctr9/Paf1 subcomplexes with interface mutagenesis and in vivo validation; TERRA quantification in yeast deletion mutants","pmids":["30228257","29145644"],"confidence":"High","gaps":["Structure of full PAF1C bound to Pol II not resolved","Mechanism by which Paf1/Ctr9 specifically suppress TERRA not defined"]},{"year":2022,"claim":"Defined CTR9 as a regulator of repressive chromatin by showing it limits PRC2 recruitment and biases the PRC2 subtype equilibrium, with therapeutic and differentiation consequences.","evidence":"Inducible knockdown, H3K27me3/PRC2 ChIP-seq, PRC2-subtype biochemistry, inhibitor sensitivity, and EZH2/BMP-2 rescue with in vivo osteogenesis; pull-down and zebrafish KO/rescue for NDD variants","pmids":["35137163","36383652","35717577"],"confidence":"Medium","gaps":["Molecular mechanism by which CTR9 antagonizes PRC2 recruitment unresolved","How dominant-negative variants perturb PAF1C function in vivo not detailed"]},{"year":2023,"claim":"Identified the post-translational control of CTR9 abundance, showing SIAH1 ubiquitinates CTR9 via K48 linkages for proteasomal degradation, coupling CTR9 levels to EMT control.","evidence":"Yeast two-hybrid, Co-IP, K48-linkage-specific ubiquitination and proteasome inhibition assays, EMT functional readouts in HCC cells","pmids":["37038329"],"confidence":"Medium","gaps":["Signals controlling SIAH1-mediated CTR9 turnover not defined","Whether degradation targets free CTR9 or assembled PAF1C unresolved"]},{"year":null,"claim":"It remains unresolved how CTR9's distinct activities — active-mark deposition, PRC2 antagonism, elongation pausing control, ERα stabilization, and cytoplasmic DAT regulation — are mechanistically partitioned and which require intact PAF1C versus independent CTR9 function.","evidence":"No single study in the corpus reconciles the nuclear PAF1C-dependent and complex-independent roles","pmids":[],"confidence":"Low","gaps":["No reconstitution dissecting complex-dependent vs independent CTR9 activities","Triple-helical DNA binding activity not mechanistically validated","Genome-wide direct target map distinguishing CTR9-specific from PAF1C-shared functions lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1,2]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[3,5,13]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[1,7,8]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[8]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,3,5]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[2,4,6,11]}],"complexes":["PAF1 complex (PAF1C)"],"partners":["PAF1","CDC73","LEO1","RTF1","RNA POL II","SIAH1","SLC6A3","ESR1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q6PD62","full_name":"RNA polymerase-associated protein CTR9 homolog","aliases":["SH2 domain-binding protein 1"],"length_aa":1173,"mass_kda":133.5,"function":"Component of the PAF1 complex (PAF1C) which has multiple functions during transcription by RNA polymerase II and is implicated in regulation of development and maintenance of embryonic stem cell pluripotency. PAF1C associates with RNA polymerase II through interaction with POLR2A CTD non-phosphorylated and 'Ser-2'- and 'Ser-5'-phosphorylated forms and is involved in transcriptional elongation, acting both independently and synergistically with TCEA1 and in cooperation with the DSIF complex and HTATSF1. PAF1C is required for transcription of Hox and Wnt target genes. PAF1C is involved in hematopoiesis and stimulates transcriptional activity of KMT2A/MLL1; it promotes leukemogenesis through association with KMT2A/MLL1-rearranged oncoproteins, such as KMT2A/MLL1-MLLT3/AF9 and KMT2A/MLL1-MLLT1/ENL. PAF1C is involved in histone modifications such as ubiquitination of histone H2B and methylation on histone H3 'Lys-4' (H3K4me3). PAF1C recruits the RNF20/40 E3 ubiquitin-protein ligase complex and the E2 enzyme UBE2A or UBE2B to chromatin which mediate monoubiquitination of 'Lys-120' of histone H2B (H2BK120ub1); UB2A/B-mediated H2B ubiquitination is proposed to be coupled to transcription. PAF1C is involved in mRNA 3' end formation probably through association with cleavage and poly(A) factors. In case of infection by influenza A strain H3N2, PAF1C associates with viral NS1 protein, thereby regulating gene transcription. Required for mono- and trimethylation on histone H3 'Lys-4' (H3K4me3) and dimethylation on histone H3 'Lys-79' (H3K4me3). Required for Hox gene transcription. Required for the trimethylation of histone H3 'Lys-4' (H3K4me3) on genes involved in stem cell pluripotency; this function is synergistic with CXXC1 indicative for an involvement of the SET1 complex. Involved in transcriptional regulation of IL6-responsive genes and in JAK-STAT pathway; may regulate DNA-association of STAT3 (By similarity)","subcellular_location":"Nucleus speckle","url":"https://www.uniprot.org/uniprotkb/Q6PD62/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/CTR9","classification":"Common Essential","n_dependent_lines":1124,"n_total_lines":1208,"dependency_fraction":0.9304635761589404},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SSRP1","stoichiometry":4.0},{"gene":"CPSF6","stoichiometry":0.2},{"gene":"CSNK2B","stoichiometry":0.2},{"gene":"DDX21","stoichiometry":0.2},{"gene":"HIST2H2BE","stoichiometry":0.2},{"gene":"HMGA1","stoichiometry":0.2},{"gene":"POLR2F","stoichiometry":0.2},{"gene":"SNRPA","stoichiometry":0.2},{"gene":"SNRPB","stoichiometry":0.2},{"gene":"SNRPC","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/CTR9","total_profiled":1310},"omim":[{"mim_id":"610507","title":"LEO1 HOMOLOG, PAF1/RNA POLYMERASE II COMPLEX COMPONENT; LEO1","url":"https://www.omim.org/entry/610507"},{"mim_id":"610506","title":"PAF1 HOMOLOG, PAF1/RNA POLYMERASE II COMPLEX COMPONENT; PAF1","url":"https://www.omim.org/entry/610506"},{"mim_id":"609366","title":"CTR9 HOMOLOG, PAF1/RNA POLYMERASE II COMPLEX COMPONENT; CTR9","url":"https://www.omim.org/entry/609366"},{"mim_id":"607393","title":"CELL DIVISION CYCLE 73; CDC73","url":"https://www.omim.org/entry/607393"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Nucleoplasm","reliability":"Enhanced"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/CTR9"},"hgnc":{"alias_symbol":["KIAA0155","TSBP","p150TSP"],"prev_symbol":["SH2BP1"]},"alphafold":{"accession":"Q6PD62","domains":[{"cath_id":"1.25.40.10","chopping":"198-264","consensus_level":"medium","plddt":91.1775,"start":198,"end":264},{"cath_id":"1.25.40.10","chopping":"267-373","consensus_level":"medium","plddt":91.436,"start":267,"end":373},{"cath_id":"1.20.5","chopping":"777-865","consensus_level":"high","plddt":87.1752,"start":777,"end":865}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6PD62","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q6PD62-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q6PD62-F1-predicted_aligned_error_v6.png","plddt_mean":76.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CTR9","jax_strain_url":"https://www.jax.org/strain/search?query=CTR9"},"sequence":{"accession":"Q6PD62","fasta_url":"https://rest.uniprot.org/uniprotkb/Q6PD62.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q6PD62/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6PD62"}},"corpus_meta":[{"pmid":"11884586","id":"PMC_11884586","title":"Ctr9, Rtf1, and Leo1 are components of the Paf1/RNA polymerase II complex.","date":"2002","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/11884586","citation_count":206,"is_preprint":false},{"pmid":"25099282","id":"PMC_25099282","title":"Germline mutations in the PAF1 complex gene CTR9 predispose to Wilms tumour.","date":"2014","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/25099282","citation_count":76,"is_preprint":false},{"pmid":"30228257","id":"PMC_30228257","title":"Paf1 and Ctr9 subcomplex formation is essential for Paf1 complex assembly and functional regulation.","date":"2018","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/30228257","citation_count":38,"is_preprint":false},{"pmid":"24036311","id":"PMC_24036311","title":"CTR9/PAF1c regulates molecular lineage identity, histone H3K36 trimethylation and genomic imprinting during preimplantation development.","date":"2013","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/24036311","citation_count":34,"is_preprint":false},{"pmid":"26494790","id":"PMC_26494790","title":"Ctr9, a key subunit of PAFc, affects global estrogen signaling and drives ERα-positive breast tumorigenesis.","date":"2015","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/26494790","citation_count":29,"is_preprint":false},{"pmid":"27520958","id":"PMC_27520958","title":"Ctr9, a Key Component of the Paf1 Complex, Affects Proliferation and Terminal Differentiation in the Developing Drosophila Nervous System.","date":"2016","source":"G3 (Bethesda, Md.)","url":"https://pubmed.ncbi.nlm.nih.gov/27520958","citation_count":25,"is_preprint":false},{"pmid":"8636124","id":"PMC_8636124","title":"p150TSP, a conserved nuclear phosphoprotein that contains multiple tetratricopeptide repeats and binds specifically to SH2 domains.","date":"1996","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/8636124","citation_count":20,"is_preprint":false},{"pmid":"29145644","id":"PMC_29145644","title":"Paf1 and Ctr9, core components of the PAF1 complex, maintain low levels of telomeric repeat containing RNA.","date":"2018","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/29145644","citation_count":18,"is_preprint":false},{"pmid":"36383652","id":"PMC_36383652","title":"CTR9 drives osteochondral lineage differentiation of human mesenchymal stem cells via epigenetic regulation of BMP-2 signaling.","date":"2022","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/36383652","citation_count":16,"is_preprint":false},{"pmid":"29292210","id":"PMC_29292210","title":"Identification of a novel CTR9 germline mutation in a family with Wilms tumor.","date":"2017","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/29292210","citation_count":15,"is_preprint":false},{"pmid":"27678520","id":"PMC_27678520","title":"Drosophila CG2469 Encodes a Homolog of Human CTR9 and Is Essential for Development.","date":"2016","source":"G3 (Bethesda, Md.)","url":"https://pubmed.ncbi.nlm.nih.gov/27678520","citation_count":14,"is_preprint":false},{"pmid":"34876700","id":"PMC_34876700","title":"Transcriptional regulator CTR9 promotes hepatocellular carcinoma progression and metastasis via increasing PEG10 transcriptional activity.","date":"2021","source":"Acta pharmacologica Sinica","url":"https://pubmed.ncbi.nlm.nih.gov/34876700","citation_count":12,"is_preprint":false},{"pmid":"35137163","id":"PMC_35137163","title":"The transcriptional elongation factor CTR9 demarcates PRC2-mediated H3K27me3 domains by altering PRC2 subtype equilibrium.","date":"2022","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/35137163","citation_count":12,"is_preprint":false},{"pmid":"26048990","id":"PMC_26048990","title":"Ctr9, a Protein in the Transcription Complex Paf1, Regulates Dopamine Transporter Activity at the Plasma Membrane.","date":"2015","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26048990","citation_count":11,"is_preprint":false},{"pmid":"24420920","id":"PMC_24420920","title":"Transcriptional regulator CTR9 inhibits Th17 differentiation via repression of IL-17 expression.","date":"2014","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/24420920","citation_count":10,"is_preprint":false},{"pmid":"35016493","id":"PMC_35016493","title":"MicroRNA-17-3p is upregulated in psoriasis and regulates keratinocyte hyperproliferation and pro-inflammatory cytokine secretion by targeting <em>CTR9</em>.","date":"2022","source":"European journal of histochemistry : EJH","url":"https://pubmed.ncbi.nlm.nih.gov/35016493","citation_count":10,"is_preprint":false},{"pmid":"23593388","id":"PMC_23593388","title":"CTR9, a component of PAF complex, controls elongation block at the c-Fos locus via signal-dependent regulation of chromatin-bound NELF dissociation.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23593388","citation_count":9,"is_preprint":false},{"pmid":"34369006","id":"PMC_34369006","title":"CTR9-mediated JAK2/STAT3 pathway promotes the proliferation, migration, and invasion of human glioma cells.","date":"2021","source":"Journal of clinical laboratory analysis","url":"https://pubmed.ncbi.nlm.nih.gov/34369006","citation_count":8,"is_preprint":false},{"pmid":"27829357","id":"PMC_27829357","title":"Systematic identification of Ctr9 regulome in ERα-positive breast cancer.","date":"2016","source":"BMC genomics","url":"https://pubmed.ncbi.nlm.nih.gov/27829357","citation_count":8,"is_preprint":false},{"pmid":"37038329","id":"PMC_37038329","title":"SIAH1/CTR9 axis promotes the epithelial-mesenchymal transition of hepatocellular carcinoma.","date":"2023","source":"Carcinogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/37038329","citation_count":7,"is_preprint":false},{"pmid":"35499524","id":"PMC_35499524","title":"Heterozygous variants in CTR9, which encodes a major component of the PAF1 complex, are associated with a neurodevelopmental disorder.","date":"2022","source":"Genetics in medicine : official journal of the American College of Medical Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/35499524","citation_count":7,"is_preprint":false},{"pmid":"22446411","id":"PMC_22446411","title":"Proteome analysis of a CTR9 deficient yeast strain suggests that Ctr9 has function(s) independent of the Paf1 complex.","date":"2012","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/22446411","citation_count":4,"is_preprint":false},{"pmid":"40763999","id":"PMC_40763999","title":"Paralog-Dependent Specialization of Paf1C Subunit, Ctr9, for Sex Chromosome Gene Regulation and Male Germline Differentiation in Drosophila.","date":"2025","source":"Genes to cells : devoted to molecular & cellular mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/40763999","citation_count":3,"is_preprint":false},{"pmid":"39316797","id":"PMC_39316797","title":"Ctr9 promotes virulence of Candida albicans by regulating methionine metabolism.","date":"2024","source":"Virulence","url":"https://pubmed.ncbi.nlm.nih.gov/39316797","citation_count":2,"is_preprint":false},{"pmid":"35717577","id":"PMC_35717577","title":"De novo non-synonymous CTR9 variants are associated with motor delay and macrocephaly: human genetic and zebrafish experimental evidence.","date":"2022","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/35717577","citation_count":1,"is_preprint":false},{"pmid":"39293508","id":"PMC_39293508","title":"Novel CTR9 germline pathogenic splice site variant in siblings with Wilms tumor from Tanzania.","date":"2024","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/39293508","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":14163,"output_tokens":4945,"usd":0.058332,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13191,"output_tokens":3884,"usd":0.081528,"stage2_stop_reason":"end_turn"},"total_usd":0.13986,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2002,\n      \"finding\": \"Ctr9 is a component of the Paf1/RNA polymerase II complex (Paf1C), distinct from the Srb-mediator form of Pol II holoenzyme. Tandem affinity purification and mass spectrometry established that Ctr9 associates with Paf1, Cdc73, Leo1, Rtf1, and Pol II. Genetic epistasis showed deletion of PAF1 or CTR9 produces similar severe pleiotropic phenotypes that are not additive when combined, placing them in the same pathway.\",\n      \"method\": \"Tandem affinity purification, mass spectrometry, genetic epistasis (double-deletion analysis)\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — biochemical purification with MS identification plus genetic epistasis, foundational paper replicated across many subsequent studies\",\n      \"pmids\": [\"11884586\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"CTR9/p150TSP is a nuclear phosphoprotein containing multiple tetratricopeptide repeat (TPR) domains that binds specifically to SH2 domains. The TPR module mediates homotypic protein-protein interactions in transfected cells. The C-terminal serine/glutamic acid-rich region is essential for SH2 binding, which depends on serine/threonine phosphorylation but not tyrosine phosphorylation.\",\n      \"method\": \"Biochemical purification from B cell lysates, cDNA cloning, transfection with deletion mutants, phosphorylation-dependent binding assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding assays with deletion mutagenesis in a single study; foundational characterization of domain architecture\",\n      \"pmids\": [\"8636124\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Crystal structures of both human and yeast Ctr9/Paf1 subcomplexes reveal that they assemble into heterodimers with similar conformations via an interface between the TPR module of Ctr9 and Paf1. Formation of the Ctr9/Paf1 heterodimer is required for assembly of the full yeast Paf1C and for yeast viability. Disruption of this interface greatly reduces histone H3 methylation in vivo.\",\n      \"method\": \"Crystal structure determination (X-ray crystallography), interface mutagenesis, yeast viability assay, histone modification analysis in vivo\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures of both human and yeast subcomplexes plus mutagenesis and in vivo functional validation in a single rigorous study\",\n      \"pmids\": [\"30228257\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CTR9 (as part of PAFc) constitutively associates with the 5'-coding region of the c-Fos locus and controls the elongation block by regulating NELF and SPT5 chromatin association. CTR9 depletion increases serine 5- and serine 2-phosphorylated Pol II at the unstimulated c-Fos locus, increases CDK9 association, reduces NELF binding, and enhances SPT5 recruitment. IL-6-induced JAK2 kinase activity controls CTR9 chromatin dissociation at this locus.\",\n      \"method\": \"ChIP assay, siRNA knockdown, kinase inhibitor (AG-490) treatment, analysis of Pol II phosphorylation states\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP with multiple targets and pharmacological inhibition in a single lab study\",\n      \"pmids\": [\"23593388\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Ctr9 knockdown in mouse preimplantation embryos causes loss of histone H3K36me3, failure to correctly specify ICM/TE lineages at the blastocyst stage, and aberrant expression of imprinted genes without altering allele-specific DNA methylation. These phenotypes are similar to those produced by knockdown of Setd2 (the H3K36me3 writer) or Rtf1.\",\n      \"method\": \"siRNA knockdown in mouse embryos, immunofluorescence for H3K36me3, allele-specific expression analysis, genetic epistasis with Setd2 and Rtf1 knockdown\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined epigenetic and developmental phenotypes, epistasis with Setd2, single lab\",\n      \"pmids\": [\"24036311\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Ctr9 enhances ERα protein stability, promotes recruitment of ERα and RNAPII to estrogen-regulated loci, and stimulates transcription elongation and transcription-coupled histone modifications in ERα+ breast cancer cells. Knockdown of Ctr9 (but not other PAFc subunits) nearly completely erases estrogen-regulated transcriptional response and alters cell morphology, proliferative capacity, and tamoxifen sensitivity.\",\n      \"method\": \"siRNA knockdown, ChIP, co-immunoprecipitation, ERα stability assay, transcriptome analysis, cell proliferation and morphology assays\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (ChIP, IP, protein stability, transcriptome) in a single lab; subunit-specificity established by parallel knockdown of other PAFc members\",\n      \"pmids\": [\"26494790\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Loss of Ctr9 in the Drosophila nervous system (null mutant) reduces global H3K4me3 levels, increases neuroblast numbers and nervous system proliferation, and downregulates neuropeptide genes; it also upregulates E2f1 and alters Notch pathway target gene expression. A human CTR9 cDNA transgene rescues lethality of the Drosophila Ctr9 null mutant, demonstrating functional conservation.\",\n      \"method\": \"Drosophila null mutation, human cDNA rescue transgene, immunostaining for H3K4me3, genome-wide transcriptome analysis, clonal analysis\",\n      \"journal\": \"G3 (Bethesda, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — null mutant with defined epigenetic phenotype, cross-species rescue, multiple orthogonal readouts, single lab\",\n      \"pmids\": [\"27520958\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Drosophila CG2469 encodes a functional Ctr9 homolog; both human and Drosophila Ctr9 localize to nuclei and are enriched in histone locus bodies. Null mutation of Drosophila Ctr9 causes lethality and reduces global H3K4me3 in ovary clones. A human CTR9 cDNA transgene rescues the lethality, confirming functional conservation.\",\n      \"method\": \"Sequence analysis, nuclear localization by immunofluorescence, null mutation analysis, H3K4me3 immunostaining in clones, human cDNA rescue\",\n      \"journal\": \"G3 (Bethesda, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — null mutant with histone modification readout plus cross-species rescue; single lab\",\n      \"pmids\": [\"27678520\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Ctr9 physically interacts with the dopamine transporter (DAT) via residues YKF in the first half of the DAT C-terminus, as demonstrated by yeast two-hybrid, GST pulldown, and co-immunoprecipitation. In mammalian cells, Ctr9 partially colocalizes with DAT at the plasma membrane and dramatically enhances DAT-mediated dopamine uptake by increasing the number of DAT transporters at the plasma membrane. Deletion mutagenesis demonstrated that the SH2 domain of Ctr9 is required for its nuclear localization.\",\n      \"method\": \"Yeast two-hybrid, GST pulldown, co-immunoprecipitation, co-localization imaging, dopamine uptake assay, deletion mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal binding assays (YTH, pulldown, Co-IP) plus functional uptake assay and mutagenesis; single lab\",\n      \"pmids\": [\"26048990\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CTR9 occupies the coding region of the Il17a gene in naive T cells and dissociates under Th17-polarizing conditions; its depletion induces IL-17 expression and enhances Th17 differentiation. IL-6 directly represses CTR9 promoter activity, creating a feed-forward loop. Lentiviral CTR9 overexpression in joints of collagen-induced arthritis mice reduced arthritis severity and CD4+IL-17+ T cell frequency.\",\n      \"method\": \"ChIP assay, siRNA knockdown, promoter reporter assay, lentiviral overexpression in vivo (mouse arthritis model), flow cytometry\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP, KD, promoter assay, and in vivo overexpression with defined phenotypic readouts; single lab\",\n      \"pmids\": [\"24420920\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In yeast, Paf1 and Ctr9 (core PAF1C subunits) specifically maintain low levels of telomere repeat-containing RNA (TERRA), while Cdc73, Leo1, and Rtf1 have lesser effects. Double-mutant analysis showed Paf1 and Ctr9 can regulate TERRA independently of Sir4, Rat1, and Trf4 (previously known TERRA regulators), and the data suggest they do so by affecting both transcription and degradation of TERRA.\",\n      \"method\": \"Northern blot/TERRA quantification in deletion mutants, genetic epistasis (double mutants with sir4Δ, rat1Δ, trf4Δ)\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis analysis in multiple double mutants with direct TERRA measurement; single lab\",\n      \"pmids\": [\"29145644\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CTR9 controls genome-wide H3K27me3 levels by regulating PRC2 subtype equilibrium. Loss of CTR9 leads to global expansion of H3K27me3, increased PRC2 chromatin recruitment, and a switch from the less active PRC2.2 to the more active PRC2.1 subtype. These effects are reversed by CTR9 restoration, and CTR9 depletion renders breast cancer cells hypersensitive to PRC2 inhibitors.\",\n      \"method\": \"Inducible and stable CTR9 knockdown, quantitative histone modification profiling, ChIP-seq for H3K27me3 and PRC2 subunits, PRC2 subtype biochemical analysis, cell viability assays with PRC2 inhibitors\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (ChIP-seq, quantitative histone profiling, inhibitor sensitivity) with rescue experiment; single lab\",\n      \"pmids\": [\"35137163\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CTR9 counteracts EZH2-mediated H3K27me3 deposition in human mesenchymal stem cells. CTR9 knockdown causes gain of H3K27me3 and blocks osteoblast/chondrocyte differentiation; this block is partially rescued by EZH2 inhibitors. CTR9 regulates BMP-2 secretion and membrane anchorage, and the BMP-SMAD pathway is impaired by CTR9 knockdown but rescued by BMP-2 supplementation.\",\n      \"method\": \"siRNA knockdown, EZH2 inhibitor rescue, ChIP for H3K27me3, BMP-2 supplementation rescue, in vivo ectopic osteogenesis assay, transcriptome analysis\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple rescue experiments (EZH2 inhibitor, BMP-2 supplementation) plus in vivo osteogenesis and epigenetic profiling; single lab\",\n      \"pmids\": [\"36383652\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CTR9 promotes transcription of the oncogene PEG10 via its promoter region in hepatocellular carcinoma cells. CTR9 knockdown reduces PEG10 expression, increases p21 and p27, and decreases MMP2/MMP9, while overexpression has the opposite effects. These oncogenic roles were confirmed in a xenograft mouse model.\",\n      \"method\": \"siRNA knockdown, CTR9 overexpression, promoter reporter assay, western blot, xenograft mouse model\",\n      \"journal\": \"Acta pharmacologica Sinica\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — functional KD/OE with downstream target identification, but mechanistic link to CTR9 direct transcriptional activity at PEG10 promoter is only partially resolved\",\n      \"pmids\": [\"34876700\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"SIAH1 physically interacts with CTR9 (identified by yeast two-hybrid and confirmed by co-immunoprecipitation) and ubiquitinates CTR9 via K48-linked polyubiquitination, leading to proteasomal degradation of CTR9 in HCC cells. SIAH1 inhibits EMT of HCC cells through negative regulation of CTR9 protein levels.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, ubiquitination assay (K48-linkage specificity), proteasome inhibitor assay, EMT functional assays\",\n      \"journal\": \"Carcinogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal interaction assays plus ubiquitination linkage specificity and proteasome pathway confirmation; single lab\",\n      \"pmids\": [\"37038329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Genome-wide ChIP-seq demonstrated that Ctr9 knockdown dramatically decreases global chromatin occupancy of ERα and RNAPII in response to estrogen in ERα+ breast cancer cells, establishing that Ctr9 controls ERα-target gene expression by regulating global ERα and RNAPII chromatin binding, independently of other PAFc subunits.\",\n      \"method\": \"ChIP-seq for ERα and RNAPII, inducible Ctr9 knockdown, parallel knockdown of other PAFc subunits\",\n      \"journal\": \"BMC genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide ChIP-seq with subunit-specificity controls; single lab extending prior findings\",\n      \"pmids\": [\"27829357\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"De novo CTR9 missense variants (p.Glu15Asp, p.Pro25Arg) associated with neurodevelopmental disorder show stronger affinity to PAF1 protein in pull-down assays compared to wild-type CTR9. In zebrafish, ctr9 knockout causes motor defects and telencephalon enlargement; introduction of human CTR9 mutants failed to rescue these phenotypes, and mutant mRNA overexpression caused telencephalon enlargement, indicating dominant-negative activity.\",\n      \"method\": \"Pull-down assay (mutant vs wild-type binding to PAF1), zebrafish ctr9 knockout, human CTR9 mRNA rescue experiment, overexpression of mutant mRNA in zebrafish\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro binding assay combined with zebrafish KO rescue experiment and dominant-negative overexpression; single lab, two orthogonal model systems\",\n      \"pmids\": [\"35717577\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Proteome analysis of a ctr9Δ yeast strain by 2D gel electrophoresis revealed proteome changes not fully explained by Paf1C functions, and Ctr9 has been described as a triple-helical DNA binding protein, suggesting functions independent of the Paf1 complex.\",\n      \"method\": \"2D gel electrophoresis proteomics of ctr9Δ yeast strain\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — proteomics screen suggesting independent function but without direct mechanistic validation of the specific pathway\",\n      \"pmids\": [\"22446411\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CTR9 is the scaffold/core subunit of the evolutionarily conserved PAF1 complex (PAF1C), where it forms a structurally defined heterodimer with PAF1 via its TPR domain that is essential for full complex assembly; within PAF1C, CTR9 associates with RNA Polymerase II and promotes transcription elongation, couples active transcription to histone modifications (H3K4me3, H3K36me3), restrains repressive H3K27me3 by limiting PRC2.1 activity, regulates NELF/SPT5 occupancy at specific loci to control elongation pausing, and can also localize outside the nucleus to regulate dopamine transporter trafficking; CTR9 protein stability is controlled by SIAH1-mediated K48-linked ubiquitination and proteasomal degradation, and loss-of-function variants in CTR9 cause Wilms tumor predisposition and neurodevelopmental disorders.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CTR9 is the scaffold subunit of the evolutionarily conserved PAF1 complex (PAF1C), where it associates with Paf1, Cdc73, Leo1, Rtf1, and RNA Polymerase II to couple transcription elongation to chromatin modification [#0]. Through its tetratricopeptide-repeat (TPR) module, CTR9 forms a structurally defined heterodimer with PAF1 — an interface resolved in both human and yeast crystal structures whose disruption abolishes full PAF1C assembly, yeast viability, and histone H3 methylation in vivo [#1, #2]. Within this complex CTR9 promotes deposition of active histone marks H3K4me3 and H3K36me3, a function conserved from Drosophila to mammals such that human CTR9 cDNA rescues lethality of the Drosophila null mutant [#4, #6, #7]. CTR9 also restrains the repressive mark H3K27me3 by limiting PRC2 chromatin recruitment and shifting the PRC2 subtype equilibrium away from the more active PRC2.1, a balance whose loss sensitizes breast cancer cells to PRC2 inhibitors and blocks mesenchymal stem cell differentiation [#11, #12]. At specific loci CTR9 controls Pol II elongation by regulating NELF and SPT5 chromatin occupancy and the elongation block, with cytokine signaling (IL-6/JAK2) driving its locus dissociation [#3, #9]. Beyond transcription, CTR9 enhances ERα protein stability and global ERα/RNAPII chromatin binding to drive estrogen-regulated transcription [#5, #15], and acts at the plasma membrane to enhance dopamine transporter surface levels and uptake [#8]. CTR9 protein abundance is controlled by SIAH1-mediated K48-linked polyubiquitination and proteasomal degradation [#14], and de novo CTR9 variants that act as dominant-negative alleles cause neurodevelopmental phenotypes in zebrafish models [#16].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Before its complex membership was known, CTR9 was defined as a nuclear TPR-domain phosphoprotein, establishing the domain architecture (TPR module mediating protein-protein interactions; C-terminal SH2-binding region) that would later underlie its scaffolding role.\",\n      \"evidence\": \"Biochemical purification from B cell lysates, cDNA cloning, and phosphorylation-dependent binding assays with deletion mutants\",\n      \"pmids\": [\"8636124\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of SH2-domain binding not connected to a pathway\", \"No structural model of the TPR module at this stage\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Established CTR9 as a bona fide subunit of the Paf1/RNA Pol II complex distinct from the Srb-mediator holoenzyme, defining its core biological context.\",\n      \"evidence\": \"Tandem affinity purification, mass spectrometry, and genetic epistasis (non-additive PAF1/CTR9 double deletion) in yeast\",\n      \"pmids\": [\"11884586\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve which subunit interactions are direct\", \"Molecular function of CTR9 within the complex not separated from other subunits\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Answered how CTR9 contributes to elongation control by showing it regulates the elongation block at specific loci through NELF/SPT5 occupancy and Pol II phosphorylation, linking it to signal-responsive gene activation.\",\n      \"evidence\": \"ChIP, siRNA knockdown, and JAK2 inhibition at the c-Fos locus in mammalian cells\",\n      \"pmids\": [\"23593388\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Locus-specific; not shown to be genome-wide\", \"Direct vs indirect effect on NELF/SPT5 binding not distinguished\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Connected CTR9 to a specific active chromatin mark and developmental output by linking it to H3K36me3 deposition required for lineage specification.\",\n      \"evidence\": \"siRNA knockdown in mouse preimplantation embryos with H3K36me3 immunofluorescence and epistasis with Setd2/Rtf1\",\n      \"pmids\": [\"24036311\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of imprinted-gene misregulation without DNA methylation change unresolved\", \"Whether effect requires full PAF1C not tested\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showed CTR9 acts as a brake on Th17 differentiation by occupying the Il17a coding region, with IL-6 repressing CTR9 in a feed-forward loop, establishing an immunoregulatory role.\",\n      \"evidence\": \"ChIP, knockdown, promoter reporter, and lentiviral overexpression in a mouse arthritis model\",\n      \"pmids\": [\"24420920\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of CTR9 dissociation under Th17 polarization unclear\", \"Whether repression involves histone marks not addressed\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Revealed PAF1C-independent and complex-dependent activities: CTR9 stabilizes ERα protein and drives estrogen-regulated transcription, while a separate cytoplasmic role enhances dopamine transporter surface expression.\",\n      \"evidence\": \"ChIP, Co-IP, ERα stability and transcriptome assays in breast cancer cells; yeast two-hybrid, GST pulldown, Co-IP, and dopamine uptake assays for DAT\",\n      \"pmids\": [\"26494790\", \"26048990\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which CTR9 stabilizes ERα protein not defined\", \"How nuclear vs plasma-membrane localization is partitioned unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstrated functional conservation and a link to H3K4me3, with human CTR9 rescuing Drosophila null lethality and loss reducing global H3K4me3 and disrupting neural proliferation.\",\n      \"evidence\": \"Drosophila null mutants, human cDNA rescue, H3K4me3 immunostaining, and transcriptome/clonal analysis; genome-wide ChIP-seq of ERα/RNAPII in breast cancer\",\n      \"pmids\": [\"27520958\", \"27678520\", \"27829357\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct enzymatic link between CTR9 and the H3K4 methyltransferase not established\", \"Whether neural phenotypes are cell-autonomous unresolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Provided the structural basis for CTR9 function, showing the TPR module/PAF1 heterodimer interface is required for full complex assembly, viability, and histone methylation.\",\n      \"evidence\": \"Crystal structures of human and yeast Ctr9/Paf1 subcomplexes with interface mutagenesis and in vivo validation; TERRA quantification in yeast deletion mutants\",\n      \"pmids\": [\"30228257\", \"29145644\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of full PAF1C bound to Pol II not resolved\", \"Mechanism by which Paf1/Ctr9 specifically suppress TERRA not defined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined CTR9 as a regulator of repressive chromatin by showing it limits PRC2 recruitment and biases the PRC2 subtype equilibrium, with therapeutic and differentiation consequences.\",\n      \"evidence\": \"Inducible knockdown, H3K27me3/PRC2 ChIP-seq, PRC2-subtype biochemistry, inhibitor sensitivity, and EZH2/BMP-2 rescue with in vivo osteogenesis; pull-down and zebrafish KO/rescue for NDD variants\",\n      \"pmids\": [\"35137163\", \"36383652\", \"35717577\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism by which CTR9 antagonizes PRC2 recruitment unresolved\", \"How dominant-negative variants perturb PAF1C function in vivo not detailed\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified the post-translational control of CTR9 abundance, showing SIAH1 ubiquitinates CTR9 via K48 linkages for proteasomal degradation, coupling CTR9 levels to EMT control.\",\n      \"evidence\": \"Yeast two-hybrid, Co-IP, K48-linkage-specific ubiquitination and proteasome inhibition assays, EMT functional readouts in HCC cells\",\n      \"pmids\": [\"37038329\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Signals controlling SIAH1-mediated CTR9 turnover not defined\", \"Whether degradation targets free CTR9 or assembled PAF1C unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how CTR9's distinct activities — active-mark deposition, PRC2 antagonism, elongation pausing control, ERα stabilization, and cytoplasmic DAT regulation — are mechanistically partitioned and which require intact PAF1C versus independent CTR9 function.\",\n      \"evidence\": \"No single study in the corpus reconciles the nuclear PAF1C-dependent and complex-independent roles\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No reconstitution dissecting complex-dependent vs independent CTR9 activities\", \"Triple-helical DNA binding activity not mechanistically validated\", \"Genome-wide direct target map distinguishing CTR9-specific from PAF1C-shared functions lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [3, 5, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [1, 7, 8]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 3, 5]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [2, 4, 6, 11]}\n    ],\n    \"complexes\": [\"PAF1 complex (PAF1C)\"],\n    \"partners\": [\"PAF1\", \"CDC73\", \"LEO1\", \"RTF1\", \"RNA Pol II\", \"SIAH1\", \"SLC6A3\", \"ESR1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}