{"gene":"PCGF1","run_date":"2026-06-10T05:19:53","timeline":{"discoveries":[{"year":2013,"finding":"The RAWUL domain of PCGF1 binds selectively to the PUFD domain of BCOR (but not to PCGF2/MEL18 or PCGF4/BMI1 RAWUL domains). Crystal structure of the BCOR PUFD–PCGF1 RAWUL complex reveals that PUFD binds the same surfaces as other Polycomb RAWUL interactions, and selectivity is determined by specific residues within these interaction surfaces.","method":"X-ray crystallography, in vitro binding assays, analytical ultracentrifugation","journal":"Structure","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional validation of binding selectivity, multiple orthogonal methods in one rigorous study","pmids":["23523425"],"is_preprint":false},{"year":2016,"finding":"PCGF1 and BCORL1 form a heterodimer (via PCGF1 RAWUL and BCORL1 PUFD) that is required for KDM2B recruitment to assemble a minimal four-component PRC1.1 complex (KDM2B/SKP1/BCORL1/PCGF1). The crystal structure shows that BCORL1 PUFD positions residues preceding the PCGF1 RAWUL to create an extended interface unique to PCGF1-containing PRC1.1. BCOR PUFD internal tandem duplications found in pediatric tumors are structurally rationalized by this complex.","method":"X-ray crystallography, in vitro assembly assays, analytical ultracentrifugation","journal":"Structure","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure of tetrameric complex combined with in vitro reconstitution and domain mapping","pmids":["27568929"],"is_preprint":false},{"year":2008,"finding":"NSPc1/PCGF1 stimulates H2A ubiquitination in vivo and in vitro through direct interaction with both RING2 and H2A. NSPc1 cooperates with EZH2-mediated H3K27me3 and Dnmt1-mediated DNA methylation at the HOXA7 promoter; NSPc1 knockdown reduces H2AK119ub and leads to DNA demethylation and Dnmt1 dissociation, while EZH2 depletion abolishes NSPc1 recruitment.","method":"In vitro ubiquitination assay, co-immunoprecipitation, ChIP, siRNA knockdown, RT-PCR","journal":"Nucleic Acids Research","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro ubiquitination assay plus ChIP and knockdown, multiple orthogonal methods, single lab","pmids":["18460542"],"is_preprint":false},{"year":2018,"finding":"The FBXL10(KDM2B)–RNF68(PCGF1)–RNF2 ubiquitin ligase complex (FRRUC) is rapidly and transiently recruited to DNA damage sites in a PARP1- and TIMELESS-dependent manner. At damage sites FRRUC promotes H2AK119 mono-ubiquitylation, a local decrease of H2A levels, increased H2A.Z incorporation, transcriptional repression, DSB signaling, and homologous recombination repair. FRRUC activity is also required for subsequent proper recruitment of BMI1–RNF2 and MEL18–RNF2 complexes.","method":"Live-cell imaging, co-immunoprecipitation, laser micro-irradiation, knockdown/knockout with functional readouts (HR repair assays, DSB signaling)","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (live imaging, Co-IP, functional HR assay) with rigorous controls","pmids":["29985131"],"is_preprint":false},{"year":2021,"finding":"PCGF1-containing variant PRC1 (PCGF1-PRC1) mediates differentiation-associated transcriptional down-regulation of target genes by depositing H2AK119ub1 and recruiting PRC2. In the absence of PCGF1, both H2AK119ub1 deposition and PRC2 recruitment are disrupted, leading to aberrant expression of target genes during embryoid body differentiation.","method":"PCGF1 knockout in ESCs, ChIP-seq, RNA-seq, embryoid body differentiation assay","journal":"Nature Communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with ChIP-seq and RNA-seq defining molecular mechanism and pathway position","pmids":["34504070"],"is_preprint":false},{"year":2022,"finding":"PCGF1-PRC1 localizes at the replication fork and prevents overloading of activators and chromatin remodeling factors on nascent DNA, thereby mediating proper nucleosome deposition and correct chromatin configurations. This replication-fork function facilitates downstream PRC2-mediated repression of target genes (e.g., Hmga2) and restricts premature myeloid differentiation in hematopoietic stem and progenitor cells.","method":"PCGF1 conditional KO in HSPCs, iPOND/nascent chromatin capture, ChIP-seq, RNA-seq, differentiation assays","journal":"Nature Communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with nascent chromatin capture plus ChIP-seq establishing mechanistic link between replication fork function and PRC2 recruitment","pmids":["36443290"],"is_preprint":false},{"year":2024,"finding":"At the single-molecule level, variant PRC1 containing PCGF1 transiently samples chromatin until reaching a catalytically competent nucleosome-bound state that enables E2 recruitment and ubiquitin transfer to H2AK119. PCGF1-containing PRC1 has lower activity than PCGF4-containing PRC1 because it achieves the catalytically competent state with lower probability. Variant PRC1 shows weak processivity in ubiquitylating neighboring nucleosomes.","method":"Single-molecule fluorescence microscopy, in vitro chromatin ubiquitylation reconstitution","journal":"bioRxiv (preprint)","confidence":"High","confidence_rationale":"Tier 1 / Moderate — reconstituted in vitro with single-molecule resolution; preprint, single lab, not yet peer-reviewed","pmids":["bio_10.1101_2024.10.25.620026"],"is_preprint":true},{"year":2005,"finding":"NSPc1/PCGF1 protein localizes predominantly to the nucleus. Its transcriptional repression activity depends on the C-terminal domain and specifically on the PKC phosphorylation site at serine 183; mutation of this site impairs repression activity.","method":"Subcellular fractionation/immunofluorescence, luciferase reporter assay with deletion/point mutants, Western blot","journal":"FEBS Letters","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — direct localization experiment plus functional mutagenesis, single lab, two orthogonal methods","pmids":["15620699"],"is_preprint":false},{"year":2006,"finding":"NSPc1/PCGF1 represses p21Waf1/Cip1 transcription by binding to the −1357 to −1083 region of the p21 promoter, and this repression is dependent on the retinoic acid response element (RARE) within that region. NSPc1 competes with RA receptors for the RARE element both in vitro and in vivo.","method":"ChIP, DNA pulldown, luciferase reporter assays, RT-PCR, siRNA knockdown","journal":"Nucleic Acids Research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — ChIP and DNA pulldown with reporter assays showing RARE-dependent mechanism, single lab","pmids":["17088287"],"is_preprint":false},{"year":2013,"finding":"Nspc1/PCGF1 directly binds the −1021 to −784 region of the Oct4 promoter and activates Oct4 transcription in a RARE-dependent manner, thereby positively regulating the Oct4-Nanog-Sox2 pluripotency axis in P19 embryonal carcinoma cells.","method":"ChIP, luciferase reporter assay, dominant-negative analysis, siRNA/overexpression","journal":"Biochemical and Biophysical Research Communications","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — ChIP and reporter assay with RARE-dependent mechanism; single lab, moderate methods","pmids":["24113379"],"is_preprint":false},{"year":2017,"finding":"NSPc1/PCGF1 promotes cancer stem cell self-renewal in glioma by epigenetically repressing RDH16 through direct binding to the −1073 to −823 region of the RDH16 promoter, reducing all-trans retinoic acid (ATRA) synthesis; RDH16 restoration partially rescues the NSPc1-induced stemness enhancement.","method":"ChIP, shRNA knockdown, sphere formation assay, xenograft, RT-PCR/Western blot","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — ChIP confirming direct binding plus functional rescue, single lab","pmids":["28394339"],"is_preprint":false},{"year":2015,"finding":"Under endogenous conditions in a neuronal differentiation cell model, PCGF1 physically interacts with all previously reported members of the variant PRC1 complex (including BCOR and KDM2B) and additionally with a pluripotency sub-network including NANOG, OCT4, PATZ1, and DPPA4. PCGF1 knockdown reduces DPPA4 expression at both mRNA and protein levels.","method":"Affinity purification–mass spectrometry (AP-MS) under endogenous conditions, siRNA knockdown, Western blot","journal":"Scientific Reports","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — AP-MS with two rounds of interaction mapping plus functional knockdown, single lab","pmids":["26687479"],"is_preprint":false},{"year":2017,"finding":"Pcgf1 loss-of-function in mouse ES cells (CRISPR/Cas9 KO) severely impairs in vitro differentiation while self-renewal is maintained. ChIP shows that Pcgf1 deletion reduces Ring1B and H2AK119ub1 occupancy at target genes, revealing an unexpected positive role of Pcgf1 in gene activation during ES cell lineage specification.","method":"CRISPR/Cas9 knockout, RNA-seq, ChIP, differentiation assays","journal":"Scientific Reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with ChIP and RNA-seq, single lab","pmids":["28393894"],"is_preprint":false},{"year":2024,"finding":"PCGF1 facilitates deposition of H2AK119ub at MHC class I gene promoters to silence MHC-I transcription in tumor cells. The deubiquitinase BAP1 opposes this by removing H2AK119ub, and PCGF1 depletion restores MHC-I expression and T cell-mediated killing of tumor cells.","method":"Genome-wide CRISPR screen, PCGF1 KO/knockdown, ChIP, T cell cytotoxicity assays in multiple tumor lines","journal":"Journal of Immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR screen plus functional KO with ChIP and T cell killing assay, single lab","pmids":["38088808"],"is_preprint":false},{"year":2024,"finding":"PCGF1 inhibits MMP10 transcription by upregulating RING1B/H2AK119ub and EZH2/H3K27me3 marks at the MMP10 promoter in microglia, thereby suppressing NF-κB/MAPK pathway activation and neuroinflammation.","method":"ChIP, in vivo microglial PCGF1 manipulation, behavioral assays, Western blot","journal":"Molecular Psychiatry","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — ChIP demonstrating promoter occupancy and histone marks with in vivo functional readout, single lab","pmids":["39215186"],"is_preprint":false},{"year":2023,"finding":"NSPc1/PCGF1 requires DNMT3a recruitment for maintenance of DNA methylation at the HOXA11 promoter in trophoblast cells; NSPc1 is required for DNMT3a occupancy, and the NSPc1–DNMT3a cooperation represses HOXA11 and promotes trophoblast cell apoptosis.","method":"ChIP, siRNA knockdown, co-immunoprecipitation, bisulfite sequencing, apoptosis assays","journal":"Acta Biochimica et Biophysica Sinica","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — ChIP and Co-IP showing NSPc1–DNMT3a interaction with functional apoptosis readout, single lab","pmids":["36815373"],"is_preprint":false},{"year":2023,"finding":"MORC4 interacts physically with PCGF1 (by co-immunoprecipitation) and augments PCGF1's repression of CDKN1A (p21) transcription; MORC4 itself does not substantially suppress CDKN1A activity but potentiates PCGF1's effect. MORC4 is degraded via the ubiquitin-proteasome system by HECW2.","method":"Co-immunoprecipitation, luciferase reporter assay, siRNA/overexpression, Western blot","journal":"Cancer Gene Therapy","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP plus reporter assay, single lab, limited mechanistic detail","pmids":["36932196"],"is_preprint":false},{"year":2021,"finding":"Pcgf1 loss-of-function in zebrafish decreases H3K27me3 at the promoters of Ngn1 and Otx2 and decreases H3K4me3 at the promoters of Pou5f3 and Nanog, implicating Pcgf1 in maintaining specific histone methylation states during early neural tube development.","method":"Morpholino knockdown in zebrafish, ChIP, RNA-seq in P19 cells","journal":"Frontiers in Cell and Developmental Biology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — ChIP on specific promoters in knockdown cells, single lab, limited mechanistic follow-up","pmids":["33575252"],"is_preprint":false},{"year":2024,"finding":"USP15 deubiquitinates and stabilizes TFAP4, which transcriptionally activates PCGF1; the USP15–TFAP4–PCGF1 axis promotes EMT, invasion, and stemness in colorectal cancer cells.","method":"Co-immunoprecipitation, dual luciferase reporter assay, oligonucleotide pulldown, ChIP, siRNA knockdown","journal":"Biochemical Pharmacology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — multiple assays but primarily showing upstream regulation of PCGF1 expression; PCGF1's own mechanism not further resolved, single lab","pmids":["38801926"],"is_preprint":false}],"current_model":"PCGF1 is a core subunit of variant Polycomb Repressive Complex 1 (PRC1.1) whose RAWUL domain selectively binds the PUFD domains of BCOR/BCORL1 to recruit KDM2B/SKP1, forming a minimal complex that mono-ubiquitylates H2AK119 on chromatin; this activity—shown at single-molecule resolution to depend on transient sampling until a catalytically competent nucleosome-bound state is achieved—silences developmental genes by promoting PRC2 recruitment and H3K27me3 deposition, while at DNA damage sites the FBXL10–PCGF1–RNF2 complex is recruited in a PARP1/TIMELESS-dependent manner to drive H2AK119ub1, H2A.Z incorporation, and homologous recombination repair."},"narrative":{"mechanistic_narrative":"PCGF1 (NSPc1) is a core subunit of variant Polycomb Repressive Complex 1 (PRC1.1) that targets H2AK119 mono-ubiquitylation to developmental and lineage-control genes, coupling Polycomb repression to PRC2 recruitment and chromatin silencing [PMID:34504070]. Its RAWUL domain selectively engages the PUFD domain of BCOR/BCORL1 — but not the RAWUL domains of PCGF2/MEL18 or PCGF4/BMI1 — and this interface assembles a minimal four-component KDM2B/SKP1/BCORL1/PCGF1 complex, the structural basis for PCGF1-specific PRC1.1 assembly [PMID:23523425, PMID:27568929]. PCGF1 directly contacts both RING2/RING1B and H2A to stimulate H2AK119 ubiquitylation [PMID:18460542], and at the single-molecule level the PCGF1 complex transiently samples chromatin until reaching a catalytically competent nucleosome-bound state, with intrinsically lower activity and weaker processivity than PCGF4-containing PRC1 [PMID:bio_10.1101_2024.10.25.620026]. Functionally, PCGF1-deposited H2AK119ub1 recruits PRC2 and licenses H3K27me3 to drive differentiation-associated gene down-regulation in ESCs [PMID:34504070], and at replication forks the complex governs nucleosome deposition to restrain premature myeloid differentiation in hematopoietic stem/progenitor cells [PMID:36443290]. Beyond canonical silencing, the FBXL10(KDM2B)–PCGF1–RNF2 ligase complex is transiently recruited to DNA damage sites in a PARP1/TIMELESS-dependent manner to drive H2AK119ub1, H2A.Z incorporation, and homologous recombination repair [PMID:29985131]. PCGF1 additionally silences specific promoters including MHC class I genes — opposed by the deubiquitinase BAP1 — to limit T cell-mediated tumor killing [PMID:38088808], and at several gene-specific targets (HOXA7, CDKN1A/p21) it cooperates with EZH2, Dnmt1, and DNMT3a to integrate H2AK119ub with H3K27me3 and DNA methylation [PMID:18460542, PMID:17088287].","teleology":[{"year":2005,"claim":"Established PCGF1/NSPc1 as a nuclear transcriptional repressor and identified a regulatory phosphorylation site, providing the first functional handle on the protein before its Polycomb role was defined.","evidence":"Subcellular fractionation/immunofluorescence and luciferase reporter assays with deletion/point mutants","pmids":["15620699"],"confidence":"Medium","gaps":["Repression mechanism not linked to chromatin modification at this stage","PKC-dependent regulation of S183 not tested in vivo","No target genes identified"]},{"year":2008,"claim":"Connected PCGF1 to histone modification by showing it stimulates H2A ubiquitylation via direct RING2 and H2A contacts and cooperates with EZH2/Dnmt1 silencing, placing it within a Polycomb-DNA methylation axis.","evidence":"In vitro ubiquitination assay, Co-IP, ChIP and siRNA knockdown at the HOXA7 promoter","pmids":["18460542"],"confidence":"High","gaps":["Did not define the full PRC1.1 complex composition","Direction of EZH2/PCGF1 recruitment hierarchy only partially resolved","Genome-wide targets unknown"]},{"year":2013,"claim":"Resolved the structural and selectivity basis for PCGF1 recruitment, showing the PCGF1 RAWUL domain binds BCOR PUFD selectively over other PCGF paralogs.","evidence":"X-ray crystallography of the BCOR PUFD–PCGF1 RAWUL complex with in vitro binding and analytical ultracentrifugation","pmids":["23523425"],"confidence":"High","gaps":["Did not show catalytic consequences of the interaction","Full PRC1.1 assembly not reconstituted in this study"]},{"year":2016,"claim":"Defined the minimal PRC1.1 assembly by showing PCGF1–BCORL1 heterodimerization is required to recruit KDM2B and build a four-component complex, and rationalized tumor-associated BCOR duplications structurally.","evidence":"Crystal structure of the tetrameric KDM2B/SKP1/BCORL1/PCGF1 complex with in vitro reconstitution and domain mapping","pmids":["27568929"],"confidence":"High","gaps":["Catalytic activity of the reconstituted complex on nucleosomes not measured here","In vivo requirement of the extended interface not tested"]},{"year":2017,"claim":"Revealed a context-dependent and even positive role for PCGF1 in gene regulation during differentiation, complicating a purely repressive model.","evidence":"CRISPR/Cas9 KO in mouse ES cells with RNA-seq, ChIP and differentiation assays","pmids":["28393894"],"confidence":"Medium","gaps":["Mechanism of positive gene activation not resolved","Single lab","Distinction between direct and indirect targets unclear"]},{"year":2018,"claim":"Extended PCGF1 function beyond transcription to genome maintenance, identifying the FBXL10–PCGF1–RNF2 ligase as a PARP1/TIMELESS-dependent responder at DNA damage sites driving HR repair.","evidence":"Live-cell imaging, laser micro-irradiation, Co-IP and HR/DSB functional assays","pmids":["29985131"],"confidence":"High","gaps":["Direct PARP1/TIMELESS-PCGF1 recruitment interface not defined","Substrate range beyond H2AK119 at damage sites unclear"]},{"year":2021,"claim":"Defined the pathway position of PCGF1-PRC1 in development, showing its H2AK119ub1 deposition is required for PRC2 recruitment and H3K27me3 during differentiation.","evidence":"PCGF1 KO in ESCs with ChIP-seq, RNA-seq and embryoid body differentiation","pmids":["34504070"],"confidence":"High","gaps":["Mechanism by which H2AK119ub1 recruits PRC2 not directly demonstrated here","Target gene selectivity determinants unresolved"]},{"year":2022,"claim":"Identified an unexpected replication-fork function in which PCGF1-PRC1 controls nucleosome deposition on nascent DNA to enable downstream PRC2 repression and restrain premature myeloid differentiation.","evidence":"Conditional KO in HSPCs with iPOND/nascent chromatin capture, ChIP-seq and RNA-seq","pmids":["36443290"],"confidence":"High","gaps":["How PCGF1 is recruited to forks is unknown","Relationship between fork function and canonical H2AK119ub deposition not fully separated"]},{"year":2024,"claim":"Resolved the catalytic mechanism at single-molecule level, showing PCGF1-PRC1 transiently samples chromatin to reach a competent state and is intrinsically less active and less processive than PCGF4-PRC1.","evidence":"Single-molecule fluorescence microscopy with reconstituted in vitro chromatin ubiquitylation (preprint)","pmids":["bio_10.1101_2024.10.25.620026"],"confidence":"High","gaps":["Preprint, single lab, not yet peer-reviewed","Cellular determinants modulating sampling kinetics unknown"]},{"year":2024,"claim":"Extended PCGF1-mediated silencing to immune evasion and inflammation, showing it represses MHC-I (opposed by BAP1) and MMP10 to limit T cell killing and neuroinflammation.","evidence":"Genome-wide CRISPR screen, KO/knockdown, ChIP, T cell cytotoxicity and in vivo microglial assays","pmids":["38088808","39215186"],"confidence":"Medium","gaps":["Whether MHC-I and MMP10 silencing reflect canonical PRC1.1 targeting not fully established","BAP1-PCGF1 antagonism mechanism at specific loci not structurally defined"]},{"year":null,"claim":"How PCGF1 target selectivity, replication-fork recruitment, and damage-site recruitment are coordinated across its repressive, developmental, and DNA-repair functions remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking PCGF1 recruitment cues across chromatin contexts","Determinants of locus-specific recruitment beyond BCOR/BCORL1 binding unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[2,3,6]},{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[2,3]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[4,8,13]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[8,9,10]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[7]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[2,4]}],"pathway":[{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[2,4,5]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[4,8,13]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[3]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[4,5,12]}],"complexes":["variant PRC1.1 (KDM2B/SKP1/BCOR-BCORL1/PCGF1)","FBXL10(KDM2B)-PCGF1(RNF68)-RNF2 (FRRUC)"],"partners":["BCOR","BCORL1","KDM2B","RNF2","RING1B","EZH2","DNMT3A","MORC4"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9BSM1","full_name":"Polycomb group RING finger protein 1","aliases":["Nervous system Polycomb-1","NSPc1","RING finger protein 68"],"length_aa":259,"mass_kda":30.3,"function":"Component of the Polycomb group (PcG) multiprotein BCOR complex, a complex required to maintain the transcriptionally repressive state of some genes, such as BCL6 and the cyclin-dependent kinase inhibitor, CDKN1A. Transcriptional repressor that may be targeted to the DNA by BCL6; this transcription repressor activity may be related to PKC signaling pathway. Represses CDKN1A expression by binding to its promoter, and this repression is dependent on the retinoic acid response element (RARE element). Promotes cell cycle progression and enhances cell proliferation as well. May have a positive role in tumor cell growth by down-regulating CDKN1A. Component of a Polycomb group (PcG) multiprotein PRC1-like complex, a complex class required to maintain the transcriptionally repressive state of many genes, including Hox genes, throughout development. PcG PRC1 complex acts via chromatin remodeling and modification of histones; it mediates monoubiquitination of histone H2A 'Lys-119', rendering chromatin heritably changed in its expressibility (PubMed:26151332). Within the PRC1-like complex, regulates RNF2 ubiquitin ligase activity (PubMed:26151332). Regulates the expression of DPPA4 and NANOG in the NT2 embryonic carcinoma cells (PubMed:26687479)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q9BSM1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PCGF1","classification":"Not Classified","n_dependent_lines":44,"n_total_lines":1208,"dependency_fraction":0.03642384105960265},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"HIST2H2BE","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/PCGF1","total_profiled":1310},"omim":[{"mim_id":"617543","title":"POLYCOMB GROUP RING FINGER PROTEIN 3; PCGF3","url":"https://www.omim.org/entry/617543"},{"mim_id":"617407","title":"POLYCOMB GROUP RING FINGER PROTEIN 5; PCGF5","url":"https://www.omim.org/entry/617407"},{"mim_id":"610231","title":"POLYCOMB GROUP RING FINGER PROTEIN 1; PCGF1","url":"https://www.omim.org/entry/610231"},{"mim_id":"604479","title":"SIRTUIN 1; SIRT1","url":"https://www.omim.org/entry/604479"},{"mim_id":"300688","title":"BCL6 COREPRESSOR-LIKE 1; BCORL1","url":"https://www.omim.org/entry/300688"}],"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/PCGF1"},"hgnc":{"alias_symbol":["NSPC1","RNF68","MGC10882"],"prev_symbol":[]},"alphafold":{"accession":"Q9BSM1","domains":[{"cath_id":"3.30.40.10","chopping":"37-110","consensus_level":"high","plddt":95.1865,"start":37,"end":110},{"cath_id":"3.10.20.90","chopping":"162-178_185-253","consensus_level":"high","plddt":90.7533,"start":162,"end":253}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BSM1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BSM1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BSM1-F1-predicted_aligned_error_v6.png","plddt_mean":81.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PCGF1","jax_strain_url":"https://www.jax.org/strain/search?query=PCGF1"},"sequence":{"accession":"Q9BSM1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9BSM1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9BSM1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BSM1"}},"corpus_meta":[{"pmid":"23523425","id":"PMC_23523425","title":"Structure of the polycomb group protein PCGF1 in complex with BCOR reveals basis for binding selectivity of PCGF homologs.","date":"2013","source":"Structure (London, England : 1993)","url":"https://pubmed.ncbi.nlm.nih.gov/23523425","citation_count":87,"is_preprint":false},{"pmid":"18460542","id":"PMC_18460542","title":"Cooperation between EZH2, NSPc1-mediated histone H2A ubiquitination and Dnmt1 in HOX gene silencing.","date":"2008","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/18460542","citation_count":82,"is_preprint":false},{"pmid":"27568929","id":"PMC_27568929","title":"KDM2B Recruitment of the Polycomb Group Complex, PRC1.1, Requires Cooperation between PCGF1 and BCORL1.","date":"2016","source":"Structure (London, England : 1993)","url":"https://pubmed.ncbi.nlm.nih.gov/27568929","citation_count":50,"is_preprint":false},{"pmid":"29985131","id":"PMC_29985131","title":"PARP1-dependent recruitment of the FBXL10-RNF68-RNF2 ubiquitin ligase to sites of DNA damage controls H2A.Z loading.","date":"2018","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/29985131","citation_count":46,"is_preprint":false},{"pmid":"26687479","id":"PMC_26687479","title":"The variant Polycomb Repressor Complex 1 component PCGF1 interacts with a pluripotency sub-network that includes DPPA4, a regulator of embryogenesis.","date":"2015","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/26687479","citation_count":46,"is_preprint":false},{"pmid":"28394339","id":"PMC_28394339","title":"NSPc1 promotes cancer stem cell self-renewal by repressing the synthesis of all-trans retinoic acid via targeting RDH16 in malignant glioma.","date":"2017","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/28394339","citation_count":42,"is_preprint":false},{"pmid":"17088287","id":"PMC_17088287","title":"NSPc1 is a cell growth regulator that acts as a transcriptional repressor of p21Waf1/Cip1 via the RARE element.","date":"2006","source":"Nucleic acids 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one","url":"https://pubmed.ncbi.nlm.nih.gov/27442247","citation_count":22,"is_preprint":false},{"pmid":"39215186","id":"PMC_39215186","title":"Microglial PCGF1 alleviates neuroinflammation associated depressive behavior in adolescent mice.","date":"2024","source":"Molecular psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/39215186","citation_count":21,"is_preprint":false},{"pmid":"24113379","id":"PMC_24113379","title":"Nspc1 regulates the key pluripotent Oct4-Nanog-Sox2 axis in P19 embryonal carcinoma cells via directly activating Oct4.","date":"2013","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/24113379","citation_count":16,"is_preprint":false},{"pmid":"36443290","id":"PMC_36443290","title":"PCGF1-PRC1 links chromatin repression with DNA replication during hematopoietic cell lineage commitment.","date":"2022","source":"Nature 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letters","url":"https://pubmed.ncbi.nlm.nih.gov/31186810","citation_count":8,"is_preprint":false},{"pmid":"36932196","id":"PMC_36932196","title":"MORC4 plays a tumor-promoting role in colorectal cancer via regulating PCGF1/CDKN1A axis in vitro and in vivo.","date":"2023","source":"Cancer gene therapy","url":"https://pubmed.ncbi.nlm.nih.gov/36932196","citation_count":7,"is_preprint":false},{"pmid":"38088808","id":"PMC_38088808","title":"Balanced Epigenetic Regulation of MHC Class I Expression in Tumor Cells by the Histone Ubiquitin Modifiers BAP1 and PCGF1.","date":"2024","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/38088808","citation_count":7,"is_preprint":false},{"pmid":"30720120","id":"PMC_30720120","title":"NSPc1 polycomb protein complex binds and cross‑talks to lncRNAs in glioma H4 cells.","date":"2019","source":"Oncology reports","url":"https://pubmed.ncbi.nlm.nih.gov/30720120","citation_count":6,"is_preprint":false},{"pmid":"37452641","id":"PMC_37452641","title":"Pcgf1 gene disruption reveals primary involvement of epigenetic mechanism in neuronal subtype specification in the enteric nervous system.","date":"2023","source":"Development, growth & differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/37452641","citation_count":4,"is_preprint":false},{"pmid":"19024384","id":"PMC_19024384","title":"[Expression pattern of polycomb gene Nspc1 at the early developmental stage in zebrafish].","date":"2008","source":"Zhongguo yi xue ke xue yuan xue bao. Acta Academiae Medicinae Sinicae","url":"https://pubmed.ncbi.nlm.nih.gov/19024384","citation_count":3,"is_preprint":false},{"pmid":"36210701","id":"PMC_36210701","title":"[PCGF1 is highly expressed in rectal adenocarcinoma and silencing PCGF1 inhibits proliferation of rectal adenocarcinoma cells in vitro].","date":"2022","source":"Nan fang yi ke da xue xue bao = Journal of Southern Medical University","url":"https://pubmed.ncbi.nlm.nih.gov/36210701","citation_count":1,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.10.25.620026","title":"Single-molecule analysis reveals the mechanism of chromatin ubiquitylation by variant PRC1 complexes","date":"2024-10-29","source":"bioRxiv","url":"https://doi.org/10.1101/2024.10.25.620026","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":15794,"output_tokens":4755,"usd":0.059353,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12810,"output_tokens":3929,"usd":0.081138,"stage2_stop_reason":"end_turn"},"total_usd":0.140491,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2013,\n      \"finding\": \"The RAWUL domain of PCGF1 binds selectively to the PUFD domain of BCOR (but not to PCGF2/MEL18 or PCGF4/BMI1 RAWUL domains). Crystal structure of the BCOR PUFD–PCGF1 RAWUL complex reveals that PUFD binds the same surfaces as other Polycomb RAWUL interactions, and selectivity is determined by specific residues within these interaction surfaces.\",\n      \"method\": \"X-ray crystallography, in vitro binding assays, analytical ultracentrifugation\",\n      \"journal\": \"Structure\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional validation of binding selectivity, multiple orthogonal methods in one rigorous study\",\n      \"pmids\": [\"23523425\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PCGF1 and BCORL1 form a heterodimer (via PCGF1 RAWUL and BCORL1 PUFD) that is required for KDM2B recruitment to assemble a minimal four-component PRC1.1 complex (KDM2B/SKP1/BCORL1/PCGF1). The crystal structure shows that BCORL1 PUFD positions residues preceding the PCGF1 RAWUL to create an extended interface unique to PCGF1-containing PRC1.1. BCOR PUFD internal tandem duplications found in pediatric tumors are structurally rationalized by this complex.\",\n      \"method\": \"X-ray crystallography, in vitro assembly assays, analytical ultracentrifugation\",\n      \"journal\": \"Structure\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure of tetrameric complex combined with in vitro reconstitution and domain mapping\",\n      \"pmids\": [\"27568929\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"NSPc1/PCGF1 stimulates H2A ubiquitination in vivo and in vitro through direct interaction with both RING2 and H2A. NSPc1 cooperates with EZH2-mediated H3K27me3 and Dnmt1-mediated DNA methylation at the HOXA7 promoter; NSPc1 knockdown reduces H2AK119ub and leads to DNA demethylation and Dnmt1 dissociation, while EZH2 depletion abolishes NSPc1 recruitment.\",\n      \"method\": \"In vitro ubiquitination assay, co-immunoprecipitation, ChIP, siRNA knockdown, RT-PCR\",\n      \"journal\": \"Nucleic Acids Research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro ubiquitination assay plus ChIP and knockdown, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"18460542\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The FBXL10(KDM2B)–RNF68(PCGF1)–RNF2 ubiquitin ligase complex (FRRUC) is rapidly and transiently recruited to DNA damage sites in a PARP1- and TIMELESS-dependent manner. At damage sites FRRUC promotes H2AK119 mono-ubiquitylation, a local decrease of H2A levels, increased H2A.Z incorporation, transcriptional repression, DSB signaling, and homologous recombination repair. FRRUC activity is also required for subsequent proper recruitment of BMI1–RNF2 and MEL18–RNF2 complexes.\",\n      \"method\": \"Live-cell imaging, co-immunoprecipitation, laser micro-irradiation, knockdown/knockout with functional readouts (HR repair assays, DSB signaling)\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (live imaging, Co-IP, functional HR assay) with rigorous controls\",\n      \"pmids\": [\"29985131\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PCGF1-containing variant PRC1 (PCGF1-PRC1) mediates differentiation-associated transcriptional down-regulation of target genes by depositing H2AK119ub1 and recruiting PRC2. In the absence of PCGF1, both H2AK119ub1 deposition and PRC2 recruitment are disrupted, leading to aberrant expression of target genes during embryoid body differentiation.\",\n      \"method\": \"PCGF1 knockout in ESCs, ChIP-seq, RNA-seq, embryoid body differentiation assay\",\n      \"journal\": \"Nature Communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with ChIP-seq and RNA-seq defining molecular mechanism and pathway position\",\n      \"pmids\": [\"34504070\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PCGF1-PRC1 localizes at the replication fork and prevents overloading of activators and chromatin remodeling factors on nascent DNA, thereby mediating proper nucleosome deposition and correct chromatin configurations. This replication-fork function facilitates downstream PRC2-mediated repression of target genes (e.g., Hmga2) and restricts premature myeloid differentiation in hematopoietic stem and progenitor cells.\",\n      \"method\": \"PCGF1 conditional KO in HSPCs, iPOND/nascent chromatin capture, ChIP-seq, RNA-seq, differentiation assays\",\n      \"journal\": \"Nature Communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with nascent chromatin capture plus ChIP-seq establishing mechanistic link between replication fork function and PRC2 recruitment\",\n      \"pmids\": [\"36443290\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"At the single-molecule level, variant PRC1 containing PCGF1 transiently samples chromatin until reaching a catalytically competent nucleosome-bound state that enables E2 recruitment and ubiquitin transfer to H2AK119. PCGF1-containing PRC1 has lower activity than PCGF4-containing PRC1 because it achieves the catalytically competent state with lower probability. Variant PRC1 shows weak processivity in ubiquitylating neighboring nucleosomes.\",\n      \"method\": \"Single-molecule fluorescence microscopy, in vitro chromatin ubiquitylation reconstitution\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — reconstituted in vitro with single-molecule resolution; preprint, single lab, not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2024.10.25.620026\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"NSPc1/PCGF1 protein localizes predominantly to the nucleus. Its transcriptional repression activity depends on the C-terminal domain and specifically on the PKC phosphorylation site at serine 183; mutation of this site impairs repression activity.\",\n      \"method\": \"Subcellular fractionation/immunofluorescence, luciferase reporter assay with deletion/point mutants, Western blot\",\n      \"journal\": \"FEBS Letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — direct localization experiment plus functional mutagenesis, single lab, two orthogonal methods\",\n      \"pmids\": [\"15620699\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"NSPc1/PCGF1 represses p21Waf1/Cip1 transcription by binding to the −1357 to −1083 region of the p21 promoter, and this repression is dependent on the retinoic acid response element (RARE) within that region. NSPc1 competes with RA receptors for the RARE element both in vitro and in vivo.\",\n      \"method\": \"ChIP, DNA pulldown, luciferase reporter assays, RT-PCR, siRNA knockdown\",\n      \"journal\": \"Nucleic Acids Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — ChIP and DNA pulldown with reporter assays showing RARE-dependent mechanism, single lab\",\n      \"pmids\": [\"17088287\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Nspc1/PCGF1 directly binds the −1021 to −784 region of the Oct4 promoter and activates Oct4 transcription in a RARE-dependent manner, thereby positively regulating the Oct4-Nanog-Sox2 pluripotency axis in P19 embryonal carcinoma cells.\",\n      \"method\": \"ChIP, luciferase reporter assay, dominant-negative analysis, siRNA/overexpression\",\n      \"journal\": \"Biochemical and Biophysical Research Communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — ChIP and reporter assay with RARE-dependent mechanism; single lab, moderate methods\",\n      \"pmids\": [\"24113379\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"NSPc1/PCGF1 promotes cancer stem cell self-renewal in glioma by epigenetically repressing RDH16 through direct binding to the −1073 to −823 region of the RDH16 promoter, reducing all-trans retinoic acid (ATRA) synthesis; RDH16 restoration partially rescues the NSPc1-induced stemness enhancement.\",\n      \"method\": \"ChIP, shRNA knockdown, sphere formation assay, xenograft, RT-PCR/Western blot\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — ChIP confirming direct binding plus functional rescue, single lab\",\n      \"pmids\": [\"28394339\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Under endogenous conditions in a neuronal differentiation cell model, PCGF1 physically interacts with all previously reported members of the variant PRC1 complex (including BCOR and KDM2B) and additionally with a pluripotency sub-network including NANOG, OCT4, PATZ1, and DPPA4. PCGF1 knockdown reduces DPPA4 expression at both mRNA and protein levels.\",\n      \"method\": \"Affinity purification–mass spectrometry (AP-MS) under endogenous conditions, siRNA knockdown, Western blot\",\n      \"journal\": \"Scientific Reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — AP-MS with two rounds of interaction mapping plus functional knockdown, single lab\",\n      \"pmids\": [\"26687479\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Pcgf1 loss-of-function in mouse ES cells (CRISPR/Cas9 KO) severely impairs in vitro differentiation while self-renewal is maintained. ChIP shows that Pcgf1 deletion reduces Ring1B and H2AK119ub1 occupancy at target genes, revealing an unexpected positive role of Pcgf1 in gene activation during ES cell lineage specification.\",\n      \"method\": \"CRISPR/Cas9 knockout, RNA-seq, ChIP, differentiation assays\",\n      \"journal\": \"Scientific Reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with ChIP and RNA-seq, single lab\",\n      \"pmids\": [\"28393894\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PCGF1 facilitates deposition of H2AK119ub at MHC class I gene promoters to silence MHC-I transcription in tumor cells. The deubiquitinase BAP1 opposes this by removing H2AK119ub, and PCGF1 depletion restores MHC-I expression and T cell-mediated killing of tumor cells.\",\n      \"method\": \"Genome-wide CRISPR screen, PCGF1 KO/knockdown, ChIP, T cell cytotoxicity assays in multiple tumor lines\",\n      \"journal\": \"Journal of Immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR screen plus functional KO with ChIP and T cell killing assay, single lab\",\n      \"pmids\": [\"38088808\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PCGF1 inhibits MMP10 transcription by upregulating RING1B/H2AK119ub and EZH2/H3K27me3 marks at the MMP10 promoter in microglia, thereby suppressing NF-κB/MAPK pathway activation and neuroinflammation.\",\n      \"method\": \"ChIP, in vivo microglial PCGF1 manipulation, behavioral assays, Western blot\",\n      \"journal\": \"Molecular Psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — ChIP demonstrating promoter occupancy and histone marks with in vivo functional readout, single lab\",\n      \"pmids\": [\"39215186\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NSPc1/PCGF1 requires DNMT3a recruitment for maintenance of DNA methylation at the HOXA11 promoter in trophoblast cells; NSPc1 is required for DNMT3a occupancy, and the NSPc1–DNMT3a cooperation represses HOXA11 and promotes trophoblast cell apoptosis.\",\n      \"method\": \"ChIP, siRNA knockdown, co-immunoprecipitation, bisulfite sequencing, apoptosis assays\",\n      \"journal\": \"Acta Biochimica et Biophysica Sinica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — ChIP and Co-IP showing NSPc1–DNMT3a interaction with functional apoptosis readout, single lab\",\n      \"pmids\": [\"36815373\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MORC4 interacts physically with PCGF1 (by co-immunoprecipitation) and augments PCGF1's repression of CDKN1A (p21) transcription; MORC4 itself does not substantially suppress CDKN1A activity but potentiates PCGF1's effect. MORC4 is degraded via the ubiquitin-proteasome system by HECW2.\",\n      \"method\": \"Co-immunoprecipitation, luciferase reporter assay, siRNA/overexpression, Western blot\",\n      \"journal\": \"Cancer Gene Therapy\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP plus reporter assay, single lab, limited mechanistic detail\",\n      \"pmids\": [\"36932196\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Pcgf1 loss-of-function in zebrafish decreases H3K27me3 at the promoters of Ngn1 and Otx2 and decreases H3K4me3 at the promoters of Pou5f3 and Nanog, implicating Pcgf1 in maintaining specific histone methylation states during early neural tube development.\",\n      \"method\": \"Morpholino knockdown in zebrafish, ChIP, RNA-seq in P19 cells\",\n      \"journal\": \"Frontiers in Cell and Developmental Biology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — ChIP on specific promoters in knockdown cells, single lab, limited mechanistic follow-up\",\n      \"pmids\": [\"33575252\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"USP15 deubiquitinates and stabilizes TFAP4, which transcriptionally activates PCGF1; the USP15–TFAP4–PCGF1 axis promotes EMT, invasion, and stemness in colorectal cancer cells.\",\n      \"method\": \"Co-immunoprecipitation, dual luciferase reporter assay, oligonucleotide pulldown, ChIP, siRNA knockdown\",\n      \"journal\": \"Biochemical Pharmacology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — multiple assays but primarily showing upstream regulation of PCGF1 expression; PCGF1's own mechanism not further resolved, single lab\",\n      \"pmids\": [\"38801926\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PCGF1 is a core subunit of variant Polycomb Repressive Complex 1 (PRC1.1) whose RAWUL domain selectively binds the PUFD domains of BCOR/BCORL1 to recruit KDM2B/SKP1, forming a minimal complex that mono-ubiquitylates H2AK119 on chromatin; this activity—shown at single-molecule resolution to depend on transient sampling until a catalytically competent nucleosome-bound state is achieved—silences developmental genes by promoting PRC2 recruitment and H3K27me3 deposition, while at DNA damage sites the FBXL10–PCGF1–RNF2 complex is recruited in a PARP1/TIMELESS-dependent manner to drive H2AK119ub1, H2A.Z incorporation, and homologous recombination repair.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PCGF1 (NSPc1) is a core subunit of variant Polycomb Repressive Complex 1 (PRC1.1) that targets H2AK119 mono-ubiquitylation to developmental and lineage-control genes, coupling Polycomb repression to PRC2 recruitment and chromatin silencing [#4]. Its RAWUL domain selectively engages the PUFD domain of BCOR/BCORL1 — but not the RAWUL domains of PCGF2/MEL18 or PCGF4/BMI1 — and this interface assembles a minimal four-component KDM2B/SKP1/BCORL1/PCGF1 complex, the structural basis for PCGF1-specific PRC1.1 assembly [#0, #1]. PCGF1 directly contacts both RING2/RING1B and H2A to stimulate H2AK119 ubiquitylation [#2], and at the single-molecule level the PCGF1 complex transiently samples chromatin until reaching a catalytically competent nucleosome-bound state, with intrinsically lower activity and weaker processivity than PCGF4-containing PRC1 [#6]. Functionally, PCGF1-deposited H2AK119ub1 recruits PRC2 and licenses H3K27me3 to drive differentiation-associated gene down-regulation in ESCs [#4], and at replication forks the complex governs nucleosome deposition to restrain premature myeloid differentiation in hematopoietic stem/progenitor cells [#5]. Beyond canonical silencing, the FBXL10(KDM2B)–PCGF1–RNF2 ligase complex is transiently recruited to DNA damage sites in a PARP1/TIMELESS-dependent manner to drive H2AK119ub1, H2A.Z incorporation, and homologous recombination repair [#3]. PCGF1 additionally silences specific promoters including MHC class I genes — opposed by the deubiquitinase BAP1 — to limit T cell-mediated tumor killing [#13], and at several gene-specific targets (HOXA7, CDKN1A/p21) it cooperates with EZH2, Dnmt1, and DNMT3a to integrate H2AK119ub with H3K27me3 and DNA methylation [#2, #8].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Established PCGF1/NSPc1 as a nuclear transcriptional repressor and identified a regulatory phosphorylation site, providing the first functional handle on the protein before its Polycomb role was defined.\",\n      \"evidence\": \"Subcellular fractionation/immunofluorescence and luciferase reporter assays with deletion/point mutants\",\n      \"pmids\": [\"15620699\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Repression mechanism not linked to chromatin modification at this stage\", \"PKC-dependent regulation of S183 not tested in vivo\", \"No target genes identified\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Connected PCGF1 to histone modification by showing it stimulates H2A ubiquitylation via direct RING2 and H2A contacts and cooperates with EZH2/Dnmt1 silencing, placing it within a Polycomb-DNA methylation axis.\",\n      \"evidence\": \"In vitro ubiquitination assay, Co-IP, ChIP and siRNA knockdown at the HOXA7 promoter\",\n      \"pmids\": [\"18460542\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the full PRC1.1 complex composition\", \"Direction of EZH2/PCGF1 recruitment hierarchy only partially resolved\", \"Genome-wide targets unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Resolved the structural and selectivity basis for PCGF1 recruitment, showing the PCGF1 RAWUL domain binds BCOR PUFD selectively over other PCGF paralogs.\",\n      \"evidence\": \"X-ray crystallography of the BCOR PUFD–PCGF1 RAWUL complex with in vitro binding and analytical ultracentrifugation\",\n      \"pmids\": [\"23523425\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not show catalytic consequences of the interaction\", \"Full PRC1.1 assembly not reconstituted in this study\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined the minimal PRC1.1 assembly by showing PCGF1–BCORL1 heterodimerization is required to recruit KDM2B and build a four-component complex, and rationalized tumor-associated BCOR duplications structurally.\",\n      \"evidence\": \"Crystal structure of the tetrameric KDM2B/SKP1/BCORL1/PCGF1 complex with in vitro reconstitution and domain mapping\",\n      \"pmids\": [\"27568929\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Catalytic activity of the reconstituted complex on nucleosomes not measured here\", \"In vivo requirement of the extended interface not tested\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Revealed a context-dependent and even positive role for PCGF1 in gene regulation during differentiation, complicating a purely repressive model.\",\n      \"evidence\": \"CRISPR/Cas9 KO in mouse ES cells with RNA-seq, ChIP and differentiation assays\",\n      \"pmids\": [\"28393894\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of positive gene activation not resolved\", \"Single lab\", \"Distinction between direct and indirect targets unclear\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Extended PCGF1 function beyond transcription to genome maintenance, identifying the FBXL10–PCGF1–RNF2 ligase as a PARP1/TIMELESS-dependent responder at DNA damage sites driving HR repair.\",\n      \"evidence\": \"Live-cell imaging, laser micro-irradiation, Co-IP and HR/DSB functional assays\",\n      \"pmids\": [\"29985131\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct PARP1/TIMELESS-PCGF1 recruitment interface not defined\", \"Substrate range beyond H2AK119 at damage sites unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Defined the pathway position of PCGF1-PRC1 in development, showing its H2AK119ub1 deposition is required for PRC2 recruitment and H3K27me3 during differentiation.\",\n      \"evidence\": \"PCGF1 KO in ESCs with ChIP-seq, RNA-seq and embryoid body differentiation\",\n      \"pmids\": [\"34504070\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which H2AK119ub1 recruits PRC2 not directly demonstrated here\", \"Target gene selectivity determinants unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified an unexpected replication-fork function in which PCGF1-PRC1 controls nucleosome deposition on nascent DNA to enable downstream PRC2 repression and restrain premature myeloid differentiation.\",\n      \"evidence\": \"Conditional KO in HSPCs with iPOND/nascent chromatin capture, ChIP-seq and RNA-seq\",\n      \"pmids\": [\"36443290\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How PCGF1 is recruited to forks is unknown\", \"Relationship between fork function and canonical H2AK119ub deposition not fully separated\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Resolved the catalytic mechanism at single-molecule level, showing PCGF1-PRC1 transiently samples chromatin to reach a competent state and is intrinsically less active and less processive than PCGF4-PRC1.\",\n      \"evidence\": \"Single-molecule fluorescence microscopy with reconstituted in vitro chromatin ubiquitylation (preprint)\",\n      \"pmids\": [\"bio_10.1101_2024.10.25.620026\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Preprint, single lab, not yet peer-reviewed\", \"Cellular determinants modulating sampling kinetics unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended PCGF1-mediated silencing to immune evasion and inflammation, showing it represses MHC-I (opposed by BAP1) and MMP10 to limit T cell killing and neuroinflammation.\",\n      \"evidence\": \"Genome-wide CRISPR screen, KO/knockdown, ChIP, T cell cytotoxicity and in vivo microglial assays\",\n      \"pmids\": [\"38088808\", \"39215186\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether MHC-I and MMP10 silencing reflect canonical PRC1.1 targeting not fully established\", \"BAP1-PCGF1 antagonism mechanism at specific loci not structurally defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PCGF1 target selectivity, replication-fork recruitment, and damage-site recruitment are coordinated across its repressive, developmental, and DNA-repair functions remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking PCGF1 recruitment cues across chromatin contexts\", \"Determinants of locus-specific recruitment beyond BCOR/BCORL1 binding unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2, 3, 6]},\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [4, 8, 13]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [8, 9, 10]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [2, 4, 5]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [4, 8, 13]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [4, 5, 12]}\n    ],\n    \"complexes\": [\"variant PRC1.1 (KDM2B/SKP1/BCOR-BCORL1/PCGF1)\", \"FBXL10(KDM2B)-PCGF1(RNF68)-RNF2 (FRRUC)\"],\n    \"partners\": [\"BCOR\", \"BCORL1\", \"KDM2B\", \"RNF2\", \"RING1B\", \"EZH2\", \"DNMT3a\", \"MORC4\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":6,"faith_pct":83.33333333333333}}