{"gene":"PCGF1","run_date":"2026-04-29T11:37:58","timeline":{"discoveries":[{"year":2013,"finding":"Crystal structure of PCGF1 RAWUL domain in complex with BCOR PUFD domain reveals that BCOR PUFD selectively binds PCGF1 (and PCGF3) but not PCGF2 (MEL18) or PCGF4 (BMI1), with selectivity determined by specific residues within the RAWUL interaction surface.","method":"X-ray crystallography, in vitro binding assays, analytical ultracentrifugation","journal":"Structure","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with functional binding selectivity validated by multiple biophysical methods","pmids":["23523425"],"is_preprint":false},{"year":2016,"finding":"Crystal structure of KDM2B/SKP1/BCORL1/PCGF1 complex reveals that the BCORL1 PUFD domain positions residues preceding the PCGF1 RAWUL domain to create an extended interface for interaction with KDM2B, enabling recruitment of PRC1.1 to CpG islands; a minimal four-component PRC1.1 complex can be reconstituted from KDM2B/SKP1 and BCORL1/PCGF1 subcomplexes.","method":"X-ray crystallography, in vitro assembly assays, analytical ultracentrifugation","journal":"Structure","confidence":"High","confidence_rationale":"Tier 1 — crystal structure plus reconstitution of minimal complex with domain mapping","pmids":["27568929"],"is_preprint":false},{"year":2008,"finding":"PCGF1 (NSPc1) stimulates histone H2A ubiquitination in vivo and in vitro through direct interaction with both RING2 and H2A, and cooperates with EZH2 and DNMT1 in HOX gene (HOXA7) silencing; EZH2-mediated H3K27me3 is required upstream for NSPc1 recruitment and H2A ubiquitination.","method":"In vitro ubiquitination assay, Co-IP, ChIP, siRNA knockdown, RT-PCR","journal":"Nucleic Acids Research","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro ubiquitination assay combined with ChIP and genetic knockdown epistasis","pmids":["18460542"],"is_preprint":false},{"year":2005,"finding":"NSPc1 (PCGF1) localizes predominantly to the nucleus and mediates transcriptional repression; the C-terminal domain and PKC phosphorylation site at S183 are required for its transcriptional repression activity.","method":"Western blotting, subcellular fractionation, reporter repression assay, site-directed mutagenesis","journal":"FEBS Letters","confidence":"Medium","confidence_rationale":"Tier 2–3 — direct localization with functional mutagenesis of phosphorylation site, single lab","pmids":["15620699"],"is_preprint":false},{"year":2006,"finding":"NSPc1 (PCGF1) represses p21Waf1/Cip1 transcription by binding to the −1357 to −1083 region of its promoter via the RARE element, competing with RA receptors at this site in vivo and in vitro.","method":"Luciferase reporter assay, ChIP, DNA pulldown, RT-PCR","journal":"Nucleic Acids Research","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP and DNA pulldown with functional reporter assay, single lab","pmids":["17088287"],"is_preprint":false},{"year":2015,"finding":"PCGF1 physically interacts with all known components of the variant PRC1 complex (including BCOR and KDM2B) and additionally interacts with pluripotency factors NANOG, OCT4, PATZ1, and DPPA4 under endogenous conditions; knockdown of PCGF1 reduces DPPA4 expression at mRNA and protein levels.","method":"Affinity purification–mass spectrometry (AP-MS) under endogenous conditions, reciprocal Co-IP, siRNA knockdown","journal":"Scientific Reports","confidence":"Medium","confidence_rationale":"Tier 2 — quantitative AP-MS with reciprocal validation, single lab","pmids":["26687479"],"is_preprint":false},{"year":2021,"finding":"PCGF1-containing variant PRC1 (PCGF1-PRC1) mediates differentiation-associated transcriptional downregulation by depositing H2AK119ub1 and recruiting PRC2 to target gene loci upon differentiation cues; loss of PCGF1-PRC1 disrupts both H2AK119ub1 deposition and PRC2 recruitment, causing aberrant target gene expression.","method":"CRISPR/Cas9 knockout in mouse ESCs, ChIP-seq, RNA-seq, embryoid body differentiation","journal":"Nature Communications","confidence":"High","confidence_rationale":"Tier 2 — clean KO with genome-wide ChIP-seq epistasis between PCGF1-PRC1 and PRC2 recruitment, multiple orthogonal methods","pmids":["34504070"],"is_preprint":false},{"year":2017,"finding":"Loss of Pcgf1 in mouse ESCs (CRISPR/Cas9) causes severe differentiation defects and reduces Ring1B and H2AK119ub1 binding at target genes, revealing a role for Pcgf1 in gene activation during lineage specification in addition to repression.","method":"CRISPR/Cas9 knockout, RNA-seq, ChIP, in vitro differentiation assays","journal":"Scientific Reports","confidence":"Medium","confidence_rationale":"Tier 2 — clean KO with ChIP and transcriptome analysis, single lab","pmids":["28393894"],"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, enabling proper nucleosome deposition and downstream PRC2-mediated repression of target genes (e.g., Hmga2), thereby maintaining hematopoietic stem and progenitor cell differentiation potential.","method":"Conditional KO in HSPCs, iPOND (nascent DNA proteomics), ChIP-seq, RNA-seq, ATAC-seq","journal":"Nature Communications","confidence":"High","confidence_rationale":"Tier 2 — conditional KO with iPOND, ChIP-seq, and ATAC-seq demonstrating replication fork function, multiple orthogonal methods","pmids":["36443290"],"is_preprint":false},{"year":2018,"finding":"The FBXL10 (KDM2B)–RNF68–RNF2 ubiquitin ligase complex (FRRUC), which contains PCGF1 as a core component (FBXL10 = KDM2B), is recruited to sites of DNA damage in a PARP1- and TIMELESS-dependent manner to mono-ubiquitylate H2A at K119, promoting H2A.Z incorporation and homologous recombination repair.","method":"Live-cell imaging, Co-IP, ChIP, siRNA/shRNA knockdown, in vitro ubiquitylation, HR reporter assay","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods, but PCGF1 involvement is inferred as component of the FRRUC complex rather than directly tested","pmids":["29985131"],"is_preprint":false},{"year":2024,"finding":"PCGF1-containing PRC1 facilitates deposition of H2AK119ub at MHC-I gene promoters to silence MHC-I transcription; BAP1 opposes this by removing the ubiquitin mark; PCGF1 depletion restores MHC-I expression and T cell-mediated tumor killing.","method":"Genome-wide CRISPR screen, ChIP, siRNA knockdown, T cell killing assay","journal":"Journal of Immunology","confidence":"Medium","confidence_rationale":"Tier 2 — genome-wide unbiased screen with functional ChIP validation and T cell functional readout, single lab","pmids":["38088808"],"is_preprint":false},{"year":2013,"finding":"NSPc1 (PCGF1) directly activates Oct4 transcription by binding to the −1021 to −784 region of the Oct4 promoter in a RARE-dependent manner, maintaining the pluripotency network (Oct4-Nanog-Sox2) in P19 embryonal carcinoma cells.","method":"Luciferase reporter assay, ChIP, dominant-negative analysis, siRNA/overexpression","journal":"Biochemical and Biophysical Research Communications","confidence":"Medium","confidence_rationale":"Tier 3 — ChIP and reporter assay with dominant-negative, single lab, single study","pmids":["24113379"],"is_preprint":false},{"year":2024,"finding":"PCGF1 inhibits MMP10 transcription by upregulating RING1B-mediated H2AK119ub and EZH2-mediated H3K27me3 at the MMP10 promoter in microglia, thereby suppressing NF-κB/MAPK-driven neuroinflammation.","method":"ChIP, siRNA knockdown in vivo and in vitro, cytokine measurement, behavioral assays","journal":"Molecular Psychiatry","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP with mechanistic knockdown validated in vivo and in vitro, single lab","pmids":["39215186"],"is_preprint":false},{"year":2023,"finding":"PCGF1 represses HOXA11 expression in trophoblast cells by recruiting DNMT3a to maintain DNA methylation at the HOXA11 promoter; the interplay between NSPc1 and DNMT3a cooperatively silences HOXA11 and promotes apoptosis.","method":"ChIP, bisulfite sequencing, siRNA knockdown, Co-IP, apoptosis assays","journal":"Acta Biochimica et Biophysica Sinica","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP with bisulfite sequencing and Co-IP demonstrating DNMT3a recruitment, single lab","pmids":["36815373"],"is_preprint":false},{"year":2017,"finding":"NSPc1 (PCGF1) epigenetically represses RDH16 expression by directly binding to the −1073 to −823 region of the RDH16 promoter, suppressing ATRA synthesis and promoting cancer stem cell self-renewal in glioma.","method":"ChIP, siRNA knockdown, sphere formation assay, xenograft assay","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2–3 — ChIP with functional rescue assay, single lab","pmids":["28394339"],"is_preprint":false},{"year":2023,"finding":"MORC4 physically interacts with PCGF1 (Co-IP) and augments PCGF1-mediated transcriptional repression of CDKN1A, promoting colorectal cancer progression; MORC4 itself is degraded via HECW2-mediated ubiquitination.","method":"Co-immunoprecipitation, luciferase reporter assay, siRNA knockdown, ChIP","journal":"Cancer Gene Therapy","confidence":"Low","confidence_rationale":"Tier 3 — single Co-IP with partial mechanistic follow-up, single lab","pmids":["36932196"],"is_preprint":false},{"year":2019,"finding":"NSPc1 (PCGF1) protein complex binds lncRNAs MALAT1, SOX2OT, and ANRIL in glioma cells as demonstrated by RNA immunoprecipitation, and co-regulation of NSPc1 with these lncRNAs affects p21 and OCT4 transcription.","method":"RNA immunoprecipitation (RIP), RT-PCR, siRNA knockdown","journal":"Oncology Letters","confidence":"Low","confidence_rationale":"Tier 3 — single RIP method, limited mechanistic follow-up, single lab","pmids":["31186810"],"is_preprint":false},{"year":2024,"finding":"Single-molecule imaging reveals that PCGF1-containing variant PRC1 transiently samples chromatin until reaching a catalytically competent nucleosome-bound state that enables E2 recruitment and ubiquitin transfer; PCGF1-PRC1 has a distinct (lower) probability of achieving this catalytically competent state compared to PCGF4-PRC1, explaining subtype-specific activity differences.","method":"Single-molecule fluorescence microscopy, in vitro reconstituted ubiquitylation assay on nucleosomal arrays","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 — reconstituted single-molecule assay with direct mechanistic readout, but preprint not yet peer-reviewed","pmids":["bio_10.1101_2024.10.25.620026"],"is_preprint":true}],"current_model":"PCGF1 is a core subunit of the non-canonical PRC1.1 complex that selectively binds BCOR/BCORL1 via its RAWUL domain, recruits the KDM2B/SKP1 heterodimer to CpG islands, and catalyzes H2AK119 mono-ubiquitination (through RING1B/RNF2) to silence developmental and lineage-inappropriate genes; it also cooperates with EZH2/PRC2-mediated H3K27me3 and DNA methylation for long-term gene repression, functions at the replication fork to ensure proper nucleosome deposition, and its catalytic competence is governed by the dynamic formation of an active PCGF1-PRC1–E2–chromatin ternary complex."},"narrative":{"teleology":[{"year":2005,"claim":"Establishing that PCGF1 is a nuclear protein whose transcriptional repression activity depends on its C-terminal domain and PKC-mediated phosphorylation at S183 provided the first functional map of the protein.","evidence":"Subcellular fractionation, reporter repression assay, and site-directed mutagenesis in cultured cells","pmids":["15620699"],"confidence":"Medium","gaps":["No identification of endogenous target genes","PKC phosphorylation at S183 not validated in vivo with phospho-specific reagents","Repression mechanism (direct DNA binding vs. complex recruitment) unresolved"]},{"year":2006,"claim":"Demonstrating that PCGF1 binds the p21 promoter via a RARE element and competes with retinoic acid receptors established it as a sequence-directed transcriptional repressor at a defined genomic locus.","evidence":"ChIP, DNA pulldown, and luciferase reporter assay in cultured cells","pmids":["17088287"],"confidence":"Medium","gaps":["Whether PCGF1 directly contacts DNA or acts through an intermediary was not resolved","Generality beyond p21 unknown"]},{"year":2008,"claim":"Showing that PCGF1 directly stimulates RING1B-mediated H2AK119 ubiquitination and that its recruitment depends on upstream EZH2/H3K27me3 established the catalytic function and hierarchical relationship between PRC1.1 and PRC2.","evidence":"In vitro ubiquitination assay, Co-IP, ChIP, and siRNA knockdown epistasis at HOX loci","pmids":["18460542"],"confidence":"High","gaps":["Whether PCGF1 directly contacts H2A or acts solely through RING1B stimulation was unclear","No genome-wide target identification"]},{"year":2013,"claim":"Solving the PCGF1 RAWUL–BCOR PUFD crystal structure revealed the structural basis for selective assembly of PRC1.1 versus canonical PRC1, explaining why BCOR binds PCGF1/3 but not PCGF2/4.","evidence":"X-ray crystallography, analytical ultracentrifugation, and in vitro binding assays","pmids":["23523425"],"confidence":"High","gaps":["Full quaternary architecture of PRC1.1 not yet resolved","No in vivo validation of selectivity-determining residues"]},{"year":2013,"claim":"Finding that PCGF1 directly activates Oct4 transcription by binding its promoter via a RARE element indicated that PCGF1 can act as both a repressor and an activator depending on genomic context.","evidence":"ChIP, luciferase reporter, dominant-negative, siRNA/overexpression in P19 cells","pmids":["24113379"],"confidence":"Medium","gaps":["Mechanism distinguishing activation from repression at PCGF1-bound loci not determined","Single cell line (P19), generality unclear"]},{"year":2015,"claim":"Endogenous AP-MS identification of PCGF1 interacting with all known PRC1.1 subunits plus pluripotency factors (NANOG, OCT4, DPPA4) expanded the complex's interactome and linked it to the pluripotency network.","evidence":"Affinity purification–mass spectrometry under endogenous conditions with reciprocal Co-IP in ESCs","pmids":["26687479"],"confidence":"Medium","gaps":["Whether pluripotency factor interactions are direct or bridged through PRC1.1 subunits unknown","Functional consequence of most interactions not tested"]},{"year":2016,"claim":"The crystal structure of a four-component KDM2B/SKP1/BCORL1/PCGF1 complex revealed how BCORL1 creates an extended interface enabling KDM2B recruitment, explaining PRC1.1 targeting to CpG islands.","evidence":"X-ray crystallography plus in vitro reconstitution and analytical ultracentrifugation","pmids":["27568929"],"confidence":"High","gaps":["Structure lacks RING1B and the ubiquitin-transfer module","Chromatin-bound conformation unknown"]},{"year":2017,"claim":"CRISPR knockout of Pcgf1 in mouse ESCs revealed severe differentiation defects and reduced Ring1B/H2AK119ub at target genes, establishing a non-redundant role for PCGF1 in lineage specification.","evidence":"CRISPR/Cas9 knockout, RNA-seq, ChIP, in vitro differentiation in mouse ESCs","pmids":["28393894"],"confidence":"Medium","gaps":["In vivo embryonic phenotype not examined","Extent of redundancy with other PCGF paralogs not systematically tested"]},{"year":2021,"claim":"Genome-wide analysis in differentiating ESCs showed that PCGF1-PRC1 deposits H2AK119ub1 de novo at differentiation-responsive loci and is required upstream for PRC2 recruitment, revising the earlier model of PRC2-first hierarchy.","evidence":"CRISPR/Cas9 knockout in mouse ESCs, ChIP-seq for H2AK119ub1 and H3K27me3, RNA-seq, embryoid body differentiation","pmids":["34504070"],"confidence":"High","gaps":["Whether PCGF1-PRC1 initiates PRC2 recruitment at all loci or only differentiation-responsive ones is unresolved","Mechanism of de novo targeting upon differentiation unknown"]},{"year":2022,"claim":"iPOND proteomics and conditional knockout revealed that PCGF1-PRC1 acts at the replication fork to prevent activator and chromatin remodeler overloading on nascent DNA, establishing a replication-coupled function beyond steady-state gene silencing.","evidence":"Conditional KO in HSPCs, iPOND, ChIP-seq, ATAC-seq","pmids":["36443290"],"confidence":"High","gaps":["Whether replication fork function is specific to PCGF1-PRC1 or shared by other variant PRC1 complexes not tested","Structural basis for fork association unknown"]},{"year":2024,"claim":"CRISPR screening identified PCGF1-PRC1 as a silencer of MHC-I genes via H2AK119ub deposition, opposed by BAP1 deubiquitination, linking PRC1.1 to immune evasion in cancer.","evidence":"Genome-wide CRISPR screen, ChIP, siRNA knockdown, T cell killing assay","pmids":["38088808"],"confidence":"Medium","gaps":["Whether PCGF1 directly occupies MHC-I promoters or acts indirectly not fully resolved","In vivo tumor immune evasion role not tested"]},{"year":null,"claim":"How PCGF1-PRC1 selects target loci in a context-dependent manner (repression at some promoters, activation at others) and what determines its differential catalytic competence relative to other PRC1 subtypes on chromatin remain open questions.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structure of full PCGF1-PRC1 on a nucleosome substrate","Mechanism of context-dependent activation versus repression unresolved","In vivo requirement during mammalian embryogenesis not reported"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[2,6,8,10,12]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[3,4,11,14]},{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[2,6]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[3]},{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[6,8]}],"pathway":[{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[2,6,8,10,12]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[6,7]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[4,11,14]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[9]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[10]}],"complexes":["PRC1.1 (variant Polycomb repressive complex 1.1)","FRRUC (FBXL10-RNF68-RNF2 ubiquitin ligase complex)"],"partners":["BCOR","BCORL1","RNF2","KDM2B","SKP1","EZH2","MORC4","DNMT3A"],"other_free_text":[]},"mechanistic_narrative":"PCGF1 is a core subunit of the non-canonical Polycomb repressive complex PRC1.1 that directs histone H2AK119 mono-ubiquitination and gene silencing at CpG island-containing promoters during development, differentiation, and immune regulation. Its RAWUL domain selectively binds BCOR/BCORL1 (but not PCGF2/4-associated partners), and this interaction creates an extended surface that recruits the KDM2B–SKP1 heterodimer, enabling CpG island targeting [PMID:23523425, PMID:27568929]. PCGF1 stimulates RING1B-dependent H2AK119ub1 deposition and cooperates with PRC2-mediated H3K27me3 and DNMT-dependent DNA methylation to achieve stable transcriptional repression of developmental genes including HOX loci, MHC-I genes, and cell-cycle regulators such as p21 [PMID:18460542, PMID:34504070, PMID:38088808, PMID:36815373]. Beyond canonical gene silencing, PCGF1-PRC1 functions at the replication fork to prevent inappropriate activator loading onto nascent DNA and ensure proper nucleosome deposition, thereby maintaining stem and progenitor cell differentiation potential [PMID:36443290]."},"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":86,"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":49,"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":43,"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":39,"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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communications","url":"https://pubmed.ncbi.nlm.nih.gov/36443290","citation_count":13,"is_preprint":false},{"pmid":"28849208","id":"PMC_28849208","title":"MicroRNA‑320a inhibition decreases insulin‑induced KGN cell proliferation and apoptosis by targeting PCGF1.","date":"2017","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/28849208","citation_count":11,"is_preprint":false},{"pmid":"32021272","id":"PMC_32021272","title":"Repression of PCGF1 Decreases the Proliferation of Glioblastoma Cells in Association with Inactivation of c-Myc Signaling Pathway.","date":"2020","source":"OncoTargets and therapy","url":"https://pubmed.ncbi.nlm.nih.gov/32021272","citation_count":9,"is_preprint":false},{"pmid":"33575252","id":"PMC_33575252","title":"Pcgf1 Regulates Early Neural Tube Development Through Histone Methylation in Zebrafish.","date":"2021","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/33575252","citation_count":9,"is_preprint":false},{"pmid":"31186810","id":"PMC_31186810","title":"lncRNAs combine and crosstalk with NSPc1 in ATRA-induced differentiation of U87 glioma cells.","date":"2019","source":"Oncology 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":"38801926","id":"PMC_38801926","title":"Ubiquitin-specific peptidase 15 regulates the TFAP4/PCGF1 axis facilitating liver metastasis of colorectal cancer and cell stemness.","date":"2024","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/38801926","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":"36815373","id":"PMC_36815373","title":"Cooperation between NSPc1 and DNA methylation represses HOXA11 expression and promotes apoptosis of trophoblast cells during preeclampsia.","date":"2023","source":"Acta biochimica et biophysica Sinica","url":"https://pubmed.ncbi.nlm.nih.gov/36815373","citation_count":6,"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":4,"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},{"pmid":null,"id":"bio_10.1101_2024.05.21.595144","title":"BCOR-Rearranged Sarcomas:<i>In Silico</i>Insights into Altered Domains and Reduced RAWUL-PUFD Binding","date":"2024-05-21","source":"bioRxiv","url":"https://doi.org/10.1101/2024.05.21.595144","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":15541,"output_tokens":4064,"usd":0.053791},"stage2":{"model":"claude-opus-4-6","input_tokens":7553,"output_tokens":2939,"usd":0.16686},"total_usd":0.220651,"stage1_batch_id":"msgbatch_012ZiiCUBfB62NCTQd4Bk1Jo","stage2_batch_id":"msgbatch_01Xuqq9aUHoQouS7UVGZNStZ","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2013,\n      \"finding\": \"Crystal structure of PCGF1 RAWUL domain in complex with BCOR PUFD domain reveals that BCOR PUFD selectively binds PCGF1 (and PCGF3) but not PCGF2 (MEL18) or PCGF4 (BMI1), with selectivity determined by specific residues within the RAWUL interaction surface.\",\n      \"method\": \"X-ray crystallography, in vitro binding assays, analytical ultracentrifugation\",\n      \"journal\": \"Structure\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with functional binding selectivity validated by multiple biophysical methods\",\n      \"pmids\": [\"23523425\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Crystal structure of KDM2B/SKP1/BCORL1/PCGF1 complex reveals that the BCORL1 PUFD domain positions residues preceding the PCGF1 RAWUL domain to create an extended interface for interaction with KDM2B, enabling recruitment of PRC1.1 to CpG islands; a minimal four-component PRC1.1 complex can be reconstituted from KDM2B/SKP1 and BCORL1/PCGF1 subcomplexes.\",\n      \"method\": \"X-ray crystallography, in vitro assembly assays, analytical ultracentrifugation\",\n      \"journal\": \"Structure\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus reconstitution of minimal complex with domain mapping\",\n      \"pmids\": [\"27568929\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PCGF1 (NSPc1) stimulates histone H2A ubiquitination in vivo and in vitro through direct interaction with both RING2 and H2A, and cooperates with EZH2 and DNMT1 in HOX gene (HOXA7) silencing; EZH2-mediated H3K27me3 is required upstream for NSPc1 recruitment and H2A ubiquitination.\",\n      \"method\": \"In vitro ubiquitination assay, Co-IP, ChIP, siRNA knockdown, RT-PCR\",\n      \"journal\": \"Nucleic Acids Research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro ubiquitination assay combined with ChIP and genetic knockdown epistasis\",\n      \"pmids\": [\"18460542\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"NSPc1 (PCGF1) localizes predominantly to the nucleus and mediates transcriptional repression; the C-terminal domain and PKC phosphorylation site at S183 are required for its transcriptional repression activity.\",\n      \"method\": \"Western blotting, subcellular fractionation, reporter repression assay, site-directed mutagenesis\",\n      \"journal\": \"FEBS Letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — direct localization with functional mutagenesis of phosphorylation site, single lab\",\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 its promoter via the RARE element, competing with RA receptors at this site in vivo and in vitro.\",\n      \"method\": \"Luciferase reporter assay, ChIP, DNA pulldown, RT-PCR\",\n      \"journal\": \"Nucleic Acids Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP and DNA pulldown with functional reporter assay, single lab\",\n      \"pmids\": [\"17088287\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PCGF1 physically interacts with all known components of the variant PRC1 complex (including BCOR and KDM2B) and additionally interacts with pluripotency factors NANOG, OCT4, PATZ1, and DPPA4 under endogenous conditions; knockdown of PCGF1 reduces DPPA4 expression at mRNA and protein levels.\",\n      \"method\": \"Affinity purification–mass spectrometry (AP-MS) under endogenous conditions, reciprocal Co-IP, siRNA knockdown\",\n      \"journal\": \"Scientific Reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — quantitative AP-MS with reciprocal validation, single lab\",\n      \"pmids\": [\"26687479\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PCGF1-containing variant PRC1 (PCGF1-PRC1) mediates differentiation-associated transcriptional downregulation by depositing H2AK119ub1 and recruiting PRC2 to target gene loci upon differentiation cues; loss of PCGF1-PRC1 disrupts both H2AK119ub1 deposition and PRC2 recruitment, causing aberrant target gene expression.\",\n      \"method\": \"CRISPR/Cas9 knockout in mouse ESCs, ChIP-seq, RNA-seq, embryoid body differentiation\",\n      \"journal\": \"Nature Communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with genome-wide ChIP-seq epistasis between PCGF1-PRC1 and PRC2 recruitment, multiple orthogonal methods\",\n      \"pmids\": [\"34504070\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Loss of Pcgf1 in mouse ESCs (CRISPR/Cas9) causes severe differentiation defects and reduces Ring1B and H2AK119ub1 binding at target genes, revealing a role for Pcgf1 in gene activation during lineage specification in addition to repression.\",\n      \"method\": \"CRISPR/Cas9 knockout, RNA-seq, ChIP, in vitro differentiation assays\",\n      \"journal\": \"Scientific Reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with ChIP and transcriptome analysis, single lab\",\n      \"pmids\": [\"28393894\"],\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, enabling proper nucleosome deposition and downstream PRC2-mediated repression of target genes (e.g., Hmga2), thereby maintaining hematopoietic stem and progenitor cell differentiation potential.\",\n      \"method\": \"Conditional KO in HSPCs, iPOND (nascent DNA proteomics), ChIP-seq, RNA-seq, ATAC-seq\",\n      \"journal\": \"Nature Communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — conditional KO with iPOND, ChIP-seq, and ATAC-seq demonstrating replication fork function, multiple orthogonal methods\",\n      \"pmids\": [\"36443290\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The FBXL10 (KDM2B)–RNF68–RNF2 ubiquitin ligase complex (FRRUC), which contains PCGF1 as a core component (FBXL10 = KDM2B), is recruited to sites of DNA damage in a PARP1- and TIMELESS-dependent manner to mono-ubiquitylate H2A at K119, promoting H2A.Z incorporation and homologous recombination repair.\",\n      \"method\": \"Live-cell imaging, Co-IP, ChIP, siRNA/shRNA knockdown, in vitro ubiquitylation, HR reporter assay\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods, but PCGF1 involvement is inferred as component of the FRRUC complex rather than directly tested\",\n      \"pmids\": [\"29985131\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PCGF1-containing PRC1 facilitates deposition of H2AK119ub at MHC-I gene promoters to silence MHC-I transcription; BAP1 opposes this by removing the ubiquitin mark; PCGF1 depletion restores MHC-I expression and T cell-mediated tumor killing.\",\n      \"method\": \"Genome-wide CRISPR screen, ChIP, siRNA knockdown, T cell killing assay\",\n      \"journal\": \"Journal of Immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genome-wide unbiased screen with functional ChIP validation and T cell functional readout, single lab\",\n      \"pmids\": [\"38088808\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"NSPc1 (PCGF1) directly activates Oct4 transcription by binding to the −1021 to −784 region of the Oct4 promoter in a RARE-dependent manner, maintaining the pluripotency network (Oct4-Nanog-Sox2) in P19 embryonal carcinoma cells.\",\n      \"method\": \"Luciferase reporter assay, ChIP, dominant-negative analysis, siRNA/overexpression\",\n      \"journal\": \"Biochemical and Biophysical Research Communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — ChIP and reporter assay with dominant-negative, single lab, single study\",\n      \"pmids\": [\"24113379\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PCGF1 inhibits MMP10 transcription by upregulating RING1B-mediated H2AK119ub and EZH2-mediated H3K27me3 at the MMP10 promoter in microglia, thereby suppressing NF-κB/MAPK-driven neuroinflammation.\",\n      \"method\": \"ChIP, siRNA knockdown in vivo and in vitro, cytokine measurement, behavioral assays\",\n      \"journal\": \"Molecular Psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP with mechanistic knockdown validated in vivo and in vitro, single lab\",\n      \"pmids\": [\"39215186\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PCGF1 represses HOXA11 expression in trophoblast cells by recruiting DNMT3a to maintain DNA methylation at the HOXA11 promoter; the interplay between NSPc1 and DNMT3a cooperatively silences HOXA11 and promotes apoptosis.\",\n      \"method\": \"ChIP, bisulfite sequencing, siRNA knockdown, Co-IP, apoptosis assays\",\n      \"journal\": \"Acta Biochimica et Biophysica Sinica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP with bisulfite sequencing and Co-IP demonstrating DNMT3a recruitment, single lab\",\n      \"pmids\": [\"36815373\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"NSPc1 (PCGF1) epigenetically represses RDH16 expression by directly binding to the −1073 to −823 region of the RDH16 promoter, suppressing ATRA synthesis and promoting cancer stem cell self-renewal in glioma.\",\n      \"method\": \"ChIP, siRNA knockdown, sphere formation assay, xenograft assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — ChIP with functional rescue assay, single lab\",\n      \"pmids\": [\"28394339\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MORC4 physically interacts with PCGF1 (Co-IP) and augments PCGF1-mediated transcriptional repression of CDKN1A, promoting colorectal cancer progression; MORC4 itself is degraded via HECW2-mediated ubiquitination.\",\n      \"method\": \"Co-immunoprecipitation, luciferase reporter assay, siRNA knockdown, ChIP\",\n      \"journal\": \"Cancer Gene Therapy\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP with partial mechanistic follow-up, single lab\",\n      \"pmids\": [\"36932196\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"NSPc1 (PCGF1) protein complex binds lncRNAs MALAT1, SOX2OT, and ANRIL in glioma cells as demonstrated by RNA immunoprecipitation, and co-regulation of NSPc1 with these lncRNAs affects p21 and OCT4 transcription.\",\n      \"method\": \"RNA immunoprecipitation (RIP), RT-PCR, siRNA knockdown\",\n      \"journal\": \"Oncology Letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single RIP method, limited mechanistic follow-up, single lab\",\n      \"pmids\": [\"31186810\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Single-molecule imaging reveals that PCGF1-containing variant PRC1 transiently samples chromatin until reaching a catalytically competent nucleosome-bound state that enables E2 recruitment and ubiquitin transfer; PCGF1-PRC1 has a distinct (lower) probability of achieving this catalytically competent state compared to PCGF4-PRC1, explaining subtype-specific activity differences.\",\n      \"method\": \"Single-molecule fluorescence microscopy, in vitro reconstituted ubiquitylation assay on nucleosomal arrays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted single-molecule assay with direct mechanistic readout, but preprint not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2024.10.25.620026\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"PCGF1 is a core subunit of the non-canonical PRC1.1 complex that selectively binds BCOR/BCORL1 via its RAWUL domain, recruits the KDM2B/SKP1 heterodimer to CpG islands, and catalyzes H2AK119 mono-ubiquitination (through RING1B/RNF2) to silence developmental and lineage-inappropriate genes; it also cooperates with EZH2/PRC2-mediated H3K27me3 and DNA methylation for long-term gene repression, functions at the replication fork to ensure proper nucleosome deposition, and its catalytic competence is governed by the dynamic formation of an active PCGF1-PRC1–E2–chromatin ternary complex.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PCGF1 is a core subunit of the non-canonical Polycomb repressive complex PRC1.1 that directs histone H2AK119 mono-ubiquitination and gene silencing at CpG island-containing promoters during development, differentiation, and immune regulation. Its RAWUL domain selectively binds BCOR/BCORL1 (but not PCGF2/4-associated partners), and this interaction creates an extended surface that recruits the KDM2B–SKP1 heterodimer, enabling CpG island targeting [PMID:23523425, PMID:27568929]. PCGF1 stimulates RING1B-dependent H2AK119ub1 deposition and cooperates with PRC2-mediated H3K27me3 and DNMT-dependent DNA methylation to achieve stable transcriptional repression of developmental genes including HOX loci, MHC-I genes, and cell-cycle regulators such as p21 [PMID:18460542, PMID:34504070, PMID:38088808, PMID:36815373]. Beyond canonical gene silencing, PCGF1-PRC1 functions at the replication fork to prevent inappropriate activator loading onto nascent DNA and ensure proper nucleosome deposition, thereby maintaining stem and progenitor cell differentiation potential [PMID:36443290].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Establishing that PCGF1 is a nuclear protein whose transcriptional repression activity depends on its C-terminal domain and PKC-mediated phosphorylation at S183 provided the first functional map of the protein.\",\n      \"evidence\": \"Subcellular fractionation, reporter repression assay, and site-directed mutagenesis in cultured cells\",\n      \"pmids\": [\"15620699\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No identification of endogenous target genes\", \"PKC phosphorylation at S183 not validated in vivo with phospho-specific reagents\", \"Repression mechanism (direct DNA binding vs. complex recruitment) unresolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrating that PCGF1 binds the p21 promoter via a RARE element and competes with retinoic acid receptors established it as a sequence-directed transcriptional repressor at a defined genomic locus.\",\n      \"evidence\": \"ChIP, DNA pulldown, and luciferase reporter assay in cultured cells\",\n      \"pmids\": [\"17088287\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether PCGF1 directly contacts DNA or acts through an intermediary was not resolved\", \"Generality beyond p21 unknown\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Showing that PCGF1 directly stimulates RING1B-mediated H2AK119 ubiquitination and that its recruitment depends on upstream EZH2/H3K27me3 established the catalytic function and hierarchical relationship between PRC1.1 and PRC2.\",\n      \"evidence\": \"In vitro ubiquitination assay, Co-IP, ChIP, and siRNA knockdown epistasis at HOX loci\",\n      \"pmids\": [\"18460542\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PCGF1 directly contacts H2A or acts solely through RING1B stimulation was unclear\", \"No genome-wide target identification\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Solving the PCGF1 RAWUL–BCOR PUFD crystal structure revealed the structural basis for selective assembly of PRC1.1 versus canonical PRC1, explaining why BCOR binds PCGF1/3 but not PCGF2/4.\",\n      \"evidence\": \"X-ray crystallography, analytical ultracentrifugation, and in vitro binding assays\",\n      \"pmids\": [\"23523425\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full quaternary architecture of PRC1.1 not yet resolved\", \"No in vivo validation of selectivity-determining residues\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Finding that PCGF1 directly activates Oct4 transcription by binding its promoter via a RARE element indicated that PCGF1 can act as both a repressor and an activator depending on genomic context.\",\n      \"evidence\": \"ChIP, luciferase reporter, dominant-negative, siRNA/overexpression in P19 cells\",\n      \"pmids\": [\"24113379\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism distinguishing activation from repression at PCGF1-bound loci not determined\", \"Single cell line (P19), generality unclear\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Endogenous AP-MS identification of PCGF1 interacting with all known PRC1.1 subunits plus pluripotency factors (NANOG, OCT4, DPPA4) expanded the complex's interactome and linked it to the pluripotency network.\",\n      \"evidence\": \"Affinity purification–mass spectrometry under endogenous conditions with reciprocal Co-IP in ESCs\",\n      \"pmids\": [\"26687479\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether pluripotency factor interactions are direct or bridged through PRC1.1 subunits unknown\", \"Functional consequence of most interactions not tested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"The crystal structure of a four-component KDM2B/SKP1/BCORL1/PCGF1 complex revealed how BCORL1 creates an extended interface enabling KDM2B recruitment, explaining PRC1.1 targeting to CpG islands.\",\n      \"evidence\": \"X-ray crystallography plus in vitro reconstitution and analytical ultracentrifugation\",\n      \"pmids\": [\"27568929\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure lacks RING1B and the ubiquitin-transfer module\", \"Chromatin-bound conformation unknown\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"CRISPR knockout of Pcgf1 in mouse ESCs revealed severe differentiation defects and reduced Ring1B/H2AK119ub at target genes, establishing a non-redundant role for PCGF1 in lineage specification.\",\n      \"evidence\": \"CRISPR/Cas9 knockout, RNA-seq, ChIP, in vitro differentiation in mouse ESCs\",\n      \"pmids\": [\"28393894\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo embryonic phenotype not examined\", \"Extent of redundancy with other PCGF paralogs not systematically tested\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Genome-wide analysis in differentiating ESCs showed that PCGF1-PRC1 deposits H2AK119ub1 de novo at differentiation-responsive loci and is required upstream for PRC2 recruitment, revising the earlier model of PRC2-first hierarchy.\",\n      \"evidence\": \"CRISPR/Cas9 knockout in mouse ESCs, ChIP-seq for H2AK119ub1 and H3K27me3, RNA-seq, embryoid body differentiation\",\n      \"pmids\": [\"34504070\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PCGF1-PRC1 initiates PRC2 recruitment at all loci or only differentiation-responsive ones is unresolved\", \"Mechanism of de novo targeting upon differentiation unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"iPOND proteomics and conditional knockout revealed that PCGF1-PRC1 acts at the replication fork to prevent activator and chromatin remodeler overloading on nascent DNA, establishing a replication-coupled function beyond steady-state gene silencing.\",\n      \"evidence\": \"Conditional KO in HSPCs, iPOND, ChIP-seq, ATAC-seq\",\n      \"pmids\": [\"36443290\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether replication fork function is specific to PCGF1-PRC1 or shared by other variant PRC1 complexes not tested\", \"Structural basis for fork association unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"CRISPR screening identified PCGF1-PRC1 as a silencer of MHC-I genes via H2AK119ub deposition, opposed by BAP1 deubiquitination, linking PRC1.1 to immune evasion in cancer.\",\n      \"evidence\": \"Genome-wide CRISPR screen, ChIP, siRNA knockdown, T cell killing assay\",\n      \"pmids\": [\"38088808\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether PCGF1 directly occupies MHC-I promoters or acts indirectly not fully resolved\", \"In vivo tumor immune evasion role not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PCGF1-PRC1 selects target loci in a context-dependent manner (repression at some promoters, activation at others) and what determines its differential catalytic competence relative to other PRC1 subtypes on chromatin remain open questions.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structure of full PCGF1-PRC1 on a nucleosome substrate\", \"Mechanism of context-dependent activation versus repression unresolved\", \"In vivo requirement during mammalian embryogenesis not reported\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2, 6, 8, 10, 12]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [3, 4, 11, 14]},\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [2, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [6, 8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [2, 6, 8, 10, 12]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [6, 7]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [4, 11, 14]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [9]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [10]}\n    ],\n    \"complexes\": [\n      \"PRC1.1 (variant Polycomb repressive complex 1.1)\",\n      \"FRRUC (FBXL10-RNF68-RNF2 ubiquitin ligase complex)\"\n    ],\n    \"partners\": [\n      \"BCOR\",\n      \"BCORL1\",\n      \"RNF2\",\n      \"KDM2B\",\n      \"SKP1\",\n      \"EZH2\",\n      \"MORC4\",\n      \"DNMT3A\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}