{"gene":"BACC1","run_date":"2026-06-09T22:02:44","timeline":{"discoveries":[{"year":2016,"finding":"BAP18 acts as a coactivator of androgen receptor (AR) in both Drosophila and mammalian cells; it facilitates recruitment of the MLL1 subcomplex and AR to androgen-response elements (AREs) of AR target genes, increasing histone H3K4 trimethylation and H4K16 acetylation. BAP18 knockdown attenuates prostate cancer cell growth and xenograft tumor growth.","method":"Co-immunoprecipitation, ChIP assay, luciferase reporter assay, siRNA/shRNA knockdown, xenograft mouse model, Drosophila experimental system","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, ChIP, reporter assay, and in vivo xenograft across multiple systems and cell lines, replicated in subsequent studies","pmids":["27226492"],"is_preprint":false},{"year":2020,"finding":"BAP18 functions as an H3K4me3 reader; it is recruited to promoter regions of CCND1 and CCND2 in oral squamous cell carcinoma cells, facilitating recruitment of MLL1 complex core subunits to increase H3K4me3 levels and activate transcription, thereby promoting G1-S phase transition and cell growth.","method":"ChIP assay, qPCR, western blot, lentiviral shRNA knockdown, colony formation, xenograft tumor experiment","journal":"EBioMedicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and functional knockdown with cell cycle phenotype, single lab with two orthogonal methods","pmids":["32113162"],"is_preprint":false},{"year":2020,"finding":"BAP18 acts as a co-activator of ERα in breast cancer cells; it is recruited to promoter regions of estrogen-induced genes and facilitates recruitment of COMPASS-like core subunits, accompanied by enrichment of H3K4me3, in an E2-dependent manner. BAP18 promotes cell growth and modulates antiestrogen sensitivity.","method":"ChIP-seq, Co-IP, ChIP assay, shRNA knockdown, luciferase reporter assay","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Strong — ChIP-seq plus Co-IP plus functional knockdown with multiple orthogonal methods in a single rigorous study","pmids":["32986841"],"is_preprint":false},{"year":2022,"finding":"BAP18 is recruited to the H3K4me3-marked promoter of S100A9 in triple-negative breast cancer cells, enhancing its promoter activity and transcription. Knockdown of BAP18 suppresses xenograft tumor growth, an effect partially rescued by S100A9 re-expression, placing S100A9 downstream of BAP18.","method":"ChIP assay, luciferase reporter assay, shRNA knockdown, rescue experiment (S100A9 re-expression), xenograft mouse model","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis rescue experiment plus ChIP and in vivo data, single lab","pmids":["35484101"],"is_preprint":false},{"year":2023,"finding":"BAP18 interacts with SMARCA1/BPTF and is required for CTCF recruitment to ERα-enriched enhancers; it facilitates chromatin accessibility within enhancer regions, promotes enhancer RNA transcription, and enhances enhancer-promoter looping. BAP18 depletion increases sensitivity to anti-estrogen and anti-enhancer treatment.","method":"Co-IP, ChIP assay, GRO-seq, ATAC-seq (chromatin accessibility), shRNA knockdown, luciferase reporter assay","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Co-IP, ChIP, GRO-seq, chromatin accessibility) in a single rigorous study demonstrating direct interaction and functional consequence","pmids":["36828916"],"is_preprint":false},{"year":2021,"finding":"BAP18 interacts with androgen receptor (AR) and enhances AR-mediated transactivation in luteinized granulosa cells; BAP18 and AR co-recruit to AREs of CYP19A1 and FSHR promoters. BAP18 also interacts with Sp1 and co-recruits to the AR gene promoter to activate AR transcription. BAP18 knockdown decreases CYP19A1 expression and impairs androgen-to-estrogen conversion.","method":"Co-IP, ChIP assay, siRNA knockdown, qPCR, western blot","journal":"Molecular and cellular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and ChIP with functional knockdown, single lab, two orthogonal methods","pmids":["33662476"],"is_preprint":false},{"year":2023,"finding":"BAP18 co-activates PPARα-mediated transactivation in hepatocellular carcinoma cells and facilitates recruitment of the NuA4/TIP60 complex, thereby increasing histone H4 acetylation at SCD1 loci. BAP18 promotes HCC cell proliferation and lipid accumulation.","method":"Co-IP, ChIP assay, shRNA knockdown, luciferase reporter assay, cell proliferation assay","journal":"Biochimica et biophysica acta. Molecular basis of disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and ChIP with functional readouts, single lab","pmids":["38042310"],"is_preprint":false},{"year":2025,"finding":"BAP18 recruits ACTL6A and PAF1 to Wnt target gene promoters, enhancing β-catenin-mediated transcription in NSCLC cells. Co-immunoprecipitation confirmed interaction between BAP18, β-catenin, ACTL6A, and PAF1; luciferase reporter assays showed increased β-catenin transcriptional activity. BAP18 knockdown inhibited NSCLC cell proliferation, migration, and xenograft tumor growth.","method":"Co-immunoprecipitation, luciferase reporter assay, RNA sequencing, shRNA knockdown, xenograft mouse model, immunohistochemistry","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, reporter assay, and in vivo data, single lab, multiple orthogonal methods","pmids":["40818609"],"is_preprint":false},{"year":2025,"finding":"In AR-positive triple-negative breast cancer cells, BAP18 acts as a transcriptional corepressor of AR by associating with AR and the SIN3A/HDAC subcomplex. BAP18 facilitates SIN3A/HDAC recruitment to AREs in promoters of P21 and PTEN, reducing histone H4 acetylation at those sites and suppressing their expression.","method":"Co-immunoprecipitation, ChIP assay, shRNA knockdown, western blot","journal":"Cell & bioscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and ChIP with functional knockdown demonstrating corepressor activity, single lab","pmids":["41163225"],"is_preprint":false},{"year":2022,"finding":"BAP18 knockdown in NSCLC cell lines (A549, H1299) reduces transcriptional levels of CCND1 and CCND2, delays G1-to-S phase transition, and weakens NSCLC cell growth, indicating BAP18 regulates CCND1/2 transcription to promote cell cycle progression.","method":"siRNA/lentiviral shRNA knockdown, qRT-PCR, western blot, colony formation assay, cell cycle analysis","journal":"European review for medical and pharmacological sciences","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single method category (no ChIP or Co-IP reported), observational correlation between knockdown and target gene expression","pmids":["35587057"],"is_preprint":false}],"current_model":"BAP18 (BACC1/C17orf49) is a chromatin-associated H3K4me3 reader that functions as a transcriptional co-regulator—acting as a coactivator for AR, ERα, and PPARα, or as a corepressor for AR depending on cellular context—by bridging nuclear receptors with chromatin-modifying complexes (MLL1/COMPASS-like, NuA4/TIP60, SIN3A/HDAC) and chromatin remodeling factors (SMARCA1/BPTF), thereby modulating histone H3K4me3, H4K16ac, or H4ac levels at target gene promoters and enhancers to control transcription of genes including CCND1/2, CYP19A1, S100A9, and Wnt target genes through a complex involving ACTL6A and PAF1."},"narrative":{"mechanistic_narrative":"BAP18 (BACC1/C17orf49) is a chromatin-associated H3K4me3 reader that operates as a context-dependent transcriptional co-regulator, bridging sequence-specific nuclear receptors and transcription factors to histone-modifying and chromatin-remodeling machineries at target promoters and enhancers [PMID:27226492, PMID:32986841]. As a coactivator, BAP18 is recruited to androgen-response elements and estrogen-induced gene promoters where it facilitates recruitment of the MLL1/COMPASS-like complex and AR or ERα, increasing H3K4me3 and H4K16 acetylation to drive transcription and cancer cell growth [PMID:27226492, PMID:32986841]. Its reader activity targets it to H3K4me3-marked promoters of growth and effector genes including CCND1/CCND2, S100A9, and CYP19A1, coupling chromatin engagement to G1-S progression and tumor growth [PMID:32113162, PMID:35484101, PMID:33662476]. BAP18 diversifies its mechanism across complexes and pathways: it recruits the NuA4/TIP60 complex to boost H4 acetylation during PPARα-mediated lipogenic transcription [PMID:38042310], partners with SMARCA1/BPTF to enable CTCF recruitment, enhancer accessibility, eRNA transcription, and enhancer-promoter looping at ERα enhancers [PMID:36828916], and recruits ACTL6A and PAF1 to potentiate β-catenin-driven Wnt target transcription [PMID:40818609]. In an opposing role, BAP18 can act as an AR corepressor by recruiting the SIN3A/HDAC subcomplex to AREs of P21 and PTEN, reducing local H4 acetylation and silencing these genes [PMID:41163225], establishing that BAP18 toggles between activating and repressive outputs depending on the associated complex and cellular context.","teleology":[{"year":2016,"claim":"Established BAP18's core function as an AR coactivator that physically links the receptor to a histone methyltransferase complex, defining its mechanism of activating chromatin modification.","evidence":"Co-IP, ChIP, luciferase reporter, knockdown, and xenograft across Drosophila and mammalian prostate cancer systems","pmids":["27226492"],"confidence":"High","gaps":["Did not define the structural basis of H3K4me3 recognition","Generality beyond AR not yet tested"]},{"year":2020,"claim":"Showed BAP18 acts as an H3K4me3 reader that recruits MLL1 core subunits to cyclin gene promoters, connecting its chromatin-reading activity to cell cycle control.","evidence":"ChIP, qPCR, western blot, shRNA knockdown, and xenograft in oral squamous cell carcinoma cells","pmids":["32113162"],"confidence":"Medium","gaps":["Direct H3K4me3 binding affinity/domain not characterized","Single tumor type"]},{"year":2020,"claim":"Extended BAP18 coactivation beyond AR to ERα, showing E2-dependent recruitment of COMPASS-like subunits and a role in antiestrogen sensitivity.","evidence":"ChIP-seq, Co-IP, ChIP, reporter assay, and knockdown in breast cancer cells","pmids":["32986841"],"confidence":"High","gaps":["Genome-wide selectivity of BAP18 recruitment not fully resolved"]},{"year":2021,"claim":"Demonstrated BAP18 cooperates with AR and Sp1 to activate steroidogenic genes, broadening its role beyond cancer to normal endocrine (granulosa cell) physiology.","evidence":"Co-IP, ChIP, siRNA knockdown, qPCR, and western blot in luteinized granulosa cells","pmids":["33662476"],"confidence":"Medium","gaps":["Physiological reproductive phenotype in vivo not established","Single lab"]},{"year":2022,"claim":"Identified S100A9 as a functional downstream effector of BAP18 in triple-negative breast cancer via epistasis rescue, linking BAP18 chromatin activity to a specific oncogenic target.","evidence":"ChIP, reporter assay, shRNA knockdown, S100A9 rescue, and xenograft","pmids":["35484101"],"confidence":"Medium","gaps":["Only partial rescue, other targets contribute","Single lab"]},{"year":2022,"claim":"Reinforced BAP18 control of CCND1/2 transcription and G1-S transition in NSCLC, supporting a conserved cyclin-regulatory role across tumor types.","evidence":"siRNA/shRNA knockdown, qRT-PCR, western blot, colony formation, and cell cycle analysis in NSCLC cells","pmids":["35587057"],"confidence":"Low","gaps":["No ChIP or Co-IP, so direct promoter occupancy not shown","Correlation only between knockdown and target expression"]},{"year":2023,"claim":"Revealed an enhancer-level mechanism in which BAP18 interacts with SMARCA1/BPTF to drive CTCF recruitment, chromatin accessibility, eRNA transcription, and enhancer-promoter looping.","evidence":"Co-IP, ChIP, GRO-seq, ATAC-seq, reporter assay, and knockdown at ERα enhancers","pmids":["36828916"],"confidence":"High","gaps":["How BAP18 selects specific enhancers not defined","Direct vs indirect CTCF dependence unresolved"]},{"year":2023,"claim":"Showed BAP18 coactivates PPARα via the NuA4/TIP60 complex and H4 acetylation, demonstrating it partners with an acetyltransferase complex and acts in lipid metabolism.","evidence":"Co-IP, ChIP, shRNA knockdown, reporter assay, and proliferation assay in hepatocellular carcinoma cells","pmids":["38042310"],"confidence":"Medium","gaps":["Direct BAP18-TIP60 contact surface unknown","Single lab"]},{"year":2025,"claim":"Connected BAP18 to Wnt/β-catenin signaling by showing it recruits ACTL6A and PAF1 to potentiate β-catenin-mediated transcription.","evidence":"Co-IP, reporter assay, RNA-seq, shRNA knockdown, and xenograft in NSCLC cells","pmids":["40818609"],"confidence":"Medium","gaps":["Direct vs scaffolded interactions within the complex not dissected","Single lab"]},{"year":2025,"claim":"Established that BAP18 can act as an AR corepressor by recruiting the SIN3A/HDAC subcomplex, demonstrating its transcriptional output is context-dependent rather than uniformly activating.","evidence":"Co-IP, ChIP, shRNA knockdown, and western blot in AR-positive triple-negative breast cancer cells","pmids":["41163225"],"confidence":"Medium","gaps":["Determinants that switch BAP18 between coactivator and corepressor states unknown","Single lab"]},{"year":null,"claim":"How BAP18 chooses between activating (MLL1/COMPASS, NuA4/TIP60, BPTF) and repressive (SIN3A/HDAC) complexes at a given locus, and the structural basis of its H3K4me3 reading, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of the H3K4me3-binding module","Context signals that determine complex selection unknown","Whether reader activity is required for corepressor recruitment untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,2,6,8]},{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[0,1,2]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,4,7]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,2,4]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[0,1,2]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,2,6]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[0,2,4]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,7]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[1,9]}],"complexes":["MLL1/COMPASS-like complex","NuA4/TIP60 complex","SIN3A/HDAC complex"],"partners":["AR","ESR1","PPARA","SMARCA1","BPTF","ACTL6A","PAF1","CTNNB1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8IXM2","full_name":"BPTF-associated chromatin complex component 1","aliases":["BPTF-associated protein of 18 kDa","Chromatin complexes subunit BAP18"],"length_aa":172,"mass_kda":17.9,"function":"Component of chromatin complexes such as the MLL1/MLL and NURF complexes","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q8IXM2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/BACC1","classification":"Not Classified","n_dependent_lines":306,"n_total_lines":1208,"dependency_fraction":0.2533112582781457},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SMARCA5","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/BACC1","total_profiled":1310},"omim":[{"mim_id":"617215","title":"BPTF-ASSOCIATED CHROMATIN COMPLEX COMPONENT 1; BACC1","url":"https://www.omim.org/entry/617215"}],"hpa":{"profiled":true,"resolved_as":"C17ORF49","reliability":"Uncertain","locations":[{"location":"Nucleoplasm","reliability":"Uncertain"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/C17ORF49"},"hgnc":{"alias_symbol":["MGC49942","BAP18","HEPIS"],"prev_symbol":["C17orf49"]},"alphafold":{"accession":"Q8IXM2","domains":[{"cath_id":"1.20.5","chopping":"2-30","consensus_level":"medium","plddt":92.1752,"start":2,"end":30},{"cath_id":"1.20.5","chopping":"43-90","consensus_level":"medium","plddt":84.986,"start":43,"end":90}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IXM2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IXM2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IXM2-F1-predicted_aligned_error_v6.png","plddt_mean":69.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=BACC1","jax_strain_url":"https://www.jax.org/strain/search?query=BACC1"},"sequence":{"accession":"Q8IXM2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8IXM2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8IXM2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IXM2"}},"corpus_meta":[{"pmid":"27226492","id":"PMC_27226492","title":"BAP18 coactivates androgen receptor action and promotes prostate cancer progression.","date":"2016","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/27226492","citation_count":30,"is_preprint":false},{"pmid":"32113162","id":"PMC_32113162","title":"BAP18 is involved in upregulation of CCND1/2 transcription to promote cell growth in oral squamous cell carcinoma.","date":"2020","source":"EBioMedicine","url":"https://pubmed.ncbi.nlm.nih.gov/32113162","citation_count":15,"is_preprint":false},{"pmid":"32986841","id":"PMC_32986841","title":"An H3K4me3 reader, BAP18 as an adaptor of COMPASS-like core subunits co-activates ERα action and associates with the sensitivity of antiestrogen in breast cancer.","date":"2020","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/32986841","citation_count":15,"is_preprint":false},{"pmid":"35484101","id":"PMC_35484101","title":"Chromatin complexes subunit BAP18 promotes triple-negative breast cancer progression through transcriptional activation of oncogene S100A9.","date":"2022","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/35484101","citation_count":14,"is_preprint":false},{"pmid":"36828916","id":"PMC_36828916","title":"BAP18 facilitates CTCF-mediated chromatin accessible to regulate enhancer activity in breast cancer.","date":"2023","source":"Cell death and differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/36828916","citation_count":14,"is_preprint":false},{"pmid":"33662476","id":"PMC_33662476","title":"The function of BAP18 on modulation of androgen receptor action in luteinized granulosa cells from normal weight women with and without PCOS.","date":"2021","source":"Molecular and cellular endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/33662476","citation_count":9,"is_preprint":false},{"pmid":"35587057","id":"PMC_35587057","title":"BAP18 induces growth of non-small-cell lung carcinoma through upregulating transcriptional level of CCND1/2.","date":"2022","source":"European review for medical and pharmacological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/35587057","citation_count":4,"is_preprint":false},{"pmid":"38042310","id":"PMC_38042310","title":"BAP18 acting as a novel peroxisome proliferator-activated receptor α co-regulator contributes to hepatocellular carcinoma progression.","date":"2023","source":"Biochimica et biophysica acta. Molecular basis of disease","url":"https://pubmed.ncbi.nlm.nih.gov/38042310","citation_count":1,"is_preprint":false},{"pmid":"40818609","id":"PMC_40818609","title":"The chromatin remodeling factor BAP18 promotes non-small cell lung cancer progression via the recruitment of β-catenin with the transcriptional coactivator complex ACTL6A-PAF1.","date":"2025","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/40818609","citation_count":0,"is_preprint":false},{"pmid":"41163225","id":"PMC_41163225","title":"BAP18, as a corepressor of AR together with the SIN3A/HDAC complex, promotes AR-positive triple-negative breast cancer progression.","date":"2025","source":"Cell & bioscience","url":"https://pubmed.ncbi.nlm.nih.gov/41163225","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7135,"output_tokens":2578,"usd":0.030038,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9819,"output_tokens":3458,"usd":0.067772,"stage2_stop_reason":"end_turn"},"total_usd":0.09781,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2016,\n      \"finding\": \"BAP18 acts as a coactivator of androgen receptor (AR) in both Drosophila and mammalian cells; it facilitates recruitment of the MLL1 subcomplex and AR to androgen-response elements (AREs) of AR target genes, increasing histone H3K4 trimethylation and H4K16 acetylation. BAP18 knockdown attenuates prostate cancer cell growth and xenograft tumor growth.\",\n      \"method\": \"Co-immunoprecipitation, ChIP assay, luciferase reporter assay, siRNA/shRNA knockdown, xenograft mouse model, Drosophila experimental system\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, ChIP, reporter assay, and in vivo xenograft across multiple systems and cell lines, replicated in subsequent studies\",\n      \"pmids\": [\"27226492\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"BAP18 functions as an H3K4me3 reader; it is recruited to promoter regions of CCND1 and CCND2 in oral squamous cell carcinoma cells, facilitating recruitment of MLL1 complex core subunits to increase H3K4me3 levels and activate transcription, thereby promoting G1-S phase transition and cell growth.\",\n      \"method\": \"ChIP assay, qPCR, western blot, lentiviral shRNA knockdown, colony formation, xenograft tumor experiment\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and functional knockdown with cell cycle phenotype, single lab with two orthogonal methods\",\n      \"pmids\": [\"32113162\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"BAP18 acts as a co-activator of ERα in breast cancer cells; it is recruited to promoter regions of estrogen-induced genes and facilitates recruitment of COMPASS-like core subunits, accompanied by enrichment of H3K4me3, in an E2-dependent manner. BAP18 promotes cell growth and modulates antiestrogen sensitivity.\",\n      \"method\": \"ChIP-seq, Co-IP, ChIP assay, shRNA knockdown, luciferase reporter assay\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — ChIP-seq plus Co-IP plus functional knockdown with multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"32986841\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"BAP18 is recruited to the H3K4me3-marked promoter of S100A9 in triple-negative breast cancer cells, enhancing its promoter activity and transcription. Knockdown of BAP18 suppresses xenograft tumor growth, an effect partially rescued by S100A9 re-expression, placing S100A9 downstream of BAP18.\",\n      \"method\": \"ChIP assay, luciferase reporter assay, shRNA knockdown, rescue experiment (S100A9 re-expression), xenograft mouse model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis rescue experiment plus ChIP and in vivo data, single lab\",\n      \"pmids\": [\"35484101\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"BAP18 interacts with SMARCA1/BPTF and is required for CTCF recruitment to ERα-enriched enhancers; it facilitates chromatin accessibility within enhancer regions, promotes enhancer RNA transcription, and enhances enhancer-promoter looping. BAP18 depletion increases sensitivity to anti-estrogen and anti-enhancer treatment.\",\n      \"method\": \"Co-IP, ChIP assay, GRO-seq, ATAC-seq (chromatin accessibility), shRNA knockdown, luciferase reporter assay\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Co-IP, ChIP, GRO-seq, chromatin accessibility) in a single rigorous study demonstrating direct interaction and functional consequence\",\n      \"pmids\": [\"36828916\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"BAP18 interacts with androgen receptor (AR) and enhances AR-mediated transactivation in luteinized granulosa cells; BAP18 and AR co-recruit to AREs of CYP19A1 and FSHR promoters. BAP18 also interacts with Sp1 and co-recruits to the AR gene promoter to activate AR transcription. BAP18 knockdown decreases CYP19A1 expression and impairs androgen-to-estrogen conversion.\",\n      \"method\": \"Co-IP, ChIP assay, siRNA knockdown, qPCR, western blot\",\n      \"journal\": \"Molecular and cellular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and ChIP with functional knockdown, single lab, two orthogonal methods\",\n      \"pmids\": [\"33662476\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"BAP18 co-activates PPARα-mediated transactivation in hepatocellular carcinoma cells and facilitates recruitment of the NuA4/TIP60 complex, thereby increasing histone H4 acetylation at SCD1 loci. BAP18 promotes HCC cell proliferation and lipid accumulation.\",\n      \"method\": \"Co-IP, ChIP assay, shRNA knockdown, luciferase reporter assay, cell proliferation assay\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular basis of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and ChIP with functional readouts, single lab\",\n      \"pmids\": [\"38042310\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"BAP18 recruits ACTL6A and PAF1 to Wnt target gene promoters, enhancing β-catenin-mediated transcription in NSCLC cells. Co-immunoprecipitation confirmed interaction between BAP18, β-catenin, ACTL6A, and PAF1; luciferase reporter assays showed increased β-catenin transcriptional activity. BAP18 knockdown inhibited NSCLC cell proliferation, migration, and xenograft tumor growth.\",\n      \"method\": \"Co-immunoprecipitation, luciferase reporter assay, RNA sequencing, shRNA knockdown, xenograft mouse model, immunohistochemistry\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, reporter assay, and in vivo data, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"40818609\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In AR-positive triple-negative breast cancer cells, BAP18 acts as a transcriptional corepressor of AR by associating with AR and the SIN3A/HDAC subcomplex. BAP18 facilitates SIN3A/HDAC recruitment to AREs in promoters of P21 and PTEN, reducing histone H4 acetylation at those sites and suppressing their expression.\",\n      \"method\": \"Co-immunoprecipitation, ChIP assay, shRNA knockdown, western blot\",\n      \"journal\": \"Cell & bioscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and ChIP with functional knockdown demonstrating corepressor activity, single lab\",\n      \"pmids\": [\"41163225\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"BAP18 knockdown in NSCLC cell lines (A549, H1299) reduces transcriptional levels of CCND1 and CCND2, delays G1-to-S phase transition, and weakens NSCLC cell growth, indicating BAP18 regulates CCND1/2 transcription to promote cell cycle progression.\",\n      \"method\": \"siRNA/lentiviral shRNA knockdown, qRT-PCR, western blot, colony formation assay, cell cycle analysis\",\n      \"journal\": \"European review for medical and pharmacological sciences\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single method category (no ChIP or Co-IP reported), observational correlation between knockdown and target gene expression\",\n      \"pmids\": [\"35587057\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"BAP18 (BACC1/C17orf49) is a chromatin-associated H3K4me3 reader that functions as a transcriptional co-regulator—acting as a coactivator for AR, ERα, and PPARα, or as a corepressor for AR depending on cellular context—by bridging nuclear receptors with chromatin-modifying complexes (MLL1/COMPASS-like, NuA4/TIP60, SIN3A/HDAC) and chromatin remodeling factors (SMARCA1/BPTF), thereby modulating histone H3K4me3, H4K16ac, or H4ac levels at target gene promoters and enhancers to control transcription of genes including CCND1/2, CYP19A1, S100A9, and Wnt target genes through a complex involving ACTL6A and PAF1.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"BAP18 (BACC1/C17orf49) is a chromatin-associated H3K4me3 reader that operates as a context-dependent transcriptional co-regulator, bridging sequence-specific nuclear receptors and transcription factors to histone-modifying and chromatin-remodeling machineries at target promoters and enhancers [#0, #2]. As a coactivator, BAP18 is recruited to androgen-response elements and estrogen-induced gene promoters where it facilitates recruitment of the MLL1/COMPASS-like complex and AR or ERα, increasing H3K4me3 and H4K16 acetylation to drive transcription and cancer cell growth [#0, #2]. Its reader activity targets it to H3K4me3-marked promoters of growth and effector genes including CCND1/CCND2, S100A9, and CYP19A1, coupling chromatin engagement to G1-S progression and tumor growth [#1, #3, #5]. BAP18 diversifies its mechanism across complexes and pathways: it recruits the NuA4/TIP60 complex to boost H4 acetylation during PPARα-mediated lipogenic transcription [#6], partners with SMARCA1/BPTF to enable CTCF recruitment, enhancer accessibility, eRNA transcription, and enhancer-promoter looping at ERα enhancers [#4], and recruits ACTL6A and PAF1 to potentiate β-catenin-driven Wnt target transcription [#7]. In an opposing role, BAP18 can act as an AR corepressor by recruiting the SIN3A/HDAC subcomplex to AREs of P21 and PTEN, reducing local H4 acetylation and silencing these genes [#8], establishing that BAP18 toggles between activating and repressive outputs depending on the associated complex and cellular context.\",\n  \"teleology\": [\n    {\n      \"year\": 2016,\n      \"claim\": \"Established BAP18's core function as an AR coactivator that physically links the receptor to a histone methyltransferase complex, defining its mechanism of activating chromatin modification.\",\n      \"evidence\": \"Co-IP, ChIP, luciferase reporter, knockdown, and xenograft across Drosophila and mammalian prostate cancer systems\",\n      \"pmids\": [\"27226492\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the structural basis of H3K4me3 recognition\", \"Generality beyond AR not yet tested\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Showed BAP18 acts as an H3K4me3 reader that recruits MLL1 core subunits to cyclin gene promoters, connecting its chromatin-reading activity to cell cycle control.\",\n      \"evidence\": \"ChIP, qPCR, western blot, shRNA knockdown, and xenograft in oral squamous cell carcinoma cells\",\n      \"pmids\": [\"32113162\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct H3K4me3 binding affinity/domain not characterized\", \"Single tumor type\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Extended BAP18 coactivation beyond AR to ERα, showing E2-dependent recruitment of COMPASS-like subunits and a role in antiestrogen sensitivity.\",\n      \"evidence\": \"ChIP-seq, Co-IP, ChIP, reporter assay, and knockdown in breast cancer cells\",\n      \"pmids\": [\"32986841\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genome-wide selectivity of BAP18 recruitment not fully resolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrated BAP18 cooperates with AR and Sp1 to activate steroidogenic genes, broadening its role beyond cancer to normal endocrine (granulosa cell) physiology.\",\n      \"evidence\": \"Co-IP, ChIP, siRNA knockdown, qPCR, and western blot in luteinized granulosa cells\",\n      \"pmids\": [\"33662476\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological reproductive phenotype in vivo not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified S100A9 as a functional downstream effector of BAP18 in triple-negative breast cancer via epistasis rescue, linking BAP18 chromatin activity to a specific oncogenic target.\",\n      \"evidence\": \"ChIP, reporter assay, shRNA knockdown, S100A9 rescue, and xenograft\",\n      \"pmids\": [\"35484101\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Only partial rescue, other targets contribute\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Reinforced BAP18 control of CCND1/2 transcription and G1-S transition in NSCLC, supporting a conserved cyclin-regulatory role across tumor types.\",\n      \"evidence\": \"siRNA/shRNA knockdown, qRT-PCR, western blot, colony formation, and cell cycle analysis in NSCLC cells\",\n      \"pmids\": [\"35587057\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No ChIP or Co-IP, so direct promoter occupancy not shown\", \"Correlation only between knockdown and target expression\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed an enhancer-level mechanism in which BAP18 interacts with SMARCA1/BPTF to drive CTCF recruitment, chromatin accessibility, eRNA transcription, and enhancer-promoter looping.\",\n      \"evidence\": \"Co-IP, ChIP, GRO-seq, ATAC-seq, reporter assay, and knockdown at ERα enhancers\",\n      \"pmids\": [\"36828916\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How BAP18 selects specific enhancers not defined\", \"Direct vs indirect CTCF dependence unresolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showed BAP18 coactivates PPARα via the NuA4/TIP60 complex and H4 acetylation, demonstrating it partners with an acetyltransferase complex and acts in lipid metabolism.\",\n      \"evidence\": \"Co-IP, ChIP, shRNA knockdown, reporter assay, and proliferation assay in hepatocellular carcinoma cells\",\n      \"pmids\": [\"38042310\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct BAP18-TIP60 contact surface unknown\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Connected BAP18 to Wnt/β-catenin signaling by showing it recruits ACTL6A and PAF1 to potentiate β-catenin-mediated transcription.\",\n      \"evidence\": \"Co-IP, reporter assay, RNA-seq, shRNA knockdown, and xenograft in NSCLC cells\",\n      \"pmids\": [\"40818609\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs scaffolded interactions within the complex not dissected\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Established that BAP18 can act as an AR corepressor by recruiting the SIN3A/HDAC subcomplex, demonstrating its transcriptional output is context-dependent rather than uniformly activating.\",\n      \"evidence\": \"Co-IP, ChIP, shRNA knockdown, and western blot in AR-positive triple-negative breast cancer cells\",\n      \"pmids\": [\"41163225\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Determinants that switch BAP18 between coactivator and corepressor states unknown\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How BAP18 chooses between activating (MLL1/COMPASS, NuA4/TIP60, BPTF) and repressive (SIN3A/HDAC) complexes at a given locus, and the structural basis of its H3K4me3 reading, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of the H3K4me3-binding module\", \"Context signals that determine complex selection unknown\", \"Whether reader activity is required for corepressor recruitment untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 2, 6, 8]},\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 4, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 2, 4]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [0, 1, 2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 2, 6]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [0, 2, 4]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 7]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [1, 9]}\n    ],\n    \"complexes\": [\n      \"MLL1/COMPASS-like complex\",\n      \"NuA4/TIP60 complex\",\n      \"SIN3A/HDAC complex\"\n    ],\n    \"partners\": [\n      \"AR\",\n      \"ESR1\",\n      \"PPARA\",\n      \"SMARCA1\",\n      \"BPTF\",\n      \"ACTL6A\",\n      \"PAF1\",\n      \"CTNNB1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}