{"gene":"C8ORF33","run_date":"2026-06-09T22:02:45","timeline":{"discoveries":[{"year":2025,"finding":"C8orf33 is a nuclear protein localized predominantly to the nucleolus and is recruited to DNA double-strand break (DSB) sites in both nuclear and nucleolar regions, where it promotes NHEJ by facilitating 53BP1 recruitment and inhibiting DNA end resection, thereby counteracting BRCA1 and RAD51 (HR factors) recruitment to DSB sites.","method":"Loss-of-function studies (C8orf33 knockdown), live-cell imaging/localization experiments, and recruitment assays for 53BP1, BRCA1, and RAD51 at DSB sites","journal":"Cell death & disease","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal functional assays with multiple orthogonal readouts (localization, factor recruitment, end resection) in a single rigorous study","pmids":["41249114"],"is_preprint":false},{"year":2025,"finding":"C8orf33 mechanistically antagonizes chromatin association of KAT8 acetyltransferase at DSB sites, leading to reduced H4K16 acetylation (H4K16ac); loss of C8orf33 enhances KAT8 chromatin binding, increases H4K16ac levels, promotes HR factor recruitment, and suppresses NHEJ factor accumulation at DSB sites.","method":"Chromatin profiling analysis (ChIP-based), loss-of-function (C8orf33 knockdown) with measurement of KAT8 binding and H4K16ac levels at DSB sites","journal":"Cell death & disease","confidence":"High","confidence_rationale":"Tier 2 / Strong — chromatin profiling combined with genetic loss-of-function and multiple orthogonal readouts in a single rigorous study","pmids":["41249114"],"is_preprint":false},{"year":2025,"finding":"Loss of C8orf33 causes genomic instability evidenced by accelerated loss of ribosomal DNA repeats and increased cell death, consistent with its role in directing DSB repair toward NHEJ and suppressing aberrant HR.","method":"C8orf33 knockdown with measurement of rDNA repeat stability and cell viability/death assays","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO/KD with defined cellular phenotype, single lab, single study","pmids":["41249114"],"is_preprint":false},{"year":2026,"finding":"C8orf33 knockdown in HCC cell lines (Huh7) reduced proliferation, migration, tumorigenic capacity, and increased apoptosis, and was accompanied by reduced mRNA and protein levels of MIF and its receptor components (CD74, CXCR4, CD44); xenografts from C8orf33-silenced cells showed lower MIF-axis component expression and reduced infiltration of CD163/CD206-positive macrophages.","method":"In vitro loss-of-function (siRNA/shRNA knockdown), in vivo subcutaneous xenograft assays, western blot/qPCR for MIF-axis components, IHC for macrophage markers","journal":"Discover oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD with multiple orthogonal phenotypic readouts (proliferation, migration, apoptosis, in vivo xenograft, molecular markers), single lab","pmids":["41965457"],"is_preprint":false}],"current_model":"C8orf33 is a nucleolar/nuclear protein that directs DNA double-strand break repair toward NHEJ by promoting 53BP1 recruitment and antagonizing KAT8-mediated H4K16 acetylation at DSB sites, thereby suppressing homologous recombination factors BRCA1 and RAD51; additionally, in hepatocellular carcinoma cells, C8orf33 supports proliferation, migration, and tumorigenic capacity, at least in part through regulation of the MIF–CD74/CXCR4/CD44 signaling axis."},"narrative":{"mechanistic_narrative":"C8orf33 is a nuclear, predominantly nucleolar protein that functions as a determinant of DNA double-strand break (DSB) repair pathway choice, biasing repair toward non-homologous end joining (NHEJ) [PMID:41249114]. Recruited to DSB sites in both nuclear and nucleolar chromatin, it facilitates 53BP1 accumulation and inhibits DNA end resection, thereby counteracting recruitment of the homologous recombination factors BRCA1 and RAD51 [PMID:41249114]. Mechanistically, C8orf33 antagonizes chromatin association of the KAT8 acetyltransferase at break sites, lowering H4K16 acetylation; its loss enhances KAT8 binding and H4K16ac, shifting the balance toward HR factor recruitment and away from NHEJ [PMID:41249114]. Consistent with this repair role, depletion destabilizes ribosomal DNA repeats and increases cell death, indicating a contribution to genome integrity [PMID:41249114]. In hepatocellular carcinoma cells, C8orf33 supports proliferation, migration, and tumorigenicity while restraining apoptosis, in part through regulation of MIF and its receptor components CD74, CXCR4, and CD44 and associated tumor macrophage infiltration [PMID:41965457].","teleology":[{"year":2025,"claim":"Established that C8orf33 is a nucleolar/nuclear factor that actively governs DSB repair pathway choice, answering whether this uncharacterized ORF has a defined chromatin function.","evidence":"C8orf33 knockdown with live-cell localization and recruitment assays for 53BP1, BRCA1, and RAD51 at DSB sites","pmids":["41249114"],"confidence":"High","gaps":["Direct molecular partners mediating 53BP1 facilitation are not defined","How C8orf33 is recruited to DSB sites is unknown","No structural basis for its activity"]},{"year":2025,"claim":"Defined the chromatin-level mechanism by which C8orf33 enforces NHEJ — antagonizing KAT8 binding and H4K16 acetylation at breaks — answering how it tilts the resection balance.","evidence":"ChIP-based chromatin profiling plus loss-of-function measurement of KAT8 binding and H4K16ac at DSB sites","pmids":["41249114"],"confidence":"High","gaps":["Whether C8orf33 binds KAT8 directly or acts through an intermediary is unresolved","No reconstitution of the antagonism in vitro","Stoichiometry and kinetics of KAT8 displacement unknown"]},{"year":2025,"claim":"Linked the repair function to a cellular consequence, showing C8orf33 loss causes rDNA instability and cell death and thereby matters for genome maintenance.","evidence":"C8orf33 knockdown with rDNA repeat stability and viability/death assays","pmids":["41249114"],"confidence":"Medium","gaps":["Single study and single lab","Whether rDNA loss is a direct consequence of aberrant HR or a secondary effect is not established"]},{"year":2026,"claim":"Extended C8orf33 to a tumor-promoting role in hepatocellular carcinoma, connecting it to MIF–CD74/CXCR4/CD44 signaling and the tumor immune microenvironment.","evidence":"siRNA/shRNA knockdown in Huh7, xenograft assays, western blot/qPCR for MIF-axis components, IHC for macrophage markers","pmids":["41965457"],"confidence":"Medium","gaps":["Single lab, correlative link between C8orf33 and MIF-axis regulation","Mechanism by which C8orf33 controls MIF/receptor expression is unknown","Relationship between the DSB-repair function and the HCC phenotype is not addressed"]},{"year":null,"claim":"How C8orf33 is recruited to DSBs, its direct binding partners, and whether its DNA-repair role mechanistically underlies its tumor-promoting effects remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No identified direct protein interactor or recruitment determinant","No structural or biochemical characterization","DSB-repair function and HCC/MIF-axis phenotype not mechanistically connected"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1]}],"localization":[{"term_id":"GO:0005730","term_label":"nucleolus","supporting_discovery_ids":[0]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[0,1]}],"complexes":[],"partners":["KAT8","53BP1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9H7E9","full_name":"UPF0488 protein C8orf33","aliases":[],"length_aa":229,"mass_kda":25.0,"function":"","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q9H7E9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/C8ORF33"},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000182307","cell_line_id":"CID000391","localizations":[{"compartment":"cytoplasmic","grade":3},{"compartment":"nucleolus_gc","grade":3},{"compartment":"nucleoplasm","grade":2}],"interactors":[{"gene":"CHMP7","stoichiometry":0.2},{"gene":"NPM1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000391","total_profiled":1310},"omim":[],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Nucleoplasm","reliability":"Uncertain"},{"location":"Plasma membrane","reliability":"Uncertain"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/C8ORF33"},"hgnc":{"alias_symbol":["FLJ20989"],"prev_symbol":[]},"alphafold":{"accession":"Q9H7E9","domains":[{"cath_id":"-","chopping":"105-188","consensus_level":"high","plddt":95.0761,"start":105,"end":188}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H7E9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H7E9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H7E9-F1-predicted_aligned_error_v6.png","plddt_mean":71.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=C8ORF33","jax_strain_url":"https://www.jax.org/strain/search?query=C8ORF33"},"sequence":{"accession":"Q9H7E9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9H7E9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9H7E9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H7E9"}},"corpus_meta":[{"pmid":"35091678","id":"PMC_35091678","title":"An mRNA expression-based signature for oncogene-induced replication-stress.","date":"2022","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/35091678","citation_count":38,"is_preprint":false},{"pmid":"29123978","id":"PMC_29123978","title":"Deep sequencing and comprehensive expression analysis identifies several molecules potentially related to human poorly differentiated hepatocellular carcinoma.","date":"2017","source":"FEBS open bio","url":"https://pubmed.ncbi.nlm.nih.gov/29123978","citation_count":18,"is_preprint":false},{"pmid":"37672187","id":"PMC_37672187","title":"Identifying Genetic Signatures Associated with Oncogene-Induced Replication Stress in Osteosarcoma and Screening for Potential Targeted Drugs.","date":"2023","source":"Biochemical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/37672187","citation_count":9,"is_preprint":false},{"pmid":"18479593","id":"PMC_18479593","title":"[Differentially expressed genes between upward and downward progressing types of nasopharyngeal carcinoma].","date":"2008","source":"Ai zheng = Aizheng = Chinese journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/18479593","citation_count":4,"is_preprint":false},{"pmid":"41249114","id":"PMC_41249114","title":"C8orf33 dictates DNA double-strand break repair choice by modulating KAT8-mediated H4K16 acetylation.","date":"2025","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/41249114","citation_count":1,"is_preprint":false},{"pmid":"41965457","id":"PMC_41965457","title":"Characterization and regulatory mechanism evaluation of C8orf33 in hepatocellular carcinoma through multiomics profiling.","date":"2026","source":"Discover oncology","url":"https://pubmed.ncbi.nlm.nih.gov/41965457","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":5826,"output_tokens":1119,"usd":0.017132,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7698,"output_tokens":1999,"usd":0.044233,"stage2_stop_reason":"end_turn"},"total_usd":0.061365,"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\": 2025,\n      \"finding\": \"C8orf33 is a nuclear protein localized predominantly to the nucleolus and is recruited to DNA double-strand break (DSB) sites in both nuclear and nucleolar regions, where it promotes NHEJ by facilitating 53BP1 recruitment and inhibiting DNA end resection, thereby counteracting BRCA1 and RAD51 (HR factors) recruitment to DSB sites.\",\n      \"method\": \"Loss-of-function studies (C8orf33 knockdown), live-cell imaging/localization experiments, and recruitment assays for 53BP1, BRCA1, and RAD51 at DSB sites\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal functional assays with multiple orthogonal readouts (localization, factor recruitment, end resection) in a single rigorous study\",\n      \"pmids\": [\"41249114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"C8orf33 mechanistically antagonizes chromatin association of KAT8 acetyltransferase at DSB sites, leading to reduced H4K16 acetylation (H4K16ac); loss of C8orf33 enhances KAT8 chromatin binding, increases H4K16ac levels, promotes HR factor recruitment, and suppresses NHEJ factor accumulation at DSB sites.\",\n      \"method\": \"Chromatin profiling analysis (ChIP-based), loss-of-function (C8orf33 knockdown) with measurement of KAT8 binding and H4K16ac levels at DSB sites\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — chromatin profiling combined with genetic loss-of-function and multiple orthogonal readouts in a single rigorous study\",\n      \"pmids\": [\"41249114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Loss of C8orf33 causes genomic instability evidenced by accelerated loss of ribosomal DNA repeats and increased cell death, consistent with its role in directing DSB repair toward NHEJ and suppressing aberrant HR.\",\n      \"method\": \"C8orf33 knockdown with measurement of rDNA repeat stability and cell viability/death assays\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO/KD with defined cellular phenotype, single lab, single study\",\n      \"pmids\": [\"41249114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"C8orf33 knockdown in HCC cell lines (Huh7) reduced proliferation, migration, tumorigenic capacity, and increased apoptosis, and was accompanied by reduced mRNA and protein levels of MIF and its receptor components (CD74, CXCR4, CD44); xenografts from C8orf33-silenced cells showed lower MIF-axis component expression and reduced infiltration of CD163/CD206-positive macrophages.\",\n      \"method\": \"In vitro loss-of-function (siRNA/shRNA knockdown), in vivo subcutaneous xenograft assays, western blot/qPCR for MIF-axis components, IHC for macrophage markers\",\n      \"journal\": \"Discover oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD with multiple orthogonal phenotypic readouts (proliferation, migration, apoptosis, in vivo xenograft, molecular markers), single lab\",\n      \"pmids\": [\"41965457\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"C8orf33 is a nucleolar/nuclear protein that directs DNA double-strand break repair toward NHEJ by promoting 53BP1 recruitment and antagonizing KAT8-mediated H4K16 acetylation at DSB sites, thereby suppressing homologous recombination factors BRCA1 and RAD51; additionally, in hepatocellular carcinoma cells, C8orf33 supports proliferation, migration, and tumorigenic capacity, at least in part through regulation of the MIF–CD74/CXCR4/CD44 signaling axis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"C8orf33 is a nuclear, predominantly nucleolar protein that functions as a determinant of DNA double-strand break (DSB) repair pathway choice, biasing repair toward non-homologous end joining (NHEJ) [#0]. Recruited to DSB sites in both nuclear and nucleolar chromatin, it facilitates 53BP1 accumulation and inhibits DNA end resection, thereby counteracting recruitment of the homologous recombination factors BRCA1 and RAD51 [#0]. Mechanistically, C8orf33 antagonizes chromatin association of the KAT8 acetyltransferase at break sites, lowering H4K16 acetylation; its loss enhances KAT8 binding and H4K16ac, shifting the balance toward HR factor recruitment and away from NHEJ [#1]. Consistent with this repair role, depletion destabilizes ribosomal DNA repeats and increases cell death, indicating a contribution to genome integrity [#2]. In hepatocellular carcinoma cells, C8orf33 supports proliferation, migration, and tumorigenicity while restraining apoptosis, in part through regulation of MIF and its receptor components CD74, CXCR4, and CD44 and associated tumor macrophage infiltration [#3].\",\n  \"teleology\": [\n    {\n      \"year\": 2025,\n      \"claim\": \"Established that C8orf33 is a nucleolar/nuclear factor that actively governs DSB repair pathway choice, answering whether this uncharacterized ORF has a defined chromatin function.\",\n      \"evidence\": \"C8orf33 knockdown with live-cell localization and recruitment assays for 53BP1, BRCA1, and RAD51 at DSB sites\",\n      \"pmids\": [\n        \"41249114\"\n      ],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Direct molecular partners mediating 53BP1 facilitation are not defined\",\n        \"How C8orf33 is recruited to DSB sites is unknown\",\n        \"No structural basis for its activity\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defined the chromatin-level mechanism by which C8orf33 enforces NHEJ — antagonizing KAT8 binding and H4K16 acetylation at breaks — answering how it tilts the resection balance.\",\n      \"evidence\": \"ChIP-based chromatin profiling plus loss-of-function measurement of KAT8 binding and H4K16ac at DSB sites\",\n      \"pmids\": [\n        \"41249114\"\n      ],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether C8orf33 binds KAT8 directly or acts through an intermediary is unresolved\",\n        \"No reconstitution of the antagonism in vitro\",\n        \"Stoichiometry and kinetics of KAT8 displacement unknown\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Linked the repair function to a cellular consequence, showing C8orf33 loss causes rDNA instability and cell death and thereby matters for genome maintenance.\",\n      \"evidence\": \"C8orf33 knockdown with rDNA repeat stability and viability/death assays\",\n      \"pmids\": [\n        \"41249114\"\n      ],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single study and single lab\",\n        \"Whether rDNA loss is a direct consequence of aberrant HR or a secondary effect is not established\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Extended C8orf33 to a tumor-promoting role in hepatocellular carcinoma, connecting it to MIF–CD74/CXCR4/CD44 signaling and the tumor immune microenvironment.\",\n      \"evidence\": \"siRNA/shRNA knockdown in Huh7, xenograft assays, western blot/qPCR for MIF-axis components, IHC for macrophage markers\",\n      \"pmids\": [\n        \"41965457\"\n      ],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single lab, correlative link between C8orf33 and MIF-axis regulation\",\n        \"Mechanism by which C8orf33 controls MIF/receptor expression is unknown\",\n        \"Relationship between the DSB-repair function and the HCC phenotype is not addressed\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How C8orf33 is recruited to DSBs, its direct binding partners, and whether its DNA-repair role mechanistically underlies its tumor-promoting effects remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No identified direct protein interactor or recruitment determinant\",\n        \"No structural or biochemical characterization\",\n        \"DSB-repair function and HCC/MIF-axis phenotype not mechanistically connected\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\n        \"term_id\": \"GO:0098772\",\n        \"supporting_discovery_ids\": [\n          1\n        ]\n      }\n    ],\n    \"localization\": [\n      {\n        \"term_id\": \"GO:0005730\",\n        \"supporting_discovery_ids\": [\n          0\n        ]\n      },\n      {\n        \"term_id\": \"GO:0005634\",\n        \"supporting_discovery_ids\": [\n          0\n        ]\n      },\n      {\n        \"term_id\": \"GO:0000228\",\n        \"supporting_discovery_ids\": [\n          0,\n          1\n        ]\n      }\n    ],\n    \"pathway\": [\n      {\n        \"term_id\": \"R-HSA-73894\",\n        \"supporting_discovery_ids\": [\n          0,\n          1\n        ]\n      }\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"KAT8\",\n      \"53BP1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":4,"faith_total":5,"faith_pct":80.0}}