{"gene":"POLI","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":2020,"finding":"Human DNA polymerase iota (POLI) possesses both polymerase (TLS) activity and deoxyribose phosphate (dRP) lyase activity. Missense variants K209Q, K228I, and Q386R showed 4- to 53-fold decreases in specificity constants (kcat/Km) for dCTP insertion opposite G and 8-oxo-7,8-dihydroguanine. A CRISPR/Cas9 POLI knockout in HEK293 cells conferred higher H2O2 sensitivity; variants retaining polymerase activity (R126C, K345E) rescued this sensitivity, while variants lacking polymerase activity (K209Q, K228I, Q386R) did not, establishing that TLS-related polymerase function—rather than dRP lyase activity—is the primary determinant of POLI's protective role against oxidative stress.","method":"In vitro kinetic assays with recombinant protein variants, dRP lyase assays, CRISPR/Cas9 knockout, exogenous expression rescue in HEK293 cells","journal":"Chemical research in toxicology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with mutagenesis plus cell-based rescue assay, single lab with multiple orthogonal methods","pmids":["32635723"],"is_preprint":false},{"year":2023,"finding":"POLI stabilizes RAD51 protein by competitively binding RAD51 and blocking the interaction between RAD51 and the E3 ubiquitin ligase XIAP, thereby preventing XIAP-mediated ubiquitination and degradation of RAD51. POLI-deficient ESCC cells showed impaired homologous recombination (HR) but not NHEJ, and loss of POLI activated GAS signaling. This stabilization mechanism underlies POLI-mediated radioresistance.","method":"Co-immunoprecipitation (competitive binding assay), ubiquitination assay, HR/NHEJ reporter assays, siRNA/shRNA knockdown, γH2AX foci and comet tail assays after ionizing radiation","journal":"Cell death discovery","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP and functional assays in a single lab, two orthogonal methods (binding + HR repair assay)","pmids":["37558683"],"is_preprint":false},{"year":2003,"finding":"Mouse Poli (the Par2 candidate gene) encodes an error-prone DNA polymerase that preferentially incorporates G or T opposite template T in vitro. BALB/cByJ-specific polymorphisms (21 SNPs causing 7 amino acid substitutions) in Poli correlate with reduced Kras2-mutated lung tumor frequency, suggesting Poli's misincorporation activity generates the A-to-G/T transversions at codon 61 that initiate urethane-induced lung tumors.","method":"In vitro polymerase activity characterization, cDNA sequencing, chimeric mouse tumor analysis, sequencing of Kras2 mutations in tumors","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro polymerase assay combined with genetic analysis in chimeric mice and sequencing; single lab","pmids":["12700672"],"is_preprint":false},{"year":2025,"finding":"POLI interacts with DCLRE1A during the repair of Cas12a-induced DNA breaks within CAG repeat tracts, and this interaction leads to the formation of inverted repeats at the break site via template switching mechanisms, as opposed to pure repeat contractions generated by the DCLRE1A–SLX4 interaction.","method":"CRISPRi screen, Co-immunoprecipitation/interaction assays, sequencing of editing outcomes, Cas12a-fusion protein experiments","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — preprint, single lab, interaction inferred from screen and co-IP; mechanistic detail is partial","pmids":["bio_10.1101_2025.11.18.689026"],"is_preprint":true}],"current_model":"Human POLI (DNA polymerase iota) is a Y-family translesion synthesis polymerase with both TLS polymerase and dRP lyase activities; its TLS polymerase function is the primary mechanism protecting cells from oxidative DNA damage, it stabilizes RAD51 by competitively blocking XIAP-mediated ubiquitination to promote homologous recombination and radioresistance, and it interacts with DCLRE1A during repeat repair to promote template switching."},"narrative":{"mechanistic_narrative":"POLI encodes DNA polymerase iota, an error-prone translesion synthesis (TLS) polymerase that protects cells from genotoxic stress through both catalytic and protein-stabilizing functions [PMID:32635723, PMID:37558683]. The recombinant enzyme carries both TLS polymerase and deoxyribose phosphate (dRP) lyase activities, but structure-function analysis of missense variants establishes that it is the TLS polymerase activity—not dRP lyase activity—that determines POLI's protective role against oxidative DNA damage: variants retaining polymerase activity rescue H2O2 sensitivity of POLI-knockout cells while catalytically dead variants do not [PMID:32635723]. Beyond direct lesion bypass, POLI stabilizes the recombinase RAD51 by competitively binding RAD51 and blocking its interaction with the E3 ubiquitin ligase XIAP, thereby preventing RAD51 ubiquitination and degradation; through this mechanism POLI supports homologous recombination and confers radioresistance [PMID:37558683].","teleology":[{"year":2003,"claim":"Established that the Poli gene product is an error-prone polymerase whose misincorporation activity can be mutagenic in vivo, linking its biochemical infidelity to tumor initiation.","evidence":"In vitro polymerase activity characterization plus genetic correlation of Poli polymorphisms with Kras2 mutation frequency in chimeric mouse lung tumors","pmids":["12700672"],"confidence":"Medium","gaps":["Correlation between polymorphisms and tumor frequency does not prove a direct causal mechanism","Mouse ortholog; human POLI not assayed here","No structural basis for the misincorporation preference"]},{"year":2020,"claim":"Resolved which of POLI's two enzymatic activities underlies its protective function, showing the TLS polymerase activity—not dRP lyase activity—guards cells against oxidative damage.","evidence":"In vitro kinetic and dRP lyase assays on recombinant variants combined with CRISPR/Cas9 knockout and variant rescue of H2O2 sensitivity in HEK293 cells","pmids":["32635723"],"confidence":"High","gaps":["Physiological lesions bypassed in vivo not fully cataloged beyond 8-oxoG","Role of dRP lyase activity, if any, remains undefined","Single cell line tested"]},{"year":2023,"claim":"Revealed a non-catalytic role for POLI in homologous recombination by showing it stabilizes RAD51 through competitive blockade of XIAP-mediated ubiquitination, explaining POLI-dependent radioresistance.","evidence":"Reciprocal Co-IP/competitive binding, ubiquitination assays, HR/NHEJ reporters, and DNA damage foci/comet assays after irradiation in ESCC cells with knockdown","pmids":["37558683"],"confidence":"Medium","gaps":["Whether RAD51 stabilization requires POLI catalytic activity is unresolved","Single cancer cell context (ESCC)","Direct competition with XIAP not confirmed structurally"]},{"year":2025,"claim":"Implicated POLI in repeat-tract repair, showing its interaction with DCLRE1A channels break repair toward inverted-repeat formation via template switching.","evidence":"CRISPRi screen, Co-IP, and sequencing of Cas12a-induced editing outcomes at CAG repeats (preprint)","pmids":["bio_10.1101_2025.11.18.689026"],"confidence":"Low","gaps":["Preprint, single lab, not peer reviewed","Interaction inferred from screen and co-IP without reciprocal/structural validation","Mechanism of template switching only partially defined"]},{"year":null,"claim":"How POLI's catalytic TLS function and its non-catalytic protein-stabilizing/scaffolding roles are coordinated within the same cell remains unknown.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model integrating polymerase, dRP lyase, RAD51-binding, and DCLRE1A-binding functions","Regulation of POLI recruitment to different repair pathways undefined","Physiological substrate spectrum incompletely mapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140097","term_label":"catalytic activity, acting on DNA","supporting_discovery_ids":[0,2]},{"term_id":"GO:0016829","term_label":"lyase activity","supporting_discovery_ids":[0]},{"term_id":"GO:0140313","term_label":"molecular sequestering activity","supporting_discovery_ids":[1]}],"localization":[],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[0,1]}],"complexes":[],"partners":["RAD51","XIAP","DCLRE1A"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9UNA4","full_name":"DNA polymerase iota","aliases":["Eta2","RAD30 homolog B"],"length_aa":740,"mass_kda":83.0,"function":"Error-prone DNA polymerase specifically involved in DNA repair (PubMed:11013228, PubMed:11387224). Plays an important role in translesion synthesis, where the normal high-fidelity DNA polymerases cannot proceed and DNA synthesis stalls (PubMed:11013228, PubMed:11387224, PubMed:14630940, PubMed:15199127, PubMed:20388628). Favors Hoogsteen base-pairing in the active site (PubMed:15254543). Inserts the correct base with high-fidelity opposite an adenosine template (PubMed:15254543). Exhibits low fidelity and efficiency opposite a thymidine template, where it will preferentially insert guanosine (PubMed:11013228). May play a role in hypermutation of immunoglobulin genes (PubMed:12410315). Forms a Schiff base with 5'-deoxyribose phosphate at abasic sites, but may not have lyase activity (PubMed:11251121, PubMed:14630940)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q9UNA4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/POLI","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/POLI","total_profiled":1310},"omim":[{"mim_id":"619705","title":"IMMUNODEFICIENCY 93 AND HYPERTROPHIC CARDIOMYOPATHY; IMD93","url":"https://www.omim.org/entry/619705"},{"mim_id":"618982","title":"IMMUNODEFICIENCY 72 WITH AUTOINFLAMMATION AND LYMPHOPROLIFERATION; IMD72","url":"https://www.omim.org/entry/618982"},{"mim_id":"618048","title":"PROTEASOME-ASSOCIATED AUTOINFLAMMATORY SYNDROME 2; PRAAS2","url":"https://www.omim.org/entry/618048"},{"mim_id":"616414","title":"AUTOINFLAMMATION AND AUTOIMMUNITY, SYSTEMIC, WITH IMMUNE DYSREGULATION 1; AIAISD1","url":"https://www.omim.org/entry/616414"},{"mim_id":"615577","title":"IMMUNODEFICIENCY, COMMON VARIABLE, 10; CVID10","url":"https://www.omim.org/entry/615577"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nuclear speckles","reliability":"Supported"},{"location":"Cytoplasmic bodies","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/POLI"},"hgnc":{"alias_symbol":[],"prev_symbol":["RAD3OB","RAD30B"]},"alphafold":{"accession":"Q9UNA4","domains":[{"cath_id":"3.30.70.270","chopping":"56-258","consensus_level":"medium","plddt":97.2989,"start":56,"end":258},{"cath_id":"1.10.150.20","chopping":"259-316","consensus_level":"medium","plddt":96.8891,"start":259,"end":316},{"cath_id":"3.30.1490.100","chopping":"327-441","consensus_level":"high","plddt":92.2357,"start":327,"end":441}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UNA4","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UNA4-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UNA4-F1-predicted_aligned_error_v6.png","plddt_mean":70.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=POLI","jax_strain_url":"https://www.jax.org/strain/search?query=POLI"},"sequence":{"accession":"Q9UNA4","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UNA4.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UNA4/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UNA4"}},"corpus_meta":[{"pmid":"15609317","id":"PMC_15609317","title":"Association of amino acid substitution polymorphisms in DNA repair genes TP53, POLI, REV1 and LIG4 with lung cancer risk.","date":"2005","source":"International journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/15609317","citation_count":137,"is_preprint":false},{"pmid":"11889052","id":"PMC_11889052","title":"Mutations in polI but not mutSLH destabilize Haemophilus influenzae tetranucleotide repeats.","date":"2002","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/11889052","citation_count":44,"is_preprint":false},{"pmid":"26225536","id":"PMC_26225536","title":"PoLi: A Virtual Screening Pipeline Based on Template Pocket and Ligand Similarity.","date":"2015","source":"Journal of chemical information and modeling","url":"https://pubmed.ncbi.nlm.nih.gov/26225536","citation_count":29,"is_preprint":false},{"pmid":"12700672","id":"PMC_12700672","title":"Analysis of lung tumorigenesis in chimeric mice indicates the Pulmonary adenoma resistance 2 (Par2) locus to operate in the tumor-initiation stage in a cell-autonomous manner: detection of polymorphisms in the Poli gene as a candidate for Par2.","date":"2003","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/12700672","citation_count":27,"is_preprint":false},{"pmid":"26097541","id":"PMC_26097541","title":"Elevated DNA polymerase iota (Poli) is involved in the acquisition of aggressive phenotypes of human esophageal squamous cell cancer.","date":"2015","source":"International journal of clinical and experimental pathology","url":"https://pubmed.ncbi.nlm.nih.gov/26097541","citation_count":17,"is_preprint":false},{"pmid":"32274883","id":"PMC_32274883","title":"Diversity and bioactivity of fungi associated with the marine sea cucumber Holothuria poli: disclosing the strains potential for biomedical applications.","date":"2020","source":"Journal of applied microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/32274883","citation_count":16,"is_preprint":false},{"pmid":"15653640","id":"PMC_15653640","title":"Destabilization of tetranucleotide repeats in Haemophilus influenzae mutants lacking RnaseHI or the Klenow domain of PolI.","date":"2005","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/15653640","citation_count":16,"is_preprint":false},{"pmid":"6085006","id":"PMC_6085006","title":"Characterization of a crude selective PolI transcription system from Tetrahymena pyriformis.","date":"1984","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/6085006","citation_count":16,"is_preprint":false},{"pmid":"31699041","id":"PMC_31699041","title":"Organ transcriptomes of the lucinid clam Loripes orbiculatus (Poli, 1791) provide insights into their specialised roles in the biology of a chemosymbiotic bivalve.","date":"2019","source":"BMC genomics","url":"https://pubmed.ncbi.nlm.nih.gov/31699041","citation_count":16,"is_preprint":false},{"pmid":"37558683","id":"PMC_37558683","title":"Polymerase iota (POLI) confers radioresistance of esophageal squamous cell carcinoma by regulating RAD51 stability and facilitating homologous recombination.","date":"2023","source":"Cell death discovery","url":"https://pubmed.ncbi.nlm.nih.gov/37558683","citation_count":7,"is_preprint":false},{"pmid":"32635723","id":"PMC_32635723","title":"Three Human Pol ι Variants with Impaired Polymerase Activity Fail to Rescue H2O2 Sensitivity in POLI-Deficient Cells.","date":"2020","source":"Chemical research in toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/32635723","citation_count":3,"is_preprint":false},{"pmid":"39335462","id":"PMC_39335462","title":"Toxicological Assessment of Biodegradable Poli-ε-Caprolactone Polymer Composite Materials Containing Hydroxyapatite, Bioglass, and Chitosan as Potential Biomaterials for Bone Regeneration Scaffolds.","date":"2024","source":"Biomedicines","url":"https://pubmed.ncbi.nlm.nih.gov/39335462","citation_count":3,"is_preprint":false},{"pmid":"40112579","id":"PMC_40112579","title":"DNA-poli: Design and development of a digital platform for family communication support and predictive genetic counseling on inherited diseases.","date":"2025","source":"Patient education and counseling","url":"https://pubmed.ncbi.nlm.nih.gov/40112579","citation_count":2,"is_preprint":false},{"pmid":"34459328","id":"PMC_34459328","title":"Semi-Purified Saponins of Holothuria poli Associated Antiproliferation in Tumor Cell Lines.","date":"2021","source":"Nutrition and cancer","url":"https://pubmed.ncbi.nlm.nih.gov/34459328","citation_count":1,"is_preprint":false},{"pmid":"19651477","id":"PMC_19651477","title":"Schizophrenia, brain disease and meta-analyses: integrating the pieces and testing Fusar-Poli's hypothesis.","date":"2009","source":"Medical hypotheses","url":"https://pubmed.ncbi.nlm.nih.gov/19651477","citation_count":1,"is_preprint":false},{"pmid":"9246790","id":"PMC_9246790","title":"PolI-driven integrative expression vectors for yeast.","date":"1997","source":"Journal of biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/9246790","citation_count":1,"is_preprint":false},{"pmid":"36761442","id":"PMC_36761442","title":"Molecular analysis of Lepidopleuruscajetanus (Poli, 1791) (Polyplacophora, Leptochitonidae) from the Mediterranean and near Atlantic.","date":"2022","source":"ZooKeys","url":"https://pubmed.ncbi.nlm.nih.gov/36761442","citation_count":1,"is_preprint":false},{"pmid":"41210372","id":"PMC_41210372","title":"Evaluation of DNA-poli: Study protocol of a randomized controlled trial to assess a digital platform for family cascade genetic testing and predictive genetic counseling.","date":"2025","source":"Genetics in medicine 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breaks","date":"2025-11-18","source":"bioRxiv","url":"https://doi.org/10.1101/2025.11.18.689026","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.09.24.25336565","title":"Intravenous Thrombolysis for Acute Central Retinal Artery Occlusion: Protocol For a Systematic Review and Individual Participant Data Meta-Analysis of Randomized Controlled Trials","date":"2025-09-25","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.24.25336565","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.08.13.25333645","title":"Knowledge, Attitudes, and Barriers to Oncofertility Services Among Cancer Patients Requiring Chemoradiotherapy: A Systematic Review","date":"2025-08-15","source":"bioRxiv","url":"https://doi.org/10.1101/2025.08.13.25333645","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13517,"output_tokens":1292,"usd":0.029965,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7925,"output_tokens":1839,"usd":0.0428,"stage2_stop_reason":"end_turn"},"total_usd":0.072765,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2020,\n      \"finding\": \"Human DNA polymerase iota (POLI) possesses both polymerase (TLS) activity and deoxyribose phosphate (dRP) lyase activity. Missense variants K209Q, K228I, and Q386R showed 4- to 53-fold decreases in specificity constants (kcat/Km) for dCTP insertion opposite G and 8-oxo-7,8-dihydroguanine. A CRISPR/Cas9 POLI knockout in HEK293 cells conferred higher H2O2 sensitivity; variants retaining polymerase activity (R126C, K345E) rescued this sensitivity, while variants lacking polymerase activity (K209Q, K228I, Q386R) did not, establishing that TLS-related polymerase function—rather than dRP lyase activity—is the primary determinant of POLI's protective role against oxidative stress.\",\n      \"method\": \"In vitro kinetic assays with recombinant protein variants, dRP lyase assays, CRISPR/Cas9 knockout, exogenous expression rescue in HEK293 cells\",\n      \"journal\": \"Chemical research in toxicology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with mutagenesis plus cell-based rescue assay, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"32635723\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"POLI stabilizes RAD51 protein by competitively binding RAD51 and blocking the interaction between RAD51 and the E3 ubiquitin ligase XIAP, thereby preventing XIAP-mediated ubiquitination and degradation of RAD51. POLI-deficient ESCC cells showed impaired homologous recombination (HR) but not NHEJ, and loss of POLI activated GAS signaling. This stabilization mechanism underlies POLI-mediated radioresistance.\",\n      \"method\": \"Co-immunoprecipitation (competitive binding assay), ubiquitination assay, HR/NHEJ reporter assays, siRNA/shRNA knockdown, γH2AX foci and comet tail assays after ionizing radiation\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP and functional assays in a single lab, two orthogonal methods (binding + HR repair assay)\",\n      \"pmids\": [\"37558683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Mouse Poli (the Par2 candidate gene) encodes an error-prone DNA polymerase that preferentially incorporates G or T opposite template T in vitro. BALB/cByJ-specific polymorphisms (21 SNPs causing 7 amino acid substitutions) in Poli correlate with reduced Kras2-mutated lung tumor frequency, suggesting Poli's misincorporation activity generates the A-to-G/T transversions at codon 61 that initiate urethane-induced lung tumors.\",\n      \"method\": \"In vitro polymerase activity characterization, cDNA sequencing, chimeric mouse tumor analysis, sequencing of Kras2 mutations in tumors\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro polymerase assay combined with genetic analysis in chimeric mice and sequencing; single lab\",\n      \"pmids\": [\"12700672\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"POLI interacts with DCLRE1A during the repair of Cas12a-induced DNA breaks within CAG repeat tracts, and this interaction leads to the formation of inverted repeats at the break site via template switching mechanisms, as opposed to pure repeat contractions generated by the DCLRE1A–SLX4 interaction.\",\n      \"method\": \"CRISPRi screen, Co-immunoprecipitation/interaction assays, sequencing of editing outcomes, Cas12a-fusion protein experiments\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — preprint, single lab, interaction inferred from screen and co-IP; mechanistic detail is partial\",\n      \"pmids\": [\"bio_10.1101_2025.11.18.689026\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"Human POLI (DNA polymerase iota) is a Y-family translesion synthesis polymerase with both TLS polymerase and dRP lyase activities; its TLS polymerase function is the primary mechanism protecting cells from oxidative DNA damage, it stabilizes RAD51 by competitively blocking XIAP-mediated ubiquitination to promote homologous recombination and radioresistance, and it interacts with DCLRE1A during repeat repair to promote template switching.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"POLI encodes DNA polymerase iota, an error-prone translesion synthesis (TLS) polymerase that protects cells from genotoxic stress through both catalytic and protein-stabilizing functions [#0, #1]. The recombinant enzyme carries both TLS polymerase and deoxyribose phosphate (dRP) lyase activities, but structure-function analysis of missense variants establishes that it is the TLS polymerase activity—not dRP lyase activity—that determines POLI's protective role against oxidative DNA damage: variants retaining polymerase activity rescue H2O2 sensitivity of POLI-knockout cells while catalytically dead variants do not [#0]. Beyond direct lesion bypass, POLI stabilizes the recombinase RAD51 by competitively binding RAD51 and blocking its interaction with the E3 ubiquitin ligase XIAP, thereby preventing RAD51 ubiquitination and degradation; through this mechanism POLI supports homologous recombination and confers radioresistance [#1].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Established that the Poli gene product is an error-prone polymerase whose misincorporation activity can be mutagenic in vivo, linking its biochemical infidelity to tumor initiation.\",\n      \"evidence\": \"In vitro polymerase activity characterization plus genetic correlation of Poli polymorphisms with Kras2 mutation frequency in chimeric mouse lung tumors\",\n      \"pmids\": [\"12700672\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Correlation between polymorphisms and tumor frequency does not prove a direct causal mechanism\", \"Mouse ortholog; human POLI not assayed here\", \"No structural basis for the misincorporation preference\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Resolved which of POLI's two enzymatic activities underlies its protective function, showing the TLS polymerase activity—not dRP lyase activity—guards cells against oxidative damage.\",\n      \"evidence\": \"In vitro kinetic and dRP lyase assays on recombinant variants combined with CRISPR/Cas9 knockout and variant rescue of H2O2 sensitivity in HEK293 cells\",\n      \"pmids\": [\"32635723\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological lesions bypassed in vivo not fully cataloged beyond 8-oxoG\", \"Role of dRP lyase activity, if any, remains undefined\", \"Single cell line tested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed a non-catalytic role for POLI in homologous recombination by showing it stabilizes RAD51 through competitive blockade of XIAP-mediated ubiquitination, explaining POLI-dependent radioresistance.\",\n      \"evidence\": \"Reciprocal Co-IP/competitive binding, ubiquitination assays, HR/NHEJ reporters, and DNA damage foci/comet assays after irradiation in ESCC cells with knockdown\",\n      \"pmids\": [\"37558683\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether RAD51 stabilization requires POLI catalytic activity is unresolved\", \"Single cancer cell context (ESCC)\", \"Direct competition with XIAP not confirmed structurally\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Implicated POLI in repeat-tract repair, showing its interaction with DCLRE1A channels break repair toward inverted-repeat formation via template switching.\",\n      \"evidence\": \"CRISPRi screen, Co-IP, and sequencing of Cas12a-induced editing outcomes at CAG repeats (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.11.18.689026\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Preprint, single lab, not peer reviewed\", \"Interaction inferred from screen and co-IP without reciprocal/structural validation\", \"Mechanism of template switching only partially defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How POLI's catalytic TLS function and its non-catalytic protein-stabilizing/scaffolding roles are coordinated within the same cell remains unknown.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model integrating polymerase, dRP lyase, RAD51-binding, and DCLRE1A-binding functions\", \"Regulation of POLI recruitment to different repair pathways undefined\", \"Physiological substrate spectrum incompletely mapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140097\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0016829\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0140313\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"RAD51\", \"XIAP\", \"DCLRE1A\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":3,"faith_total":3,"faith_pct":100.0}}