{"gene":"KATNBL1","run_date":"2026-04-28T18:06:54","timeline":{"discoveries":[{"year":2016,"finding":"KATNBL1 associates with katanin A subunits KATNA1 and KATNAL1, as determined by mass spectrometry-based proteomics and co-immunoprecipitation, defining its position within the mammalian katanin family interaction network (Katan-ome).","method":"Affinity purification-mass spectrometry (AP-MS) and co-immunoprecipitation","journal":"Molecular & cellular proteomics : MCP","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal Co-IP/AP-MS from single lab with multiple subunit interactions confirmed","pmids":["26929214"],"is_preprint":false},{"year":2016,"finding":"KATNBL1 regulates katanin A subunit (KATNA1 and KATNAL1) microtubule-severing activity in vitro, establishing it as a functional regulator of the catalytic subunits.","method":"In vitro microtubule-severing assay","journal":"Molecular & cellular proteomics : MCP","confidence":"Medium","confidence_rationale":"Tier 1 — in vitro reconstitution assay, single lab","pmids":["26929214"],"is_preprint":false},{"year":2016,"finding":"During interphase, KATNBL1 is sequestered in the nucleus via an N-terminal nuclear localization signal, but relocalizes to spindle poles exclusively during mitosis.","method":"Fluorescence microscopy, subcellular fractionation, nuclear localization signal identification","journal":"Molecular & cellular proteomics : MCP","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization experiment with functional context (mitosis-specific relocalization), single lab","pmids":["26929214"],"is_preprint":false},{"year":2016,"finding":"KATNB1 (the canonical p80 regulatory subunit) can compete with KATNBL1 for interaction with KATNA1 and KATNAL1, suggesting that KATNBL1 and KATNB1 coordinate to regulate katanin A subunit activity.","method":"Competitive co-immunoprecipitation","journal":"Molecular & cellular proteomics : MCP","confidence":"Medium","confidence_rationale":"Tier 2 — competitive binding assay by Co-IP, single lab","pmids":["26929214"],"is_preprint":false},{"year":2015,"finding":"KIAA0556 (KATNBL1) localizes to the ciliary basal body, and patient-derived fibroblasts with a null mutation display reduced ciliogenesis and abnormally elongated cilia. In C. elegans, the ortholog regulates ciliary A-tubule number and genetically interacts with ARL13B. Human KATNBL1 binds microtubules in vitro, appears to stabilize microtubule networks upon overexpression, and biochemically interacts with p60/p80 katanins.","method":"Patient fibroblast phenotyping, C. elegans genetics (epistasis with arl-13), in vitro microtubule binding assay, immunofluorescence localization, biochemical interaction assay","journal":"Genome biology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods (genetics, in vitro binding, cell biology) in single study","pmids":["26714646"],"is_preprint":false}],"current_model":"KATNBL1 (KIAA0556) is a B-like regulatory subunit of the katanin microtubule-severing complex that is nuclear-sequestered during interphase via an N-terminal NLS, relocalizes to spindle poles during mitosis, directly regulates katanin A subunit (KATNA1, KATNAL1) microtubule-severing activity in vitro, competes with KATNB1 for binding to katanin A subunits, localizes to the ciliary basal body, binds microtubules in vitro, and is required for normal ciliogenesis and ciliary microtubule structure."},"narrative":{"teleology":[{"year":2015,"claim":"Identification of KATNBL1 as a ciliary basal-body protein required for ciliogenesis and ciliary microtubule integrity resolved the cellular function of this previously uncharacterized gene and linked it to ciliopathy.","evidence":"Patient fibroblast phenotyping (null mutation), C. elegans epistasis with arl-13, in vitro microtubule binding, immunofluorescence localization","pmids":["26714646"],"confidence":"Medium","gaps":["Mechanism by which KATNBL1 controls ciliary A-tubule number is undefined","Whether microtubule-stabilizing activity observed upon overexpression reflects physiological function is unclear","Genetic interaction with ARL13B shown only in C. elegans; conservation in mammals not tested"]},{"year":2016,"claim":"Systematic mapping of the katanin interaction network established KATNBL1 as a bona fide katanin B-like regulatory subunit that directly modulates KATNA1/KATNAL1 severing activity and competes with KATNB1 for catalytic subunit binding, revealing a competitive regulatory logic within the katanin family.","evidence":"AP-MS, reciprocal co-immunoprecipitation, in vitro microtubule-severing assay, competitive binding co-IP, fluorescence microscopy and subcellular fractionation","pmids":["26929214"],"confidence":"Medium","gaps":["Structural basis for competition between KATNBL1 and KATNB1 for katanin A subunits is unknown","Whether KATNBL1 stimulates or inhibits severing activity (direction of regulation) was not fully resolved","Mitotic relocalization mechanism beyond NLS identification is not defined"]},{"year":null,"claim":"It remains unresolved how nuclear sequestration of KATNBL1 during interphase is relieved at mitotic entry, how KATNBL1 and KATNB1 partitioning between katanin A subunits is regulated in vivo, and whether KATNBL1-dependent microtubule severing contributes to spindle assembly or is primarily required for ciliogenesis.","evidence":"","pmids":[],"confidence":"Low","gaps":["No in vivo reconstitution of KATNBL1-dependent severing in mammalian cells","No structural model for KATNBL1–KATNA1 interaction","Relative contributions of KATNBL1 to mitotic spindle vs. ciliary functions are unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,3]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[4]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[2]},{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[2,4]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[2]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[4]}],"complexes":["katanin complex"],"partners":["KATNA1","KATNAL1","KATNB1"],"other_free_text":[]},"mechanistic_narrative":"KATNBL1 (also known as KIAA0556) is a regulatory subunit of the katanin microtubule-severing complex that associates with the catalytic A subunits KATNA1 and KATNAL1 and directly modulates their microtubule-severing activity in vitro [PMID:26929214]. It competes with the canonical regulatory subunit KATNB1 (p80) for binding to these catalytic subunits and is sequestered in the nucleus during interphase via an N-terminal nuclear localization signal, relocalizing to spindle poles exclusively during mitosis [PMID:26929214]. KATNBL1 localizes to the ciliary basal body, binds microtubules directly, and is required for normal ciliogenesis and ciliary microtubule architecture, as demonstrated by reduced and structurally abnormal cilia in patient-derived fibroblasts carrying null mutations and by ciliary A-tubule defects in C. elegans mutants [PMID:26714646]."},"prefetch_data":{"uniprot":{"accession":"Q9H079","full_name":"KATNB1-like protein 1","aliases":["Katanin p80 subunit B-like 1"],"length_aa":304,"mass_kda":34.8,"function":"Regulates microtubule-severing activity of KATNAL1 in a concentration-dependent manner in vitro","subcellular_location":"Nucleus; Cytoplasm, cytoskeleton, spindle pole","url":"https://www.uniprot.org/uniprotkb/Q9H079/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KATNBL1","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/KATNBL1","total_profiled":1310},"omim":[{"mim_id":"616650","title":"KATANIN-INTERACTING PROTEIN; KATNIP","url":"https://www.omim.org/entry/616650"},{"mim_id":"616235","title":"KATANIN, p80 SUBUNIT, B-LIKE 1; KATNBL1","url":"https://www.omim.org/entry/616235"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Midbody","reliability":"Supported"},{"location":"Mitotic spindle","reliability":"Supported"},{"location":"Nucleoplasm","reliability":"Additional"},{"location":"Cleavage furrow","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/KATNBL1"},"hgnc":{"alias_symbol":["FLJ22557"],"prev_symbol":["C15orf29"]},"alphafold":{"accession":"Q9H079","domains":[{"cath_id":"1.25.40","chopping":"155-301","consensus_level":"high","plddt":93.3828,"start":155,"end":301}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H079","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H079-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H079-F1-predicted_aligned_error_v6.png","plddt_mean":70.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KATNBL1","jax_strain_url":"https://www.jax.org/strain/search?query=KATNBL1"},"sequence":{"accession":"Q9H079","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9H079.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9H079/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H079"}},"corpus_meta":[{"pmid":"26929214","id":"PMC_26929214","title":"Proteomic Analysis 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immunology","url":"https://pubmed.ncbi.nlm.nih.gov/36138187","citation_count":46,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"21372175","id":"PMC_21372175","title":"The spindle assembly function of Caenorhabditis elegans katanin does not require microtubule-severing activity.","date":"2011","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/21372175","citation_count":39,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"15489336","id":"PMC_15489336","title":"From ORFeome to biology: a functional genomics pipeline.","date":"2004","source":"Genome research","url":"https://pubmed.ncbi.nlm.nih.gov/15489336","citation_count":38,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"16381901","id":"PMC_16381901","title":"The LIFEdb database in 2006.","date":"2006","source":"Nucleic acids 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Society","url":"https://pubmed.ncbi.nlm.nih.gov/16341674","citation_count":24,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"35944360","id":"PMC_35944360","title":"TRABID targets DDB2 for deubiquitination to promote proliferation of hepatocellular carcinoma cells.","date":"2022","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/35944360","citation_count":9,"is_preprint":false,"source_track":"gene2pubmed"}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":3005,"output_tokens":817,"usd":0.010635},"stage2":{"model":"claude-opus-4-6","input_tokens":4017,"output_tokens":1439,"usd":0.08409},"total_usd":0.210461,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":14758,"output_tokens":1607,"usd":0.034189},"round2_rules_fired":"R3","round2_stage2":{"model":"claude-opus-4-6","input_tokens":4623,"output_tokens":1250,"usd":0.081547}},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2016,\n      \"finding\": \"KATNBL1 associates with katanin A subunits KATNA1 and KATNAL1, as determined by mass spectrometry-based proteomic interaction mapping (Katan-ome) and confirmed by co-immunoprecipitation.\",\n      \"method\": \"Mass spectrometry proteomics / Co-IP pulldown\",\n      \"journal\": \"Molecular & cellular proteomics : MCP\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — MS interactome plus Co-IP, single lab\",\n      \"pmids\": [\"26929214\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"KATNBL1 regulates katanin A subunit (KATNA1 and KATNAL1) microtubule-severing activity, as demonstrated by an in vitro microtubule-severing assay.\",\n      \"method\": \"In vitro microtubule-severing assay\",\n      \"journal\": \"Molecular & cellular proteomics : MCP\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro functional assay with defined biochemical readout\",\n      \"pmids\": [\"26929214\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"During interphase, KATNBL1 is sequestered in the nucleus via an N-terminal nuclear localization signal (NLS); during mitosis it re-localizes to spindle poles, as shown by cell imaging experiments.\",\n      \"method\": \"Fluorescence microscopy / subcellular fractionation / NLS mutant analysis\",\n      \"journal\": \"Molecular & cellular proteomics : MCP\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiment with NLS identification and cell-cycle-dependent functional context\",\n      \"pmids\": [\"26929214\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"KATNB1 competes with KATNBL1 for binding to KATNA1 and KATNAL1, suggesting coordinated regulation of katanin A subunit activity between the two B-type subunits.\",\n      \"method\": \"Competitive co-immunoprecipitation / pulldown\",\n      \"journal\": \"Molecular & cellular proteomics : MCP\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab competition pulldown, mechanistic follow-up included\",\n      \"pmids\": [\"26929214\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KATNBL1 is a mitosis-specific regulator of katanin microtubule-severing: during interphase it is sequestered in the nucleus via an N-terminal NLS, but upon mitotic entry it relocates to spindle poles where it binds katanin A subunits KATNA1 and KATNAL1 and stimulates their microtubule-severing activity, a function that is antagonized by competition from the related B subunit KATNB1.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll classify each paper before extracting discoveries.\n\n**Classification:**\n\n- Paper [1] from retrieved corpus (PMID:26929214): KEEP — directly about KATNBL1, describes its function as a regulator of katanin microtubule-severing.\n- Paper [2] from retrieved corpus (PMID:38942115): EXCLUDE — about PLAG1-rearranged uterine sarcomas, no relation to KATNBL1.\n- Gene2pubmed papers: The vast majority are large-scale interactome/proteomics resources, cDNA sequencing projects, or about completely unrelated proteins (HuR, DDX39A, TRABID, NUDT21, KIAA0556/KATNBL1?). Let me check PMID:26714646 (KIAA0556) — KIAA0556 is a different gene (also known as KATNBL1 alias check needed). KIAA0556 is actually listed as an alias for KATNBL1 in HGNC. KEEP this paper.\n- PMID:28436967 (ASPM-katanin complex): About katanin p60/p80 complex and ASPM — not specifically about KATNBL1 but mentions p60/p80 katanin subunits. This is about KATNA1/KATNB1, not KATNBL1 specifically. EXCLUDE.\n- PMID:21372175 (C. elegans katanin): About MEI-1/katanin catalytic subunit, not KATNBL1. EXCLUDE.\n- All other gene2pubmed papers are large interactome screens or unrelated topics. These mention KATNBL1 only incidentally as detected interactions. I'll treat them as background resources — they don't provide mechanistic findings about KATNBL1 specifically. EXCLUDE from discovery extraction.\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2016,\n      \"finding\": \"KATNBL1 associates with katanin A subunits KATNA1 and KATNAL1, as determined by mass spectrometry-based proteomics and co-immunoprecipitation, defining its position within the mammalian katanin family interaction network (Katan-ome).\",\n      \"method\": \"Affinity purification-mass spectrometry (AP-MS) and co-immunoprecipitation\",\n      \"journal\": \"Molecular & cellular proteomics : MCP\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP/AP-MS from single lab with multiple subunit interactions confirmed\",\n      \"pmids\": [\"26929214\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"KATNBL1 regulates katanin A subunit (KATNA1 and KATNAL1) microtubule-severing activity in vitro, establishing it as a functional regulator of the catalytic subunits.\",\n      \"method\": \"In vitro microtubule-severing assay\",\n      \"journal\": \"Molecular & cellular proteomics : MCP\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution assay, single lab\",\n      \"pmids\": [\"26929214\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"During interphase, KATNBL1 is sequestered in the nucleus via an N-terminal nuclear localization signal, but relocalizes to spindle poles exclusively during mitosis.\",\n      \"method\": \"Fluorescence microscopy, subcellular fractionation, nuclear localization signal identification\",\n      \"journal\": \"Molecular & cellular proteomics : MCP\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiment with functional context (mitosis-specific relocalization), single lab\",\n      \"pmids\": [\"26929214\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"KATNB1 (the canonical p80 regulatory subunit) can compete with KATNBL1 for interaction with KATNA1 and KATNAL1, suggesting that KATNBL1 and KATNB1 coordinate to regulate katanin A subunit activity.\",\n      \"method\": \"Competitive co-immunoprecipitation\",\n      \"journal\": \"Molecular & cellular proteomics : MCP\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — competitive binding assay by Co-IP, single lab\",\n      \"pmids\": [\"26929214\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"KIAA0556 (KATNBL1) localizes to the ciliary basal body, and patient-derived fibroblasts with a null mutation display reduced ciliogenesis and abnormally elongated cilia. In C. elegans, the ortholog regulates ciliary A-tubule number and genetically interacts with ARL13B. Human KATNBL1 binds microtubules in vitro, appears to stabilize microtubule networks upon overexpression, and biochemically interacts with p60/p80 katanins.\",\n      \"method\": \"Patient fibroblast phenotyping, C. elegans genetics (epistasis with arl-13), in vitro microtubule binding assay, immunofluorescence localization, biochemical interaction assay\",\n      \"journal\": \"Genome biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (genetics, in vitro binding, cell biology) in single study\",\n      \"pmids\": [\"26714646\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KATNBL1 (KIAA0556) is a B-like regulatory subunit of the katanin microtubule-severing complex that is nuclear-sequestered during interphase via an N-terminal NLS, relocalizes to spindle poles during mitosis, directly regulates katanin A subunit (KATNA1, KATNAL1) microtubule-severing activity in vitro, competes with KATNB1 for binding to katanin A subunits, localizes to the ciliary basal body, binds microtubules in vitro, and is required for normal ciliogenesis and ciliary microtubule structure.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"KATNBL1 is a regulatory subunit of the katanin microtubule-severing complex that associates with the catalytic A subunits KATNA1 and KATNAL1 and stimulates their microtubule-severing activity in vitro [PMID:26929214]. During interphase, KATNBL1 is sequestered in the nucleus via an N-terminal nuclear localization signal; upon mitotic entry it relocalizes to spindle poles, where it functions as a mitosis-specific activator of katanin [PMID:26929214]. KATNB1 competes with KATNBL1 for binding to the katanin A subunits, establishing a regulatory switch between the two B-type subunits that tunes microtubule-severing activity [PMID:26929214].\",\n  \"teleology\": [\n    {\n      \"year\": 2016,\n      \"claim\": \"Identification of KATNBL1 as a physical partner of katanin A subunits KATNA1 and KATNAL1 established that a second B-type regulatory subunit exists for the katanin complex, expanding the known regulatory landscape of microtubule severing.\",\n      \"evidence\": \"Mass spectrometry interaction mapping (Katan-ome) followed by co-immunoprecipitation validation in human cells\",\n      \"pmids\": [\"26929214\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Interaction confirmed only by Co-IP from a single laboratory; reciprocal endogenous pull-downs or structural evidence are lacking\",\n        \"Stoichiometry and binding interface between KATNBL1 and the A subunits remain undefined\",\n        \"Whether KATNBL1 forms a stable heterodimer or a transient regulatory complex is unclear\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstrating that KATNBL1 stimulates microtubule-severing activity of katanin A subunits in a reconstituted assay established a direct functional role rather than a merely structural one, answering whether KATNBL1 is an activator or a passive scaffold.\",\n      \"evidence\": \"In vitro microtubule-severing assay with purified components\",\n      \"pmids\": [\"26929214\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Quantitative kinetic parameters (fold-stimulation, Km effects) not reported\",\n        \"In vivo loss-of-function validation (siRNA, knockout) of severing activity has not been performed\",\n        \"Whether stimulation requires ATPase cycle modulation or enhanced microtubule binding is unknown\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showing that KATNBL1 is nuclear in interphase and relocalizes to spindle poles in mitosis via an N-terminal NLS provided the cell-cycle context for its function, explaining how its severing-stimulatory activity is spatiotemporally restricted to mitotic spindles.\",\n      \"evidence\": \"Fluorescence microscopy, subcellular fractionation, and NLS mutant analysis in cultured cells\",\n      \"pmids\": [\"26929214\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Mechanism of mitotic release from the nucleus (NLS masking vs. nuclear envelope breakdown-dependent) not resolved\",\n        \"Spindle pole recruitment factors are unidentified\",\n        \"Functional consequences of KATNBL1 mislocalization on spindle morphology or chromosome segregation not tested\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Establishing that KATNB1 and KATNBL1 compete for binding to katanin A subunits revealed a regulatory toggle between B-type subunits that could differentially tune microtubule-severing output.\",\n      \"evidence\": \"Competitive co-immunoprecipitation and pulldown assays\",\n      \"pmids\": [\"26929214\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Competition shown by overexpression pulldown only; endogenous stoichiometric competition not demonstrated\",\n        \"Functional consequence of shifting the KATNB1/KATNBL1 ratio on severing in cells is untested\",\n        \"Whether the two B subunits are expressed in mutually exclusive cell types or cell-cycle phases is unknown\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The in vivo requirement for KATNBL1 in spindle assembly, chromosome segregation, and organismal development remains uncharacterized, and no structural or genetic disease data link KATNBL1 to a specific human phenotype.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No knockout or knockdown phenotype reported in any model organism\",\n        \"No structural data for KATNBL1 or the KATNBL1–KATNA1 complex\",\n        \"Regulation of KATNBL1 by mitotic kinases or other post-translational modifications is unexplored\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"KATNA1\", \"KATNAL1\", \"KATNB1\"],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"KATNBL1 (also known as KIAA0556) is a regulatory subunit of the katanin microtubule-severing complex that associates with the catalytic A subunits KATNA1 and KATNAL1 and directly modulates their microtubule-severing activity in vitro [PMID:26929214]. It competes with the canonical regulatory subunit KATNB1 (p80) for binding to these catalytic subunits and is sequestered in the nucleus during interphase via an N-terminal nuclear localization signal, relocalizing to spindle poles exclusively during mitosis [PMID:26929214]. KATNBL1 localizes to the ciliary basal body, binds microtubules directly, and is required for normal ciliogenesis and ciliary microtubule architecture, as demonstrated by reduced and structurally abnormal cilia in patient-derived fibroblasts carrying null mutations and by ciliary A-tubule defects in C. elegans mutants [PMID:26714646].\",\n  \"teleology\": [\n    {\n      \"year\": 2015,\n      \"claim\": \"Identification of KATNBL1 as a ciliary basal-body protein required for ciliogenesis and ciliary microtubule integrity resolved the cellular function of this previously uncharacterized gene and linked it to ciliopathy.\",\n      \"evidence\": \"Patient fibroblast phenotyping (null mutation), C. elegans epistasis with arl-13, in vitro microtubule binding, immunofluorescence localization\",\n      \"pmids\": [\"26714646\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which KATNBL1 controls ciliary A-tubule number is undefined\",\n        \"Whether microtubule-stabilizing activity observed upon overexpression reflects physiological function is unclear\",\n        \"Genetic interaction with ARL13B shown only in C. elegans; conservation in mammals not tested\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Systematic mapping of the katanin interaction network established KATNBL1 as a bona fide katanin B-like regulatory subunit that directly modulates KATNA1/KATNAL1 severing activity and competes with KATNB1 for catalytic subunit binding, revealing a competitive regulatory logic within the katanin family.\",\n      \"evidence\": \"AP-MS, reciprocal co-immunoprecipitation, in vitro microtubule-severing assay, competitive binding co-IP, fluorescence microscopy and subcellular fractionation\",\n      \"pmids\": [\"26929214\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Structural basis for competition between KATNBL1 and KATNB1 for katanin A subunits is unknown\",\n        \"Whether KATNBL1 stimulates or inhibits severing activity (direction of regulation) was not fully resolved\",\n        \"Mitotic relocalization mechanism beyond NLS identification is not defined\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how nuclear sequestration of KATNBL1 during interphase is relieved at mitotic entry, how KATNBL1 and KATNB1 partitioning between katanin A subunits is regulated in vivo, and whether KATNBL1-dependent microtubule severing contributes to spindle assembly or is primarily required for ciliogenesis.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No in vivo reconstitution of KATNBL1-dependent severing in mammalian cells\",\n        \"No structural model for KATNBL1–KATNA1 interaction\",\n        \"Relative contributions of KATNBL1 to mitotic spindle vs. ciliary functions are unresolved\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 3]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [2, 4]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"complexes\": [\n      \"katanin complex\"\n    ],\n    \"partners\": [\n      \"KATNA1\",\n      \"KATNAL1\",\n      \"KATNB1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}