{"gene":"TERB1","run_date":"2026-04-28T21:42:58","timeline":{"discoveries":[{"year":2014,"finding":"TERB1 forms a heterocomplex with the canonical telomeric protein TRF1 and binds telomere repeat DNA, localizing at telomeres in mouse germ cells during meiotic prophase.","method":"Co-immunoprecipitation, telomere DNA binding assays, mouse knockout","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP and functional KO, replicated by multiple subsequent studies","pmids":["24413433"],"is_preprint":false},{"year":2014,"finding":"TERB1 promotes telomere association with the nuclear envelope and deposition of the SUN-KASH (LINC) complex, which recruits cytoplasmic motor complexes to drive meiotic chromosomal movement.","method":"Mouse Terb1 knockout — abolishes meiotic chromosomal movement; immunofluorescence showing loss of SUN-KASH at telomeres","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined cellular phenotype plus localization data, replicated by subsequent studies","pmids":["24413433"],"is_preprint":false},{"year":2014,"finding":"TERB1 binds and recruits cohesin to telomeres to develop structural rigidity reminiscent of centromeres.","method":"Mouse Terb1 knockout combined with cohesin localization assays","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 — KO with defined molecular phenotype (cohesin loss at telomeres), replicated by domain mapping studies","pmids":["24413433"],"is_preprint":false},{"year":2014,"finding":"CCDC79/TERB1 is a meiosis-specific telomere-associated protein that localizes to telomeres from leptotene to diplotene; its telomere localization does not require telomere-nuclear envelope attachment (persists in SUN1-deficient spermatocytes), but is lost from most telomeres lacking SUN1-connection in SMC1B-deficient spermatocytes.","method":"Immunofluorescence in wild-type, SUN1-KO, and SMC1B-KO spermatocytes","journal":"BMC cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization experiment with genetic controls, single lab","pmids":["24885367"],"is_preprint":false},{"year":2017,"finding":"Crystal structure of the TRF1-binding motif of human TERB1 in complex with the TRFH domain of TRF1 was solved; a point mutation specifically disrupting the TERB1-TRF1 interaction causes male-specific infertility with zygotene-early pachytene arrest and failure of X-Y chromosome pairing.","method":"X-ray crystallography; Terb1 point-mutant knock-in mouse","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 — crystal structure combined with in vivo point-mutant validation","pmids":["29083416"],"is_preprint":false},{"year":2017,"finding":"TERB1 contains a distinct TERB2-binding (T2B) domain that is dispensable for TRF1 interaction but essential for TERB1-TERB2 interaction and subsequent telomere attachment to the nuclear envelope; cohesin recruitment at telomeres is mediated by the MYB-like domain of TERB1, not by TERB2-MAJIN.","method":"Germ-cell-specific TRF1 knockout mouse; domain deletion mapping; mouse knockouts","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — multiple domain-specific KO/KI mice with defined molecular phenotypes","pmids":["29141207"],"is_preprint":false},{"year":2018,"finding":"Crystal structure of the MAJIN-TERB2 complex shows a 2:2 hetero-tetramer that binds strongly to DNA and is tethered through flexible linkers to the inner nuclear membrane and two TERB2-TERB1 (1:1) complexes; during pachytene, TRF1 is displaced from the complex allowing MAJIN-TERB2-TERB1 to directly bind telomeric DNA and form a mature attachment plate.","method":"X-ray crystallography, light scattering, structured illumination microscopy, biochemical DNA binding assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with orthogonal biochemical and imaging validation","pmids":["30559341"],"is_preprint":false},{"year":2019,"finding":"Crystal structures of human TERB1-TERB2 and TERB2-MAJIN subcomplexes were solved; specific disruption of the TERB1-TERB2 or TERB2-MAJIN interaction in mice abolishes telomere attachment to the nuclear envelope and causes aberrant homologous pairing and disordered synapsis.","method":"X-ray crystallography; Terb2 knock-in point mutant mice disrupting defined interfaces","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 — crystal structures plus in vivo interface-specific knock-in mutations","pmids":["30718482"],"is_preprint":false},{"year":2022,"finding":"The TERB1 MYB domain has lost its canonical DNA-binding activity; it is dispensable for telomere localization of TERB1 and the downstream TERB2-MAJIN complex and for homologous pairing, but instead regulates cohesin enrichment, promotes axial element remodeling at the pachytene transition, and suppresses telomere erosion.","method":"Terb1 MYB-domain point-mutant knock-in mice; in vitro DNA binding assays showing loss of activity; cohesin and SC component localization","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro mutagenesis combined with in vivo knock-in mouse with multiple molecular readouts","pmids":["35081355"],"is_preprint":false}],"current_model":"TERB1 is a meiosis-specific telomere protein that acts as a central scaffold: it binds TRF1 (via its TRF1-binding motif, structurally characterized), recruits TERB2-MAJIN through a distinct T2B domain to tether telomeres to the inner nuclear membrane, promotes SUN-KASH (LINC) complex deposition to transmit cytoskeletal forces for chromosome movement, recruits cohesin via its MYB-like domain to confer telomere rigidity, and—after displacing TRF1 at pachytene—allows MAJIN-TERB2-TERB1 to directly bind telomeric DNA and form a mature attachment plate, while the MYB domain also suppresses telomere erosion by regulating cohesin enrichment and axial element remodeling."},"narrative":{"teleology":[{"year":2014,"claim":"Identification of TERB1 as a meiosis-specific telomere protein established the first known dedicated bridge between shelterin (TRF1) and the nuclear envelope/cytoskeletal machinery during meiosis, resolving how telomeres recruit LINC complexes and cohesin for chromosome movement and structural rigidity.","evidence":"Mouse Terb1 knockout with Co-IP, telomere DNA binding assays, and immunofluorescence for SUN–KASH and cohesin localization","pmids":["24413433","24885367"],"confidence":"High","gaps":["Structural basis of the TERB1–TRF1 interaction was unknown","The mechanism by which TERB1 connects to the inner nuclear membrane was not defined","Individual domain contributions to cohesin recruitment versus membrane tethering were not separated"]},{"year":2017,"claim":"Crystal structure of the TERB1–TRF1 interface and domain dissection of TERB1 resolved how a single protein uses separable domains for TRF1 binding, TERB2–MAJIN recruitment (T2B domain), and cohesin recruitment (MYB domain), and showed that disruption of the TRF1 interface alone causes male infertility with zygotene–pachytene arrest.","evidence":"X-ray crystallography of human TERB1 TRF1-binding motif with TRFH domain; Terb1 point-mutant knock-in and germ-cell-specific TRF1 KO mice with domain deletions","pmids":["29083416","29141207"],"confidence":"High","gaps":["Structural basis of the TERB1–TERB2 and TERB2–MAJIN interfaces remained unsolved","The mechanism of TRF1 displacement at pachytene was not explained","How the MYB domain recruits cohesin at a molecular level was unclear"]},{"year":2018,"claim":"Crystal structures of the MAJIN–TERB2 complex and biochemical reconstitution revealed a 2:2 hetero-tetramer that directly binds DNA, establishing that after TRF1 displacement at pachytene, the MAJIN–TERB2–TERB1 complex forms a mature DNA-binding attachment plate anchored to the inner nuclear membrane.","evidence":"X-ray crystallography, light scattering, DNA binding assays, and structured illumination microscopy","pmids":["30559341"],"confidence":"High","gaps":["The trigger and regulation of TRF1 displacement were not defined","The structural basis of the TERB1–TERB2 interface was not yet solved","No reconstitution of the full pentameric TRF1–TERB1–TERB2–MAJIN–DNA assembly was achieved"]},{"year":2019,"claim":"Crystal structures of human TERB1–TERB2 and TERB2–MAJIN subcomplexes, combined with interface-specific knock-in mutations in mice, demonstrated that each pairwise interaction in the TERB1–TERB2–MAJIN chain is independently essential for telomere–nuclear envelope attachment, homologous pairing, and synapsis.","evidence":"X-ray crystallography of both subcomplexes; Terb2 knock-in point mutant mice disrupting defined interfaces","pmids":["30718482"],"confidence":"High","gaps":["How the assembled complex integrates with LINC complex components at a structural level was not resolved","Whether TERB1–TERB2–MAJIN has additional post-translational regulation during prophase progression was unknown"]},{"year":2022,"claim":"Functional characterization of the TERB1 MYB domain revealed it has lost canonical DNA-binding activity and instead serves a non-canonical role in cohesin enrichment, axial element remodeling at pachytene, and suppression of telomere erosion—functions separable from telomere localization and homologous pairing.","evidence":"Terb1 MYB-domain point-mutant knock-in mice with in vitro DNA binding assays and cohesin/SC component localization","pmids":["35081355"],"confidence":"High","gaps":["The direct binding partner through which the MYB domain recruits cohesin has not been identified","How MYB-domain-mediated cohesin enrichment mechanistically suppresses telomere erosion is unknown","Whether the MYB domain functions equivalently in female meiosis is untested"]},{"year":null,"claim":"Key open questions include the molecular trigger for TRF1 displacement at pachytene, the identity of the direct MYB-domain binding partner that mediates cohesin recruitment, the full structural reconstitution of the TRF1–TERB1–TERB2–MAJIN–LINC super-complex, and whether TERB1 functions equivalently in oogenesis.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No molecular trigger identified for TRF1 displacement at pachytene","Direct cohesin-recruiting partner of the MYB domain unknown","Full structural reconstitution of the telomere attachment complex not achieved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1,2,5]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[2,8]}],"localization":[{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[0,3,4]},{"term_id":"GO:0005635","term_label":"nuclear envelope","supporting_discovery_ids":[1,5,6,7]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0,1,4,7]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[0,4]}],"complexes":["MAJIN-TERB2-TERB1","TRF1-TERB1"],"partners":["TRF1","TERB2","MAJIN","SUN1"],"other_free_text":[]},"mechanistic_narrative":"TERB1 is a meiosis-specific telomere scaffold protein that organizes chromosome end attachment to the nuclear envelope and transmits cytoskeletal forces required for homologous chromosome pairing and synapsis during meiotic prophase. TERB1 binds telomeres through interaction with TRF1 via a structurally defined TRF1-binding motif, recruits the TERB2–MAJIN complex through its T2B domain to tether telomeres to the inner nuclear membrane and promote SUN–KASH (LINC) complex deposition for meiotic chromosome movement, and independently recruits cohesin via its MYB-like domain to confer centromere-like structural rigidity at telomeres [PMID:24413433, PMID:29141207]. At pachytene, TRF1 is displaced and the MAJIN–TERB2–TERB1 complex directly binds telomeric DNA to form a mature attachment plate, while the MYB domain—which has lost canonical DNA-binding activity—regulates cohesin enrichment, axial element remodeling, and suppression of telomere erosion [PMID:30559341, PMID:35081355]. Disruption of the TERB1–TRF1 interface causes male-specific infertility with zygotene–pachytene arrest and failure of X–Y chromosome pairing [PMID:29083416]."},"prefetch_data":{"uniprot":{"accession":"Q8NA31","full_name":"Telomere repeats-binding bouquet formation protein 1","aliases":["Coiled-coil domain-containing protein 79"],"length_aa":727,"mass_kda":83.1,"function":"Meiosis-specific telomere-associated protein involved in meiotic telomere attachment to the nucleus inner membrane, a crucial step for homologous pairing and synapsis. Component of the MAJIN-TERB1-TERB2 complex, which promotes telomere cap exchange by mediating attachment of telomeric DNA to the inner nuclear membrane and replacement of the protective cap of telomeric chromosomes: in early meiosis, the MAJIN-TERB1-TERB2 complex associates with telomeric DNA and the shelterin/telosome complex. During prophase, the complex matures and promotes release of the shelterin/telosome complex from telomeric DNA. In the MAJIN-TERB1-TERB2 complex, TERB1 probably mediates association with the shelterin/telosome complex via interaction with TERF1, promoting priming telomeric DNA attachment'. Promotes telomere association with the nuclear envelope and deposition of the SUN-KASH/LINC complex. Also recruits cohesin to telomeres to develop structural rigidity","subcellular_location":"Chromosome, telomere; Nucleus inner membrane","url":"https://www.uniprot.org/uniprotkb/Q8NA31/entry"},"depmap":{"release":"DepMap","has_data":false,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TERB1"},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TERB1","total_profiled":1310},"omim":[{"mim_id":"619646","title":"SPERMATOGENIC FAILURE 60; SPGF60","url":"https://www.omim.org/entry/619646"},{"mim_id":"619645","title":"SPERMATOGENIC FAILURE 59; SPGF59","url":"https://www.omim.org/entry/619645"},{"mim_id":"617332","title":"TELOMERE REPEAT-BINDING BOUQUET FORMATION PROTEIN 1; TERB1","url":"https://www.omim.org/entry/617332"},{"mim_id":"617131","title":"TELOMERE REPEAT-BINDING BOUQUET FORMATION PROTEIN 2; TERB2","url":"https://www.omim.org/entry/617131"},{"mim_id":"617130","title":"MEMBRANE-ANCHORED JUNCTION PROTEIN; MAJIN","url":"https://www.omim.org/entry/617130"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Cell Junctions","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"testis","ntpm":11.7}],"url":"https://www.proteinatlas.org/search/TERB1"},"hgnc":{"alias_symbol":["FLJ35894"],"prev_symbol":["CCDC79"]},"alphafold":{"accession":"Q8NA31","domains":[{"cath_id":"1.25.10.10","chopping":"230-378","consensus_level":"medium","plddt":90.9548,"start":230,"end":378},{"cath_id":"1.10.10.60","chopping":"677-721","consensus_level":"medium","plddt":88.5247,"start":677,"end":721}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NA31","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NA31-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NA31-F1-predicted_aligned_error_v6.png","plddt_mean":71.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TERB1","jax_strain_url":"https://www.jax.org/strain/search?query=TERB1"},"sequence":{"accession":"Q8NA31","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8NA31.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8NA31/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NA31"}},"corpus_meta":[{"pmid":"24413433","id":"PMC_24413433","title":"The TRF1-binding protein TERB1 promotes chromosome movement and telomere rigidity in meiosis.","date":"2014","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/24413433","citation_count":150,"is_preprint":false},{"pmid":"30718482","id":"PMC_30718482","title":"The meiotic TERB1-TERB2-MAJIN complex tethers telomeres to the nuclear envelope.","date":"2019","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/30718482","citation_count":41,"is_preprint":false},{"pmid":"29083416","id":"PMC_29083416","title":"Telomeric TERB1-TRF1 interaction is crucial for male meiosis.","date":"2017","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/29083416","citation_count":41,"is_preprint":false},{"pmid":"33211200","id":"PMC_33211200","title":"Disruption of human meiotic telomere complex genes TERB1, TERB2 and MAJIN in men with non-obstructive azoospermia.","date":"2020","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33211200","citation_count":37,"is_preprint":false},{"pmid":"24885367","id":"PMC_24885367","title":"Mouse CCDC79 (TERB1) is a meiosis-specific telomere associated protein.","date":"2014","source":"BMC cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/24885367","citation_count":33,"is_preprint":false},{"pmid":"30559341","id":"PMC_30559341","title":"Structural basis of meiotic telomere attachment to the nuclear envelope by MAJIN-TERB2-TERB1.","date":"2018","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/30559341","citation_count":32,"is_preprint":false},{"pmid":"29141207","id":"PMC_29141207","title":"Distinct TERB1 Domains Regulate Different Protein Interactions in Meiotic Telomere Movement.","date":"2017","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/29141207","citation_count":30,"is_preprint":false},{"pmid":"32408858","id":"PMC_32408858","title":"The TERB1-TERB2-MAJIN complex of mouse meiotic telomeres dates back to the common ancestor of metazoans.","date":"2020","source":"BMC evolutionary biology","url":"https://pubmed.ncbi.nlm.nih.gov/32408858","citation_count":17,"is_preprint":false},{"pmid":"35081355","id":"PMC_35081355","title":"The TERB1 MYB domain suppresses telomere erosion in meiotic prophase I.","date":"2022","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/35081355","citation_count":10,"is_preprint":false},{"pmid":"38277113","id":"PMC_38277113","title":"A report of two homozygous TERB1 protein-truncating variants in two unrelated women with primary infertility.","date":"2024","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/38277113","citation_count":3,"is_preprint":false},{"pmid":"38809870","id":"PMC_38809870","title":"Medaka Terb1 Mutant Displays Defects of Synaptonemal Complex Formation and Sexual Difference in Gametogenesis.","date":"2024","source":"Zoological science","url":"https://pubmed.ncbi.nlm.nih.gov/38809870","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":6390,"output_tokens":2023,"usd":0.024758},"stage2":{"model":"claude-opus-4-6","input_tokens":5324,"output_tokens":2116,"usd":0.11928},"total_usd":0.144038,"stage1_batch_id":"msgbatch_01RPbVc9PDH9zQmYK5Hs6srm","stage2_batch_id":"msgbatch_01JVbVLzeKN2yVrsGp3zC8aM","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2014,\n      \"finding\": \"TERB1 forms a heterocomplex with the canonical telomeric protein TRF1 and binds telomere repeat DNA, localizing at telomeres in mouse germ cells during meiotic prophase.\",\n      \"method\": \"Co-immunoprecipitation, telomere DNA binding assays, mouse knockout\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP and functional KO, replicated by multiple subsequent studies\",\n      \"pmids\": [\"24413433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TERB1 promotes telomere association with the nuclear envelope and deposition of the SUN-KASH (LINC) complex, which recruits cytoplasmic motor complexes to drive meiotic chromosomal movement.\",\n      \"method\": \"Mouse Terb1 knockout — abolishes meiotic chromosomal movement; immunofluorescence showing loss of SUN-KASH at telomeres\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined cellular phenotype plus localization data, replicated by subsequent studies\",\n      \"pmids\": [\"24413433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TERB1 binds and recruits cohesin to telomeres to develop structural rigidity reminiscent of centromeres.\",\n      \"method\": \"Mouse Terb1 knockout combined with cohesin localization assays\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO with defined molecular phenotype (cohesin loss at telomeres), replicated by domain mapping studies\",\n      \"pmids\": [\"24413433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CCDC79/TERB1 is a meiosis-specific telomere-associated protein that localizes to telomeres from leptotene to diplotene; its telomere localization does not require telomere-nuclear envelope attachment (persists in SUN1-deficient spermatocytes), but is lost from most telomeres lacking SUN1-connection in SMC1B-deficient spermatocytes.\",\n      \"method\": \"Immunofluorescence in wild-type, SUN1-KO, and SMC1B-KO spermatocytes\",\n      \"journal\": \"BMC cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiment with genetic controls, single lab\",\n      \"pmids\": [\"24885367\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Crystal structure of the TRF1-binding motif of human TERB1 in complex with the TRFH domain of TRF1 was solved; a point mutation specifically disrupting the TERB1-TRF1 interaction causes male-specific infertility with zygotene-early pachytene arrest and failure of X-Y chromosome pairing.\",\n      \"method\": \"X-ray crystallography; Terb1 point-mutant knock-in mouse\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure combined with in vivo point-mutant validation\",\n      \"pmids\": [\"29083416\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TERB1 contains a distinct TERB2-binding (T2B) domain that is dispensable for TRF1 interaction but essential for TERB1-TERB2 interaction and subsequent telomere attachment to the nuclear envelope; cohesin recruitment at telomeres is mediated by the MYB-like domain of TERB1, not by TERB2-MAJIN.\",\n      \"method\": \"Germ-cell-specific TRF1 knockout mouse; domain deletion mapping; mouse knockouts\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple domain-specific KO/KI mice with defined molecular phenotypes\",\n      \"pmids\": [\"29141207\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Crystal structure of the MAJIN-TERB2 complex shows a 2:2 hetero-tetramer that binds strongly to DNA and is tethered through flexible linkers to the inner nuclear membrane and two TERB2-TERB1 (1:1) complexes; during pachytene, TRF1 is displaced from the complex allowing MAJIN-TERB2-TERB1 to directly bind telomeric DNA and form a mature attachment plate.\",\n      \"method\": \"X-ray crystallography, light scattering, structured illumination microscopy, biochemical DNA binding assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with orthogonal biochemical and imaging validation\",\n      \"pmids\": [\"30559341\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Crystal structures of human TERB1-TERB2 and TERB2-MAJIN subcomplexes were solved; specific disruption of the TERB1-TERB2 or TERB2-MAJIN interaction in mice abolishes telomere attachment to the nuclear envelope and causes aberrant homologous pairing and disordered synapsis.\",\n      \"method\": \"X-ray crystallography; Terb2 knock-in point mutant mice disrupting defined interfaces\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structures plus in vivo interface-specific knock-in mutations\",\n      \"pmids\": [\"30718482\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The TERB1 MYB domain has lost its canonical DNA-binding activity; it is dispensable for telomere localization of TERB1 and the downstream TERB2-MAJIN complex and for homologous pairing, but instead regulates cohesin enrichment, promotes axial element remodeling at the pachytene transition, and suppresses telomere erosion.\",\n      \"method\": \"Terb1 MYB-domain point-mutant knock-in mice; in vitro DNA binding assays showing loss of activity; cohesin and SC component localization\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro mutagenesis combined with in vivo knock-in mouse with multiple molecular readouts\",\n      \"pmids\": [\"35081355\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TERB1 is a meiosis-specific telomere protein that acts as a central scaffold: it binds TRF1 (via its TRF1-binding motif, structurally characterized), recruits TERB2-MAJIN through a distinct T2B domain to tether telomeres to the inner nuclear membrane, promotes SUN-KASH (LINC) complex deposition to transmit cytoskeletal forces for chromosome movement, recruits cohesin via its MYB-like domain to confer telomere rigidity, and—after displacing TRF1 at pachytene—allows MAJIN-TERB2-TERB1 to directly bind telomeric DNA and form a mature attachment plate, while the MYB domain also suppresses telomere erosion by regulating cohesin enrichment and axial element remodeling.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"TERB1 is a meiosis-specific telomere scaffold protein that organizes chromosome end attachment to the nuclear envelope and transmits cytoskeletal forces required for homologous chromosome pairing and synapsis during meiotic prophase. TERB1 binds telomeres through interaction with TRF1 via a structurally defined TRF1-binding motif, recruits the TERB2–MAJIN complex through its T2B domain to tether telomeres to the inner nuclear membrane and promote SUN–KASH (LINC) complex deposition for meiotic chromosome movement, and independently recruits cohesin via its MYB-like domain to confer centromere-like structural rigidity at telomeres [PMID:24413433, PMID:29141207]. At pachytene, TRF1 is displaced and the MAJIN–TERB2–TERB1 complex directly binds telomeric DNA to form a mature attachment plate, while the MYB domain—which has lost canonical DNA-binding activity—regulates cohesin enrichment, axial element remodeling, and suppression of telomere erosion [PMID:30559341, PMID:35081355]. Disruption of the TERB1–TRF1 interface causes male-specific infertility with zygotene–pachytene arrest and failure of X–Y chromosome pairing [PMID:29083416].\",\n  \"teleology\": [\n    {\n      \"year\": 2014,\n      \"claim\": \"Identification of TERB1 as a meiosis-specific telomere protein established the first known dedicated bridge between shelterin (TRF1) and the nuclear envelope/cytoskeletal machinery during meiosis, resolving how telomeres recruit LINC complexes and cohesin for chromosome movement and structural rigidity.\",\n      \"evidence\": \"Mouse Terb1 knockout with Co-IP, telomere DNA binding assays, and immunofluorescence for SUN–KASH and cohesin localization\",\n      \"pmids\": [\"24413433\", \"24885367\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of the TERB1–TRF1 interaction was unknown\",\n        \"The mechanism by which TERB1 connects to the inner nuclear membrane was not defined\",\n        \"Individual domain contributions to cohesin recruitment versus membrane tethering were not separated\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Crystal structure of the TERB1–TRF1 interface and domain dissection of TERB1 resolved how a single protein uses separable domains for TRF1 binding, TERB2–MAJIN recruitment (T2B domain), and cohesin recruitment (MYB domain), and showed that disruption of the TRF1 interface alone causes male infertility with zygotene–pachytene arrest.\",\n      \"evidence\": \"X-ray crystallography of human TERB1 TRF1-binding motif with TRFH domain; Terb1 point-mutant knock-in and germ-cell-specific TRF1 KO mice with domain deletions\",\n      \"pmids\": [\"29083416\", \"29141207\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of the TERB1–TERB2 and TERB2–MAJIN interfaces remained unsolved\",\n        \"The mechanism of TRF1 displacement at pachytene was not explained\",\n        \"How the MYB domain recruits cohesin at a molecular level was unclear\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Crystal structures of the MAJIN–TERB2 complex and biochemical reconstitution revealed a 2:2 hetero-tetramer that directly binds DNA, establishing that after TRF1 displacement at pachytene, the MAJIN–TERB2–TERB1 complex forms a mature DNA-binding attachment plate anchored to the inner nuclear membrane.\",\n      \"evidence\": \"X-ray crystallography, light scattering, DNA binding assays, and structured illumination microscopy\",\n      \"pmids\": [\"30559341\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The trigger and regulation of TRF1 displacement were not defined\",\n        \"The structural basis of the TERB1–TERB2 interface was not yet solved\",\n        \"No reconstitution of the full pentameric TRF1–TERB1–TERB2–MAJIN–DNA assembly was achieved\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Crystal structures of human TERB1–TERB2 and TERB2–MAJIN subcomplexes, combined with interface-specific knock-in mutations in mice, demonstrated that each pairwise interaction in the TERB1–TERB2–MAJIN chain is independently essential for telomere–nuclear envelope attachment, homologous pairing, and synapsis.\",\n      \"evidence\": \"X-ray crystallography of both subcomplexes; Terb2 knock-in point mutant mice disrupting defined interfaces\",\n      \"pmids\": [\"30718482\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How the assembled complex integrates with LINC complex components at a structural level was not resolved\",\n        \"Whether TERB1–TERB2–MAJIN has additional post-translational regulation during prophase progression was unknown\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Functional characterization of the TERB1 MYB domain revealed it has lost canonical DNA-binding activity and instead serves a non-canonical role in cohesin enrichment, axial element remodeling at pachytene, and suppression of telomere erosion—functions separable from telomere localization and homologous pairing.\",\n      \"evidence\": \"Terb1 MYB-domain point-mutant knock-in mice with in vitro DNA binding assays and cohesin/SC component localization\",\n      \"pmids\": [\"35081355\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The direct binding partner through which the MYB domain recruits cohesin has not been identified\",\n        \"How MYB-domain-mediated cohesin enrichment mechanistically suppresses telomere erosion is unknown\",\n        \"Whether the MYB domain functions equivalently in female meiosis is untested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include the molecular trigger for TRF1 displacement at pachytene, the identity of the direct MYB-domain binding partner that mediates cohesin recruitment, the full structural reconstitution of the TRF1–TERB1–TERB2–MAJIN–LINC super-complex, and whether TERB1 functions equivalently in oogenesis.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No molecular trigger identified for TRF1 displacement at pachytene\",\n        \"Direct cohesin-recruiting partner of the MYB domain unknown\",\n        \"Full structural reconstitution of the telomere attachment complex not achieved\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1, 2, 5]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [2, 8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [0, 3, 4]},\n      {\"term_id\": \"GO:0005635\", \"supporting_discovery_ids\": [1, 5, 6, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0, 1, 4, 7]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"complexes\": [\n      \"MAJIN-TERB2-TERB1\",\n      \"TRF1-TERB1\"\n    ],\n    \"partners\": [\n      \"TRF1\",\n      \"TERB2\",\n      \"MAJIN\",\n      \"SUN1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}