{"gene":"ESPL1","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":2013,"finding":"Overexpression of Separase (ESPL1) in mammary epithelium causes chromosomal instability including premature chromatid separation (PCS), lagging chromosomes, anaphase bridges, micronuclei, centrosome amplification, and multinucleated cells, establishing a direct role for ESPL1 in maintaining chromosomal segregation fidelity in vivo.","method":"MMTV-Espl1 transgenic mouse model; cytogenetic analysis of mammary tumors","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean transgenic overexpression model with defined cytological phenotypes, single lab with multiple orthogonal readouts","pmids":["24276237"],"is_preprint":false},{"year":2016,"finding":"The transcription factor c-MYB binds to a c-MYB binding sequence in the ESPL1 promoter and positively regulates ESPL1/Separase transcription; c-MYB silencing reduces Separase protein levels in CML cell lines.","method":"Gelshift assay, ChIP assay, RNA silencing of c-MYB, qRT-PCR and Western blot","journal":"Biomarker research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and gelshift confirm direct promoter binding, RNA silencing confirms functional consequence, single lab","pmids":["26937281"],"is_preprint":false},{"year":2024,"finding":"ESPL1 interacts with MDM2 (an E3 ubiquitin protein ligase) in gastric cancer cells; this interaction was identified by co-immunoprecipitation and linked to apatinib resistance.","method":"Co-immunoprecipitation, CRISPR genome-wide gain-of-function screen, loss-of-function studies","journal":"Cancer cell international","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP/pulldown in a cancer cell context, single lab, no mechanistic follow-up of the interaction itself","pmids":["38402402"],"is_preprint":false},{"year":2024,"finding":"PAX2 transcriptionally activates ESPL1 by binding to its promoter region; ESPL1 overexpression activates the JAK2/STAT3 pathway to enhance cisplatin resistance in bladder cancer cells, and this effect is blocked by the JAK2 inhibitor AG490.","method":"ChIP assay, luciferase reporter gene assay, siRNA knockdown, pharmacological inhibition with AG490, xenograft tumor model","journal":"Naunyn-Schmiedeberg's archives of pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP + luciferase confirm promoter binding, functional epistasis with JAK2 inhibitor establishes pathway order, single lab with multiple orthogonal methods","pmids":["38573552"],"is_preprint":false},{"year":2025,"finding":"BRD4 acts as a scaffold for the ubiquitin ligase TRIM21 and the RNA demethylase ALKBH5, promoting ubiquitination and degradation of ALKBH5; BRD4 inhibition stabilizes ALKBH5, which then demethylates ESPL1 mRNA (m6A), reducing binding of the m6A reader IGF2BP3 and leading to ESPL1 mRNA decay.","method":"siRNA knockdown, BRD4 inhibitor (JQ1), co-IP for BRD4/TRIM21/ALKBH5 complex, m6A quantification, RIP assay for IGF2BP3-ESPL1 mRNA binding, animal and clinical validation","journal":"Acta pharmaceutica Sinica. B","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (co-IP, RIP, m6A assay, inhibitor studies) in single lab; mechanism is detailed but awaits independent replication","pmids":["40370540"],"is_preprint":false},{"year":2025,"finding":"Heterozygous knockout of espl1 in fish (loach and zebrafish) impairs mitotic sister chromatid separation in spermatogonia, causing chromosome number doubling and production of unreduced (diploid) sperms, confirming ESPL1's essential role in mitotic cohesin cleavage for sister chromatid separation.","method":"CRISPR/Cas9 heterozygous knockout in diploid loach and zebrafish; ploidy analysis of progeny; cytological analysis of spermatogonia","journal":"Molecular biology and evolution","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic loss-of-function in two independent vertebrate model organisms with direct cytological readout of chromatid separation defects, replicated across species","pmids":["40794720"],"is_preprint":false},{"year":2025,"finding":"Drosophila Separase (Sse, ortholog of ESPL1) physically interacts with nuclear lamins (Lamin C and Lamin Dm0) and colocalizes with them at the nuclear envelope during interphase; loss of Sse disrupts nuclear organization in larval muscles. In human fibroblasts, depletion of ESPL1 causes misshapen nuclei and increased lamin A levels, and ESPL1 co-immunoprecipitates with lamin A, indicating an evolutionarily conserved functional interaction.","method":"Co-immunoprecipitation (Drosophila and human fibroblasts), immunofluorescence colocalization, ESPL1 siRNA knockdown in SV40 fibroblasts, nuclear morphology analysis, locomotion assay","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP in two organisms plus functional nuclear phenotype upon depletion, but preprint not yet peer-reviewed","pmids":["bio_10.1101_2025.02.19.638993"],"is_preprint":true},{"year":2026,"finding":"Iron overload activates a p53/CDK1/ESPL1 pathway in aged oocytes: p53 upregulation and CDK1 downregulation leads to increased ESPL1 activity causing premature cleavage of chromosomal cohesin, resulting in spindle abnormalities and aneuploidy during meiosis.","method":"Naturally aged and FeSO4-induced iron overload mouse models; adenovirus infection for gene manipulation; in vitro oocyte culture; measurement of p53, p21, CDK1, and ESPL1 protein levels; spindle and chromosome analysis","journal":"Free radical biology & medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic/pharmacological manipulation in two mouse models with direct readout of cohesin cleavage and meiotic fidelity, single lab","pmids":["42214643"],"is_preprint":false}],"current_model":"ESPL1/Separase is a cysteine endopeptidase that cleaves chromosomal cohesin at the metaphase-to-anaphase transition to enable sister chromatid separation; its activity is regulated transcriptionally by c-MYB and PAX2, post-transcriptionally via BRD4/ALKBH5-mediated m6A modification of its mRNA, and functionally by a p53/CDK1 axis during meiosis; beyond cohesin cleavage, ESPL1 physically interacts with nuclear lamins to regulate nuclear envelope organization, and interacts with MDM2 in cancer cells, with overexpression driving chromosomal instability and tumorigenesis."},"narrative":{"mechanistic_narrative":"ESPL1/Separase is the protease responsible for cleaving chromosomal cohesin to enable sister chromatid separation, and it functions as a central guardian of genome segregation fidelity [PMID:40794720]. Genetic loss-of-function in two vertebrate models (loach and zebrafish) demonstrates that ESPL1 is essential for mitotic sister chromatid separation in spermatogonia, with heterozygous knockout causing chromosome number doubling and unreduced diploid sperm [PMID:40794720], while its activity in meiosis is gated by a p53/CDK1 axis whose dysregulation under iron overload drives premature cohesin cleavage, spindle abnormalities, and aneuploidy in aged oocytes [PMID:42214643]. Conversely, ESPL1 overexpression in mammary epithelium produces chromosomal instability—premature chromatid separation, anaphage bridges, micronuclei, and centrosome amplification—linking dosage imbalance to tumorigenesis [PMID:24276237]. Beyond cohesin cleavage, ESPL1 physically associates with nuclear lamins at the nuclear envelope and is required for normal nuclear morphology, and its depletion in human fibroblasts elevates lamin A and distorts nuclei [PMID:bio_10.1101_2025.02.19.638993]. ESPL1 expression is tightly controlled: it is transcriptionally activated by c-MYB [PMID:26937281] and PAX2 [PMID:38573552], and its mRNA stability is governed by an m6A circuit in which BRD4-directed degradation of the demethylase ALKBH5 preserves IGF2BP3-dependent ESPL1 transcript stability [PMID:40370540]. In cancer, elevated ESPL1 engages the JAK2/STAT3 pathway to confer cisplatin resistance [PMID:38573552] and interacts with the E3 ligase MDM2 in the context of apatinib resistance [PMID:38402402].","teleology":[{"year":2013,"claim":"Establishing that ESPL1 dosage matters in vivo, overexpression was shown to actively destabilize chromosome segregation rather than being merely a passive cleavage enzyme.","evidence":"MMTV-Espl1 transgenic mouse model with cytogenetic analysis of mammary tumors","pmids":["24276237"],"confidence":"Medium","gaps":["Does not establish whether the instability arises from excess cohesin cleavage or from off-target substrates","Does not define ESPL1 protease activity directly in the tumor cells"]},{"year":2016,"claim":"Addressed how ESPL1 levels are set, identifying c-MYB as a direct transcriptional driver of Separase expression.","evidence":"Gelshift, ChIP, c-MYB silencing with qRT-PCR/Western in CML cell lines","pmids":["26937281"],"confidence":"Medium","gaps":["Does not connect c-MYB-driven ESPL1 levels to a segregation or disease phenotype","Single cell-type context (CML)"]},{"year":2024,"claim":"Extended the transcriptional control logic and linked ESPL1 output to a drug-resistance signaling axis, showing PAX2 activates ESPL1 which feeds the JAK2/STAT3 pathway.","evidence":"ChIP, luciferase reporter, siRNA, AG490 inhibition, xenograft in bladder cancer cells","pmids":["38573552"],"confidence":"Medium","gaps":["Mechanism by which a cohesin protease engages JAK2/STAT3 is not defined","Whether the effect requires ESPL1 protease activity is untested"]},{"year":2024,"claim":"Identified a physical partner outside the segregation machinery, placing ESPL1 in contact with the E3 ligase MDM2 in a drug-resistance setting.","evidence":"Co-immunoprecipitation plus CRISPR gain-of-function screen in gastric cancer cells","pmids":["38402402"],"confidence":"Low","gaps":["Single Co-IP without reciprocal validation or mapping of the interaction","No functional consequence of the ESPL1-MDM2 interaction established","Directionality (is ESPL1 an MDM2 substrate?) unknown"]},{"year":2025,"claim":"Defined post-transcriptional control of ESPL1, showing its mRNA stability depends on an m6A reader/eraser balance set by BRD4-mediated ALKBH5 turnover.","evidence":"siRNA, JQ1, co-IP of BRD4/TRIM21/ALKBH5, m6A quantification, IGF2BP3 RIP, animal and clinical validation","pmids":["40370540"],"confidence":"Medium","gaps":["Awaits independent replication","Does not map the specific m6A sites on ESPL1 mRNA functionally","Connection to ESPL1's segregation function not tested"]},{"year":2025,"claim":"Provided the cleanest genetic proof of ESPL1's core function, demonstrating it is essential for mitotic sister chromatid separation in a whole animal.","evidence":"CRISPR/Cas9 heterozygous knockout in loach and zebrafish with ploidy and spermatogonial cytology","pmids":["40794720"],"confidence":"High","gaps":["Does not directly visualize cohesin cleavage by ESPL1 in this system","Haploinsufficiency mechanism for the dominant unreduced-sperm phenotype not fully resolved"]},{"year":2025,"claim":"Uncovered a non-canonical role at the nuclear envelope, showing ESPL1 physically and functionally associates with lamins to maintain nuclear architecture.","evidence":"Reciprocal co-IP in Drosophila and human fibroblasts, IF colocalization, ESPL1 siRNA with nuclear morphology and locomotion assays (preprint)","pmids":["bio_10.1101_2025.02.19.638993"],"confidence":"Medium","gaps":["Preprint not yet peer-reviewed","Whether lamins are proteolytic substrates of ESPL1 is not established","Independence from the cohesin-cleavage function unclear"]},{"year":2026,"claim":"Connected upstream stress signaling to ESPL1 activity in meiosis, showing a p53/CDK1 axis gates Separase to prevent premature cohesin cleavage in oocytes.","evidence":"Naturally aged and FeSO4 iron-overload mouse models, adenoviral manipulation, oocyte culture, spindle/chromosome analysis","pmids":["42214643"],"confidence":"Medium","gaps":["Whether CDK1 regulates ESPL1 directly versus indirectly is not resolved","Single lab; generality beyond iron-overload aging context untested"]},{"year":null,"claim":"How ESPL1's regulatory inputs (c-MYB, PAX2, m6A, p53/CDK1) and non-canonical lamin interaction integrate to control its protease activity in time and space remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural or biochemical reconstitution in the corpus linking regulators to protease state","Whether lamins and MDM2 are substrates versus binding partners is undetermined","No unified model coupling transcriptional, post-transcriptional, and signaling control"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[5,7]}],"localization":[{"term_id":"GO:0005635","term_label":"nuclear envelope","supporting_discovery_ids":[6]},{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[5]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0,5,7]}],"complexes":[],"partners":["MDM2","LMNA","IGF2BP3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q14674","full_name":"Separin","aliases":["Caspase-like protein ESPL1","Extra spindle poles-like 1 protein","Separase"],"length_aa":2120,"mass_kda":233.2,"function":"Caspase-like protease, which plays a central role in the chromosome segregation by cleaving the SCC1/RAD21 subunit of the cohesin complex at the onset of anaphase. During most of the cell cycle, it is inactivated by different mechanisms","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/Q14674/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/ESPL1","classification":"Common Essential","n_dependent_lines":1207,"n_total_lines":1208,"dependency_fraction":0.9991721854304636},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"FKBP5","stoichiometry":0.2},{"gene":"PPP2CA","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/ESPL1","total_profiled":1310},"omim":[{"mim_id":"620335","title":"CELL DIVISION CYCLE 20B; CDC20B","url":"https://www.omim.org/entry/620335"},{"mim_id":"617969","title":"COILED-COIL DOMAIN-CONTAINING PROTEIN 63; CCDC63","url":"https://www.omim.org/entry/617969"},{"mim_id":"615562","title":"SPERM-ASSOCIATED ANTIGEN 5; SPAG5","url":"https://www.omim.org/entry/615562"},{"mim_id":"614718","title":"KINETOCHORE-LOCALIZED ASTRIN/SPAG5-BINDING PROTEIN; KNSTRN","url":"https://www.omim.org/entry/614718"},{"mim_id":"612425","title":"SHUGOSHIN-LIKE 2; SGOL2","url":"https://www.omim.org/entry/612425"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"bone marrow","ntpm":8.0},{"tissue":"esophagus","ntpm":14.2},{"tissue":"lymphoid tissue","ntpm":9.9}],"url":"https://www.proteinatlas.org/search/ESPL1"},"hgnc":{"alias_symbol":["KIAA0165","ESP1","SEPA"],"prev_symbol":[]},"alphafold":{"accession":"Q14674","domains":[{"cath_id":"-","chopping":"163-236_243-286","consensus_level":"medium","plddt":80.6117,"start":163,"end":286},{"cath_id":"3.40.50,3.40.50","chopping":"1937-2120","consensus_level":"medium","plddt":91.7883,"start":1937,"end":2120}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q14674","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q14674-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q14674-F1-predicted_aligned_error_v6.png","plddt_mean":75.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ESPL1","jax_strain_url":"https://www.jax.org/strain/search?query=ESPL1"},"sequence":{"accession":"Q14674","fasta_url":"https://rest.uniprot.org/uniprotkb/Q14674.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q14674/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q14674"}},"corpus_meta":[{"pmid":"19167332","id":"PMC_19167332","title":"SEPA-1 mediates the specific recognition and degradation of P granule components by autophagy in C. elegans.","date":"2009","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/19167332","citation_count":198,"is_preprint":false},{"pmid":"7476198","id":"PMC_7476198","title":"SepA, the major extracellular protein of Shigella flexneri: autonomous secretion and involvement in tissue invasion.","date":"1995","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/7476198","citation_count":154,"is_preprint":false},{"pmid":"11854405","id":"PMC_11854405","title":"Functional characterization and localization of the Aspergillus nidulans formin SEPA.","date":"2002","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/11854405","citation_count":125,"is_preprint":false},{"pmid":"9218790","id":"PMC_9218790","title":"The Aspergillus nidulans sepA gene encodes an FH1/2 protein involved in cytokinesis and the maintenance of cellular polarity.","date":"1997","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/9218790","citation_count":108,"is_preprint":false},{"pmid":"24276237","id":"PMC_24276237","title":"MMTV-Espl1 transgenic mice develop aneuploid, estrogen receptor alpha (ERα)-positive mammary adenocarcinomas.","date":"2013","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/24276237","citation_count":56,"is_preprint":false},{"pmid":"27997732","id":"PMC_27997732","title":"The metalloprotease SepA governs processing of accumulation-associated protein and shapes intercellular adhesive surface properties in Staphylococcus epidermidis.","date":"2017","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/27997732","citation_count":46,"is_preprint":false},{"pmid":"28598765","id":"PMC_28598765","title":"Shigella depends on SepA to destabilize the intestinal epithelial integrity via cofilin activation.","date":"2017","source":"Gut 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England)","url":"https://pubmed.ncbi.nlm.nih.gov/35199150","citation_count":29,"is_preprint":false},{"pmid":"31629796","id":"PMC_31629796","title":"Quercetin a major biomarker of Psidium guajava L. inhibits SepA protease activity of Shigella flexneri in treatment of infectious diarrhoea.","date":"2019","source":"Microbial pathogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/31629796","citation_count":23,"is_preprint":false},{"pmid":"19479821","id":"PMC_19479821","title":"The STE group kinase SepA controls cleavage furrow formation in Dictyostelium.","date":"2009","source":"Cell motility and the cytoskeleton","url":"https://pubmed.ncbi.nlm.nih.gov/19479821","citation_count":15,"is_preprint":false},{"pmid":"31892573","id":"PMC_31892573","title":"High Rate of Detection of Human ESPL1-HBV S Fusion Gene in Patients With HBV-related Liver Cancer: A Chinese Case-Control Study.","date":"2020","source":"Anticancer research","url":"https://pubmed.ncbi.nlm.nih.gov/31892573","citation_count":15,"is_preprint":false},{"pmid":"34724811","id":"PMC_34724811","title":"SepA Enhances Shigella Invasion of Epithelial Cells by Degrading Alpha-1 Antitrypsin and Producing a Neutrophil Chemoattractant.","date":"2021","source":"mBio","url":"https://pubmed.ncbi.nlm.nih.gov/34724811","citation_count":11,"is_preprint":false},{"pmid":"37006282","id":"PMC_37006282","title":"Pan-Cancer analysis and experimental validation identify the oncogenic nature of ESPL1: Potential therapeutic target in colorectal cancer.","date":"2023","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/37006282","citation_count":10,"is_preprint":false},{"pmid":"33308056","id":"PMC_33308056","title":"Serum ESPL1 Can Be Used as a Biomarker for Patients With Hepatitis B Virus-Related Liver Cancer: A Chinese Case-Control Study.","date":"2020","source":"Technology in cancer research & treatment","url":"https://pubmed.ncbi.nlm.nih.gov/33308056","citation_count":10,"is_preprint":false},{"pmid":"26937281","id":"PMC_26937281","title":"c-MYB is a transcriptional regulator of ESPL1/Separase in BCR-ABL-positive chronic myeloid leukemia.","date":"2016","source":"Biomarker research","url":"https://pubmed.ncbi.nlm.nih.gov/26937281","citation_count":10,"is_preprint":false},{"pmid":"40370540","id":"PMC_40370540","title":"BRD4 regulates m6A of ESPL1 mRNA via interaction with ALKBH5 to modulate breast cancer progression.","date":"2025","source":"Acta pharmaceutica Sinica. 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cytogenetic analysis of mammary tumors\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean transgenic overexpression model with defined cytological phenotypes, single lab with multiple orthogonal readouts\",\n      \"pmids\": [\"24276237\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The transcription factor c-MYB binds to a c-MYB binding sequence in the ESPL1 promoter and positively regulates ESPL1/Separase transcription; c-MYB silencing reduces Separase protein levels in CML cell lines.\",\n      \"method\": \"Gelshift assay, ChIP assay, RNA silencing of c-MYB, qRT-PCR and Western blot\",\n      \"journal\": \"Biomarker research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and gelshift confirm direct promoter binding, RNA silencing confirms functional consequence, single lab\",\n      \"pmids\": [\"26937281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"ESPL1 interacts with MDM2 (an E3 ubiquitin protein ligase) in gastric cancer cells; this interaction was identified by co-immunoprecipitation and linked to apatinib resistance.\",\n      \"method\": \"Co-immunoprecipitation, CRISPR genome-wide gain-of-function screen, loss-of-function studies\",\n      \"journal\": \"Cancer cell international\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP/pulldown in a cancer cell context, single lab, no mechanistic follow-up of the interaction itself\",\n      \"pmids\": [\"38402402\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PAX2 transcriptionally activates ESPL1 by binding to its promoter region; ESPL1 overexpression activates the JAK2/STAT3 pathway to enhance cisplatin resistance in bladder cancer cells, and this effect is blocked by the JAK2 inhibitor AG490.\",\n      \"method\": \"ChIP assay, luciferase reporter gene assay, siRNA knockdown, pharmacological inhibition with AG490, xenograft tumor model\",\n      \"journal\": \"Naunyn-Schmiedeberg's archives of pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP + luciferase confirm promoter binding, functional epistasis with JAK2 inhibitor establishes pathway order, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"38573552\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"BRD4 acts as a scaffold for the ubiquitin ligase TRIM21 and the RNA demethylase ALKBH5, promoting ubiquitination and degradation of ALKBH5; BRD4 inhibition stabilizes ALKBH5, which then demethylates ESPL1 mRNA (m6A), reducing binding of the m6A reader IGF2BP3 and leading to ESPL1 mRNA decay.\",\n      \"method\": \"siRNA knockdown, BRD4 inhibitor (JQ1), co-IP for BRD4/TRIM21/ALKBH5 complex, m6A quantification, RIP assay for IGF2BP3-ESPL1 mRNA binding, animal and clinical validation\",\n      \"journal\": \"Acta pharmaceutica Sinica. B\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (co-IP, RIP, m6A assay, inhibitor studies) in single lab; mechanism is detailed but awaits independent replication\",\n      \"pmids\": [\"40370540\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Heterozygous knockout of espl1 in fish (loach and zebrafish) impairs mitotic sister chromatid separation in spermatogonia, causing chromosome number doubling and production of unreduced (diploid) sperms, confirming ESPL1's essential role in mitotic cohesin cleavage for sister chromatid separation.\",\n      \"method\": \"CRISPR/Cas9 heterozygous knockout in diploid loach and zebrafish; ploidy analysis of progeny; cytological analysis of spermatogonia\",\n      \"journal\": \"Molecular biology and evolution\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic loss-of-function in two independent vertebrate model organisms with direct cytological readout of chromatid separation defects, replicated across species\",\n      \"pmids\": [\"40794720\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Drosophila Separase (Sse, ortholog of ESPL1) physically interacts with nuclear lamins (Lamin C and Lamin Dm0) and colocalizes with them at the nuclear envelope during interphase; loss of Sse disrupts nuclear organization in larval muscles. In human fibroblasts, depletion of ESPL1 causes misshapen nuclei and increased lamin A levels, and ESPL1 co-immunoprecipitates with lamin A, indicating an evolutionarily conserved functional interaction.\",\n      \"method\": \"Co-immunoprecipitation (Drosophila and human fibroblasts), immunofluorescence colocalization, ESPL1 siRNA knockdown in SV40 fibroblasts, nuclear morphology analysis, locomotion assay\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP in two organisms plus functional nuclear phenotype upon depletion, but preprint not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.02.19.638993\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Iron overload activates a p53/CDK1/ESPL1 pathway in aged oocytes: p53 upregulation and CDK1 downregulation leads to increased ESPL1 activity causing premature cleavage of chromosomal cohesin, resulting in spindle abnormalities and aneuploidy during meiosis.\",\n      \"method\": \"Naturally aged and FeSO4-induced iron overload mouse models; adenovirus infection for gene manipulation; in vitro oocyte culture; measurement of p53, p21, CDK1, and ESPL1 protein levels; spindle and chromosome analysis\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic/pharmacological manipulation in two mouse models with direct readout of cohesin cleavage and meiotic fidelity, single lab\",\n      \"pmids\": [\"42214643\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ESPL1/Separase is a cysteine endopeptidase that cleaves chromosomal cohesin at the metaphase-to-anaphase transition to enable sister chromatid separation; its activity is regulated transcriptionally by c-MYB and PAX2, post-transcriptionally via BRD4/ALKBH5-mediated m6A modification of its mRNA, and functionally by a p53/CDK1 axis during meiosis; beyond cohesin cleavage, ESPL1 physically interacts with nuclear lamins to regulate nuclear envelope organization, and interacts with MDM2 in cancer cells, with overexpression driving chromosomal instability and tumorigenesis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ESPL1/Separase is the protease responsible for cleaving chromosomal cohesin to enable sister chromatid separation, and it functions as a central guardian of genome segregation fidelity [#5]. Genetic loss-of-function in two vertebrate models (loach and zebrafish) demonstrates that ESPL1 is essential for mitotic sister chromatid separation in spermatogonia, with heterozygous knockout causing chromosome number doubling and unreduced diploid sperm [#5], while its activity in meiosis is gated by a p53/CDK1 axis whose dysregulation under iron overload drives premature cohesin cleavage, spindle abnormalities, and aneuploidy in aged oocytes [#7]. Conversely, ESPL1 overexpression in mammary epithelium produces chromosomal instability—premature chromatid separation, anaphage bridges, micronuclei, and centrosome amplification—linking dosage imbalance to tumorigenesis [#0]. Beyond cohesin cleavage, ESPL1 physically associates with nuclear lamins at the nuclear envelope and is required for normal nuclear morphology, and its depletion in human fibroblasts elevates lamin A and distorts nuclei [#6]. ESPL1 expression is tightly controlled: it is transcriptionally activated by c-MYB [#1] and PAX2 [#3], and its mRNA stability is governed by an m6A circuit in which BRD4-directed degradation of the demethylase ALKBH5 preserves IGF2BP3-dependent ESPL1 transcript stability [#4]. In cancer, elevated ESPL1 engages the JAK2/STAT3 pathway to confer cisplatin resistance [#3] and interacts with the E3 ligase MDM2 in the context of apatinib resistance [#2].\",\n  \"teleology\": [\n    {\n      \"year\": 2013,\n      \"claim\": \"Establishing that ESPL1 dosage matters in vivo, overexpression was shown to actively destabilize chromosome segregation rather than being merely a passive cleavage enzyme.\",\n      \"evidence\": \"MMTV-Espl1 transgenic mouse model with cytogenetic analysis of mammary tumors\",\n      \"pmids\": [\"24276237\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not establish whether the instability arises from excess cohesin cleavage or from off-target substrates\", \"Does not define ESPL1 protease activity directly in the tumor cells\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Addressed how ESPL1 levels are set, identifying c-MYB as a direct transcriptional driver of Separase expression.\",\n      \"evidence\": \"Gelshift, ChIP, c-MYB silencing with qRT-PCR/Western in CML cell lines\",\n      \"pmids\": [\"26937281\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not connect c-MYB-driven ESPL1 levels to a segregation or disease phenotype\", \"Single cell-type context (CML)\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended the transcriptional control logic and linked ESPL1 output to a drug-resistance signaling axis, showing PAX2 activates ESPL1 which feeds the JAK2/STAT3 pathway.\",\n      \"evidence\": \"ChIP, luciferase reporter, siRNA, AG490 inhibition, xenograft in bladder cancer cells\",\n      \"pmids\": [\"38573552\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which a cohesin protease engages JAK2/STAT3 is not defined\", \"Whether the effect requires ESPL1 protease activity is untested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identified a physical partner outside the segregation machinery, placing ESPL1 in contact with the E3 ligase MDM2 in a drug-resistance setting.\",\n      \"evidence\": \"Co-immunoprecipitation plus CRISPR gain-of-function screen in gastric cancer cells\",\n      \"pmids\": [\"38402402\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single Co-IP without reciprocal validation or mapping of the interaction\", \"No functional consequence of the ESPL1-MDM2 interaction established\", \"Directionality (is ESPL1 an MDM2 substrate?) unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defined post-transcriptional control of ESPL1, showing its mRNA stability depends on an m6A reader/eraser balance set by BRD4-mediated ALKBH5 turnover.\",\n      \"evidence\": \"siRNA, JQ1, co-IP of BRD4/TRIM21/ALKBH5, m6A quantification, IGF2BP3 RIP, animal and clinical validation\",\n      \"pmids\": [\"40370540\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Awaits independent replication\", \"Does not map the specific m6A sites on ESPL1 mRNA functionally\", \"Connection to ESPL1's segregation function not tested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Provided the cleanest genetic proof of ESPL1's core function, demonstrating it is essential for mitotic sister chromatid separation in a whole animal.\",\n      \"evidence\": \"CRISPR/Cas9 heterozygous knockout in loach and zebrafish with ploidy and spermatogonial cytology\",\n      \"pmids\": [\"40794720\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not directly visualize cohesin cleavage by ESPL1 in this system\", \"Haploinsufficiency mechanism for the dominant unreduced-sperm phenotype not fully resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Uncovered a non-canonical role at the nuclear envelope, showing ESPL1 physically and functionally associates with lamins to maintain nuclear architecture.\",\n      \"evidence\": \"Reciprocal co-IP in Drosophila and human fibroblasts, IF colocalization, ESPL1 siRNA with nuclear morphology and locomotion assays (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.02.19.638993\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint not yet peer-reviewed\", \"Whether lamins are proteolytic substrates of ESPL1 is not established\", \"Independence from the cohesin-cleavage function unclear\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Connected upstream stress signaling to ESPL1 activity in meiosis, showing a p53/CDK1 axis gates Separase to prevent premature cohesin cleavage in oocytes.\",\n      \"evidence\": \"Naturally aged and FeSO4 iron-overload mouse models, adenoviral manipulation, oocyte culture, spindle/chromosome analysis\",\n      \"pmids\": [\"42214643\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether CDK1 regulates ESPL1 directly versus indirectly is not resolved\", \"Single lab; generality beyond iron-overload aging context untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How ESPL1's regulatory inputs (c-MYB, PAX2, m6A, p53/CDK1) and non-canonical lamin interaction integrate to control its protease activity in time and space remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural or biochemical reconstitution in the corpus linking regulators to protease state\", \"Whether lamins and MDM2 are substrates versus binding partners is undetermined\", \"No unified model coupling transcriptional, post-transcriptional, and signaling control\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [5, 7]},\n      {\"term_id\": \"GO:0008233\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005635\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0, 5, 7]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"MDM2\", \"LMNA\", \"IGF2BP3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}