{"gene":"PDS5A","run_date":"2026-06-10T05:19:53","timeline":{"discoveries":[{"year":2022,"finding":"Cohesin acetylation by ESCO1 restricts chromatin loop length and architectural stripes by promoting PDS5A binding to cohesin, which acts as a brake enabling pausing and restart of loop enlargement; HDAC8-mediated deacetylation promotes loop extension by releasing this PDS5A-bound braked state. This role in loop-length control is distinct from the canonical WAPL-mediated DNA release pathway.","method":"Hi-C, ChIP-seq, auxin-inducible degron depletion of ESCO1/HDAC8, functional genomics in human cells","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal genomic and functional methods (Hi-C, ChIP-seq, protein depletion), mechanistic model supported by genetic epistasis between acetylation cycle components and PDS5A","pmids":["35710836"],"is_preprint":false},{"year":2023,"finding":"PDS5A loss impairs cohesin unloading, causing aberrant cohesin activity that generates ectopic insulation sites and disrupts ultra-long Polycomb loops, which are required for robust silencing of a subset of PRC1/PRC2 target genes; derepression occurs without loss of Polycomb chromatin domains, placing PDS5A as a cohesin unloading regulator whose activity maintains genome architecture needed for Polycomb gene silencing.","method":"CRISPR screen in mouse ESCs, PDS5A deletion, Hi-C, RNA-seq, ChIP-seq","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function with multiple orthogonal genomic readouts (Hi-C, RNA-seq, ChIP-seq) defining pathway position","pmids":["38071364"],"is_preprint":false},{"year":2020,"finding":"Depletion of Pds5A or Pds5B individually increased SMC3 acetylation in perturbed cell cycle, whereas co-depletion of both severely impaired SMC3 acetylation, demonstrating overlapping roles in facilitating SMC3 acetylation. Additionally, Pds5A/B loss stabilized WAPL on chromatin and activated the spindle assembly checkpoint via an ATR-Chk1-dependent mechanism, revealing non-redundant functions in cohesin removal.","method":"siRNA knockdown, western blot for acetyl-SMC3, immunofluorescence for MAD2/WAPL, flow cytometry, Chk1 inhibitor rescue","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean knockdown with defined molecular readouts (SMC3 acetylation, WAPL chromatin binding), single lab, two orthogonal methods","pmids":["32760717"],"is_preprint":false},{"year":2025,"finding":"Pds5A localizes to spindle fibers in mouse oocytes at metaphase I and II and plays a non-canonical, cohesion-independent role in meiotic spindle assembly. Mechanistically, Pds5A recruits the deubiquitinase USP14 to the spindle apparatus, which stabilizes kinesin family member KIF5B by deubiquitination, thereby regulating spindle elongation.","method":"Morpholino depletion, genetic knockout in mouse oocytes, immunofluorescence, co-immunoprecipitation, ubiquitination assay","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic ablation plus Co-IP identifying USP14 as recruited factor, ubiquitination assay for KIF5B stabilization, replicated by two depletion strategies (morpholino and KO)","pmids":["40215310"],"is_preprint":false},{"year":2007,"finding":"SCC-112/PDS5A protein was found to interact with p63 by co-immunoprecipitation, and overexpression of SCC-112 up-regulated p63 expression, promoting cell proliferation in G2/M phase.","method":"Co-immunoprecipitation, overexpression/siRNA knockdown, MTT proliferation assay, FACS cell cycle analysis","journal":"Journal of cancer research and clinical oncology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP from a single lab, no reciprocal validation or in vitro confirmation","pmids":["17846787"],"is_preprint":false},{"year":2026,"finding":"PDS5A interacts with TOP2B and CTCF; a novel CTCF N-terminal region (amino acids 95–116) is required for the CTCF–PDS5A–TOP2B interaction in vitro and for TOP2B-mediated enrichment of PDS5A chromatin occupancy in vivo. Catalytically active TOP2B increases PDS5A occupancy genome-wide, and PDS5A knockdown reduces TOP2B chromatin occupancy and alters gene expression.","method":"In vitro binding assay with CTCF deletion mutants, ChIP-seq, inducible PDS5A knockdown, chromatin loop analysis by Hi-C","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro interaction mapping with mutagenesis plus ChIP-seq in vivo, single lab, preprint not yet peer-reviewed","pmids":["41959374"],"is_preprint":true},{"year":2025,"finding":"PDS5 proteins stop cohesin-mediated loop extrusion by facilitating dissociation of NIPBL from cohesin, as demonstrated by in vitro single-molecule imaging; this mechanism limits cohesin-NIPBL lifetime and is required for establishment of CTCF boundaries and maintenance of chromatin compartmentalization.","method":"In vitro single-molecule imaging, Hi-C, in silico polymer modelling","journal":"bioRxiv","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro single-molecule reconstitution of loop extrusion with and without PDS5, corroborated by Hi-C and computational modelling","pmids":["bio_10.1101_2025.08.30.673243"],"is_preprint":true},{"year":2025,"finding":"PDS5A tunes the conformational ensemble of CTCF before cohesin engagement, influencing the probability that cohesin stalls at CTCF boundaries; upon cohesin binding, PDS5A enhances the mechanical stability of loop anchors, reinforcing orientation-dependent boundaries.","method":"Single-molecule imaging of CTCF conformational dynamics, in vitro cohesin–CTCF–PDS5A reconstitution, mechanical stability assays","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro reconstitution with mechanistic insight, but single lab and preprint; novel claim not yet replicated","pmids":["bio_10.1101_2025.11.25.690553"],"is_preprint":true},{"year":2026,"finding":"In medaka embryos, simultaneous depletion of both Pds5a and Pds5b, but not single depletion, caused pronounced increases in long-range chromatin contacts and de novo formation of extended chromatin loops by Hi-C, demonstrating that Pds5a and Pds5b act cooperatively to constrain cohesin-mediated loop extrusion in vivo during development.","method":"Morpholino-mediated depletion in medaka embryos, in situ Hi-C, RNA-seq","journal":"Development, growth & differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo Hi-C with genetic epistasis (single vs double depletion), single lab","pmids":["41994921"],"is_preprint":false}],"current_model":"PDS5A is a regulatory subunit of the cohesin complex that controls chromatin loop length and genome organization by: (1) acting as a NIPBL-dissociation factor that stops loop extrusion in vitro; (2) occupying a cohesin-bound 'braked' state promoted by SMC3 acetylation (via ESCO1) to pause loop enlargement, with HDAC8-mediated deacetylation restarting extrusion; (3) cooperating with TOP2B at CTCF-bound chromatin boundaries, where a CTCF N-terminal region (aa 95–116) is required for their interaction; (4) maintaining cohesin unloading to preserve ultra-long Polycomb loops required for gene silencing; and (5) recruiting USP14 deubiquitinase to the meiotic spindle for KIF5B stabilization, revealing a non-canonical spindle-regulatory function in oocytes."},"narrative":{"mechanistic_narrative":"PDS5A is a regulatory subunit of the cohesin complex that constrains cohesin-mediated DNA loop extrusion to shape three-dimensional genome architecture [PMID:35710836, PMID:bio_10.1101_2025.08.30.673243]. Mechanistically, it acts as a NIPBL-dissociation factor that limits the cohesin–NIPBL lifetime, halting loop extrusion and enabling establishment of CTCF boundaries and chromatin compartmentalization [PMID:bio_10.1101_2025.08.30.673243]. PDS5A binding to cohesin is promoted by ESCO1-mediated SMC3 acetylation, generating a 'braked' state that pauses loop enlargement, whereas HDAC8-dependent deacetylation releases this brake to restart extrusion—a loop-length control distinct from the canonical WAPL-mediated DNA release pathway [PMID:35710836]. PDS5A also supports cohesin unloading, and its loss produces aberrant cohesin activity, ectopic insulation, and disruption of ultra-long Polycomb loops required for robust PRC1/PRC2 target silencing [PMID:38071364]. PDS5A and its paralog PDS5B have overlapping roles in facilitating SMC3 acetylation while retaining non-redundant functions in cohesin removal [PMID:32760717], and act cooperatively in vivo to constrain loop extrusion during development [PMID:41994921]. Beyond chromatin, PDS5A has a cohesion-independent role in meiotic spindle assembly, localizing to spindle fibers in mouse oocytes where it recruits the deubiquitinase USP14 to stabilize KIF5B and regulate spindle elongation [PMID:40215310].","teleology":[{"year":2007,"claim":"An early attempt to assign PDS5A a function linked it to a p63-dependent proliferative role, raising the possibility of activity outside cohesin biology.","evidence":"Co-immunoprecipitation, overexpression/knockdown, proliferation and cell-cycle assays in human cells","pmids":["17846787"],"confidence":"Low","gaps":["Single Co-IP without reciprocal validation or in vitro confirmation","No connection drawn to cohesin or loop architecture","p63 link not corroborated by later mechanistic work"]},{"year":2020,"claim":"To resolve whether PDS5A and PDS5B are redundant in cohesin regulation, paralog depletion experiments showed they cooperate in SMC3 acetylation yet retain non-redundant roles in cohesin removal and checkpoint control.","evidence":"siRNA single and co-depletion, acetyl-SMC3 western blot, WAPL/MAD2 immunofluorescence, Chk1-inhibitor rescue in human cells","pmids":["32760717"],"confidence":"Medium","gaps":["Mechanism of how PDS5A facilitates SMC3 acetylation not defined","Performed in perturbed cell cycle, leaving steady-state role unclear","Does not address loop-level architectural consequences"]},{"year":2022,"claim":"The question of how acetylation cycles control loop length was answered by showing ESCO1-driven SMC3 acetylation promotes a PDS5A-bound braked state that pauses extrusion, reversibly released by HDAC8.","evidence":"Hi-C, ChIP-seq, auxin-inducible degron depletion of ESCO1/HDAC8 in human cells","pmids":["35710836"],"confidence":"High","gaps":["Structural basis of the braked PDS5A–cohesin state not resolved","Relationship between braking and NIPBL dissociation not yet connected","Quantitative kinetics of pause/restart unmeasured in vivo"]},{"year":2023,"claim":"To place PDS5A in gene-regulatory architecture, its deletion was shown to impair cohesin unloading and disrupt ultra-long Polycomb loops, defining a role in maintaining genome organization needed for Polycomb silencing.","evidence":"CRISPR screen, PDS5A deletion, Hi-C, RNA-seq, ChIP-seq in mouse ESCs","pmids":["38071364"],"confidence":"High","gaps":["How loss of unloading mechanistically derepresses only a subset of targets unclear","Direct biochemical link between PDS5A and Polycomb machinery not established","Polycomb chromatin domains persist, decoupling silencing from domain identity"]},{"year":2025,"claim":"The biochemical mechanism by which PDS5 stops loop extrusion was directly resolved: PDS5 facilitates NIPBL dissociation from cohesin, limiting cohesin–NIPBL lifetime and enabling CTCF boundary establishment.","evidence":"In vitro single-molecule imaging of loop extrusion, Hi-C, polymer modelling (preprint)","pmids":["bio_10.1101_2025.08.30.673243"],"confidence":"High","gaps":["Awaits peer review","How NIPBL dissociation integrates with the acetylation-dependent braked state not unified","Paralog-specific contributions in the reconstituted system not separated"]},{"year":2025,"claim":"PDS5A was assigned a discrete role in CTCF boundary mechanics, tuning CTCF's conformational ensemble before cohesin engagement and reinforcing loop-anchor stability after binding.","evidence":"Single-molecule imaging of CTCF dynamics and in vitro CTCF–cohesin–PDS5A reconstitution with mechanical stability assays (preprint)","pmids":["bio_10.1101_2025.11.25.690553"],"confidence":"Medium","gaps":["Preprint, single lab, not independently replicated","In vivo relevance of CTCF conformational tuning not demonstrated","Structural detail of PDS5A–CTCF contact undefined"]},{"year":2025,"claim":"A cohesion-independent function emerged: in oocytes PDS5A localizes to the meiotic spindle and recruits USP14 to deubiquitinate and stabilize KIF5B, controlling spindle elongation.","evidence":"Morpholino depletion plus genetic knockout in mouse oocytes, immunofluorescence, Co-IP, ubiquitination assay","pmids":["40215310"],"confidence":"High","gaps":["How PDS5A is targeted to the spindle is unknown","Whether this function generalizes beyond meiotic oocytes unclear","Structural basis of PDS5A–USP14 interaction undefined"]},{"year":2026,"claim":"PDS5A's partnership with the topoisomerase TOP2B at CTCF boundaries was defined, with a CTCF N-terminal region (aa 95–116) required for the CTCF–PDS5A–TOP2B interaction.","evidence":"In vitro binding with CTCF deletion mutants, ChIP-seq, inducible PDS5A knockdown, Hi-C (preprint)","pmids":["41959374"],"confidence":"Medium","gaps":["Preprint, not peer reviewed","Functional consequence of TOP2B catalytic activity on loop dynamics not fully resolved","How this interaction relates to the braked/NIPBL-dissociation mechanisms unclear"]},{"year":2026,"claim":"In vivo developmental relevance was confirmed by showing Pds5a and Pds5b cooperatively constrain loop extrusion in medaka embryos, with phenotypes only on double depletion.","evidence":"Morpholino depletion in medaka embryos, in situ Hi-C, RNA-seq","pmids":["41994921"],"confidence":"Medium","gaps":["Single vs double depletion does not separate paralog-specific roles","Developmental phenotypes downstream of loop changes not characterized","Single lab in one model organism"]},{"year":null,"claim":"How the distinct PDS5A activities—NIPBL dissociation, acetylation-dependent braking, cohesin unloading, CTCF/TOP2B boundary cooperation, and meiotic spindle regulation—are coordinated within a unified molecular framework remains unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No structural model integrating the braked, NIPBL-dissociating, and CTCF-stabilizing states","Switch between chromatin and spindle functions uncharacterized","Quantitative partitioning of PDS5A vs PDS5B in each activity undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,6]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[0,1]}],"localization":[{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[0,1]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[2]}],"complexes":["cohesin complex"],"partners":["NIPBL","CTCF","TOP2B","USP14","KIF5B","PDS5B","WAPL"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q29RF7","full_name":"Sister chromatid cohesion protein PDS5 homolog A","aliases":["Cell proliferation-inducing gene 54 protein","Sister chromatid cohesion protein 112","SCC-112"],"length_aa":1337,"mass_kda":150.8,"function":"Probable regulator of sister chromatid cohesion in mitosis which may stabilize cohesin complex association with chromatin. May couple sister chromatid cohesion during mitosis to DNA replication. Cohesion ensures that chromosome partitioning is accurate in both meiotic and mitotic cells and plays an important role in DNA repair","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q29RF7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PDS5A","classification":"Not Classified","n_dependent_lines":367,"n_total_lines":1208,"dependency_fraction":0.3038079470198676},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"STAG2","stoichiometry":10.0},{"gene":"SMC1A","stoichiometry":4.0}],"url":"https://opencell.sf.czbiohub.org/search/PDS5A","total_profiled":1310},"omim":[{"mim_id":"613203","title":"DNA REPLICATION AND SISTER CHROMATID COHESION 1; DSCC1","url":"https://www.omim.org/entry/613203"},{"mim_id":"613202","title":"CHROMOSOME TRANSMISSION FIDELITY FACTOR 8; CHTF8","url":"https://www.omim.org/entry/613202"},{"mim_id":"613201","title":"CHROMOSOME TRANSMISSION FIDELITY FACTOR 18; CHTF18","url":"https://www.omim.org/entry/613201"},{"mim_id":"613200","title":"PDS5 COHESIN-ASSOCIATED FACTOR A; PDS5A","url":"https://www.omim.org/entry/613200"},{"mim_id":"610754","title":"WAPL COHESIN RELEASE FACTOR; WAPL","url":"https://www.omim.org/entry/610754"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Nucleoplasm","reliability":"Enhanced"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/PDS5A"},"hgnc":{"alias_symbol":["KIAA0648","PIG54","SCC-112"],"prev_symbol":[]},"alphafold":{"accession":"Q29RF7","domains":[{"cath_id":"-","chopping":"22-162","consensus_level":"medium","plddt":91.1931,"start":22,"end":162},{"cath_id":"-","chopping":"519-619","consensus_level":"medium","plddt":89.9988,"start":519,"end":619},{"cath_id":"-","chopping":"958-1133","consensus_level":"high","plddt":88.2764,"start":958,"end":1133}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q29RF7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q29RF7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q29RF7-F1-predicted_aligned_error_v6.png","plddt_mean":81.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PDS5A","jax_strain_url":"https://www.jax.org/strain/search?query=PDS5A"},"sequence":{"accession":"Q29RF7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q29RF7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q29RF7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q29RF7"}},"corpus_meta":[{"pmid":"35710836","id":"PMC_35710836","title":"The cohesin acetylation cycle controls chromatin loop length through a PDS5A brake mechanism.","date":"2022","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/35710836","citation_count":59,"is_preprint":false},{"pmid":"34070827","id":"PMC_34070827","title":"PDS5A and PDS5B in Cohesin Function and Human Disease.","date":"2021","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/34070827","citation_count":35,"is_preprint":false},{"pmid":"15019998","id":"PMC_15019998","title":"SCC-112, a novel cell cycle-regulated molecule, exhibits reduced expression in human renal carcinomas.","date":"2004","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/15019998","citation_count":20,"is_preprint":false},{"pmid":"38071364","id":"PMC_38071364","title":"Loss of cohesin regulator PDS5A reveals repressive role of Polycomb loops.","date":"2023","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/38071364","citation_count":14,"is_preprint":false},{"pmid":"17846787","id":"PMC_17846787","title":"SCC-112 gene is involved in tumor progression and promotes the cell proliferation in G2/M phase.","date":"2007","source":"Journal of cancer research and clinical oncology","url":"https://pubmed.ncbi.nlm.nih.gov/17846787","citation_count":14,"is_preprint":false},{"pmid":"32760717","id":"PMC_32760717","title":"Pds5A and Pds5B Display Non-redundant Functions in Mitosis and Their Loss Triggers Chk1 Activation.","date":"2020","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/32760717","citation_count":7,"is_preprint":false},{"pmid":"35506437","id":"PMC_35506437","title":"Knockdown of CDCA5 suppresses malignant progression of breast cancer cells by regulating PDS5A.","date":"2022","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/35506437","citation_count":6,"is_preprint":false},{"pmid":"40215310","id":"PMC_40215310","title":"The cohesin-associated protein Pds5A governs the meiotic spindle assembly via deubiquitination of Kif5B in oocytes.","date":"2025","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/40215310","citation_count":3,"is_preprint":false},{"pmid":"21865657","id":"PMC_21865657","title":"HIV-1 infection suppresses expression of host cell cycle-associated gene PDS5A.","date":"2011","source":"Intervirology","url":"https://pubmed.ncbi.nlm.nih.gov/21865657","citation_count":3,"is_preprint":false},{"pmid":"41959374","id":"PMC_41959374","title":"PDS5A and TOP2B cooperate for chromatin recruitment via CTCF.","date":"2026","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/41959374","citation_count":0,"is_preprint":false},{"pmid":"41994921","id":"PMC_41994921","title":"Cooperative Roles of Pds5a and Pds5b Constrain Long-Range Chromatin Interactions in Vertebrate Embryos.","date":"2026","source":"Development, growth & differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/41994921","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.08.30.673243","title":"PDS5 proteins control genome architecture by limiting the lifetime of cohesin-NIPBL complexes","date":"2025-08-30","source":"bioRxiv","url":"https://doi.org/10.1101/2025.08.30.673243","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.11.25.690553","title":"Chromatin boundary permeability is controlled by CTCF conformational ensembles","date":"2025-11-29","source":"bioRxiv","url":"https://doi.org/10.1101/2025.11.25.690553","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7882,"output_tokens":2452,"usd":0.030213,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9630,"output_tokens":3460,"usd":0.067325,"stage2_stop_reason":"end_turn"},"total_usd":0.097538,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2022,\n      \"finding\": \"Cohesin acetylation by ESCO1 restricts chromatin loop length and architectural stripes by promoting PDS5A binding to cohesin, which acts as a brake enabling pausing and restart of loop enlargement; HDAC8-mediated deacetylation promotes loop extension by releasing this PDS5A-bound braked state. This role in loop-length control is distinct from the canonical WAPL-mediated DNA release pathway.\",\n      \"method\": \"Hi-C, ChIP-seq, auxin-inducible degron depletion of ESCO1/HDAC8, functional genomics in human cells\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal genomic and functional methods (Hi-C, ChIP-seq, protein depletion), mechanistic model supported by genetic epistasis between acetylation cycle components and PDS5A\",\n      \"pmids\": [\"35710836\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PDS5A loss impairs cohesin unloading, causing aberrant cohesin activity that generates ectopic insulation sites and disrupts ultra-long Polycomb loops, which are required for robust silencing of a subset of PRC1/PRC2 target genes; derepression occurs without loss of Polycomb chromatin domains, placing PDS5A as a cohesin unloading regulator whose activity maintains genome architecture needed for Polycomb gene silencing.\",\n      \"method\": \"CRISPR screen in mouse ESCs, PDS5A deletion, Hi-C, RNA-seq, ChIP-seq\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function with multiple orthogonal genomic readouts (Hi-C, RNA-seq, ChIP-seq) defining pathway position\",\n      \"pmids\": [\"38071364\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Depletion of Pds5A or Pds5B individually increased SMC3 acetylation in perturbed cell cycle, whereas co-depletion of both severely impaired SMC3 acetylation, demonstrating overlapping roles in facilitating SMC3 acetylation. Additionally, Pds5A/B loss stabilized WAPL on chromatin and activated the spindle assembly checkpoint via an ATR-Chk1-dependent mechanism, revealing non-redundant functions in cohesin removal.\",\n      \"method\": \"siRNA knockdown, western blot for acetyl-SMC3, immunofluorescence for MAD2/WAPL, flow cytometry, Chk1 inhibitor rescue\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean knockdown with defined molecular readouts (SMC3 acetylation, WAPL chromatin binding), single lab, two orthogonal methods\",\n      \"pmids\": [\"32760717\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Pds5A localizes to spindle fibers in mouse oocytes at metaphase I and II and plays a non-canonical, cohesion-independent role in meiotic spindle assembly. Mechanistically, Pds5A recruits the deubiquitinase USP14 to the spindle apparatus, which stabilizes kinesin family member KIF5B by deubiquitination, thereby regulating spindle elongation.\",\n      \"method\": \"Morpholino depletion, genetic knockout in mouse oocytes, immunofluorescence, co-immunoprecipitation, ubiquitination assay\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic ablation plus Co-IP identifying USP14 as recruited factor, ubiquitination assay for KIF5B stabilization, replicated by two depletion strategies (morpholino and KO)\",\n      \"pmids\": [\"40215310\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"SCC-112/PDS5A protein was found to interact with p63 by co-immunoprecipitation, and overexpression of SCC-112 up-regulated p63 expression, promoting cell proliferation in G2/M phase.\",\n      \"method\": \"Co-immunoprecipitation, overexpression/siRNA knockdown, MTT proliferation assay, FACS cell cycle analysis\",\n      \"journal\": \"Journal of cancer research and clinical oncology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP from a single lab, no reciprocal validation or in vitro confirmation\",\n      \"pmids\": [\"17846787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"PDS5A interacts with TOP2B and CTCF; a novel CTCF N-terminal region (amino acids 95–116) is required for the CTCF–PDS5A–TOP2B interaction in vitro and for TOP2B-mediated enrichment of PDS5A chromatin occupancy in vivo. Catalytically active TOP2B increases PDS5A occupancy genome-wide, and PDS5A knockdown reduces TOP2B chromatin occupancy and alters gene expression.\",\n      \"method\": \"In vitro binding assay with CTCF deletion mutants, ChIP-seq, inducible PDS5A knockdown, chromatin loop analysis by Hi-C\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro interaction mapping with mutagenesis plus ChIP-seq in vivo, single lab, preprint not yet peer-reviewed\",\n      \"pmids\": [\"41959374\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PDS5 proteins stop cohesin-mediated loop extrusion by facilitating dissociation of NIPBL from cohesin, as demonstrated by in vitro single-molecule imaging; this mechanism limits cohesin-NIPBL lifetime and is required for establishment of CTCF boundaries and maintenance of chromatin compartmentalization.\",\n      \"method\": \"In vitro single-molecule imaging, Hi-C, in silico polymer modelling\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro single-molecule reconstitution of loop extrusion with and without PDS5, corroborated by Hi-C and computational modelling\",\n      \"pmids\": [\"bio_10.1101_2025.08.30.673243\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PDS5A tunes the conformational ensemble of CTCF before cohesin engagement, influencing the probability that cohesin stalls at CTCF boundaries; upon cohesin binding, PDS5A enhances the mechanical stability of loop anchors, reinforcing orientation-dependent boundaries.\",\n      \"method\": \"Single-molecule imaging of CTCF conformational dynamics, in vitro cohesin–CTCF–PDS5A reconstitution, mechanical stability assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro reconstitution with mechanistic insight, but single lab and preprint; novel claim not yet replicated\",\n      \"pmids\": [\"bio_10.1101_2025.11.25.690553\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"In medaka embryos, simultaneous depletion of both Pds5a and Pds5b, but not single depletion, caused pronounced increases in long-range chromatin contacts and de novo formation of extended chromatin loops by Hi-C, demonstrating that Pds5a and Pds5b act cooperatively to constrain cohesin-mediated loop extrusion in vivo during development.\",\n      \"method\": \"Morpholino-mediated depletion in medaka embryos, in situ Hi-C, RNA-seq\",\n      \"journal\": \"Development, growth & differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo Hi-C with genetic epistasis (single vs double depletion), single lab\",\n      \"pmids\": [\"41994921\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PDS5A is a regulatory subunit of the cohesin complex that controls chromatin loop length and genome organization by: (1) acting as a NIPBL-dissociation factor that stops loop extrusion in vitro; (2) occupying a cohesin-bound 'braked' state promoted by SMC3 acetylation (via ESCO1) to pause loop enlargement, with HDAC8-mediated deacetylation restarting extrusion; (3) cooperating with TOP2B at CTCF-bound chromatin boundaries, where a CTCF N-terminal region (aa 95–116) is required for their interaction; (4) maintaining cohesin unloading to preserve ultra-long Polycomb loops required for gene silencing; and (5) recruiting USP14 deubiquitinase to the meiotic spindle for KIF5B stabilization, revealing a non-canonical spindle-regulatory function in oocytes.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PDS5A is a regulatory subunit of the cohesin complex that constrains cohesin-mediated DNA loop extrusion to shape three-dimensional genome architecture [#0, #6]. Mechanistically, it acts as a NIPBL-dissociation factor that limits the cohesin–NIPBL lifetime, halting loop extrusion and enabling establishment of CTCF boundaries and chromatin compartmentalization [#6]. PDS5A binding to cohesin is promoted by ESCO1-mediated SMC3 acetylation, generating a 'braked' state that pauses loop enlargement, whereas HDAC8-dependent deacetylation releases this brake to restart extrusion—a loop-length control distinct from the canonical WAPL-mediated DNA release pathway [#0]. PDS5A also supports cohesin unloading, and its loss produces aberrant cohesin activity, ectopic insulation, and disruption of ultra-long Polycomb loops required for robust PRC1/PRC2 target silencing [#1]. PDS5A and its paralog PDS5B have overlapping roles in facilitating SMC3 acetylation while retaining non-redundant functions in cohesin removal [#2], and act cooperatively in vivo to constrain loop extrusion during development [#8]. Beyond chromatin, PDS5A has a cohesion-independent role in meiotic spindle assembly, localizing to spindle fibers in mouse oocytes where it recruits the deubiquitinase USP14 to stabilize KIF5B and regulate spindle elongation [#3].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"An early attempt to assign PDS5A a function linked it to a p63-dependent proliferative role, raising the possibility of activity outside cohesin biology.\",\n      \"evidence\": \"Co-immunoprecipitation, overexpression/knockdown, proliferation and cell-cycle assays in human cells\",\n      \"pmids\": [\"17846787\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single Co-IP without reciprocal validation or in vitro confirmation\", \"No connection drawn to cohesin or loop architecture\", \"p63 link not corroborated by later mechanistic work\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"To resolve whether PDS5A and PDS5B are redundant in cohesin regulation, paralog depletion experiments showed they cooperate in SMC3 acetylation yet retain non-redundant roles in cohesin removal and checkpoint control.\",\n      \"evidence\": \"siRNA single and co-depletion, acetyl-SMC3 western blot, WAPL/MAD2 immunofluorescence, Chk1-inhibitor rescue in human cells\",\n      \"pmids\": [\"32760717\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of how PDS5A facilitates SMC3 acetylation not defined\", \"Performed in perturbed cell cycle, leaving steady-state role unclear\", \"Does not address loop-level architectural consequences\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"The question of how acetylation cycles control loop length was answered by showing ESCO1-driven SMC3 acetylation promotes a PDS5A-bound braked state that pauses extrusion, reversibly released by HDAC8.\",\n      \"evidence\": \"Hi-C, ChIP-seq, auxin-inducible degron depletion of ESCO1/HDAC8 in human cells\",\n      \"pmids\": [\"35710836\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the braked PDS5A–cohesin state not resolved\", \"Relationship between braking and NIPBL dissociation not yet connected\", \"Quantitative kinetics of pause/restart unmeasured in vivo\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"To place PDS5A in gene-regulatory architecture, its deletion was shown to impair cohesin unloading and disrupt ultra-long Polycomb loops, defining a role in maintaining genome organization needed for Polycomb silencing.\",\n      \"evidence\": \"CRISPR screen, PDS5A deletion, Hi-C, RNA-seq, ChIP-seq in mouse ESCs\",\n      \"pmids\": [\"38071364\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How loss of unloading mechanistically derepresses only a subset of targets unclear\", \"Direct biochemical link between PDS5A and Polycomb machinery not established\", \"Polycomb chromatin domains persist, decoupling silencing from domain identity\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"The biochemical mechanism by which PDS5 stops loop extrusion was directly resolved: PDS5 facilitates NIPBL dissociation from cohesin, limiting cohesin–NIPBL lifetime and enabling CTCF boundary establishment.\",\n      \"evidence\": \"In vitro single-molecule imaging of loop extrusion, Hi-C, polymer modelling (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.08.30.673243\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Awaits peer review\", \"How NIPBL dissociation integrates with the acetylation-dependent braked state not unified\", \"Paralog-specific contributions in the reconstituted system not separated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"PDS5A was assigned a discrete role in CTCF boundary mechanics, tuning CTCF's conformational ensemble before cohesin engagement and reinforcing loop-anchor stability after binding.\",\n      \"evidence\": \"Single-molecule imaging of CTCF dynamics and in vitro CTCF–cohesin–PDS5A reconstitution with mechanical stability assays (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.11.25.690553\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, single lab, not independently replicated\", \"In vivo relevance of CTCF conformational tuning not demonstrated\", \"Structural detail of PDS5A–CTCF contact undefined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"A cohesion-independent function emerged: in oocytes PDS5A localizes to the meiotic spindle and recruits USP14 to deubiquitinate and stabilize KIF5B, controlling spindle elongation.\",\n      \"evidence\": \"Morpholino depletion plus genetic knockout in mouse oocytes, immunofluorescence, Co-IP, ubiquitination assay\",\n      \"pmids\": [\"40215310\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How PDS5A is targeted to the spindle is unknown\", \"Whether this function generalizes beyond meiotic oocytes unclear\", \"Structural basis of PDS5A–USP14 interaction undefined\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"PDS5A's partnership with the topoisomerase TOP2B at CTCF boundaries was defined, with a CTCF N-terminal region (aa 95–116) required for the CTCF–PDS5A–TOP2B interaction.\",\n      \"evidence\": \"In vitro binding with CTCF deletion mutants, ChIP-seq, inducible PDS5A knockdown, Hi-C (preprint)\",\n      \"pmids\": [\"41959374\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not peer reviewed\", \"Functional consequence of TOP2B catalytic activity on loop dynamics not fully resolved\", \"How this interaction relates to the braked/NIPBL-dissociation mechanisms unclear\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"In vivo developmental relevance was confirmed by showing Pds5a and Pds5b cooperatively constrain loop extrusion in medaka embryos, with phenotypes only on double depletion.\",\n      \"evidence\": \"Morpholino depletion in medaka embryos, in situ Hi-C, RNA-seq\",\n      \"pmids\": [\"41994921\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single vs double depletion does not separate paralog-specific roles\", \"Developmental phenotypes downstream of loop changes not characterized\", \"Single lab in one model organism\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the distinct PDS5A activities—NIPBL dissociation, acetylation-dependent braking, cohesin unloading, CTCF/TOP2B boundary cooperation, and meiotic spindle regulation—are coordinated within a unified molecular framework remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural model integrating the braked, NIPBL-dissociating, and CTCF-stabilizing states\", \"Switch between chromatin and spindle functions uncharacterized\", \"Quantitative partitioning of PDS5A vs PDS5B in each activity undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 6]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"complexes\": [\"cohesin complex\"],\n    \"partners\": [\"NIPBL\", \"CTCF\", \"TOP2B\", \"USP14\", \"KIF5B\", \"PDS5B\", \"WAPL\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}