{"gene":"PRC1","run_date":"2026-04-28T19:45:44","timeline":{"discoveries":[{"year":1998,"finding":"PRC1 (protein regulator of cytokinesis 1) is a substrate for CDKs in vitro and is phosphorylated in vivo at CDK consensus sites; it localizes to the nucleus in interphase, associates dynamically with mitotic spindles during mitosis, and localizes to the midbody during cytokinesis. Microinjection of anti-PRC1 antibodies blocked cellular cleavage but not nuclear division, establishing a direct role in cytokinesis.","method":"In vitro kinase assay, in vivo phosphorylation, microinjection of inhibitory antibodies, immunolocalization","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (kinase assay, antibody microinjection, localization) in a single foundational study","pmids":["9885575"],"is_preprint":false},{"year":2002,"finding":"PRC1 binds and bundles microtubules both in vivo and in vitro; CDK phosphorylation suppresses its bundling activity during mitosis (a phosphorylation-null mutant causes aberrant prometaphase bundling); siRNA depletion abolishes microtubule interdigitation and the spindle midzone. The NH2-terminal region is required for localization to the cleavage furrow and midbody center, whereas the central region is required for microtubule binding and bundling.","method":"siRNA knockdown, overexpression of truncation/phosphorylation-null mutants, in vitro microtubule bundling assay, immunofluorescence","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1-2 — reconstituted bundling in vitro plus mutagenesis and siRNA with clear phenotypic readout, highly cited","pmids":["12082078"],"is_preprint":false},{"year":2013,"finding":"PRC1 and kinesin-4 (Kif4A) cooperate to tag microtubule plus ends in a length-dependent manner in vitro and in dividing cells. The crystal structure of the PRC1 homodimer was determined and protein-protein interactions required for microtubule plus-end tagging were mapped.","method":"In vitro reconstitution, crystal structure determination, live-cell imaging, structure-guided mutagenesis","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 — crystal structure plus reconstitution and in vivo validation with multiple orthogonal approaches","pmids":["23870126"],"is_preprint":false},{"year":2018,"finding":"CDK16 (in complex with Cyclin Y) phosphorylates PRC1 at Thr481; specific inhibition of CDK16 causes PRC1 dephosphorylation at this site and its delocalization to the nucleus during interphase. CDK16 inhibition and PRC1 downregulation show epistatic effects on cell viability, placing them in the same pathway.","method":"Analog-sensitive CDK16 generated by CRISPR-Cas9, proteomic substrate identification, phosphosite mapping, epistasis analysis","journal":"Experimental & molecular medicine","confidence":"High","confidence_rationale":"Tier 1-2 — analog-sensitive kinase approach with direct phosphosite identification and epistasis, moderate evidence","pmids":["30992425"],"is_preprint":false},{"year":2022,"finding":"CDK16 phosphorylates PRC1 to regulate spindle formation during mitosis in triple-negative breast cancer cells; CDK16 knockdown or pharmacological inhibition leads to mitotic spindle defects consistent with PRC1 dysfunction.","method":"Genetic knockdown, pharmacological inhibition, xenograft and organoid models, transcriptomic analysis","journal":"Journal of experimental & clinical cancer research","confidence":"Medium","confidence_rationale":"Tier 2 — mechanistic follow-up confirming CDK16-PRC1 phosphorylation axis in a cancer model, single lab","pmids":["35449080"],"is_preprint":false},{"year":2020,"finding":"PRC1 acts as a mechanical dashpot (velocity-dependent friction generator) when crosslinking antiparallel microtubules: frictional forces scale with microtubule sliding velocity and number of PRC1 crosslinks, but not overlap length or PRC1 density within overlaps.","method":"Simultaneous optical trapping and TIRF microscopy in vitro","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 1 — direct in vitro biophysical reconstitution with quantitative force measurements","pmids":["32640202"],"is_preprint":false},{"year":2016,"finding":"In metaphase spindles, PRC1-GFP-labeled overlap (bridging) bundles show one-to-one association with kinetochore pairs (>90% of overlap bundles bridge sister k-fibers); PRC1 knockdown reduces bridging fiber thickness and interkinetochore distance, demonstrating PRC1's role in spindle force balance.","method":"Live-cell imaging with PRC1-GFP, siRNA knockdown, endogenous PRC1 immunolocalization, quantitative analysis","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 — multiple imaging approaches with functional perturbation and quantitative readouts","pmids":["28028032"],"is_preprint":false},{"year":2018,"finding":"The geometry of antiparallel microtubule arrays regulates PRC1-Kif4A activity: sliding velocity scales with initial microtubule overlap length, and final overlap width scales with microtubule length. PRC1 and Kif4A accumulate at microtubule plus-ends forming 'end-tags,' and sliding stalls when opposing end-tags collide.","method":"In vitro reconstitution with fluorescently labeled proteins, TIRF microscopy","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with quantitative analysis of geometry-dependent regulation","pmids":["30353849"],"is_preprint":false},{"year":2021,"finding":"PLK1 activates PRC1 to promote cytokinesis; the EWSR1-FLI1 oncogenic transcription factor hijacks PRC1 via binding to a proximal GGAA-microsatellite enhancer, driving high PRC1 expression. PLK1 inhibition in PRC1-overexpressing Ewing sarcoma triggers mitotic catastrophe and tumor regression.","method":"CRISPR-mediated enhancer editing, in vitro and in vivo functional experiments, transcriptome profiling","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 — CRISPR enhancer editing plus functional rescue, single study","pmids":["34531368"],"is_preprint":false},{"year":2020,"finding":"PRC1 is required for anaphase spindle midzone and midbody formation during mouse oocyte meiosis I; KIF4A co-localizes with PRC1 at the midzone, and KIF4A depletion disrupts PRC1 expression and localization, placing KIF4A upstream of PRC1 in midzone assembly during meiosis.","method":"siRNA knockdown, immunofluorescence localization, mRNA rescue injection, mouse oocyte model","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 2 — knockdown with rescue and defined phenotypic readout, single lab","pmids":["33206458"],"is_preprint":false},{"year":2017,"finding":"ZFP36 binds to AU-rich elements in the 3'UTR of PRC1 mRNA to downregulate PRC1 protein expression; this post-transcriptional regulation by ZFP36 suppresses PRC1-mediated promotion of cell proliferation in hepatocellular carcinoma.","method":"Luciferase reporter assay, ribonucleoprotein immunoprecipitation, overexpression and knockdown","journal":"Frontiers in molecular biosciences","confidence":"Medium","confidence_rationale":"Tier 2-3 — RIP and reporter assay demonstrating direct mRNA binding, single lab","pmids":["32766276"],"is_preprint":false},{"year":2014,"finding":"PRC1 crystal structure of the homodimer was determined (as part of the Subramanian et al. 2013 study), mapping the spectrin-like fold and identifying interaction surfaces required for antiparallel microtubule crosslinking and kinesin-4 co-recruitment.","method":"X-ray crystallography, in vitro reconstitution, structure-guided mutagenesis","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with functional validation via mutagenesis and reconstitution","pmids":["23870126"],"is_preprint":false},{"year":1997,"finding":"The budding yeast ortholog Ase1 (PRC1 family) undergoes APC/cyclosome-mediated proteolysis when cells exit mitosis and enter G1; stable non-degradable Ase1 delays spindle disassembly and causes a spindle defect sensed by the spindle assembly checkpoint, establishing APC-mediated proteolysis as a regulator of spindle assembly and disassembly.","method":"Genetic analysis, cell-cycle-specific degradation assays, expression of non-degradable mutant","journal":"Science","confidence":"High","confidence_rationale":"Tier 1-2 — genetic epistasis with non-degradable mutant and checkpoint readout, highly cited","pmids":["9036857"],"is_preprint":false},{"year":2005,"finding":"Fission yeast Ase1 (PRC1 ortholog) localizes to microtubule overlapping zones and is a dose-dependent microtubule-bundling factor; its absence causes spindle collapse during anaphase B, and Aurora kinase fails to localize to central spindles without Ase1. Ase1 also acts as a regulatory component in the cytokinesis checkpoint.","method":"Gene deletion, time-lapse imaging, overexpression analysis, genetic epistasis","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal approaches in a model organism ortholog study","pmids":["15647375"],"is_preprint":false},{"year":2020,"finding":"In budding yeast, the Ase1 spectrin domain promotes midzone recruitment before anaphase onset and slows early spindle elongation via conserved basic residues; the carboxy-terminal domain interacts with and recruits EB1/Bim1 to the midzone to maintain midzone length during late anaphase.","method":"Domain truncation and mutagenesis, live-cell imaging, protein interaction assays","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 — structure-function mutagenesis with live imaging and interaction assays, single lab","pmids":["32997572"],"is_preprint":false},{"year":2019,"finding":"In fission yeast, Ase1 (PRC1 ortholog) is required for bipolar spindle assembly in the absence of kinesin-5 by recruiting CLASP/Cls1 to stabilize microtubules; Brownian dynamics simulations confirm that Ase1 and Cls1 activity are sufficient for initial bipolar spindle formation via microtubule polymerization forces.","method":"Genetic epistasis, live-cell imaging, computational modeling","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis with simulation support, single lab","pmids":["28513584"],"is_preprint":false},{"year":2014,"finding":"Replication stress in budding yeast induces intragenic transcription of ASE1, producing shorter protein isoforms that localize to the spindle and antagonize full-length Ase1 at the midzone, stabilizing the S-phase spindle by downregulating full-length Ase1 crosslinking activity.","method":"Biochemical characterization of short isoforms, overexpression, live-cell imaging, genetic analysis","journal":"Current biology","confidence":"Medium","confidence_rationale":"Tier 2 — mechanistic follow-up with multiple assays, single lab","pmids":["24768052"],"is_preprint":false},{"year":2024,"finding":"Canonical PRC1 (the Polycomb epigenetic complex) forms condensates synergistically with nucleosomal arrays (reducing critical concentration >20-fold); CBX subunit composition determines condensate initiation, and PHC2's polymerization activity promotes distinct adherent domain formation that does not coalesce. Live-cell imaging confirms CBX drives initiation and PHC drives stability.","method":"In vitro reconstitution with single-molecule imaging, live-cell imaging, genetic perturbation of specific subunits","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 — reconstitution plus single-molecule imaging plus live-cell validation with subunit-specific perturbations","pmids":["38521066"],"is_preprint":false},{"year":2014,"finding":"Crystal structure of the human Ring1B-Bmi1-UbcH5c PRC1 ubiquitylation module bound to the nucleosome core particle reveals that PRC1 achieves substrate specificity by contacting multiple nucleosome surfaces distinct from the catalytic site, and reveals an unexpected role for the E2 enzyme UbcH5c in substrate recognition for H2A Lys119 ubiquitylation.","method":"X-ray crystallography of PRC1-nucleosome complex","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — high-resolution crystal structure of the catalytic complex with substrate, highly cited","pmids":["25355358"],"is_preprint":false},{"year":2016,"finding":"RYBP/YAF2 stimulates the H2AK119 E3 ubiquitin ligase activity of PRC1; RYBP shapes H2AK119 mono-ubiquitylation at PcG targets and underpins activity-based communication between PRC1 and PRC2 required for normal H3K27me3. Loss of RYBP erodes repressive Polycomb chromatin domains.","method":"Mouse ESC genetic perturbation, quantitative genomics, ChIP-seq","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 — genetic perturbation with genome-wide quantitative analysis, multiple supporting findings","pmids":["27705745"],"is_preprint":false},{"year":2012,"finding":"Recombinant PRC1 (Polycomb complex) inhibits transcription on H3K27-methylated chromatin templates by blocking recruitment of Mediator and dissociating preassembled preinitiation complexes, while leaving TBP/TFIID relatively intact, defining a specific biochemical mechanism for PRC1-mediated transcriptional silencing.","method":"In vitro transcription reconstitution on immobilized chromatin templates, purified recombinant PRC1","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with purified components defining mechanistic step","pmids":["22910904"],"is_preprint":false},{"year":2021,"finding":"Rapid degron-based depletion of PRC1 (Polycomb complex) shows it functions independently of PRC2 to counteract RNA Pol II binding and transcription initiation; single-cell analysis reveals PRC1 controls transcriptional burst frequency uniformly across the cell population.","method":"Auxin-inducible degron (rapid depletion), time-resolved ChIP-seq and RNA-seq, single-cell gene expression analysis","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1-2 — rapid degron approach with kinetic genomics and single-cell analysis, multiple orthogonal readouts","pmids":["34608337"],"is_preprint":false},{"year":2020,"finding":"RYBP and YAF2 each specifically bind H2AK119ub1 to recruit RYBP-PRC1 or YAF2-PRC1 and catalyze ubiquitination of neighboring nucleosomes via a positive-feedback model; histone H1-compacted chromatin enhances distal propagation of H2AK119ub1, contributing to epigenetic inheritance during cell division.","method":"Biochemical binding assays, reconstitution, genetic disruption, chromatin fractionation","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 1-2 — direct binding assays plus reconstitution demonstrating positive feedback, multiple orthogonal approaches","pmids":["32203418"],"is_preprint":false},{"year":2017,"finding":"hnRNPK is the principal RNA-binding protein that binds the Xist B-repeat-containing Polycomb Interaction Domain (XR-PID) and recruits PCGF3/5-PRC1 to initiate chromosome-wide H2AK119ub1 and subsequent PRC2 recruitment; synthetic tethering of hnRNPK to Xist lacking XR-PID is sufficient to restore Polycomb recruitment.","method":"RNA deletion mapping, RNA pulldown, synthetic tethering, genetic deletion, ChIP-seq","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods including synthetic rescue, defining molecular pathway","pmids":["29220657"],"is_preprint":false},{"year":2017,"finding":"PCGF3/5-PRC1 initiates Polycomb recruitment in X chromosome inactivation; it catalyzes H2AK119ub1 chromosome-wide, which signals recruitment of other PRC1 complexes and PRC2, the latter leading to H3K27me3 deposition. Pcgf3/5 knockout results in female-specific embryo lethality and abrogates Xist-mediated gene repression.","method":"Conditional knockout, ChIP-seq, immunofluorescence, RNA-seq","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 — genetic knockout with genome-wide analysis, defining epistatic order of PRC1/PRC2 recruitment","pmids":["28596365"],"is_preprint":false},{"year":2016,"finding":"The Sfmbt subunit of PhoRC and the Scm subunit of canonical PRC1 directly bind each other through their SAM domains; the 1.9 Å crystal structure reveals the recognition mechanism and shows Sfmbt-SAM lacks polymerization capacity. PRE-tethered Sfmbt-SAM nucleates PRC1 recruitment via Scm-SAM, and Scm-SAM/Ph-SAM polymerization drives PRC1-compacted chromatin formation.","method":"X-ray crystallography (1.9 Å), in vitro binding assays, Drosophila functional genetics","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1 — high-resolution structure plus in vitro and in vivo functional validation","pmids":["27151979"],"is_preprint":false},{"year":2016,"finding":"BMI1's central domain adopts a ubiquitin-like (UBL) fold that binds PHC2 in a β-hairpin conformation and also mediates BMI1 homo-oligomerization; both BMI1-PHC2 interaction and UBL-domain homo-oligomerization are required for H2A ubiquitination activity of PRC1 and clonogenic potential of cancer cells.","method":"NMR spectroscopy, X-ray crystallography, H2A ubiquitination assay, clonogenic assay","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 — combined NMR and crystal structure with functional enzymatic and cellular validation","pmids":["27827373"],"is_preprint":false},{"year":2020,"finding":"SUMOylated CBX2-containing PRC1 recruits the H3.3-specific chaperone DAXX to paternal pericentric heterochromatin (pat-PCH) in mouse pre-implantation embryos, enabling H3.3 incorporation; loss of Daxx, Ring1, or Rnf2 abrogates H3.3 incorporation and causes chromatin breakage and mis-segregation of paternal chromosomes.","method":"Genetic knockdown/knockout in mouse embryos, immunofluorescence, complementation assays","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 — genetic perturbation with rescue and mechanistic pathway definition in an in vivo developmental model","pmids":["32395866"],"is_preprint":false},{"year":2015,"finding":"Cbx2 directs catalytically active PRC1 to paternal pericentric heterochromatin (pat-PCH) in mouse zygotes via its chromodomain binding H3K27me3 and an AT-hook binding AT-rich major satellites; HP1β at maternal PCH prevents Cbx2 AT-hook from accessing DNA there, establishing a parent-of-origin-specific PRC1 targeting mechanism.","method":"Mouse zygote genetics, domain mutation analysis, immunofluorescence, loss-of-function studies","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 — domain-level mutagenesis with in vivo parent-of-origin targeting mechanism defined","pmids":["25801166"],"is_preprint":false},{"year":2021,"finding":"Single-particle tracking in live mouse ESCs shows PRC1 (Polycomb complex) is highly dynamic with only a small fraction stably bound to chromatin, and exhibits low occupancy at target sites; specific subunits define kinetics (CBX for chromatin binding, other subunits for complex stability), suggesting chromatin modification rather than complex occupancy is central to gene repression.","method":"Single-particle tracking in live cells (SPT), genome engineering, chromatin fraction analysis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — quantitative live-cell SPT with genetic perturbations and integrated measurements","pmids":["33563969"],"is_preprint":false},{"year":2023,"finding":"PRC2.1 catalyzes most H3K27me3 at Polycomb targets and promotes recruitment of CBX2/4-cPRC1 but not CBX7-cPRC1; conversely, the PRC2.2 accessory protein JARID2 is specifically required for CBX7-cPRC1 recruitment and consequent 3D chromatin interactions, defining distinct mechanisms by which PRC2.1 and PRC2.2 recruit different canonical PRC1 forms.","method":"CRISPR knockout and genetic replacement of subunit-specific factors, ChIP-seq, Hi-C, Co-IP","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 — systematic genetic KO/replacement with genome-wide assays and interaction studies","pmids":["37030288"],"is_preprint":false},{"year":2020,"finding":"Canonical PRC1, but not variant PRC1, can maintain gene silencing through cell division upon removal of tethering signal, via cis-acting H2AK119ub1 and H3K27me3 promoting a sequence-independent feedback recruitment of PcG proteins.","method":"Reversible tethering of PcG proteins to ectopic sites in mouse ESCs, ChIP-seq, RNA-seq","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — reversible tethering system with genome-wide analysis distinguishing canonical vs. variant PRC1 functions","pmids":["31036804"],"is_preprint":false},{"year":2019,"finding":"Variant PRC1 complexes (not canonical PRC1) are the primary drivers of Polycomb-mediated gene repression; distinct pools of H2A monoubiquitylation from different variant PRC1 complexes are associated with target gene repression and X chromosome inactivation silencing. Canonical PRC1 contributes to higher-order chromatin structures but little to gene repression.","method":"Combinatorial genetic perturbation, quantitative genomics (ChIP-seq, RNA-seq) in mouse ESCs","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 — systematic combinatorial genetics with quantitative genome-wide readouts","pmids":["31029541"],"is_preprint":false},{"year":2020,"finding":"Canonical PRC1 mediates long-range chromatin interactions (bridging megabase-scale loci) independently of CTCF; impairment of PRC1 enzymatic activity does not directly disrupt these interactions, and transcriptional activation is separable from loss of PRC1-mediated interactions.","method":"Hi-C, imaging, genetic loss of function in mouse ESCs","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 — combination of Hi-C and imaging with enzymatic activity separation","pmids":["32439634"],"is_preprint":false}],"current_model":"PRC1 refers to two distinct proteins: (1) the mitotic 'Protein Regulator of Cytokinesis 1,' a CDK substrate and microtubule-binding/bundling protein that crosslinks antiparallel microtubules at the spindle midzone via its central domain, is activated by Plk1 and phosphorylated/inhibited by CDK1 to control bundling timing, acts as a mechanical dashpot to resist motor-driven microtubule sliding, recruits kinesin-4 (Kif4A) to mark microtubule plus-ends in a length-dependent manner, and is required for midzone and midbody assembly to complete cytokinesis; and (2) the epigenetic 'Polycomb Repressive Complex 1,' a multisubunit E3 ubiquitin ligase (Ring1A/B with PCGF, CBX, PHC, and RYBP/YAF2 subunits) that monoubiquitylates histone H2AK119, stimulated by RYBP, uses nucleosome contacts remote from the catalytic site for substrate specificity, represses transcription by blocking RNA Pol II binding and transcription initiation (reducing burst frequency) and by evicting Mediator from preinitiation complexes, propagates H2AK119ub1 through a positive-feedback mechanism, communicates with PRC2 to promote H3K27me3 deposition, mediates long-range 3D chromatin compaction and phase separation via PHC polymerization, and is recruited to chromatin through CBX-H3K27me3 reading, hnRNPK-Xist RNA interaction, PhoRC-SAM domain contacts, and CpG-island-targeting non-canonical complexes."},"narrative":{"teleology":[{"year":1997,"claim":"Whether PRC1-family proteins are cell-cycle-regulated was unknown; demonstration that yeast Ase1 undergoes APC/cyclosome-mediated proteolysis at mitotic exit, and that a non-degradable mutant delays spindle disassembly, established that PRC1-family turnover is essential for orderly spindle dynamics.","evidence":"Non-degradable Ase1 mutant expression and cell-cycle degradation assays in budding yeast","pmids":["9036857"],"confidence":"High","gaps":["Mechanism of APC recognition of Ase1/PRC1 degron not defined","Not tested in mammalian cells"]},{"year":1998,"claim":"The function of PRC1 in mammalian cell division was unknown; showing it is a CDK substrate that dynamically localizes to spindles and midbody, and that antibody microinjection blocks cytokinesis but not nuclear division, established PRC1 as a direct effector of cytokinesis.","evidence":"In vitro kinase assay, in vivo phosphorylation, antibody microinjection, immunolocalization in mammalian cells","pmids":["9885575"],"confidence":"High","gaps":["Molecular mechanism of cytokinesis failure not resolved","Phosphorylation sites and their individual functions not mapped"]},{"year":2002,"claim":"How PRC1 contributes to midzone formation was unclear; demonstrating that PRC1 directly binds and bundles microtubules in vitro, that CDK phosphorylation suppresses bundling during prometaphase, and that siRNA depletion abolishes midzone interdigitation defined PRC1 as a phospho-regulated microtubule crosslinker.","evidence":"In vitro microtubule bundling, phosphorylation-null mutant expression, siRNA knockdown, domain truncation analysis","pmids":["12082078"],"confidence":"High","gaps":["Structural basis of bundling not yet resolved","Identity of the phosphatase that reactivates PRC1 unknown"]},{"year":2005,"claim":"Whether PRC1-family function in midzone assembly is conserved and what downstream effectors it recruits was unknown; showing that fission yeast Ase1 is dose-dependent for bundling, required for anaphase B spindle integrity, and necessary for Aurora kinase midzone recruitment established PRC1 as a conserved scaffold for midzone signaling.","evidence":"Gene deletion, time-lapse imaging, overexpression, and genetic epistasis in fission yeast","pmids":["15647375"],"confidence":"High","gaps":["Direct physical interaction with Aurora kinase not demonstrated","Checkpoint function mechanism not fully defined"]},{"year":2013,"claim":"How antiparallel overlap length is set was a major open question; crystal structure of the PRC1 homodimer and reconstitution of PRC1–Kif4A end-tagging showed that the two proteins cooperate to mark microtubule plus-ends in a length-dependent manner, providing a molecular ruler mechanism.","evidence":"X-ray crystallography, in vitro reconstitution with TIRF microscopy, structure-guided mutagenesis, live-cell imaging","pmids":["23870126"],"confidence":"High","gaps":["How other MAPs modulate end-tagging in vivo not addressed","Mechanism of length-sensing at quantitative level incomplete"]},{"year":2018,"claim":"How PRC1 geometry-dependent sliding and stalling occur was unresolved; reconstitution showed that PRC1–Kif4A sliding velocity scales with initial overlap length and stalls when opposing end-tags collide, providing a self-limiting overlap control mechanism.","evidence":"In vitro reconstitution with TIRF microscopy and quantitative analysis","pmids":["30353849"],"confidence":"High","gaps":["Force generation at stall not measured","Contribution of other crosslinkers in vivo not tested"]},{"year":2018,"claim":"Which kinase phosphorylates PRC1 at Thr481 and what this modification does was unknown; identification of CDK16–Cyclin Y as the kinase and showing that its inhibition causes PRC1 mislocalization to the nucleus during interphase defined an interphase regulatory axis for PRC1.","evidence":"Analog-sensitive CDK16 (CRISPR), proteomic substrate identification, epistasis analysis","pmids":["30992425"],"confidence":"High","gaps":["Whether CDK16 regulates PRC1 bundling activity directly not tested","Redundancy with other CDKs at this site not fully explored"]},{"year":2020,"claim":"Whether PRC1 generates passive mechanical forces was unknown; optical trapping demonstrated that PRC1 crosslinks act as velocity-dependent friction generators (dashpots) whose force scales with sliding speed and crosslink number, establishing a biophysical function beyond static bundling.","evidence":"Simultaneous optical trapping and TIRF microscopy in vitro","pmids":["32640202"],"confidence":"High","gaps":["In vivo force measurements not performed","How dashpot friction integrates with active motor forces in cells not modeled"]},{"year":2016,"claim":"Whether PRC1 bridging fibers associate with kinetochores during metaphase was unclear; live imaging showed >90% of PRC1-labeled overlap bundles bridge sister k-fibers one-to-one, and PRC1 knockdown reduces bridging fiber thickness and interkinetochore distance, defining PRC1's role in metaphase force balance.","evidence":"PRC1-GFP live imaging, siRNA knockdown, quantitative analysis in human cells","pmids":["28028032"],"confidence":"High","gaps":["How bridging fiber forces are transmitted to kinetochores mechanistically unknown","Contribution relative to other crosslinkers not quantified"]},{"year":null,"claim":"Key open questions include the identity of the phosphatase that reactivates PRC1 bundling at anaphase onset, how PRC1 dashpot forces integrate with motor-generated forces in vivo, and whether PRC1 post-translational modifications beyond CDK and Plk1 sites regulate its crosslinking geometry in different cell types.","evidence":"","pmids":[],"confidence":"Medium","gaps":["Phosphatase identity unknown","In vivo force balance model incorporating PRC1 friction not established","Cell-type-specific regulation largely unexplored"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[1,2,5,6,7,11]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[1,2,5,13]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,1,2,6]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,3]},{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[0,1,9]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0,1,3,4,6,8,12]}],"complexes":["PRC1 homodimer"],"partners":["KIF4A","CDK16","CCNY","PLK1","BIM1"],"other_free_text":[]},"mechanistic_narrative":"PRC1 is a homodimeric microtubule-bundling protein that crosslinks antiparallel microtubules at the spindle midzone to ensure proper spindle mechanics and cytokinesis. Its bundling activity is suppressed during early mitosis by CDK phosphorylation and activated at anaphase, with CDK16–Cyclin Y phosphorylating Thr481 to regulate interphase localization, while Plk1 activates PRC1 to promote cytokinesis [PMID:9885575, PMID:12082078, PMID:30992425, PMID:34531368]. PRC1 cooperates with kinesin-4 (Kif4A) to mark microtubule plus-ends in a length-dependent manner, forming end-tags whose collision stalls sliding, and functions as a velocity-dependent mechanical dashpot that generates frictional resistance to motor-driven microtubule sliding [PMID:23870126, PMID:30353849, PMID:32640202]. Crystal structures reveal a spectrin-like fold that mediates homodimerization and antiparallel microtubule crosslinking, with distinct domains required for microtubule binding, cleavage-furrow localization, and Kif4A co-recruitment [PMID:23870126, PMID:12082078]."},"prefetch_data":{"uniprot":{"accession":"O43663","full_name":"Protein regulator of cytokinesis 1","aliases":[],"length_aa":620,"mass_kda":71.6,"function":"Key regulator of cytokinesis that cross-links antiparrallel microtubules at an average distance of 35 nM. Essential for controlling the spatiotemporal formation of the midzone and successful cytokinesis. Required for KIF14 localization to the central spindle and midbody. Required to recruit PLK1 to the spindle. Stimulates PLK1 phosphorylation of RACGAP1 to allow recruitment of ECT2 to the central spindle. Acts as an oncogene for promoting bladder cancer cells proliferation, apoptosis inhibition and carcinogenic progression (PubMed:17409436)","subcellular_location":"Nucleus; Cytoplasm; Cytoplasm, cytoskeleton, spindle pole; Midbody; Chromosome","url":"https://www.uniprot.org/uniprotkb/O43663/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/PRC1","classification":"Common Essential","n_dependent_lines":1196,"n_total_lines":1208,"dependency_fraction":0.9900662251655629},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CTTN","stoichiometry":0.2},{"gene":"TUBB4B","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/PRC1","total_profiled":1310},"omim":[{"mim_id":"620493","title":"STERILE ALPHA MOTIF DOMAIN-CONTAINING PROTEIN 7; SAMD7","url":"https://www.omim.org/entry/620493"},{"mim_id":"619906","title":"DExD-BOX HELICASE 39A; DDX39A","url":"https://www.omim.org/entry/619906"},{"mim_id":"619288","title":"COILED-COIL DOMAIN-CONTAINING PROTEIN 69; CCDC69","url":"https://www.omim.org/entry/619288"},{"mim_id":"617914","title":"MICROCEPHALY 20, PRIMARY, AUTOSOMAL RECESSIVE; MCPH20","url":"https://www.omim.org/entry/617914"},{"mim_id":"617795","title":"ELONGIN BC- AND POLYCOMB REPRESSIVE COMPLEX 2-ASSOCIATED PROTEIN; EPOP","url":"https://www.omim.org/entry/617795"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Microtubules","reliability":"Supported"},{"location":"Cytokinetic bridge","reliability":"Supported"},{"location":"Midbody","reliability":"Supported"},{"location":"Nucleoplasm","reliability":"Additional"},{"location":"Plasma membrane","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"bone marrow","ntpm":84.5},{"tissue":"testis","ntpm":50.4}],"url":"https://www.proteinatlas.org/search/PRC1"},"hgnc":{"alias_symbol":["ASE1","MAP65"],"prev_symbol":[]},"alphafold":{"accession":"O43663","domains":[{"cath_id":"-","chopping":"33-149","consensus_level":"medium","plddt":91.5509,"start":33,"end":149},{"cath_id":"1.20.58.1520","chopping":"285-377_385-462","consensus_level":"medium","plddt":90.7399,"start":285,"end":462},{"cath_id":"1.20.1270","chopping":"163-268","consensus_level":"medium","plddt":94.6915,"start":163,"end":268}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O43663","model_url":"https://alphafold.ebi.ac.uk/files/AF-O43663-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O43663-F1-predicted_aligned_error_v6.png","plddt_mean":78.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PRC1","jax_strain_url":"https://www.jax.org/strain/search?query=PRC1"},"sequence":{"accession":"O43663","fasta_url":"https://rest.uniprot.org/uniprotkb/O43663.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O43663/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O43663"}},"corpus_meta":[{"pmid":"12082078","id":"PMC_12082078","title":"PRC1 is a microtubule binding and bundling protein essential to maintain the mitotic spindle midzone.","date":"2002","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/12082078","citation_count":367,"is_preprint":false},{"pmid":"9885575","id":"PMC_9885575","title":"PRC1: a human mitotic spindle-associated CDK substrate protein required for cytokinesis.","date":"1998","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/9885575","citation_count":310,"is_preprint":false},{"pmid":"16628213","id":"PMC_16628213","title":"Genome-wide profiling of PRC1 and PRC2 Polycomb chromatin binding in Drosophila melanogaster.","date":"2006","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/16628213","citation_count":309,"is_preprint":false},{"pmid":"25355358","id":"PMC_25355358","title":"Crystal structure of the PRC1 ubiquitylation module bound to the nucleosome.","date":"2014","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/25355358","citation_count":265,"is_preprint":false},{"pmid":"29220657","id":"PMC_29220657","title":"hnRNPK Recruits PCGF3/5-PRC1 to the Xist RNA B-Repeat to Establish Polycomb-Mediated Chromosomal Silencing.","date":"2017","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/29220657","citation_count":257,"is_preprint":false},{"pmid":"9036857","id":"PMC_9036857","title":"APC-mediated proteolysis of Ase1 and the morphogenesis of the mitotic spindle.","date":"1997","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/9036857","citation_count":226,"is_preprint":false},{"pmid":"28596365","id":"PMC_28596365","title":"PCGF3/5-PRC1 initiates Polycomb recruitment in X chromosome inactivation.","date":"2017","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/28596365","citation_count":212,"is_preprint":false},{"pmid":"31029541","id":"PMC_31029541","title":"Synergy between Variant PRC1 Complexes Defines Polycomb-Mediated Gene Repression.","date":"2019","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/31029541","citation_count":206,"is_preprint":false},{"pmid":"23150630","id":"PMC_23150630","title":"Phosphatidic acid regulates microtubule organization by interacting with MAP65-1 in response to salt stress in Arabidopsis.","date":"2012","source":"The Plant cell","url":"https://pubmed.ncbi.nlm.nih.gov/23150630","citation_count":174,"is_preprint":false},{"pmid":"26178786","id":"PMC_26178786","title":"Transcriptional repression by PRC1 in the absence of H2A monoubiquitylation.","date":"2015","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/26178786","citation_count":155,"is_preprint":false},{"pmid":"15557096","id":"PMC_15557096","title":"In vivo dynamics and differential microtubule-binding activities of MAP65 proteins.","date":"2004","source":"Plant physiology","url":"https://pubmed.ncbi.nlm.nih.gov/15557096","citation_count":141,"is_preprint":false},{"pmid":"15647375","id":"PMC_15647375","title":"The roles of fission yeast ase1 in mitotic cell division, meiotic nuclear oscillation, and cytokinesis checkpoint signaling.","date":"2005","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/15647375","citation_count":129,"is_preprint":false},{"pmid":"23870126","id":"PMC_23870126","title":"Marking and measuring single microtubules by PRC1 and kinesin-4.","date":"2013","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/23870126","citation_count":127,"is_preprint":false},{"pmid":"30664650","id":"PMC_30664650","title":"BAP1 complex promotes transcription by opposing PRC1-mediated H2A ubiquitylation.","date":"2019","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/30664650","citation_count":122,"is_preprint":false},{"pmid":"27705745","id":"PMC_27705745","title":"RYBP stimulates PRC1 to shape chromatin-based communication between Polycomb repressive complexes.","date":"2016","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/27705745","citation_count":116,"is_preprint":false},{"pmid":"22770845","id":"PMC_22770845","title":"The polycomb group protein L3mbtl2 assembles an atypical PRC1-family complex that is essential in pluripotent stem cells and early development.","date":"2012","source":"Cell stem cell","url":"https://pubmed.ncbi.nlm.nih.gov/22770845","citation_count":115,"is_preprint":false},{"pmid":"32439634","id":"PMC_32439634","title":"A central role for canonical PRC1 in shaping the 3D nuclear landscape.","date":"2020","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/32439634","citation_count":108,"is_preprint":false},{"pmid":"29502955","id":"PMC_29502955","title":"The SS18-SSX Oncoprotein Hijacks KDM2B-PRC1.1 to Drive Synovial Sarcoma.","date":"2018","source":"Cancer cell","url":"https://pubmed.ncbi.nlm.nih.gov/29502955","citation_count":105,"is_preprint":false},{"pmid":"18263774","id":"PMC_18263774","title":"MAP65-3 microtubule-associated protein is essential for nematode-induced giant cell ontogenesis in Arabidopsis.","date":"2008","source":"The Plant cell","url":"https://pubmed.ncbi.nlm.nih.gov/18263774","citation_count":100,"is_preprint":false},{"pmid":"21873565","id":"PMC_21873565","title":"Interaction of antiparallel microtubules in the phragmoplast is mediated by the microtubule-associated protein MAP65-3 in Arabidopsis.","date":"2011","source":"The Plant cell","url":"https://pubmed.ncbi.nlm.nih.gov/21873565","citation_count":95,"is_preprint":false},{"pmid":"32203418","id":"PMC_32203418","title":"RYBP/YAF2-PRC1 complexes and histone H1-dependent chromatin compaction mediate propagation of H2AK119ub1 during cell division.","date":"2020","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/32203418","citation_count":91,"is_preprint":false},{"pmid":"21551389","id":"PMC_21551389","title":"Microtubule-associated proteins MAP65-1 and MAP65-2 positively regulate axial cell growth in etiolated Arabidopsis hypocotyls.","date":"2011","source":"The Plant cell","url":"https://pubmed.ncbi.nlm.nih.gov/21551389","citation_count":86,"is_preprint":false},{"pmid":"29337181","id":"PMC_29337181","title":"A Non-canonical BCOR-PRC1.1 Complex Represses Differentiation Programs in Human ESCs.","date":"2018","source":"Cell stem cell","url":"https://pubmed.ncbi.nlm.nih.gov/29337181","citation_count":82,"is_preprint":false},{"pmid":"27557709","id":"PMC_27557709","title":"Interdependence of PRC1 and PRC2 for recruitment to Polycomb Response Elements.","date":"2016","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/27557709","citation_count":81,"is_preprint":false},{"pmid":"19060108","id":"PMC_19060108","title":"The C-terminal variable region specifies the dynamic properties of Arabidopsis microtubule-associated protein MAP65 isotypes.","date":"2008","source":"The Plant cell","url":"https://pubmed.ncbi.nlm.nih.gov/19060108","citation_count":80,"is_preprint":false},{"pmid":"34608337","id":"PMC_34608337","title":"PRC1 drives Polycomb-mediated gene repression by controlling transcription initiation and burst frequency.","date":"2021","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/34608337","citation_count":78,"is_preprint":false},{"pmid":"27151979","id":"PMC_27151979","title":"Molecular basis of PRC1 targeting to Polycomb response elements by PhoRC.","date":"2016","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/27151979","citation_count":75,"is_preprint":false},{"pmid":"25801166","id":"PMC_25801166","title":"Cbx2 targets PRC1 to constitutive heterochromatin in mouse zygotes in a parent-of-origin-dependent manner.","date":"2015","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/25801166","citation_count":74,"is_preprint":false},{"pmid":"28087428","id":"PMC_28087428","title":"Polycomb complexes PRC1 and their function in hematopoiesis.","date":"2017","source":"Experimental hematology","url":"https://pubmed.ncbi.nlm.nih.gov/28087428","citation_count":72,"is_preprint":false},{"pmid":"28513584","id":"PMC_28513584","title":"Kinesin-5-independent mitotic spindle assembly requires the antiparallel microtubule crosslinker Ase1 in fission yeast.","date":"2017","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/28513584","citation_count":63,"is_preprint":false},{"pmid":"33202645","id":"PMC_33202645","title":"Mammalian PRC1 Complexes: Compositional Complexity and Diverse Molecular Mechanisms.","date":"2020","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/33202645","citation_count":61,"is_preprint":false},{"pmid":"28028032","id":"PMC_28028032","title":"PRC1-labeled microtubule bundles and kinetochore pairs show one-to-one association in metaphase.","date":"2016","source":"EMBO reports","url":"https://pubmed.ncbi.nlm.nih.gov/28028032","citation_count":61,"is_preprint":false},{"pmid":"24553292","id":"PMC_24553292","title":"The putative PRC1 RING-finger protein AtRING1A regulates flowering through repressing MADS AFFECTING FLOWERING genes in Arabidopsis.","date":"2014","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/24553292","citation_count":60,"is_preprint":false},{"pmid":"23706298","id":"PMC_23706298","title":"The polycomb complex PRC1: composition and function in plants.","date":"2013","source":"Journal of genetics and genomics = Yi chuan xue bao","url":"https://pubmed.ncbi.nlm.nih.gov/23706298","citation_count":59,"is_preprint":false},{"pmid":"31036804","id":"PMC_31036804","title":"Canonical PRC1 controls sequence-independent propagation of Polycomb-mediated gene silencing.","date":"2019","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/31036804","citation_count":59,"is_preprint":false},{"pmid":"22910904","id":"PMC_22910904","title":"Polycomb repressive complex 1 (PRC1) disassembles RNA polymerase II preinitiation complexes.","date":"2012","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22910904","citation_count":58,"is_preprint":false},{"pmid":"29413422","id":"PMC_29413422","title":"PRC1: Linking Cytokinesis, Chromosomal Instability, and Cancer Evolution.","date":"2017","source":"Trends in cancer","url":"https://pubmed.ncbi.nlm.nih.gov/29413422","citation_count":56,"is_preprint":false},{"pmid":"27827373","id":"PMC_27827373","title":"BMI1 regulates PRC1 architecture and activity through homo- and hetero-oligomerization.","date":"2016","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/27827373","citation_count":56,"is_preprint":false},{"pmid":"33563969","id":"PMC_33563969","title":"Live-cell single particle tracking of PRC1 reveals a highly dynamic system with low target site occupancy.","date":"2021","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/33563969","citation_count":56,"is_preprint":false},{"pmid":"37030288","id":"PMC_37030288","title":"PRC2.1- and PRC2.2-specific accessory proteins drive recruitment of different forms of canonical PRC1.","date":"2023","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/37030288","citation_count":54,"is_preprint":false},{"pmid":"22770239","id":"PMC_22770239","title":"Polycomb in stem cells: PRC1 branches out.","date":"2012","source":"Cell stem cell","url":"https://pubmed.ncbi.nlm.nih.gov/22770239","citation_count":54,"is_preprint":false},{"pmid":"22570443","id":"PMC_22570443","title":"Arabidopsis microtubule-associated protein MAP65-3 cross-links antiparallel microtubules toward their plus ends in the phragmoplast via its distinct C-terminal microtubule binding domain.","date":"2012","source":"The Plant cell","url":"https://pubmed.ncbi.nlm.nih.gov/22570443","citation_count":53,"is_preprint":false},{"pmid":"32196702","id":"PMC_32196702","title":"Activity of PRC1 and Histone H2AK119 Monoubiquitination: Revising Popular Misconceptions.","date":"2020","source":"BioEssays : news and reviews in molecular, cellular and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/32196702","citation_count":50,"is_preprint":false},{"pmid":"23349393","id":"PMC_23349393","title":"Nonredundant and locus-specific gene repression functions of PRC1 paralog family members in human hematopoietic stem/progenitor cells.","date":"2013","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/23349393","citation_count":50,"is_preprint":false},{"pmid":"17011227","id":"PMC_17011227","title":"MAP65: a bridge linking a MAP kinase to microtubule turnover.","date":"2006","source":"Current opinion in plant biology","url":"https://pubmed.ncbi.nlm.nih.gov/17011227","citation_count":49,"is_preprint":false},{"pmid":"30353849","id":"PMC_30353849","title":"Geometry of antiparallel microtubule bundles regulates relative sliding and stalling by PRC1 and Kif4A.","date":"2018","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/30353849","citation_count":48,"is_preprint":false},{"pmid":"28370001","id":"PMC_28370001","title":"Arabidopsis MAP65-4 plays a role in phragmoplast microtubule organization and marks the cortical cell division site.","date":"2017","source":"The New phytologist","url":"https://pubmed.ncbi.nlm.nih.gov/28370001","citation_count":48,"is_preprint":false},{"pmid":"21119057","id":"PMC_21119057","title":"Arabidopsis kinetochore fiber-associated MAP65-4 cross-links microtubules and promotes microtubule bundle elongation.","date":"2010","source":"The Plant cell","url":"https://pubmed.ncbi.nlm.nih.gov/21119057","citation_count":48,"is_preprint":false},{"pmid":"30254245","id":"PMC_30254245","title":"Loss of PRC1 induces higher-order opening of Hox loci independently of transcription during Drosophila embryogenesis.","date":"2018","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/30254245","citation_count":46,"is_preprint":false},{"pmid":"16449317","id":"PMC_16449317","title":"The role of MAP65-1 in microtubule bundling during Zinnia tracheary element formation.","date":"2006","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/16449317","citation_count":45,"is_preprint":false},{"pmid":"27879390","id":"PMC_27879390","title":"Phosphorylation of MAP65-1 by Arabidopsis Aurora Kinases Is Required for Efficient Cell Cycle Progression.","date":"2016","source":"Plant physiology","url":"https://pubmed.ncbi.nlm.nih.gov/27879390","citation_count":44,"is_preprint":false},{"pmid":"34857746","id":"PMC_34857746","title":"Repression of germline genes by PRC1.6 and SETDB1 in the early embryo precedes DNA methylation-mediated silencing.","date":"2021","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/34857746","citation_count":44,"is_preprint":false},{"pmid":"28900001","id":"PMC_28900001","title":"Samd7 is a cell type-specific PRC1 component essential for establishing retinal rod photoreceptor identity.","date":"2017","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/28900001","citation_count":43,"is_preprint":false},{"pmid":"22443289","id":"PMC_22443289","title":"MAP65-1 and MAP65-2 promote cell proliferation and axial growth in Arabidopsis roots.","date":"2012","source":"The Plant journal : for cell and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/22443289","citation_count":42,"is_preprint":false},{"pmid":"23103209","id":"PMC_23103209","title":"End-binding proteins and Ase1/PRC1 define local functionality of structurally distinct parts of the microtubule cytoskeleton.","date":"2012","source":"Trends in cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/23103209","citation_count":40,"is_preprint":false},{"pmid":"31323466","id":"PMC_31323466","title":"Chromatin folding and nuclear architecture: PRC1 function in 3D.","date":"2019","source":"Current opinion in genetics & development","url":"https://pubmed.ncbi.nlm.nih.gov/31323466","citation_count":40,"is_preprint":false},{"pmid":"22500804","id":"PMC_22500804","title":"A PLETHORA-auxin transcription module controls cell division plane rotation through MAP65 and CLASP.","date":"2012","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/22500804","citation_count":39,"is_preprint":false},{"pmid":"30002118","id":"PMC_30002118","title":"Dual localized kinesin-12 POK2 plays multiple roles during cell division and interacts with MAP65-3.","date":"2018","source":"EMBO reports","url":"https://pubmed.ncbi.nlm.nih.gov/30002118","citation_count":37,"is_preprint":false},{"pmid":"32640202","id":"PMC_32640202","title":"The Mitotic Crosslinking Protein PRC1 Acts Like a Mechanical Dashpot to Resist Microtubule Sliding.","date":"2020","source":"Developmental cell","url":"https://pubmed.ncbi.nlm.nih.gov/32640202","citation_count":37,"is_preprint":false},{"pmid":"35449080","id":"PMC_35449080","title":"CDK16 promotes the progression and metastasis of triple-negative breast cancer by phosphorylating PRC1.","date":"2022","source":"Journal of experimental & clinical cancer research : CR","url":"https://pubmed.ncbi.nlm.nih.gov/35449080","citation_count":37,"is_preprint":false},{"pmid":"23956414","id":"PMC_23956414","title":"MAP65-1a positively regulates H2O2 amplification and enhances brassinosteroid-induced antioxidant defence in maize.","date":"2013","source":"Journal of experimental botany","url":"https://pubmed.ncbi.nlm.nih.gov/23956414","citation_count":36,"is_preprint":false},{"pmid":"35015684","id":"PMC_35015684","title":"BCOR and BCORL1 Mutations Drive Epigenetic Reprogramming and Oncogenic Signaling by Unlinking PRC1.1 from Target Genes.","date":"2022","source":"Blood cancer discovery","url":"https://pubmed.ncbi.nlm.nih.gov/35015684","citation_count":36,"is_preprint":false},{"pmid":"28190297","id":"PMC_28190297","title":"Elevated PRC1 in gastric carcinoma exerts oncogenic function and is targeted by piperlongumine in a p53-dependent manner.","date":"2017","source":"Journal of cellular and molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/28190297","citation_count":36,"is_preprint":false},{"pmid":"29097204","id":"PMC_29097204","title":"Chitosan-coated doxorubicin nano-particles drug delivery system inhibits cell growth of liver cancer via p53/PRC1 pathway.","date":"2017","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/29097204","citation_count":35,"is_preprint":false},{"pmid":"34637753","id":"PMC_34637753","title":"A Polycomb domain found in committed cells impairs differentiation when introduced into PRC1 in pluripotent cells.","date":"2021","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/34637753","citation_count":32,"is_preprint":false},{"pmid":"29166607","id":"PMC_29166607","title":"Kdm2b Regulates Somatic Reprogramming through Variant PRC1 Complex-Dependent Function.","date":"2017","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/29166607","citation_count":32,"is_preprint":false},{"pmid":"30560907","id":"PMC_30560907","title":"SCL/TAL1 cooperates with Polycomb RYBP-PRC1 to suppress alternative lineages in blood-fated cells.","date":"2018","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/30560907","citation_count":31,"is_preprint":false},{"pmid":"31343816","id":"PMC_31343816","title":"Mechanisms of the Ase1/PRC1/MAP65 family in central spindle assembly.","date":"2019","source":"Biological reviews of the Cambridge Philosophical Society","url":"https://pubmed.ncbi.nlm.nih.gov/31343816","citation_count":30,"is_preprint":false},{"pmid":"32395866","id":"PMC_32395866","title":"SUMOylated PRC1 controls histone H3.3 deposition and genome integrity of embryonic heterochromatin.","date":"2020","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/32395866","citation_count":29,"is_preprint":false},{"pmid":"34504070","id":"PMC_34504070","title":"Variant PCGF1-PRC1 links PRC2 recruitment with differentiation-associated transcriptional inactivation at target genes.","date":"2021","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/34504070","citation_count":29,"is_preprint":false},{"pmid":"28969791","id":"PMC_28969791","title":"MAP65-1 is required for the depolymerization and reorganization of cortical microtubules in the response to salt stress in Arabidopsis.","date":"2017","source":"Plant science : an international journal of experimental plant biology","url":"https://pubmed.ncbi.nlm.nih.gov/28969791","citation_count":28,"is_preprint":false},{"pmid":"32820036","id":"PMC_32820036","title":"Functional loss of a noncanonical BCOR-PRC1.1 complex accelerates SHH-driven medulloblastoma formation.","date":"2020","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/32820036","citation_count":27,"is_preprint":false},{"pmid":"27096886","id":"PMC_27096886","title":"Dual role of Med12 in PRC1-dependent gene repression and ncRNA-mediated transcriptional activation.","date":"2016","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/27096886","citation_count":27,"is_preprint":false},{"pmid":"28382142","id":"PMC_28382142","title":"Protein Regulator of Cytokinesis PRC1 Confers Chemoresistance and Predicts an Unfavorable Postoperative Survival of Hepatocellular Carcinoma Patients.","date":"2017","source":"Journal of Cancer","url":"https://pubmed.ncbi.nlm.nih.gov/28382142","citation_count":26,"is_preprint":false},{"pmid":"30992425","id":"PMC_30992425","title":"Phosphoregulation of the oncogenic protein regulator of cytokinesis 1 (PRC1) by the atypical CDK16/CCNY complex.","date":"2019","source":"Experimental & molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/30992425","citation_count":26,"is_preprint":false},{"pmid":"29070704","id":"PMC_29070704","title":"Bivalent complexes of PRC1 with orthologs of BRD4 and MOZ/MORF target developmental genes in Drosophila.","date":"2017","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/29070704","citation_count":26,"is_preprint":false},{"pmid":"38521066","id":"PMC_38521066","title":"Modularity of PRC1 composition and chromatin interaction define condensate properties.","date":"2024","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/38521066","citation_count":25,"is_preprint":false},{"pmid":"33750950","id":"PMC_33750950","title":"Independent domains for recruitment of PRC1 and PRC2 by human XIST.","date":"2021","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33750950","citation_count":25,"is_preprint":false},{"pmid":"31089172","id":"PMC_31089172","title":"Kinesin-6 Klp9 plays motor-dependent and -independent roles in collaboration with Kinesin-5 Cut7 and the microtubule crosslinker Ase1 in fission yeast.","date":"2019","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/31089172","citation_count":23,"is_preprint":false},{"pmid":"37735617","id":"PMC_37735617","title":"Aberrant gene activation in synovial sarcoma relies on SSX specificity and increased PRC1.1 stability.","date":"2023","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/37735617","citation_count":22,"is_preprint":false},{"pmid":"31017848","id":"PMC_31017848","title":"Microtubule bundling by MAP65-1 protects against severing by inhibiting the binding of katanin.","date":"2019","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/31017848","citation_count":22,"is_preprint":false},{"pmid":"34531368","id":"PMC_34531368","title":"Therapeutic targeting of the PLK1-PRC1-axis triggers cell death in genomically silent childhood cancer.","date":"2021","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/34531368","citation_count":22,"is_preprint":false},{"pmid":"23945219","id":"PMC_23945219","title":"Microtubule organization by kinesin motors and microtubule crosslinking protein MAP65.","date":"2013","source":"Journal of physics. Condensed matter : an Institute of Physics journal","url":"https://pubmed.ncbi.nlm.nih.gov/23945219","citation_count":21,"is_preprint":false},{"pmid":"34715055","id":"PMC_34715055","title":"Reprogramming CBX8-PRC1 function with a positive allosteric modulator.","date":"2021","source":"Cell chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/34715055","citation_count":21,"is_preprint":false},{"pmid":"31856871","id":"PMC_31856871","title":"MYCN and PRC1 cooperatively repress docosahexaenoic acid synthesis in neuroblastoma via ELOVL2.","date":"2019","source":"Journal of experimental & clinical cancer research : CR","url":"https://pubmed.ncbi.nlm.nih.gov/31856871","citation_count":21,"is_preprint":false},{"pmid":"37949928","id":"PMC_37949928","title":"Uncoupled evolution of the Polycomb system and deep origin of non-canonical PRC1.","date":"2023","source":"Communications biology","url":"https://pubmed.ncbi.nlm.nih.gov/37949928","citation_count":21,"is_preprint":false},{"pmid":"36737841","id":"PMC_36737841","title":"Targeted Degradation of PRC1 Components, BMI1 and RING1B, via a Novel Protein Complex Degrader Strategy.","date":"2023","source":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/36737841","citation_count":20,"is_preprint":false},{"pmid":"32868440","id":"PMC_32868440","title":"The genetic basis for PRC1 complex diversity emerged early in animal evolution.","date":"2020","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/32868440","citation_count":20,"is_preprint":false},{"pmid":"30065110","id":"PMC_30065110","title":"Chromatin modulation and gene regulation in plants: insight about PRC1 function.","date":"2018","source":"Biochemical Society transactions","url":"https://pubmed.ncbi.nlm.nih.gov/30065110","citation_count":19,"is_preprint":false},{"pmid":"26729480","id":"PMC_26729480","title":"The evolutionary landscape of PRC1 core components in green lineage.","date":"2016","source":"Planta","url":"https://pubmed.ncbi.nlm.nih.gov/26729480","citation_count":19,"is_preprint":false},{"pmid":"38142439","id":"PMC_38142439","title":"PRC1 directs PRC2-H3K27me3 deposition to shield adult spermatogonial stem cells from differentiation.","date":"2024","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/38142439","citation_count":19,"is_preprint":false},{"pmid":"32766276","id":"PMC_32766276","title":"ZFP36 Binds With PRC1 to Inhibit Tumor Growth and Increase 5-Fu Chemosensitivity of Hepatocellular Carcinoma.","date":"2020","source":"Frontiers in molecular biosciences","url":"https://pubmed.ncbi.nlm.nih.gov/32766276","citation_count":17,"is_preprint":false},{"pmid":"32997572","id":"PMC_32997572","title":"Ase1 domains dynamically slow anaphase spindle elongation and recruit Bim1 to the midzone.","date":"2020","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/32997572","citation_count":16,"is_preprint":false},{"pmid":"32628469","id":"PMC_32628469","title":"Structure and Role of BCOR PUFD in Noncanonical PRC1 Assembly and Disease.","date":"2020","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/32628469","citation_count":16,"is_preprint":false},{"pmid":"18562692","id":"PMC_18562692","title":"Latrunculin A delays anaphase onset in fission yeast by disrupting an Ase1-independent pathway controlling mitotic spindle stability.","date":"2008","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/18562692","citation_count":16,"is_preprint":false},{"pmid":"26798028","id":"PMC_26798028","title":"The Arabidopsis microtubule-associated protein MAP65-3 supports infection by filamentous biotrophic pathogens by down-regulating salicylic acid-dependent defenses.","date":"2016","source":"Journal of experimental botany","url":"https://pubmed.ncbi.nlm.nih.gov/26798028","citation_count":15,"is_preprint":false},{"pmid":"20878450","id":"PMC_20878450","title":"Tobacco microtubule-associated protein, MAP65-1c, bundles and stabilizes microtubules.","date":"2010","source":"Plant molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/20878450","citation_count":15,"is_preprint":false},{"pmid":"24768052","id":"PMC_24768052","title":"Replicative stress induces intragenic transcription of the ASE1 gene that negatively regulates Ase1 activity.","date":"2014","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/24768052","citation_count":14,"is_preprint":false},{"pmid":"29435157","id":"PMC_29435157","title":"The microtubule-associated protein PRC1 is a potential therapeutic target for lung cancer.","date":"2017","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/29435157","citation_count":14,"is_preprint":false},{"pmid":"33206458","id":"PMC_33206458","title":"PRC1 is a critical regulator for anaphase spindle midzone assembly and cytokinesis in mouse oocyte meiosis.","date":"2020","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/33206458","citation_count":14,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":43386,"output_tokens":7641,"usd":0.122386},"stage2":{"model":"claude-opus-4-6","input_tokens":11395,"output_tokens":2422,"usd":0.176288},"total_usd":0.298674,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1998,\n      \"finding\": \"PRC1 (protein regulator of cytokinesis 1) is a substrate for CDKs in vitro and is phosphorylated in vivo at CDK consensus sites; it localizes to the nucleus in interphase, associates dynamically with mitotic spindles during mitosis, and localizes to the midbody during cytokinesis. Microinjection of anti-PRC1 antibodies blocked cellular cleavage but not nuclear division, establishing a direct role in cytokinesis.\",\n      \"method\": \"In vitro kinase assay, in vivo phosphorylation, microinjection of inhibitory antibodies, immunolocalization\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (kinase assay, antibody microinjection, localization) in a single foundational study\",\n      \"pmids\": [\"9885575\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PRC1 binds and bundles microtubules both in vivo and in vitro; CDK phosphorylation suppresses its bundling activity during mitosis (a phosphorylation-null mutant causes aberrant prometaphase bundling); siRNA depletion abolishes microtubule interdigitation and the spindle midzone. The NH2-terminal region is required for localization to the cleavage furrow and midbody center, whereas the central region is required for microtubule binding and bundling.\",\n      \"method\": \"siRNA knockdown, overexpression of truncation/phosphorylation-null mutants, in vitro microtubule bundling assay, immunofluorescence\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — reconstituted bundling in vitro plus mutagenesis and siRNA with clear phenotypic readout, highly cited\",\n      \"pmids\": [\"12082078\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PRC1 and kinesin-4 (Kif4A) cooperate to tag microtubule plus ends in a length-dependent manner in vitro and in dividing cells. The crystal structure of the PRC1 homodimer was determined and protein-protein interactions required for microtubule plus-end tagging were mapped.\",\n      \"method\": \"In vitro reconstitution, crystal structure determination, live-cell imaging, structure-guided mutagenesis\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus reconstitution and in vivo validation with multiple orthogonal approaches\",\n      \"pmids\": [\"23870126\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CDK16 (in complex with Cyclin Y) phosphorylates PRC1 at Thr481; specific inhibition of CDK16 causes PRC1 dephosphorylation at this site and its delocalization to the nucleus during interphase. CDK16 inhibition and PRC1 downregulation show epistatic effects on cell viability, placing them in the same pathway.\",\n      \"method\": \"Analog-sensitive CDK16 generated by CRISPR-Cas9, proteomic substrate identification, phosphosite mapping, epistasis analysis\",\n      \"journal\": \"Experimental & molecular medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — analog-sensitive kinase approach with direct phosphosite identification and epistasis, moderate evidence\",\n      \"pmids\": [\"30992425\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CDK16 phosphorylates PRC1 to regulate spindle formation during mitosis in triple-negative breast cancer cells; CDK16 knockdown or pharmacological inhibition leads to mitotic spindle defects consistent with PRC1 dysfunction.\",\n      \"method\": \"Genetic knockdown, pharmacological inhibition, xenograft and organoid models, transcriptomic analysis\",\n      \"journal\": \"Journal of experimental & clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic follow-up confirming CDK16-PRC1 phosphorylation axis in a cancer model, single lab\",\n      \"pmids\": [\"35449080\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PRC1 acts as a mechanical dashpot (velocity-dependent friction generator) when crosslinking antiparallel microtubules: frictional forces scale with microtubule sliding velocity and number of PRC1 crosslinks, but not overlap length or PRC1 density within overlaps.\",\n      \"method\": \"Simultaneous optical trapping and TIRF microscopy in vitro\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro biophysical reconstitution with quantitative force measurements\",\n      \"pmids\": [\"32640202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"In metaphase spindles, PRC1-GFP-labeled overlap (bridging) bundles show one-to-one association with kinetochore pairs (>90% of overlap bundles bridge sister k-fibers); PRC1 knockdown reduces bridging fiber thickness and interkinetochore distance, demonstrating PRC1's role in spindle force balance.\",\n      \"method\": \"Live-cell imaging with PRC1-GFP, siRNA knockdown, endogenous PRC1 immunolocalization, quantitative analysis\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple imaging approaches with functional perturbation and quantitative readouts\",\n      \"pmids\": [\"28028032\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The geometry of antiparallel microtubule arrays regulates PRC1-Kif4A activity: sliding velocity scales with initial microtubule overlap length, and final overlap width scales with microtubule length. PRC1 and Kif4A accumulate at microtubule plus-ends forming 'end-tags,' and sliding stalls when opposing end-tags collide.\",\n      \"method\": \"In vitro reconstitution with fluorescently labeled proteins, TIRF microscopy\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with quantitative analysis of geometry-dependent regulation\",\n      \"pmids\": [\"30353849\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PLK1 activates PRC1 to promote cytokinesis; the EWSR1-FLI1 oncogenic transcription factor hijacks PRC1 via binding to a proximal GGAA-microsatellite enhancer, driving high PRC1 expression. PLK1 inhibition in PRC1-overexpressing Ewing sarcoma triggers mitotic catastrophe and tumor regression.\",\n      \"method\": \"CRISPR-mediated enhancer editing, in vitro and in vivo functional experiments, transcriptome profiling\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — CRISPR enhancer editing plus functional rescue, single study\",\n      \"pmids\": [\"34531368\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PRC1 is required for anaphase spindle midzone and midbody formation during mouse oocyte meiosis I; KIF4A co-localizes with PRC1 at the midzone, and KIF4A depletion disrupts PRC1 expression and localization, placing KIF4A upstream of PRC1 in midzone assembly during meiosis.\",\n      \"method\": \"siRNA knockdown, immunofluorescence localization, mRNA rescue injection, mouse oocyte model\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — knockdown with rescue and defined phenotypic readout, single lab\",\n      \"pmids\": [\"33206458\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"ZFP36 binds to AU-rich elements in the 3'UTR of PRC1 mRNA to downregulate PRC1 protein expression; this post-transcriptional regulation by ZFP36 suppresses PRC1-mediated promotion of cell proliferation in hepatocellular carcinoma.\",\n      \"method\": \"Luciferase reporter assay, ribonucleoprotein immunoprecipitation, overexpression and knockdown\",\n      \"journal\": \"Frontiers in molecular biosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — RIP and reporter assay demonstrating direct mRNA binding, single lab\",\n      \"pmids\": [\"32766276\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PRC1 crystal structure of the homodimer was determined (as part of the Subramanian et al. 2013 study), mapping the spectrin-like fold and identifying interaction surfaces required for antiparallel microtubule crosslinking and kinesin-4 co-recruitment.\",\n      \"method\": \"X-ray crystallography, in vitro reconstitution, structure-guided mutagenesis\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with functional validation via mutagenesis and reconstitution\",\n      \"pmids\": [\"23870126\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"The budding yeast ortholog Ase1 (PRC1 family) undergoes APC/cyclosome-mediated proteolysis when cells exit mitosis and enter G1; stable non-degradable Ase1 delays spindle disassembly and causes a spindle defect sensed by the spindle assembly checkpoint, establishing APC-mediated proteolysis as a regulator of spindle assembly and disassembly.\",\n      \"method\": \"Genetic analysis, cell-cycle-specific degradation assays, expression of non-degradable mutant\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — genetic epistasis with non-degradable mutant and checkpoint readout, highly cited\",\n      \"pmids\": [\"9036857\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Fission yeast Ase1 (PRC1 ortholog) localizes to microtubule overlapping zones and is a dose-dependent microtubule-bundling factor; its absence causes spindle collapse during anaphase B, and Aurora kinase fails to localize to central spindles without Ase1. Ase1 also acts as a regulatory component in the cytokinesis checkpoint.\",\n      \"method\": \"Gene deletion, time-lapse imaging, overexpression analysis, genetic epistasis\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal approaches in a model organism ortholog study\",\n      \"pmids\": [\"15647375\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In budding yeast, the Ase1 spectrin domain promotes midzone recruitment before anaphase onset and slows early spindle elongation via conserved basic residues; the carboxy-terminal domain interacts with and recruits EB1/Bim1 to the midzone to maintain midzone length during late anaphase.\",\n      \"method\": \"Domain truncation and mutagenesis, live-cell imaging, protein interaction assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — structure-function mutagenesis with live imaging and interaction assays, single lab\",\n      \"pmids\": [\"32997572\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In fission yeast, Ase1 (PRC1 ortholog) is required for bipolar spindle assembly in the absence of kinesin-5 by recruiting CLASP/Cls1 to stabilize microtubules; Brownian dynamics simulations confirm that Ase1 and Cls1 activity are sufficient for initial bipolar spindle formation via microtubule polymerization forces.\",\n      \"method\": \"Genetic epistasis, live-cell imaging, computational modeling\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with simulation support, single lab\",\n      \"pmids\": [\"28513584\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Replication stress in budding yeast induces intragenic transcription of ASE1, producing shorter protein isoforms that localize to the spindle and antagonize full-length Ase1 at the midzone, stabilizing the S-phase spindle by downregulating full-length Ase1 crosslinking activity.\",\n      \"method\": \"Biochemical characterization of short isoforms, overexpression, live-cell imaging, genetic analysis\",\n      \"journal\": \"Current biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic follow-up with multiple assays, single lab\",\n      \"pmids\": [\"24768052\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Canonical PRC1 (the Polycomb epigenetic complex) forms condensates synergistically with nucleosomal arrays (reducing critical concentration >20-fold); CBX subunit composition determines condensate initiation, and PHC2's polymerization activity promotes distinct adherent domain formation that does not coalesce. Live-cell imaging confirms CBX drives initiation and PHC drives stability.\",\n      \"method\": \"In vitro reconstitution with single-molecule imaging, live-cell imaging, genetic perturbation of specific subunits\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution plus single-molecule imaging plus live-cell validation with subunit-specific perturbations\",\n      \"pmids\": [\"38521066\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Crystal structure of the human Ring1B-Bmi1-UbcH5c PRC1 ubiquitylation module bound to the nucleosome core particle reveals that PRC1 achieves substrate specificity by contacting multiple nucleosome surfaces distinct from the catalytic site, and reveals an unexpected role for the E2 enzyme UbcH5c in substrate recognition for H2A Lys119 ubiquitylation.\",\n      \"method\": \"X-ray crystallography of PRC1-nucleosome complex\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution crystal structure of the catalytic complex with substrate, highly cited\",\n      \"pmids\": [\"25355358\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"RYBP/YAF2 stimulates the H2AK119 E3 ubiquitin ligase activity of PRC1; RYBP shapes H2AK119 mono-ubiquitylation at PcG targets and underpins activity-based communication between PRC1 and PRC2 required for normal H3K27me3. Loss of RYBP erodes repressive Polycomb chromatin domains.\",\n      \"method\": \"Mouse ESC genetic perturbation, quantitative genomics, ChIP-seq\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic perturbation with genome-wide quantitative analysis, multiple supporting findings\",\n      \"pmids\": [\"27705745\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Recombinant PRC1 (Polycomb complex) inhibits transcription on H3K27-methylated chromatin templates by blocking recruitment of Mediator and dissociating preassembled preinitiation complexes, while leaving TBP/TFIID relatively intact, defining a specific biochemical mechanism for PRC1-mediated transcriptional silencing.\",\n      \"method\": \"In vitro transcription reconstitution on immobilized chromatin templates, purified recombinant PRC1\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with purified components defining mechanistic step\",\n      \"pmids\": [\"22910904\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Rapid degron-based depletion of PRC1 (Polycomb complex) shows it functions independently of PRC2 to counteract RNA Pol II binding and transcription initiation; single-cell analysis reveals PRC1 controls transcriptional burst frequency uniformly across the cell population.\",\n      \"method\": \"Auxin-inducible degron (rapid depletion), time-resolved ChIP-seq and RNA-seq, single-cell gene expression analysis\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — rapid degron approach with kinetic genomics and single-cell analysis, multiple orthogonal readouts\",\n      \"pmids\": [\"34608337\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"RYBP and YAF2 each specifically bind H2AK119ub1 to recruit RYBP-PRC1 or YAF2-PRC1 and catalyze ubiquitination of neighboring nucleosomes via a positive-feedback model; histone H1-compacted chromatin enhances distal propagation of H2AK119ub1, contributing to epigenetic inheritance during cell division.\",\n      \"method\": \"Biochemical binding assays, reconstitution, genetic disruption, chromatin fractionation\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct binding assays plus reconstitution demonstrating positive feedback, multiple orthogonal approaches\",\n      \"pmids\": [\"32203418\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"hnRNPK is the principal RNA-binding protein that binds the Xist B-repeat-containing Polycomb Interaction Domain (XR-PID) and recruits PCGF3/5-PRC1 to initiate chromosome-wide H2AK119ub1 and subsequent PRC2 recruitment; synthetic tethering of hnRNPK to Xist lacking XR-PID is sufficient to restore Polycomb recruitment.\",\n      \"method\": \"RNA deletion mapping, RNA pulldown, synthetic tethering, genetic deletion, ChIP-seq\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods including synthetic rescue, defining molecular pathway\",\n      \"pmids\": [\"29220657\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PCGF3/5-PRC1 initiates Polycomb recruitment in X chromosome inactivation; it catalyzes H2AK119ub1 chromosome-wide, which signals recruitment of other PRC1 complexes and PRC2, the latter leading to H3K27me3 deposition. Pcgf3/5 knockout results in female-specific embryo lethality and abrogates Xist-mediated gene repression.\",\n      \"method\": \"Conditional knockout, ChIP-seq, immunofluorescence, RNA-seq\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockout with genome-wide analysis, defining epistatic order of PRC1/PRC2 recruitment\",\n      \"pmids\": [\"28596365\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The Sfmbt subunit of PhoRC and the Scm subunit of canonical PRC1 directly bind each other through their SAM domains; the 1.9 Å crystal structure reveals the recognition mechanism and shows Sfmbt-SAM lacks polymerization capacity. PRE-tethered Sfmbt-SAM nucleates PRC1 recruitment via Scm-SAM, and Scm-SAM/Ph-SAM polymerization drives PRC1-compacted chromatin formation.\",\n      \"method\": \"X-ray crystallography (1.9 Å), in vitro binding assays, Drosophila functional genetics\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution structure plus in vitro and in vivo functional validation\",\n      \"pmids\": [\"27151979\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"BMI1's central domain adopts a ubiquitin-like (UBL) fold that binds PHC2 in a β-hairpin conformation and also mediates BMI1 homo-oligomerization; both BMI1-PHC2 interaction and UBL-domain homo-oligomerization are required for H2A ubiquitination activity of PRC1 and clonogenic potential of cancer cells.\",\n      \"method\": \"NMR spectroscopy, X-ray crystallography, H2A ubiquitination assay, clonogenic assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — combined NMR and crystal structure with functional enzymatic and cellular validation\",\n      \"pmids\": [\"27827373\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"SUMOylated CBX2-containing PRC1 recruits the H3.3-specific chaperone DAXX to paternal pericentric heterochromatin (pat-PCH) in mouse pre-implantation embryos, enabling H3.3 incorporation; loss of Daxx, Ring1, or Rnf2 abrogates H3.3 incorporation and causes chromatin breakage and mis-segregation of paternal chromosomes.\",\n      \"method\": \"Genetic knockdown/knockout in mouse embryos, immunofluorescence, complementation assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic perturbation with rescue and mechanistic pathway definition in an in vivo developmental model\",\n      \"pmids\": [\"32395866\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Cbx2 directs catalytically active PRC1 to paternal pericentric heterochromatin (pat-PCH) in mouse zygotes via its chromodomain binding H3K27me3 and an AT-hook binding AT-rich major satellites; HP1β at maternal PCH prevents Cbx2 AT-hook from accessing DNA there, establishing a parent-of-origin-specific PRC1 targeting mechanism.\",\n      \"method\": \"Mouse zygote genetics, domain mutation analysis, immunofluorescence, loss-of-function studies\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — domain-level mutagenesis with in vivo parent-of-origin targeting mechanism defined\",\n      \"pmids\": [\"25801166\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Single-particle tracking in live mouse ESCs shows PRC1 (Polycomb complex) is highly dynamic with only a small fraction stably bound to chromatin, and exhibits low occupancy at target sites; specific subunits define kinetics (CBX for chromatin binding, other subunits for complex stability), suggesting chromatin modification rather than complex occupancy is central to gene repression.\",\n      \"method\": \"Single-particle tracking in live cells (SPT), genome engineering, chromatin fraction analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — quantitative live-cell SPT with genetic perturbations and integrated measurements\",\n      \"pmids\": [\"33563969\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PRC2.1 catalyzes most H3K27me3 at Polycomb targets and promotes recruitment of CBX2/4-cPRC1 but not CBX7-cPRC1; conversely, the PRC2.2 accessory protein JARID2 is specifically required for CBX7-cPRC1 recruitment and consequent 3D chromatin interactions, defining distinct mechanisms by which PRC2.1 and PRC2.2 recruit different canonical PRC1 forms.\",\n      \"method\": \"CRISPR knockout and genetic replacement of subunit-specific factors, ChIP-seq, Hi-C, Co-IP\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic genetic KO/replacement with genome-wide assays and interaction studies\",\n      \"pmids\": [\"37030288\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Canonical PRC1, but not variant PRC1, can maintain gene silencing through cell division upon removal of tethering signal, via cis-acting H2AK119ub1 and H3K27me3 promoting a sequence-independent feedback recruitment of PcG proteins.\",\n      \"method\": \"Reversible tethering of PcG proteins to ectopic sites in mouse ESCs, ChIP-seq, RNA-seq\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reversible tethering system with genome-wide analysis distinguishing canonical vs. variant PRC1 functions\",\n      \"pmids\": [\"31036804\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Variant PRC1 complexes (not canonical PRC1) are the primary drivers of Polycomb-mediated gene repression; distinct pools of H2A monoubiquitylation from different variant PRC1 complexes are associated with target gene repression and X chromosome inactivation silencing. Canonical PRC1 contributes to higher-order chromatin structures but little to gene repression.\",\n      \"method\": \"Combinatorial genetic perturbation, quantitative genomics (ChIP-seq, RNA-seq) in mouse ESCs\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic combinatorial genetics with quantitative genome-wide readouts\",\n      \"pmids\": [\"31029541\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Canonical PRC1 mediates long-range chromatin interactions (bridging megabase-scale loci) independently of CTCF; impairment of PRC1 enzymatic activity does not directly disrupt these interactions, and transcriptional activation is separable from loss of PRC1-mediated interactions.\",\n      \"method\": \"Hi-C, imaging, genetic loss of function in mouse ESCs\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — combination of Hi-C and imaging with enzymatic activity separation\",\n      \"pmids\": [\"32439634\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PRC1 refers to two distinct proteins: (1) the mitotic 'Protein Regulator of Cytokinesis 1,' a CDK substrate and microtubule-binding/bundling protein that crosslinks antiparallel microtubules at the spindle midzone via its central domain, is activated by Plk1 and phosphorylated/inhibited by CDK1 to control bundling timing, acts as a mechanical dashpot to resist motor-driven microtubule sliding, recruits kinesin-4 (Kif4A) to mark microtubule plus-ends in a length-dependent manner, and is required for midzone and midbody assembly to complete cytokinesis; and (2) the epigenetic 'Polycomb Repressive Complex 1,' a multisubunit E3 ubiquitin ligase (Ring1A/B with PCGF, CBX, PHC, and RYBP/YAF2 subunits) that monoubiquitylates histone H2AK119, stimulated by RYBP, uses nucleosome contacts remote from the catalytic site for substrate specificity, represses transcription by blocking RNA Pol II binding and transcription initiation (reducing burst frequency) and by evicting Mediator from preinitiation complexes, propagates H2AK119ub1 through a positive-feedback mechanism, communicates with PRC2 to promote H3K27me3 deposition, mediates long-range 3D chromatin compaction and phase separation via PHC polymerization, and is recruited to chromatin through CBX-H3K27me3 reading, hnRNPK-Xist RNA interaction, PhoRC-SAM domain contacts, and CpG-island-targeting non-canonical complexes.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PRC1 is a homodimeric microtubule-bundling protein that crosslinks antiparallel microtubules at the spindle midzone to ensure proper spindle mechanics and cytokinesis. Its bundling activity is suppressed during early mitosis by CDK phosphorylation and activated at anaphase, with CDK16–Cyclin Y phosphorylating Thr481 to regulate interphase localization, while Plk1 activates PRC1 to promote cytokinesis [PMID:9885575, PMID:12082078, PMID:30992425, PMID:34531368]. PRC1 cooperates with kinesin-4 (Kif4A) to mark microtubule plus-ends in a length-dependent manner, forming end-tags whose collision stalls sliding, and functions as a velocity-dependent mechanical dashpot that generates frictional resistance to motor-driven microtubule sliding [PMID:23870126, PMID:30353849, PMID:32640202]. Crystal structures reveal a spectrin-like fold that mediates homodimerization and antiparallel microtubule crosslinking, with distinct domains required for microtubule binding, cleavage-furrow localization, and Kif4A co-recruitment [PMID:23870126, PMID:12082078].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Whether PRC1-family proteins are cell-cycle-regulated was unknown; demonstration that yeast Ase1 undergoes APC/cyclosome-mediated proteolysis at mitotic exit, and that a non-degradable mutant delays spindle disassembly, established that PRC1-family turnover is essential for orderly spindle dynamics.\",\n      \"evidence\": \"Non-degradable Ase1 mutant expression and cell-cycle degradation assays in budding yeast\",\n      \"pmids\": [\"9036857\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of APC recognition of Ase1/PRC1 degron not defined\", \"Not tested in mammalian cells\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"The function of PRC1 in mammalian cell division was unknown; showing it is a CDK substrate that dynamically localizes to spindles and midbody, and that antibody microinjection blocks cytokinesis but not nuclear division, established PRC1 as a direct effector of cytokinesis.\",\n      \"evidence\": \"In vitro kinase assay, in vivo phosphorylation, antibody microinjection, immunolocalization in mammalian cells\",\n      \"pmids\": [\"9885575\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism of cytokinesis failure not resolved\", \"Phosphorylation sites and their individual functions not mapped\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"How PRC1 contributes to midzone formation was unclear; demonstrating that PRC1 directly binds and bundles microtubules in vitro, that CDK phosphorylation suppresses bundling during prometaphase, and that siRNA depletion abolishes midzone interdigitation defined PRC1 as a phospho-regulated microtubule crosslinker.\",\n      \"evidence\": \"In vitro microtubule bundling, phosphorylation-null mutant expression, siRNA knockdown, domain truncation analysis\",\n      \"pmids\": [\"12082078\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of bundling not yet resolved\", \"Identity of the phosphatase that reactivates PRC1 unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Whether PRC1-family function in midzone assembly is conserved and what downstream effectors it recruits was unknown; showing that fission yeast Ase1 is dose-dependent for bundling, required for anaphase B spindle integrity, and necessary for Aurora kinase midzone recruitment established PRC1 as a conserved scaffold for midzone signaling.\",\n      \"evidence\": \"Gene deletion, time-lapse imaging, overexpression, and genetic epistasis in fission yeast\",\n      \"pmids\": [\"15647375\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct physical interaction with Aurora kinase not demonstrated\", \"Checkpoint function mechanism not fully defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"How antiparallel overlap length is set was a major open question; crystal structure of the PRC1 homodimer and reconstitution of PRC1–Kif4A end-tagging showed that the two proteins cooperate to mark microtubule plus-ends in a length-dependent manner, providing a molecular ruler mechanism.\",\n      \"evidence\": \"X-ray crystallography, in vitro reconstitution with TIRF microscopy, structure-guided mutagenesis, live-cell imaging\",\n      \"pmids\": [\"23870126\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How other MAPs modulate end-tagging in vivo not addressed\", \"Mechanism of length-sensing at quantitative level incomplete\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"How PRC1 geometry-dependent sliding and stalling occur was unresolved; reconstitution showed that PRC1–Kif4A sliding velocity scales with initial overlap length and stalls when opposing end-tags collide, providing a self-limiting overlap control mechanism.\",\n      \"evidence\": \"In vitro reconstitution with TIRF microscopy and quantitative analysis\",\n      \"pmids\": [\"30353849\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Force generation at stall not measured\", \"Contribution of other crosslinkers in vivo not tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Which kinase phosphorylates PRC1 at Thr481 and what this modification does was unknown; identification of CDK16–Cyclin Y as the kinase and showing that its inhibition causes PRC1 mislocalization to the nucleus during interphase defined an interphase regulatory axis for PRC1.\",\n      \"evidence\": \"Analog-sensitive CDK16 (CRISPR), proteomic substrate identification, epistasis analysis\",\n      \"pmids\": [\"30992425\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CDK16 regulates PRC1 bundling activity directly not tested\", \"Redundancy with other CDKs at this site not fully explored\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Whether PRC1 generates passive mechanical forces was unknown; optical trapping demonstrated that PRC1 crosslinks act as velocity-dependent friction generators (dashpots) whose force scales with sliding speed and crosslink number, establishing a biophysical function beyond static bundling.\",\n      \"evidence\": \"Simultaneous optical trapping and TIRF microscopy in vitro\",\n      \"pmids\": [\"32640202\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo force measurements not performed\", \"How dashpot friction integrates with active motor forces in cells not modeled\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Whether PRC1 bridging fibers associate with kinetochores during metaphase was unclear; live imaging showed >90% of PRC1-labeled overlap bundles bridge sister k-fibers one-to-one, and PRC1 knockdown reduces bridging fiber thickness and interkinetochore distance, defining PRC1's role in metaphase force balance.\",\n      \"evidence\": \"PRC1-GFP live imaging, siRNA knockdown, quantitative analysis in human cells\",\n      \"pmids\": [\"28028032\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How bridging fiber forces are transmitted to kinetochores mechanistically unknown\", \"Contribution relative to other crosslinkers not quantified\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include the identity of the phosphatase that reactivates PRC1 bundling at anaphase onset, how PRC1 dashpot forces integrate with motor-generated forces in vivo, and whether PRC1 post-translational modifications beyond CDK and Plk1 sites regulate its crosslinking geometry in different cell types.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Phosphatase identity unknown\", \"In vivo force balance model incorporating PRC1 friction not established\", \"Cell-type-specific regulation largely unexplored\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [1, 2, 5, 6, 7, 11]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1, 2, 5, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 1, 2, 6]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [0, 1, 9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0, 1, 3, 4, 6, 8, 12]}\n    ],\n    \"complexes\": [\n      \"PRC1 homodimer\"\n    ],\n    \"partners\": [\n      \"KIF4A\",\n      \"CDK16\",\n      \"CCNY\",\n      \"PLK1\",\n      \"BIM1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}