{"gene":"BORA","run_date":"2026-06-09T22:02:45","timeline":{"discoveries":[{"year":2006,"finding":"Bora (Aurora Borealis) is a conserved binding partner of Aurora-A kinase required for its activation at mitotic entry. Both Drosophila and human Bora bind Aurora-A and activate the kinase in vitro. In interphase, Bora is nuclear; upon mitotic entry it translocates to the cytoplasm in a Cdc2-dependent manner, where it activates Aurora-A.","method":"In vitro kinase assay, genetic rescue (bora mutants rescued by Bora overexpression in Drosophila PNS), subcellular fractionation/live imaging, co-immunoprecipitation","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro kinase reconstitution with human and Drosophila proteins, genetic epistasis in vivo, localization by imaging, replicated across species","pmids":["16890155"],"is_preprint":false},{"year":2008,"finding":"Bora interacts with Plk1 and controls accessibility of the Plk1 activation loop (T210) for phosphorylation and activation by Aurora A, thereby driving the G2-M transition. Bora accumulates in G2 and promotes Aurora-A-mediated Plk1 activation leading to Cdk1 activation and mitotic entry.","method":"Co-immunoprecipitation, in vitro kinase assay, RNAi knockdown with mitotic entry readout, functional genomics/proteomics","journal":"Science (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro reconstitution of the Aurora A–Bora–Plk1 activation cascade, co-IP, and functional knockdown with defined phenotype; foundational paper replicated by multiple labs","pmids":["18566290"],"is_preprint":false},{"year":2008,"finding":"Bora is degraded by the SCF-β-TrCP ubiquitin ligase in mitosis. Plk1 phosphorylates a conserved DSGxxT degron in Bora, promoting its interaction with β-TrCP. Stabilization of Bora (degron mutant) prolongs metaphase and delays anaphase. Bora knockdown activates the spindle checkpoint and delays sister chromatid segregation; Bora promotes spindle stability, microtubule polymerization, and kinetochore tension.","method":"Co-immunoprecipitation, in vitro kinase assay, proteasome inhibitor treatment, site-directed mutagenesis of degron, RNAi knockdown with spindle/kinetochore phenotype readout","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — mutagenesis of degron + co-IP with β-TrCP + in vitro Plk1 phosphorylation + multiple cellular phenotypes","pmids":["18378770"],"is_preprint":false},{"year":2010,"finding":"In C. elegans, the Bora ortholog SPAT-1 acts with PLK-1 (not Aurora A/AIR-1) to regulate PAR polarity and cell cycle progression. SPAT-1 binds PLK-1; SPAT-1 and PLK-1 depletion cause similar cell division and polarity defects distinct from AIR-1 depletion. SPAT-1 is enriched in posterior cells in a PAR polarity- and PLK-1-dependent manner.","method":"RNAi depletion, genetic epistasis (par-2 mutant rescue), co-immunoprecipitation (SPAT-1/PLK-1 interaction), immunofluorescence localization","journal":"Development (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — reciprocal epistasis and co-IP in C. elegans, single lab, multiple readouts","pmids":["20823068"],"is_preprint":false},{"year":2013,"finding":"A fraction of Bora is retained in mitosis and is essential for continued Aurora-A-dependent T210 phosphorylation of Plk1. The Bora–Aurora-A complex remains the major activator of Plk1 in mitosis, functioning as a bistable switch.","method":"Quantitative phosphorylation assays, RNAi/siRNA depletion, immunoprecipitation, cell cycle synchronization with kinase activity readout","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical and cell-based methods, single lab","pmids":["24338364"],"is_preprint":false},{"year":2013,"finding":"ATR phosphorylates Bora at Thr-501 following UV irradiation; phospho-Thr-501 is recognized by SCF-β-TrCP, targeting Bora for degradation. Bora degradation inhibits Plk1 activation and contributes to DNA damage-induced G2 arrest.","method":"In vitro kinase assay (ATR on Bora), co-immunoprecipitation, site-directed mutagenesis (T501A), cell-based G2/M checkpoint assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro kinase assay plus mutagenesis and co-IP, single lab","pmids":["23592782"],"is_preprint":false},{"year":2013,"finding":"Pin1 interacts with Bora phosphorylated at Ser274 and Ser278, alters Bora's cytoplasmic translocation, and promotes its premature β-TrCP-mediated degradation, delaying mitotic entry. Aurora-A phosphorylates Pin1 at Ser16, suppressing Pin1's ability to bind Bora and act as a negative G2/M regulator.","method":"Co-immunoprecipitation, site-directed mutagenesis (Bora Ser274/278, Pin1 Ser16), subcellular localization assay, in vitro kinase assay, cell cycle progression readout","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — multiple co-IPs, mutagenesis, and cellular assays; single lab","pmids":["23970419"],"is_preprint":false},{"year":2015,"finding":"CDK-1 phosphorylates SPAT-1/Bora at multiple sites in its N-terminus to regulate its interaction with PLK-1 and trigger mitotic entry. Phospho-SPAT-1 activates PLK-1 by stimulating Aurora A-dependent T-loop phosphorylation in vitro. Phosphorylation of human Bora by Cdk1 likewise promotes Aurora A-dependent Plk1 T210 phosphorylation, indicating conservation.","method":"In vitro kinase assay, site-directed mutagenesis (CDK-1 phosphorylation sites), C. elegans genetics (non-phosphorylatable SPAT-1 mutants), co-immunoprecipitation (SPAT-1/PLK-1)","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro reconstitution of CDK-1→Bora→Aurora A→Plk1 cascade, mutagenesis, genetic validation in vivo, conservation confirmed in human cells","pmids":["25753036"],"is_preprint":false},{"year":2016,"finding":"Cdk1 phosphorylates the N-terminus of Bora at three conserved Sp/Tp residues; mutation of these sites or the two cyclin-binding motifs in Bora abrogates its ability to promote Aurora A-dependent Plk1 activation. Bora carrying these mutations cannot sustain mitotic entry after DNA damage in human cells.","method":"In vitro kinase assay, site-directed mutagenesis, FRET-based Plk1 activity biosensor in human cells, C. elegans genetics","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro reconstitution with mutagenesis, live-cell FRET biosensor, and in vivo genetic validation across two species","pmids":["27068477"],"is_preprint":false},{"year":2016,"finding":"DNA damage inhibits Plk1 by disrupting Aurora A recruitment to the Bora–Plk1 complex. Loss of Plk1-T210 phosphorylation is entirely responsible for DDR-induced Plk1 inhibition. A direct Aurora A–Bora fusion prevented DNA damage-induced loss of Plk1 activity, showing the DDR targets the Aurora A–Bora interaction.","method":"FRET-based Plk1 activity biosensor, Aurora A mutants refractory to DDR, Aurora A–Bora fusion protein expression, quantitative T210 phosphorylation analysis","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live-cell FRET biosensor plus fusion-protein rescue, single lab, multiple orthogonal approaches","pmids":["27721411"],"is_preprint":false},{"year":2014,"finding":"In Xenopus CSF extracts, phosphorylation of Bora on the Cdk consensus site T52 blocks Bora degradation by Plx1. Calcineurin dephosphorylates T52 upon fertilization, triggering Plx1 oscillations. In somatic cells, GFP-Bora degradation stops upon mitotic entry when Cdk1 activity is high, suggesting Cdk1 controls Bora through an incoherent feedforward loop.","method":"Xenopus egg extract biochemistry, phospho-mutant analysis, phosphatase (calcineurin) treatment, live-cell imaging of GFP-Bora","journal":"Cell cycle (Georgetown, Tex.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Xenopus extract reconstitution plus live-cell imaging, site-specific phospho-mutants, single lab","pmids":["24675888"],"is_preprint":false},{"year":2018,"finding":"Cyclin A/Cdk1 phosphorylates Bora to promote Aurora A-dependent Plk1 activation and mitotic entry. Bora phosphorylation by cyclin A/Cdk1 is both necessary and sufficient for mitotic commitment. A specific Bora site whose phosphorylation by cyclin A/Cdk1 is required for mitotic entry was identified.","method":"In vitro kinase assay, site-directed mutagenesis, Xenopus egg extract experiments, mathematical modeling, cell-based mitotic entry assay","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro reconstitution, site-specific mutagenesis, Xenopus extract validation, mathematical modeling; multiple orthogonal methods","pmids":["29870721"],"is_preprint":false},{"year":2021,"finding":"Phospho-Bora (phosphorylated by CyclinA/B-Cdk1) is a direct activator of Aurora A kinase activity. The key determinants map to a 100 aa region with two TPX2-like motifs and a phosphoSer112–Pro motif through which Bora binds Aurora A. PhosphoSer112 substitutes in trans for the Aurora A T288 phospho-regulatory site, stabilizing an active kinase conformation. These determinants are required for mitotic entry in Xenopus extracts and human cells.","method":"Structural modelling, NMR spectroscopy, in vitro kinase reconstitution, site-directed mutagenesis, Xenopus egg extract, human cell mitotic entry assay","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR structural validation plus mutagenesis plus in vitro reconstitution plus in vivo functional rescue in two systems","pmids":["33771996"],"is_preprint":false},{"year":2015,"finding":"Bora specifically interacted with the tandem BRCT domain of MDC1 in a phosphorylation-dependent manner, and overexpression of Bora abolished irradiation-induced MDC1 foci formation. Bora knockdown increased G2-M arrest, increased Chk2 phosphorylation, and accelerated DNA double-strand break repair after irradiation.","method":"Co-immunoprecipitation (Bora–MDC1 interaction), siRNA knockdown, colony formation assay, γ-H2AX foci quantification, immunofluorescence","journal":"PloS one","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single co-IP and cell-based assays, single lab, limited mechanistic follow-up","pmids":["25742493"],"is_preprint":false},{"year":2013,"finding":"In mouse oocyte meiosis, Bora co-localizes with α-tubulin at the spindle during prometaphase/metaphase but dissociates at anaphase/telophase. Inhibition or depletion of Bora caused defective spindles, misaligned chromosomes, and impaired polar body extrusion, along with loss of Aurora A and Plk1 from the spindle.","method":"Immunofluorescence co-localization, antibody microinjection, siRNA microinjection, spindle/chromosome alignment assay","journal":"Molecular reproduction and development","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — direct loss-of-function (antibody + siRNA) with specific spindle and chromosome phenotypes, localization by immunofluorescence","pmids":["23610072"],"is_preprint":false},{"year":2025,"finding":"PKA (cAMP-dependent protein kinase) phosphorylates Bora to enable it to bind Aurora A and recruit Aurora A to the Bora–Plk1 complex in G2, facilitating Aurora A-dependent Plk1 activation. Disruption of PKA-mediated Bora phosphorylation or the Bora–Aurora A interaction impairs Plk1 activation and delays the G2/M transition, including after DNA damage checkpoint recovery.","method":"In vitro kinase assay, phospho-mimetic and phospho-dead Bora mutants, co-immunoprecipitation, cell-based Plk1 activation and mitotic entry assay, cAMP signaling manipulation","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical and cell-based orthogonal methods, single lab, peer-reviewed","pmids":["40849432"],"is_preprint":false},{"year":2026,"finding":"Crystal/structural models of the Aurora A/Bora and Aurora A/Bora/PLK1 ternary complex, validated by mutagenesis, biochemical assays and NMR, show that Bora wraps around the N-lobe of Aurora A; CDK1-phosphorylated Ser112 on Bora mimics Aurora A activation loop phosphorylation within a TPX2-like motif. In the ternary complex, Bora bridges Aurora A and PLK1, orienting the PLK1 activation loop toward the Aurora A active site. Bora residues 56–66 form a critical interface with a conserved pocket on the PLK1 C-helix (analogous to the TPX2 Y-pocket of Aurora A). Aurora A phosphorylation of Bora Ser59 further increases PLK1 phosphorylation efficiency.","method":"Structural modelling, NMR spectroscopy, site-directed mutagenesis, in vitro biochemical kinase assays","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 1 / Moderate — structural models validated with NMR and mutagenesis plus biochemical assays; single lab but multiple orthogonal methods in one rigorous study","pmids":["41606264"],"is_preprint":false},{"year":2025,"finding":"Bora is the main driver for mitotic entry, DNA-damage recovery, and centrosome maturation among Plk1 coactivators (Bora, Cep192, Cenexin), activating a distinct cytoplasmic Plk1 pool. Centriole disengagement is mainly regulated by Cep192 and Cenexin, not Bora. These three coactivators control different cell-cycle steps via distinct Plk1 pools.","method":"siRNA knockdown of individual coactivators, cell cycle stage-specific phenotypic readouts, human cell imaging","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — systematic loss-of-function with multiple cell cycle readouts; preprint, single lab","pmids":[],"is_preprint":true},{"year":2025,"finding":"Aurora A:Bora complex specifically phosphorylates PLK1 Thr210 in vitro, while Aurora A alone, other Aurora A:activator complexes, and Aurora B:INCENP fail to do so even at high concentrations. A transient interaction between Bora and PLK1 (identified by structural modelling, confirmed by mutagenesis) is uniquely required for Thr210 phosphorylation. Mutating PLK1 Lys208 to Arg eliminates the Bora requirement, converting PLK1 into a substrate for nearly all Aurora kinases.","method":"In vitro kinase reconstitution, site-directed mutagenesis (PLK1 K208R, Bora interface mutants), structural modelling","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro reconstitution with mutagenesis; preprint, single lab","pmids":[],"is_preprint":true},{"year":2025,"finding":"Structural modelling and in vitro assays show that Bora wraps around the N-terminal lobe of Aurora A, positioning phospho-Ser112 near the Aurora A T-loop to mimic T-loop phosphorylation. Bora also transiently interacts with the alpha-C helix of the Plk1 kinase domain through a conserved motif, directing Aurora A activity toward the Plk1 T-loop. This conserved Bora motif is required for Plk1 activation in vitro and for mitotic entry in Xenopus egg extracts.","method":"AlphaFold3 structural modelling, in vitro reconstitution (MITOKINAC assay in E. coli), 39 Bora variants, Xenopus egg extract mitotic entry assay","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — structural modelling validated by systematic mutagenesis and in vitro reconstitution plus Xenopus extract; preprint, independent lab","pmids":[],"is_preprint":true}],"current_model":"Bora is an intrinsically disordered co-factor that acts as a molecular bridge during the G2-to-mitosis transition: first phosphorylated on conserved N-terminal sites (including Ser112) by cyclin A/B–Cdk1 (and PKA), phospho-Bora wraps around the N-lobe of Aurora A, with its phospho-Ser112 mimicking Aurora A T-loop phosphorylation to activate the kinase; simultaneously, a conserved Bora interface contacts the alpha-C helix of PLK1 to orient its T-loop (Thr210) toward the Aurora A active site for phosphorylation and activation — a reaction strictly dependent on the Aurora A–Bora–Plk1 ternary complex; once PLK1 is active, PLK1 phosphorylates a DSGxxT degron in Bora targeting it for SCF-β-TrCP-mediated proteasomal degradation, while during DNA damage the DDR (via ATR-mediated Bora phosphorylation and disruption of the Aurora A–Bora interaction) prevents Plk1 activation and enforces G2 arrest."},"narrative":{"mechanistic_narrative":"BORA (Aurora Borealis) is an intrinsically disordered cell-cycle co-factor that licenses the G2-to-mitosis transition by templating the activation of Aurora A and PLK1 [PMID:16890155, PMID:18566290]. It first integrates cell-cycle kinase input: cyclin A/B–Cdk1 phosphorylates conserved N-terminal Sp/Tp sites in Bora (including the cyclin-binding motifs), a modification both necessary and sufficient for mitotic commitment, and PKA contributes an additional priming phosphorylation that enables Bora to bind Aurora A in G2 [PMID:27068477, PMID:29870721, PMID:40849432]. Phospho-Bora is a direct allosteric activator of Aurora A: it wraps around the kinase N-lobe through TPX2-like motifs, and its phospho-Ser112 substitutes in trans for the Aurora A T-loop phospho-site to stabilize an active conformation [PMID:33771996, PMID:41606264]. Within an Aurora A–Bora–PLK1 ternary complex, Bora bridges the two kinases — contacting the PLK1 αC-helix through a conserved interface (residues ~56–66) to orient the PLK1 activation loop toward the Aurora A active site, making T210 phosphorylation of PLK1 strictly dependent on this assembly [PMID:18566290, PMID:41606264]. Activated PLK1 in turn phosphorylates a conserved DSGxxT degron in Bora, driving SCF-β-TrCP–mediated proteasomal degradation, which couples Bora activity to its own turnover and shapes mitotic progression, spindle stability, and kinetochore tension [PMID:18378770]. The pathway is a node for the DNA damage response: ATR-driven Bora phosphorylation and disruption of the Aurora A–Bora interaction abolish PLK1 T210 phosphorylation to enforce G2 arrest [PMID:23592782, PMID:27721411]. Bora is conserved as the C. elegans SPAT-1, where it acts with PLK-1 to couple cell-cycle progression to PAR polarity [PMID:20823068], and it localizes to the meiotic spindle where it is required for spindle assembly and chromosome alignment [PMID:23610072].","teleology":[{"year":2006,"claim":"Established Bora as a dedicated Aurora A activator, answering how Aurora A is switched on at mitotic entry rather than acting constitutively.","evidence":"In vitro kinase reconstitution with human and Drosophila proteins, genetic rescue in Drosophila, and imaging of Cdc2-dependent nuclear-to-cytoplasmic translocation","pmids":["16890155"],"confidence":"High","gaps":["Did not define the Bora sites or structural basis of Aurora A binding","Did not link Bora to downstream kinases beyond Aurora A"]},{"year":2008,"claim":"Defined Bora as the bridge that channels Aurora A activity onto PLK1, explaining how the G2-M transition is triggered through PLK1 T210 phosphorylation.","evidence":"Co-IP, in vitro kinase assays, and RNAi knockdown with mitotic-entry readouts placing Bora upstream of Aurora A–dependent PLK1 activation and Cdk1","pmids":["18566290"],"confidence":"High","gaps":["Structural mechanism of how Bora orients the PLK1 T-loop not yet resolved","Did not address how Bora levels are controlled after activation"]},{"year":2008,"claim":"Showed Bora activity is self-limiting, revealing a feedback loop in which the kinase Bora activates triggers Bora's own destruction to permit ordered mitotic progression.","evidence":"Degron mutagenesis, co-IP with β-TrCP, in vitro PLK1 phosphorylation, and RNAi with spindle/kinetochore phenotypes","pmids":["18378770"],"confidence":"High","gaps":["How a residual Bora pool escapes degradation to sustain mitotic PLK1 activity not addressed","Direct structural recognition of the phospho-degron by β-TrCP not shown"]},{"year":2010,"claim":"Demonstrated evolutionary conservation and a PLK-centric branch of Bora function, linking the cell-cycle co-factor to cell polarity in an Aurora A–independent context.","evidence":"RNAi depletion, genetic epistasis with par-2, co-IP, and immunofluorescence of SPAT-1/PLK-1 in C. elegans","pmids":["20823068"],"confidence":"Medium","gaps":["Whether the polarity role generalizes to mammalian Bora unknown","Biochemical basis of Aurora A independence in worm not resolved"]},{"year":2013,"claim":"Refined the model from a purely interphase event to a mitotic bistable switch, showing a retained Bora–Aurora A pool sustains PLK1 T210 phosphorylation during mitosis.","evidence":"Quantitative phosphorylation assays, siRNA depletion, and IP with cell-cycle synchronization","pmids":["24338364"],"confidence":"Medium","gaps":["Mechanism protecting the residual Bora pool from degradation unresolved","Single lab, quantitative thresholds not independently validated"]},{"year":2013,"claim":"Connected Bora to the DNA damage checkpoint, identifying ATR-driven Bora degradation as a route to PLK1 inhibition and G2 arrest.","evidence":"In vitro ATR kinase assay on Bora Thr-501, T501A mutagenesis, co-IP with β-TrCP, and cell-based G2/M checkpoint assay","pmids":["23592782"],"confidence":"Medium","gaps":["Relative contribution of degradation versus interaction disruption to arrest not separated here","Single lab"]},{"year":2013,"claim":"Added a Pin1/proline-isomerase layer of Bora regulation, showing phospho-dependent control of Bora localization and stability as a brake on mitotic entry, itself opposed by Aurora A.","evidence":"Co-IP, Bora Ser274/278 and Pin1 Ser16 mutagenesis, localization assays, and in vitro kinase assay","pmids":["23970419"],"confidence":"Medium","gaps":["Physiological weight of Pin1 regulation relative to Cdk1 priming unclear","Single lab"]},{"year":2013,"claim":"Extended Bora function to meiosis, establishing it as a spindle-associated factor required for Aurora A/PLK1 spindle recruitment and chromosome alignment in oocytes.","evidence":"Immunofluorescence co-localization with α-tubulin, antibody and siRNA microinjection with spindle/chromosome phenotypes in mouse oocytes","pmids":["23610072"],"confidence":"Medium","gaps":["Whether spindle localization reflects a complex-bound or free Bora pool unknown","Direct binding partners at the spindle not defined"]},{"year":2014,"claim":"Mapped Cdk-site phosphorylation as a switch controlling Bora degradation timing, framing Cdk1 control of Bora as an incoherent feedforward loop driving Plx1/PLK oscillations.","evidence":"Xenopus CSF extract biochemistry, T52 phospho-mutants, calcineurin treatment, and live-cell GFP-Bora imaging","pmids":["24675888"],"confidence":"Medium","gaps":["Mapping of Xenopus T52 to human Bora sites not fully resolved","Single lab"]},{"year":2015,"claim":"Established the input phosphorylation that activates Bora, showing Cdk1/CDK-1 phosphorylation of the Bora N-terminus is required for Aurora A–dependent PLK1 T-loop phosphorylation across species.","evidence":"In vitro reconstitution of the CDK-1→Bora→Aurora A→PLK1 cascade, phospho-site mutagenesis, and C. elegans genetics with human-cell confirmation","pmids":["25753036"],"confidence":"High","gaps":["Which individual N-terminal sites are rate-limiting not fully dissected here","Structural consequence of phosphorylation not yet shown"]},{"year":2015,"claim":"Proposed a distinct Bora link to DNA damage signaling through MDC1, but with limited mechanistic depth.","evidence":"Co-IP of Bora with the MDC1 BRCT domain, siRNA knockdown, γ-H2AX foci quantification, and colony formation","pmids":["25742493"],"confidence":"Low","gaps":["Single co-IP without reciprocal validation or structural follow-up","Relationship to the Aurora A–Bora–PLK1 axis unresolved","Not independently confirmed"]},{"year":2016,"claim":"Pinned the DNA damage response to disruption of the Aurora A–Bora interaction, showing loss of PLK1 T210 phosphorylation fully accounts for DDR-induced PLK1 inhibition.","evidence":"FRET PLK1 activity biosensor, DDR-refractory Aurora A mutants, and an Aurora A–Bora fusion that rescues PLK1 activity under damage","pmids":["27721411"],"confidence":"Medium","gaps":["The upstream signal severing the Aurora A–Bora contact not fully defined","Single lab"]},{"year":2016,"claim":"Resolved which Bora phosphosites and cyclin-binding motifs are functionally required, tying Cdk1 input directly to mitotic entry and DNA-damage recovery in human cells.","evidence":"In vitro kinase assays, mutagenesis of three Sp/Tp sites and two cyclin-binding motifs, FRET PLK1 biosensor, and C. elegans genetics","pmids":["27068477"],"confidence":"High","gaps":["Did not yet provide a structural model of the activated Bora–Aurora A complex"]},{"year":2018,"claim":"Identified cyclin A/Cdk1 as necessary and sufficient for the Bora phosphorylation that commits cells to mitosis, defining the decisive upstream trigger.","evidence":"In vitro kinase assays, site mutagenesis, Xenopus egg extract, mathematical modeling, and cell-based mitotic-entry assays","pmids":["29870721"],"confidence":"High","gaps":["How cyclin A specificity is achieved over cyclin B not fully resolved","Structural basis of phospho-Bora action still pending at this stage"]},{"year":2021,"claim":"Provided the structural mechanism of Aurora A activation, showing phospho-Bora wraps the Aurora A N-lobe and phospho-Ser112 substitutes in trans for the T288 phospho-site.","evidence":"NMR spectroscopy, structural modeling, in vitro kinase reconstitution, mutagenesis, Xenopus extract, and human-cell mitotic entry","pmids":["33771996"],"confidence":"High","gaps":["Did not yet visualize the ternary Aurora A–Bora–PLK1 arrangement","PLK1-contacting interface of Bora not defined in this work"]},{"year":2025,"claim":"Added PKA as a second kinase input that primes Bora to recruit Aurora A in G2, broadening the regulatory logic beyond Cdk1 and linking cAMP signaling to mitotic entry and checkpoint recovery.","evidence":"In vitro kinase assays, phospho-mimetic/dead Bora mutants, co-IP, cell-based PLK1 activation/mitotic entry assays, and cAMP manipulation","pmids":["40849432"],"confidence":"Medium","gaps":["PKA target site(s) on Bora and their hierarchy with Cdk1 sites not fully ordered","Single lab"]},{"year":2025,"claim":"Distinguished Bora from other PLK1 coactivators, assigning it to a cytoplasmic PLK1 pool driving mitotic entry, DNA-damage recovery and centrosome maturation while excluding it from centriole disengagement.","evidence":"siRNA knockdown of individual coactivators (Bora, Cep192, Cenexin) with cell-cycle-stage-specific phenotypes (preprint)","pmids":[],"confidence":"Medium","gaps":["Preprint, not peer-reviewed","Molecular basis for pool-specific targeting of PLK1 not established"]},{"year":2026,"claim":"Delivered the structural model of the full ternary complex, showing how Bora simultaneously activates Aurora A and orients PLK1, completing the mechanistic picture of dual-kinase activation.","evidence":"Structural modeling, NMR, mutagenesis, and in vitro kinase assays defining the Bora–PLK1 αC-helix interface (residues 56–66) and Aurora A phosphorylation of Bora Ser59","pmids":["41606264"],"confidence":"High","gaps":["Single lab; experimental high-resolution crystal structure of the full assembly not yet reported","Dynamics of complex assembly/disassembly in cells not directly observed"]},{"year":null,"claim":"How the temporal sequence of multiple kinase inputs (cyclin A/Cdk1, cyclin B/Cdk1, PKA) and competing brakes (Pin1, ATR, β-TrCP) is integrated to produce a sharp, switch-like commitment decision remains incompletely defined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["Quantitative hierarchy and ordering of activating phosphosites unresolved","Mechanism protecting the mitotic Bora pool from degradation not established","In vivo structure of the active ternary complex not directly determined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,12,16]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,16]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,17]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0,1,2,11]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[5,9]}],"complexes":["Aurora A–Bora–PLK1 ternary complex"],"partners":["AURKA","PLK1","BTRC","CDK1","PIN1","PRKACA","ATR","MDC1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q6PGQ7","full_name":"Protein aurora borealis","aliases":[],"length_aa":559,"mass_kda":61.2,"function":"Required for the activation of AURKA at the onset of mitosis","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q6PGQ7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/BORA","classification":"Common Essential","n_dependent_lines":1017,"n_total_lines":1208,"dependency_fraction":0.8418874172185431},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/BORA","total_profiled":1310},"omim":[{"mim_id":"610510","title":"AURORA BOREALIS; BORA","url":"https://www.omim.org/entry/610510"},{"mim_id":"609931","title":"MYOSIN LIGHT CHAIN 6, ALKALI, SMOOTH MUSCLE AND NONMUSCLE; MYL6","url":"https://www.omim.org/entry/609931"},{"mim_id":"603690","title":"SOLUTE CARRIER FAMILY 33 (ACETYL-CoA TRANSPORTER), MEMBER 1; SLC33A1","url":"https://www.omim.org/entry/603690"},{"mim_id":"603072","title":"AURORA KINASE A; AURKA","url":"https://www.omim.org/entry/603072"},{"mim_id":"602098","title":"POLO-LIKE KINASE 1; PLK1","url":"https://www.omim.org/entry/602098"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Nucleoli fibrillar center","reliability":"Approved"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/BORA"},"hgnc":{"alias_symbol":["FLJ22624"],"prev_symbol":["C13orf34"]},"alphafold":{"accession":"Q6PGQ7","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6PGQ7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q6PGQ7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q6PGQ7-F1-predicted_aligned_error_v6.png","plddt_mean":50.91},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=BORA","jax_strain_url":"https://www.jax.org/strain/search?query=BORA"},"sequence":{"accession":"Q6PGQ7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q6PGQ7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q6PGQ7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6PGQ7"}},"corpus_meta":[{"pmid":"18566290","id":"PMC_18566290","title":"Bora and the kinase Aurora a cooperatively activate the kinase Plk1 and control mitotic entry.","date":"2008","source":"Science (New 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Both Drosophila and human Bora bind Aurora-A and activate the kinase in vitro. In interphase, Bora is nuclear; upon mitotic entry it translocates to the cytoplasm in a Cdc2-dependent manner, where it activates Aurora-A.\",\n      \"method\": \"In vitro kinase assay, genetic rescue (bora mutants rescued by Bora overexpression in Drosophila PNS), subcellular fractionation/live imaging, co-immunoprecipitation\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro kinase reconstitution with human and Drosophila proteins, genetic epistasis in vivo, localization by imaging, replicated across species\",\n      \"pmids\": [\"16890155\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Bora interacts with Plk1 and controls accessibility of the Plk1 activation loop (T210) for phosphorylation and activation by Aurora A, thereby driving the G2-M transition. Bora accumulates in G2 and promotes Aurora-A-mediated Plk1 activation leading to Cdk1 activation and mitotic entry.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, RNAi knockdown with mitotic entry readout, functional genomics/proteomics\",\n      \"journal\": \"Science (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro reconstitution of the Aurora A–Bora–Plk1 activation cascade, co-IP, and functional knockdown with defined phenotype; foundational paper replicated by multiple labs\",\n      \"pmids\": [\"18566290\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Bora is degraded by the SCF-β-TrCP ubiquitin ligase in mitosis. Plk1 phosphorylates a conserved DSGxxT degron in Bora, promoting its interaction with β-TrCP. Stabilization of Bora (degron mutant) prolongs metaphase and delays anaphase. Bora knockdown activates the spindle checkpoint and delays sister chromatid segregation; Bora promotes spindle stability, microtubule polymerization, and kinetochore tension.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, proteasome inhibitor treatment, site-directed mutagenesis of degron, RNAi knockdown with spindle/kinetochore phenotype readout\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — mutagenesis of degron + co-IP with β-TrCP + in vitro Plk1 phosphorylation + multiple cellular phenotypes\",\n      \"pmids\": [\"18378770\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"In C. elegans, the Bora ortholog SPAT-1 acts with PLK-1 (not Aurora A/AIR-1) to regulate PAR polarity and cell cycle progression. SPAT-1 binds PLK-1; SPAT-1 and PLK-1 depletion cause similar cell division and polarity defects distinct from AIR-1 depletion. SPAT-1 is enriched in posterior cells in a PAR polarity- and PLK-1-dependent manner.\",\n      \"method\": \"RNAi depletion, genetic epistasis (par-2 mutant rescue), co-immunoprecipitation (SPAT-1/PLK-1 interaction), immunofluorescence localization\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — reciprocal epistasis and co-IP in C. elegans, single lab, multiple readouts\",\n      \"pmids\": [\"20823068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"A fraction of Bora is retained in mitosis and is essential for continued Aurora-A-dependent T210 phosphorylation of Plk1. The Bora–Aurora-A complex remains the major activator of Plk1 in mitosis, functioning as a bistable switch.\",\n      \"method\": \"Quantitative phosphorylation assays, RNAi/siRNA depletion, immunoprecipitation, cell cycle synchronization with kinase activity readout\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical and cell-based methods, single lab\",\n      \"pmids\": [\"24338364\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"ATR phosphorylates Bora at Thr-501 following UV irradiation; phospho-Thr-501 is recognized by SCF-β-TrCP, targeting Bora for degradation. Bora degradation inhibits Plk1 activation and contributes to DNA damage-induced G2 arrest.\",\n      \"method\": \"In vitro kinase assay (ATR on Bora), co-immunoprecipitation, site-directed mutagenesis (T501A), cell-based G2/M checkpoint assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro kinase assay plus mutagenesis and co-IP, single lab\",\n      \"pmids\": [\"23592782\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Pin1 interacts with Bora phosphorylated at Ser274 and Ser278, alters Bora's cytoplasmic translocation, and promotes its premature β-TrCP-mediated degradation, delaying mitotic entry. Aurora-A phosphorylates Pin1 at Ser16, suppressing Pin1's ability to bind Bora and act as a negative G2/M regulator.\",\n      \"method\": \"Co-immunoprecipitation, site-directed mutagenesis (Bora Ser274/278, Pin1 Ser16), subcellular localization assay, in vitro kinase assay, cell cycle progression readout\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — multiple co-IPs, mutagenesis, and cellular assays; single lab\",\n      \"pmids\": [\"23970419\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CDK-1 phosphorylates SPAT-1/Bora at multiple sites in its N-terminus to regulate its interaction with PLK-1 and trigger mitotic entry. Phospho-SPAT-1 activates PLK-1 by stimulating Aurora A-dependent T-loop phosphorylation in vitro. Phosphorylation of human Bora by Cdk1 likewise promotes Aurora A-dependent Plk1 T210 phosphorylation, indicating conservation.\",\n      \"method\": \"In vitro kinase assay, site-directed mutagenesis (CDK-1 phosphorylation sites), C. elegans genetics (non-phosphorylatable SPAT-1 mutants), co-immunoprecipitation (SPAT-1/PLK-1)\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro reconstitution of CDK-1→Bora→Aurora A→Plk1 cascade, mutagenesis, genetic validation in vivo, conservation confirmed in human cells\",\n      \"pmids\": [\"25753036\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Cdk1 phosphorylates the N-terminus of Bora at three conserved Sp/Tp residues; mutation of these sites or the two cyclin-binding motifs in Bora abrogates its ability to promote Aurora A-dependent Plk1 activation. Bora carrying these mutations cannot sustain mitotic entry after DNA damage in human cells.\",\n      \"method\": \"In vitro kinase assay, site-directed mutagenesis, FRET-based Plk1 activity biosensor in human cells, C. elegans genetics\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro reconstitution with mutagenesis, live-cell FRET biosensor, and in vivo genetic validation across two species\",\n      \"pmids\": [\"27068477\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"DNA damage inhibits Plk1 by disrupting Aurora A recruitment to the Bora–Plk1 complex. Loss of Plk1-T210 phosphorylation is entirely responsible for DDR-induced Plk1 inhibition. A direct Aurora A–Bora fusion prevented DNA damage-induced loss of Plk1 activity, showing the DDR targets the Aurora A–Bora interaction.\",\n      \"method\": \"FRET-based Plk1 activity biosensor, Aurora A mutants refractory to DDR, Aurora A–Bora fusion protein expression, quantitative T210 phosphorylation analysis\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live-cell FRET biosensor plus fusion-protein rescue, single lab, multiple orthogonal approaches\",\n      \"pmids\": [\"27721411\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In Xenopus CSF extracts, phosphorylation of Bora on the Cdk consensus site T52 blocks Bora degradation by Plx1. Calcineurin dephosphorylates T52 upon fertilization, triggering Plx1 oscillations. In somatic cells, GFP-Bora degradation stops upon mitotic entry when Cdk1 activity is high, suggesting Cdk1 controls Bora through an incoherent feedforward loop.\",\n      \"method\": \"Xenopus egg extract biochemistry, phospho-mutant analysis, phosphatase (calcineurin) treatment, live-cell imaging of GFP-Bora\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Xenopus extract reconstitution plus live-cell imaging, site-specific phospho-mutants, single lab\",\n      \"pmids\": [\"24675888\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Cyclin A/Cdk1 phosphorylates Bora to promote Aurora A-dependent Plk1 activation and mitotic entry. Bora phosphorylation by cyclin A/Cdk1 is both necessary and sufficient for mitotic commitment. A specific Bora site whose phosphorylation by cyclin A/Cdk1 is required for mitotic entry was identified.\",\n      \"method\": \"In vitro kinase assay, site-directed mutagenesis, Xenopus egg extract experiments, mathematical modeling, cell-based mitotic entry assay\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro reconstitution, site-specific mutagenesis, Xenopus extract validation, mathematical modeling; multiple orthogonal methods\",\n      \"pmids\": [\"29870721\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Phospho-Bora (phosphorylated by CyclinA/B-Cdk1) is a direct activator of Aurora A kinase activity. The key determinants map to a 100 aa region with two TPX2-like motifs and a phosphoSer112–Pro motif through which Bora binds Aurora A. PhosphoSer112 substitutes in trans for the Aurora A T288 phospho-regulatory site, stabilizing an active kinase conformation. These determinants are required for mitotic entry in Xenopus extracts and human cells.\",\n      \"method\": \"Structural modelling, NMR spectroscopy, in vitro kinase reconstitution, site-directed mutagenesis, Xenopus egg extract, human cell mitotic entry assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR structural validation plus mutagenesis plus in vitro reconstitution plus in vivo functional rescue in two systems\",\n      \"pmids\": [\"33771996\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Bora specifically interacted with the tandem BRCT domain of MDC1 in a phosphorylation-dependent manner, and overexpression of Bora abolished irradiation-induced MDC1 foci formation. Bora knockdown increased G2-M arrest, increased Chk2 phosphorylation, and accelerated DNA double-strand break repair after irradiation.\",\n      \"method\": \"Co-immunoprecipitation (Bora–MDC1 interaction), siRNA knockdown, colony formation assay, γ-H2AX foci quantification, immunofluorescence\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single co-IP and cell-based assays, single lab, limited mechanistic follow-up\",\n      \"pmids\": [\"25742493\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In mouse oocyte meiosis, Bora co-localizes with α-tubulin at the spindle during prometaphase/metaphase but dissociates at anaphase/telophase. Inhibition or depletion of Bora caused defective spindles, misaligned chromosomes, and impaired polar body extrusion, along with loss of Aurora A and Plk1 from the spindle.\",\n      \"method\": \"Immunofluorescence co-localization, antibody microinjection, siRNA microinjection, spindle/chromosome alignment assay\",\n      \"journal\": \"Molecular reproduction and development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — direct loss-of-function (antibody + siRNA) with specific spindle and chromosome phenotypes, localization by immunofluorescence\",\n      \"pmids\": [\"23610072\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PKA (cAMP-dependent protein kinase) phosphorylates Bora to enable it to bind Aurora A and recruit Aurora A to the Bora–Plk1 complex in G2, facilitating Aurora A-dependent Plk1 activation. Disruption of PKA-mediated Bora phosphorylation or the Bora–Aurora A interaction impairs Plk1 activation and delays the G2/M transition, including after DNA damage checkpoint recovery.\",\n      \"method\": \"In vitro kinase assay, phospho-mimetic and phospho-dead Bora mutants, co-immunoprecipitation, cell-based Plk1 activation and mitotic entry assay, cAMP signaling manipulation\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical and cell-based orthogonal methods, single lab, peer-reviewed\",\n      \"pmids\": [\"40849432\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Crystal/structural models of the Aurora A/Bora and Aurora A/Bora/PLK1 ternary complex, validated by mutagenesis, biochemical assays and NMR, show that Bora wraps around the N-lobe of Aurora A; CDK1-phosphorylated Ser112 on Bora mimics Aurora A activation loop phosphorylation within a TPX2-like motif. In the ternary complex, Bora bridges Aurora A and PLK1, orienting the PLK1 activation loop toward the Aurora A active site. Bora residues 56–66 form a critical interface with a conserved pocket on the PLK1 C-helix (analogous to the TPX2 Y-pocket of Aurora A). Aurora A phosphorylation of Bora Ser59 further increases PLK1 phosphorylation efficiency.\",\n      \"method\": \"Structural modelling, NMR spectroscopy, site-directed mutagenesis, in vitro biochemical kinase assays\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — structural models validated with NMR and mutagenesis plus biochemical assays; single lab but multiple orthogonal methods in one rigorous study\",\n      \"pmids\": [\"41606264\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Bora is the main driver for mitotic entry, DNA-damage recovery, and centrosome maturation among Plk1 coactivators (Bora, Cep192, Cenexin), activating a distinct cytoplasmic Plk1 pool. Centriole disengagement is mainly regulated by Cep192 and Cenexin, not Bora. These three coactivators control different cell-cycle steps via distinct Plk1 pools.\",\n      \"method\": \"siRNA knockdown of individual coactivators, cell cycle stage-specific phenotypic readouts, human cell imaging\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — systematic loss-of-function with multiple cell cycle readouts; preprint, single lab\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Aurora A:Bora complex specifically phosphorylates PLK1 Thr210 in vitro, while Aurora A alone, other Aurora A:activator complexes, and Aurora B:INCENP fail to do so even at high concentrations. A transient interaction between Bora and PLK1 (identified by structural modelling, confirmed by mutagenesis) is uniquely required for Thr210 phosphorylation. Mutating PLK1 Lys208 to Arg eliminates the Bora requirement, converting PLK1 into a substrate for nearly all Aurora kinases.\",\n      \"method\": \"In vitro kinase reconstitution, site-directed mutagenesis (PLK1 K208R, Bora interface mutants), structural modelling\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro reconstitution with mutagenesis; preprint, single lab\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Structural modelling and in vitro assays show that Bora wraps around the N-terminal lobe of Aurora A, positioning phospho-Ser112 near the Aurora A T-loop to mimic T-loop phosphorylation. Bora also transiently interacts with the alpha-C helix of the Plk1 kinase domain through a conserved motif, directing Aurora A activity toward the Plk1 T-loop. This conserved Bora motif is required for Plk1 activation in vitro and for mitotic entry in Xenopus egg extracts.\",\n      \"method\": \"AlphaFold3 structural modelling, in vitro reconstitution (MITOKINAC assay in E. coli), 39 Bora variants, Xenopus egg extract mitotic entry assay\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — structural modelling validated by systematic mutagenesis and in vitro reconstitution plus Xenopus extract; preprint, independent lab\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"Bora is an intrinsically disordered co-factor that acts as a molecular bridge during the G2-to-mitosis transition: first phosphorylated on conserved N-terminal sites (including Ser112) by cyclin A/B–Cdk1 (and PKA), phospho-Bora wraps around the N-lobe of Aurora A, with its phospho-Ser112 mimicking Aurora A T-loop phosphorylation to activate the kinase; simultaneously, a conserved Bora interface contacts the alpha-C helix of PLK1 to orient its T-loop (Thr210) toward the Aurora A active site for phosphorylation and activation — a reaction strictly dependent on the Aurora A–Bora–Plk1 ternary complex; once PLK1 is active, PLK1 phosphorylates a DSGxxT degron in Bora targeting it for SCF-β-TrCP-mediated proteasomal degradation, while during DNA damage the DDR (via ATR-mediated Bora phosphorylation and disruption of the Aurora A–Bora interaction) prevents Plk1 activation and enforces G2 arrest.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"BORA (Aurora Borealis) is an intrinsically disordered cell-cycle co-factor that licenses the G2-to-mitosis transition by templating the activation of Aurora A and PLK1 [#0, #1]. It first integrates cell-cycle kinase input: cyclin A/B–Cdk1 phosphorylates conserved N-terminal Sp/Tp sites in Bora (including the cyclin-binding motifs), a modification both necessary and sufficient for mitotic commitment, and PKA contributes an additional priming phosphorylation that enables Bora to bind Aurora A in G2 [#8, #11, #15]. Phospho-Bora is a direct allosteric activator of Aurora A: it wraps around the kinase N-lobe through TPX2-like motifs, and its phospho-Ser112 substitutes in trans for the Aurora A T-loop phospho-site to stabilize an active conformation [#12, #16]. Within an Aurora A–Bora–PLK1 ternary complex, Bora bridges the two kinases — contacting the PLK1 αC-helix through a conserved interface (residues ~56–66) to orient the PLK1 activation loop toward the Aurora A active site, making T210 phosphorylation of PLK1 strictly dependent on this assembly [#1, #16]. Activated PLK1 in turn phosphorylates a conserved DSGxxT degron in Bora, driving SCF-β-TrCP–mediated proteasomal degradation, which couples Bora activity to its own turnover and shapes mitotic progression, spindle stability, and kinetochore tension [#2]. The pathway is a node for the DNA damage response: ATR-driven Bora phosphorylation and disruption of the Aurora A–Bora interaction abolish PLK1 T210 phosphorylation to enforce G2 arrest [#5, #9]. Bora is conserved as the C. elegans SPAT-1, where it acts with PLK-1 to couple cell-cycle progression to PAR polarity [#3], and it localizes to the meiotic spindle where it is required for spindle assembly and chromosome alignment [#14].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Established Bora as a dedicated Aurora A activator, answering how Aurora A is switched on at mitotic entry rather than acting constitutively.\",\n      \"evidence\": \"In vitro kinase reconstitution with human and Drosophila proteins, genetic rescue in Drosophila, and imaging of Cdc2-dependent nuclear-to-cytoplasmic translocation\",\n      \"pmids\": [\"16890155\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the Bora sites or structural basis of Aurora A binding\", \"Did not link Bora to downstream kinases beyond Aurora A\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Defined Bora as the bridge that channels Aurora A activity onto PLK1, explaining how the G2-M transition is triggered through PLK1 T210 phosphorylation.\",\n      \"evidence\": \"Co-IP, in vitro kinase assays, and RNAi knockdown with mitotic-entry readouts placing Bora upstream of Aurora A–dependent PLK1 activation and Cdk1\",\n      \"pmids\": [\"18566290\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural mechanism of how Bora orients the PLK1 T-loop not yet resolved\", \"Did not address how Bora levels are controlled after activation\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Showed Bora activity is self-limiting, revealing a feedback loop in which the kinase Bora activates triggers Bora's own destruction to permit ordered mitotic progression.\",\n      \"evidence\": \"Degron mutagenesis, co-IP with β-TrCP, in vitro PLK1 phosphorylation, and RNAi with spindle/kinetochore phenotypes\",\n      \"pmids\": [\"18378770\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How a residual Bora pool escapes degradation to sustain mitotic PLK1 activity not addressed\", \"Direct structural recognition of the phospho-degron by β-TrCP not shown\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Demonstrated evolutionary conservation and a PLK-centric branch of Bora function, linking the cell-cycle co-factor to cell polarity in an Aurora A–independent context.\",\n      \"evidence\": \"RNAi depletion, genetic epistasis with par-2, co-IP, and immunofluorescence of SPAT-1/PLK-1 in C. elegans\",\n      \"pmids\": [\"20823068\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether the polarity role generalizes to mammalian Bora unknown\", \"Biochemical basis of Aurora A independence in worm not resolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Refined the model from a purely interphase event to a mitotic bistable switch, showing a retained Bora–Aurora A pool sustains PLK1 T210 phosphorylation during mitosis.\",\n      \"evidence\": \"Quantitative phosphorylation assays, siRNA depletion, and IP with cell-cycle synchronization\",\n      \"pmids\": [\"24338364\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism protecting the residual Bora pool from degradation unresolved\", \"Single lab, quantitative thresholds not independently validated\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Connected Bora to the DNA damage checkpoint, identifying ATR-driven Bora degradation as a route to PLK1 inhibition and G2 arrest.\",\n      \"evidence\": \"In vitro ATR kinase assay on Bora Thr-501, T501A mutagenesis, co-IP with β-TrCP, and cell-based G2/M checkpoint assay\",\n      \"pmids\": [\"23592782\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative contribution of degradation versus interaction disruption to arrest not separated here\", \"Single lab\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Added a Pin1/proline-isomerase layer of Bora regulation, showing phospho-dependent control of Bora localization and stability as a brake on mitotic entry, itself opposed by Aurora A.\",\n      \"evidence\": \"Co-IP, Bora Ser274/278 and Pin1 Ser16 mutagenesis, localization assays, and in vitro kinase assay\",\n      \"pmids\": [\"23970419\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological weight of Pin1 regulation relative to Cdk1 priming unclear\", \"Single lab\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Extended Bora function to meiosis, establishing it as a spindle-associated factor required for Aurora A/PLK1 spindle recruitment and chromosome alignment in oocytes.\",\n      \"evidence\": \"Immunofluorescence co-localization with α-tubulin, antibody and siRNA microinjection with spindle/chromosome phenotypes in mouse oocytes\",\n      \"pmids\": [\"23610072\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether spindle localization reflects a complex-bound or free Bora pool unknown\", \"Direct binding partners at the spindle not defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Mapped Cdk-site phosphorylation as a switch controlling Bora degradation timing, framing Cdk1 control of Bora as an incoherent feedforward loop driving Plx1/PLK oscillations.\",\n      \"evidence\": \"Xenopus CSF extract biochemistry, T52 phospho-mutants, calcineurin treatment, and live-cell GFP-Bora imaging\",\n      \"pmids\": [\"24675888\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mapping of Xenopus T52 to human Bora sites not fully resolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Established the input phosphorylation that activates Bora, showing Cdk1/CDK-1 phosphorylation of the Bora N-terminus is required for Aurora A–dependent PLK1 T-loop phosphorylation across species.\",\n      \"evidence\": \"In vitro reconstitution of the CDK-1→Bora→Aurora A→PLK1 cascade, phospho-site mutagenesis, and C. elegans genetics with human-cell confirmation\",\n      \"pmids\": [\"25753036\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which individual N-terminal sites are rate-limiting not fully dissected here\", \"Structural consequence of phosphorylation not yet shown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Proposed a distinct Bora link to DNA damage signaling through MDC1, but with limited mechanistic depth.\",\n      \"evidence\": \"Co-IP of Bora with the MDC1 BRCT domain, siRNA knockdown, γ-H2AX foci quantification, and colony formation\",\n      \"pmids\": [\"25742493\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single co-IP without reciprocal validation or structural follow-up\", \"Relationship to the Aurora A–Bora–PLK1 axis unresolved\", \"Not independently confirmed\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Pinned the DNA damage response to disruption of the Aurora A–Bora interaction, showing loss of PLK1 T210 phosphorylation fully accounts for DDR-induced PLK1 inhibition.\",\n      \"evidence\": \"FRET PLK1 activity biosensor, DDR-refractory Aurora A mutants, and an Aurora A–Bora fusion that rescues PLK1 activity under damage\",\n      \"pmids\": [\"27721411\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The upstream signal severing the Aurora A–Bora contact not fully defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Resolved which Bora phosphosites and cyclin-binding motifs are functionally required, tying Cdk1 input directly to mitotic entry and DNA-damage recovery in human cells.\",\n      \"evidence\": \"In vitro kinase assays, mutagenesis of three Sp/Tp sites and two cyclin-binding motifs, FRET PLK1 biosensor, and C. elegans genetics\",\n      \"pmids\": [\"27068477\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not yet provide a structural model of the activated Bora–Aurora A complex\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified cyclin A/Cdk1 as necessary and sufficient for the Bora phosphorylation that commits cells to mitosis, defining the decisive upstream trigger.\",\n      \"evidence\": \"In vitro kinase assays, site mutagenesis, Xenopus egg extract, mathematical modeling, and cell-based mitotic-entry assays\",\n      \"pmids\": [\"29870721\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How cyclin A specificity is achieved over cyclin B not fully resolved\", \"Structural basis of phospho-Bora action still pending at this stage\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Provided the structural mechanism of Aurora A activation, showing phospho-Bora wraps the Aurora A N-lobe and phospho-Ser112 substitutes in trans for the T288 phospho-site.\",\n      \"evidence\": \"NMR spectroscopy, structural modeling, in vitro kinase reconstitution, mutagenesis, Xenopus extract, and human-cell mitotic entry\",\n      \"pmids\": [\"33771996\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not yet visualize the ternary Aurora A–Bora–PLK1 arrangement\", \"PLK1-contacting interface of Bora not defined in this work\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Added PKA as a second kinase input that primes Bora to recruit Aurora A in G2, broadening the regulatory logic beyond Cdk1 and linking cAMP signaling to mitotic entry and checkpoint recovery.\",\n      \"evidence\": \"In vitro kinase assays, phospho-mimetic/dead Bora mutants, co-IP, cell-based PLK1 activation/mitotic entry assays, and cAMP manipulation\",\n      \"pmids\": [\"40849432\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"PKA target site(s) on Bora and their hierarchy with Cdk1 sites not fully ordered\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Distinguished Bora from other PLK1 coactivators, assigning it to a cytoplasmic PLK1 pool driving mitotic entry, DNA-damage recovery and centrosome maturation while excluding it from centriole disengagement.\",\n      \"evidence\": \"siRNA knockdown of individual coactivators (Bora, Cep192, Cenexin) with cell-cycle-stage-specific phenotypes (preprint)\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not peer-reviewed\", \"Molecular basis for pool-specific targeting of PLK1 not established\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Delivered the structural model of the full ternary complex, showing how Bora simultaneously activates Aurora A and orients PLK1, completing the mechanistic picture of dual-kinase activation.\",\n      \"evidence\": \"Structural modeling, NMR, mutagenesis, and in vitro kinase assays defining the Bora–PLK1 αC-helix interface (residues 56–66) and Aurora A phosphorylation of Bora Ser59\",\n      \"pmids\": [\"41606264\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Single lab; experimental high-resolution crystal structure of the full assembly not yet reported\", \"Dynamics of complex assembly/disassembly in cells not directly observed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the temporal sequence of multiple kinase inputs (cyclin A/Cdk1, cyclin B/Cdk1, PKA) and competing brakes (Pin1, ATR, β-TrCP) is integrated to produce a sharp, switch-like commitment decision remains incompletely defined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Quantitative hierarchy and ordering of activating phosphosites unresolved\", \"Mechanism protecting the mitotic Bora pool from degradation not established\", \"In vivo structure of the active ternary complex not directly determined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 12, 16]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 16]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 17]},\n      {\"term_id\": \"GO:0005819\", \"supporting_discovery_ids\": [14]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0, 1, 2, 11]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [5, 9]}\n    ],\n    \"complexes\": [\n      \"Aurora A–Bora–PLK1 ternary complex\"\n    ],\n    \"partners\": [\n      \"AURKA\",\n      \"PLK1\",\n      \"BTRC\",\n      \"CDK1\",\n      \"PIN1\",\n      \"PRKACA\",\n      \"ATR\",\n      \"MDC1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":7,"faith_total":7,"faith_pct":100.0}}