{"gene":"CDC25C","run_date":"2026-06-09T22:57:18","timeline":{"discoveries":[{"year":1997,"finding":"CDC25C is phosphorylated on serine-216 throughout interphase (but not mitosis), and this phosphorylation mediates binding to 14-3-3 proteins. A S216A mutation abrogated 14-3-3 binding and allowed cells to escape G2 checkpoint arrest induced by unreplicated DNA or radiation. Chk1 phosphorylates CDC25C on serine-216 in vitro, establishing the checkpoint kinase–CDC25C–14-3-3 axis.","method":"In vitro kinase assay (Chk1 phosphorylation of CDC25C), site-directed mutagenesis (S216A), conditional overexpression, checkpoint abrogation assay","journal":"Science","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods (in vitro kinase assay, mutagenesis, functional checkpoint readout), highly replicated across the field","pmids":["9278512"],"is_preprint":false},{"year":1993,"finding":"CDC25C phosphatase activity is directly activated by phosphorylation by the cdc2-cyclin B kinase in mitotic HeLa extracts and in vitro. Phosphorylation of CDC25C is required for activation of cdc2-cyclin B and entry into M-phase, establishing a positive feedback (autocatalytic) loop at the onset of mitosis.","method":"In vitro kinase/phosphatase assay, Xenopus egg extract activation assay, oocyte maturation assay, thiophosphorylation experiments","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with multiple functional readouts, replicated in multiple systems (HeLa extracts, Xenopus eggs, oocytes)","pmids":["8428594"],"is_preprint":false},{"year":1993,"finding":"PP2A (type-2A phosphatase) maintains CDC25C in a dephosphorylated, low-activity state during interphase in Xenopus egg extracts. Inhibition of PP2A by okadaic acid prevents CDC25C dephosphorylation and prematurely activates cdc2-cyclin B, while addition of PP2A catalytic subunit blocks kinase activation. This places PP2A as a negative regulator upstream of CDC25C in a positive feedback loop.","method":"Xenopus egg extract biochemistry, okadaic acid inhibition, PP2A catalytic subunit addition, phosphatase-specific inhibitors (inhibitor-2)","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution in cell-free extracts with multiple pharmacological and biochemical interventions, replicated independently","pmids":["8389619"],"is_preprint":false},{"year":1994,"finding":"cdc2-cyclin B phosphorylates CDC25C on five specific sites in vitro and in vivo at the G2-M transition. Phosphorylation by cdc2-cyclin B increases CDC25C phosphatase activity 2–3-fold. Only phosphorylated CDC25C (not unphosphorylated) effectively induces premature prophase when microinjected into living fibroblasts, demonstrating that multisite phosphorylation by cdc2-cyclin B drives the autoamplification loop.","method":"In vitro kinase assay, tryptic phosphopeptide mapping, peptide sequencing, microinjection into living fibroblasts, phosphatase activity assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution, precise site mapping, and functional in vivo microinjection validation in one study","pmids":["8119945"],"is_preprint":false},{"year":1998,"finding":"C-TAK1 (Cdc25C-associated protein kinase 1) phosphorylates CDC25C on serine-216 in vitro and in vivo. C-TAK1 physically interacts with CDC25C (co-immunoprecipitation in COS-7 cells). Co-production of C-TAK1 and CDC25C in bacteria results in stoichiometric S216 phosphorylation and facilitates 14-3-3 binding in vitro.","method":"In vitro kinase assay, co-immunoprecipitation, bacterial co-expression, 14-3-3 binding assay","journal":"Cell growth & differentiation","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — multiple orthogonal methods (in vitro kinase, Co-IP, bacterial co-expression), single lab but rigorous validation","pmids":["9543386"],"is_preprint":false},{"year":1999,"finding":"CDC25C is retained in the cytoplasm during interphase in human cells. A 58-amino-acid region (aa 201–258) containing the 14-3-3 binding site is required for cytoplasmic localization. Mutations disrupting 14-3-3 binding cause pancellular redistribution and increased ability to induce premature chromosome condensation. Gamma irradiation or leptomycin B did not alter cytoplasmic localization, suggesting 14-3-3 binding (not NES) is the dominant mechanism for cytoplasmic retention during interphase.","method":"Monoclonal antibody immunofluorescence, deletion/point mutagenesis, premature chromosome condensation assay, leptomycin B treatment","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct localization experiments with mutational dissection and functional readout, single lab, multiple orthogonal approaches","pmids":["10330186"],"is_preprint":false},{"year":2000,"finding":"14-3-3 binding regulates intracellular trafficking of CDC25C. CDC25C is actively exported from the nucleus via an intrinsic NES in its amino terminus. A 14-3-3-binding mutant of CDC25C is partially nuclear, and its nuclear accumulation is enhanced by leptomycin B. Loss of both NES function and 14-3-3 binding is required for complete nuclear accumulation. 14-3-3 binding negatively regulates nuclear import rather than promoting nuclear export.","method":"Leptomycin B nuclear export inhibition, NES mutation, 14-3-3-binding mutant, immunofluorescence localization","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal pharmacological and genetic dissection of import vs. export contributions, two orthogonal approaches","pmids":["11313932"],"is_preprint":false},{"year":2000,"finding":"Pin1 catalyzes prolyl isomerization of specific pSer/Thr-Pro motifs in CDC25C, facilitating their dephosphorylation by PP2A, which is conformation-specific and efficiently dephosphorylates only the trans pSer/Thr-Pro isomer. This Pin1-dependent isomerization is essential for cell division in vivo.","method":"In vitro prolyl isomerase assay, PP2A dephosphorylation assay with cis/trans-specific substrates, genetic epistasis in yeast, in vivo cell division assay with Pin1 catalytic mutants","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with conformation-specific assays plus genetic epistasis, single lab but multiple orthogonal methods","pmids":["11090625"],"is_preprint":false},{"year":2002,"finding":"Plk1 phosphorylates CDC25C on Ser198 within its nuclear export signal during prophase, promoting nuclear localization of CDC25C. A constitutively active Plk1 promotes nuclear accumulation; S198A mutant CDC25C remains cytoplasmic when wild-type CDC25C enters the nucleus during prophase.","method":"In vitro kinase assay, immunofluorescence microscopy, constitutively active Plk1 overexpression, S198A point mutation","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct kinase assay combined with functional mutational validation and cell biological localization, single lab, multiple orthogonal methods","pmids":["11897663"],"is_preprint":false},{"year":2000,"finding":"Human PLK directly phosphorylates CDC25C in vitro (using endogenous PLK immunoprecipitated from G2/M-arrested Jurkat cells and recombinant PLK). Phosphorylation of CDC25C by PLK activates its phosphatase activity, as assessed by dephosphorylation of cdc2-cyclin B.","method":"In vitro kinase assay with endogenous and recombinant PLK, phosphatase activity assay","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 1–2 / Weak — in vitro reconstitution with endogenous and recombinant proteins, single lab","pmids":["11202906"],"is_preprint":false},{"year":2001,"finding":"Immunodepletion of Plx1 (Xenopus polo-like kinase) from oocyte extracts completely inhibited activation of Cdc25C and cyclin B-Cdc2 by PKI, demonstrating that Plx1 is necessary for Cdc25C activation during meiotic maturation.","method":"Immunodepletion from Xenopus oocyte extract, cell-free maturation assay with PKI, MAPK pathway inhibition","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — immunodepletion in cell-free extract with biochemical readout of Cdc25C and Cdk activation, rigorous controls","pmids":["11408585"],"is_preprint":false},{"year":2000,"finding":"UCN-01 causes loss of CDC25C serine-216 phosphorylation and 14-3-3 binding in DNA-damaged cells. UCN-01 potently inhibits Chk1-mediated phosphorylation of CDC25C in vitro, identifying Chk1 and the CDC25C pathway as targets of UCN-01-mediated G2 checkpoint abrogation.","method":"In vitro Chk1 kinase assay, immunoprecipitation of CDC25C/14-3-3 complexes from irradiated cells, phosphorylation-site western blot","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro kinase assay plus cell-based biochemical validation, replicated with multiple orthogonal readouts","pmids":["10681541"],"is_preprint":false},{"year":1994,"finding":"A serine kinase that associates with and phosphorylates CDC25C on serine-216 was purified ~8000-fold from rat liver as a 36–38 kDa doublet. The kinase binds within amino acids 200–256 of CDC25C, a region that also contains a putative bipartite nuclear localization signal.","method":"Protein purification (8000-fold), in vitro kinase assay, domain mapping","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — biochemical purification and in vitro kinase assay, single lab, predates molecular identification of the kinase","pmids":["7982962"],"is_preprint":false},{"year":2002,"finding":"Hydrogen peroxide induces an intramolecular disulfide bond between the active-site cysteine (C377) and C330 in CDC25C in vitro, promoting its degradation in vivo. A double C330/C377 mutant that cannot form this disulfide is more stable, resistant to oxidative stress-induced degradation, and shows reduced 14-3-3 binding in vitro and in vivo. Chk1 phosphorylation site mutation did not prevent H2O2-induced degradation, indicating a Chk1-independent mechanism.","method":"In vitro oxidation assay, site-directed mutagenesis (C330A, C377A, double mutant), stability/half-life assay, 14-3-3 binding assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro biochemical demonstration of disulfide bond plus mutational functional validation in cells, single lab, multiple orthogonal methods","pmids":["11925443"],"is_preprint":false},{"year":2004,"finding":"Plk3 phosphorylates CDC25C primarily on S191 (and to a lesser extent S198) in vitro; both sites are within the nuclear exclusion motif. The S191D phosphomimetic mutant accumulates in the nucleus, whereas S191A facilitates nuclear exclusion. Plk3 overexpression promotes CDC25C nuclear accumulation and decreased Cdc2 Y15 phosphorylation; kinase-dead Plk3 fails to do so.","method":"In vitro kinase assay, phosphomimetic/alanine mutagenesis, immunofluorescence localization, Cdc2 Y15 phosphorylation western blot","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro kinase assay with functional mutagenesis and localization readout, single lab","pmids":["14968113"],"is_preprint":false},{"year":2007,"finding":"ERK2/p42 MAPK is a major Cdc25C-phosphorylating kinase in M-phase-arrested Xenopus egg extracts. In Xenopus oocytes, p42 MAPK interacts with hypophosphorylated Cdc25C before meiotic induction and phosphorylates Cdc25C at T48, T138, and S205, increasing its phosphatase activity. In mammalian cells, ERK1/2 interacts with Cdc25C in interphase and phosphorylates Cdc25C at T48 in mitosis; ERK inhibition partially inhibits T48 phosphorylation, Cdc25C activation, and mitotic entry.","method":"Xenopus egg extract biochemistry, co-immunoprecipitation, in vitro kinase assay, site-directed mutagenesis, ERK inhibition in mammalian cells","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple systems (Xenopus extract, oocytes, mammalian cells), Co-IP, in vitro kinase assay, and site mapping, convergent evidence","pmids":["17382881"],"is_preprint":false},{"year":2003,"finding":"JNK/SAPK directly phosphorylates CDC25C on serine-168 in vitro. S168 is phosphorylated in vivo in response to stress (UV, DNA damage). Phospho-S168 CDC25C lacks phosphatase activity; S168A mutant expression reverses JNK-mediated inhibition of cdc2-cyclin B kinase activity.","method":"In vitro kinase assay, phosphospecific antibody detection in vivo, S168A mutagenesis, cdc2-cyclin B activity assay","journal":"Cellular signalling","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro kinase assay, in vivo phosphorylation verified by phosphospecific antibody, functional rescue by mutagenesis; replicated in follow-up study (PMID 20220133)","pmids":["12742231","20220133"],"is_preprint":false},{"year":2003,"finding":"CaMKII phosphorylates Cdc25C on S287 in vitro and delays Cdc2-cyclin B activation via S287 phosphorylation in Xenopus egg extracts. S287-kinase activity is stimulated upon Ca2+ addition (mimicking fertilization) and is dependent on CaMKII; it is not dependent on cyclin B degradation or Cdc2 inactivation.","method":"Xenopus egg extract biochemistry, Ca2+ addition assay, CaMKII-specific inhibitors (KN-93, UCN-01, debromohymenialdisine), in vitro CaMKII kinase assay on Cdc25C","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1 / Moderate — cell-free reconstitution with multiple kinase inhibitors and direct in vitro kinase assay; complements earlier cell-based evidence","pmids":["14517314"],"is_preprint":false},{"year":1999,"finding":"CaM kinase II phosphorylates CDC25C in vitro and increases its phosphatase activity 2.5–3-fold. Inhibition of CaM kinase II in synchronized HeLa cells (KN-93 or microinjected AC3-I peptide) causes G2 block with unphosphorylated CDC25C, phosphorylated Cdc2-Y15, and no histone H1 kinase activation.","method":"In vitro CaM kinase II kinase/phosphatase assay, HeLa cell synchronization, KN-93 pharmacological inhibition, microinjection of peptide inhibitor","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro kinase assay combined with pharmacological and peptide inhibitor cell studies, single lab","pmids":["10075693"],"is_preprint":false},{"year":2002,"finding":"Chk2 monomers and dimers both phosphorylate Cdc25C in vitro. Chk2 from unstressed cells is largely monomeric, inactive, and unphosphorylated at Thr-68. After DNA damage, active Chk2 exists as stable Thr-68-phosphorylated dimers as well as Thr-68-unphosphorylated monomers/dimers, all capable of phosphorylating Cdc25C.","method":"Purification of Chk2 from baculovirus-infected insect cells and human cells ± DNA damage, in vitro kinase assay with Cdc25C substrate, Stokes radius and sedimentation coefficient analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — biochemical purification, in vitro kinase assay, biophysical characterization; single lab but rigorous","pmids":["12386164"],"is_preprint":false},{"year":2004,"finding":"Pim-1 kinase directly binds and phosphorylates the N-terminal region of CDC25C, enhancing its phosphatase activity. Pim-1 also phosphorylates and inhibits C-TAK1 (which normally phosphorylates and inactivates CDC25C), thus indirectly activating CDC25C through two mechanisms. Pim-1 and CDC25C co-localize in the cytoplasm.","method":"Biochemical kinase assay, yeast two-hybrid, immunofluorescence co-localization, mass spectrometry of phosphorylation sites, G2/M progression assay","journal":"The Journal of biological chemistry / The international journal of biochemistry & cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical and cell biological methods from one lab; two independent papers corroborate direct phosphorylation","pmids":["15319445","16356754"],"is_preprint":false},{"year":1999,"finding":"Prk (a polo-related kinase) physically interacts with CDC25C and phosphorylates it at two sites in vitro, with the major site co-migrating with serine-216. Co-immunoprecipitation and affinity chromatography confirmed the interaction. Prk-phosphorylated CDC25C showed enhanced kinase activity.","method":"Baculovirus expression, in vitro kinase assay, co-immunoprecipitation, affinity column chromatography, phosphopeptide mapping","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal biochemical interaction methods and in vitro kinase assay, single lab","pmids":["10557092"],"is_preprint":false},{"year":2000,"finding":"An essential phosphorylation-site domain of CDC25C (aa ~200–256) interacts with both 14-3-3 proteins and cyclins (via the cyclin P-box motif). NMR and circular dichroism reveal two alpha-helical moieties interconnected by a loop carrying the 14-3-3 binding site; helical folding is induced upon 14-3-3 binding, suggesting conformational regulation.","method":"NMR spectroscopy, circular dichroism, in vitro binding assays with purified 14-3-3 and cyclins, domain analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR structure with biochemical binding validation, single lab","pmids":["10864927"],"is_preprint":false},{"year":2002,"finding":"Arsenite induces CDC25C degradation via the ubiquitin-proteasome pathway. Mutation of the KEN box within residues 151–157 of CDC25C, or competition with a KEN-box peptide, partially inhibits arsenite-induced CDC25C ubiquitination. This CDC25C degradation contributes to G2/M arrest.","method":"Ubiquitination assay, proteasome inhibition, KEN-box mutagenesis, KEN-box peptide competition","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis and peptide competition with biochemical readout, single lab","pmids":["11842186"],"is_preprint":false},{"year":2004,"finding":"p53 represses CDC25C transcription via two independent mechanisms: (1) direct binding of p53 to a site in the cdc25C promoter; (2) a CDE/CHR element-dependent mechanism not requiring p53 direct binding. Three CCAAT elements previously implicated do not mediate repression at physiologically relevant p53 levels.","method":"Reporter gene assay with promoter mutations, p53 binding site mutation, gel shift/EMSA, cell-based p53 induction at physiological levels","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic promoter dissection with multiple mutations and functional readouts, independently corroborated by other labs studying CDC25C promoter regulation","pmids":["15574328"],"is_preprint":false},{"year":2002,"finding":"CDC25C interacts with PCNA, as identified by yeast two-hybrid and confirmed by in vitro and in vivo co-immunoprecipitation. CDC25C and PCNA transiently co-immunoprecipitate and co-localize in the nucleus at the beginning of M phase in Jurkat cells.","method":"Yeast two-hybrid, in vitro binding assay, co-immunoprecipitation from Jurkat cells, immunofluorescence co-localization","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — yeast two-hybrid confirmed by co-IP and co-localization, single lab","pmids":["11896603"],"is_preprint":false},{"year":2007,"finding":"PP2A:B56δ dephosphorylates CDC25C both during interphase and at mitosis. Loss of PP2A:B56δ (stable knockdown or mouse KO) results in prolonged CDC25C hyperphosphorylation/activation and persistent Cdk1 activation, causing delayed mitotic exit. This is compensated by transcriptional upregulation of Wee1 kinase.","method":"Stable knockdown, mouse knockout, biochemical analysis of CDC25C and Cdk1 phosphorylation, mitotic timing assay, Wee1 expression analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO in mice corroborated by stable knockdown, biochemical mechanistic readouts, and compensation analysis","pmids":["18056802"],"is_preprint":false},{"year":2003,"finding":"Xp38γ/SAPK3 phosphorylates Xenopus Cdc25C on Ser205 and promotes meiotic G2/M transition. Overexpression of constitutively active MKK6-Xp38γ induces oocyte maturation without progesterone; kinase-dead MKK6 and Xp38γ inhibit progesterone-induced maturation. This requires neither Mos/MAPK nor protein synthesis.","method":"Xenopus oocyte overexpression, constitutively active/dominant-negative mutants, immunoprecipitation kinase assay, site identification","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional gain/loss-of-function in oocytes with kinase assay and site mapping, single lab","pmids":["14592973"],"is_preprint":false},{"year":2001,"finding":"Cdc25C knockout mice are viable, fertile, and display no obvious abnormalities. MEFs lacking Cdc25C show normal cdc2 phosphorylation, normal timing of mitotic entry, and normal DNA damage responses. This demonstrates Cdc25C is dispensable for embryonic and adult cell cycles in mice, suggesting functional redundancy with Cdc25A and/or Cdc25B.","method":"Mouse gene knockout, MEF cell cycle analysis, DNA damage response assay, tissue expression analysis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout in mice with comprehensive phenotypic analysis; confirmed by Cdc25B/C double-KO study (PMID 15767688)","pmids":["11359894","15767688"],"is_preprint":false},{"year":2003,"finding":"CDC25C functional phosphatase activity is required for S-phase entry in human cells. CDC25C protein and activity increase at S-phase onset. Antisense, siRNA, or microinjection of anti-CDC25C antibodies inhibits DNA synthesis; re-introduction of wild-type but not catalytically-dead (C377S) CDC25C restores normal cell cycle progression.","method":"siRNA knockdown, antisense microinjection, immunoprecipitate phosphatase activity assay from synchronized HeLa cells, wild-type vs. C377S rescue","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with multiple approaches plus catalytic mutant rescue, single lab; contrasts with mouse KO data suggesting redundancy","pmids":["12857880"],"is_preprint":false},{"year":2007,"finding":"LZTS1/Fez1 interacts with Cdk1 and Cdc25C during mitosis. In Lzts1−/− MEFs, Cdc25C degradation is increased during M phase, resulting in decreased Cdk1 activity, accelerated mitotic progression, resistance to taxol/nocodazole-induced M-phase arrest, and improper chromosome segregation.","method":"Lzts1 knockout mouse, MEF biochemical analysis, Cdc25C stability assay, Cdk1 activity assay, chromosome segregation analysis","journal":"Cancer cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with biochemical mechanistic readouts, single lab","pmids":["17349584"],"is_preprint":false},{"year":2012,"finding":"Telomere damage (via TRF2 or POT1 depletion) activates ATR/ATM, which phosphorylate CHK1/CHK2, leading to S216 phosphorylation of CDC25C, its nuclear export, and proteasomal degradation. This CDC25C degradation is required to sustain G2/M arrest from dysfunctional telomeres. Additionally, p53 transcriptionally downregulates CDC25C in this context.","method":"TRF2/POT1 siRNA depletion, CHK1/2 inhibition, proteasome inhibition, phospho-S216 CDC25C detection, checkpoint abrogation readout","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockdowns with biochemical mechanistic readouts, single lab, multiple orthogonal interventions","pmids":["22842784"],"is_preprint":false},{"year":2017,"finding":"Mdm2 physically interacts with CDC25C and promotes its proteasomal degradation in a ubiquitin-independent manner, reducing CDC25C half-life. Either Mdm2 overexpression or CDC25C downregulation delays cell cycle progression through G2/M. This is a p53-independent pathway, providing a dual mechanism (p53-mediated transcriptional repression + Mdm2-mediated protein degradation) for p53/Mdm2 to enforce G2/M arrest.","method":"Co-immunoprecipitation, Mdm2 siRNA, half-life assay, proteasome inhibition, cell cycle timing analysis","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal interaction and stability assays with functional readout, single lab","pmids":["28806397"],"is_preprint":false},{"year":2015,"finding":"During interphase, CDC25C phosphatase dephosphorylates phospho-Thr-838 in the activation loop of ASK1, suppressing ASK1-mediated apoptosis. CDC25C knockdown increases ASK1 activity; CDC25C overexpression inhibits ASK1-mediated apoptosis. During mitotic arrest, hyperphosphorylated CDC25C has reduced affinity for ASK1, allowing increased ASK1 activity. This reveals a cell cycle-dependent role for CDC25C in suppressing apoptosis during interphase.","method":"In vitro phosphatase assay (CDC25C on ASK1 pThr-838), siRNA knockdown of CDC25C, co-immunoprecipitation, ASK1 activity assay, apoptosis assay","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro phosphatase assay with physiological substrate plus cell-based knockdown/overexpression, single lab","pmids":["25633196"],"is_preprint":false},{"year":2008,"finding":"A fraction of CDC25C localizes to centrosomes in a cell cycle-dependent manner from late S phase through mitosis. CDC25C co-localizes with Cyclin B1 at centrosomes in G2 and prophase, and both undergo dynamic exchange between centrosome and cytoplasm (FRAP). Centrosomal localization is mediated by the catalytic C-terminal domain but does not require catalytic activity. Phosphatase-dead and substrate-binding mutants of CDC25C accumulate at centrosomes with phospho-Y15-Cdk1 and behave as dominant negatives that impair mitotic entry.","method":"Immunofluorescence, FRAP live-cell imaging, C-terminal domain deletion/mutant analysis, phosphatase-dead and hotspot mutants, dominant-negative assay","journal":"Cell cycle","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct live-cell imaging (FRAP) with mutagenesis and functional readout, single lab","pmids":["18604163"],"is_preprint":false},{"year":2010,"finding":"Cyclin E/CDK2 physically interacts with and phosphorylates CDC25C on Ser214, leading to premature CDC25C activation. Low molecular weight (LMW) cyclin E overexpression causes premature inactivation of CDC25C and PLK1, leading to faster mitotic exit. Downregulation of CDC25C inhibits LMW-E-mediated chromosome missegregation, anaphase bridges, and centrosome amplification.","method":"Co-immunoprecipitation, in vitro kinase assay, CDC25C phosphatase activity assay, siRNA knockdown of CDC25C, chromosome segregation/centrosome analysis","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP confirmed kinase-substrate relationship with functional mutagenesis and knockdown readout, single lab","pmids":["20530684"],"is_preprint":false},{"year":2005,"finding":"HIV-1 Vpr directly binds CDC25C in vitro and in mammalian cells and inhibits CDC25C phosphatase activity in vitro by binding a site distinct from the catalytic site. Expression of a Cdc25C mutant with reduced Vpr binding or siRNA depletion of Cdc25C reduces Vpr-mediated G2 arrest.","method":"In vitro binding assay, co-immunoprecipitation from mammalian cells, in vitro phosphatase inhibition assay, CDC25C mutant with reduced Vpr binding, CDC25C depletion","journal":"Virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro binding and phosphatase assay confirmed in cells with loss-of-function rescue, single lab","pmids":["14972559"],"is_preprint":false},{"year":1992,"finding":"Microinjected antibody to hamster/human CDC25C inhibits chromosome condensation induced by loss of RCC1 function (tsBN2 mutation), demonstrating that CDC25C is required for p34cdc2 kinase activation in this context. CDC25C is located predominantly in the cytoplasm (periphery of nuclei) in interphase cells and moves into the nucleus upon loss of RCC1 function.","method":"Antibody microinjection, tsBN2 cell genetic system, immunofluorescence localization","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — antibody microinjection with genetic system readout and direct localization, single lab","pmids":["1337289"],"is_preprint":false},{"year":2015,"finding":"p53-dependent repression of CDC25C requires activation of p21 (CDKN1A), which causes replacement of the MMB (B-MYB-MuvB) complex by the DREAM complex at CDE/CHR elements in the CDC25C promoter. ChIP shows E2F4 and p130 (DREAM components) replace B-MYB upon p53 activation; mutations in CDE/CHR elements abolish p53-dependent repression. No p53 binding to the CDC25C promoter is detected by ChIP.","method":"Chromatin immunoprecipitation (ChIP), promoter reporter assays with CDE/CHR mutations, p21 knockdown epistasis","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and promoter mutagenesis with epistasis, single lab; refines mechanism of prior studies","pmids":["26595675"],"is_preprint":false},{"year":2023,"finding":"PUF60, a poly(U)-binding splicing factor, controls alternative splicing of CDC25C. PUF60 knockdown causes exon 3 skipping in CDC25C, leading to nonsense-mediated mRNA decay and decreased CDC25C protein, thereby inhibiting G2/M transition and cancer cell proliferation.","method":"Systematic splicing factor analysis in LUAD, siRNA knockdown of PUF60, RNA-seq for splice variant detection, cell cycle analysis","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNA-seq splice variant identification with functional knockdown and cell cycle readout, single lab","pmids":["37682709"],"is_preprint":false}],"current_model":"CDC25C is a dual-specificity phosphatase that activates the Cdk1 (cdc2)/cyclin B complex at the G2/M transition by dephosphorylating Thr14 and Tyr15 on Cdk1; it is regulated by an intricate network of post-translational modifications—including inhibitory phosphorylation at S216 by Chk1, Chk2, C-TAK1, CaMKII, JNK, and ERK, and activating phosphorylation at multiple sites by cdc2-cyclin B (positive feedback loop), Plk1, PLK3, ERK/MAPK, and Pim-1—that control its phosphatase activity and nucleocytoplasmic localization; during interphase, S216 phosphorylation promotes 14-3-3 binding, which sequesters CDC25C in the cytoplasm by blocking nuclear import, while an intrinsic NES mediates its nuclear export; at mitotic entry, Plk1-mediated S198 phosphorylation overcomes nuclear exclusion; Pin1-catalyzed prolyl isomerization facilitates PP2A-mediated dephosphorylation of CDC25C; Mdm2 promotes CDC25C proteasomal degradation in a ubiquitin-independent manner; p53 represses CDC25C transcription through direct promoter binding and via the p21-DREAM-CDE/CHR pathway; and beyond its canonical mitotic role, CDC25C additionally dephosphorylates and suppresses ASK1 during interphase, interacts with PCNA at the G2/M boundary, and localizes dynamically to centrosomes to amplify Cdk1 activation."},"narrative":{"mechanistic_narrative":"CDC25C is a dual-specificity phosphatase that drives the G2/M transition by activating the cdc2(Cdk1)-cyclin B kinase, and its own phosphatase activity is in turn amplified through a positive feedback loop in which active cdc2-cyclin B phosphorylates CDC25C on multiple sites to increase its activity 2-3-fold and trigger premature mitotic entry [PMID:8428594, PMID:8119945]. This autoamplification is held in check during interphase by PP2A, which keeps CDC25C dephosphorylated and inactive; the conformation-specific PP2A:B56δ holoenzyme, acting on trans pSer/Thr-Pro motifs generated by Pin1-catalyzed prolyl isomerization, restrains CDC25C and Cdk1 activity until mitotic exit [PMID:8389619, PMID:11090625, PMID:18056802]. CDC25C activity and localization are governed by an extensive phosphorylation network: inhibitory phosphorylation of Ser216 by Chk1, Chk2, C-TAK1, and CaMKII creates a 14-3-3 binding site that enforces cytoplasmic retention by blocking nuclear import, working together with an intrinsic N-terminal nuclear export signal [PMID:9278512, PMID:9543386, PMID:11313932, PMID:14517314, PMID:12386164, PMID:10864927], while activating phosphorylation by Plk1/PLK on Ser198, by Plk3 on Ser191, and by ERK/MAPK on Thr48 overcomes nuclear exclusion and stimulates phosphatase activity at mitotic entry [PMID:11897663, PMID:11202906, PMID:14968113, PMID:17382881]. This network couples CDC25C to checkpoint and stress signaling: DNA-damage and replication checkpoints converge on Ser216 phosphorylation and 14-3-3 sequestration to enforce G2 arrest [PMID:9278512, PMID:10681541], stress kinases such as JNK inactivate CDC25C, and oxidative stress drives an intramolecular disulfide bond that triggers degradation [PMID:11925443, PMID:12742231, PMID:20220133]. CDC25C levels are further controlled by p53, which represses its transcription both by direct promoter binding and through the p21-dependent DREAM/CDE-CHR pathway, and by Mdm2, which promotes ubiquitin-independent proteasomal degradation, together enforcing G2/M arrest [PMID:15574328, PMID:28806397, PMID:26595675]. Beyond mitotic control, CDC25C dephosphorylates the activation-loop Thr838 of ASK1 to suppress apoptosis during interphase, and a centrosomal pool co-localizes with cyclin B1 to locally amplify Cdk1 activation [PMID:25633196, PMID:18604163]. Genetic ablation in mice shows CDC25C is dispensable for normal cell cycles, indicating functional redundancy with CDC25A/B [PMID:11359894, PMID:15767688].","teleology":[{"year":1992,"claim":"Established that CDC25C is functionally required for cdc2 kinase activation and chromosome condensation, and that it is cytoplasmic in interphase but enters the nucleus upon checkpoint loss.","evidence":"Antibody microinjection in the tsBN2 (RCC1-mutant) genetic system with immunofluorescence localization","pmids":["1337289"],"confidence":"Medium","gaps":["Mechanism of nuclear relocalization not defined","Substrate specificity for Cdk1 sites not yet mapped"]},{"year":1993,"claim":"Defined the core mitotic feedback loop: cdc2-cyclin B phosphorylation directly activates CDC25C, while PP2A keeps it inactive during interphase, framing the switch-like onset of mitosis.","evidence":"Xenopus egg extract and HeLa extract biochemistry with okadaic acid, PP2A catalytic subunit addition, and oocyte maturation assays","pmids":["8428594","8389619"],"confidence":"High","gaps":["Specific activating phosphosites not yet mapped","Identity of the PP2A holoenzyme not defined"]},{"year":1994,"claim":"Mapped the cdc2-cyclin B activating phosphorylation to five sites and showed phosphorylation is functionally sufficient to drive premature prophase, defining the autoamplification mechanism.","evidence":"In vitro kinase assay, tryptic phosphopeptide mapping, peptide sequencing, microinjection into fibroblasts","pmids":["8119945"],"confidence":"High","gaps":["Did not address how the loop is initially triggered","Spatial regulation not addressed"]},{"year":1994,"claim":"Biochemically purified an unidentified Ser216 kinase binding within aa 200-256, anticipating the regulatory checkpoint axis before its molecular identity was known.","evidence":"8000-fold protein purification from rat liver with in vitro kinase assay and domain mapping","pmids":["7982962"],"confidence":"Medium","gaps":["Kinase identity not molecularly defined at the time","Functional consequence of S216 phosphorylation not yet established"]},{"year":1997,"claim":"Connected the DNA-damage/replication checkpoint to CDC25C by showing Chk1 phosphorylates Ser216 to create a 14-3-3 site whose loss abrogates G2 arrest, establishing the checkpoint-CDC25C-14-3-3 axis.","evidence":"In vitro Chk1 kinase assay, S216A mutagenesis, and checkpoint abrogation assays","pmids":["9278512"],"confidence":"High","gaps":["How 14-3-3 binding alters localization not yet resolved","Other Ser216 kinases not addressed"]},{"year":1998,"claim":"Identified C-TAK1 as a constitutive Ser216 kinase that directly binds CDC25C and promotes 14-3-3 binding, broadening the set of kinases enforcing cytoplasmic sequestration.","evidence":"In vitro kinase assay, Co-IP in COS-7 cells, bacterial co-expression, 14-3-3 binding assay","pmids":["9543386"],"confidence":"High","gaps":["Physiological context distinguishing C-TAK1 from Chk1 not defined"]},{"year":1999,"claim":"Demonstrated that the 14-3-3-binding region (aa 201-258) mediates cytoplasmic retention and that disrupting 14-3-3 binding enables premature chromosome condensation, identifying 14-3-3 as the dominant interphase retention mechanism.","evidence":"Immunofluorescence with deletion/point mutagenesis, premature chromosome condensation assay, leptomycin B treatment","pmids":["10330186"],"confidence":"High","gaps":["Relative contribution of NES not yet quantified","Mechanism by which 14-3-3 blocks import unresolved"]},{"year":1999,"claim":"Showed CaMKII phosphorylates and activates CDC25C and is required for G2/M progression, linking calcium signaling to mitotic entry.","evidence":"In vitro CaMKII kinase/phosphatase assay, HeLa synchronization, KN-93 and peptide inhibitor microinjection","pmids":["10075693"],"confidence":"Medium","gaps":["Phosphosite not mapped in this study","Single lab"]},{"year":2000,"claim":"Resolved the import/export logic of CDC25C trafficking, showing an intrinsic N-terminal NES drives export while 14-3-3 binding negatively regulates nuclear import.","evidence":"Leptomycin B export inhibition, NES and 14-3-3-binding mutants, immunofluorescence","pmids":["11313932"],"confidence":"High","gaps":["Import receptor not identified","How mitotic kinases override NES not yet addressed"]},{"year":2000,"claim":"Provided a structural basis for conformational regulation, showing the regulatory domain binds both 14-3-3 and cyclins and folds into helices upon 14-3-3 binding.","evidence":"NMR spectroscopy, circular dichroism, in vitro binding with purified 14-3-3 and cyclins","pmids":["10864927"],"confidence":"High","gaps":["Full-length structure not solved","Functional consequence of cyclin P-box binding not defined"]},{"year":2000,"claim":"Introduced Pin1 prolyl isomerization as a conformational checkpoint that renders CDC25C competent for PP2A-mediated dephosphorylation, coupling proline-directed phosphorylation to phosphatase access.","evidence":"In vitro prolyl isomerase and conformation-specific PP2A assays, yeast genetic epistasis, in vivo cell division with Pin1 catalytic mutants","pmids":["11090625"],"confidence":"High","gaps":["Specific isomerized motifs in CDC25C not fully enumerated"]},{"year":2000,"claim":"Linked the G2 checkpoint to therapy by showing UCN-01 inhibits Chk1-mediated Ser216 phosphorylation and abrogates 14-3-3 binding, validating the axis as a drug target.","evidence":"In vitro Chk1 kinase assay and IP of CDC25C/14-3-3 complexes from irradiated cells","pmids":["10681541"],"confidence":"High","gaps":["Off-target kinase effects of UCN-01 not fully excluded"]},{"year":2000,"claim":"Established polo-like kinase as a direct activating kinase of CDC25C, increasing phosphatase activity toward cdc2-cyclin B.","evidence":"In vitro kinase assay with endogenous and recombinant PLK, phosphatase activity assay","pmids":["11202906"],"confidence":"Medium","gaps":["Activating phosphosite not mapped here","In vivo requirement not established"]},{"year":2001,"claim":"Demonstrated in a cell-free meiotic system that polo-like kinase (Plx1) is necessary for Cdc25C and Cdc2 activation, establishing PLK as an upstream requirement.","evidence":"Immunodepletion of Plx1 from Xenopus oocyte extract with maturation assay","pmids":["11408585"],"confidence":"High","gaps":["Direct vs. indirect requirement not separated","Mammalian generality from oocyte system"]},{"year":2001,"claim":"Showed via knockout that Cdc25C is dispensable for mouse development and cell cycles, revealing functional redundancy among CDC25 family members.","evidence":"Cdc25C knockout mouse with MEF cell cycle and DNA damage response analysis (confirmed by Cdc25B/C double-KO)","pmids":["11359894","15767688"],"confidence":"High","gaps":["Degree of compensation by CDC25A/B not quantified","Cell-context-specific non-redundant roles not excluded"]},{"year":2002,"claim":"Refined the spatial activation step by showing Plk1 phosphorylates Ser198 within the NES to promote nuclear localization at prophase.","evidence":"In vitro kinase assay, S198A mutant, constitutively active Plk1, immunofluorescence","pmids":["11897663"],"confidence":"High","gaps":["Interplay with 14-3-3 release not fully resolved"]},{"year":2002,"claim":"Established Chk2, in both monomeric and dimeric forms, as a DNA-damage-responsive CDC25C kinase, expanding the checkpoint kinase repertoire converging on CDC25C.","evidence":"Purification of Chk2 ± DNA damage, in vitro kinase assay on Cdc25C, biophysical sizing","pmids":["12386164"],"confidence":"High","gaps":["In vivo site preference vs. Chk1 not distinguished"]},{"year":2002,"claim":"Identified arsenite-induced, KEN-box-dependent ubiquitin-proteasome degradation of CDC25C as a route to G2/M arrest, introducing proteolytic control of CDC25C abundance.","evidence":"Ubiquitination assay, proteasome inhibition, KEN-box mutagenesis and peptide competition","pmids":["11842186"],"confidence":"Medium","gaps":["Responsible E3 ligase not identified","Physiological trigger beyond arsenite not defined"]},{"year":2002,"claim":"Discovered a physical CDC25C-PCNA interaction at the G2/M boundary, hinting at coupling to replication/repair machinery.","evidence":"Yeast two-hybrid, in vitro binding, Co-IP and co-localization in Jurkat cells","pmids":["11896603"],"confidence":"Medium","gaps":["Functional consequence of the interaction not established","Single lab"]},{"year":2002,"claim":"Revealed redox control of CDC25C: H2O2 induces an active-site disulfide (C330-C377) that promotes degradation independently of Chk1, linking oxidative stress to CDC25C turnover.","evidence":"In vitro oxidation assay, C330/C377 mutants, stability and 14-3-3 binding assays","pmids":["11925443"],"confidence":"High","gaps":["In vivo physiological oxidant source not defined","Link to ubiquitin machinery not resolved"]},{"year":2003,"claim":"Showed catalytically active CDC25C is required for human S-phase entry, extending its role beyond mitosis (in apparent contrast to mouse redundancy data).","evidence":"siRNA, antisense and antibody microinjection in HeLa, with wild-type vs. C377S rescue","pmids":["12857880"],"confidence":"Medium","gaps":["Discrepancy with mouse KO redundancy unresolved","Relevant S-phase substrate not identified"]},{"year":2003,"claim":"Identified JNK/SAPK as a stress kinase that inactivates CDC25C via Ser168 phosphorylation, coupling stress signaling to mitotic inhibition.","evidence":"In vitro kinase assay, phospho-S168 detection, S168A rescue of cdc2-cyclin B activity (replicated)","pmids":["12742231","20220133"],"confidence":"High","gaps":["Structural basis for S168-mediated inactivation unknown"]},{"year":2003,"claim":"Defined CaMKII Ser287 (Xenopus) phosphorylation as a calcium-triggered inhibitory event delaying Cdc2-cyclin B activation, mechanistically linking fertilization signals to cell cycle timing.","evidence":"Xenopus egg extract biochemistry, Ca2+ addition, CaMKII inhibitors, in vitro kinase assay","pmids":["14517314"],"confidence":"High","gaps":["Mammalian equivalent site context not fully mapped"]},{"year":2003,"claim":"Showed Xp38γ/SAPK3 phosphorylates Cdc25C Ser205 to promote the meiotic G2/M transition independently of Mos/MAPK, adding a stress-kinase route to activation.","evidence":"Xenopus oocyte overexpression with CA/DN mutants, IP kinase assay, site identification","pmids":["14592973"],"confidence":"Medium","gaps":["Mammalian relevance not established","Single lab"]},{"year":2004,"claim":"Established p53 as a transcriptional repressor of CDC25C through both direct promoter binding and a CDE/CHR-dependent route, placing CDC25C downstream of tumor suppressor signaling.","evidence":"Reporter assays with promoter mutations, EMSA, physiological p53 induction","pmids":["15574328"],"confidence":"High","gaps":["Relative contribution of the two mechanisms not quantified at the time"]},{"year":2004,"claim":"Identified Plk3 as a kinase phosphorylating Ser191/Ser198 in the nuclear-exclusion motif, with phosphomimetics driving nuclear accumulation and reduced Cdc2-Y15.","evidence":"In vitro kinase assay, phosphomimetic/alanine mutagenesis, localization, Cdc2-Y15 western","pmids":["14968113"],"confidence":"Medium","gaps":["Distinct roles of Plk1 vs. Plk3 on overlapping sites not reconciled"]},{"year":2004,"claim":"Showed Pim-1 activates CDC25C both directly by N-terminal phosphorylation and indirectly by inhibiting C-TAK1, adding an oncogenic kinase input to the activation network.","evidence":"Kinase assay, yeast two-hybrid, co-localization, MS site mapping, G2/M assay (two papers)","pmids":["15319445","16356754"],"confidence":"Medium","gaps":["In vivo significance of dual mechanism not quantified"]},{"year":2005,"claim":"Demonstrated that HIV-1 Vpr binds CDC25C at a non-catalytic site to inhibit its phosphatase activity and drive viral G2 arrest, identifying CDC25C as a host target of viral cell cycle manipulation.","evidence":"In vitro binding and phosphatase inhibition, Co-IP, binding-deficient mutant and CDC25C depletion","pmids":["14972559"],"confidence":"Medium","gaps":["Structural basis of inhibitory binding not solved"]},{"year":2007,"claim":"Established ERK/p42 MAPK as a major activating CDC25C kinase across systems, phosphorylating Thr48 (and T138/S205) to boost phosphatase activity and promote mitotic entry.","evidence":"Xenopus extract/oocyte biochemistry, Co-IP, in vitro kinase assay, site mapping, ERK inhibition in mammalian cells","pmids":["17382881"],"confidence":"High","gaps":["Quantitative contribution relative to PLK feedback not defined"]},{"year":2007,"claim":"Identified PP2A:B56δ as the specific holoenzyme dephosphorylating CDC25C at interphase and mitosis, with its loss causing persistent Cdk1 activity and delayed mitotic exit, defining the molecular counterweight to the activation loop.","evidence":"Stable knockdown and mouse KO, biochemical phosphorylation analysis, mitotic timing, Wee1 compensation","pmids":["18056802"],"confidence":"High","gaps":["Targeting mechanism of B56δ to CDC25C not defined"]},{"year":2007,"claim":"Showed LZTS1/Fez1 stabilizes Cdc25C during mitosis to sustain Cdk1 activity and proper chromosome segregation, identifying a scaffold protecting CDC25C from M-phase degradation.","evidence":"Lzts1 knockout mouse, MEF biochemistry, Cdc25C stability and Cdk1 activity assays, segregation analysis","pmids":["17349584"],"confidence":"Medium","gaps":["Mechanism by which LZTS1 prevents degradation not defined"]},{"year":2008,"claim":"Revealed a centrosomal pool of CDC25C that co-localizes with cyclin B1 to locally amplify Cdk1 activation; phosphatase-dead mutants act as dominant negatives impairing mitotic entry.","evidence":"Immunofluorescence, FRAP, C-terminal domain mutants, dominant-negative assay","pmids":["18604163"],"confidence":"Medium","gaps":["Centrosomal docking partner not identified","Single lab"]},{"year":2010,"claim":"Showed cyclin E/CDK2 phosphorylates CDC25C on Ser214 to cause premature activation, with LMW cyclin E driving CDC25C-dependent chromosomal instability, linking CDC25C to oncogenic cell cycle deregulation.","evidence":"Co-IP, in vitro kinase assay, phosphatase activity assay, CDC25C siRNA, segregation/centrosome analysis","pmids":["20530684"],"confidence":"Medium","gaps":["Physiological role of S214 in normal cycle not defined"]},{"year":2012,"claim":"Integrated telomere dysfunction into the CDC25C axis, showing ATR/ATM-CHK1/2 signaling drives S216 phosphorylation, nuclear export, and degradation of CDC25C to sustain G2/M arrest, with p53 transcriptional input.","evidence":"TRF2/POT1 depletion, CHK1/2 and proteasome inhibition, phospho-S216 detection, checkpoint readout","pmids":["22842784"],"confidence":"Medium","gaps":["E3 ligase for CDC25C degradation in this context not identified"]},{"year":2015,"claim":"Uncovered a non-mitotic role: CDC25C dephosphorylates ASK1 activation-loop Thr838 to suppress apoptosis during interphase, with hyperphosphorylated mitotic CDC25C releasing this inhibition.","evidence":"In vitro phosphatase assay on ASK1 pThr838, CDC25C siRNA/overexpression, Co-IP, ASK1 activity and apoptosis assays","pmids":["25633196"],"confidence":"Medium","gaps":["In vivo significance of CDC25C-ASK1 axis not established"]},{"year":2015,"claim":"Refined p53-mediated repression to a p21-dependent DREAM-complex mechanism, showing DREAM replaces MMB at CDE/CHR elements with no detectable p53 promoter binding.","evidence":"ChIP, promoter reporter with CDE/CHR mutations, p21 knockdown epistasis","pmids":["26595675"],"confidence":"Medium","gaps":["Reconciliation with earlier direct-p53-binding model not fully resolved"]},{"year":2017,"claim":"Identified Mdm2 as a p53-independent route to CDC25C downregulation, promoting ubiquitin-independent proteasomal degradation, completing a dual p53/Mdm2 mechanism for G2/M arrest.","evidence":"Co-IP, Mdm2 siRNA, half-life assay, proteasome inhibition, cell cycle timing","pmids":["28806397"],"confidence":"Medium","gaps":["Structural basis of ubiquitin-independent degradation unknown"]},{"year":2023,"claim":"Added a post-transcriptional layer, showing the splicing factor PUF60 controls CDC25C exon 3 inclusion, with its loss triggering NMD and reduced CDC25C to impair G2/M and proliferation.","evidence":"Splicing factor screen in LUAD, PUF60 siRNA, RNA-seq splice variant detection, cell cycle analysis","pmids":["37682709"],"confidence":"Medium","gaps":["Regulation of PUF60 activity toward CDC25C not defined","Generality beyond LUAD not established"]},{"year":null,"claim":"It remains unresolved how the dense, sometimes overlapping phosphorylation inputs (multiple activating and inhibitory kinases on shared sites) are temporally integrated to produce the switch-like CDC25C activation, and which E3 ligases mediate its various degradation routes.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified quantitative model of competing phosphorylation inputs","E3 ligases for checkpoint, arsenite, and Mdm2-associated degradation not all identified","Discrepancy between human S-phase requirement and mouse dispensability unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1,3,29,33,34]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[1,29,33]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,33]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[5,6,20,37]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[6,8,14,25,37]},{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[34]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[1,3,26,29]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[0,11,31]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[33]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[24,38]}],"complexes":[],"partners":["CDK1","CCNB1","YWHAB","CHEK1","CHEK2","PLK1","PCNA","MDM2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P30307","full_name":"M-phase inducer phosphatase 3","aliases":["Dual specificity phosphatase Cdc25C"],"length_aa":473,"mass_kda":53.4,"function":"Functions as a dosage-dependent inducer in mitotic control. Tyrosine protein phosphatase required for progression of the cell cycle (PubMed:8119945). When phosphorylated, highly effective in activating G2 cells into prophase (PubMed:8119945). Directly dephosphorylates CDK1 and activates its kinase activity (PubMed:8119945)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/P30307/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CDC25C","classification":"Not Classified","n_dependent_lines":4,"n_total_lines":1208,"dependency_fraction":0.0033112582781456954},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"ANKRD39","stoichiometry":0.2},{"gene":"MIF","stoichiometry":0.2},{"gene":"RER1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/CDC25C","total_profiled":1310},"omim":[{"mim_id":"614184","title":"DIS3-LIKE 3-PRIME-5-PRIME EXORIBONUCLEASE 2; DIS3L2","url":"https://www.omim.org/entry/614184"},{"mim_id":"609357","title":"MINICHROMOSOME MAINTENANCE COMPLEX COMPONENT 10; MCM10","url":"https://www.omim.org/entry/609357"},{"mim_id":"609236","title":"BR SERINE/THREONINE KINASE 2; BRSK2","url":"https://www.omim.org/entry/609236"},{"mim_id":"609185","title":"ZINC FINGER AND HOMEODOMAIN PROTEIN 2; ZHX2","url":"https://www.omim.org/entry/609185"},{"mim_id":"604373","title":"CHECKPOINT KINASE 2; CHEK2","url":"https://www.omim.org/entry/604373"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nuclear speckles","reliability":"Supported"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"bone marrow","ntpm":5.4},{"tissue":"lymphoid tissue","ntpm":8.3},{"tissue":"testis","ntpm":16.9}],"url":"https://www.proteinatlas.org/search/CDC25C"},"hgnc":{"alias_symbol":["PPP1R60"],"prev_symbol":["CDC25"]},"alphafold":{"accession":"P30307","domains":[{"cath_id":"3.40.250.10","chopping":"281-436","consensus_level":"high","plddt":96.7739,"start":281,"end":436}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P30307","model_url":"https://alphafold.ebi.ac.uk/files/AF-P30307-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P30307-F1-predicted_aligned_error_v6.png","plddt_mean":63.66},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CDC25C","jax_strain_url":"https://www.jax.org/strain/search?query=CDC25C"},"sequence":{"accession":"P30307","fasta_url":"https://rest.uniprot.org/uniprotkb/P30307.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P30307/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P30307"}},"corpus_meta":[{"pmid":"9278512","id":"PMC_9278512","title":"Mitotic 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cell cycle arrest.","date":"2018","source":"Toxicology and applied pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/30009775","citation_count":30,"is_preprint":false},{"pmid":"20530684","id":"PMC_20530684","title":"Cyclin E deregulation impairs mitotic progression through premature activation of Cdc25C.","date":"2010","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/20530684","citation_count":30,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":49500,"output_tokens":10527,"usd":0.153202,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":21143,"output_tokens":9526,"usd":0.171932,"stage2_stop_reason":"end_turn"},"total_usd":0.325134,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1997,\n      \"finding\": \"CDC25C is phosphorylated on serine-216 throughout interphase (but not mitosis), and this phosphorylation mediates binding to 14-3-3 proteins. A S216A mutation abrogated 14-3-3 binding and allowed cells to escape G2 checkpoint arrest induced by unreplicated DNA or radiation. Chk1 phosphorylates CDC25C on serine-216 in vitro, establishing the checkpoint kinase–CDC25C–14-3-3 axis.\",\n      \"method\": \"In vitro kinase assay (Chk1 phosphorylation of CDC25C), site-directed mutagenesis (S216A), conditional overexpression, checkpoint abrogation assay\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods (in vitro kinase assay, mutagenesis, functional checkpoint readout), highly replicated across the field\",\n      \"pmids\": [\"9278512\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"CDC25C phosphatase activity is directly activated by phosphorylation by the cdc2-cyclin B kinase in mitotic HeLa extracts and in vitro. Phosphorylation of CDC25C is required for activation of cdc2-cyclin B and entry into M-phase, establishing a positive feedback (autocatalytic) loop at the onset of mitosis.\",\n      \"method\": \"In vitro kinase/phosphatase assay, Xenopus egg extract activation assay, oocyte maturation assay, thiophosphorylation experiments\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with multiple functional readouts, replicated in multiple systems (HeLa extracts, Xenopus eggs, oocytes)\",\n      \"pmids\": [\"8428594\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"PP2A (type-2A phosphatase) maintains CDC25C in a dephosphorylated, low-activity state during interphase in Xenopus egg extracts. Inhibition of PP2A by okadaic acid prevents CDC25C dephosphorylation and prematurely activates cdc2-cyclin B, while addition of PP2A catalytic subunit blocks kinase activation. This places PP2A as a negative regulator upstream of CDC25C in a positive feedback loop.\",\n      \"method\": \"Xenopus egg extract biochemistry, okadaic acid inhibition, PP2A catalytic subunit addition, phosphatase-specific inhibitors (inhibitor-2)\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution in cell-free extracts with multiple pharmacological and biochemical interventions, replicated independently\",\n      \"pmids\": [\"8389619\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"cdc2-cyclin B phosphorylates CDC25C on five specific sites in vitro and in vivo at the G2-M transition. Phosphorylation by cdc2-cyclin B increases CDC25C phosphatase activity 2–3-fold. Only phosphorylated CDC25C (not unphosphorylated) effectively induces premature prophase when microinjected into living fibroblasts, demonstrating that multisite phosphorylation by cdc2-cyclin B drives the autoamplification loop.\",\n      \"method\": \"In vitro kinase assay, tryptic phosphopeptide mapping, peptide sequencing, microinjection into living fibroblasts, phosphatase activity assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution, precise site mapping, and functional in vivo microinjection validation in one study\",\n      \"pmids\": [\"8119945\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"C-TAK1 (Cdc25C-associated protein kinase 1) phosphorylates CDC25C on serine-216 in vitro and in vivo. C-TAK1 physically interacts with CDC25C (co-immunoprecipitation in COS-7 cells). Co-production of C-TAK1 and CDC25C in bacteria results in stoichiometric S216 phosphorylation and facilitates 14-3-3 binding in vitro.\",\n      \"method\": \"In vitro kinase assay, co-immunoprecipitation, bacterial co-expression, 14-3-3 binding assay\",\n      \"journal\": \"Cell growth & differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — multiple orthogonal methods (in vitro kinase, Co-IP, bacterial co-expression), single lab but rigorous validation\",\n      \"pmids\": [\"9543386\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"CDC25C is retained in the cytoplasm during interphase in human cells. A 58-amino-acid region (aa 201–258) containing the 14-3-3 binding site is required for cytoplasmic localization. Mutations disrupting 14-3-3 binding cause pancellular redistribution and increased ability to induce premature chromosome condensation. Gamma irradiation or leptomycin B did not alter cytoplasmic localization, suggesting 14-3-3 binding (not NES) is the dominant mechanism for cytoplasmic retention during interphase.\",\n      \"method\": \"Monoclonal antibody immunofluorescence, deletion/point mutagenesis, premature chromosome condensation assay, leptomycin B treatment\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiments with mutational dissection and functional readout, single lab, multiple orthogonal approaches\",\n      \"pmids\": [\"10330186\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"14-3-3 binding regulates intracellular trafficking of CDC25C. CDC25C is actively exported from the nucleus via an intrinsic NES in its amino terminus. A 14-3-3-binding mutant of CDC25C is partially nuclear, and its nuclear accumulation is enhanced by leptomycin B. Loss of both NES function and 14-3-3 binding is required for complete nuclear accumulation. 14-3-3 binding negatively regulates nuclear import rather than promoting nuclear export.\",\n      \"method\": \"Leptomycin B nuclear export inhibition, NES mutation, 14-3-3-binding mutant, immunofluorescence localization\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal pharmacological and genetic dissection of import vs. export contributions, two orthogonal approaches\",\n      \"pmids\": [\"11313932\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Pin1 catalyzes prolyl isomerization of specific pSer/Thr-Pro motifs in CDC25C, facilitating their dephosphorylation by PP2A, which is conformation-specific and efficiently dephosphorylates only the trans pSer/Thr-Pro isomer. This Pin1-dependent isomerization is essential for cell division in vivo.\",\n      \"method\": \"In vitro prolyl isomerase assay, PP2A dephosphorylation assay with cis/trans-specific substrates, genetic epistasis in yeast, in vivo cell division assay with Pin1 catalytic mutants\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with conformation-specific assays plus genetic epistasis, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"11090625\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Plk1 phosphorylates CDC25C on Ser198 within its nuclear export signal during prophase, promoting nuclear localization of CDC25C. A constitutively active Plk1 promotes nuclear accumulation; S198A mutant CDC25C remains cytoplasmic when wild-type CDC25C enters the nucleus during prophase.\",\n      \"method\": \"In vitro kinase assay, immunofluorescence microscopy, constitutively active Plk1 overexpression, S198A point mutation\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct kinase assay combined with functional mutational validation and cell biological localization, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"11897663\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Human PLK directly phosphorylates CDC25C in vitro (using endogenous PLK immunoprecipitated from G2/M-arrested Jurkat cells and recombinant PLK). Phosphorylation of CDC25C by PLK activates its phosphatase activity, as assessed by dephosphorylation of cdc2-cyclin B.\",\n      \"method\": \"In vitro kinase assay with endogenous and recombinant PLK, phosphatase activity assay\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Weak — in vitro reconstitution with endogenous and recombinant proteins, single lab\",\n      \"pmids\": [\"11202906\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Immunodepletion of Plx1 (Xenopus polo-like kinase) from oocyte extracts completely inhibited activation of Cdc25C and cyclin B-Cdc2 by PKI, demonstrating that Plx1 is necessary for Cdc25C activation during meiotic maturation.\",\n      \"method\": \"Immunodepletion from Xenopus oocyte extract, cell-free maturation assay with PKI, MAPK pathway inhibition\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — immunodepletion in cell-free extract with biochemical readout of Cdc25C and Cdk activation, rigorous controls\",\n      \"pmids\": [\"11408585\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"UCN-01 causes loss of CDC25C serine-216 phosphorylation and 14-3-3 binding in DNA-damaged cells. UCN-01 potently inhibits Chk1-mediated phosphorylation of CDC25C in vitro, identifying Chk1 and the CDC25C pathway as targets of UCN-01-mediated G2 checkpoint abrogation.\",\n      \"method\": \"In vitro Chk1 kinase assay, immunoprecipitation of CDC25C/14-3-3 complexes from irradiated cells, phosphorylation-site western blot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro kinase assay plus cell-based biochemical validation, replicated with multiple orthogonal readouts\",\n      \"pmids\": [\"10681541\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"A serine kinase that associates with and phosphorylates CDC25C on serine-216 was purified ~8000-fold from rat liver as a 36–38 kDa doublet. The kinase binds within amino acids 200–256 of CDC25C, a region that also contains a putative bipartite nuclear localization signal.\",\n      \"method\": \"Protein purification (8000-fold), in vitro kinase assay, domain mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — biochemical purification and in vitro kinase assay, single lab, predates molecular identification of the kinase\",\n      \"pmids\": [\"7982962\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Hydrogen peroxide induces an intramolecular disulfide bond between the active-site cysteine (C377) and C330 in CDC25C in vitro, promoting its degradation in vivo. A double C330/C377 mutant that cannot form this disulfide is more stable, resistant to oxidative stress-induced degradation, and shows reduced 14-3-3 binding in vitro and in vivo. Chk1 phosphorylation site mutation did not prevent H2O2-induced degradation, indicating a Chk1-independent mechanism.\",\n      \"method\": \"In vitro oxidation assay, site-directed mutagenesis (C330A, C377A, double mutant), stability/half-life assay, 14-3-3 binding assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro biochemical demonstration of disulfide bond plus mutational functional validation in cells, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"11925443\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Plk3 phosphorylates CDC25C primarily on S191 (and to a lesser extent S198) in vitro; both sites are within the nuclear exclusion motif. The S191D phosphomimetic mutant accumulates in the nucleus, whereas S191A facilitates nuclear exclusion. Plk3 overexpression promotes CDC25C nuclear accumulation and decreased Cdc2 Y15 phosphorylation; kinase-dead Plk3 fails to do so.\",\n      \"method\": \"In vitro kinase assay, phosphomimetic/alanine mutagenesis, immunofluorescence localization, Cdc2 Y15 phosphorylation western blot\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro kinase assay with functional mutagenesis and localization readout, single lab\",\n      \"pmids\": [\"14968113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"ERK2/p42 MAPK is a major Cdc25C-phosphorylating kinase in M-phase-arrested Xenopus egg extracts. In Xenopus oocytes, p42 MAPK interacts with hypophosphorylated Cdc25C before meiotic induction and phosphorylates Cdc25C at T48, T138, and S205, increasing its phosphatase activity. In mammalian cells, ERK1/2 interacts with Cdc25C in interphase and phosphorylates Cdc25C at T48 in mitosis; ERK inhibition partially inhibits T48 phosphorylation, Cdc25C activation, and mitotic entry.\",\n      \"method\": \"Xenopus egg extract biochemistry, co-immunoprecipitation, in vitro kinase assay, site-directed mutagenesis, ERK inhibition in mammalian cells\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple systems (Xenopus extract, oocytes, mammalian cells), Co-IP, in vitro kinase assay, and site mapping, convergent evidence\",\n      \"pmids\": [\"17382881\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"JNK/SAPK directly phosphorylates CDC25C on serine-168 in vitro. S168 is phosphorylated in vivo in response to stress (UV, DNA damage). Phospho-S168 CDC25C lacks phosphatase activity; S168A mutant expression reverses JNK-mediated inhibition of cdc2-cyclin B kinase activity.\",\n      \"method\": \"In vitro kinase assay, phosphospecific antibody detection in vivo, S168A mutagenesis, cdc2-cyclin B activity assay\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro kinase assay, in vivo phosphorylation verified by phosphospecific antibody, functional rescue by mutagenesis; replicated in follow-up study (PMID 20220133)\",\n      \"pmids\": [\"12742231\", \"20220133\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"CaMKII phosphorylates Cdc25C on S287 in vitro and delays Cdc2-cyclin B activation via S287 phosphorylation in Xenopus egg extracts. S287-kinase activity is stimulated upon Ca2+ addition (mimicking fertilization) and is dependent on CaMKII; it is not dependent on cyclin B degradation or Cdc2 inactivation.\",\n      \"method\": \"Xenopus egg extract biochemistry, Ca2+ addition assay, CaMKII-specific inhibitors (KN-93, UCN-01, debromohymenialdisine), in vitro CaMKII kinase assay on Cdc25C\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cell-free reconstitution with multiple kinase inhibitors and direct in vitro kinase assay; complements earlier cell-based evidence\",\n      \"pmids\": [\"14517314\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"CaM kinase II phosphorylates CDC25C in vitro and increases its phosphatase activity 2.5–3-fold. Inhibition of CaM kinase II in synchronized HeLa cells (KN-93 or microinjected AC3-I peptide) causes G2 block with unphosphorylated CDC25C, phosphorylated Cdc2-Y15, and no histone H1 kinase activation.\",\n      \"method\": \"In vitro CaM kinase II kinase/phosphatase assay, HeLa cell synchronization, KN-93 pharmacological inhibition, microinjection of peptide inhibitor\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro kinase assay combined with pharmacological and peptide inhibitor cell studies, single lab\",\n      \"pmids\": [\"10075693\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Chk2 monomers and dimers both phosphorylate Cdc25C in vitro. Chk2 from unstressed cells is largely monomeric, inactive, and unphosphorylated at Thr-68. After DNA damage, active Chk2 exists as stable Thr-68-phosphorylated dimers as well as Thr-68-unphosphorylated monomers/dimers, all capable of phosphorylating Cdc25C.\",\n      \"method\": \"Purification of Chk2 from baculovirus-infected insect cells and human cells ± DNA damage, in vitro kinase assay with Cdc25C substrate, Stokes radius and sedimentation coefficient analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — biochemical purification, in vitro kinase assay, biophysical characterization; single lab but rigorous\",\n      \"pmids\": [\"12386164\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Pim-1 kinase directly binds and phosphorylates the N-terminal region of CDC25C, enhancing its phosphatase activity. Pim-1 also phosphorylates and inhibits C-TAK1 (which normally phosphorylates and inactivates CDC25C), thus indirectly activating CDC25C through two mechanisms. Pim-1 and CDC25C co-localize in the cytoplasm.\",\n      \"method\": \"Biochemical kinase assay, yeast two-hybrid, immunofluorescence co-localization, mass spectrometry of phosphorylation sites, G2/M progression assay\",\n      \"journal\": \"The Journal of biological chemistry / The international journal of biochemistry & cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical and cell biological methods from one lab; two independent papers corroborate direct phosphorylation\",\n      \"pmids\": [\"15319445\", \"16356754\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Prk (a polo-related kinase) physically interacts with CDC25C and phosphorylates it at two sites in vitro, with the major site co-migrating with serine-216. Co-immunoprecipitation and affinity chromatography confirmed the interaction. Prk-phosphorylated CDC25C showed enhanced kinase activity.\",\n      \"method\": \"Baculovirus expression, in vitro kinase assay, co-immunoprecipitation, affinity column chromatography, phosphopeptide mapping\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal biochemical interaction methods and in vitro kinase assay, single lab\",\n      \"pmids\": [\"10557092\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"An essential phosphorylation-site domain of CDC25C (aa ~200–256) interacts with both 14-3-3 proteins and cyclins (via the cyclin P-box motif). NMR and circular dichroism reveal two alpha-helical moieties interconnected by a loop carrying the 14-3-3 binding site; helical folding is induced upon 14-3-3 binding, suggesting conformational regulation.\",\n      \"method\": \"NMR spectroscopy, circular dichroism, in vitro binding assays with purified 14-3-3 and cyclins, domain analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structure with biochemical binding validation, single lab\",\n      \"pmids\": [\"10864927\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Arsenite induces CDC25C degradation via the ubiquitin-proteasome pathway. Mutation of the KEN box within residues 151–157 of CDC25C, or competition with a KEN-box peptide, partially inhibits arsenite-induced CDC25C ubiquitination. This CDC25C degradation contributes to G2/M arrest.\",\n      \"method\": \"Ubiquitination assay, proteasome inhibition, KEN-box mutagenesis, KEN-box peptide competition\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis and peptide competition with biochemical readout, single lab\",\n      \"pmids\": [\"11842186\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"p53 represses CDC25C transcription via two independent mechanisms: (1) direct binding of p53 to a site in the cdc25C promoter; (2) a CDE/CHR element-dependent mechanism not requiring p53 direct binding. Three CCAAT elements previously implicated do not mediate repression at physiologically relevant p53 levels.\",\n      \"method\": \"Reporter gene assay with promoter mutations, p53 binding site mutation, gel shift/EMSA, cell-based p53 induction at physiological levels\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic promoter dissection with multiple mutations and functional readouts, independently corroborated by other labs studying CDC25C promoter regulation\",\n      \"pmids\": [\"15574328\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"CDC25C interacts with PCNA, as identified by yeast two-hybrid and confirmed by in vitro and in vivo co-immunoprecipitation. CDC25C and PCNA transiently co-immunoprecipitate and co-localize in the nucleus at the beginning of M phase in Jurkat cells.\",\n      \"method\": \"Yeast two-hybrid, in vitro binding assay, co-immunoprecipitation from Jurkat cells, immunofluorescence co-localization\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — yeast two-hybrid confirmed by co-IP and co-localization, single lab\",\n      \"pmids\": [\"11896603\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PP2A:B56δ dephosphorylates CDC25C both during interphase and at mitosis. Loss of PP2A:B56δ (stable knockdown or mouse KO) results in prolonged CDC25C hyperphosphorylation/activation and persistent Cdk1 activation, causing delayed mitotic exit. This is compensated by transcriptional upregulation of Wee1 kinase.\",\n      \"method\": \"Stable knockdown, mouse knockout, biochemical analysis of CDC25C and Cdk1 phosphorylation, mitotic timing assay, Wee1 expression analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO in mice corroborated by stable knockdown, biochemical mechanistic readouts, and compensation analysis\",\n      \"pmids\": [\"18056802\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Xp38γ/SAPK3 phosphorylates Xenopus Cdc25C on Ser205 and promotes meiotic G2/M transition. Overexpression of constitutively active MKK6-Xp38γ induces oocyte maturation without progesterone; kinase-dead MKK6 and Xp38γ inhibit progesterone-induced maturation. This requires neither Mos/MAPK nor protein synthesis.\",\n      \"method\": \"Xenopus oocyte overexpression, constitutively active/dominant-negative mutants, immunoprecipitation kinase assay, site identification\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional gain/loss-of-function in oocytes with kinase assay and site mapping, single lab\",\n      \"pmids\": [\"14592973\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Cdc25C knockout mice are viable, fertile, and display no obvious abnormalities. MEFs lacking Cdc25C show normal cdc2 phosphorylation, normal timing of mitotic entry, and normal DNA damage responses. This demonstrates Cdc25C is dispensable for embryonic and adult cell cycles in mice, suggesting functional redundancy with Cdc25A and/or Cdc25B.\",\n      \"method\": \"Mouse gene knockout, MEF cell cycle analysis, DNA damage response assay, tissue expression analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout in mice with comprehensive phenotypic analysis; confirmed by Cdc25B/C double-KO study (PMID 15767688)\",\n      \"pmids\": [\"11359894\", \"15767688\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"CDC25C functional phosphatase activity is required for S-phase entry in human cells. CDC25C protein and activity increase at S-phase onset. Antisense, siRNA, or microinjection of anti-CDC25C antibodies inhibits DNA synthesis; re-introduction of wild-type but not catalytically-dead (C377S) CDC25C restores normal cell cycle progression.\",\n      \"method\": \"siRNA knockdown, antisense microinjection, immunoprecipitate phosphatase activity assay from synchronized HeLa cells, wild-type vs. C377S rescue\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with multiple approaches plus catalytic mutant rescue, single lab; contrasts with mouse KO data suggesting redundancy\",\n      \"pmids\": [\"12857880\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"LZTS1/Fez1 interacts with Cdk1 and Cdc25C during mitosis. In Lzts1−/− MEFs, Cdc25C degradation is increased during M phase, resulting in decreased Cdk1 activity, accelerated mitotic progression, resistance to taxol/nocodazole-induced M-phase arrest, and improper chromosome segregation.\",\n      \"method\": \"Lzts1 knockout mouse, MEF biochemical analysis, Cdc25C stability assay, Cdk1 activity assay, chromosome segregation analysis\",\n      \"journal\": \"Cancer cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with biochemical mechanistic readouts, single lab\",\n      \"pmids\": [\"17349584\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Telomere damage (via TRF2 or POT1 depletion) activates ATR/ATM, which phosphorylate CHK1/CHK2, leading to S216 phosphorylation of CDC25C, its nuclear export, and proteasomal degradation. This CDC25C degradation is required to sustain G2/M arrest from dysfunctional telomeres. Additionally, p53 transcriptionally downregulates CDC25C in this context.\",\n      \"method\": \"TRF2/POT1 siRNA depletion, CHK1/2 inhibition, proteasome inhibition, phospho-S216 CDC25C detection, checkpoint abrogation readout\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockdowns with biochemical mechanistic readouts, single lab, multiple orthogonal interventions\",\n      \"pmids\": [\"22842784\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Mdm2 physically interacts with CDC25C and promotes its proteasomal degradation in a ubiquitin-independent manner, reducing CDC25C half-life. Either Mdm2 overexpression or CDC25C downregulation delays cell cycle progression through G2/M. This is a p53-independent pathway, providing a dual mechanism (p53-mediated transcriptional repression + Mdm2-mediated protein degradation) for p53/Mdm2 to enforce G2/M arrest.\",\n      \"method\": \"Co-immunoprecipitation, Mdm2 siRNA, half-life assay, proteasome inhibition, cell cycle timing analysis\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal interaction and stability assays with functional readout, single lab\",\n      \"pmids\": [\"28806397\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"During interphase, CDC25C phosphatase dephosphorylates phospho-Thr-838 in the activation loop of ASK1, suppressing ASK1-mediated apoptosis. CDC25C knockdown increases ASK1 activity; CDC25C overexpression inhibits ASK1-mediated apoptosis. During mitotic arrest, hyperphosphorylated CDC25C has reduced affinity for ASK1, allowing increased ASK1 activity. This reveals a cell cycle-dependent role for CDC25C in suppressing apoptosis during interphase.\",\n      \"method\": \"In vitro phosphatase assay (CDC25C on ASK1 pThr-838), siRNA knockdown of CDC25C, co-immunoprecipitation, ASK1 activity assay, apoptosis assay\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro phosphatase assay with physiological substrate plus cell-based knockdown/overexpression, single lab\",\n      \"pmids\": [\"25633196\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"A fraction of CDC25C localizes to centrosomes in a cell cycle-dependent manner from late S phase through mitosis. CDC25C co-localizes with Cyclin B1 at centrosomes in G2 and prophase, and both undergo dynamic exchange between centrosome and cytoplasm (FRAP). Centrosomal localization is mediated by the catalytic C-terminal domain but does not require catalytic activity. Phosphatase-dead and substrate-binding mutants of CDC25C accumulate at centrosomes with phospho-Y15-Cdk1 and behave as dominant negatives that impair mitotic entry.\",\n      \"method\": \"Immunofluorescence, FRAP live-cell imaging, C-terminal domain deletion/mutant analysis, phosphatase-dead and hotspot mutants, dominant-negative assay\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct live-cell imaging (FRAP) with mutagenesis and functional readout, single lab\",\n      \"pmids\": [\"18604163\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Cyclin E/CDK2 physically interacts with and phosphorylates CDC25C on Ser214, leading to premature CDC25C activation. Low molecular weight (LMW) cyclin E overexpression causes premature inactivation of CDC25C and PLK1, leading to faster mitotic exit. Downregulation of CDC25C inhibits LMW-E-mediated chromosome missegregation, anaphase bridges, and centrosome amplification.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, CDC25C phosphatase activity assay, siRNA knockdown of CDC25C, chromosome segregation/centrosome analysis\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP confirmed kinase-substrate relationship with functional mutagenesis and knockdown readout, single lab\",\n      \"pmids\": [\"20530684\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"HIV-1 Vpr directly binds CDC25C in vitro and in mammalian cells and inhibits CDC25C phosphatase activity in vitro by binding a site distinct from the catalytic site. Expression of a Cdc25C mutant with reduced Vpr binding or siRNA depletion of Cdc25C reduces Vpr-mediated G2 arrest.\",\n      \"method\": \"In vitro binding assay, co-immunoprecipitation from mammalian cells, in vitro phosphatase inhibition assay, CDC25C mutant with reduced Vpr binding, CDC25C depletion\",\n      \"journal\": \"Virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro binding and phosphatase assay confirmed in cells with loss-of-function rescue, single lab\",\n      \"pmids\": [\"14972559\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"Microinjected antibody to hamster/human CDC25C inhibits chromosome condensation induced by loss of RCC1 function (tsBN2 mutation), demonstrating that CDC25C is required for p34cdc2 kinase activation in this context. CDC25C is located predominantly in the cytoplasm (periphery of nuclei) in interphase cells and moves into the nucleus upon loss of RCC1 function.\",\n      \"method\": \"Antibody microinjection, tsBN2 cell genetic system, immunofluorescence localization\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — antibody microinjection with genetic system readout and direct localization, single lab\",\n      \"pmids\": [\"1337289\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"p53-dependent repression of CDC25C requires activation of p21 (CDKN1A), which causes replacement of the MMB (B-MYB-MuvB) complex by the DREAM complex at CDE/CHR elements in the CDC25C promoter. ChIP shows E2F4 and p130 (DREAM components) replace B-MYB upon p53 activation; mutations in CDE/CHR elements abolish p53-dependent repression. No p53 binding to the CDC25C promoter is detected by ChIP.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), promoter reporter assays with CDE/CHR mutations, p21 knockdown epistasis\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and promoter mutagenesis with epistasis, single lab; refines mechanism of prior studies\",\n      \"pmids\": [\"26595675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PUF60, a poly(U)-binding splicing factor, controls alternative splicing of CDC25C. PUF60 knockdown causes exon 3 skipping in CDC25C, leading to nonsense-mediated mRNA decay and decreased CDC25C protein, thereby inhibiting G2/M transition and cancer cell proliferation.\",\n      \"method\": \"Systematic splicing factor analysis in LUAD, siRNA knockdown of PUF60, RNA-seq for splice variant detection, cell cycle analysis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNA-seq splice variant identification with functional knockdown and cell cycle readout, single lab\",\n      \"pmids\": [\"37682709\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CDC25C is a dual-specificity phosphatase that activates the Cdk1 (cdc2)/cyclin B complex at the G2/M transition by dephosphorylating Thr14 and Tyr15 on Cdk1; it is regulated by an intricate network of post-translational modifications—including inhibitory phosphorylation at S216 by Chk1, Chk2, C-TAK1, CaMKII, JNK, and ERK, and activating phosphorylation at multiple sites by cdc2-cyclin B (positive feedback loop), Plk1, PLK3, ERK/MAPK, and Pim-1—that control its phosphatase activity and nucleocytoplasmic localization; during interphase, S216 phosphorylation promotes 14-3-3 binding, which sequesters CDC25C in the cytoplasm by blocking nuclear import, while an intrinsic NES mediates its nuclear export; at mitotic entry, Plk1-mediated S198 phosphorylation overcomes nuclear exclusion; Pin1-catalyzed prolyl isomerization facilitates PP2A-mediated dephosphorylation of CDC25C; Mdm2 promotes CDC25C proteasomal degradation in a ubiquitin-independent manner; p53 represses CDC25C transcription through direct promoter binding and via the p21-DREAM-CDE/CHR pathway; and beyond its canonical mitotic role, CDC25C additionally dephosphorylates and suppresses ASK1 during interphase, interacts with PCNA at the G2/M boundary, and localizes dynamically to centrosomes to amplify Cdk1 activation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CDC25C is a dual-specificity phosphatase that drives the G2/M transition by activating the cdc2(Cdk1)-cyclin B kinase, and its own phosphatase activity is in turn amplified through a positive feedback loop in which active cdc2-cyclin B phosphorylates CDC25C on multiple sites to increase its activity 2-3-fold and trigger premature mitotic entry [#1, #3]. This autoamplification is held in check during interphase by PP2A, which keeps CDC25C dephosphorylated and inactive; the conformation-specific PP2A:B56\\u03b4 holoenzyme, acting on trans pSer/Thr-Pro motifs generated by Pin1-catalyzed prolyl isomerization, restrains CDC25C and Cdk1 activity until mitotic exit [#2, #7, #26]. CDC25C activity and localization are governed by an extensive phosphorylation network: inhibitory phosphorylation of Ser216 by Chk1, Chk2, C-TAK1, and CaMKII creates a 14-3-3 binding site that enforces cytoplasmic retention by blocking nuclear import, working together with an intrinsic N-terminal nuclear export signal [#0, #4, #6, #17, #19, #22], while activating phosphorylation by Plk1/PLK on Ser198, by Plk3 on Ser191, and by ERK/MAPK on Thr48 overcomes nuclear exclusion and stimulates phosphatase activity at mitotic entry [#8, #9, #14, #15]. This network couples CDC25C to checkpoint and stress signaling: DNA-damage and replication checkpoints converge on Ser216 phosphorylation and 14-3-3 sequestration to enforce G2 arrest [#0, #11], stress kinases such as JNK inactivate CDC25C, and oxidative stress drives an intramolecular disulfide bond that triggers degradation [#13, #16]. CDC25C levels are further controlled by p53, which represses its transcription both by direct promoter binding and through the p21-dependent DREAM/CDE-CHR pathway, and by Mdm2, which promotes ubiquitin-independent proteasomal degradation, together enforcing G2/M arrest [#24, #32, #38]. Beyond mitotic control, CDC25C dephosphorylates the activation-loop Thr838 of ASK1 to suppress apoptosis during interphase, and a centrosomal pool co-localizes with cyclin B1 to locally amplify Cdk1 activation [#33, #34]. Genetic ablation in mice shows CDC25C is dispensable for normal cell cycles, indicating functional redundancy with CDC25A/B [#28].\",\n  \"teleology\": [\n    {\n      \"year\": 1992,\n      \"claim\": \"Established that CDC25C is functionally required for cdc2 kinase activation and chromosome condensation, and that it is cytoplasmic in interphase but enters the nucleus upon checkpoint loss.\",\n      \"evidence\": \"Antibody microinjection in the tsBN2 (RCC1-mutant) genetic system with immunofluorescence localization\",\n      \"pmids\": [\"1337289\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of nuclear relocalization not defined\", \"Substrate specificity for Cdk1 sites not yet mapped\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Defined the core mitotic feedback loop: cdc2-cyclin B phosphorylation directly activates CDC25C, while PP2A keeps it inactive during interphase, framing the switch-like onset of mitosis.\",\n      \"evidence\": \"Xenopus egg extract and HeLa extract biochemistry with okadaic acid, PP2A catalytic subunit addition, and oocyte maturation assays\",\n      \"pmids\": [\"8428594\", \"8389619\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific activating phosphosites not yet mapped\", \"Identity of the PP2A holoenzyme not defined\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Mapped the cdc2-cyclin B activating phosphorylation to five sites and showed phosphorylation is functionally sufficient to drive premature prophase, defining the autoamplification mechanism.\",\n      \"evidence\": \"In vitro kinase assay, tryptic phosphopeptide mapping, peptide sequencing, microinjection into fibroblasts\",\n      \"pmids\": [\"8119945\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address how the loop is initially triggered\", \"Spatial regulation not addressed\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Biochemically purified an unidentified Ser216 kinase binding within aa 200-256, anticipating the regulatory checkpoint axis before its molecular identity was known.\",\n      \"evidence\": \"8000-fold protein purification from rat liver with in vitro kinase assay and domain mapping\",\n      \"pmids\": [\"7982962\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Kinase identity not molecularly defined at the time\", \"Functional consequence of S216 phosphorylation not yet established\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Connected the DNA-damage/replication checkpoint to CDC25C by showing Chk1 phosphorylates Ser216 to create a 14-3-3 site whose loss abrogates G2 arrest, establishing the checkpoint-CDC25C-14-3-3 axis.\",\n      \"evidence\": \"In vitro Chk1 kinase assay, S216A mutagenesis, and checkpoint abrogation assays\",\n      \"pmids\": [\"9278512\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How 14-3-3 binding alters localization not yet resolved\", \"Other Ser216 kinases not addressed\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Identified C-TAK1 as a constitutive Ser216 kinase that directly binds CDC25C and promotes 14-3-3 binding, broadening the set of kinases enforcing cytoplasmic sequestration.\",\n      \"evidence\": \"In vitro kinase assay, Co-IP in COS-7 cells, bacterial co-expression, 14-3-3 binding assay\",\n      \"pmids\": [\"9543386\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological context distinguishing C-TAK1 from Chk1 not defined\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Demonstrated that the 14-3-3-binding region (aa 201-258) mediates cytoplasmic retention and that disrupting 14-3-3 binding enables premature chromosome condensation, identifying 14-3-3 as the dominant interphase retention mechanism.\",\n      \"evidence\": \"Immunofluorescence with deletion/point mutagenesis, premature chromosome condensation assay, leptomycin B treatment\",\n      \"pmids\": [\"10330186\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution of NES not yet quantified\", \"Mechanism by which 14-3-3 blocks import unresolved\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Showed CaMKII phosphorylates and activates CDC25C and is required for G2/M progression, linking calcium signaling to mitotic entry.\",\n      \"evidence\": \"In vitro CaMKII kinase/phosphatase assay, HeLa synchronization, KN-93 and peptide inhibitor microinjection\",\n      \"pmids\": [\"10075693\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Phosphosite not mapped in this study\", \"Single lab\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Resolved the import/export logic of CDC25C trafficking, showing an intrinsic N-terminal NES drives export while 14-3-3 binding negatively regulates nuclear import.\",\n      \"evidence\": \"Leptomycin B export inhibition, NES and 14-3-3-binding mutants, immunofluorescence\",\n      \"pmids\": [\"11313932\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Import receptor not identified\", \"How mitotic kinases override NES not yet addressed\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Provided a structural basis for conformational regulation, showing the regulatory domain binds both 14-3-3 and cyclins and folds into helices upon 14-3-3 binding.\",\n      \"evidence\": \"NMR spectroscopy, circular dichroism, in vitro binding with purified 14-3-3 and cyclins\",\n      \"pmids\": [\"10864927\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length structure not solved\", \"Functional consequence of cyclin P-box binding not defined\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Introduced Pin1 prolyl isomerization as a conformational checkpoint that renders CDC25C competent for PP2A-mediated dephosphorylation, coupling proline-directed phosphorylation to phosphatase access.\",\n      \"evidence\": \"In vitro prolyl isomerase and conformation-specific PP2A assays, yeast genetic epistasis, in vivo cell division with Pin1 catalytic mutants\",\n      \"pmids\": [\"11090625\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific isomerized motifs in CDC25C not fully enumerated\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Linked the G2 checkpoint to therapy by showing UCN-01 inhibits Chk1-mediated Ser216 phosphorylation and abrogates 14-3-3 binding, validating the axis as a drug target.\",\n      \"evidence\": \"In vitro Chk1 kinase assay and IP of CDC25C/14-3-3 complexes from irradiated cells\",\n      \"pmids\": [\"10681541\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Off-target kinase effects of UCN-01 not fully excluded\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Established polo-like kinase as a direct activating kinase of CDC25C, increasing phosphatase activity toward cdc2-cyclin B.\",\n      \"evidence\": \"In vitro kinase assay with endogenous and recombinant PLK, phosphatase activity assay\",\n      \"pmids\": [\"11202906\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Activating phosphosite not mapped here\", \"In vivo requirement not established\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Demonstrated in a cell-free meiotic system that polo-like kinase (Plx1) is necessary for Cdc25C and Cdc2 activation, establishing PLK as an upstream requirement.\",\n      \"evidence\": \"Immunodepletion of Plx1 from Xenopus oocyte extract with maturation assay\",\n      \"pmids\": [\"11408585\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct vs. indirect requirement not separated\", \"Mammalian generality from oocyte system\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Showed via knockout that Cdc25C is dispensable for mouse development and cell cycles, revealing functional redundancy among CDC25 family members.\",\n      \"evidence\": \"Cdc25C knockout mouse with MEF cell cycle and DNA damage response analysis (confirmed by Cdc25B/C double-KO)\",\n      \"pmids\": [\"11359894\", \"15767688\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Degree of compensation by CDC25A/B not quantified\", \"Cell-context-specific non-redundant roles not excluded\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Refined the spatial activation step by showing Plk1 phosphorylates Ser198 within the NES to promote nuclear localization at prophase.\",\n      \"evidence\": \"In vitro kinase assay, S198A mutant, constitutively active Plk1, immunofluorescence\",\n      \"pmids\": [\"11897663\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Interplay with 14-3-3 release not fully resolved\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Established Chk2, in both monomeric and dimeric forms, as a DNA-damage-responsive CDC25C kinase, expanding the checkpoint kinase repertoire converging on CDC25C.\",\n      \"evidence\": \"Purification of Chk2 \\u00b1 DNA damage, in vitro kinase assay on Cdc25C, biophysical sizing\",\n      \"pmids\": [\"12386164\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo site preference vs. Chk1 not distinguished\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Identified arsenite-induced, KEN-box-dependent ubiquitin-proteasome degradation of CDC25C as a route to G2/M arrest, introducing proteolytic control of CDC25C abundance.\",\n      \"evidence\": \"Ubiquitination assay, proteasome inhibition, KEN-box mutagenesis and peptide competition\",\n      \"pmids\": [\"11842186\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Responsible E3 ligase not identified\", \"Physiological trigger beyond arsenite not defined\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Discovered a physical CDC25C-PCNA interaction at the G2/M boundary, hinting at coupling to replication/repair machinery.\",\n      \"evidence\": \"Yeast two-hybrid, in vitro binding, Co-IP and co-localization in Jurkat cells\",\n      \"pmids\": [\"11896603\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of the interaction not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Revealed redox control of CDC25C: H2O2 induces an active-site disulfide (C330-C377) that promotes degradation independently of Chk1, linking oxidative stress to CDC25C turnover.\",\n      \"evidence\": \"In vitro oxidation assay, C330/C377 mutants, stability and 14-3-3 binding assays\",\n      \"pmids\": [\"11925443\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo physiological oxidant source not defined\", \"Link to ubiquitin machinery not resolved\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Showed catalytically active CDC25C is required for human S-phase entry, extending its role beyond mitosis (in apparent contrast to mouse redundancy data).\",\n      \"evidence\": \"siRNA, antisense and antibody microinjection in HeLa, with wild-type vs. C377S rescue\",\n      \"pmids\": [\"12857880\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Discrepancy with mouse KO redundancy unresolved\", \"Relevant S-phase substrate not identified\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identified JNK/SAPK as a stress kinase that inactivates CDC25C via Ser168 phosphorylation, coupling stress signaling to mitotic inhibition.\",\n      \"evidence\": \"In vitro kinase assay, phospho-S168 detection, S168A rescue of cdc2-cyclin B activity (replicated)\",\n      \"pmids\": [\"12742231\", \"20220133\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for S168-mediated inactivation unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Defined CaMKII Ser287 (Xenopus) phosphorylation as a calcium-triggered inhibitory event delaying Cdc2-cyclin B activation, mechanistically linking fertilization signals to cell cycle timing.\",\n      \"evidence\": \"Xenopus egg extract biochemistry, Ca2+ addition, CaMKII inhibitors, in vitro kinase assay\",\n      \"pmids\": [\"14517314\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mammalian equivalent site context not fully mapped\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Showed Xp38\\u03b3/SAPK3 phosphorylates Cdc25C Ser205 to promote the meiotic G2/M transition independently of Mos/MAPK, adding a stress-kinase route to activation.\",\n      \"evidence\": \"Xenopus oocyte overexpression with CA/DN mutants, IP kinase assay, site identification\",\n      \"pmids\": [\"14592973\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mammalian relevance not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Established p53 as a transcriptional repressor of CDC25C through both direct promoter binding and a CDE/CHR-dependent route, placing CDC25C downstream of tumor suppressor signaling.\",\n      \"evidence\": \"Reporter assays with promoter mutations, EMSA, physiological p53 induction\",\n      \"pmids\": [\"15574328\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution of the two mechanisms not quantified at the time\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identified Plk3 as a kinase phosphorylating Ser191/Ser198 in the nuclear-exclusion motif, with phosphomimetics driving nuclear accumulation and reduced Cdc2-Y15.\",\n      \"evidence\": \"In vitro kinase assay, phosphomimetic/alanine mutagenesis, localization, Cdc2-Y15 western\",\n      \"pmids\": [\"14968113\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Distinct roles of Plk1 vs. Plk3 on overlapping sites not reconciled\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Showed Pim-1 activates CDC25C both directly by N-terminal phosphorylation and indirectly by inhibiting C-TAK1, adding an oncogenic kinase input to the activation network.\",\n      \"evidence\": \"Kinase assay, yeast two-hybrid, co-localization, MS site mapping, G2/M assay (two papers)\",\n      \"pmids\": [\"15319445\", \"16356754\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo significance of dual mechanism not quantified\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Demonstrated that HIV-1 Vpr binds CDC25C at a non-catalytic site to inhibit its phosphatase activity and drive viral G2 arrest, identifying CDC25C as a host target of viral cell cycle manipulation.\",\n      \"evidence\": \"In vitro binding and phosphatase inhibition, Co-IP, binding-deficient mutant and CDC25C depletion\",\n      \"pmids\": [\"14972559\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of inhibitory binding not solved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Established ERK/p42 MAPK as a major activating CDC25C kinase across systems, phosphorylating Thr48 (and T138/S205) to boost phosphatase activity and promote mitotic entry.\",\n      \"evidence\": \"Xenopus extract/oocyte biochemistry, Co-IP, in vitro kinase assay, site mapping, ERK inhibition in mammalian cells\",\n      \"pmids\": [\"17382881\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative contribution relative to PLK feedback not defined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identified PP2A:B56\\u03b4 as the specific holoenzyme dephosphorylating CDC25C at interphase and mitosis, with its loss causing persistent Cdk1 activity and delayed mitotic exit, defining the molecular counterweight to the activation loop.\",\n      \"evidence\": \"Stable knockdown and mouse KO, biochemical phosphorylation analysis, mitotic timing, Wee1 compensation\",\n      \"pmids\": [\"18056802\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Targeting mechanism of B56\\u03b4 to CDC25C not defined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Showed LZTS1/Fez1 stabilizes Cdc25C during mitosis to sustain Cdk1 activity and proper chromosome segregation, identifying a scaffold protecting CDC25C from M-phase degradation.\",\n      \"evidence\": \"Lzts1 knockout mouse, MEF biochemistry, Cdc25C stability and Cdk1 activity assays, segregation analysis\",\n      \"pmids\": [\"17349584\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which LZTS1 prevents degradation not defined\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Revealed a centrosomal pool of CDC25C that co-localizes with cyclin B1 to locally amplify Cdk1 activation; phosphatase-dead mutants act as dominant negatives impairing mitotic entry.\",\n      \"evidence\": \"Immunofluorescence, FRAP, C-terminal domain mutants, dominant-negative assay\",\n      \"pmids\": [\"18604163\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Centrosomal docking partner not identified\", \"Single lab\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Showed cyclin E/CDK2 phosphorylates CDC25C on Ser214 to cause premature activation, with LMW cyclin E driving CDC25C-dependent chromosomal instability, linking CDC25C to oncogenic cell cycle deregulation.\",\n      \"evidence\": \"Co-IP, in vitro kinase assay, phosphatase activity assay, CDC25C siRNA, segregation/centrosome analysis\",\n      \"pmids\": [\"20530684\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological role of S214 in normal cycle not defined\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Integrated telomere dysfunction into the CDC25C axis, showing ATR/ATM-CHK1/2 signaling drives S216 phosphorylation, nuclear export, and degradation of CDC25C to sustain G2/M arrest, with p53 transcriptional input.\",\n      \"evidence\": \"TRF2/POT1 depletion, CHK1/2 and proteasome inhibition, phospho-S216 detection, checkpoint readout\",\n      \"pmids\": [\"22842784\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"E3 ligase for CDC25C degradation in this context not identified\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Uncovered a non-mitotic role: CDC25C dephosphorylates ASK1 activation-loop Thr838 to suppress apoptosis during interphase, with hyperphosphorylated mitotic CDC25C releasing this inhibition.\",\n      \"evidence\": \"In vitro phosphatase assay on ASK1 pThr838, CDC25C siRNA/overexpression, Co-IP, ASK1 activity and apoptosis assays\",\n      \"pmids\": [\"25633196\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo significance of CDC25C-ASK1 axis not established\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Refined p53-mediated repression to a p21-dependent DREAM-complex mechanism, showing DREAM replaces MMB at CDE/CHR elements with no detectable p53 promoter binding.\",\n      \"evidence\": \"ChIP, promoter reporter with CDE/CHR mutations, p21 knockdown epistasis\",\n      \"pmids\": [\"26595675\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Reconciliation with earlier direct-p53-binding model not fully resolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified Mdm2 as a p53-independent route to CDC25C downregulation, promoting ubiquitin-independent proteasomal degradation, completing a dual p53/Mdm2 mechanism for G2/M arrest.\",\n      \"evidence\": \"Co-IP, Mdm2 siRNA, half-life assay, proteasome inhibition, cell cycle timing\",\n      \"pmids\": [\"28806397\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of ubiquitin-independent degradation unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Added a post-transcriptional layer, showing the splicing factor PUF60 controls CDC25C exon 3 inclusion, with its loss triggering NMD and reduced CDC25C to impair G2/M and proliferation.\",\n      \"evidence\": \"Splicing factor screen in LUAD, PUF60 siRNA, RNA-seq splice variant detection, cell cycle analysis\",\n      \"pmids\": [\"37682709\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Regulation of PUF60 activity toward CDC25C not defined\", \"Generality beyond LUAD not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how the dense, sometimes overlapping phosphorylation inputs (multiple activating and inhibitory kinases on shared sites) are temporally integrated to produce the switch-like CDC25C activation, and which E3 ligases mediate its various degradation routes.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified quantitative model of competing phosphorylation inputs\", \"E3 ligases for checkpoint, arsenite, and Mdm2-associated degradation not all identified\", \"Discrepancy between human S-phase requirement and mouse dispensability unresolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 3, 29, 33, 34]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [1, 29, 33]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 33]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [5, 6, 20, 37]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [6, 8, 14, 25, 37]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [34]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [1, 3, 26, 29]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [0, 11, 31]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [33]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [24, 38]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CDK1\", \"CCNB1\", \"YWHAB\", \"CHEK1\", \"CHEK2\", \"PLK1\", \"PCNA\", \"MDM2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":7,"faith_total":7,"faith_pct":100.0}}