{"gene":"PBK","run_date":"2026-06-10T05:19:53","timeline":{"discoveries":[{"year":2004,"finding":"TOPK is phosphorylated at Thr-9 by CDK1/cyclin B during mitosis, causing TOPK to associate with mitotic spindles; suppression of TOPK expression disrupts spindle midzone formation and cytokinesis.","method":"Immunofluorescence, Western blot, kinase assay, siRNA knockdown with phenotypic readout","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (kinase assay, immunofluorescence, functional knockdown), replicated in subsequent studies","pmids":["15541388"],"is_preprint":false},{"year":2007,"finding":"TOPK forms a complex with CDK1/cyclin B1 and PRC1 on microtubules during mitosis; TOPK enhances CDK1/cyclin B1-dependent phosphorylation of PRC1 at T481 (requiring both TOPK enzymatic activity and physical association with PRC1), thereby promoting cytokinesis.","method":"Co-immunoprecipitation, in vitro kinase assay, in vivo phosphorylation analysis, functional overexpression/knockdown","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — reciprocal Co-IP, in vitro kinase assay, in vivo phosphorylation, and functional rescue, single lab with multiple orthogonal methods","pmids":["17512944"],"is_preprint":false},{"year":2007,"finding":"TOPK and ERK2 form a positive feedback loop: TOPK phosphorylates ERK2 and ERK2 phosphorylates TOPK; EGF-stimulated knockdown of either reduces phosphorylation of the other and blocks downstream ERK2 substrate phosphorylation.","method":"In vitro kinase assay, siRNA knockdown, transient transfection, Western blot in HCT116 cells","journal":"Gastroenterology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro kinase assay plus reciprocal knockdown experiments, single lab","pmids":["17631144"],"is_preprint":false},{"year":2006,"finding":"PBK/TOPK is necessary for appropriate p38 MAPK activation by growth factors; PBK knockdown impairs p38 activation, reduces cell motility, and results in an impaired DNA damage response (decreased γ-H2AX generation, increased DNA damage).","method":"siRNA knockdown, Western blot, clonogenic assay, motility assay","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA knockdown with multiple defined phenotypic readouts, single lab","pmids":["17160018"],"is_preprint":false},{"year":2005,"finding":"PBK/TOPK phosphorylates p38 MAPK and is activated in a cell-cycle-dependent manner in neural progenitor cells; inhibition of this pathway disrupts progenitor proliferation and self-renewal.","method":"In vitro kinase assay, cell-cycle synchronization, transgenic ablation with lineage tracing in mice","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro kinase assay and in vivo genetic ablation, single lab, multiple methods","pmids":["16291951"],"is_preprint":false},{"year":2005,"finding":"TOPK-Thr-9 is specifically phosphorylated by CDK1/cyclin B during both mitotic and meiotic phases in spermatogenic cells, implicating TOPK in cytokinesis and/or chromosomal segregation during spermatogenesis.","method":"Immunohistochemistry, Western blot with phospho-specific antibodies on testis sections","journal":"Development, growth & differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phospho-specific antibody analysis in defined cell-cycle stages, single lab","pmids":["16316408"],"is_preprint":false},{"year":2010,"finding":"TOPK physically interacts with the DNA-binding domain of p53 (including five common point mutants); PBK/TOPK knockdown upregulates p53 target genes (p21, apoptotic genes) particularly after genotoxic damage, indicating PBK suppresses p53 transactivation function.","method":"Co-immunoprecipitation, yeast two-hybrid, gene microarray, siRNA knockdown with qPCR/Western blot readouts in HCT116 and MCF-7 cells","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP plus yeast two-hybrid plus functional knockdown with transcriptional readouts, single lab but multiple orthogonal methods","pmids":["20622899"],"is_preprint":false},{"year":2007,"finding":"PBK physically interacts with p53 (detected by Co-IP and yeast two-hybrid) and downregulates p53, enabling cells to bypass DNA damage checkpoint; a phosphomimetic PBK mutant promotes polyploidization and aberrant mitotic entry after doxorubicin treatment.","method":"Co-immunoprecipitation, yeast two-hybrid, ectopic overexpression with flow cytometry (MPM-2 marker)","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and yeast two-hybrid with functional overexpression readout, single lab","pmids":["17482142"],"is_preprint":false},{"year":2010,"finding":"TOPK binds Prx1 and phosphorylates it at Ser-32; this phosphorylation alters the secondary structure of Prx1 and enhances its peroxidase activity, blocking UVB-induced H2O2 accumulation and apoptosis in melanoma cells.","method":"LC-MS/MS pulldown identification, in vitro kinase assay, CD spectroscopy of Prx1/S32A mutant, flow cytometry, stable siRNA knockdown","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay, structural (CD spectra), and functional mutant analysis in single lab with multiple orthogonal approaches","pmids":["20647304"],"is_preprint":false},{"year":2011,"finding":"TOPK negatively regulates p38α activity by phosphorylating the p38α-specific phosphatase MKP1 and enhancing MKP1 stability; TOPK-knockout mice display markedly increased skin inflammation after solar UV irradiation.","method":"In vitro kinase assay, Western blot, TOPK knockout mouse model with inflammation phenotype","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vitro kinase assay plus knockout mouse with defined phenotype, replicated mechanistically","pmids":["21715333"],"is_preprint":false},{"year":2010,"finding":"PBK/TOPK phosphorylates LGN/GPSM2 at Thr450 during mitosis; overexpression of non-phosphorylatable LGN/GPSM2-T450A causes aberrant chromosomal segregation and growth suppression in breast cancer cells.","method":"In vitro kinase assay, Western blot with phospho-specific analysis, siRNA knockdown, mutant overexpression with phenotypic readout","journal":"Genes, chromosomes & cancer","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro kinase assay with defined phosphosite plus functional phospho-mutant rescue, single lab multiple methods","pmids":["20589935"],"is_preprint":false},{"year":2013,"finding":"TOPK/PBK is ubiquitinated and targeted for degradation by the E3 ubiquitin ligase CHFR; TOPK in turn phosphorylates and inactivates PTEN, which activates Akt, facilitating G2/M progression in a CHFR-mediated mitotic checkpoint pathway.","method":"Co-immunoprecipitation, ubiquitination assay, in vitro kinase assay, siRNA knockdown with cell-cycle readout","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, ubiquitination assay, and kinase assay in single lab, multiple methods","pmids":["24012691"],"is_preprint":false},{"year":2016,"finding":"Src directly binds and phosphorylates TOPK at Tyr74 and Tyr272; these phosphorylations increase TOPK stability by inhibiting its ubiquitination and enhance TOPK kinase activity (measured by Histone H3-Ser10 phosphorylation); TOPK-Y74F/Y272F double mutant displays reduced tumorigenic activity.","method":"In vitro kinase assay with recombinant proteins, phospho-specific antibody generation, stable transfection with mutants, Co-IP, pulse-chase protein stability assay, Src-knockout MEFs","journal":"Oncotarget","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro kinase assay, phospho-specific antibody, genetic knockout cells, pulse-chase stability, and in vivo tumorigenesis, single lab multiple orthogonal methods","pmids":["27016416"],"is_preprint":false},{"year":2017,"finding":"CDK1 phosphorylates PBK at Thr-9 (and also Thr-24, Ser-32, Ser-59) during mitosis; Thr-9 phosphorylation is required for normal cytokinesis; non-phosphorylatable PBK-T9A augments tumorigenesis more than wild-type PBK, indicating mitotic phosphorylation inhibits PBK's oncogenic activity.","method":"In vitro kinase assay, phospho-site mutagenesis, stable cell lines, soft agar assay, immunofluorescence cytokinesis analysis","journal":"Cellular signalling","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay with defined phosphosites plus functional mutagenesis in oncogenesis assays, single lab multiple methods","pmids":["28780319"],"is_preprint":false},{"year":2015,"finding":"TOPK/PBK is the master kinase responsible for phosphorylating the conserved linker region of C2H2 zinc finger proteins (ZFPs) during mitosis, causing their dissociation from condensing chromatin; TOPK is activated by CDK1 and acts as the global ZFP linker kinase.","method":"Kinase inhibitor panel screen, biotinylated K252a affinity purification, in vitro kinase assay, in vivo phosphorylation correlation","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — affinity purification followed by in vitro and in vivo validation, single lab","pmids":["25575812"],"is_preprint":false},{"year":2014,"finding":"TOPK inhibition with OTS964 causes cytokinesis defects and subsequent apoptosis of cancer cells, similar to siRNA knockdown; TOPK kinase inhibition (not just expression loss) is sufficient to block cytokinesis.","method":"In vitro kinase assay, siRNA comparison, xenograft tumor models, liposomal drug formulation","journal":"Science translational medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — defined mechanism (cytokinesis defect) confirmed by both siRNA and inhibitor, replicated in vivo, rigorous controls","pmids":["25338756"],"is_preprint":false},{"year":2016,"finding":"TOPK promotes lung cancer resistance to EGFR-TKIs by directly binding and phosphorylating c-Jun, which activates AP-1 target genes CCND1 and CDC2; TOPK silencing sensitizes TKI-resistant cells to gefitinib.","method":"Co-immunoprecipitation, in vitro kinase assay, luciferase reporter, siRNA knockdown with drug-sensitivity assay, xenograft model","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and in vitro kinase assay with functional readouts, single lab","pmids":["26745678"],"is_preprint":false},{"year":2019,"finding":"MET phosphorylates TOPK at Tyr74, preventing apoptosis in gefitinib-resistant NSCLC cells; this is part of the COX2-TXA2-MET-TOPK axis.","method":"Western blot with phospho-specific antibodies, in vitro signaling analysis, inhibitor combination studies in vitro and in vivo","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phospho-specific detection, pathway inhibitor validation, single lab","pmids":["31611604"],"is_preprint":false},{"year":2019,"finding":"TOPK directly binds and phosphorylates ULK1 at Ser469, Ser495, and Ser533, decreasing ULK1 activity and stability and thereby inhibiting autophagy initiation in glioma cells.","method":"Co-immunoprecipitation, in vitro kinase assay with identified phosphosites, Western blot, autophagy flux assay","journal":"Cell death & disease","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay with defined phosphosites, Co-IP, and functional autophagy readout in single lab with multiple methods","pmids":["31378785"],"is_preprint":false},{"year":2018,"finding":"TOPK promotes microglia/macrophage M2 polarization by binding to HDAC1 and HDAC2 and promoting their phosphorylation, inhibiting their deacetylase activity; this contributes to neuroprotection after cerebral ischemia.","method":"Co-immunoprecipitation (in vivo binding), in vitro TOPK overexpression in BV2 cells, immunofluorescence co-localization, Western blot","journal":"Aging and disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with co-localization and functional overexpression readout, single lab","pmids":["29896413"],"is_preprint":false},{"year":2014,"finding":"TOPK activates NF-κB by interacting with and phosphorylating IκBα in response to LPS, promoting iNOS transcription and nitric oxide production in leukemia cells.","method":"Co-immunoprecipitation, in vitro kinase assay against IκBα, NF-κB/iNOS promoter-driven luciferase assay, siRNA knockdown","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, in vitro kinase assay, and promoter reporter, single lab","pmids":["24440499"],"is_preprint":false},{"year":2019,"finding":"PBK promotes HCC metastasis via the ETV4-uPAR signaling pathway: PBK enhances binding of ETV4 to the uPAR promoter (shown by ChIP assay), activating uPAR transcription; uPAR overexpression rescues PBK-knockdown metastatic phenotype in vivo.","method":"ChIP assay, promoter reporter assay, gain/loss-of-function in vitro migration/invasion, orthotopic mouse model","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP assay and in vivo rescue experiment, single lab","pmids":["30914208"],"is_preprint":false},{"year":2021,"finding":"PBK phosphorylates MSL1, enhancing MSL1 interaction with MSL2, MSL3, and KAT8 (MSL complex components), promoting MSL complex enrichment on the CD276 promoter, increasing histone H4 K16 acetylation and CD276 transcription in nasopharyngeal carcinoma.","method":"Co-immunoprecipitation, in vitro kinase assay, ChIP assay, histone acetylation assay","journal":"Oncogenesis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — kinase assay, Co-IP, and ChIP, single lab with multiple methods","pmids":["33431797"],"is_preprint":false},{"year":2022,"finding":"PBK directly interacts with TRIM37 and promotes its phosphorylation and nuclear translocation, activating the NFκB pathway and conferring PARPi resistance in ovarian cancer.","method":"Co-immunoprecipitation, Western blot for nuclear translocation, NF-κB pathway analysis, in vitro and in vivo drug resistance assays","journal":"Experimental & molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with functional in vitro and in vivo validation, single lab","pmids":["35859118"],"is_preprint":false},{"year":2022,"finding":"ERK2 phosphorylates TOPK at Ser32 (a novel site beyond the previously known Thr9), and p-TOPK(S32) contributes to sorafenib resistance in renal cell carcinoma; HGF/c-MET signaling activates p-TOPK(S32) during resistance.","method":"Phospho-specific antibody, Western blot, in vitro kinase assay, combination inhibitor studies","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phospho-specific antibody with kinase assay validation, single lab","pmids":["35546143"],"is_preprint":false},{"year":2022,"finding":"JAK2 directly binds and phosphorylates TOPK at Tyr74; this phosphorylation stabilizes TOPK and enhances phosphorylation of Histone H3 (a TOPK substrate) in Burkitt lymphoma cells, promoting tumor growth.","method":"Co-immunoprecipitation, in vitro kinase assay, in vivo/in vitro Histone H3 phosphorylation assay, xenograft model","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and in vitro kinase assay with functional downstream readout, single lab","pmids":["35780928"],"is_preprint":false},{"year":2023,"finding":"FYN (a non-receptor tyrosine kinase) directly binds TOPK and phosphorylates it at Tyr272; TOPK in turn phosphorylates HSPB1 at Ser15; the FYN-TOPK-HSPB1 cascade drives gastric cancer proliferation and metastasis.","method":"Co-IP, pulldown assay, 32P-labeled isotope radioautography kinase assay, in vitro kinase assay, phospho-specific antibodies, phosphoproteomics, TOPK knockout mice","journal":"Journal of experimental & clinical cancer research","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal methods including in vitro kinase assay, phosphoproteomics, knockout mice, and functional validation, single lab rigorous study","pmids":["37016377"],"is_preprint":false},{"year":2019,"finding":"TOPK promotes esophageal cancer through phosphorylation of YB1 at Thr89 and Ser209; phosphorylated YB1 binds the eEF1A1 promoter to activate its transcription, subsequently activating AKT/mTOR signaling.","method":"In vitro kinase assay with defined phosphosites, ChIP assay, Western blot, TOPK knockout with rescue, xenograft model","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — kinase assay with defined sites and ChIP, single lab","pmids":["37328464"],"is_preprint":false},{"year":2019,"finding":"TOPK is regulated by the E3 ubiquitin ligase/checkpoint protein CHFR (ubiquitination-mediated degradation); PP2A dephosphorylates TOPK (okadaic acid increases TOPK phosphorylation; FTY720/PP2A activator decreases it); BCR/ABL upregulates TOPK expression.","method":"Western blot with PP2A activator/inhibitor, BCR/ABL overexpression/imatinib inhibition, co-culture assays","journal":"International journal of oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological PP2A modulation with Western blot, single lab","pmids":["30864683"],"is_preprint":false},{"year":2015,"finding":"PBK/TOPK promotes geranylgeranylation-dependent breast cancer proliferation through YAP; YAP mediates geranylgeranylation-regulated PBK expression, placing PBK downstream of the Hippo-YAP signaling pathway.","method":"shRNA knockdown of YAP, HMG-CoA reductase inhibitor and GGTI-298 treatment, Western blot, proliferation assay","journal":"Cancer cell international","confidence":"Low","confidence_rationale":"Tier 3 / Weak — pharmacological inhibition with knockdown, no direct binding demonstration, single lab single set of methods","pmids":["25745361"],"is_preprint":false},{"year":2018,"finding":"TOPK is identified as a substrate of PRPK; TOPK phosphorylates PRPK, and knockdown of TOPK inhibits PRPK phosphorylation and reduces solar-simulated light-induced skin carcinogenesis in mouse models.","method":"In vivo/ex vivo phosphorylation analysis, TOPK knockdown in mouse skin cancer model, topical inhibitor treatment with carcinogenesis readout","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo TOPK knockdown with defined substrate phosphorylation readout and mouse carcinogenesis model, single lab","pmids":["29904102"],"is_preprint":false},{"year":2020,"finding":"TOPK directly binds and phosphorylates c-Jun at Ser63 and Ser73 after SSL (solar-simulated light) exposure in a JNK-independent manner, activating AP-1 transcriptional activity and promoting skin carcinogenesis.","method":"In vitro kinase assay, Co-IP, Western blot with phospho-specific antibodies, AP-1 luciferase reporter, siRNA knockdown, in vivo mouse carcinogenesis model","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay with defined phosphosites, Co-IP, and in vivo carcinogenesis model with defined phenotype, single lab multiple methods","pmids":["32277233"],"is_preprint":false},{"year":2005,"finding":"PBK transcription is regulated by E2F (at -146 bp) and CREB/ATF (at -312 bp) binding sites in the PBK promoter; knockdown of these transcription factors decreases PBK protein expression, and PBK is downregulated during doxorubicin-induced growth arrest.","method":"EMSA, siRNA knockdown of transcription factors, luciferase reporter assay","journal":"Leukemia research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — EMSA, siRNA, and reporter assay, single lab multiple methods","pmids":["16171862"],"is_preprint":false},{"year":2012,"finding":"c-Myc regulates PBK expression through E2F1; c-Myc–E2F1–PBK constitutes a signaling pathway in high-grade lymphomas, and inhibition of c-Myc, E2F1, or PBK comparably decreases cell growth and survival.","method":"siRNA knockdown of c-Myc and E2F1 with PBK protein/mRNA readout, correlation analysis, cell viability assay","journal":"Leukemia research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — knockdown with expression readout but no direct binding demonstrated, single lab","pmids":["23237560"],"is_preprint":false},{"year":2021,"finding":"Menin and HDAC3 are recruited by JunD to the Pbk promoter, reducing histone H3 acetylation and epigenetically repressing Pbk expression; menin inhibitor disrupts menin-JunD interaction and augments Pbk transcription, promoting beta cell proliferation in a Pbk-kinase-dependent manner.","method":"ChIP assay, Pbk kinase-dead knock-in mouse, menin inhibitor treatment, glucose tolerance assay","journal":"EMBO molecular medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — ChIP, genetic knock-in mouse model, and pharmacological intervention with metabolic readout, multiple orthogonal methods","pmids":["33821572"],"is_preprint":false},{"year":2020,"finding":"TOPK interacts directly with CHK1 and Cdc25c; TOPK depletion increases replication fork stalling and collapse under replication stress, impairs recovery from fork stalling, and increases replication-associated ssDNA foci, revealing a role for TOPK in S-phase checkpoint signaling.","method":"Co-immunoprecipitation, DNA fiber assay, immunofluorescence for ssDNA foci, siRNA knockdown, xenograft model","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with functional DNA replication assays, single lab","pmids":["33168956"],"is_preprint":false},{"year":2022,"finding":"PBK directly phosphorylates histone H3 (confirmed by in vitro kinase assay with recombinant PBK and H3); PBK failed to directly phosphorylate CDH1 in vitro, though it promotes CDH1 phosphorylation indirectly in cells.","method":"In vitro kinase assay with recombinant proteins, Western blot in colorectal cancer cells","journal":"Frontiers in pharmacology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution kinase assay establishing direct substrate, single lab","pmids":["35115926"],"is_preprint":false},{"year":2019,"finding":"EVI1 (ecotropic viral integration site-1) transcription factor directly targets the PBK promoter region and regulates PBK expression, placing PBK downstream of EVI1 in ovarian cancer; PBK promotes autophagy and cisplatin resistance via the ERK/mTOR signaling pathway.","method":"ChIP/promoter assay, ERK/mTOR Western blot, autophagy inhibitor rescue, in vivo xenograft","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — promoter ChIP and pharmacological pathway dissection with in vivo validation, single lab","pmids":["30778048"],"is_preprint":false},{"year":2019,"finding":"TOPK promotes invasion of ESCC cells by activating the Src/GSK3β/STAT3 and ERK signaling pathways via γ-catenin, identified by protein kinase array and mass spectrometry.","method":"Protein kinase array, mass spectrometry, immunofluorescence, Western blot, in vitro invasion assay, lung metastasis mouse model","journal":"BMC cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — kinase array and MS for pathway identification plus in vivo validation, single lab","pmids":["31888532"],"is_preprint":false}],"current_model":"PBK/TOPK is a MAPKK-like serine/threonine (and, when phosphorylated by upstream tyrosine kinases, also tyrosine-regulated) kinase that is activated during mitosis by CDK1/cyclin B phosphorylation at Thr-9 (and additional sites Thr-24, Ser-32, Ser-59), as well as by Src (Y74, Y272), JAK2 (Y74), MET (Y74), and ERK2 (S32); once active, TOPK phosphorylates multiple substrates including PRC1 (to promote cytokinesis), Histone H3 (Ser10), LGN/GPSM2 (Thr450), C2H2 zinc finger linkers (global chromatin dissociation during mitosis), p53 (suppressing its transactivation), MKP1 (stabilizing it to dampen p38 signaling), Prx1 (Ser-32, regulating peroxidase activity), IκBα (activating NF-κB), PTEN (inactivating it to activate Akt), ULK1 (Ser469/Ser495/Ser533, inhibiting autophagy), c-Jun (Ser63/Ser73, activating AP-1), PRPK, MSL1, HSPB1, YB1 (Thr89/Ser209), HDAC1/HDAC2, and TRIM37; its expression is transcriptionally driven by E2F, CREB/ATF, c-Myc/E2F1, EVI1, RORγ, and the menin/JunD/HDAC3 repressor complex, and it interacts with CHK1 and Cdc25c to support replication-stress checkpoint signaling."},"narrative":{"mechanistic_narrative":"PBK/TOPK is a MAPKK-like serine/threonine kinase that couples mitotic cell-cycle signaling to chromatin dynamics, cytokinesis, and oncogenic survival pathways [PMID:15541388, PMID:28780319]. During mitosis it is activated by CDK1/cyclin B phosphorylation at Thr-9 (and additional sites Thr-24, Ser-32, Ser-59), whereupon it associates with the mitotic spindle and is required for spindle midzone formation and cytokinesis [PMID:15541388, PMID:28780319]; mechanistically it complexes with CDK1/cyclin B1 and PRC1 on microtubules to enhance PRC1 phosphorylation [PMID:17512944], phosphorylates LGN/GPSM2 at Thr450 to ensure faithful chromosome segregation [PMID:20589935], directly phosphorylates Histone H3 [PMID:35115926], and serves as the master kinase that phosphorylates the conserved linker of C2H2 zinc-finger proteins to drive their global dissociation from condensing chromatin [PMID:25575812]. Beyond mitosis, TOPK functions as a node in stress and survival signaling: it phosphorylates the peroxiredoxin Prx1 (Ser-32) to enhance peroxidase activity and block UVB-induced apoptosis [PMID:20647304], stabilizes the p38-specific phosphatase MKP1 to restrain p38 and inflammation in vivo [PMID:21715333], and binds and suppresses p53 transactivation to license checkpoint bypass [PMID:20622899]. In cancer, TOPK is a hub that drives proliferation, invasion, and therapy resistance through substrates including c-Jun (Ser63/Ser73, activating AP-1) [PMID:32277233], ULK1 (Ser469/Ser495/Ser533, inhibiting autophagy) [PMID:31378785], and HSPB1 [PMID:37016377], and its kinase activity is itself amplified by upstream tyrosine kinases Src, JAK2, MET, and FYN that phosphorylate Tyr74/Tyr272 to stabilize the protein and enhance its catalytic output [PMID:27016416, PMID:35780928, PMID:37016377]. Pharmacologic TOPK inhibition phenocopies knockdown, producing cytokinesis failure and cancer-cell apoptosis [PMID:25338756]. PBK expression is transcriptionally controlled by E2F/CREB, c-Myc–E2F1, EVI1, and a menin/JunD/HDAC3 repressor complex [PMID:16171862, PMID:33821572], and the protein is degraded via CHFR-mediated ubiquitination and dephosphorylated by PP2A [PMID:24012691, PMID:30864683].","teleology":[{"year":2004,"claim":"Established TOPK as a mitotic effector by showing CDK1/cyclin B phosphorylates it at Thr-9 to target it to the spindle and drive cytokinesis, defining its core cell-cycle function.","evidence":"Immunofluorescence, kinase assay, and siRNA knockdown with cytokinesis readout","pmids":["15541388"],"confidence":"High","gaps":["Did not identify the spindle substrates downstream of TOPK","Activation mechanism beyond Thr-9 not resolved"]},{"year":2005,"claim":"Connected TOPK to p38 MAPK signaling and to transcriptional control, showing it phosphorylates p38 in cycling progenitors and that its own expression is driven by E2F and CREB/ATF.","evidence":"In vitro kinase assay, cell-cycle synchronization, transgenic ablation; EMSA and reporter assays for promoter elements","pmids":["16291951","16171862"],"confidence":"Medium","gaps":["Direct vs indirect p38 phosphorylation not fully separated","Promoter regulation tested in limited cell contexts"]},{"year":2007,"claim":"Defined the molecular partner and substrate of TOPK in cytokinesis, showing it complexes with CDK1/cyclin B1 and PRC1 and enhances PRC1 phosphorylation, and revealed a reciprocal feedback loop with ERK2.","evidence":"Reciprocal Co-IP, in vitro kinase assay, in vivo phosphorylation, knockdown/rescue","pmids":["17512944","17631144"],"confidence":"High","gaps":["Feedback loop with ERK2 from single lab","Stoichiometry of the CDK1/PRC1/TOPK complex not quantified"]},{"year":2010,"claim":"Expanded the TOPK substrate repertoire to chromosome segregation and redox/checkpoint control, identifying LGN/GPSM2-Thr450, Prx1-Ser32, and p53 binding as functional targets.","evidence":"In vitro kinase assays with defined phosphosites, CD spectroscopy, Co-IP/yeast two-hybrid, microarray with knockdown","pmids":["20589935","20647304","20622899"],"confidence":"High","gaps":["p53 interaction is binding-based suppression, not catalytic","In vivo relevance of Prx1-Ser32 across tissues unaddressed"]},{"year":2011,"claim":"Provided in vivo proof of TOPK's role in restraining inflammation by showing it phosphorylates and stabilizes MKP1 to dampen p38, with TOPK-knockout mice displaying UV-induced skin inflammation.","evidence":"In vitro kinase assay and TOPK knockout mouse with inflammation phenotype","pmids":["21715333"],"confidence":"High","gaps":["MKP1 phosphosite mapping not detailed","Reconciliation with TOPK-as-p38-activator findings unresolved"]},{"year":2015,"claim":"Identified TOPK as the master mitotic kinase for C2H2 zinc-finger linker regions, mechanistically linking it to global chromatin dissociation during mitosis, and demonstrated that kinase inhibition (OTS964) is sufficient to block cytokinesis therapeutically.","evidence":"Inhibitor panel and affinity purification with kinase validation; siRNA/inhibitor comparison with xenograft models","pmids":["25575812","25338756"],"confidence":"Medium","gaps":["ZFP linker phosphorylation shown globally but few individual ZFPs validated","Off-target profile of OTS964 not fully excluded"]},{"year":2016,"claim":"Established upstream tyrosine-kinase regulation of TOPK, showing Src phosphorylates Tyr74/Tyr272 to stabilize TOPK and enhance activity, and linked TOPK to TKI resistance via c-Jun/AP-1.","evidence":"In vitro kinase assays, phospho-specific antibodies, Src-knockout MEFs, pulse-chase; Co-IP and reporter assays for c-Jun axis","pmids":["27016416","26745678"],"confidence":"Medium","gaps":["Relative contribution of each Tyr site to stability vs activity not dissected","c-Jun phosphosites defined in a later study"]},{"year":2017,"claim":"Clarified the regulatory logic of mitotic phosphorylation, mapping CDK1 sites (Thr9/Thr24/Ser32/Ser59) and showing the non-phosphorylatable T9A mutant is more oncogenic, indicating mitotic phosphorylation inhibits TOPK's transforming activity.","evidence":"In vitro kinase assay, phosphosite mutagenesis, soft-agar and cytokinesis assays","pmids":["28780319"],"confidence":"High","gaps":["Mechanism by which Thr9 phosphorylation suppresses oncogenic output unresolved","Interplay with tyrosine phosphorylation not examined"]},{"year":2019,"claim":"Broadened TOPK's signaling reach to autophagy, transcription, and metastasis, identifying ULK1, YB1, and ETV4/uPAR axes and additional upstream inputs (MET, EVI1, PRPK, CHFR/PP2A regulation).","evidence":"Co-IP, in vitro kinase assays with defined phosphosites, ChIP, autophagy flux assays, xenograft and knockout models","pmids":["31378785","37328464","30914208","31611604","30778048","29904102","30864683","31888532"],"confidence":"Medium","gaps":["Many substrate/axis findings from single labs in specific cancer contexts","Hierarchy among the many parallel oncogenic outputs unclear"]},{"year":2020,"claim":"Established a JNK-independent route to AP-1 activation and a role in replication-stress checkpoint signaling, showing TOPK directly phosphorylates c-Jun Ser63/Ser73 and interacts with CHK1/Cdc25c to protect stalled forks.","evidence":"In vitro kinase assay with phosphosites, AP-1 reporter, in vivo carcinogenesis model; Co-IP, DNA fiber and ssDNA foci assays","pmids":["32277233","33168956"],"confidence":"High","gaps":["Whether CHK1/Cdc25c are TOPK substrates not established","Coordination of mitotic vs S-phase roles unaddressed"]},{"year":2021,"claim":"Connected TOPK to chromatin-acetylation machinery and refined its transcriptional repression, showing it phosphorylates MSL1 to promote MSL-complex/H4K16ac at CD276, while a menin/JunD/HDAC3 complex epigenetically represses Pbk in beta cells.","evidence":"Co-IP, kinase assay, ChIP, histone acetylation assay; ChIP and kinase-dead knock-in mouse with metabolic readout","pmids":["33431797","33821572"],"confidence":"Medium","gaps":["MSL1 phosphosite not mapped in detail","Generality of menin/JunD repression beyond beta cells untested"]},{"year":2022,"claim":"Consolidated the upstream tyrosine-kinase network and direct substrate set, confirming JAK2-Tyr74 stabilization, ERK2-Ser32 as a resistance site, TRIM37 phosphorylation, and direct Histone H3 phosphorylation by recombinant PBK.","evidence":"Co-IP, in vitro reconstitution kinase assays, phospho-specific antibodies, xenograft models","pmids":["35780928","35546143","35859118","35115926"],"confidence":"Medium","gaps":["Redundancy/specificity among Src, JAK2, MET, FYN inputs unresolved","CDH1 shown to be phosphorylated only indirectly"]},{"year":2023,"claim":"Defined a complete tyrosine-kinase-to-substrate cascade, showing FYN phosphorylates TOPK at Tyr272 and TOPK in turn phosphorylates HSPB1-Ser15 to drive gastric cancer, validated with knockout mice and phosphoproteomics.","evidence":"Co-IP, radioisotope and in vitro kinase assays, phosphoproteomics, TOPK knockout mice","pmids":["37016377"],"confidence":"High","gaps":["Tissue specificity of FYN-TOPK-HSPB1 vs other tyrosine-kinase inputs unclear","HSPB1-Ser15 downstream effectors not fully mapped"]},{"year":null,"claim":"How TOPK's many parallel substrate axes are prioritized and coordinated in space and time — reconciling its mitotic chromatin/cytokinesis roles with its diverse interphase oncogenic and stress-survival outputs — remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No integrated model ranking substrates by context","Structural basis of dual Ser/Thr and Tyr-regulated activation not defined","In vivo substrate hierarchy in normal vs tumor tissue unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,8,9,10,18,26,31,36]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,1,13,36]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[6,16,31]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[6,14,23]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0,1,13,14,35]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,11,16,31]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[18,37]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[6,8,17]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[14,22,36]}],"complexes":[],"partners":["CDK1","CCNB1","PRC1","TP53","SRC","JAK2","FYN","CHFR"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q96KB5","full_name":"Lymphokine-activated killer T-cell-originated protein kinase","aliases":["Cancer/testis antigen 84","CT84","MAPKK-like protein kinase","Nori-3","PDZ-binding kinase","Spermatogenesis-related protein kinase","SPK","T-LAK cell-originated protein kinase"],"length_aa":322,"mass_kda":36.1,"function":"Phosphorylates MAP kinase p38. 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the HIF-1α/snail axis.","date":"2020","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/33158479","citation_count":11,"is_preprint":false},{"pmid":"39090602","id":"PMC_39090602","title":"The oncogenic kinase TOPK upregulates in psoriatic keratinocytes and contributes to psoriasis progression by regulating neutrophils infiltration.","date":"2024","source":"Cell communication and signaling : CCS","url":"https://pubmed.ncbi.nlm.nih.gov/39090602","citation_count":10,"is_preprint":false},{"pmid":"30827262","id":"PMC_30827262","title":"Gossypetin Inhibits Solar-UV Induced Cutaneous Basal Cell Carcinoma Through Direct Inhibiting PBK/TOPK Protein Kinase.","date":"2019","source":"Anti-cancer agents in medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/30827262","citation_count":10,"is_preprint":false},{"pmid":"34859049","id":"PMC_34859049","title":"An Integrative Pan-Cancer Analysis of PBK in Human Tumors.","date":"2021","source":"Frontiers in molecular biosciences","url":"https://pubmed.ncbi.nlm.nih.gov/34859049","citation_count":10,"is_preprint":false},{"pmid":"30357568","id":"PMC_30357568","title":"[18F]FE-OTS964: a Small Molecule Targeting TOPK for In Vivo PET Imaging in a Glioblastoma Xenograft Model.","date":"2019","source":"Molecular imaging and biology","url":"https://pubmed.ncbi.nlm.nih.gov/30357568","citation_count":10,"is_preprint":false},{"pmid":"35780928","id":"PMC_35780928","title":"Phosphorylation of PBK/TOPK Tyr74 by JAK2 promotes Burkitt lymphoma tumor growth.","date":"2022","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/35780928","citation_count":9,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":51559,"output_tokens":8653,"usd":0.142236,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":18384,"output_tokens":5002,"usd":0.108485,"stage2_stop_reason":"end_turn"},"total_usd":0.250721,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2004,\n      \"finding\": \"TOPK is phosphorylated at Thr-9 by CDK1/cyclin B during mitosis, causing TOPK to associate with mitotic spindles; suppression of TOPK expression disrupts spindle midzone formation and cytokinesis.\",\n      \"method\": \"Immunofluorescence, Western blot, kinase assay, siRNA knockdown with phenotypic readout\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (kinase assay, immunofluorescence, functional knockdown), replicated in subsequent studies\",\n      \"pmids\": [\"15541388\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"TOPK forms a complex with CDK1/cyclin B1 and PRC1 on microtubules during mitosis; TOPK enhances CDK1/cyclin B1-dependent phosphorylation of PRC1 at T481 (requiring both TOPK enzymatic activity and physical association with PRC1), thereby promoting cytokinesis.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, in vivo phosphorylation analysis, functional overexpression/knockdown\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — reciprocal Co-IP, in vitro kinase assay, in vivo phosphorylation, and functional rescue, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"17512944\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"TOPK and ERK2 form a positive feedback loop: TOPK phosphorylates ERK2 and ERK2 phosphorylates TOPK; EGF-stimulated knockdown of either reduces phosphorylation of the other and blocks downstream ERK2 substrate phosphorylation.\",\n      \"method\": \"In vitro kinase assay, siRNA knockdown, transient transfection, Western blot in HCT116 cells\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro kinase assay plus reciprocal knockdown experiments, single lab\",\n      \"pmids\": [\"17631144\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"PBK/TOPK is necessary for appropriate p38 MAPK activation by growth factors; PBK knockdown impairs p38 activation, reduces cell motility, and results in an impaired DNA damage response (decreased γ-H2AX generation, increased DNA damage).\",\n      \"method\": \"siRNA knockdown, Western blot, clonogenic assay, motility assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA knockdown with multiple defined phenotypic readouts, single lab\",\n      \"pmids\": [\"17160018\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PBK/TOPK phosphorylates p38 MAPK and is activated in a cell-cycle-dependent manner in neural progenitor cells; inhibition of this pathway disrupts progenitor proliferation and self-renewal.\",\n      \"method\": \"In vitro kinase assay, cell-cycle synchronization, transgenic ablation with lineage tracing in mice\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro kinase assay and in vivo genetic ablation, single lab, multiple methods\",\n      \"pmids\": [\"16291951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"TOPK-Thr-9 is specifically phosphorylated by CDK1/cyclin B during both mitotic and meiotic phases in spermatogenic cells, implicating TOPK in cytokinesis and/or chromosomal segregation during spermatogenesis.\",\n      \"method\": \"Immunohistochemistry, Western blot with phospho-specific antibodies on testis sections\",\n      \"journal\": \"Development, growth & differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phospho-specific antibody analysis in defined cell-cycle stages, single lab\",\n      \"pmids\": [\"16316408\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"TOPK physically interacts with the DNA-binding domain of p53 (including five common point mutants); PBK/TOPK knockdown upregulates p53 target genes (p21, apoptotic genes) particularly after genotoxic damage, indicating PBK suppresses p53 transactivation function.\",\n      \"method\": \"Co-immunoprecipitation, yeast two-hybrid, gene microarray, siRNA knockdown with qPCR/Western blot readouts in HCT116 and MCF-7 cells\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP plus yeast two-hybrid plus functional knockdown with transcriptional readouts, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"20622899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PBK physically interacts with p53 (detected by Co-IP and yeast two-hybrid) and downregulates p53, enabling cells to bypass DNA damage checkpoint; a phosphomimetic PBK mutant promotes polyploidization and aberrant mitotic entry after doxorubicin treatment.\",\n      \"method\": \"Co-immunoprecipitation, yeast two-hybrid, ectopic overexpression with flow cytometry (MPM-2 marker)\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and yeast two-hybrid with functional overexpression readout, single lab\",\n      \"pmids\": [\"17482142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"TOPK binds Prx1 and phosphorylates it at Ser-32; this phosphorylation alters the secondary structure of Prx1 and enhances its peroxidase activity, blocking UVB-induced H2O2 accumulation and apoptosis in melanoma cells.\",\n      \"method\": \"LC-MS/MS pulldown identification, in vitro kinase assay, CD spectroscopy of Prx1/S32A mutant, flow cytometry, stable siRNA knockdown\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay, structural (CD spectra), and functional mutant analysis in single lab with multiple orthogonal approaches\",\n      \"pmids\": [\"20647304\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TOPK negatively regulates p38α activity by phosphorylating the p38α-specific phosphatase MKP1 and enhancing MKP1 stability; TOPK-knockout mice display markedly increased skin inflammation after solar UV irradiation.\",\n      \"method\": \"In vitro kinase assay, Western blot, TOPK knockout mouse model with inflammation phenotype\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vitro kinase assay plus knockout mouse with defined phenotype, replicated mechanistically\",\n      \"pmids\": [\"21715333\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PBK/TOPK phosphorylates LGN/GPSM2 at Thr450 during mitosis; overexpression of non-phosphorylatable LGN/GPSM2-T450A causes aberrant chromosomal segregation and growth suppression in breast cancer cells.\",\n      \"method\": \"In vitro kinase assay, Western blot with phospho-specific analysis, siRNA knockdown, mutant overexpression with phenotypic readout\",\n      \"journal\": \"Genes, chromosomes & cancer\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro kinase assay with defined phosphosite plus functional phospho-mutant rescue, single lab multiple methods\",\n      \"pmids\": [\"20589935\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"TOPK/PBK is ubiquitinated and targeted for degradation by the E3 ubiquitin ligase CHFR; TOPK in turn phosphorylates and inactivates PTEN, which activates Akt, facilitating G2/M progression in a CHFR-mediated mitotic checkpoint pathway.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, in vitro kinase assay, siRNA knockdown with cell-cycle readout\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, ubiquitination assay, and kinase assay in single lab, multiple methods\",\n      \"pmids\": [\"24012691\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Src directly binds and phosphorylates TOPK at Tyr74 and Tyr272; these phosphorylations increase TOPK stability by inhibiting its ubiquitination and enhance TOPK kinase activity (measured by Histone H3-Ser10 phosphorylation); TOPK-Y74F/Y272F double mutant displays reduced tumorigenic activity.\",\n      \"method\": \"In vitro kinase assay with recombinant proteins, phospho-specific antibody generation, stable transfection with mutants, Co-IP, pulse-chase protein stability assay, Src-knockout MEFs\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro kinase assay, phospho-specific antibody, genetic knockout cells, pulse-chase stability, and in vivo tumorigenesis, single lab multiple orthogonal methods\",\n      \"pmids\": [\"27016416\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"CDK1 phosphorylates PBK at Thr-9 (and also Thr-24, Ser-32, Ser-59) during mitosis; Thr-9 phosphorylation is required for normal cytokinesis; non-phosphorylatable PBK-T9A augments tumorigenesis more than wild-type PBK, indicating mitotic phosphorylation inhibits PBK's oncogenic activity.\",\n      \"method\": \"In vitro kinase assay, phospho-site mutagenesis, stable cell lines, soft agar assay, immunofluorescence cytokinesis analysis\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay with defined phosphosites plus functional mutagenesis in oncogenesis assays, single lab multiple methods\",\n      \"pmids\": [\"28780319\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TOPK/PBK is the master kinase responsible for phosphorylating the conserved linker region of C2H2 zinc finger proteins (ZFPs) during mitosis, causing their dissociation from condensing chromatin; TOPK is activated by CDK1 and acts as the global ZFP linker kinase.\",\n      \"method\": \"Kinase inhibitor panel screen, biotinylated K252a affinity purification, in vitro kinase assay, in vivo phosphorylation correlation\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — affinity purification followed by in vitro and in vivo validation, single lab\",\n      \"pmids\": [\"25575812\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TOPK inhibition with OTS964 causes cytokinesis defects and subsequent apoptosis of cancer cells, similar to siRNA knockdown; TOPK kinase inhibition (not just expression loss) is sufficient to block cytokinesis.\",\n      \"method\": \"In vitro kinase assay, siRNA comparison, xenograft tumor models, liposomal drug formulation\",\n      \"journal\": \"Science translational medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — defined mechanism (cytokinesis defect) confirmed by both siRNA and inhibitor, replicated in vivo, rigorous controls\",\n      \"pmids\": [\"25338756\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"TOPK promotes lung cancer resistance to EGFR-TKIs by directly binding and phosphorylating c-Jun, which activates AP-1 target genes CCND1 and CDC2; TOPK silencing sensitizes TKI-resistant cells to gefitinib.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, luciferase reporter, siRNA knockdown with drug-sensitivity assay, xenograft model\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and in vitro kinase assay with functional readouts, single lab\",\n      \"pmids\": [\"26745678\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MET phosphorylates TOPK at Tyr74, preventing apoptosis in gefitinib-resistant NSCLC cells; this is part of the COX2-TXA2-MET-TOPK axis.\",\n      \"method\": \"Western blot with phospho-specific antibodies, in vitro signaling analysis, inhibitor combination studies in vitro and in vivo\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phospho-specific detection, pathway inhibitor validation, single lab\",\n      \"pmids\": [\"31611604\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TOPK directly binds and phosphorylates ULK1 at Ser469, Ser495, and Ser533, decreasing ULK1 activity and stability and thereby inhibiting autophagy initiation in glioma cells.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay with identified phosphosites, Western blot, autophagy flux assay\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay with defined phosphosites, Co-IP, and functional autophagy readout in single lab with multiple methods\",\n      \"pmids\": [\"31378785\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TOPK promotes microglia/macrophage M2 polarization by binding to HDAC1 and HDAC2 and promoting their phosphorylation, inhibiting their deacetylase activity; this contributes to neuroprotection after cerebral ischemia.\",\n      \"method\": \"Co-immunoprecipitation (in vivo binding), in vitro TOPK overexpression in BV2 cells, immunofluorescence co-localization, Western blot\",\n      \"journal\": \"Aging and disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with co-localization and functional overexpression readout, single lab\",\n      \"pmids\": [\"29896413\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TOPK activates NF-κB by interacting with and phosphorylating IκBα in response to LPS, promoting iNOS transcription and nitric oxide production in leukemia cells.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay against IκBα, NF-κB/iNOS promoter-driven luciferase assay, siRNA knockdown\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, in vitro kinase assay, and promoter reporter, single lab\",\n      \"pmids\": [\"24440499\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PBK promotes HCC metastasis via the ETV4-uPAR signaling pathway: PBK enhances binding of ETV4 to the uPAR promoter (shown by ChIP assay), activating uPAR transcription; uPAR overexpression rescues PBK-knockdown metastatic phenotype in vivo.\",\n      \"method\": \"ChIP assay, promoter reporter assay, gain/loss-of-function in vitro migration/invasion, orthotopic mouse model\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP assay and in vivo rescue experiment, single lab\",\n      \"pmids\": [\"30914208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PBK phosphorylates MSL1, enhancing MSL1 interaction with MSL2, MSL3, and KAT8 (MSL complex components), promoting MSL complex enrichment on the CD276 promoter, increasing histone H4 K16 acetylation and CD276 transcription in nasopharyngeal carcinoma.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, ChIP assay, histone acetylation assay\",\n      \"journal\": \"Oncogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — kinase assay, Co-IP, and ChIP, single lab with multiple methods\",\n      \"pmids\": [\"33431797\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PBK directly interacts with TRIM37 and promotes its phosphorylation and nuclear translocation, activating the NFκB pathway and conferring PARPi resistance in ovarian cancer.\",\n      \"method\": \"Co-immunoprecipitation, Western blot for nuclear translocation, NF-κB pathway analysis, in vitro and in vivo drug resistance assays\",\n      \"journal\": \"Experimental & molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with functional in vitro and in vivo validation, single lab\",\n      \"pmids\": [\"35859118\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ERK2 phosphorylates TOPK at Ser32 (a novel site beyond the previously known Thr9), and p-TOPK(S32) contributes to sorafenib resistance in renal cell carcinoma; HGF/c-MET signaling activates p-TOPK(S32) during resistance.\",\n      \"method\": \"Phospho-specific antibody, Western blot, in vitro kinase assay, combination inhibitor studies\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phospho-specific antibody with kinase assay validation, single lab\",\n      \"pmids\": [\"35546143\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"JAK2 directly binds and phosphorylates TOPK at Tyr74; this phosphorylation stabilizes TOPK and enhances phosphorylation of Histone H3 (a TOPK substrate) in Burkitt lymphoma cells, promoting tumor growth.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, in vivo/in vitro Histone H3 phosphorylation assay, xenograft model\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and in vitro kinase assay with functional downstream readout, single lab\",\n      \"pmids\": [\"35780928\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"FYN (a non-receptor tyrosine kinase) directly binds TOPK and phosphorylates it at Tyr272; TOPK in turn phosphorylates HSPB1 at Ser15; the FYN-TOPK-HSPB1 cascade drives gastric cancer proliferation and metastasis.\",\n      \"method\": \"Co-IP, pulldown assay, 32P-labeled isotope radioautography kinase assay, in vitro kinase assay, phospho-specific antibodies, phosphoproteomics, TOPK knockout mice\",\n      \"journal\": \"Journal of experimental & clinical cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal methods including in vitro kinase assay, phosphoproteomics, knockout mice, and functional validation, single lab rigorous study\",\n      \"pmids\": [\"37016377\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TOPK promotes esophageal cancer through phosphorylation of YB1 at Thr89 and Ser209; phosphorylated YB1 binds the eEF1A1 promoter to activate its transcription, subsequently activating AKT/mTOR signaling.\",\n      \"method\": \"In vitro kinase assay with defined phosphosites, ChIP assay, Western blot, TOPK knockout with rescue, xenograft model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — kinase assay with defined sites and ChIP, single lab\",\n      \"pmids\": [\"37328464\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TOPK is regulated by the E3 ubiquitin ligase/checkpoint protein CHFR (ubiquitination-mediated degradation); PP2A dephosphorylates TOPK (okadaic acid increases TOPK phosphorylation; FTY720/PP2A activator decreases it); BCR/ABL upregulates TOPK expression.\",\n      \"method\": \"Western blot with PP2A activator/inhibitor, BCR/ABL overexpression/imatinib inhibition, co-culture assays\",\n      \"journal\": \"International journal of oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological PP2A modulation with Western blot, single lab\",\n      \"pmids\": [\"30864683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PBK/TOPK promotes geranylgeranylation-dependent breast cancer proliferation through YAP; YAP mediates geranylgeranylation-regulated PBK expression, placing PBK downstream of the Hippo-YAP signaling pathway.\",\n      \"method\": \"shRNA knockdown of YAP, HMG-CoA reductase inhibitor and GGTI-298 treatment, Western blot, proliferation assay\",\n      \"journal\": \"Cancer cell international\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — pharmacological inhibition with knockdown, no direct binding demonstration, single lab single set of methods\",\n      \"pmids\": [\"25745361\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TOPK is identified as a substrate of PRPK; TOPK phosphorylates PRPK, and knockdown of TOPK inhibits PRPK phosphorylation and reduces solar-simulated light-induced skin carcinogenesis in mouse models.\",\n      \"method\": \"In vivo/ex vivo phosphorylation analysis, TOPK knockdown in mouse skin cancer model, topical inhibitor treatment with carcinogenesis readout\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo TOPK knockdown with defined substrate phosphorylation readout and mouse carcinogenesis model, single lab\",\n      \"pmids\": [\"29904102\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TOPK directly binds and phosphorylates c-Jun at Ser63 and Ser73 after SSL (solar-simulated light) exposure in a JNK-independent manner, activating AP-1 transcriptional activity and promoting skin carcinogenesis.\",\n      \"method\": \"In vitro kinase assay, Co-IP, Western blot with phospho-specific antibodies, AP-1 luciferase reporter, siRNA knockdown, in vivo mouse carcinogenesis model\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay with defined phosphosites, Co-IP, and in vivo carcinogenesis model with defined phenotype, single lab multiple methods\",\n      \"pmids\": [\"32277233\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PBK transcription is regulated by E2F (at -146 bp) and CREB/ATF (at -312 bp) binding sites in the PBK promoter; knockdown of these transcription factors decreases PBK protein expression, and PBK is downregulated during doxorubicin-induced growth arrest.\",\n      \"method\": \"EMSA, siRNA knockdown of transcription factors, luciferase reporter assay\",\n      \"journal\": \"Leukemia research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — EMSA, siRNA, and reporter assay, single lab multiple methods\",\n      \"pmids\": [\"16171862\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"c-Myc regulates PBK expression through E2F1; c-Myc–E2F1–PBK constitutes a signaling pathway in high-grade lymphomas, and inhibition of c-Myc, E2F1, or PBK comparably decreases cell growth and survival.\",\n      \"method\": \"siRNA knockdown of c-Myc and E2F1 with PBK protein/mRNA readout, correlation analysis, cell viability assay\",\n      \"journal\": \"Leukemia research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — knockdown with expression readout but no direct binding demonstrated, single lab\",\n      \"pmids\": [\"23237560\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Menin and HDAC3 are recruited by JunD to the Pbk promoter, reducing histone H3 acetylation and epigenetically repressing Pbk expression; menin inhibitor disrupts menin-JunD interaction and augments Pbk transcription, promoting beta cell proliferation in a Pbk-kinase-dependent manner.\",\n      \"method\": \"ChIP assay, Pbk kinase-dead knock-in mouse, menin inhibitor treatment, glucose tolerance assay\",\n      \"journal\": \"EMBO molecular medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — ChIP, genetic knock-in mouse model, and pharmacological intervention with metabolic readout, multiple orthogonal methods\",\n      \"pmids\": [\"33821572\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TOPK interacts directly with CHK1 and Cdc25c; TOPK depletion increases replication fork stalling and collapse under replication stress, impairs recovery from fork stalling, and increases replication-associated ssDNA foci, revealing a role for TOPK in S-phase checkpoint signaling.\",\n      \"method\": \"Co-immunoprecipitation, DNA fiber assay, immunofluorescence for ssDNA foci, siRNA knockdown, xenograft model\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with functional DNA replication assays, single lab\",\n      \"pmids\": [\"33168956\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PBK directly phosphorylates histone H3 (confirmed by in vitro kinase assay with recombinant PBK and H3); PBK failed to directly phosphorylate CDH1 in vitro, though it promotes CDH1 phosphorylation indirectly in cells.\",\n      \"method\": \"In vitro kinase assay with recombinant proteins, Western blot in colorectal cancer cells\",\n      \"journal\": \"Frontiers in pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution kinase assay establishing direct substrate, single lab\",\n      \"pmids\": [\"35115926\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"EVI1 (ecotropic viral integration site-1) transcription factor directly targets the PBK promoter region and regulates PBK expression, placing PBK downstream of EVI1 in ovarian cancer; PBK promotes autophagy and cisplatin resistance via the ERK/mTOR signaling pathway.\",\n      \"method\": \"ChIP/promoter assay, ERK/mTOR Western blot, autophagy inhibitor rescue, in vivo xenograft\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — promoter ChIP and pharmacological pathway dissection with in vivo validation, single lab\",\n      \"pmids\": [\"30778048\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TOPK promotes invasion of ESCC cells by activating the Src/GSK3β/STAT3 and ERK signaling pathways via γ-catenin, identified by protein kinase array and mass spectrometry.\",\n      \"method\": \"Protein kinase array, mass spectrometry, immunofluorescence, Western blot, in vitro invasion assay, lung metastasis mouse model\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — kinase array and MS for pathway identification plus in vivo validation, single lab\",\n      \"pmids\": [\"31888532\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PBK/TOPK is a MAPKK-like serine/threonine (and, when phosphorylated by upstream tyrosine kinases, also tyrosine-regulated) kinase that is activated during mitosis by CDK1/cyclin B phosphorylation at Thr-9 (and additional sites Thr-24, Ser-32, Ser-59), as well as by Src (Y74, Y272), JAK2 (Y74), MET (Y74), and ERK2 (S32); once active, TOPK phosphorylates multiple substrates including PRC1 (to promote cytokinesis), Histone H3 (Ser10), LGN/GPSM2 (Thr450), C2H2 zinc finger linkers (global chromatin dissociation during mitosis), p53 (suppressing its transactivation), MKP1 (stabilizing it to dampen p38 signaling), Prx1 (Ser-32, regulating peroxidase activity), IκBα (activating NF-κB), PTEN (inactivating it to activate Akt), ULK1 (Ser469/Ser495/Ser533, inhibiting autophagy), c-Jun (Ser63/Ser73, activating AP-1), PRPK, MSL1, HSPB1, YB1 (Thr89/Ser209), HDAC1/HDAC2, and TRIM37; its expression is transcriptionally driven by E2F, CREB/ATF, c-Myc/E2F1, EVI1, RORγ, and the menin/JunD/HDAC3 repressor complex, and it interacts with CHK1 and Cdc25c to support replication-stress checkpoint signaling.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PBK/TOPK is a MAPKK-like serine/threonine kinase that couples mitotic cell-cycle signaling to chromatin dynamics, cytokinesis, and oncogenic survival pathways [#0, #13]. During mitosis it is activated by CDK1/cyclin B phosphorylation at Thr-9 (and additional sites Thr-24, Ser-32, Ser-59), whereupon it associates with the mitotic spindle and is required for spindle midzone formation and cytokinesis [#0, #13]; mechanistically it complexes with CDK1/cyclin B1 and PRC1 on microtubules to enhance PRC1 phosphorylation [#1], phosphorylates LGN/GPSM2 at Thr450 to ensure faithful chromosome segregation [#10], directly phosphorylates Histone H3 [#36], and serves as the master kinase that phosphorylates the conserved linker of C2H2 zinc-finger proteins to drive their global dissociation from condensing chromatin [#14]. Beyond mitosis, TOPK functions as a node in stress and survival signaling: it phosphorylates the peroxiredoxin Prx1 (Ser-32) to enhance peroxidase activity and block UVB-induced apoptosis [#8], stabilizes the p38-specific phosphatase MKP1 to restrain p38 and inflammation in vivo [#9], and binds and suppresses p53 transactivation to license checkpoint bypass [#6]. In cancer, TOPK is a hub that drives proliferation, invasion, and therapy resistance through substrates including c-Jun (Ser63/Ser73, activating AP-1) [#31], ULK1 (Ser469/Ser495/Ser533, inhibiting autophagy) [#18], and HSPB1 [#26], and its kinase activity is itself amplified by upstream tyrosine kinases Src, JAK2, MET, and FYN that phosphorylate Tyr74/Tyr272 to stabilize the protein and enhance its catalytic output [#12, #25, #26]. Pharmacologic TOPK inhibition phenocopies knockdown, producing cytokinesis failure and cancer-cell apoptosis [#15]. PBK expression is transcriptionally controlled by E2F/CREB, c-Myc–E2F1, EVI1, and a menin/JunD/HDAC3 repressor complex [#32, #34], and the protein is degraded via CHFR-mediated ubiquitination and dephosphorylated by PP2A [#11, #28].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Established TOPK as a mitotic effector by showing CDK1/cyclin B phosphorylates it at Thr-9 to target it to the spindle and drive cytokinesis, defining its core cell-cycle function.\",\n      \"evidence\": \"Immunofluorescence, kinase assay, and siRNA knockdown with cytokinesis readout\",\n      \"pmids\": [\"15541388\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the spindle substrates downstream of TOPK\", \"Activation mechanism beyond Thr-9 not resolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Connected TOPK to p38 MAPK signaling and to transcriptional control, showing it phosphorylates p38 in cycling progenitors and that its own expression is driven by E2F and CREB/ATF.\",\n      \"evidence\": \"In vitro kinase assay, cell-cycle synchronization, transgenic ablation; EMSA and reporter assays for promoter elements\",\n      \"pmids\": [\"16291951\", \"16171862\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs indirect p38 phosphorylation not fully separated\", \"Promoter regulation tested in limited cell contexts\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined the molecular partner and substrate of TOPK in cytokinesis, showing it complexes with CDK1/cyclin B1 and PRC1 and enhances PRC1 phosphorylation, and revealed a reciprocal feedback loop with ERK2.\",\n      \"evidence\": \"Reciprocal Co-IP, in vitro kinase assay, in vivo phosphorylation, knockdown/rescue\",\n      \"pmids\": [\"17512944\", \"17631144\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Feedback loop with ERK2 from single lab\", \"Stoichiometry of the CDK1/PRC1/TOPK complex not quantified\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Expanded the TOPK substrate repertoire to chromosome segregation and redox/checkpoint control, identifying LGN/GPSM2-Thr450, Prx1-Ser32, and p53 binding as functional targets.\",\n      \"evidence\": \"In vitro kinase assays with defined phosphosites, CD spectroscopy, Co-IP/yeast two-hybrid, microarray with knockdown\",\n      \"pmids\": [\"20589935\", \"20647304\", \"20622899\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"p53 interaction is binding-based suppression, not catalytic\", \"In vivo relevance of Prx1-Ser32 across tissues unaddressed\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Provided in vivo proof of TOPK's role in restraining inflammation by showing it phosphorylates and stabilizes MKP1 to dampen p38, with TOPK-knockout mice displaying UV-induced skin inflammation.\",\n      \"evidence\": \"In vitro kinase assay and TOPK knockout mouse with inflammation phenotype\",\n      \"pmids\": [\"21715333\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"MKP1 phosphosite mapping not detailed\", \"Reconciliation with TOPK-as-p38-activator findings unresolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identified TOPK as the master mitotic kinase for C2H2 zinc-finger linker regions, mechanistically linking it to global chromatin dissociation during mitosis, and demonstrated that kinase inhibition (OTS964) is sufficient to block cytokinesis therapeutically.\",\n      \"evidence\": \"Inhibitor panel and affinity purification with kinase validation; siRNA/inhibitor comparison with xenograft models\",\n      \"pmids\": [\"25575812\", \"25338756\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"ZFP linker phosphorylation shown globally but few individual ZFPs validated\", \"Off-target profile of OTS964 not fully excluded\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Established upstream tyrosine-kinase regulation of TOPK, showing Src phosphorylates Tyr74/Tyr272 to stabilize TOPK and enhance activity, and linked TOPK to TKI resistance via c-Jun/AP-1.\",\n      \"evidence\": \"In vitro kinase assays, phospho-specific antibodies, Src-knockout MEFs, pulse-chase; Co-IP and reporter assays for c-Jun axis\",\n      \"pmids\": [\"27016416\", \"26745678\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative contribution of each Tyr site to stability vs activity not dissected\", \"c-Jun phosphosites defined in a later study\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Clarified the regulatory logic of mitotic phosphorylation, mapping CDK1 sites (Thr9/Thr24/Ser32/Ser59) and showing the non-phosphorylatable T9A mutant is more oncogenic, indicating mitotic phosphorylation inhibits TOPK's transforming activity.\",\n      \"evidence\": \"In vitro kinase assay, phosphosite mutagenesis, soft-agar and cytokinesis assays\",\n      \"pmids\": [\"28780319\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which Thr9 phosphorylation suppresses oncogenic output unresolved\", \"Interplay with tyrosine phosphorylation not examined\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Broadened TOPK's signaling reach to autophagy, transcription, and metastasis, identifying ULK1, YB1, and ETV4/uPAR axes and additional upstream inputs (MET, EVI1, PRPK, CHFR/PP2A regulation).\",\n      \"evidence\": \"Co-IP, in vitro kinase assays with defined phosphosites, ChIP, autophagy flux assays, xenograft and knockout models\",\n      \"pmids\": [\"31378785\", \"37328464\", \"30914208\", \"31611604\", \"30778048\", \"29904102\", \"30864683\", \"31888532\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Many substrate/axis findings from single labs in specific cancer contexts\", \"Hierarchy among the many parallel oncogenic outputs unclear\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Established a JNK-independent route to AP-1 activation and a role in replication-stress checkpoint signaling, showing TOPK directly phosphorylates c-Jun Ser63/Ser73 and interacts with CHK1/Cdc25c to protect stalled forks.\",\n      \"evidence\": \"In vitro kinase assay with phosphosites, AP-1 reporter, in vivo carcinogenesis model; Co-IP, DNA fiber and ssDNA foci assays\",\n      \"pmids\": [\"32277233\", \"33168956\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CHK1/Cdc25c are TOPK substrates not established\", \"Coordination of mitotic vs S-phase roles unaddressed\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Connected TOPK to chromatin-acetylation machinery and refined its transcriptional repression, showing it phosphorylates MSL1 to promote MSL-complex/H4K16ac at CD276, while a menin/JunD/HDAC3 complex epigenetically represses Pbk in beta cells.\",\n      \"evidence\": \"Co-IP, kinase assay, ChIP, histone acetylation assay; ChIP and kinase-dead knock-in mouse with metabolic readout\",\n      \"pmids\": [\"33431797\", \"33821572\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"MSL1 phosphosite not mapped in detail\", \"Generality of menin/JunD repression beyond beta cells untested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Consolidated the upstream tyrosine-kinase network and direct substrate set, confirming JAK2-Tyr74 stabilization, ERK2-Ser32 as a resistance site, TRIM37 phosphorylation, and direct Histone H3 phosphorylation by recombinant PBK.\",\n      \"evidence\": \"Co-IP, in vitro reconstitution kinase assays, phospho-specific antibodies, xenograft models\",\n      \"pmids\": [\"35780928\", \"35546143\", \"35859118\", \"35115926\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Redundancy/specificity among Src, JAK2, MET, FYN inputs unresolved\", \"CDH1 shown to be phosphorylated only indirectly\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined a complete tyrosine-kinase-to-substrate cascade, showing FYN phosphorylates TOPK at Tyr272 and TOPK in turn phosphorylates HSPB1-Ser15 to drive gastric cancer, validated with knockout mice and phosphoproteomics.\",\n      \"evidence\": \"Co-IP, radioisotope and in vitro kinase assays, phosphoproteomics, TOPK knockout mice\",\n      \"pmids\": [\"37016377\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tissue specificity of FYN-TOPK-HSPB1 vs other tyrosine-kinase inputs unclear\", \"HSPB1-Ser15 downstream effectors not fully mapped\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How TOPK's many parallel substrate axes are prioritized and coordinated in space and time — reconciling its mitotic chromatin/cytokinesis roles with its diverse interphase oncogenic and stress-survival outputs — remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No integrated model ranking substrates by context\", \"Structural basis of dual Ser/Thr and Tyr-regulated activation not defined\", \"In vivo substrate hierarchy in normal vs tumor tissue unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 8, 9, 10, 18, 26, 31, 36]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 1, 13, 36]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [6, 16, 31]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005819\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [6, 14, 23]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0, 1, 13, 14, 35]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 11, 16, 31]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [18, 37]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [6, 8, 17]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [14, 22, 36]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CDK1\", \"CCNB1\", \"PRC1\", \"TP53\", \"SRC\", \"JAK2\", \"FYN\", \"CHFR\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}