{"gene":"TTK","run_date":"2026-06-10T10:51:56","timeline":{"discoveries":[{"year":1992,"finding":"TTK is a dual-specificity kinase capable of phosphorylating serine, threonine, and tyrosine residues; when the kinase domain was expressed in E. coli, elevated phosphoserine and phosphothreonine (and slightly elevated phosphotyrosine) were detected, establishing its catalytic activity.","method":"Expression of kinase domain in E. coli with phosphoamino acid analysis","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — direct in vitro enzymatic activity demonstrated, but single lab, single method, no mutagenesis validation","pmids":["1639825"],"is_preprint":false},{"year":1994,"finding":"TTK mRNA, protein, and kinase activity peak at G2/M phase of the cell cycle; levels are very low in starved/G1 cells and rise upon S-phase entry, establishing cell-cycle-dependent regulation of TTK.","method":"Cell synchronization, mRNA/protein quantification, kinase activity assays across cell cycle stages","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (mRNA, protein, kinase activity) in synchronized cells, single lab","pmids":["8302607"],"is_preprint":false},{"year":1998,"finding":"Fission yeast Mph1 (MPS1 homolog) functions upstream of Mad2 in the spindle assembly checkpoint; overexpression of mph1 mimics checkpoint activation and imposes metaphase arrest, while mph1 is required for checkpoint activation in response to spindle defects. Genetic epistasis places mph1 upstream of mad2.","method":"Genetic epistasis, overexpression, complementation analysis in S. pombe","journal":"Journal of Cell Science","confidence":"High","confidence_rationale":"Tier 2 / Strong — epistasis confirmed by multiple genetic approaches, replicated in subsequent studies","pmids":["9601094"],"is_preprint":false},{"year":2003,"finding":"TTK localizes dynamically during mitosis in HeLa cells: at nuclear pore-adjacent complex in interphase, then to corona fibers of unattached kinetochores (extending ~90 nm from the outer plate), and migrates to centrosomes upon metaphase alignment, supporting a role in spindle checkpoint signaling at both kinetochore and centrosome.","method":"Immunoelectron microscopy of HeLa cells","journal":"Cell Research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct ultrastructural localization, single lab, single method","pmids":["14728800"],"is_preprint":false},{"year":2004,"finding":"TTK/hMps1 directly phosphorylates CHK2 at Thr-68 in vitro; expression of a kinase-dead TTK(D647A) mutant impairs G2/M arrest and CHK2 Thr-68 phosphorylation after DNA damage; siRNA depletion of TTK reduces CHK2 Thr-68 phosphorylation and impairs growth arrest, placing TTK upstream of CHK2 in the DNA damage checkpoint.","method":"In vitro kinase assay, kinase-dead mutant expression, siRNA knockdown, cell cycle analysis","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro phosphorylation assay plus kinase-dead mutant and siRNA knockdown with defined phenotypic readout, single lab with multiple orthogonal methods","pmids":["15618221"],"is_preprint":false},{"year":2004,"finding":"TTK kinase activity is required for centrosomal localization of TACC2; TACC2 is pulled down by wild-type TTK but not kinase-dead TTK; expression of kinase-dead TTK or TTK depletion eliminates centrosomal TACC2, causing chromosome misalignment and reduced centrosome separation.","method":"Co-immunoprecipitation/pulldown with kinase-dead mutant, immunofluorescence, TTK knockdown","journal":"FEBS Letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP with kinase-dead mutant and localization with functional consequence, single lab","pmids":["15304323"],"is_preprint":false},{"year":2008,"finding":"TTK phosphorylates c-Abl at Thr735 (identified by expression cloning with a phosphospecific antibody); this phosphorylation promotes 14-3-3 binding to c-Abl, sequestering it in the cytoplasm; TTK knockdown abolishes oxidative stress-induced Thr735 phosphorylation and causes constitutive nuclear accumulation of c-Abl, enhancing apoptosis.","method":"Expression cloning, in vitro kinase assay, phosphospecific antibody, siRNA knockdown, subcellular fractionation/localization","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1 / Moderate — expression cloning with phosphospecific readout, in vitro kinase assay, siRNA validation, functional consequence established, single lab with multiple orthogonal methods","pmids":["18794806"],"is_preprint":false},{"year":2009,"finding":"TTK/hMps1 phosphorylates p53 at Thr18 in vitro, disrupting the p53-MDM2 interaction and abrogating MDM2-mediated p53 ubiquitination; this phosphorylation stabilizes p53 and activates p21 and Lats2 after spindle disruption; phospho-mimetic T18D rescues tetraploid checkpoint defects of p53-depleted cells, while T18A does not.","method":"In vitro kinase assay, co-immunoprecipitation, ubiquitination assay, phospho-mimetic/deficient mutants, cell cycle analysis","journal":"Molecular and Cellular Biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay plus mutagenesis (T18D/T18A), functional rescue experiment, ubiquitination assay; single lab, multiple orthogonal methods","pmids":["19332559"],"is_preprint":false},{"year":2009,"finding":"CHK2 phosphorylates TTK/hMps1 at Thr288, stabilizing TTK in response to DNA damage; CHK2 knockdown or inhibition abolishes this TTK stabilization; TTK T288A mutant re-expressed in TTK-knockdown cells causes defective G2/M arrest, establishing a CHK2→TTK feedback loop.","method":"siRNA knockdown, CHK2 inhibitor, phospho-specific antibody, mutant re-expression, cell cycle analysis","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phospho-site mapped, kinase identified, mutant re-expression with defined phenotypic readout; single lab","pmids":["19151762"],"is_preprint":false},{"year":2012,"finding":"MPS1/Mph1 phosphorylates KNL1/Spc7 at MELT repeat sequences; this phosphorylation recruits the Bub1-Bub3 complex to the kinetochore in vitro, which is required for SAC activation (Mad1-Mad2-Mad3 localization) and chromosome alignment; non-phosphorylatable spc7-12A abolishes Bub1-Bub3 kinetochore targeting, while phospho-mimetic spc7-12E forces their localization even without Mph1.","method":"In vitro kinase assay, in vitro binding assay, phospho-mimetic/non-phosphorylatable mutants, fluorescence microscopy in fission yeast and human cells","journal":"Nature Cell Biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay and binding assay, replicated independently by two labs (PMIDs 22660415 and 22521786), phospho-mimetic and non-phosphorylatable mutants with clean phenotypic readout","pmids":["22660415","22521786"],"is_preprint":false},{"year":2012,"finding":"Mph1 kinase activity (fission yeast) is required for Mad2 and Mad3 to stably bind the APC/C; a kinase-dead Mph1 allele is checkpoint-defective, and APC/C-associated Mad2 and Mad3 levels are dramatically reduced; specific phosphorylation sites in Mad2 regulate its binding to Cdc20-APC/C.","method":"Kinase-dead allele analysis, APC/C immunoprecipitation/mass spectrometry, Mad2 phospho-site mutagenesis in S. pombe","journal":"Current Biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — kinase-dead allele, biochemical pull-down of APC/C, phospho-site mutagenesis; single lab, multiple orthogonal methods","pmids":["22281223"],"is_preprint":false},{"year":2012,"finding":"Kinetochore recruitment of Mph1 is essential and upstream in the SAC hierarchy in fission yeast; an Mph1 mutant that cannot localize to kinetochores abolishes SAC signaling, and artificial kinetochore tethering of this mutant restores signaling; Mph1 and Aurora kinase Ark1 are at the top of a three-layered SAC protein recruitment hierarchy, with Bub1/Bub3 in the middle and Mad3/Mad1-Mad2 at the bottom.","method":"Separation-of-function mutants, forced kinetochore tethering (Mph1-Ndc80 fusion), fluorescence microscopy, genetic epistasis in S. pombe","journal":"Journal of Cell Science","confidence":"High","confidence_rationale":"Tier 2 / Strong — forced localization rescue experiment, multiple mutant analyses, defined hierarchy established; replicated by independent groups","pmids":["22825872","22184248"],"is_preprint":false},{"year":2015,"finding":"TTK/hMps1 phosphorylates MDM2 in response to oxidative stress, promoting histone H2B ubiquitination and chromatin decompaction, which facilitates oxidative DNA damage repair and ATR-CHK1 (but not ATM-CHK2) signaling; rescue with WT but not phospho-deficient MDM2 confirms TTK-dependent MDM2 phosphorylation is required.","method":"In vitro kinase assay, siRNA knockdown, H2B ubiquitination assay, DNA damage foci analysis, phospho-deficient mutant rescue","journal":"Nucleic Acids Research","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro phosphorylation, mutant rescue, chromatin assay, multiple orthogonal methods; single lab","pmids":["26531827"],"is_preprint":false},{"year":2015,"finding":"TTK inhibition impairs homologous recombination repair (HR) by decreasing Rad51 foci formation; re-expression of wild-type TTK rescues both radioresistance and HR repair, but kinase-dead TTK does not, establishing that TTK kinase activity is required for HR.","method":"Genetic knockdown, kinase-dead mutant re-expression, Rad51 foci immunofluorescence, clonogenic survival assays, in vivo xenograft","journal":"The Journal of Clinical Investigation","confidence":"High","confidence_rationale":"Tier 1 / Moderate — kinase-dead mutant rescue establishes catalytic requirement for HR, multiple cell lines and in vivo validation; single lab","pmids":["31961339"],"is_preprint":false},{"year":2016,"finding":"The Ndc80 hairpin region acts as a kinetochore platform for Mph1/MPS1 recruitment in fission yeast; the ndc80-AK01 point mutation within the hairpin eliminates kinetochore localization of all SAC components including Mph1; artificial tethering of Mph1 to kinetochores in ndc80-AK01 cells fully restores checkpoint signaling.","method":"Point mutagenesis of Ndc80, forced kinetochore tethering, fluorescence microscopy, checkpoint assays in S. pombe","journal":"Cell Cycle","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — structure-function mutagenesis with forced-localization rescue, single lab","pmids":["26900649"],"is_preprint":false},{"year":2017,"finding":"TTK inhibitor NTRC 0066-0 inhibits phosphorylation of the TTK substrate KNL1 in cell lines and in mice, and induces chromosome missegregation; X-ray crystal structures of multiple TTK inhibitors reveal that the most potent compounds induce a shift of the glycine-rich loop by binding the catalytic lysine (Lys553), a 'lysine trap' that disrupts the catalytic machinery.","method":"X-ray crystallography, cellular phosphorylation assays (KNL1), antiproliferative assays, thermal stability experiments","journal":"Journal of Molecular Biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structures with multiple inhibitors, cellular substrate phosphorylation assay, mechanistic explanation of catalytic disruption; single lab but rigorous","pmids":["28539250"],"is_preprint":false},{"year":2018,"finding":"USP9X directly interacts with TTK and deubiquitinates TTK via K48 ubiquitin chain, stabilizing TTK protein; USP9X knockdown reduces TTK protein levels, and this axis promotes NSCLC cell proliferation, migration, and tumorigenesis.","method":"Quantitative proteomics, co-immunoprecipitation, ubiquitination assay, siRNA knockdown, in vivo xenograft","journal":"Theranostics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP and deubiquitination assay establish direct interaction and post-translational modification mechanism; single lab","pmids":["29721084"],"is_preprint":false},{"year":2018,"finding":"Disruption of APC/C complex members confers resistance to TTK inhibitor CFI-402257; genome-wide CRISPR/Cas9 screens identified APC/C components as mediators of TTKi resistance; validated by CRISPR/Cas9 and siRNA, consistent with the APC/C promoting mitotic exit downstream of SAC inactivation by TTK inhibition.","method":"Genome-wide CRISPR/Cas9 screen, siRNA validation, cell viability and cell cycle assays in TNBC lines","journal":"Proceedings of the National Academy of Sciences of the USA","confidence":"High","confidence_rationale":"Tier 2 / Strong — genome-wide unbiased screen with orthogonal validation (CRISPR + siRNA) in multiple lines; establishes APC/C as epistatic downstream effector","pmids":["29378962"],"is_preprint":false},{"year":2022,"finding":"The first irreversible covalent MPS1/TTK inhibitor (RMS-07) was developed targeting a cysteine in the kinase hinge region; covalent binding was validated by mass spectrometry and X-ray crystal structure, confirming the binding site and selectivity mechanism.","method":"X-ray crystallography, mass spectrometry, cellular target engagement assays, antiproliferative assays","journal":"Journal of Medicinal Chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure plus mass spectrometry covalent bond validation; single lab with two orthogonal structural methods","pmids":["35167750"],"is_preprint":false},{"year":2023,"finding":"BMAL1 transcriptionally controls TTK as a circadian-controlled gene; TTK phosphorylates MDM2, which in turn regulates H2B monoubiquitination (H2Bub1); H2Bub1 feeds back to regulate BMAL1 expression, forming a BMAL1–TTK–MDM2–H2Bub1 positive loop that maintains osteogenic capacity of BM-MSCs.","method":"ChIP (BMAL1 on TTK promoter), western blot, phosphorylation assay, rAAV9 in vivo rescue in aging mice","journal":"Molecular Therapy. Nucleic Acids","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and phosphorylation evidence for the pathway, in vivo rescue; single lab","pmids":["36910712"],"is_preprint":false}],"current_model":"TTK (MPS1) is a dual-specificity kinase (phosphorylating Ser, Thr, and Tyr) that acts as a master regulator of the spindle assembly checkpoint by phosphorylating KNL1/Spc7 MELT repeats to recruit Bub1-Bub3, placing it at the apex of a kinetochore-based SAC hierarchy upstream of Mad1-Mad2-Mad3 and APC/C inhibition; it also phosphorylates CHK2 (Thr68), p53 (Thr18), MDM2, and c-Abl (Thr735) to coordinate DNA damage checkpoint responses, homologous recombination repair, and p53 stabilization, and its own stability is regulated by CHK2-mediated phosphorylation at Thr288 and USP9X-mediated deubiquitination."},"narrative":{"mechanistic_narrative":"TTK (MPS1) is a cell-cycle-regulated dual-specificity kinase that serves as the apical activator of the spindle assembly checkpoint (SAC) and additionally couples mitotic surveillance to the DNA damage response [PMID:1639825, PMID:22660415, PMID:22521786]. Its mRNA, protein, and kinase activity peak at G2/M, and during mitosis it localizes dynamically from nuclear pore-adjacent sites to the corona of unattached kinetochores and then to centrosomes [PMID:8302607, PMID:14728800]. At kinetochores, MPS1/Mph1 phosphorylates the MELT repeats of KNL1/Spc7 to recruit the Bub1-Bub3 complex, which in turn licenses downstream Mad1-Mad2-Mad3 loading—placing MPS1 at the top of a three-tiered SAC recruitment hierarchy whose own kinetochore targeting depends on the Ndc80 hairpin platform [PMID:22660415, PMID:22521786, PMID:22825872, PMID:22184248, PMID:26900649]. Mph1 kinase activity is further required for stable association of Mad2 and Mad3 with the APC/C, and genetic disruption of APC/C components confers resistance to TTK inhibition, identifying the APC/C as the epistatic effector downstream of SAC inactivation [PMID:22281223, PMID:29378962]. Beyond mitosis, TTK phosphorylates CHK2 (Thr68), p53 (Thr18), and MDM2 to enforce DNA damage and tetraploidy checkpoints: p53 Thr18 phosphorylation disrupts the p53-MDM2 interaction and stabilizes p53, MDM2 phosphorylation under oxidative stress drives H2B ubiquitination, chromatin decompaction, and ATR-CHK1 signaling, and TTK kinase activity is required for Rad51-dependent homologous recombination repair [PMID:15618221, PMID:19332559, PMID:26531827, PMID:31961339]. TTK also phosphorylates c-Abl at Thr735 to promote 14-3-3 binding and cytoplasmic sequestration of c-Abl [PMID:18794806]. TTK abundance is set post-translationally by a CHK2-mediated feedback phosphorylation at Thr288 that stabilizes the kinase after DNA damage and by USP9X-mediated K48 deubiquitination [PMID:19151762, PMID:29721084]. Structural and chemical-biology work has defined distinct inhibitor mechanisms, including a glycine-loop 'lysine trap' engaging the catalytic Lys553 and an irreversible covalent inhibitor targeting a hinge cysteine [PMID:28539250, PMID:35167750].","teleology":[{"year":1992,"claim":"Established the fundamental enzymatic identity of TTK by showing it is catalytically active as a dual-specificity kinase, the prerequisite for assigning it any signaling role.","evidence":"Kinase domain expressed in E. coli with phosphoamino acid analysis","pmids":["1639825"],"confidence":"Medium","gaps":["Single method without mutagenesis validation of the active site","Physiological substrates not identified","Tyrosine activity only marginally elevated"]},{"year":1994,"claim":"Linked TTK to mitosis by demonstrating its expression and activity peak at G2/M, framing it as a cell-cycle-regulated kinase rather than a constitutive one.","evidence":"Cell synchronization with mRNA, protein, and kinase activity assays","pmids":["8302607"],"confidence":"Medium","gaps":["Does not identify the mitotic process TTK controls","Mechanism of cell-cycle-dependent regulation unresolved"]},{"year":1998,"claim":"Placed the MPS1 homolog functionally within the spindle assembly checkpoint, showing it acts upstream of Mad2 and is sufficient to impose checkpoint arrest.","evidence":"Genetic epistasis, overexpression, and complementation in S. pombe (Mph1)","pmids":["9601094"],"confidence":"High","gaps":["Molecular substrate at the kinetochore not identified","Human ortholog SAC role not yet established in this study"]},{"year":2003,"claim":"Resolved where TTK acts during mitosis at ultrastructural resolution, localizing it to the kinetochore corona of unattached kinetochores and to centrosomes.","evidence":"Immunoelectron microscopy of HeLa cells","pmids":["14728800"],"confidence":"Medium","gaps":["Single method and single lab","Functional consequence of each localization not dissected"]},{"year":2004,"claim":"Extended TTK function beyond mitosis to the DNA damage checkpoint by establishing it as a direct upstream kinase of CHK2 at Thr68 required for G2/M arrest.","evidence":"In vitro kinase assay, kinase-dead D647A mutant, and siRNA with cell cycle readout","pmids":["15618221"],"confidence":"High","gaps":["In vivo Thr68 phosphorylation relative to ATM not fully separated","How DNA damage activates TTK toward CHK2 unresolved"]},{"year":2004,"claim":"Connected TTK kinase activity to centrosome and chromosome organization through a requirement for centrosomal TACC2 localization.","evidence":"Co-IP with kinase-dead mutant, immunofluorescence, TTK knockdown","pmids":["15304323"],"confidence":"Medium","gaps":["Direct TACC2 phosphorylation site not mapped","Single lab without structural detail"]},{"year":2008,"claim":"Identified c-Abl as a TTK substrate (Thr735), revealing a mechanism by which TTK controls c-Abl localization and apoptotic output under oxidative stress.","evidence":"Expression cloning, in vitro kinase assay, phosphospecific antibody, siRNA, fractionation","pmids":["18794806"],"confidence":"High","gaps":["Quantitative contribution to stress-induced apoptosis not bounded","Interplay with mitotic role of TTK unexplored"]},{"year":2009,"claim":"Defined a feedback architecture in which TTK phosphorylates p53 at Thr18 to stabilize p53 while CHK2 reciprocally phosphorylates TTK at Thr288 to stabilize TTK after DNA damage.","evidence":"In vitro kinase assays, ubiquitination assay, phospho-mimetic/deficient and T288A mutants, rescue and cell cycle analysis","pmids":["19332559","19151762"],"confidence":"High","gaps":["Stoichiometry and temporal order of the CHK2-TTK-p53 loop not fully resolved","MDM2 phosphorylation step not yet defined here"]},{"year":2012,"claim":"Established the molecular basis of SAC initiation by showing MPS1/Mph1 phosphorylates KNL1/Spc7 MELT repeats to recruit Bub1-Bub3 and sits atop a defined kinetochore signaling hierarchy that ultimately stabilizes Mad2/Mad3 on the APC/C.","evidence":"In vitro kinase and binding assays, phospho-mimetic/non-phosphorylatable mutants, forced kinetochore tethering, and APC/C pulldowns in yeast and human cells","pmids":["22660415","22521786","22281223","22825872","22184248"],"confidence":"High","gaps":["Precise contribution of human MPS1 to each hierarchical layer not fully separated from yeast data","Phosphatase counteraction of MELT phosphorylation not addressed here"]},{"year":2015,"claim":"Broadened TTK's genome-maintenance role by showing it phosphorylates MDM2 to drive H2B ubiquitination/chromatin decompaction supporting ATR-CHK1 signaling, and that its kinase activity is required for Rad51-dependent homologous recombination.","evidence":"In vitro kinase assays, H2B ubiquitination assay, Rad51 foci, kinase-dead and phospho-deficient rescue, clonogenic survival, xenograft","pmids":["26531827","31961339"],"confidence":"High","gaps":["Direct HR substrate of TTK not identified","Selectivity of MDM2 phosphorylation for ATR over ATM pathway mechanistically incomplete"]},{"year":2016,"claim":"Defined the kinetochore docking platform for MPS1, showing the Ndc80 hairpin is required for its recruitment and that forced tethering bypasses loss of the platform.","evidence":"Ndc80 point mutagenesis, forced kinetochore tethering, checkpoint assays in S. pombe","pmids":["26900649"],"confidence":"Medium","gaps":["Direct MPS1-Ndc80 contact interface not structurally resolved","Conservation to human kinetochores not tested here"]},{"year":2018,"claim":"Identified post-translational and genetic determinants of TTK function in cancer: USP9X stabilizes TTK by K48 deubiquitination, and APC/C disruption mediates resistance to TTK inhibitors, confirming the APC/C as the downstream effector of SAC release.","evidence":"Co-IP, deubiquitination assay, genome-wide CRISPR screen with siRNA validation, xenografts","pmids":["29721084","29378962"],"confidence":"High","gaps":["USP9X target lysines on TTK not mapped","How APC/C loss bypasses mitotic catastrophe mechanistically incomplete"]},{"year":2022,"claim":"Advanced TTK as a druggable target by defining inhibitor binding mechanisms, including a catalytic-lysine glycine-loop trap and an irreversible covalent hinge-cysteine inhibitor.","evidence":"X-ray crystallography, mass spectrometry, cellular KNL1 phosphorylation and target engagement assays","pmids":["28539250","35167750"],"confidence":"High","gaps":["In vivo durability and selectivity of covalent inhibition not fully characterized","Resistance mechanisms to covalent inhibitors not defined"]},{"year":2023,"claim":"Integrated TTK into circadian and tissue-maintenance physiology via a BMAL1-TTK-MDM2-H2Bub1 positive feedback loop supporting osteogenic capacity.","evidence":"ChIP of BMAL1 on TTK promoter, phosphorylation assays, rAAV9 in vivo rescue in aging mice","pmids":["36910712"],"confidence":"Medium","gaps":["Direct MDM2 phosphosites in this context not mapped","Single lab and tissue-specific generality unestablished"]},{"year":null,"claim":"How TTK's apical SAC kinase activity, DNA damage checkpoint substrates, and HR repair function are coordinately regulated within a single cell cycle remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking kinetochore and nuclear TTK pools","Phosphatase and degradation control of TTK activity across mitosis incompletely mapped","Direct HR substrate of TTK still unidentified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,4,6,7,9,12]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,4,7,9]},{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[15]}],"localization":[{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[3,9]},{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[3,5]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[2,9,10,11,17]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[4,12,13]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[6,7,12]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[12,19]}],"complexes":[],"partners":["KNL1","BUB1","BUB3","CHK2","TP53","MDM2","USP9X","ABL1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P33981","full_name":"Dual specificity protein kinase TTK","aliases":["Phosphotyrosine picked threonine-protein kinase","PYT"],"length_aa":857,"mass_kda":97.1,"function":"Involved in mitotic spindle assembly checkpoint signaling, a process that delays anaphase until chromosomes are bioriented on the spindle, and in the repair of incorrect mitotic kinetochore-spindle microtubule attachments (PubMed:18243099, PubMed:28441529, PubMed:29162720). Phosphorylates MAD1L1 to promote the mitotic spindle assembly checkpoint (PubMed:18243099, PubMed:29162720). Phosphorylates CDCA8/Borealin leading to enhanced AURKB activity at the kinetochore (PubMed:18243099). Phosphorylates SKA3 at 'Ser-34' leading to dissociation of the SKA complex from microtubules and destabilization of microtubule-kinetochore attachments (PubMed:28441529). Phosphorylates KNL1, KNTC1 and autophosphorylates (PubMed:28441529). Phosphorylates MCRS1 which enhances recruitment of KIF2A to the minus end of spindle microtubules and promotes chromosome alignment (PubMed:30785839)","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/P33981/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/TTK","classification":"Common Essential","n_dependent_lines":1100,"n_total_lines":1208,"dependency_fraction":0.9105960264900662},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000112742","cell_line_id":"CID001295","localizations":[{"compartment":"centrosome","grade":3},{"compartment":"cytoplasmic","grade":3},{"compartment":"nucleoplasm","grade":3}],"interactors":[{"gene":"VPS8","stoichiometry":10.0},{"gene":"CANX","stoichiometry":0.2},{"gene":"RCBTB2","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID001295","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":"610859","title":"CAPPING PROTEIN REGULATOR AND MYOSIN 1 LINKER 2; CARMIL2","url":"https://www.omim.org/entry/610859"},{"mim_id":"604094","title":"MITOTIC ARREST-DEFICIENT 2 LIKE 2; MAD2L2","url":"https://www.omim.org/entry/604094"},{"mim_id":"604092","title":"TTK PROTEIN KINASE; TTK","url":"https://www.omim.org/entry/604092"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"},{"location":"Nucleoli","reliability":"Additional"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"bone marrow","ntpm":23.9},{"tissue":"lymphoid 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medicine","url":"https://pubmed.ncbi.nlm.nih.gov/36829176","citation_count":17,"is_preprint":false},{"pmid":"27257873","id":"PMC_27257873","title":"Binding of the Fkh1 Forkhead Associated Domain to a Phosphopeptide within the Mph1 DNA Helicase Regulates Mating-Type Switching in Budding Yeast.","date":"2016","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27257873","citation_count":17,"is_preprint":false},{"pmid":"33248853","id":"PMC_33248853","title":"Pyrido[2, 3-d]pyrimidin-7(8H)-ones as new selective orally bioavailable Threonine Tyrosine Kinase (TTK) inhibitors.","date":"2020","source":"European journal of medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/33248853","citation_count":17,"is_preprint":false},{"pmid":"10671299","id":"PMC_10671299","title":"Tumour necrosis factor alpha enhances the expression of hydroxyl lyase, cytoplasmic antiproteinase-2 and a dual specificity kinase TTK in human chondrocyte-like 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reports","url":"https://pubmed.ncbi.nlm.nih.gov/27618721","citation_count":16,"is_preprint":false},{"pmid":"31607131","id":"PMC_31607131","title":"TTK contributes to tumor growth and metastasis of clear cell renal cell carcinoma by inducing cell proliferation and invasion.","date":"2019","source":"Neoplasma","url":"https://pubmed.ncbi.nlm.nih.gov/31607131","citation_count":14,"is_preprint":false},{"pmid":"25801152","id":"PMC_25801152","title":"A unique hinge binder of extremely selective aminopyridine-based Mps1 (TTK) kinase inhibitors with cellular activity.","date":"2015","source":"Bioorganic & medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/25801152","citation_count":14,"is_preprint":false},{"pmid":"36910712","id":"PMC_36910712","title":"BMAL1-TTK-H2Bub1 loop deficiency contributes to impaired BM-MSC-mediated bone formation in senile osteoporosis.","date":"2023","source":"Molecular therapy. Nucleic acids","url":"https://pubmed.ncbi.nlm.nih.gov/36910712","citation_count":13,"is_preprint":false},{"pmid":"35850753","id":"PMC_35850753","title":"TTK Protein Kinase promotes temozolomide resistance through inducing autophagy in glioblastoma.","date":"2022","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/35850753","citation_count":13,"is_preprint":false},{"pmid":"33689884","id":"PMC_33689884","title":"TTK inhibitor promotes radiosensitivity of liver cancer cells through p21.","date":"2021","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/33689884","citation_count":13,"is_preprint":false},{"pmid":"34953918","id":"PMC_34953918","title":"Tumour suppressor role of microRNA-335-5p in esophageal squamous cell carcinoma by targeting TTK (Mps1).","date":"2021","source":"Experimental and molecular pathology","url":"https://pubmed.ncbi.nlm.nih.gov/34953918","citation_count":13,"is_preprint":false},{"pmid":"26900649","id":"PMC_26900649","title":"The hairpin region of Ndc80 is important for the kinetochore recruitment of Mph1/MPS1 in fission yeast.","date":"2016","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/26900649","citation_count":13,"is_preprint":false},{"pmid":"30998356","id":"PMC_30998356","title":"Design and Optimization Leading to an Orally Active TTK Protein Kinase Inhibitor with Robust Single Agent Efficacy.","date":"2019","source":"Journal of medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/30998356","citation_count":13,"is_preprint":false},{"pmid":"27335255","id":"PMC_27335255","title":"Discovery of 4-(4-aminopyrazolo[1,5-a][1,3,5]triazin-8-yl)benzamides as novel, highly potent and selective, orally bioavailable inhibitors of Tyrosine Threonine Kinase, TTK.","date":"2016","source":"Bioorganic & medicinal chemistry letters","url":"https://pubmed.ncbi.nlm.nih.gov/27335255","citation_count":13,"is_preprint":false},{"pmid":"30038707","id":"PMC_30038707","title":"LMO1 functions as an oncogene by regulating TTK expression and correlates with neuroendocrine differentiation of lung cancer.","date":"2018","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/30038707","citation_count":13,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":48061,"output_tokens":4956,"usd":0.109261,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13214,"output_tokens":4886,"usd":0.09411,"stage2_stop_reason":"end_turn"},"total_usd":0.203371,"stage1_batch_id":"msgbatch_017qqVz33Ga63SCDwzb35XPb","stage2_batch_id":"msgbatch_01Scr2Ei9x4HJMiRGxwrmvLK","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1992,\n      \"finding\": \"TTK is a dual-specificity kinase capable of phosphorylating serine, threonine, and tyrosine residues; when the kinase domain was expressed in E. coli, elevated phosphoserine and phosphothreonine (and slightly elevated phosphotyrosine) were detected, establishing its catalytic activity.\",\n      \"method\": \"Expression of kinase domain in E. coli with phosphoamino acid analysis\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — direct in vitro enzymatic activity demonstrated, but single lab, single method, no mutagenesis validation\",\n      \"pmids\": [\"1639825\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"TTK mRNA, protein, and kinase activity peak at G2/M phase of the cell cycle; levels are very low in starved/G1 cells and rise upon S-phase entry, establishing cell-cycle-dependent regulation of TTK.\",\n      \"method\": \"Cell synchronization, mRNA/protein quantification, kinase activity assays across cell cycle stages\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (mRNA, protein, kinase activity) in synchronized cells, single lab\",\n      \"pmids\": [\"8302607\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Fission yeast Mph1 (MPS1 homolog) functions upstream of Mad2 in the spindle assembly checkpoint; overexpression of mph1 mimics checkpoint activation and imposes metaphase arrest, while mph1 is required for checkpoint activation in response to spindle defects. Genetic epistasis places mph1 upstream of mad2.\",\n      \"method\": \"Genetic epistasis, overexpression, complementation analysis in S. pombe\",\n      \"journal\": \"Journal of Cell Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — epistasis confirmed by multiple genetic approaches, replicated in subsequent studies\",\n      \"pmids\": [\"9601094\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"TTK localizes dynamically during mitosis in HeLa cells: at nuclear pore-adjacent complex in interphase, then to corona fibers of unattached kinetochores (extending ~90 nm from the outer plate), and migrates to centrosomes upon metaphase alignment, supporting a role in spindle checkpoint signaling at both kinetochore and centrosome.\",\n      \"method\": \"Immunoelectron microscopy of HeLa cells\",\n      \"journal\": \"Cell Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct ultrastructural localization, single lab, single method\",\n      \"pmids\": [\"14728800\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"TTK/hMps1 directly phosphorylates CHK2 at Thr-68 in vitro; expression of a kinase-dead TTK(D647A) mutant impairs G2/M arrest and CHK2 Thr-68 phosphorylation after DNA damage; siRNA depletion of TTK reduces CHK2 Thr-68 phosphorylation and impairs growth arrest, placing TTK upstream of CHK2 in the DNA damage checkpoint.\",\n      \"method\": \"In vitro kinase assay, kinase-dead mutant expression, siRNA knockdown, cell cycle analysis\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro phosphorylation assay plus kinase-dead mutant and siRNA knockdown with defined phenotypic readout, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"15618221\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"TTK kinase activity is required for centrosomal localization of TACC2; TACC2 is pulled down by wild-type TTK but not kinase-dead TTK; expression of kinase-dead TTK or TTK depletion eliminates centrosomal TACC2, causing chromosome misalignment and reduced centrosome separation.\",\n      \"method\": \"Co-immunoprecipitation/pulldown with kinase-dead mutant, immunofluorescence, TTK knockdown\",\n      \"journal\": \"FEBS Letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP with kinase-dead mutant and localization with functional consequence, single lab\",\n      \"pmids\": [\"15304323\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"TTK phosphorylates c-Abl at Thr735 (identified by expression cloning with a phosphospecific antibody); this phosphorylation promotes 14-3-3 binding to c-Abl, sequestering it in the cytoplasm; TTK knockdown abolishes oxidative stress-induced Thr735 phosphorylation and causes constitutive nuclear accumulation of c-Abl, enhancing apoptosis.\",\n      \"method\": \"Expression cloning, in vitro kinase assay, phosphospecific antibody, siRNA knockdown, subcellular fractionation/localization\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — expression cloning with phosphospecific readout, in vitro kinase assay, siRNA validation, functional consequence established, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"18794806\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"TTK/hMps1 phosphorylates p53 at Thr18 in vitro, disrupting the p53-MDM2 interaction and abrogating MDM2-mediated p53 ubiquitination; this phosphorylation stabilizes p53 and activates p21 and Lats2 after spindle disruption; phospho-mimetic T18D rescues tetraploid checkpoint defects of p53-depleted cells, while T18A does not.\",\n      \"method\": \"In vitro kinase assay, co-immunoprecipitation, ubiquitination assay, phospho-mimetic/deficient mutants, cell cycle analysis\",\n      \"journal\": \"Molecular and Cellular Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay plus mutagenesis (T18D/T18A), functional rescue experiment, ubiquitination assay; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"19332559\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CHK2 phosphorylates TTK/hMps1 at Thr288, stabilizing TTK in response to DNA damage; CHK2 knockdown or inhibition abolishes this TTK stabilization; TTK T288A mutant re-expressed in TTK-knockdown cells causes defective G2/M arrest, establishing a CHK2→TTK feedback loop.\",\n      \"method\": \"siRNA knockdown, CHK2 inhibitor, phospho-specific antibody, mutant re-expression, cell cycle analysis\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phospho-site mapped, kinase identified, mutant re-expression with defined phenotypic readout; single lab\",\n      \"pmids\": [\"19151762\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"MPS1/Mph1 phosphorylates KNL1/Spc7 at MELT repeat sequences; this phosphorylation recruits the Bub1-Bub3 complex to the kinetochore in vitro, which is required for SAC activation (Mad1-Mad2-Mad3 localization) and chromosome alignment; non-phosphorylatable spc7-12A abolishes Bub1-Bub3 kinetochore targeting, while phospho-mimetic spc7-12E forces their localization even without Mph1.\",\n      \"method\": \"In vitro kinase assay, in vitro binding assay, phospho-mimetic/non-phosphorylatable mutants, fluorescence microscopy in fission yeast and human cells\",\n      \"journal\": \"Nature Cell Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay and binding assay, replicated independently by two labs (PMIDs 22660415 and 22521786), phospho-mimetic and non-phosphorylatable mutants with clean phenotypic readout\",\n      \"pmids\": [\"22660415\", \"22521786\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Mph1 kinase activity (fission yeast) is required for Mad2 and Mad3 to stably bind the APC/C; a kinase-dead Mph1 allele is checkpoint-defective, and APC/C-associated Mad2 and Mad3 levels are dramatically reduced; specific phosphorylation sites in Mad2 regulate its binding to Cdc20-APC/C.\",\n      \"method\": \"Kinase-dead allele analysis, APC/C immunoprecipitation/mass spectrometry, Mad2 phospho-site mutagenesis in S. pombe\",\n      \"journal\": \"Current Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — kinase-dead allele, biochemical pull-down of APC/C, phospho-site mutagenesis; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"22281223\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Kinetochore recruitment of Mph1 is essential and upstream in the SAC hierarchy in fission yeast; an Mph1 mutant that cannot localize to kinetochores abolishes SAC signaling, and artificial kinetochore tethering of this mutant restores signaling; Mph1 and Aurora kinase Ark1 are at the top of a three-layered SAC protein recruitment hierarchy, with Bub1/Bub3 in the middle and Mad3/Mad1-Mad2 at the bottom.\",\n      \"method\": \"Separation-of-function mutants, forced kinetochore tethering (Mph1-Ndc80 fusion), fluorescence microscopy, genetic epistasis in S. pombe\",\n      \"journal\": \"Journal of Cell Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — forced localization rescue experiment, multiple mutant analyses, defined hierarchy established; replicated by independent groups\",\n      \"pmids\": [\"22825872\", \"22184248\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TTK/hMps1 phosphorylates MDM2 in response to oxidative stress, promoting histone H2B ubiquitination and chromatin decompaction, which facilitates oxidative DNA damage repair and ATR-CHK1 (but not ATM-CHK2) signaling; rescue with WT but not phospho-deficient MDM2 confirms TTK-dependent MDM2 phosphorylation is required.\",\n      \"method\": \"In vitro kinase assay, siRNA knockdown, H2B ubiquitination assay, DNA damage foci analysis, phospho-deficient mutant rescue\",\n      \"journal\": \"Nucleic Acids Research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro phosphorylation, mutant rescue, chromatin assay, multiple orthogonal methods; single lab\",\n      \"pmids\": [\"26531827\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TTK inhibition impairs homologous recombination repair (HR) by decreasing Rad51 foci formation; re-expression of wild-type TTK rescues both radioresistance and HR repair, but kinase-dead TTK does not, establishing that TTK kinase activity is required for HR.\",\n      \"method\": \"Genetic knockdown, kinase-dead mutant re-expression, Rad51 foci immunofluorescence, clonogenic survival assays, in vivo xenograft\",\n      \"journal\": \"The Journal of Clinical Investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — kinase-dead mutant rescue establishes catalytic requirement for HR, multiple cell lines and in vivo validation; single lab\",\n      \"pmids\": [\"31961339\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The Ndc80 hairpin region acts as a kinetochore platform for Mph1/MPS1 recruitment in fission yeast; the ndc80-AK01 point mutation within the hairpin eliminates kinetochore localization of all SAC components including Mph1; artificial tethering of Mph1 to kinetochores in ndc80-AK01 cells fully restores checkpoint signaling.\",\n      \"method\": \"Point mutagenesis of Ndc80, forced kinetochore tethering, fluorescence microscopy, checkpoint assays in S. pombe\",\n      \"journal\": \"Cell Cycle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — structure-function mutagenesis with forced-localization rescue, single lab\",\n      \"pmids\": [\"26900649\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TTK inhibitor NTRC 0066-0 inhibits phosphorylation of the TTK substrate KNL1 in cell lines and in mice, and induces chromosome missegregation; X-ray crystal structures of multiple TTK inhibitors reveal that the most potent compounds induce a shift of the glycine-rich loop by binding the catalytic lysine (Lys553), a 'lysine trap' that disrupts the catalytic machinery.\",\n      \"method\": \"X-ray crystallography, cellular phosphorylation assays (KNL1), antiproliferative assays, thermal stability experiments\",\n      \"journal\": \"Journal of Molecular Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structures with multiple inhibitors, cellular substrate phosphorylation assay, mechanistic explanation of catalytic disruption; single lab but rigorous\",\n      \"pmids\": [\"28539250\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"USP9X directly interacts with TTK and deubiquitinates TTK via K48 ubiquitin chain, stabilizing TTK protein; USP9X knockdown reduces TTK protein levels, and this axis promotes NSCLC cell proliferation, migration, and tumorigenesis.\",\n      \"method\": \"Quantitative proteomics, co-immunoprecipitation, ubiquitination assay, siRNA knockdown, in vivo xenograft\",\n      \"journal\": \"Theranostics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP and deubiquitination assay establish direct interaction and post-translational modification mechanism; single lab\",\n      \"pmids\": [\"29721084\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Disruption of APC/C complex members confers resistance to TTK inhibitor CFI-402257; genome-wide CRISPR/Cas9 screens identified APC/C components as mediators of TTKi resistance; validated by CRISPR/Cas9 and siRNA, consistent with the APC/C promoting mitotic exit downstream of SAC inactivation by TTK inhibition.\",\n      \"method\": \"Genome-wide CRISPR/Cas9 screen, siRNA validation, cell viability and cell cycle assays in TNBC lines\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the USA\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genome-wide unbiased screen with orthogonal validation (CRISPR + siRNA) in multiple lines; establishes APC/C as epistatic downstream effector\",\n      \"pmids\": [\"29378962\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The first irreversible covalent MPS1/TTK inhibitor (RMS-07) was developed targeting a cysteine in the kinase hinge region; covalent binding was validated by mass spectrometry and X-ray crystal structure, confirming the binding site and selectivity mechanism.\",\n      \"method\": \"X-ray crystallography, mass spectrometry, cellular target engagement assays, antiproliferative assays\",\n      \"journal\": \"Journal of Medicinal Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure plus mass spectrometry covalent bond validation; single lab with two orthogonal structural methods\",\n      \"pmids\": [\"35167750\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"BMAL1 transcriptionally controls TTK as a circadian-controlled gene; TTK phosphorylates MDM2, which in turn regulates H2B monoubiquitination (H2Bub1); H2Bub1 feeds back to regulate BMAL1 expression, forming a BMAL1–TTK–MDM2–H2Bub1 positive loop that maintains osteogenic capacity of BM-MSCs.\",\n      \"method\": \"ChIP (BMAL1 on TTK promoter), western blot, phosphorylation assay, rAAV9 in vivo rescue in aging mice\",\n      \"journal\": \"Molecular Therapy. Nucleic Acids\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and phosphorylation evidence for the pathway, in vivo rescue; single lab\",\n      \"pmids\": [\"36910712\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TTK (MPS1) is a dual-specificity kinase (phosphorylating Ser, Thr, and Tyr) that acts as a master regulator of the spindle assembly checkpoint by phosphorylating KNL1/Spc7 MELT repeats to recruit Bub1-Bub3, placing it at the apex of a kinetochore-based SAC hierarchy upstream of Mad1-Mad2-Mad3 and APC/C inhibition; it also phosphorylates CHK2 (Thr68), p53 (Thr18), MDM2, and c-Abl (Thr735) to coordinate DNA damage checkpoint responses, homologous recombination repair, and p53 stabilization, and its own stability is regulated by CHK2-mediated phosphorylation at Thr288 and USP9X-mediated deubiquitination.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TTK (MPS1) is a cell-cycle-regulated dual-specificity kinase that serves as the apical activator of the spindle assembly checkpoint (SAC) and additionally couples mitotic surveillance to the DNA damage response [#0, #9]. Its mRNA, protein, and kinase activity peak at G2/M, and during mitosis it localizes dynamically from nuclear pore-adjacent sites to the corona of unattached kinetochores and then to centrosomes [#1, #3]. At kinetochores, MPS1/Mph1 phosphorylates the MELT repeats of KNL1/Spc7 to recruit the Bub1-Bub3 complex, which in turn licenses downstream Mad1-Mad2-Mad3 loading—placing MPS1 at the top of a three-tiered SAC recruitment hierarchy whose own kinetochore targeting depends on the Ndc80 hairpin platform [#9, #11, #14]. Mph1 kinase activity is further required for stable association of Mad2 and Mad3 with the APC/C, and genetic disruption of APC/C components confers resistance to TTK inhibition, identifying the APC/C as the epistatic effector downstream of SAC inactivation [#10, #17]. Beyond mitosis, TTK phosphorylates CHK2 (Thr68), p53 (Thr18), and MDM2 to enforce DNA damage and tetraploidy checkpoints: p53 Thr18 phosphorylation disrupts the p53-MDM2 interaction and stabilizes p53, MDM2 phosphorylation under oxidative stress drives H2B ubiquitination, chromatin decompaction, and ATR-CHK1 signaling, and TTK kinase activity is required for Rad51-dependent homologous recombination repair [#4, #7, #12, #13]. TTK also phosphorylates c-Abl at Thr735 to promote 14-3-3 binding and cytoplasmic sequestration of c-Abl [#6]. TTK abundance is set post-translationally by a CHK2-mediated feedback phosphorylation at Thr288 that stabilizes the kinase after DNA damage and by USP9X-mediated K48 deubiquitination [#8, #16]. Structural and chemical-biology work has defined distinct inhibitor mechanisms, including a glycine-loop 'lysine trap' engaging the catalytic Lys553 and an irreversible covalent inhibitor targeting a hinge cysteine [#15, #18].\",\n  \"teleology\": [\n    {\n      \"year\": 1992,\n      \"claim\": \"Established the fundamental enzymatic identity of TTK by showing it is catalytically active as a dual-specificity kinase, the prerequisite for assigning it any signaling role.\",\n      \"evidence\": \"Kinase domain expressed in E. coli with phosphoamino acid analysis\",\n      \"pmids\": [\"1639825\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Single method without mutagenesis validation of the active site\", \"Physiological substrates not identified\", \"Tyrosine activity only marginally elevated\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Linked TTK to mitosis by demonstrating its expression and activity peak at G2/M, framing it as a cell-cycle-regulated kinase rather than a constitutive one.\",\n      \"evidence\": \"Cell synchronization with mRNA, protein, and kinase activity assays\",\n      \"pmids\": [\"8302607\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Does not identify the mitotic process TTK controls\", \"Mechanism of cell-cycle-dependent regulation unresolved\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Placed the MPS1 homolog functionally within the spindle assembly checkpoint, showing it acts upstream of Mad2 and is sufficient to impose checkpoint arrest.\",\n      \"evidence\": \"Genetic epistasis, overexpression, and complementation in S. pombe (Mph1)\",\n      \"pmids\": [\"9601094\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Molecular substrate at the kinetochore not identified\", \"Human ortholog SAC role not yet established in this study\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Resolved where TTK acts during mitosis at ultrastructural resolution, localizing it to the kinetochore corona of unattached kinetochores and to centrosomes.\",\n      \"evidence\": \"Immunoelectron microscopy of HeLa cells\",\n      \"pmids\": [\"14728800\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Single method and single lab\", \"Functional consequence of each localization not dissected\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Extended TTK function beyond mitosis to the DNA damage checkpoint by establishing it as a direct upstream kinase of CHK2 at Thr68 required for G2/M arrest.\",\n      \"evidence\": \"In vitro kinase assay, kinase-dead D647A mutant, and siRNA with cell cycle readout\",\n      \"pmids\": [\"15618221\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"In vivo Thr68 phosphorylation relative to ATM not fully separated\", \"How DNA damage activates TTK toward CHK2 unresolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Connected TTK kinase activity to centrosome and chromosome organization through a requirement for centrosomal TACC2 localization.\",\n      \"evidence\": \"Co-IP with kinase-dead mutant, immunofluorescence, TTK knockdown\",\n      \"pmids\": [\"15304323\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Direct TACC2 phosphorylation site not mapped\", \"Single lab without structural detail\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identified c-Abl as a TTK substrate (Thr735), revealing a mechanism by which TTK controls c-Abl localization and apoptotic output under oxidative stress.\",\n      \"evidence\": \"Expression cloning, in vitro kinase assay, phosphospecific antibody, siRNA, fractionation\",\n      \"pmids\": [\"18794806\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Quantitative contribution to stress-induced apoptosis not bounded\", \"Interplay with mitotic role of TTK unexplored\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Defined a feedback architecture in which TTK phosphorylates p53 at Thr18 to stabilize p53 while CHK2 reciprocally phosphorylates TTK at Thr288 to stabilize TTK after DNA damage.\",\n      \"evidence\": \"In vitro kinase assays, ubiquitination assay, phospho-mimetic/deficient and T288A mutants, rescue and cell cycle analysis\",\n      \"pmids\": [\"19332559\", \"19151762\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Stoichiometry and temporal order of the CHK2-TTK-p53 loop not fully resolved\", \"MDM2 phosphorylation step not yet defined here\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Established the molecular basis of SAC initiation by showing MPS1/Mph1 phosphorylates KNL1/Spc7 MELT repeats to recruit Bub1-Bub3 and sits atop a defined kinetochore signaling hierarchy that ultimately stabilizes Mad2/Mad3 on the APC/C.\",\n      \"evidence\": \"In vitro kinase and binding assays, phospho-mimetic/non-phosphorylatable mutants, forced kinetochore tethering, and APC/C pulldowns in yeast and human cells\",\n      \"pmids\": [\"22660415\", \"22521786\", \"22281223\", \"22825872\", \"22184248\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Precise contribution of human MPS1 to each hierarchical layer not fully separated from yeast data\", \"Phosphatase counteraction of MELT phosphorylation not addressed here\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Broadened TTK's genome-maintenance role by showing it phosphorylates MDM2 to drive H2B ubiquitination/chromatin decompaction supporting ATR-CHK1 signaling, and that its kinase activity is required for Rad51-dependent homologous recombination.\",\n      \"evidence\": \"In vitro kinase assays, H2B ubiquitination assay, Rad51 foci, kinase-dead and phospho-deficient rescue, clonogenic survival, xenograft\",\n      \"pmids\": [\"26531827\", \"31961339\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Direct HR substrate of TTK not identified\", \"Selectivity of MDM2 phosphorylation for ATR over ATM pathway mechanistically incomplete\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined the kinetochore docking platform for MPS1, showing the Ndc80 hairpin is required for its recruitment and that forced tethering bypasses loss of the platform.\",\n      \"evidence\": \"Ndc80 point mutagenesis, forced kinetochore tethering, checkpoint assays in S. pombe\",\n      \"pmids\": [\"26900649\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Direct MPS1-Ndc80 contact interface not structurally resolved\", \"Conservation to human kinetochores not tested here\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified post-translational and genetic determinants of TTK function in cancer: USP9X stabilizes TTK by K48 deubiquitination, and APC/C disruption mediates resistance to TTK inhibitors, confirming the APC/C as the downstream effector of SAC release.\",\n      \"evidence\": \"Co-IP, deubiquitination assay, genome-wide CRISPR screen with siRNA validation, xenografts\",\n      \"pmids\": [\"29721084\", \"29378962\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"USP9X target lysines on TTK not mapped\", \"How APC/C loss bypasses mitotic catastrophe mechanistically incomplete\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Advanced TTK as a druggable target by defining inhibitor binding mechanisms, including a catalytic-lysine glycine-loop trap and an irreversible covalent hinge-cysteine inhibitor.\",\n      \"evidence\": \"X-ray crystallography, mass spectrometry, cellular KNL1 phosphorylation and target engagement assays\",\n      \"pmids\": [\"28539250\", \"35167750\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"In vivo durability and selectivity of covalent inhibition not fully characterized\", \"Resistance mechanisms to covalent inhibitors not defined\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Integrated TTK into circadian and tissue-maintenance physiology via a BMAL1-TTK-MDM2-H2Bub1 positive feedback loop supporting osteogenic capacity.\",\n      \"evidence\": \"ChIP of BMAL1 on TTK promoter, phosphorylation assays, rAAV9 in vivo rescue in aging mice\",\n      \"pmids\": [\"36910712\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Direct MDM2 phosphosites in this context not mapped\", \"Single lab and tissue-specific generality unestablished\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How TTK's apical SAC kinase activity, DNA damage checkpoint substrates, and HR repair function are coordinately regulated within a single cell cycle remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"No unified model linking kinetochore and nuclear TTK pools\", \"Phosphatase and degradation control of TTK activity across mitosis incompletely mapped\", \"Direct HR substrate of TTK still unidentified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 4, 6, 7, 9, 12]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 4, 7, 9]},\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [15]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [3, 9]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [3, 5]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [2, 9, 10, 11, 17]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [4, 12, 13]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [6, 7, 12]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [12, 19]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"KNL1\", \"BUB1\", \"BUB3\", \"CHK2\", \"TP53\", \"MDM2\", \"USP9X\", \"ABL1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}