Affinage

CHEK1

Serine/threonine-protein kinase Chk1 · UniProt O14757

Length
476 aa
Mass
54.4 kDa
Annotated
2026-04-28
100 papers in source corpus 38 papers cited in narrative 38 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

CHEK1 encodes a serine/threonine checkpoint kinase that serves as a central effector of the DNA damage and replication stress response, coupling upstream ATR signaling to cell cycle arrest, replication fork stabilization, and DNA repair. ATR phosphorylates CHEK1 at S317 and S345 — relieving C-terminal autoinhibition and enabling kinase activation — with Claspin acting as an essential adaptor; S317 phosphorylation controls chromatin release and replication fork progression, while S345 phosphorylation governs cell survival, cytoplasmic/centrosomal localization, and 14-3-3 binding (PMID:12415000, PMID:14767054, PMID:17242188, PMID:19091954, PMID:15279790). Active CHEK1 enforces S-phase and G2/M checkpoints principally by phosphorylating CDC25 phosphatases (directly and via NEK11-mediated CDC25A degradation), and phosphorylates additional substrates including p73α (apoptosis), PRIMPOL (repriming at stalled forks), FAM122A (PP2A-B55α activation and WEE1 stabilization), SYK(L) (tumor suppression), and CK1δ (PMID:9278510, PMID:20090422, PMID:35353580, PMID:33108758, PMID:22585575, PMID:23861943). CHEK1 protein stability is tightly controlled by opposing ubiquitin ligases (SCF-Fbx6, CRL4-CDT2, HUWE1) and deubiquitinases (USP7, USP3, Ataxin-3), while its expression is transcriptionally repressed by the p53–p21–RB axis, and its maturation requires Hsp90/Cdc37 chaperoning (PMID:19716789, PMID:23109433, PMID:31713291, PMID:25483066, PMID:29735693, PMID:28180282, PMID:11158294, PMID:16330544).

Mechanistic history

Synthesis pass · year-by-year structured walk · 23 steps
  1. 1997 High

    Identifying the downstream checkpoint effector of Chk1: genetic epistasis and co-immunoprecipitation established Cdc25 phosphatase — not Wee1 — as the key target through which Chk1 enforces G2 arrest, founding the Chk1→Cdc25 signaling paradigm.

    Evidence Fission yeast Δcdc25 epistasis, in vivo co-IP and phosphorylation assay

    PMID:9278510

    Open questions at the time
    • Phosphorylation sites on Cdc25 not mapped in this study
    • Mechanism of Chk1 activation itself unknown at this stage
  2. 1999 High

    Extending the Chk1→Cdc25 axis to meiotic regulation: Chk1 maintains prophase I arrest in Xenopus oocytes by phosphorylating Cdc25C, demonstrating that this checkpoint kinase controls cell cycle transitions beyond the DNA damage context.

    Evidence Xenopus oocyte microinjection of dominant-negative Chk1, neutralizing antibody, and Cdc25C phospho-site mutant

    PMID:10068474

    Open questions at the time
    • Endogenous Chk1 activation mechanism during meiosis not defined
    • Vertebrate in vivo validation not yet performed
  3. 2000 High

    Establishing mammalian essentiality: Chk1 knockout mice die at the blastocyst stage with failure of G2/M checkpoint arrest and apoptosis, proving that Chk1 is indispensable for mammalian cell viability and checkpoint function.

    Evidence Targeted gene disruption in mice, cell cycle analysis of Chk1−/− blastocysts

    PMID:10859163

    Open questions at the time
    • Whether lethality reflects checkpoint loss or an essential role in unperturbed replication not distinguished
    • Downstream substrates in mammalian cells not identified
  4. 2001 High

    Discovering transcriptional regulation of CHEK1: p53 represses CHEK1 transcription through p21 and pRB, revealing a negative feedback loop where the DNA damage response attenuates its own checkpoint kinase.

    Evidence Tet-regulated p53 expression in p21-null and pRB-deficient cells, Northern/Western blotting

    PMID:11158294

    Open questions at the time
    • Whether E2F sites directly mediate CHK1 promoter repression not shown
    • Kinetics of feedback loop during checkpoint recovery not characterized
  5. 2002 High

    Defining the activation mechanism: ATR-dependent phosphorylation at S345 directly stimulates Chk1 kinase activity and enables 14-3-3 (Rad24) binding, establishing ATR→Chk1 phosphorylation as the activating signal.

    Evidence S345A mutagenesis, phospho-specific antibodies, in vitro kinase assay, co-IP with Rad24 in fission yeast

    PMID:12415000

    Open questions at the time
    • Role of S317 not yet addressed
    • Structural basis of activation unknown
  6. 2004 High

    Elucidating the autoinhibition mechanism and the roles of adaptor proteins: the C-terminal regulatory domain contains an autoinhibitory region relieved by ATR phosphorylation, while Claspin was identified as an essential adaptor required for ATR-dependent Chk1 phosphorylation, and 14-3-3 binding regulates Chk1 nuclear localization.

    Evidence Domain deletion/phospho-mimic mutagenesis in Xenopus (autoinhibition); co-IP and RNAi/depletion in Xenopus and human cells (Claspin); leucine-to-alanine mutagenesis and localization microscopy in fission yeast (14-3-3)

    PMID:14767054 PMID:15279790 PMID:15585577

    Open questions at the time
    • Structural details of autoinhibition at atomic resolution not resolved
    • How Claspin specifically presents Chk1 to ATR not defined
  7. 2005 High

    Establishing Chk1 as an Hsp90 client: in vitro reconstitution with purified chaperones (Hsp90, Hsp70, Hsp40, Cdc37, CK2) converted inactive Chk1 to active kinase, showing that Chk1 folding and maturation depend on the Hsp90 chaperone machinery.

    Evidence In vitro reconstitution with purified chaperones, kinase activity assay, Hsp90 inhibitor treatment in cells

    PMID:16330544

    Open questions at the time
    • Whether Hsp90 is required constitutively or only for de novo folding not resolved
    • Structural basis of C-terminal domain–Hsp90 interaction not defined
  8. 2005 High

    Extending Chk1 checkpoint function to the metaphase-anaphase transition: Drosophila Grp/Chk1 delays anaphase onset in response to DSBs independently of the spindle assembly checkpoint, broadening the cell cycle stages controlled by this kinase.

    Evidence Genetic analysis of Drosophila grp mutants with site-specific I-CreI DSBs, comparison with BubR1 mutants

    PMID:15723794

    Open questions at the time
    • Anaphase-delay substrates of Chk1 not identified
    • Whether this mechanism operates in mammalian cells not tested
  9. 2007 High

    Separating the dual functions of S317 and S345 phosphorylation: S317 controls chromatin release and replication fork progression, while S345 governs centrosomal localization, cell survival, and DNA-damage-induced centrosome amplification — genetically separable essential and checkpoint functions of Chk1.

    Evidence Knockout-knockin of S317A and S345A mutants in Chk1-null DT40 and human cells, subcellular fractionation, centrosome microscopy, checkpoint assays

    PMID:17242188 PMID:17468739 PMID:19091954

    Open questions at the time
    • How S345 phosphorylation promotes centrosome localization mechanistically not defined
    • Centrosomal substrate(s) of Chk1 not identified
  10. 2003 High

    Identifying substrates beyond Cdc25: Chk1 phosphorylates p73α at S47 to activate its apoptotic function, linking the DNA damage checkpoint to p53-family-mediated apoptosis.

    Evidence Co-IP, in vitro kinase assay, S47A mutagenesis, transactivation assay

    PMID:14585975

    Open questions at the time
    • In vivo relevance of p73α phosphorylation in tumor suppression not demonstrated genetically
  11. 2008 High

    Revealing caspase-mediated Chk1 activation during apoptosis and refining the C-terminal domain's dual role: caspase cleavage at D299/D351 generates a hyperactive N-terminal kinase fragment, while endogenous-locus mutagenesis showed the C-terminal domain is required for both autoinhibition and for adopting a fully active conformation.

    Evidence Caspase inhibitor treatment and truncation expression in U2OS (cleavage); endogenous-locus truncation and intragenic suppressor mapping in fission yeast (C-terminal dual function)

    PMID:18550533 PMID:18716058

    Open questions at the time
    • Physiological significance of caspase-cleaved Chk1 fragment during apoptosis progression not established in vivo
    • Full-length structural basis of the activating conformation not resolved
  12. 2009 High

    Defining ubiquitin-mediated Chk1 turnover and upstream regulators: SCF-Fbx6 was identified as an E3 ligase targeting the Chk1 C-terminus for proteasomal degradation to terminate checkpoint signaling; Chk1 was found to physically associate with DNA Polα for rapid activation; APC/Cdh1 controls the Claspin–Chk1 axis by targeting Claspin for degradation.

    Evidence Co-IP and ubiquitination assays (Fbx6); co-IP with Polα depletion of individual polymerases (Polα); AP-MS and Cdh1 depletion (APC/Cdh1-Claspin)

    PMID:19177015 PMID:19477924 PMID:19716789

    Open questions at the time
    • Relative contributions of SCF-Fbx6 versus CRL4-CDT2 in different cell cycle phases not resolved
    • Polα–Chk1 interaction awaits structural characterization
  13. 2010 High

    Establishing the CHK1→NEK11→CDC25A degradation cascade: CHK1 phosphorylates NEK11 at S273, which in turn phosphorylates CDC25A to trigger β-TrCP-mediated ubiquitylation, defining an ordered kinase relay for checkpoint-mediated CDC25A destruction.

    Evidence Phosphorylation assays, NEK11 depletion forcing mitotic entry, CDC25A phosphorylation site identification

    PMID:20090422

    Open questions at the time
    • Whether NEK11 is the sole or predominant intermediate for CDC25A degradation not resolved
    • In vivo validation in animal models not performed
  14. 2012 High

    Expanding the substrate repertoire and identifying compartment-specific degradation: Chk1 phosphorylates SYK(L) at S295 promoting its degradation to support tumor growth; CRL4(CDT2) ubiquitinates active Chk1 in the nucleoplasm in a PCNA-independent manner, while CRL1 degrades Chk1 in the cytoplasm.

    Evidence In vitro kinase assay and tumor models (SYK(L)); co-IP, ubiquitination assay, subcellular fractionation, CDT2 depletion (CRL4-CDT2)

    PMID:22585575 PMID:23109433

    Open questions at the time
    • Whether SYK(L) phosphorylation by CHK1 occurs in normal tissues or only cancer contexts
    • How CRL4-CDT2 distinguishes active from inactive Chk1 not mechanistically defined
  15. 2013 High

    Identifying CK1δ as a direct Chk1 substrate: Chk1 phosphorylates CK1δ at four sites, inhibiting its kinase activity and establishing a cross-talk node between checkpoint and casein kinase signaling.

    Evidence In vitro kinase assay, MS phosphosite identification, CK1δ mutant kinetics, co-IP, cellular Chk1 activation

    PMID:23861943

    Open questions at the time
    • Physiological consequence of CK1δ inhibition by Chk1 in cell cycle control not demonstrated
  16. 2014 High

    Defining the deubiquitinase network that stabilizes Chk1: USP7 directly deubiquitinates Chk1 independently of Claspin, ZEB1 enhances USP7-mediated Chk1 stabilization downstream of ATM, and the HERC2–USP20–Claspin axis provides an ATR-dependent mechanism for stabilizing Claspin to promote Chk1 activation; additionally, Tra2α/β control constitutive splicing of CHEK1 exons.

    Evidence In vitro/in vivo deubiquitination assays with WT vs catalytic-dead USP7; ATM kinase assay on ZEB1 with HR repair assay; HERC2-USP20-Claspin co-IP and ubiquitination assays; dual Tra2 siRNA depletion with RNA-seq and CHK1 protein readout

    PMID:25086746 PMID:25208576 PMID:25326330 PMID:25483066

    Open questions at the time
    • Relative importance of USP7 vs USP3 vs Ataxin-3 in different checkpoint phases not compared
    • DNA-PKcs role in Claspin–Chk1 complex stability was shown in a single study
  17. 2017 High

    Identifying Ataxin-3 as a third Chk1 deubiquitinase: Ataxin-3 directly deubiquitinates Chk1, protecting it from both DDB1/CUL4A and FBXO6/CUL1 pathways under normal and stressed conditions.

    Evidence Co-IP, in vitro and in vivo deubiquitination assay, ATX3 knockdown, G2/M checkpoint and cell survival assays

    PMID:28180282

    Open questions at the time
    • Whether polyglutamine expansion in Ataxin-3 (SCA3 disease) impairs Chk1 stabilization not tested
    • Chain-type specificity of Ataxin-3 on Chk1 not determined
  18. 2018 High

    Revealing K63-linked ubiquitin regulation of Chk1 chromatin dynamics: USP3 removes K63-linked ubiquitin from K132 in the Chk1 active site, controlling both chromatin release and substrate accessibility — a non-degradative ubiquitin signal regulating Chk1 function.

    Evidence USP3 WT and catalytic-dead/NLS-deficient mutants, K63-linkage-specific ubiquitination assay, chromatin fractionation, CHK1 phosphorylation readout

    PMID:29735693

    Open questions at the time
    • E3 ligase responsible for K63 ubiquitination of Chk1 K132 not identified
    • Structural model of how K132 ubiquitination occludes the active site not available
  19. 2019 High

    Identifying HUWE1 as an additional E3 ligase for Chk1: HUWE1 directly ubiquitinates Chk1 at multiple kinase-domain lysines independently of ATM, ATR, and p53, controlling basal and stress-induced Chk1 turnover.

    Evidence In vitro ubiquitination with HUWE1, ubiquitinated-lysine identification, HUWE1 knockdown, protein half-life measurement

    PMID:31713291

    Open questions at the time
    • Functional redundancy among SCF-Fbx6, CRL4-CDT2, and HUWE1 for Chk1 degradation not resolved
  20. 2020 High

    Connecting Chk1 to PP2A regulation via FAM122A: Chk1 phosphorylates FAM122A, relieving its inhibition of PP2A-B55α; this establishes a mechanism whereby Chk1 activity controls WEE1 stability through phosphatase activation, and FAM122A loss confers resistance to Chk1 inhibitors.

    Evidence In vitro CHK1 kinase assay on FAM122A, CRISPR knockout, PP2A-B55α activity assays, WEE1 stability measurement, CHK1 inhibitor resistance assays

    PMID:33108758

    Open questions at the time
    • Whether FAM122A phosphorylation by CHK1 occurs in all cell types or is context-specific
    • Direct phosphorylation sites on FAM122A and their individual contributions not fully mapped
  21. 2021 High

    Uncovering a non-canonical function in neuronal regeneration: the ATR–Chk1 pathway inhibits axon regeneration downstream of Piezo-mediated mechanosensation and NO signaling, independent of DNA damage; genetic removal or pharmacological inhibition promotes regeneration in Drosophila and mouse.

    Evidence Drosophila Atr/Chek1 mutant and Piezo mutant epistasis, mouse sensory neuron-specific conditional KO, pharmacological inhibition, behavioral recovery assays

    PMID:34158506

    Open questions at the time
    • Chk1 substrates mediating axon regeneration inhibition not identified
    • Whether mechanosensory activation of ATR-Chk1 occurs in other non-dividing cell types unknown
  22. 2022 High

    Identifying PRIMPOL as a direct Chk1 substrate and defining upstream condensate-based ATR activation: Chk1 phosphorylates PRIMPOL to promote repriming at stalled forks (at the cost of gap formation); APE1 nucleolar condensates recruit ATR/TopBP1/ETAA1 to activate ATR-Chk1 signaling; TRIM21 antagonizes Claspin chromatin loading via K63-linked ubiquitination, attenuating Chk1 activation.

    Evidence In vitro CHK1 kinase assay on PRIMPOL with replication/gap assays; APE1 condensate formation and in vitro ATR kinase assay; TRIM21 catalytic-mutant with linkage-specific ubiquitination and CHK1 phosphorylation readout

    PMID:35048968 PMID:35353580 PMID:36200829

    Open questions at the time
    • Specific phosphorylation sites on PRIMPOL and their individual roles not fully resolved
    • Whether APE1 condensate-based ATR activation is the dominant mode in vivo not established
    • Relative contribution of TRIM21 vs other regulators to Claspin turnover not compared
  23. 2013 High

    Pim kinases provide a non-canonical Chk1 activation input: Pim1/2 phosphorylate CHK1 at S280 in FLT3-ITD AML cells, promoting cell cycle and drug resistance functions independent of ATR.

    Evidence In vitro Pim1 kinase assay, RNAi/pharmacological inhibition, S280A mutant, patient sample validation

    PMID:23748345

    Open questions at the time
    • Whether S280 phosphorylation alters Chk1 substrate specificity not defined
    • Generalizability beyond FLT3-ITD AML context not demonstrated

Open questions

Synthesis pass · forward-looking unresolved questions
  • Key unresolved questions include: (1) the full structural basis of C-terminal autoinhibition relief and substrate engagement at atomic resolution; (2) the relative contributions and temporal ordering of multiple E3 ligases and deubiquitinases in regulating Chk1 abundance during different cell cycle phases; (3) the identity of Chk1 substrates at centrosomes and during axon regeneration; (4) how K63-linked ubiquitination at K132 and K48-linked degradation are coordinated.
  • No high-resolution structure of full-length autoinhibited or activated Chk1
  • Substrate specificity determinants for Chk1 not comprehensively defined
  • Centrosomal and neuronal substrates remain unidentified

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 12 GO:0098772 molecular function regulator activity 4
Localization
GO:0005634 nucleus 3 GO:0005815 microtubule organizing center 3 GO:0005694 chromosome 2 GO:0005829 cytosol 2 GO:0005730 nucleolus 1
Pathway
R-HSA-73894 DNA Repair 8 R-HSA-1640170 Cell Cycle 7 R-HSA-162582 Signal Transduction 4 R-HSA-69306 DNA Replication 4 R-HSA-5357801 Programmed Cell Death 3
Partners
ATXN3CDC25ACLSPNFBXO6NEK11PRIMPOLUSP3USP7

Evidence

Reading pass · 38 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1997 Chk1 targets Cdc25 phosphatase (not Wee1) in the DNA damage checkpoint: Cdc25 associated with Chk1 in vivo and was phosphorylated in Chk1 complexes; fission yeast cells lacking cdc25 were insensitive to Chk1 and irradiation, establishing Cdc25 as the key downstream target of Chk1 for G2 arrest. Genetic epistasis (cdc2-3w Δcdc25 cells), in vivo co-immunoprecipitation, in vivo phosphorylation assay Science High 9278510
1999 Xenopus Chk1 maintains prophase I arrest in oocytes by phosphorylating and inhibiting Cdc25C, thereby preventing Cdc2 activation; dominant-negative Chk1 or neutralizing anti-Chk1 antibody facilitated progesterone-induced release from arrest, and a Chk1-nonphosphorylatable Cdc25C mutant bypassed the inhibition. Oocyte microinjection (dominant-negative mutant, neutralizing antibody), Cdc25C phosphorylation-site mutagenesis Developmental Biology High 10068474
2000 Chk1 is essential for mammalian G2 checkpoint and cell survival: Chk1−/− mouse embryos failed to arrest the cell cycle before mitosis in response to DNA replication block or DNA damage, exhibiting nuclear abnormalities and apoptosis at the blastocyst stage. Targeted gene disruption (knockout mice), cell cycle analysis of Chk1−/− blastocysts Genes & Development High 10859163
2001 p53 down-regulates CHK1 transcription through p21 and the retinoblastoma protein (pRB): induction of p53 caused marked reduction in CHK1 mRNA and protein; p21 was required and sufficient for CHK1 repression; pRB was also required, implicating E2F-dependent transcription. Tet-regulated p53 expression, p21-deficient cells, pRB-deficient cells, Northern/Western blotting Molecular and Cellular Biology High 11158294
2002 ATR-dependent phosphorylation of Chk1 at Ser345 activates Chk1 kinase activity and is required for checkpoint-mediated cell cycle arrest; S345 phosphorylation is also required for Chk1 association with the 14-3-3 protein Rad24 upon DNA damage. Site-directed mutagenesis (S345A), phospho-specific antibodies, in vitro kinase assay, co-immunoprecipitation with Rad24 Journal of Cell Science High 12415000
2003 p73α is a direct substrate of Chk1: endogenous Chk1 phosphorylates p73α at Ser47 in vitro and in vivo upon DNA damage; this phosphorylation is required for the apoptotic function of p73α, and endogenous p73α co-immunoprecipitates with Chk1. Co-immunoprecipitation, in vitro kinase assay, site-directed mutagenesis (S47A), transactivation assay Molecular and Cellular Biology High 14585975
2004 The C-terminal regulatory domain of Xenopus Chk1 contains an autoinhibitory region (AIR) that interacts intramolecularly with the kinase domain; ATR-mediated phosphorylation of the C-terminal domain relieves this autoinhibition, providing a conformational mechanism for Chk1 activation. Domain deletion/mutagenesis, co-expression in Xenopus oocytes/embryos, kinase domain interaction assays, phospho-mimic mutations Molecular Biology of the Cell High 14767054
2004 Claspin associates with Chk1 upon replication stress and DNA damage and is required for ATR-dependent Chk1 activation in both Xenopus and human systems, acting as an essential adaptor for Chk1 activation in the checkpoint pathway. Co-immunoprecipitation, RNAi/depletion, checkpoint activation assays in Xenopus and human cells DNA Repair High 15279790
2005 Chk1 is an Hsp90 client kinase: inhibition of Hsp90 destabilizes Chk1, and in vitro chaperoning with purified Hsp90, Hsp70, Hsp40, Cdc37, and CK2 converts bacterially expressed Chk1 to an active kinase. The C-terminal regulatory domain of Chk1 affects association with Hsp90. In vitro reconstitution with purified chaperones, kinase activity assay, Hsp90 inhibitor treatment in cells Journal of Biological Chemistry High 16330544
2005 Drosophila Grp/Chk1 DNA damage checkpoint controls the metaphase/anaphase transition: Chk1 (Grp), but not the spindle checkpoint component BubR1, is required for delayed anaphase onset in response to site-specific double-strand breaks in neuroblasts. Genetic analysis using Drosophila grp mutants, I-CreI endonuclease-induced site-specific DSBs, comparison with BubR1 spindle checkpoint mutants Current Biology High 15723794
2007 DNA damage induces Chk1-dependent centrosome amplification: inhibition of Chk1 by RNAi, drug treatment, or kinase-dead/S345A mutation suppressed DNA-damage-induced centrosome amplification, demonstrating that Chk1 catalytic activity and ATR-mediated Chk1 phosphorylation are required. RNAi knockdown, Chk1 inhibitor treatment, Chk1−/− DT40 cells with transgenic rescue, kinase-dead and S345A mutants, light/electron microscopy EMBO Reports High 17468739
2007 ATR-dependent phosphorylation of Chk1 at S317 and S345 have distinct functions: S317 phosphorylation is required for chromatin release and replication fork progression, while S345 phosphorylation is required for cell survival and cytoplasmic localization; centrosomal localization of Chk1 (dependent on S345) is linked to prevention of apoptosis. Knockout-knockin system with Chk1-null cells, S317A and S345A point mutants, subcellular fractionation, checkpoint assays, centrosome localization by immunofluorescence Molecular and Cellular Biology High 17242188
2008 Chk1 is activated by caspase-dependent cleavage during apoptosis: active caspases cleave Chk1 at Asp299 (and Asp351 in human), generating an N-terminal fragment with elevated kinase activity; expression of this fragment induces abnormal nuclear morphology and H2AX phosphorylation. Caspase inhibitor treatment, identification of cleavage sites, expression of truncated Chk1 (residues 1–299) in U2OS cells, kinase activity assay Journal of Biological Chemistry High 18550533
2008 The C-terminal domain of Chk1 is not simply autoinhibitory but also contains regions critical for adopting an active configuration: truncation inactivates Chk1 in vivo, specific C-terminal mutations activate Chk1 without requiring phosphorylation, and intragenic suppressors map to the substrate-binding face of the kinase domain. Endogenous locus truncation in fission yeast, site-directed mutagenesis, intragenic suppressor mapping Molecular Biology of the Cell High 18716058
2008 Chk1 promotes activation of Cdk2 after ionizing radiation via Thr160 phosphorylation: in Chk1−/− DT40 cells, radiation-induced Cdk2 activation was absent; this was independent of Cdk2/cyclin protein levels and linked to Chk1-dependent centrosome amplification. Chk1−/− DT40 cells, Cdk2−/− cells, T160A Cdk2 mutant rescue experiments, kinase activity assays Oncogene High 19838212
2008 Essential function of Chk1 requires S345 phosphorylation during unperturbed mitosis (initiated at centrosomes), while S317 mutation abrogates DNA damage checkpoint, replication fork progression, and fork stalling but does not affect viability; these two functions are genetically separable. Gene targeting to introduce S317A and S345A point mutations into endogenous human CHK1 locus, cell viability assays, DNA fiber analysis, checkpoint assays PNAS High 19091954
2009 Fbx6, an F-box protein in the SCF E3 ligase complex, mediates ubiquitination and proteasomal degradation of Chk1 after DNA damage by recognizing a degron-like region at the Chk1 C-terminus, thereby terminating the replication checkpoint. Co-immunoprecipitation, ubiquitination assay in cells, siRNA knockdown, protein half-life analysis, analysis of Fbx6/Chk1 levels in cancer cell lines and tumor tissues Molecular Cell High 19716789
2009 Chk1 physically associates with DNA Polymerase alpha; depletion of DNA Polα (but not Polε or Polδ) induces ATR-dependent Chk1 Ser345 phosphorylation. Polα-associated Chk1 is rapidly phosphorylated on Ser345 in a TopBP1- and ATR-dependent manner following replication stress. Co-immunoprecipitation from cell extracts, siRNA depletion of individual polymerases, phospho-specific Western blotting, γH2AX analysis Cell Cycle Medium 19177015
2009 Pim1/2 kinases (not Akt) phosphorylate CHK1 at Ser280 in FLT3-ITD acute myeloid leukemia cells, as demonstrated by in vitro kinase assay with Pim1 and pharmacological/RNAi inhibition; Ser280 phosphorylation facilitated CHK1 cell cycle and resistance functions. In vitro kinase assay, pharmacological inhibition, RNAi, ectopic expression of Pim1/2, Ser280Ala mutant expression, patient sample validation Leukemia High 23748345
2009 APC/Cdh1 regulates the Claspin/Chk1 pathway: Claspin is a Cdh1 ubiquitin substrate identified by affinity purification/mass spectrometry; inactivation of Cdh1 leads to Claspin stabilization and consequent activation of Chk1. Affinity purification coupled with mass spectrometry, ubiquitination assay, Cdh1 depletion, Claspin/Chk1 activation readouts Molecular Biology of the Cell High 19477924
2010 NEK11 is a kinase that links CHK1 to CDC25A degradation: CHK1 activates NEK11 by phosphorylating it at Ser273; NEK11 then directly phosphorylates CDC25A on residues required for β-TrCP-mediated polyubiquitylation and degradation, establishing the CHK1→NEK11→CDC25A axis. Phosphorylation assays, NEK11 inhibition/depletion forcing cells into mitosis, identification of CDC25A phosphorylation sites Cell Cycle High 20090422
2012 CHK1 phosphorylates SYK(L) tumor suppressor at Ser295, promoting its subsequent proteasomal degradation in hepatocellular carcinoma; expression of a non-phosphorylatable SYK(L) S295 mutant was more efficient at suppressing tumor growth. In vitro kinase assay, phosphorylation site identification, proteasomal degradation assay, non-phosphorylatable mutant expression, tumor growth assays Journal of Clinical Investigation High 22585575
2012 CRL4(CDT2) ubiquitinates and degrades the activated form of CHK1 in the nucleoplasm in a PCNA-independent manner, providing a mechanism to terminate G2 cell cycle arrest; both CRL1 and CRL4 ubiquitinate CHK1 but in distinct cellular compartments. Co-immunoprecipitation, ubiquitination assay, CDT2 depletion, subcellular fractionation, CHK1 inhibitor rescue experiments Molecular and Cellular Biology High 23109433
2013 Chk1 phosphorylates CK1δ at Ser328, Ser331, Ser370, and Thr397; CK1δ co-precipitates with Chk1 from cell extracts, and cellular Chk1 activation leads to decreased CK1δ kinase activity. In vitro kinase assay, mass spectrometry identification of phosphorylation sites, CK1δ mutant kinetics, co-immunoprecipitation from cell extracts, cellular Chk1 activation PLoS One High 23861943
2014 USP7 deubiquitinase directly controls Chk1 protein stability: USP7 depletion or inhibition reduces Chk1 levels; wild-type but not catalytic-mutant USP7 deubiquitinates Chk1 in vivo and in vitro, extends Chk1 half-life, and this effect is independent of USP7's known effect on Claspin. USP7 knockdown/inhibition, overexpression of WT vs catalytic-mutant USP7, in vitro and in vivo deubiquitination assay, protein half-life analysis Cell Cycle High 25483066
2014 ZEB1 interacts with USP7 and enhances its deubiquitylation and stabilization of CHK1, thereby promoting homologous recombination-dependent DNA repair; ATM phosphorylates and stabilizes ZEB1 in response to DNA damage, linking ATM to CHK1 via ZEB1-USP7. Co-immunoprecipitation, deubiquitylation assay, ATM kinase assay on ZEB1, HR repair assay, radioresistance in vitro and in vivo Nature Cell Biology High 25086746
2014 HERC2 regulates USP20 stability under normal conditions; upon replication stress, ATR phosphorylates USP20, causing dissociation from HERC2; USP20 then deubiquitinates K48-linked polyubiquitinated Claspin, stabilizing it and promoting CHK1 phosphorylation and checkpoint activation. Co-immunoprecipitation, ubiquitination assay, ATR phosphorylation assay, USP20 depletion, Claspin stability assay, CHK1 phosphorylation readout Nucleic Acids Research High 25326330
2014 DNA-PKcs is required to maintain Chk1-Claspin complex stability and Claspin transcription; in the absence of DNA-PKcs, ATR-dependent Chk1 phosphorylation and Chk1 signaling are compromised, resulting in a defective intra-S checkpoint. DNA-PKcs-deficient cells, co-immunoprecipitation of Chk1-Claspin complex, phospho-Chk1 Western blotting, cell cycle checkpoint analysis Nucleic Acids Research Medium 24500207
2017 Ataxin-3 (ATX3) is a deubiquitinase of Chk1 that interacts with Chk1 and protects it from DDB1/CUL4A- and FBXO6/CUL1-mediated polyubiquitination and degradation under normal and DNA damage conditions; ATX3 deficiency reduces Chk1 abundance and impairs DNA damage response. Co-immunoprecipitation, deubiquitination assay in vivo and in vitro, ATX3 knockdown, G2/M checkpoint assay, cell survival after replication stress Nucleic Acids Research High 28180282
2018 USP3 deubiquitinase removes K63-linked ubiquitin chains from Chk1 at K132 (within the kinase active site); USP3 knockdown elevates K63-linked ubiquitination, prolonging CHK1 chromatin association and phosphorylation. USP3 has a dual role: releasing CHK1 from chromatin and opening the active site for substrate accessibility. USP3 knockdown/overexpression with WT and catalytic-dead or NLS-deficient mutants, K63-linked ubiquitination assay, CHK1 chromatin association assay, phosphorylation assay PNAS High 29735693
2019 HUWE1 HECT E3 ubiquitin ligase directly ubiquitinates Chk1 at multiple lysine residues within the kinase domain and controls Chk1 protein stability independently of ATM, ATR, and p53; HUWE1 knockdown markedly prolongs Chk1 half-life and prevents Chk1 degradation under replication stress. In vitro ubiquitination assay with HUWE1, identification of ubiquitinated lysines, HUWE1 knockdown, protein half-life measurement, comparison with CUL4A depletion FEBS Journal High 31713291
2020 CHK1 directly phosphorylates FAM122A (PABIR1), leading to activation of the PP2A-B55α phosphatase; FAM122A knockout activates PP2A-B55α, which dephosphorylates WEE1 and rescues it from ubiquitin-mediated degradation, reducing replication stress and conferring resistance to CHK1 inhibitors. CRISPR knockout of FAM122A, CHK1 in vitro kinase assay on FAM122A, PP2A-B55α activity assays, WEE1 stability measurements, CHK1 inhibitor resistance assays Molecular Cell High 33108758
2021 The ATR-Chek1 pathway inhibits axon regeneration in response to Piezo-dependent mechanosensation: in Drosophila sensory neurons, removing Atr or Chek1 promotes regeneration while overexpression impedes it; Atr responds to mechanical stimulus via Piezo and downstream NO signaling, independent of DNA damage. Sensory neuron-specific Atr knockout in adult mice or pharmacological ATR-Chk1 inhibition enhances axon regeneration. Drosophila genetics (Atr/Chek1 mutants, Cdc25 knockdown/overexpression), Piezo mutant analysis, mouse sensory neuron-specific conditional KO, pharmacological ATR-Chk1 inhibition in vitro and in vivo, behavioral recovery assays Nature Communications High 34158506
2022 TRIM21 E3 ligase directly interacts with and ubiquitinates Claspin via K63-linked ubiquitin chains, counteracting K6-linked ubiquitination required for Claspin-TIPIN interaction and chromatin loading; TRIM21 overexpression (but not catalytic-inactive mutant) compromises CHK1 activation, leading to replication fork instability. Co-immunoprecipitation, K63/K6 linkage-specific ubiquitination assays, TRIM21 catalytic mutant, Claspin-TIPIN interaction assay, chromatin loading assay, CHK1 phosphorylation readout, replication fork stability assay Nucleic Acids Research High 35048968
2022 CHK1 directly phosphorylates PRIMPOL to promote repriming during replication stress, enabling replication elongation; CHK1 phosphorylation of PRIMPOL is important for cellular resistance to DNA damage but promotes single-strand gap formation. In vitro CHK1 kinase assay on PRIMPOL, CLASPIN overexpression to modulate CHK1 activation, replication elongation assay, gap formation assay, DNA damage resistance assay Science Advances High 35353580
2014 Tra2α and Tra2β RNA-binding proteins jointly control constitutive splicing of CHEK1 exons; simultaneous depletion of both Tra2 proteins reduces full-length CHK1 protein levels, causing DNA damage marker γH2AX accumulation and decreased cell viability. Dual Tra2α/Tra2β siRNA depletion, RNA-seq splicing analysis, Western blotting for CHK1 protein, γH2AX immunostaining, cell viability assay Nature Communications Medium 25208576
2004 Interaction of 14-3-3 proteins with phosphorylated Chk1 regulates Chk1 nuclear localization after DNA damage in fission yeast: a leucine-rich domain in Chk1 mediates 14-3-3 binding; mutations disrupting 14-3-3 interaction prevent Chk1 phosphorylation, nuclear accumulation, and confer UV sensitivity. Co-immunoprecipitation, leucine-to-alanine mutagenesis, localization by microscopy, UV sensitivity assay, identification of nuclear import/export sequences Journal of Cell Science Medium 15585577
2022 APE1 promotes ATR-Chk1 DDR signaling by assembling biomolecular condensates in nucleoli that recruit ATR and its activators TopBP1 and ETAA1; APE1 can directly activate ATR to phosphorylate Chk1 in vitro, dependent on its N-terminal motif required for condensate assembly. siRNA knockdown, APE1 overexpression with domain mutants, in vitro ATR kinase assay, co-localization with NPM1, condensate formation assay in vitro, W119R mutant analysis Nucleic Acids Research High 36200829

Source papers

Stage 0 corpus · 100 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2003 Chk1 and Chk2 kinases in checkpoint control and cancer. Cancer cell 1251 12781359
2010 The ATM-Chk2 and ATR-Chk1 pathways in DNA damage signaling and cancer. Advances in cancer research 1018 21034966
1997 Cdc25 mitotic inducer targeted by chk1 DNA damage checkpoint kinase. Science (New York, N.Y.) 482 9278510
2000 Aberrant cell cycle checkpoint function and early embryonic death in Chk1(-/-) mice. Genes & development 415 10859163
2014 ATM-mediated stabilization of ZEB1 promotes DNA damage response and radioresistance through CHK1. Nature cell biology 380 25086746
2013 Roles of Chk1 in cell biology and cancer therapy. International journal of cancer 352 23613359
2017 ATR/CHK1 inhibitors and cancer therapy. Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology 282 29054375
2010 Death by releasing the breaks: CHK1 inhibitors as cancer therapeutics. Trends in molecular medicine 228 21087899
2017 Targeting the ATR-CHK1 Axis in Cancer Therapy. Cancers 184 28448462
2005 Chk1 and p21 cooperate to prevent apoptosis during DNA replication fork stress. Molecular biology of the cell 159 16280359
2009 The F box protein Fbx6 regulates Chk1 stability and cellular sensitivity to replication stress. Molecular cell 152 19716789
2004 Chk1 in the DNA damage response: conserved roles from yeasts to mammals. DNA repair 150 15279789
2015 LY2606368 Causes Replication Catastrophe and Antitumor Effects through CHK1-Dependent Mechanisms. Molecular cancer therapeutics 149 26141948
2001 p53 down-regulates CHK1 through p21 and the retinoblastoma protein. Molecular and cellular biology 146 11158294
2007 Specific role of Chk1 phosphorylations in cell survival and checkpoint activation. Molecular and cellular biology 140 17242188
2015 MiR-195 suppresses non-small cell lung cancer by targeting CHEK1. Oncotarget 136 25840419
2013 CHEK again: revisiting the development of CHK1 inhibitors for cancer therapy. Pharmacology & therapeutics 136 24140082
2002 Phosphorylation activates Chk1 and is required for checkpoint-mediated cell cycle arrest. Journal of cell science 133 12415000
1998 Analysis of Rad3 and Chk1 protein kinases defines different checkpoint responses. The EMBO journal 133 9857181
2008 Thymoquinone triggers inactivation of the stress response pathway sensor CHEK1 and contributes to apoptosis in colorectal cancer cells. Cancer research 124 18632613
2015 Trial Watch: Targeting ATM-CHK2 and ATR-CHK1 pathways for anticancer therapy. Molecular & cellular oncology 122 27308506
2020 Reality CHEK: Understanding the biology and clinical potential of CHK1. Cancer letters 115 32991949
2012 CHK1 targets spleen tyrosine kinase (L) for proteolysis in hepatocellular carcinoma. The Journal of clinical investigation 107 22585575
2015 A Synergistic Interaction between Chk1- and MK2 Inhibitors in KRAS-Mutant Cancer. Cell 106 26140595
2008 The multiple checkpoint functions of CHK1 and CHK2 in maintenance of genome stability. Frontiers in bioscience : a journal and virtual library 106 18508566
2008 Essential function of Chk1 can be uncoupled from DNA damage checkpoint and replication control. Proceedings of the National Academy of Sciences of the United States of America 105 19091954
2007 DNA damage induces Chk1-dependent centrosome amplification. EMBO reports 98 17468739
2013 Characterization and preclinical development of LY2603618: a selective and potent Chk1 inhibitor. Investigational new drugs 96 24114124
2015 Cancer-Specific Synthetic Lethality between ATR and CHK1 Kinase Activities. Cell reports 90 26748709
2011 CHK1 inhibitors in combination chemotherapy: thinking beyond the cell cycle. Molecular interventions 78 21540473
2018 MiR-126 negatively regulates PLK-4 to impact the development of hepatocellular carcinoma via ATR/CHEK1 pathway. Cell death & disease 74 30315225
2014 USP7 controls Chk1 protein stability by direct deubiquitination. Cell cycle (Georgetown, Tex.) 74 25483066
2005 Chaperoning checkpoint kinase 1 (Chk1), an Hsp90 client, with purified chaperones. The Journal of biological chemistry 74 16330544
2021 Clinical Candidates Targeting the ATR-CHK1-WEE1 Axis in Cancer. Cancers 71 33672884
2014 STAT3 interrupts ATR-Chk1 signaling to allow oncovirus-mediated cell proliferation. Proceedings of the National Academy of Sciences of the United States of America 71 24639502
2009 Regulation of chk1. Cell division 70 19400965
2004 Regulation of Chk1 kinase by autoinhibition and ATR-mediated phosphorylation. Molecular biology of the cell 67 14767054
2004 Claspin, a regulator of Chk1 in DNA replication stress pathway. DNA repair 67 15279790
2003 p73alpha regulation by Chk1 in response to DNA damage. Molecular and cellular biology 67 14585975
2010 Targeting the checkpoint kinase Chk1 in cancer therapy. Cell cycle (Georgetown, Tex.) 65 20023404
2018 53BP1 Mediates ATR-Chk1 Signaling and Protects Replication Forks under Conditions of Replication Stress. Molecular and cellular biology 61 29378830
2021 CHEK1 and circCHEK1_246aa evoke chromosomal instability and induce bone lesion formation in multiple myeloma. Molecular cancer 60 34090465
2019 Silencing Long Non-coding RNA LINC01224 Inhibits Hepatocellular Carcinoma Progression via MicroRNA-330-5p-Induced Inhibition of CHEK1. Molecular therapy. Nucleic acids 60 31902747
2012 CRL4(CDT2) targets CHK1 for PCNA-independent destruction. Molecular and cellular biology 58 23109433
2009 Cdh1 regulates cell cycle through modulating the claspin/Chk1 and the Rb/E2F1 pathways. Molecular biology of the cell 58 19477924
2023 New horizons in lung cancer management through ATR/CHK1 pathway modulation. Future medicinal chemistry 56 37877252
2014 HERC2/USP20 coordinates CHK1 activation by modulating CLASPIN stability. Nucleic acids research 54 25326330
2005 The Drosophila Grp/Chk1 DNA damage checkpoint controls entry into anaphase. Current biology : CB 53 15723794
2021 An extending ATR-CHK1 circuitry: the replication stress response and beyond. Current opinion in genetics & development 52 34329853
2014 Human Tra2 proteins jointly control a CHEK1 splicing switch among alternative and constitutive target exons. Nature communications 51 25208576
1995 The chk1 pathway is required to prevent mitosis following cell-cycle arrest at 'start'. Current biology : CB 51 8548290
2008 Expanded roles for Chk1 in genome maintenance. The Journal of biological chemistry 50 18424430
2006 The Chk1/Cdc25A pathway as activators of the cell cycle in neuronal death induced by camptothecin. The Journal of neuroscience : the official journal of the Society for Neuroscience 50 16928871
2020 CHK1 Inhibitor Blocks Phosphorylation of FAM122A and Promotes Replication Stress. Molecular cell 49 33108758
2007 Cross-talk between Chk1 and Chk2 in double-mutant thymocytes. Proceedings of the National Academy of Sciences of the United States of America 49 17360434
2001 DNA damage: Chk1 and Cdc25, more than meets the eye. Current opinion in genetics & development 49 11163155
2017 Synthetic Lethality Interaction Between Aurora Kinases and CHEK1 Inhibitors in Ovarian Cancer. Molecular cancer therapeutics 48 28847989
2010 Cooperative functions of Chk1 and Chk2 reduce tumour susceptibility in vivo. The EMBO journal 47 20834228
2003 Hyperoxia activates the ATR-Chk1 pathway and phosphorylates p53 at multiple sites. American journal of physiology. Lung cellular and molecular physiology 47 12959929
2022 TRIM21 suppresses CHK1 activation by preferentially targeting CLASPIN for K63-linked ubiquitination. Nucleic acids research 46 35048968
2021 The Atr-Chek1 pathway inhibits axon regeneration in response to Piezo-dependent mechanosensation. Nature communications 45 34158506
2020 Oocyte Elimination Through DNA Damage Signaling from CHK1/CHK2 to p53 and p63. Genetics 45 32273296
2017 Ataxin-3 promotes genome integrity by stabilizing Chk1. Nucleic acids research 45 28180282
2022 CHK1 phosphorylates PRIMPOL to promote replication stress tolerance. Science advances 43 35353580
2019 Direct regulation of Chk1 protein stability by E3 ubiquitin ligase HUWE1. The FEBS journal 42 31713291
2015 Topotecan synergizes with CHEK1 (CHK1) inhibitor to induce apoptosis in ovarian cancer cells. BMC cancer 42 25884494
1999 Involvement of Chk1 kinase in prophase I arrest of Xenopus oocytes. Developmental biology 42 10068474
2016 CHK1 Inhibition Radiosensitizes Head and Neck Cancers to Paclitaxel-Based Chemoradiotherapy. Molecular cancer therapeutics 41 27422809
2014 DNA-PKcs is required to maintain stability of Chk1 and Claspin for optimal replication stress response. Nucleic acids research 39 24500207
2009 DNA damage induces Chk1-dependent threonine-160 phosphorylation and activation of Cdk2. Oncogene 38 19838212
2007 grp (chk1) replication-checkpoint mutations and DNA damage trigger a Chk2-dependent block at the Drosophila midblastula transition. Development (Cambridge, England) 38 17409117
2015 Wee1 is required to sustain ATR/Chk1 signaling upon replicative stress. Oncotarget 37 25965828
2013 CK1δ kinase activity is modulated by Chk1-mediated phosphorylation. PloS one 37 23861943
2022 APE1 assembles biomolecular condensates to promote the ATR-Chk1 DNA damage response in nucleolus. Nucleic acids research 36 36200829
2004 Interaction of 14-3-3 protein with Chk1 affects localization and checkpoint function. Journal of cell science 36 15585577
2008 Cleavage-mediated activation of Chk1 during apoptosis. The Journal of biological chemistry 35 18550533
2008 Dual regulation of Cdc25A by Chk1 and p53-ATF3 in DNA replication checkpoint control. The Journal of biological chemistry 34 19060337
2014 Gemcitabine and CHK1 inhibition potentiate EGFR-directed radioimmunotherapy against pancreatic ductal adenocarcinoma. Clinical cancer research : an official journal of the American Association for Cancer Research 32 24838526
2021 A combination of PARP and CHK1 inhibitors efficiently antagonizes MYCN-driven tumors. Oncogene 31 34508175
2004 The relative contribution of CHK1 and CHK2 to Adriamycin-induced checkpoint. Experimental cell research 31 15707569
2018 Deubiquitinating enzyme USP3 controls CHK1 chromatin association and activation. Proceedings of the National Academy of Sciences of the United States of America 30 29735693
2014 Targeting CDC25C, PLK1 and CHEK1 to overcome Docetaxel resistance induced by loss of LZTS1 in prostate cancer. Oncotarget 30 24525428
2013 Pim kinases phosphorylate Chk1 and regulate its functions in acute myeloid leukemia. Leukemia 30 23748345
2009 Replication stress activates DNA polymerase alpha-associated Chk1. Cell cycle (Georgetown, Tex.) 30 19177015
2020 HOTAIR promotes paclitaxel resistance by regulating CHEK1 in ovarian cancer. Cancer chemotherapy and pharmacology 28 32743678
2015 Pharmacological inactivation of CHK1 and WEE1 induces mitotic catastrophe in nasopharyngeal carcinoma cells. Oncotarget 28 26025928
2014 Increasing cisplatin sensitivity by schedule-dependent inhibition of AKT and Chk1. Cancer biology & therapy 28 25482935
2013 Upregulation of the ATR-CHEK1 pathway in oral squamous cell carcinomas. Genes, chromosomes & cancer 28 24142626
2008 Regulation of Chk1 by its C-terminal domain. Molecular biology of the cell 28 18716058
2020 Combination of CHEK1/2 inhibition and ionizing radiation results in abscopal tumor response through increased micronuclei formation. Oncogene 27 32335582
2014 γH2AX and Chk1 phosphorylation as predictive pharmacodynamic biomarkers of Chk1 inhibitor-chemotherapy combination treatments. BMC cancer 27 24996846
2010 NEK11: linking CHK1 and CDC25A in DNA damage checkpoint signaling. Cell cycle (Georgetown, Tex.) 26 20090422
2017 BRCA1 or CDK12 loss sensitizes cells to CHK1 inhibitors. Tumour biology : the journal of the International Society for Oncodevelopmental Biology and Medicine 25 29025359
2008 Alterations of Chk1 and Chk2 expression in colon cancer. International journal of colorectal disease 25 18679694
2015 Suppression of CHK1 by ETS Family Members Promotes DNA Damage Response Bypass and Tumorigenesis. Cancer discovery 24 25653093
2019 FANCM, RAD1, CHEK1 and TP53I3 act as BRCA-like tumor suppressors and are mutated in hereditary ovarian cancer. Cancer genetics 23 31078449
2014 Novel insights into Chk1 regulation by phosphorylation. Cell structure and function 23 25748360
2020 Exploring the Synergy between PARP and CHK1 Inhibition in Matched BRCA2 Mutant and Corrected Cells. Cancers 22 32260355
2019 Synergism Through WEE1 and CHK1 Inhibition in Acute Lymphoblastic Leukemia. Cancers 22 31717700
2019 The clinical significance of CHEK1 in breast cancer: a high-throughput data analysis and immunohistochemical study. International journal of clinical and experimental pathology 22 31933717