Affinage

CHEK1

Serine/threonine-protein kinase Chk1 · UniProt O14757

Length
476 aa
Mass
54.4 kDa
Annotated
2026-06-09
100 papers in source corpus 40 papers cited in narrative 39 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

CHEK1 (CHK1) is a serine/threonine protein kinase that couples DNA damage and replication-stress sensing to cell-cycle control, enforcing checkpoints that preserve genomic integrity during both perturbed and unperturbed proliferation (PMID:8497322, PMID:10859163). CHK1 is held in a closed, autoinhibited state by an intramolecular interaction between its N-terminal kinase domain and its distal C-terminus (critical residue Leu-449); ATR-mediated phosphorylation of the C-terminal regulatory domain, or an L449R mutation, disrupts this contact and converts CHK1 to its active conformation (PMID:14767054, PMID:27129240). Activation requires the Claspin adaptor, which binds CHK1 through phosphorylated Thr916/Ser945 to permit ATR/ATM-dependent phosphorylation at Ser317/Ser345; these sites direct distinct outputs, with Ser345 controlling cytoplasmic localization and survival and Ser317 controlling chromatin release (PMID:15707391, PMID:17242188), and the activating signal is reversed by the PPM1D (Wip1) phosphatase acting on pSer345 (PMID:15870257). Once active, CHK1 enforces the G2/M, intra-S, and spindle checkpoints by phosphorylating a broad substrate set: Cdc25C (Ser216) and the NEK11 kinase (Ser273), which drives Cdc25A degradation; Aurora-B (Ser331), promoting kinetochore error correction; p73α (Ser47) for apoptosis; and FAM122A, PRIMPOL, and Smurf1 to modulate replication-stress tolerance and cell fate (PMID:10391675, PMID:20090422, PMID:17276342, PMID:23321637, PMID:14585975, PMID:33108758, PMID:35353580, PMID:25249323). Beyond its catalytic checkpoint role, CHK1 stabilizes replication forks through a kinase-independent, PCNA-interaction-motif-dependent mechanism that promotes translesion polymerase η recruitment and PCNA ubiquitination via Claspin/Rad18 (PMID:18451105, PMID:22529391). CHK1 abundance is tightly set by competing ubiquitin systems: the SCF-Fbx6, CRL4(CDT2), and HUWE1 E3 ligases target it for proteasomal degradation, opposed by the deubiquitylases USP7 (enhanced by ZEB1) and Ataxin-3, while K63-linked ubiquitination at K132 by TRAF4 promotes chromatin association and ATR-mediated activation before removal by USP3 (PMID:19716789, PMID:23109433, PMID:31713291, PMID:25483066, PMID:25086746, PMID:28180282, PMID:29735693, PMID:32357935). CHK1 expression is itself constrained by transcriptional repressors p53/p21/pRB and BCL6 (PMID:11158294, PMID:18346918).

Mechanistic history

Synthesis pass · year-by-year structured walk · 22 steps
  1. 1993 High

    Established CHK1's foundational role by placing it as a kinase linking DNA damage sensing to the cell-cycle engine, defining the entire checkpoint-to-Cdc2 axis.

    Evidence Genetic suppressor screen and rad-mutant epistasis in fission yeast

    PMID:8497322

    Open questions at the time
    • Did not define mammalian substrates or the activating upstream kinase
    • Molecular mechanism of Cdc2 inhibition not resolved
  2. 1999 Medium

    Showed human CHK1 acts during S-to-M phase to phosphorylate Cdc25C at Ser216 independently of ATM, identifying its first direct mammalian substrate and decoupling it from the ATM arm.

    Evidence Kinase assay, cell-cycle synchronization and localization in ATM-deficient cells

    PMID:10391675

    Open questions at the time
    • Did not identify the ATM-independent activating kinase (later ATR)
    • Single substrate; broader target set unknown
  3. 2000 High

    Defined CHK1 as essential for the mammalian G2/M checkpoint and for embryonic viability, converting yeast genetics into a whole-animal loss-of-function requirement.

    Evidence Chk1-null mouse knockout with embryo cell-cycle and apoptosis analysis

    PMID:10859163

    Open questions at the time
    • Embryonic lethality precluded analysis of adult/tissue-specific roles
    • Did not separate catalytic from non-catalytic functions
  4. 2003 High

    Identified p73α (Ser47) as a CHK1-specific substrate required for apoptosis, extending CHK1 output beyond cell-cycle arrest into cell-fate decisions.

    Evidence In vitro kinase assay, S47A mutagenesis, co-IP and in vivo phosphorylation; Chk2 negative control

    PMID:14585975

    Open questions at the time
    • Physiological contexts where CHK1 favors apoptosis vs. arrest not defined
  5. 2004 High

    Resolved the activation mechanism: ATR phosphorylation of the C-terminus relieves an autoinhibitory interaction with the kinase domain, explaining how upstream signaling switches CHK1 on.

    Evidence Domain truncation, phospho-mimic mutants and interaction assays in Xenopus; 14-3-3/Rad24-Rad25 binding to phospho-CHK1 in fission yeast

    PMID:14767054 PMID:15585577

    Open questions at the time
    • Precise intramolecular contact residues not yet mapped (resolved 2016)
    • Structural basis of C-terminus/kinase-domain contact unknown at this stage
  6. 2005 High

    Defined the activation interface and its reversal: Claspin (via pThr916/pSer945) is required for ATR/ATM-dependent CHK1 phosphorylation, while PPM1D/Wip1 dephosphorylates pSer345 to terminate signaling.

    Evidence Human cell-free reconstitution with phosphopeptide competition; in vitro phosphatase assay, co-IP and checkpoint abrogation

    PMID:15707391 PMID:15870257

    Open questions at the time
    • Did not address how Claspin loading is regulated at forks
    • Other phosphatases acting on CHK1 not excluded
  7. 2007 High

    Assigned phospho-site-specific outputs (Ser345 cytoplasmic/survival, Ser317 chromatin release) and extended CHK1 into spindle/centrosome control via Aurora-B activation and Cdk-dependent centrosome amplification.

    Evidence Knock-in S317A/S345A separation-of-function mutants, subcellular fractionation; Chk1-/- DT40 cells with kinase-dead/S345A rescue and in vitro Aurora-B kinase assay

    PMID:17242188 PMID:17276342 PMID:17468739

    Open questions at the time
    • How a single kinase coordinates nuclear, cytoplasmic and centrosomal pools not fully resolved
    • Direct Aurora-B site not yet mapped (resolved 2013)
  8. 2008 High

    Uncovered a kinase-independent, Claspin-dependent arm at stressed forks where CHK1 controls PCNA ubiquitination via Rad18, and revealed CHK1 is a caspase substrate during apoptosis.

    Evidence siRNA epistasis with PCNA ubiquitination and Rad18 chromatin-binding readouts; caspase cleavage-site mapping and truncated-kinase expression

    PMID:18451105 PMID:18550533

    Open questions at the time
    • Mechanism by which CHK1 stabilizes Claspin not detailed
    • Physiological significance of the hyperactive cleavage fragment unclear
  9. 2008 Medium

    Established transcriptional control of CHEK1 by BCL6, complementing the earlier p53/p21/pRB repression circuit and showing CHK1 dosage is set at the promoter level.

    Evidence ChIP of BCL6 on the CHEK1 promoter, reporter assay and pharmacological reactivation in DLBCL

    PMID:18346918

    Open questions at the time
    • Direct relevance to checkpoint output not measured
    • Interplay with p53-axis repression not addressed
  10. 2009 High

    Defined the first dedicated E3 ligase (SCF-Fbx6) terminating checkpoint signaling by degrading CHK1, and linked the pathway to Polα-associated fork-localized activation.

    Evidence In vitro/in vivo ubiquitination with degron mapping, tumor IHC; co-IP of Polα-CHK1 with TopBP1/ATR epistasis

    PMID:19177015 PMID:19716789

    Open questions at the time
    • Whether multiple ligases act redundantly was unresolved (later: CRL4-CDT2, HUWE1)
    • Spatial coupling of Polα-CHK1 to ATR not fully defined
  11. 2010 Medium

    Connected CHK1 to Cdc25A destruction through an intermediate kinase, showing CHK1 phosphorylates NEK11 (Ser273), which in turn phosphorylates Cdc25A for beta-TrCP-mediated degradation.

    Evidence In vitro kinase assay, Cdc25A ubiquitination assay and checkpoint rescue with RNAi

    PMID:20090422

    Open questions at the time
    • Relative contribution of direct vs. NEK11-mediated Cdc25A control not quantified
  12. 2012 High

    Separated CHK1's catalytic checkpoint role from a structural fork-protection role: a kinase-independent, PCNA-interaction-motif-dependent function promotes pol η recruitment and fork progression; CRL4(CDT2) was added as a second degradation route.

    Evidence Kinase-dead/PIP-mutant and chromatin-tethered chimeras, DNA fiber and pol η foci assays; co-IP and ubiquitination with CDT2 depletion

    PMID:22529391 PMID:23109433

    Open questions at the time
    • How the kinase-independent function is regulated relative to catalytic activation unclear
    • Substrate-independent fork role mechanism only partially defined
  13. 2013 Medium

    Mapped the CHK1→Aurora-B activating site (Ser331) and showed CHK1 protects against merotelic attachments by enabling kinetochore loading of error-correction factors.

    Evidence In vitro kinase assay on Aurora-B Ser331 plus loss-of-function with MCAK/Kif2b/Mps1/Hec1 immunofluorescence

    PMID:23321637

    Open questions at the time
    • How CHK1 accesses kinetochores spatially not resolved
  14. 2014 High

    Defined the deubiquitylase axis stabilizing CHK1—USP7 (enhanced by ATM-stabilized ZEB1) and the Smurf1/RhoB apoptotic output—balancing the degradation machinery and tuning DNA-repair/radioresistance.

    Evidence In vitro/in vivo deubiquitination assays, co-IP, half-life measurement, clonogenic survival; in vitro CHK1 kinase assay on Smurf1

    PMID:25086746 PMID:25249323 PMID:25483066

    Open questions at the time
    • How DUB vs. E3 competition is dynamically resolved during stress not defined
    • Cell-type specificity of the ZEB1-USP7-CHK1 axis unclear
  15. 2016 High

    Pinned the autoinhibitory contact to residues 31–87 of the kinase domain and Leu-449 of the C-terminus, providing the structural logic for how ATR phosphorylation opens CHK1.

    Evidence FRET, BiFC, L449R and phospho-mimic mutagenesis with DNA-damage activation in cells

    PMID:27129240

    Open questions at the time
    • High-resolution structure of the full-length closed state not provided
  16. 2016 Medium

    Showed CHK1 can be activated by non-genotoxic signals: PERK/UPR triggers Claspin-dependent CHK1 activation to inhibit replication origin firing, broadening CHK1's role beyond DNA damage.

    Evidence Thapsigargin UPR induction with Claspin/CHK1 siDNA rescue and origin-firing analysis

    PMID:27375025

    Open questions at the time
    • Direct PERK-Claspin biochemical link not fully defined
  17. 2017 High

    Added Ataxin-3 as a stress-regulated CHK1 deubiquitinase that protects against CRL4A and FBXO6/CUL1 degradation and dissociates under prolonged replication stress, providing a timer for CHK1 turnover.

    Evidence Co-IP, in vitro/in vivo (de)ubiquitination, ATX3 depletion/overexpression and G2/M checkpoint assays

    PMID:28180282

    Open questions at the time
    • Signal triggering ATX3 dissociation under prolonged stress unknown
  18. 2018 High

    Defined a non-degradative ubiquitin code: TRAF4-mediated K63 ubiquitination at the active-site K132 promotes chromatin association and ATR-dependent activation, reversed by USP3, distinguishing activation-linked from degradation-linked ubiquitination.

    Evidence In vitro/in vivo ubiquitination, K132 mutagenesis, USP3 knockdown and chromatin fractionation across two studies

    PMID:29735693 PMID:32357935

    Open questions at the time
    • How K63 chromatin signal is coordinated with ATR/Claspin recruitment not fully mapped
  19. 2019 Medium

    Established CHK1 functions during unperturbed S phase: basal ATR/ETAA1-driven S296 autophosphorylation stabilizes CHK1, and ATR/CHK1 signaling restrains CDK1 to maintain RIF1-PP1 activity that limits dormant origin firing.

    Evidence S296 phospho-mutants with half-life/ubiquitylation assays; pharmacological ATR/CHK1 epistasis with RIF1-PP1 co-IP, substrate dephosphorylation and DNA fiber origin analysis; HUWE1 added as ATM/ATR/p53-independent E3

    PMID:31209037 PMID:31366665 PMID:31713291

    Open questions at the time
    • How basal vs. damage-induced CHK1 activity are discriminated mechanistically
    • Redundancy among Fbx6/CRL4-CDT2/HUWE1 in vivo not resolved
  20. 2020 High

    Linked CHK1 to phosphatase regulation and drug resistance: CHK1 phosphorylates FAM122A to activate PP2A-B55α, and loss of this control stabilizes WEE1, conferring resistance to CHK1 inhibitors.

    Evidence CRISPR knockout screen, in vitro CHK1 kinase assay on FAM122A, PP2A-B55α activity and WEE1 stability assays with WEE1-inhibitor rescue

    PMID:33108758

    Open questions at the time
    • Generality of the resistance mechanism across tumor types not established
  21. 2021 Medium

    Extended CHK1 functions beyond replication into tissue and disease contexts: a DNA-damage-independent Atr-Chek1-Cdc25 axis downstream of Piezo/NO inhibits axon regeneration, and CHEK1 drives chromosomal instability (via CEP170) and osteoclast differentiation in myeloma.

    Evidence Drosophila/mammalian neuron genetics and pharmacology; CHEK1 over/under-expression with CEP170 phosphorylation, CIN scoring, osteoclast assays and xenografts

    PMID:34090465 PMID:34158506

    Open questions at the time
    • Direct CHK1 substrates in the neuronal axis not defined
    • Mechanism coupling CHK1 to NFATc1 not biochemically resolved
  22. 2022 High

    Identified PRIMPOL as a CHK1 substrate whose phosphorylation promotes repriming and replication-stress tolerance but generates fitness-reducing single-strand gaps when constitutive, illustrating the cost-benefit of CHK1 fork signaling.

    Evidence In vitro CHK1 kinase assay on PRIMPOL, repriming and DNA fiber assays, viability assays with Claspin-driven CHK1 activation

    PMID:35353580

    Open questions at the time
    • In vivo PRIMPOL phospho-site usage and regulation not fully mapped

Open questions

Synthesis pass · forward-looking unresolved questions
  • How the multiple, partly redundant ubiquitin ligase/DUB systems and phospho-codes are integrated in real time to set CHK1 abundance, conformation, and localization for the correct checkpoint vs. fork vs. apoptotic output remains unresolved.
  • No unified quantitative model of CHK1 activation/turnover dynamics
  • Relative in vivo contributions of Fbx6, CRL4-CDT2, and HUWE1 not dissected
  • Spatial coordination of nuclear, cytoplasmic, centrosomal and chromatin pools not integrated

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 9 GO:0016740 transferase activity 6 GO:0140657 ATP-dependent activity 2
Localization
GO:0005815 microtubule organizing center 4 GO:0000228 nuclear chromosome 3 GO:0005634 nucleus 2 GO:0005654 nucleoplasm 1 GO:0005829 cytosol 1
Pathway
R-HSA-1640170 Cell Cycle 6 R-HSA-392499 Metabolism of proteins 6 R-HSA-69306 DNA Replication 5 R-HSA-73894 DNA Repair 4 R-HSA-8953897 Cellular responses to stimuli 3 R-HSA-5357801 Programmed Cell Death 2
Partners
ATRATXN3CLASPINFBXO6PCNAPPM1DTRAF4USP7

Evidence

Reading pass · 39 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1993 Fission yeast Chk1 is a protein kinase that links the DNA damage checkpoint pathway (rad1-dependent) to cell-cycle regulatory kinase p34cdc2, coupling DNA damage sensing to cell cycle arrest. Genetic screen (multicopy suppressor of cdc2 mutant), sensitivity assays with rad mutants Nature High 8497322
1995 In fission yeast, a Chk1-dependent pathway prevents mitosis when passage through 'start' (G1 commitment point) is compromised, identifying a third mitotic control checkpoint distinct from S-M and DNA-damage checkpoints. Genetic epistasis in S. pombe (chk1 deletion, rad17 deletion, cell cycle analysis with 1C DNA content) Current biology : CB Medium 8548290
1999 Human Chk1 (hChk1) is expressed specifically at S-to-M phase of the cell cycle, localizes to the nucleus during this window, and phosphorylates Cdc25C at serine 216 in the absence of DNA damage, in an ATM-independent manner. Cell cycle synchronization, kinase assay (Cdc25C phosphorylation), subcellular fractionation/localization, ATM-deficient patient cells Oncogene Medium 10391675
2000 Chk1 is required for the G2/M checkpoint in mammals; Chk1-null mouse embryos fail to arrest the cell cycle before mitosis in response to DNA replication block or DNA damage and die of apoptosis at the blastocyst stage. Targeted gene disruption in mice (Chk1−/− knockout), morphological analysis, cell cycle analysis of embryos Genes & development High 10859163
2001 p53 transcriptionally represses CHK1 through a pathway requiring p21 and the retinoblastoma protein (pRB), suggesting E2F-dependent regulation; this establishes a feedback loop where p53 reduces CHK1 protein levels. Tetracycline-inducible p53 expression, p21-null cells, pRB-null cells, Northern blot/RT-PCR for CHK1 mRNA Molecular and cellular biology Medium 11158294
2003 p73α is a direct substrate of Chk1; Chk1 phosphorylates p73α at serine 47 in vitro and in vivo upon DNA damage, and this phosphorylation is required for the apoptotic function of p73α. Chk2 does not phosphorylate p73α in vitro. Co-immunoprecipitation of endogenous proteins, in vitro kinase assay, site-directed mutagenesis (S47A), in vivo phosphorylation assay Molecular and cellular biology High 14585975
2004 ATR-mediated phosphorylation of the C-terminal regulatory domain of Chk1 relieves an autoinhibitory intramolecular interaction between the C-terminal autoinhibitory region (AIR) and the kinase domain, converting Chk1 to an active conformation. Domain truncation and coexpression in Xenopus oocytes/embryos, phospho-mimic mutations, interaction assays Molecular biology of the cell High 14767054
2004 In fission yeast, 14-3-3 proteins (Rad24/Rad25) interact with phosphorylated Chk1 after DNA damage; a leucine-rich domain mediates this interaction. 14-3-3 binding is required for Chk1 phosphorylation, nuclear accumulation upon DNA damage, and checkpoint function. Co-immunoprecipitation, site-directed mutagenesis (leucine-to-alanine), nuclear localization imaging, UV sensitivity assays Journal of cell science Medium 15585577
2005 PPM1D (Wip1) phosphatase directly binds Chk1 and dephosphorylates the ATR-targeted pSer345 site, decreasing Chk1 kinase activity and abrogating intra-S and G2/M checkpoint responses to DNA damage. Co-immunoprecipitation, in vitro phosphatase assay, kinase activity assay, checkpoint abrogation assays after UV/IR Genes & development High 15870257
2005 DNA-dependent phosphorylation of Chk1 by ATR/ATM in human cells requires Claspin, which binds Chk1 through phosphorylated residues Thr916 and Ser945 within its Chk1-binding domain. A phosphopeptide from this motif competitively inhibits the Claspin-Chk1 interaction and blocks ATR/ATM-dependent Chk1 phosphorylation. Human cell-free biochemical system, double-stranded DNA oligonucleotide-induced phosphorylation, phosphopeptide competition, kinase inhibitor panel The Biochemical journal High 15707391
2007 Chk1 is required for spindle checkpoint function; Chk1-deficient vertebrate cells show decreased Aurora-B kinase activity and impaired BubR1 phosphorylation and kinetochore localization. Chk1 directly phosphorylates Aurora-B and enhances its catalytic activity in vitro. Chk1−/− DT40 cells, RNAi knockdown, in vitro kinase assay (Chk1 phosphorylates Aurora-B), taxol/nocodazole treatment, BubR1 kinetochore localization by immunofluorescence Developmental cell High 17276342
2007 Chk1 phosphorylation at S345 is required for cytoplasmic localization and prevention of mitotic catastrophe, while S317 phosphorylation is required for chromatin release upon genotoxic stress and checkpoint activation; both sites contribute distinctly to Chk1 function. Forced centrosomal immobilization of Chk1 prevents apoptosis. Knockout-knockin system with phosphorylation-site mutants (S317A, S345A), subcellular fractionation, localization imaging, centrosomal targeting construct Molecular and cellular biology High 17242188
2007 DNA damage induces Chk1-dependent centrosome amplification (not fragmentation); kinase-dead Chk1 and the non-phosphorylatable Chk1-S345A mutant fail to restore centrosome amplification, demonstrating that both ATR signaling to Chk1 and Chk1 catalytic activity are required. Chk1−/− DT40 cells, transgenic rescue with kinase-dead and S345A mutants, light and electron microscopy, RNAi knockdown, caffeine treatment EMBO reports High 17468739
2008 Chk1 regulates DNA damage-induced PCNA ubiquitination by stabilizing Claspin, which in turn controls Rad18 ubiquitin ligase binding to chromatin; this function requires Claspin but not ATR, revealing an ATR-independent arm of Chk1 activity at stressed forks. RNAi knockdown (Chk1, Claspin, Timeless), PCNA ubiquitination assay, chromatin fractionation, Rad18-chromatin binding assay Genes & development High 18451105
2008 Chk1 is cleaved by caspases during apoptosis at Asp-299 (chicken) and Asp-299/Asp-351 (human); the N-terminal cleavage fragment (residues 1–299) has elevated kinase activity and induces abnormal nuclear morphology and H2AX phosphorylation when ectopically expressed. Caspase inhibitor experiments, mapping of cleavage sites, truncated Chk1 expression (residues 1–299), kinase assay, immunofluorescence of H2AX The Journal of biological chemistry Medium 18550533
2008 The C-terminal domain of Chk1 (S. pombe) does not simply autoinhibit the kinase; it is also required for adopting an active configuration. Intragenic suppressor mutations cluster to the substrate-binding face of the catalytic domain, suggesting the C-terminus interacts with this region. Truncation analysis, activating mutations in C-terminal domain, intragenic suppressor screen, temperature-sensitive alleles expressed from endogenous locus Molecular biology of the cell Medium 18716058
2009 The SCF E3 ubiquitin ligase containing F-box protein Fbx6 mediates ubiquitination and proteasomal degradation of Chk1 after DNA damage, exposing a C-terminal degron; this terminates checkpoint signaling. Low Fbx6 levels correlate inversely with Chk1 levels and with cancer cell resistance to camptothecin. Co-immunoprecipitation, ubiquitination assay in vitro and in vivo, siRNA knockdown, proteasome inhibitor experiments, immunohistochemistry in tumor tissues Molecular cell High 19716789
2009 DNA polymerase alpha (Polα) associates with Chk1 in native cell extracts; following replication stress, Polα-associated Chk1 is phosphorylated at Ser345 in a TopBP1- and ATR-dependent manner, and this association is required for efficient intra-S checkpoint activation. Co-immunoprecipitation from native cell extracts, siRNA depletion of Polα, ATR/TopBP1 epistasis, γH2AX measurement Cell cycle (Georgetown, Tex.) Medium 19177015
2009 Chk1 signaling causes centrosome amplification after ionizing radiation by upregulating Cdk2 activity through activating T160 phosphorylation of Cdk2; Cdk1 can substitute for Cdk2 in this pathway. Chk1−/− DT40 cells, Cdk2−/− cells, Cdk2 T160A mutant rescue, IR treatment, centrosome counting Oncogene Medium 19838212
2010 NEK11, a NIMA-related kinase, is activated by CHK1-mediated phosphorylation at Ser273 and is the critical kinase that directly phosphorylates CDC25A to trigger its beta-TrCP-mediated polyubiquitylation and degradation, linking CHK1 to CDC25A destruction. In vitro kinase assay (CHK1 phosphorylates NEK11 Ser273), CDC25A ubiquitination assay, RNAi knockdown, checkpoint rescue experiments Cell cycle (Georgetown, Tex.) Medium 20090422
2012 CHK1 is a novel substrate of the CRL4(CDT2) E3 ubiquitin ligase; CRL4(CDT2) ubiquitinates the activated form of CHK1 in the nucleoplasm in a PCNA-independent manner, targeting it for degradation. CHK1 activity maintains G2 arrest in CDT2-depleted cells. Co-immunoprecipitation, ubiquitination assay, subcellular fractionation, siRNA knockdown of CDT2, G2 arrest rescue experiments Molecular and cellular biology Medium 23109433
2012 Chk1 promotes replication fork progression after UV irradiation through a kinase-independent mechanism that requires its PCNA-interacting motif and chromatin release; this function is independent of Claspin and is required for efficient recruitment of DNA polymerase η (pol η) to replication foci for translesion synthesis. Kinase-dead Chk1 mutant, PCNA-interaction motif mutant, histone H2B-Chk1 chromatin-tethering chimera, pol η foci by immunofluorescence, DNA fiber assay Proceedings of the National Academy of Sciences of the United States of America High 22529391
2013 Chk1 protects vertebrate cells against merotelic kinetochore attachments; Chk1 phosphorylates Aurora-B at Ser331 in prometaphase, which is required for optimal kinetochore localization of MCAK, Kif2b, and Mps1 and for Hec1 phosphorylation, enabling error correction. Chk1 inhibitor/knockdown, in vitro kinase assay (Chk1 phosphorylates Aurora-B Ser331), immunofluorescence of MCAK/Kif2b/Mps1/Hec1 at kinetochores, lagging chromosome analysis Journal of cell science Medium 23321637
2014 ATM phosphorylates and stabilizes ZEB1 after DNA damage; ZEB1 then interacts with USP7 deubiquitylase and enhances USP7's ability to deubiquitylate and stabilize CHK1, promoting homologous recombination-dependent DNA repair and radioresistance. Co-immunoprecipitation (ZEB1-USP7-CHK1), ubiquitination assay, in vitro deubiquitination assay, ATM kinase assay, siRNA knockdown, clonogenic survival after radiation Nature cell biology High 25086746
2014 USP7 deubiquitylase directly stabilizes Chk1 protein levels by removing ubiquitin chains: wild-type but not catalytic-mutant USP7 deubiquitinates Chk1 in vivo and in vitro, prolongs Chk1 half-life, and this effect is independent of USP7's known effect on Claspin. Co-immunoprecipitation, in vitro and in vivo deubiquitination assay, USP7 catalytic mutant, Chk1 half-life measurement (cycloheximide chase), siRNA knockdown Cell cycle (Georgetown, Tex.) High 25483066
2014 Chk1 phosphorylates Smurf1 E3 ubiquitin ligase after DNA damage (UV/MMS), enhancing Smurf1 self-degradation, which leads to RhoB accumulation and apoptosis, defining an ATR/Chk1/Smurf1/RhoB cell fate pathway. In vitro kinase assay (Chk1 phosphorylates Smurf1), co-immunoprecipitation, ubiquitination assay, siRNA knockdown, apoptosis assay Nature communications Medium 25249323
2016 Human Chk1 maintains a closed, autoinhibited conformation through an intramolecular interaction between residues 31–87 of the N-terminal kinase domain and the distal C-terminus (critical residue Leu-449). DNA damage-induced ATR-dependent phosphorylation, or Leu-449→Arg mutation, disrupts this interaction and opens Chk1 to an active conformation. FRET, bimolecular fluorescence complementation (BiFC), site-directed mutagenesis (L449R), phospho-mimic mutations, ATR-dependent DNA damage induction The Journal of biological chemistry High 27129240
2016 PERK kinase (UPR effector) inhibits DNA replication via Claspin phosphorylation and subsequent CHK1 activation in the absence of genotoxic DNA damage; depletion of Claspin or CHK1 rescues thapsigargin-induced replication inhibition by allowing increased origin firing. Thapsigargin-induced UPR (non-genotoxic), Claspin/Chk1 siRNA knockdown, DNA synthesis assay, Chk1 phosphorylation assay, replication origin firing analysis Oncogene Medium 27375025
2017 Ataxin-3 (ATX3) interacts with Chk1 under basal and DNA damage conditions, protecting it from DDB1/CUL4A- and FBXO6/CUL1-mediated polyubiquitination and degradation. ATX3 is a deubiquitinase of Chk1; under prolonged replication stress ATX3 dissociates from Chk1, allowing its degradation. Co-immunoprecipitation (ATX3-Chk1), in vivo and in vitro ubiquitination/deubiquitination assay, siRNA of ATX3, ectopic ATX3 expression, G2/M checkpoint assay Nucleic acids research High 28180282
2018 K63-linked ubiquitination of CHK1 at K132 (active site residue) by TRAF4 promotes CHK1 chromatin association and is required for ATR-mediated CHK1 phosphorylation and activation after DNA damage; USP3 deubiquitinase removes this K63 chain, releasing CHK1 from chromatin and restoring kinase active-site accessibility. Co-immunoprecipitation, ubiquitination assay (in vitro and in vivo), site-directed mutagenesis (K132), USP3 knockdown/mutants, CHK1 chromatin fractionation Proceedings of the National Academy of Sciences of the United States of America / Journal of hematology & oncology High 29735693 32357935
2019 CHK1 stability under unperturbed proliferation is maintained by basal ATR/ETAA1-driven CHK1 autophosphorylation at S296; this autoactivatory loop opposes ubiquitylation and proteasomal degradation, thereby preserving intrinsic S-phase checkpoint functions. siRNA depletion of ATR/ETAA1, S296 phospho-mutants, cycloheximide half-life assay, ubiquitylation assay, S-phase checkpoint functional assay The Journal of cell biology Medium 31366665
2019 ATR and CHK1 kinase signaling during unperturbed S phase suppresses CDK1 activity, which stabilizes a RIF1–PP1 phosphatase interaction; this PP1 activity dephosphorylates CDC7 and CDK2 substrates to inhibit helicase assembly/activation and limit dormant origin firing. ATR/CHK1 inhibitor treatment during unperturbed replication, RIF1 Ser2205 phosphorylation assay, RIF1–PP1 co-immunoprecipitation, CDK1-dependence (CDK1 inhibitor), origin firing analysis by DNA fiber Proceedings of the National Academy of Sciences of the United States of America Medium 31209037
2019 HUWE1 (HECT E3 ubiquitin ligase) directly ubiquitinates multiple lysine residues within the Chk1 kinase domain in vitro and controls Chk1 protein stability independently of ATM, ATR, and p53; HUWE1 knockdown prolongs Chk1 half-life and rescues Chk1 loss during prolonged replication stress. In vitro ubiquitination assay with mass spectrometry site mapping, cycloheximide half-life assay, siRNA knockdown of HUWE1 vs. Cul4A, replication stress (HU/CPT) treatment The FEBS journal Medium 31713291
2020 CHK1 directly phosphorylates FAM122A/PABIR1, leading to activation of PP2A-B55α phosphatase; in CHK1-inhibited cells, loss of FAM122A phosphorylation allows PP2A-B55α to dephosphorylate and stabilize WEE1, increasing WEE1 expression, reducing replication stress, and conferring resistance to CHK1 inhibitors. CRISPR knockout screen (FAM122A), kinase assay (CHK1 phosphorylates FAM122A), PP2A-B55α activity assay, WEE1 stability assay, rescue by WEE1 inhibitor combination Molecular cell High 33108758
2021 In Drosophila sensory neurons and mammalian neurons, the Atr-Chek1-Cdc25 axis acts downstream of Piezo mechanosensitive ion channel and NO signaling (independent of DNA damage) to inhibit axon regeneration; removing Atr or Chek1, or overexpressing Cdc25, promotes regeneration. Drosophila genetic epistasis (Atr/Chek1/Cdc25 overexpression and knockdown), Piezo channel genetics, NO signaling pathway analysis, mammalian neuron pharmacological inhibition, behavioral recovery assay Nature communications Medium 34158506
2022 CHK1 directly phosphorylates PRIMPOL to promote repriming activity and replication stress tolerance; this phosphorylation is important for cellular resistance to DNA damage but promotes single-strand gap formation and reduces cell fitness when constitutively active. In vitro CHK1 kinase assay on PRIMPOL, CLASPIN overexpression to increase CHK1 activation, PRIMPOL repriming assay, DNA fiber analysis, cell viability assays Science advances High 35353580
2021 CHEK1 promotes chromosomal instability in multiple myeloma partly by phosphorylating CEP170; CHEK1 also promotes osteoclast differentiation by upregulating NFATc1 expression. CHEK1 overexpression/knockdown, Giemsa staining/exon sequencing for CIN, immunofluorescence, TRAP staining for osteoclast differentiation, xenograft model Molecular cancer Medium 34090465
2008 BCL6 transcriptional repressor directly binds a consensus element in the CHEK1 promoter and represses CHEK1 expression in normal and malignant B-cells; BCL6 peptide inhibitor (BPI) reactivates CHEK1 in DLBCL cells. Chromatin immunoprecipitation (BCL6 binds CHEK1 promoter), reporter assay, BPI treatment with CHEK1 re-expression measurement Blood cells, molecules & diseases Medium 18346918
2011 Nuclear localization of Chk1 (not centrosomal) is the critical determinant for preventing premature mitotic entry; a Chk1 mutant forced to the nucleus delays mitotic entry, while centrosome-immobilized Chk1 has little impact on mitotic timing. Conditional Chk1 knockout in MEFs, Chk1+/myc knock-in (DLD-1 cells), nuclear-targeted vs. centrosome-targeted Chk1 constructs, antibody specificity validation, live-cell mitotic entry assay Journal of cell science Medium 21628425

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 1252 12781359
1993 Fission yeast chk1 protein kinase links the rad checkpoint pathway to cdc2. Nature 417 8497322
2000 Aberrant cell cycle checkpoint function and early embryonic death in Chk1(-/-) mice. Genes & development 415 10859163
2009 Kinases that control the cell cycle in response to DNA damage: Chk1, Chk2, and MK2. Current opinion in cell biology 405 19230643
2014 ATM-mediated stabilization of ZEB1 promotes DNA damage response and radioresistance through CHK1. Nature cell biology 384 25086746
2013 Roles of Chk1 in cell biology and cancer therapy. International journal of cancer 356 23613359
2005 PPM1D dephosphorylates Chk1 and p53 and abrogates cell cycle checkpoints. Genes & development 329 15870257
2017 ATR/CHK1 inhibitors and cancer therapy. Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology 290 29054375
2010 Death by releasing the breaks: CHK1 inhibitors as cancer therapeutics. Trends in molecular medicine 228 21087899
2007 Chk1 is required for spindle checkpoint function. Developmental cell 209 17276342
2017 Targeting the ATR-CHK1 Axis in Cancer Therapy. Cancers 186 28448462
2000 Chk1 and Cds1: linchpins of the DNA damage and replication checkpoint pathways. Journal of cell science 179 11058076
2009 The F box protein Fbx6 regulates Chk1 stability and cellular sensitivity to replication stress. Molecular cell 153 19716789
2015 LY2606368 Causes Replication Catastrophe and Antitumor Effects through CHK1-Dependent Mechanisms. Molecular cancer therapeutics 150 26141948
2004 Chk1 in the DNA damage response: conserved roles from yeasts to mammals. DNA repair 150 15279789
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 142 17242188
2013 CHEK again: revisiting the development of CHK1 inhibitors for cancer therapy. Pharmacology & therapeutics 138 24140082
2015 MiR-195 suppresses non-small cell lung cancer by targeting CHEK1. Oncotarget 136 25840419
1999 Cell-cycle-dependent and ATM-independent expression of human Chk1 kinase. Oncogene 133 10391675
2008 Thymoquinone triggers inactivation of the stress response pathway sensor CHEK1 and contributes to apoptosis in colorectal cancer cells. Cancer research 124 18632613
2020 Reality CHEK: Understanding the biology and clinical potential of CHK1. Cancer letters 122 32991949
2015 Trial Watch: Targeting ATM-CHK2 and ATR-CHK1 pathways for anticancer therapy. Molecular & cellular oncology 122 27308506
2004 Knockdown of Chk1, Wee1 and Myt1 by RNA interference abrogates G2 checkpoint and induces apoptosis. Cancer biology & therapy 118 14726685
2019 An ATR and CHK1 kinase signaling mechanism that limits origin firing during unperturbed DNA replication. Proceedings of the National Academy of Sciences of the United States of America 117 31209037
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
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
2008 Chk1 and Claspin potentiate PCNA ubiquitination. Genes & development 94 18451105
2015 Cancer-Specific Synthetic Lethality between ATR and CHK1 Kinase Activities. Cell reports 91 26748709
2005 DNA-dependent phosphorylation of Chk1 and Claspin in a human cell-free system. The Biochemical journal 83 15707391
2008 BCL6 represses CHEK1 and suppresses DNA damage pathways in normal and malignant B-cells. Blood cells, molecules & diseases 81 18346918
2011 CHK1 inhibitors in combination chemotherapy: thinking beyond the cell cycle. Molecular interventions 78 21540473
2011 Unleashing Chk1 in cancer therapy. Cell cycle (Georgetown, Tex.) 77 21610326
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
2021 Clinical Candidates Targeting the ATR-CHK1-WEE1 Axis in Cancer. Cancers 72 33672884
2009 Regulation of chk1. Cell division 71 19400965
2006 Chk1 inhibitors for novel cancer treatment. Anti-cancer agents in medicinal chemistry 68 16842237
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
2021 CHEK1 and circCHEK1_246aa evoke chromosomal instability and induce bone lesion formation in multiple myeloma. Molecular cancer 63 34090465
2018 53BP1 Mediates ATR-Chk1 Signaling and Protects Replication Forks under Conditions of Replication Stress. Molecular and cellular biology 61 29378830
2012 CRL4(CDT2) targets CHK1 for PCNA-independent destruction. Molecular and cellular biology 59 23109433
2023 New horizons in lung cancer management through ATR/CHK1 pathway modulation. Future medicinal chemistry 57 37877252
2021 An extending ATR-CHK1 circuitry: the replication stress response and beyond. Current opinion in genetics & development 57 34329853
2014 The fork and the kinase: a DNA replication tale from a CHK1 perspective. Mutation research. Reviews in mutation research 54 25795119
1995 The chk1 pathway is required to prevent mitosis following cell-cycle arrest at 'start'. Current biology : CB 51 8548290
2020 CHK1 Inhibitor Blocks Phosphorylation of FAM122A and Promotes Replication Stress. Molecular cell 50 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
2022 CHK1 phosphorylates PRIMPOL to promote replication stress tolerance. Science advances 48 35353580
2017 Synthetic Lethality Interaction Between Aurora Kinases and CHEK1 Inhibitors in Ovarian Cancer. Molecular cancer therapeutics 48 28847989
2014 Chk1 as a new therapeutic target in triple-negative breast cancer. Breast (Edinburgh, Scotland) 48 24636978
2020 Oocyte Elimination Through DNA Damage Signaling from CHK1/CHK2 to p53 and p63. Genetics 47 32273296
2003 Hyperoxia activates the ATR-Chk1 pathway and phosphorylates p53 at multiple sites. American journal of physiology. Lung cellular and molecular physiology 47 12959929
2021 The Atr-Chek1 pathway inhibits axon regeneration in response to Piezo-dependent mechanosensation. Nature communications 46 34158506
2017 Ataxin-3 promotes genome integrity by stabilizing Chk1. Nucleic acids research 46 28180282
2019 Direct regulation of Chk1 protein stability by E3 ubiquitin ligase HUWE1. The FEBS journal 43 31713291
2015 Topotecan synergizes with CHEK1 (CHK1) inhibitor to induce apoptosis in ovarian cancer cells. BMC cancer 42 25884494
2016 CHK1 Inhibition Radiosensitizes Head and Neck Cancers to Paclitaxel-Based Chemoradiotherapy. Molecular cancer therapeutics 41 27422809
2014 ATR/Chk1/Smurf1 pathway determines cell fate after DNA damage by controlling RhoB abundance. Nature communications 41 25249323
2022 APE1 assembles biomolecular condensates to promote the ATR-Chk1 DNA damage response in nucleolus. Nucleic acids research 40 36200829
2014 DNA-PKcs is required to maintain stability of Chk1 and Claspin for optimal replication stress response. Nucleic acids research 39 24500207
2016 PERK inhibits DNA replication during the Unfolded Protein Response via Claspin and Chk1. Oncogene 38 27375025
2012 Kinase-independent function of checkpoint kinase 1 (Chk1) in the replication of damaged DNA. Proceedings of the National Academy of Sciences of the United States of America 38 22529391
2009 DNA damage induces Chk1-dependent threonine-160 phosphorylation and activation of Cdk2. Oncogene 38 19838212
2005 Checkpoint kinase 1 (CHK1) protein and mRNA expression is downregulated in aggressive variants of human lymphoid neoplasms. Leukemia 37 15526025
2016 CHK1 and RAD51 activation after DNA damage is regulated via urokinase receptor/TLR4 signaling. Cell death & disease 36 27685627
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
2006 Targeted gene repair activates Chk1 and Chk2 and stalls replication in corrected cells. DNA repair 35 16414312
2019 Basal CHK1 activity safeguards its stability to maintain intrinsic S-phase checkpoint functions. The Journal of cell biology 33 31366665
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 33 24838526
2021 A combination of PARP and CHK1 inhibitors efficiently antagonizes MYCN-driven tumors. Oncogene 32 34508175
2004 The relative contribution of CHK1 and CHK2 to Adriamycin-induced checkpoint. Experimental cell research 32 15707569
2012 Chk1 and Wee1 kinases coordinate DNA replication, chromosome condensation, and anaphase entry. Molecular biology of the cell 31 22262459
2009 Replication stress activates DNA polymerase alpha-associated Chk1. Cell cycle (Georgetown, Tex.) 31 19177015
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
2020 HOTAIR promotes paclitaxel resistance by regulating CHEK1 in ovarian cancer. Cancer chemotherapy and pharmacology 29 32743678
2011 Nuclear Chk1 prevents premature mitotic entry. Journal of cell science 29 21628425
2010 Chk1 suppressed cell death. Cell division 29 20813042
2008 Regulation of Chk1 by its C-terminal domain. Molecular biology of the cell 29 18716058
2020 Ubiquitination of the DNA-damage checkpoint kinase CHK1 by TRAF4 is required for CHK1 activation. Journal of hematology & oncology 28 32357935
2013 Upregulation of the ATR-CHEK1 pathway in oral squamous cell carcinomas. Genes, chromosomes & cancer 28 24142626
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
2006 Chk1- and claspin-dependent but ATR/ATM- and Rad17-independent DNA replication checkpoint response in HeLa cells. Cancer research 26 16951182
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
2013 Chk1 and Mps1 jointly regulate correction of merotelic kinetochore attachments. Journal of cell science 25 23321637
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
2019 Synergism Through WEE1 and CHK1 Inhibition in Acute Lymphoblastic Leukemia. Cancers 23 31717700
2014 Novel insights into Chk1 regulation by phosphorylation. Cell structure and function 23 25748360
2016 Conformational Change of Human Checkpoint Kinase 1 (Chk1) Induced by DNA Damage. The Journal of biological chemistry 22 27129240

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