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Phosphorylation activates Chk1 and is required for checkpoint-mediated cell cycle arrest
Holly Capasso1, Carmela Palermo, Shanhong Wan
1Department of Pharmacology, UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
Journal of Cell Science
|November 5, 2002
Summary
Fission yeast Chk1 protein kinase is phosphorylated at serine 345 (S345) after DNA damage, which is essential for cell cycle delay and survival. This S345 phosphorylation increases Chk1 activity and is conserved across species.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- The protein kinase Chk1 is crucial for cell cycle delay in response to DNA damage in fission yeast.
- Loss of the chk1 gene leads to sensitivity to DNA damaging agents due to lack of cell cycle delay.
Purpose of the Study:
- To investigate the role of Chk1 phosphorylation, specifically at serine 345 (S345), in the DNA damage response pathway.
- To determine how S345 phosphorylation affects Chk1 kinase activity, cell cycle checkpoint, and cellular survival.
Main Methods:
- Utilized mutagenesis and phospho-specific antibodies to study Chk1 phosphorylation at S345 in vivo.
- Developed a kinase assay to measure Chk1 activity following DNA damage.
- Investigated the association of Chk1 with Rad24 (a 14-3-3 protein) upon DNA damage.
Main Results:
- DNA damage induces Chk1 phosphorylation at S345, which is required for an intact checkpoint response.
- Chk1 kinase activity increases upon DNA damage, dependent on S345 phosphorylation.
- S345 phosphorylation is necessary for Chk1 to associate with Rad24 after DNA damage.
Conclusions:
- Chk1 phosphorylation at S345 leads to increased kinase activity, essential for DNA damage-induced cell cycle delay and survival.
- The mechanism of Chk1 activation by DNA damage appears conserved between yeast, mammals, and Xenopus.