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DNA damage-induced activation of p53 by the checkpoint kinase Chk2

A Hirao1, Y Y Kong, S Matsuoka

  • 1The Amgen Institute, Ontario Cancer Institute, and Departments of Medical Biophysics and Immunology, University of Toronto, 620 University Avenue, Suite 706, Toronto, Ontario, M5G 2C1, Canada.

Science (New York, N.Y.)
|March 10, 2000
PubMed

Insights

Checkpoint kinase 2 (Chk2) deficiency impairs DNA damage response, affecting cell cycle arrest and p53 stabilization. This study reveals Chk2

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Genetics

Background:

  • Checkpoint kinase 2 (Chk2) is a key protein kinase activated by DNA damage.
  • Chk2 plays a role in regulating cell cycle arrest.
  • The precise mechanisms of Chk2 in DNA damage response require further elucidation.

Purpose of the Study:

  • To investigate the role of Chk2 in DNA damage-induced cell cycle arrest and apoptosis.
  • To elucidate the mechanism by which Chk2 influences p53 stability and function.
  • To determine if Chk2 directly phosphorylates p53.

Main Methods:

  • Gene targeting to generate Chk2-deficient mouse embryonic stem cells and thymocytes.
  • Gamma irradiation to induce DNA damage.
  • Analysis of cell cycle progression, apoptosis, p53 stabilization, and p53-dependent gene expression.
  • Reintroduction of the Chk2 gene to assess functional restoration.
  • In vitro phosphorylation assays.

Main Results:

  • Chk2-deficient cells failed to maintain G2 cell cycle arrest after gamma irradiation.
  • Chk2-/- thymocytes exhibited resistance to DNA damage-induced apoptosis.
  • p53 stabilization and induction of p53-dependent transcripts (e.g., p21) were defective in Chk2-/- cells.
  • Reintroduction of Chk2 restored p53-dependent transcription.
  • Chk2 directly phosphorylated p53 on serine 20, inhibiting Mdm2 binding.

Conclusions:

  • Chk2 is essential for maintaining cell cycle arrest and promoting apoptosis in response to DNA damage.
  • Chk2-deficient cells exhibit impaired p53 activation and downstream transcriptional responses.
  • Chk2-mediated phosphorylation of p53 at serine 20 is a critical mechanism for stabilizing p53 by preventing Mdm2-mediated ubiquitination and degradation.
  • These findings provide a mechanistic link between Chk2, p53 stability, and the cellular response to DNA damage.

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