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Stability of checkpoint kinase 2 is regulated via phosphorylation at serine 456

Elizabeth M Kass1, Jinwoo Ahn, Tomoaki Tanaka

  • 1Department of Biological Sciences, Columbia University, New York, New York, 10027 and Cell Signaling Technology, Inc., Danvers, Massachusetts 01923.

The Journal of Biological Chemistry
|August 24, 2007
PubMed

Insights

Checkpoint kinase 2 (Chk2) stability is regulated by phosphorylation at Ser-456, particularly after DNA damage. This phosphorylation enhances Chk2 stability and influences the apoptotic response to DNA damage.

Area of Science:

  • Molecular Biology
  • Cellular Signaling
  • DNA Damage Response

Background:

  • Checkpoint kinase 2 (Chk2) is a key protein kinase activated by DNA damage.
  • Chk2 activation involves phosphorylation at multiple sites, including Thr-68 by ATM.
  • The precise mechanisms regulating Chk2 stability and turnover are not fully understood.

Purpose of the Study:

  • To identify novel phosphorylation sites on Chk2.
  • To investigate the role of newly identified phosphorylation sites in Chk2 regulation.
  • To elucidate the impact of Chk2 phosphorylation on cellular responses to DNA damage.

Main Methods:

  • Mass spectrometry to identify Chk2 phosphorylation sites.
  • Site-directed mutagenesis (Ser-456 to Alanine).
  • Western blotting to assess Chk2 ubiquitination and stability.
  • Analysis of apoptotic response in cells expressing wild-type and mutant Chk2.

Main Results:

  • A new Chk2 phosphorylation site at Ser-456 was identified.
  • Phosphorylation of Ser-456 is crucial for Chk2 stability following DNA damage.
  • Mutation of Ser-456 to Alanine leads to Chk2 hyperubiquitination and reduced stability.
  • Cells expressing S456A Chk2 exhibit diminished apoptosis in response to DNA damage.

Conclusions:

  • Phosphorylation at Ser-456 stabilizes Chk2 protein in response to DNA damage.
  • Dephosphorylation of Ser-456 facilitates proteasome-dependent turnover of Chk2.
  • Ser-456 phosphorylation is a critical regulatory mechanism for Chk2 function and DNA damage response.

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