A protein phosphatase feedback mechanism regulates the basal phosphorylation of Chk2 kinase in the absence of DNA damage

Luigi Carlessi, Giacomo Buscemi, Enrico Fontanella, Domenico Delia

Research output: Contribution to journalArticlepeer-review

Abstract

The checkpoint kinase Chk2 is an effector component of the ATM-dependent DNA damage response (DDR) pathway. The activation of Chk2 by genotoxic stress involves its phosphorylation on T68 by ATM and additional auto/transphosphorylations. Here we demonstrate that in unperturbed cells, chemical inhibition of Chk2 by VRX0466617 (VRX) enhances the phosphorylation of Chk2-T68 throughout the cell cycle phases. This event, dependent on the presence of ATM and catalytically functional Chk2, is not consequential to DNA damage, as neither γ-H2AX nuclear foci nor increased ATM activation is detected in VRX-treated cells, suggesting the involvement of other regulatory proteins. As serine/threonine protein phosphatases (PPs) regulate the phosphorylation and deactivation of proteins of the DDR pathway, we analyzed their role in phospho-T68-Chk2 regulation. We found that intracellular inhibition of PP1 and PP2A-like activities by okadaic acid markedly raised the accumulation of Chk2-pT68 without DNA damage induction, and this phenomenon was also seen when PP1-C, PP2A-C, and Wip1/PPM1D were simultaneously knockdown by siRNA. Altogether, these data indicate a novel mechanism in undamaged cells where PPs function to maintain the balance between ATM and its direct substrate Chk2 through a regulatory circuit.

Original languageEnglish
Pages (from-to)1213-1223
Number of pages11
JournalBiochimica et Biophysica Acta - Molecular Cell Research
Volume1803
Issue number10
DOIs
Publication statusPublished - Oct 2010

Keywords

  • Cell cycle checkpoints
  • Chk2
  • DNA damage responses
  • Kinase inhibitors
  • Protein phosphatases

ASJC Scopus subject areas

  • Cell Biology
  • Molecular Biology
  • Medicine(all)

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