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PARP inhibition during alkylation-induced genotoxic stress signals a cell cycle checkpoint response mediated by ATM

Michael J Carrozza1, Donna F Stefanick, Julie K Horton

  • 1Laboratory of Structural Biology, NIEHS, National Institutes of Health, Research Triangle Park, NC 27709, USA.

DNA Repair
|September 1, 2009
PubMed

Insights

The ATM kinase is crucial for cell survival and genome stability when DNA damage occurs, especially when combined with PARP inhibition. This finding highlights ATM

Area of Science:

  • Cellular biology
  • Molecular biology
  • Genetics

Background:

  • Cell cycle checkpoints are vital for maintaining genome stability by halting cell progression upon DNA damage detection.
  • PARP inhibitors combined with methylated DNA damage induce an ATR-dependent S phase delay.
  • The role of ATM in this specific DNA damage response pathway requires further elucidation.

Purpose of the Study:

  • To investigate the involvement of ATM (Ataxia-Telangiectasia Mutated) kinase in the DNA damage response to MMS and PARP inhibition.
  • To determine the role of ATM and its downstream effector Chk2 in regulating the S phase delay and cellular sensitivity to MMS.

Main Methods:

  • Treatment of cells with methyl methanesulfonate (MMS) and a PARP inhibitor (4-AN).
  • Assessment of cell cycle progression and S phase delay.
  • Analysis of ATM, Chk2, ATR, and DNA-PK phosphorylation.
  • Utilizing genetic knockouts to study the function of ATM and Chk2.

Main Results:

  • ATM kinase activity is essential for moderating cellular sensitivity to MMS.
  • Loss of ATM or Chk2 function shortens the S phase delay induced by MMS and 4-AN.
  • ATM and Chk2 phosphorylation occurs in response to MMS and 4-AN, correlating with the S phase delay.
  • Chk2 phosphorylation is dependent on ATM, but residual phosphorylation is observed via ATR and DNA-PK.

Conclusions:

  • ATM activation is critical for preventing cell cycle progression through S phase after base excision repair initiation and PARP inhibition.
  • ATM plays a key role in protecting cells against MMS-induced cytotoxicity.
  • The findings reveal a significant role for ATM in conjunction with ATR and DNA-PK in managing DNA damage responses.

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