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Irradiation-induced G2/M checkpoint response requires ERK1/2 activation

Y Yan1, C P Black, K H Cowan

  • 1Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198-6805, USA.

Oncogene
|February 14, 2007
PubMed

Insights

Gamma-irradiation (IR) activates extracellular signal-regulated kinases 1 and 2 (ERK1/2), inducing cell cycle arrest for DNA repair. Inhibiting ERK1/2 significantly reduces this arrest and related kinase activity, highlighting ERK1/2

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Research

Background:

  • DNA damage triggers cell cycle arrest at G2/M to allow repair.
  • G2/M checkpoint activation involves specific kinases (Wee1, Chk1) and phosphatases (Cdc25A, Cdc25C).
  • Dysregulation of cell cycle checkpoints is a hallmark of cancer.

Purpose of the Study:

  • To investigate the role of extracellular signal-regulated protein kinase 1 and 2 (ERK1/2) in gamma-irradiation (IR)-induced G2/M cell cycle arrest.
  • To elucidate the relationship between ERK1/2 signaling and key DNA damage response kinases (ATM, ATR, Chk1, Wee1) in MCF-7 cells.

Main Methods:

  • MCF-7 cells were exposed to gamma-irradiation (IR).
  • ERK1/2 signaling was inhibited using specific inhibitors.
  • Cell cycle arrest was assessed, and the activation/phosphorylation status of key cell cycle regulatory proteins (ATR, Chk1, Wee1, Cdc25A, Cdc25C, Cdc2) was analyzed.
  • ATM/ATR inhibition was achieved using caffeine or siRNA targeting ATR.

Main Results:

  • IR exposure activated ERK1/2 and induced G2/M arrest in MCF-7 cells.
  • Inhibition of ERK1/2 significantly attenuated IR-induced G2/M arrest (>85%) and reduced the activation of ATR, Chk1, and Wee1, as well as specific phosphorylation events.
  • While ATR inhibition abrogated IR-induced Chk1 phosphorylation and G2/M arrest, it did not affect IR-induced ERK1/2 activation.
  • ERK1/2 inhibition markedly reduced IR-induced ATR activity but had minimal impact on ATM activation.

Conclusions:

  • IR-induced ERK1/2 activation is a critical regulator of the G2/M checkpoint response in MCF-7 cells.
  • ERK1/2 signaling acts upstream of ATR activation in the IR-induced DNA damage response pathway.
  • These findings provide insights into the molecular mechanisms governing cell cycle control following DNA damage.

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