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An ATR- and Chk1-dependent S checkpoint inhibits replicon initiation following UVC-induced DNA damage

Timothy P Heffernan1, Dennis A Simpson, Alexandra R Frank

  • 1Department of Pathology and Laboratory Medicine, Center for Environmental Health and Susceptibility, and Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA.

Molecular and Cellular Biology
|November 26, 2002
PubMed

Insights

UV radiation triggers a DNA damage response that inhibits DNA replication initiation. This process relies on ATR and Chk1 signaling, independent of ATM, Nbs1, and Mre11 proteins.

Area of Science:

  • Cellular biology
  • Molecular genetics
  • DNA damage response

Background:

  • DNA damage response involves checkpoint mechanisms controlling DNA replication.
  • The precise role of checkpoint proteins in inhibiting DNA replication initiation after UV damage is not fully understood.

Purpose of the Study:

  • To investigate the function of checkpoint proteins in the inhibition of DNA replication initiation following UV irradiation.
  • To elucidate the signaling pathways involved in the UV-induced S checkpoint response.

Main Methods:

  • UV irradiation (254 nm) of human fibroblasts.
  • Velocity sedimentation analysis of nascent DNA.
  • Analysis of cells with genetic deficiencies in DNA repair proteins (AT, NBS).
  • Inhibition of ATR and Chk1 signaling pathways.
  • Overexpression of kinase-inactive ATR and Chk1.

Main Results:

  • Low-dose UV irradiation (1 J/m(2)) caused a 50% inhibition of DNA replication initiation in normal human fibroblasts.
  • Fibroblasts deficient in ATM or Nbs1 (AT, NBS cells) exhibited normal UV-induced inhibition of replication initiation.
  • Inhibitors of ATR and Chk1 abolished the UV-induced S checkpoint response.
  • Overexpression of kinase-inactive ATR or Chk1 reversed the UV-induced inhibition of replication initiation.

Conclusions:

  • The UV-induced S checkpoint response, leading to inhibition of DNA replication initiation, is mediated by ATR signaling through Chk1.
  • This pathway is independent of ATM, Nbs1, and Mre11.
  • ATR-Chk1 signaling is crucial for maintaining genomic stability after UV DNA damage.

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