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UV-induced replication arrest in the xeroderma pigmentosum variant leads to DNA double-strand breaks, gamma -H2AX

Charles L Limoli1, Erich Giedzinski, William M Bonner

  • 1Department of Radiation Oncology, University of California, San Francisco, CA 94103-0806,USA. limoli@itsa.ucsf.edu

Proceedings of the National Academy of Sciences of the United States of America
|January 5, 2002
PubMed

Insights

UV radiation causes replication arrest in xeroderma pigmentosum variant (XPV) cells, leading to DNA double-strand breaks (DSBs) and Mre11/Rad50/Nbs1 complex accumulation at stalled forks. This suggests DSBs form during replication arrest in XPV cells.

Area of Science:

  • Molecular Biology
  • Genetics
  • DNA Repair

Background:

  • Xeroderma pigmentosum variant (XPV) cells exhibit impaired bypass replication of UV-induced DNA damage.
  • UV irradiation stalls replication forks, leading to DNA damage signaling pathways.

Purpose of the Study:

  • To investigate the formation of DNA double-strand breaks (DSBs) during UV-induced replication arrest in XPV cells.
  • To characterize the spatiotemporal relationship between Mre11/Rad50/Nbs1 complex and gamma-H2AX foci after UV irradiation in XPV cells.

Main Methods:

  • UV irradiation of XPV and normal cells.
  • Immunofluorescence microscopy to detect Mre11 and gamma-H2AX foci.
  • Analysis of foci formation, colocalization, and correlation with UV fluence and time post-irradiation.

Main Results:

  • UV-induced replication arrest in XPV cells leads to accumulation of Mre11/Rad50/Nbs1 complex and gamma-H2AX at stalled forks.
  • A fluence-dependent increase in Mre11 and gamma-H2AX foci was observed in XPV cells after UV irradiation.
  • Mre11 and gamma-H2AX foci colocalized spatially and showed a one-to-one correspondence in UV-irradiated XPV cells, unlike in x-irradiated cells.

Conclusions:

  • XPV cells develop DNA double-strand breaks (DSBs) during UV-induced replication arrest.
  • These UV-induced DSBs in XPV cells may contribute to genetic instability due to inefficient bypass replication of UV damage.

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