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Extensive RPA2 hyperphosphorylation promotes apoptosis in response to DNA replication stress in CHK1 inhibited cells

Pedro Zuazua-Villar1, Anil Ganesh1, Geraldine Phear1

  • 1Molecular Oncology Unit, Department of Oncology, School of Medicine and Biomedical Sciences, University of Sheffield, Sheffield S10 2RX, UK.

Nucleic Acids Research
|August 15, 2015
PubMed

Insights

Replication protein A (RPA) hyperphosphorylation of RPA2 promotes cell death during replication stress when CHK1 is inhibited. This RPA2 hyperphosphorylation does not affect replication fork integrity but does reduce apoptosis when CHK1 is compromised.

Area of Science:

  • Molecular Biology
  • Cellular Biology
  • DNA Replication and Repair

Background:

  • Replication protein A (RPA)-ssDNA complexes at stalled replication forks activate the ATR-CHK1 signaling cascade.
  • CHK1 inhibition during replication stress leads to extensive RPA2 hyperphosphorylation.

Purpose of the Study:

  • To investigate the role of RPA2 hyperphosphorylation in cellular fate during CHK1 inhibition and replication stress.
  • To determine if RPA2 hyperphosphorylation protects stalled forks from collapse or apoptosis.

Main Methods:

  • Investigated recruitment of DNA repair proteins (RAD51) and phosphatases (PP4) after CHK1 and DNA synthesis inhibition.
  • Characterized cells expressing RPA2 genes mutated at key phosphorylation sites.

Main Results:

  • RPA2 hyperphosphorylation is not responsible for the lack of recruitment of RAD51 or PP4, suggesting active CHK1 is required.
  • Mutant RPA2 rescued cells from RPA2 depletion and reduced apoptosis, but did not affect double-strand breaks.

Conclusions:

  • RPA2 hyperphosphorylation promotes cell death during replication stress when CHK1 is compromised.
  • RPA2 hyperphosphorylation is not essential for maintaining replication fork integrity under these conditions.

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