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BRCA1-BARD1 complexes are required for p53Ser-15 phosphorylation and a G1/S arrest following ionizing

Megan Fabbro1, Kienan Savage, Karen Hobson

  • 1Queensland Institute of Medical Research, Post Office Royal Brisbane Hospital, Brisbane, Queensland 4029, Australia.

The Journal of Biological Chemistry
|May 26, 2004
PubMed

Insights

The BRCA1-BARD1 complex is crucial for ATM/ATR-mediated p53 phosphorylation after DNA damage, controlling cell cycle arrest. Its depletion impairs this process, highlighting its role as a DNA damage response adaptor.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Genetics

Background:

  • BRCA1 is vital for DNA damage response, and its loss increases sensitivity to damaging agents.
  • BRCA1 partners with BARD1, and they cooperate in DNA damage response pathways.

Purpose of the Study:

  • To investigate the role of the BRCA1-BARD1 complex in ATM/ATR-mediated phosphorylation of p53.
  • To determine if BRCA1-BARD1 is required for other ATM/ATR target phosphorylations and cell cycle arrest.

Main Methods:

  • Small interfering RNA (siRNA) was used to deplete BRCA1 and BARD1.
  • Western blotting was employed to detect phosphorylation of various proteins, including p53, H2AX, Chk1, and Chk2.
  • Cell cycle progression was analyzed using flow cytometry.

Main Results:

  • The BRCA1-BARD1 complex is essential for ATM/ATR-mediated phosphorylation of p53(Ser-15) after IR and UV radiation.
  • Phosphorylation of other ATM/ATR targets like H2AX, Chk1, and Chk2 does not depend on BRCA1-BARD1.
  • BRCA1-BARD1 depletion compromises IR-induced G1/S arrest by inhibiting p53(Ser-15) phosphorylation and subsequent p21 induction.

Conclusions:

  • BRCA1-BARD1 complexes function as adaptors, mediating ATM/ATR-directed p53 phosphorylation.
  • This interaction is critical for regulating G1/S cell cycle progression following DNA damage, particularly after IR.
  • The findings elucidate a specific role for BRCA1-BARD1 in the p53 signaling pathway during DNA repair.

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