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BRCA1 Forms a Functional Complex with γ-H2AX as a Late Response to Genotoxic Stress
Susan A Krum1, Esther de la Rosa Dalugdugan, Gustavo A Miranda-Carboni
1Molecular Biology Institute, Jonsson Comprehensive Cancer Center, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
Journal of Nucleic Acids
|October 12, 2010
Summary
BRCA1 forms a complex with phosphorylated H2AX (γ-H2AX) at DNA damage sites. This complex helps reduce the DNA repair signal by ubiquitylating H2AX, indicating BRCA1
Area of Science:
- DNA repair mechanisms
- Cellular response to genotoxic stress
- Biochemistry of DNA damage signaling
Background:
- Genotoxic stress triggers histone H2AX phosphorylation to form γ-H2AX.
- BRCA1, a tumor suppressor, is recruited to DNA damage sites and co-localizes with γ-H2AX.
- The exact role of BRCA1 recruitment and its interaction with γ-H2AX remain unclear.
Purpose of the Study:
- To investigate the biochemical interaction between BRCA1 and γ-H2AX after DNA damage.
- To elucidate the functional significance of BRCA1-γ-H2AX complex formation in DNA repair signaling.
Main Methods:
- Formation and characterization of an acid-stable BRCA1-γ-H2AX chromatin complex.
- Assessment of H2AX ubiquitination in vivo and its dependence on BRCA1.
- Analysis of γ-H2AX levels upon inhibition of proteasome function and BRCA1 depletion.
Main Results:
- BRCA1 and γ-H2AX form a stable biochemical complex on chromatin post-DNA damage.
- BRCA1-γ-H2AX complex formation correlates with decreased γ-H2AX levels during late-stage repair.
- H2AX ubiquitination at Lys119/120 was observed in vivo, and proteasome inhibition stabilized γ-H2AX.
- Reduced BRCA1 levels diminished H2AX ubiquitination and increased persistent γ-H2AX.
Conclusions:
- BRCA1 is recruited to form stable complexes with γ-H2AX at DNA damage sites.
- The BRCA1-γ-H2AX complex plays a role in attenuating the γ-H2AX DNA repair signal.
- BRCA1-mediated ubiquitination of H2AX contributes to the resolution of the DNA damage response.
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