期刊
CELL CYCLE
卷 14, 期 3, 页码 437-448出版社
TAYLOR & FRANCIS INC
DOI: 10.4161/15384101.2014.972901
关键词
BRCA1; cell cycle; DNA double-strand break repair; end-resection; SCF
类别
资金
- National Institutes of Health [R01CA118578]
- cancer center support grant [P30CA054174]
The BRCA1 tumor suppressor plays an important role in homologous recombination (HR)-mediated DNA double-strand-break (DSB) repair. BRCA1 is phosphorylated by Chk2 kinase upon gamma-irradiation, but the role of Chk2 phosphorylation is not understood. Here, we report that abrogation of Chk2 phosphorylation on BRCA1 delays end resection and the dispersion of BRCA1 from DSBs but does not affect the assembly of Mre11/Rad50/NBS1 (MRN) and CtIP at DSBs. Moreover, we show that BRCA1 is ubiquitinated by SCFSkp2 and that abrogation of Chk2 phosphorylation impairs its ubiquitination. Our study suggests that BRCA1 is more than a scaffold protein to assemble HR repair proteins at DSBs, but that Chk2 phosphorylation of BRCA1 also serves as a built-in clock for HR repair of DSBs. BRCA1 is known to inhibit Mre11 nuclease activity. SCFSkp2 activity appears at late G1 and peaks at S/G2, and is known to ubiquitinate phosphodegron motifs. The removal of BRCA1 from DSBs by SCFSkp2-mediated degradation terminates BRCA1-mediated inhibition of Mre11 nuclease activity, allowing for end resection and restricting the initiation of HR to the S/G2 phases of the cell cycle.
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