Abstract IA20: Phosphorylation of BRCA1 by CHK2 mediates resection activity and recruitment of BRCA2

There is genetic evidence that Chk2, BRCA1 and BRCA2 are functioning in the same pathway of DNA repair, but the links between the proteins are poorly understood. We have previously shown that BRCA1's regulation of homologous recombination (HR) is dependent on Chk2-mediated phosphorylation of BRCA1 at serine 988 (BRCA1-S988). We also found that BRCA1 regulates BRCA2 recruitment in response to DNA damage, which is also dependent on the phosphorylation of BRCA1 at Serine-988. Furthermore, in HCT116/Chk2-/- cells and in MCF7 cells with depleted Chk2, the same effects on HR and BRCA2 recruitment has been found as found in cells expressing the BRCA1-S988A protein. However, in both cases, BRCA1 is recruited to chromatin and into nuclear foci, so the effect of Chk2 is not affecting the recruitment of BRCA1. BRCA1-S988A shows a defect in RPA phosphorylation in response to replication stress and DNA damage. After global DNA damage with X-rays, MRE11 foci form at double-strand breaks, and in S and G2 phases of the cell cycle, an association with CTIP is observed transiently. In the presence of BRCA1-S988A, MRE11 co-localized with CTIP persists for much longer, and results in reduced single-stranded DNA bound by RPA. In response to a site-specific DSB induced by I-SceI nuclease, BRCA1-S988A can localize to the vicinity of the break, but not directly at the broken end, as observed by chromatin immuno-precipitation. A physical assay of resection, which distinguishes single-stranded DNA fro...
Source: Molecular Cancer Research - Category: Cancer & Oncology Authors: Tags: DNA Damage Signaling: Oral Presentations - Invited Abstracts Source Type: research