Role of Rad51-Mediated Interactions in Recombination
Annual summary, 1 Aug 2004-31 Jul 2005
YALE UNIV NEW HAVEN CT
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Mutations in the BRCA2 gene are linked to familial and sporadic breast cancer, yet the molecular function of BRCA2 protein remains largely obscure. BRCA2 protein physically interacts with the Rad51 recombinase, a member of the RAD52 epistasis group of proteins that mediate homologous recombination HR, a major mechanism that repairs chromosomes damaged by ionizing radiation and genotoxic agents. Accordingly, BRCA2-deficient cell lines exhibit impaired HR and sensitivity to genotoxic agents. To help define the molecular function of human BRCA2, the authors have expressed and purified a polypeptide that harbors the BRC3 and BRC4 repeat and also the DNA binding domain of this tumor suppressor. The BRC34-DBD polypeptide interacts with hRad51 and binds DNA with a distinct preference for ssDNA. Importantly, they have demonstrated by biochemical means that BRC34-DBD nucleates hRad51 onto ssDNA and enhances the homologous DNA pairing activity of hRad51. In isolation neither the BRC3-BRC4 repeats nor the DNA binding domain of BRCA2 performs these mediator functions. The biochemical system described in this study should be valuable for systematically dissecting the HR functions of BRCA2 in the context of the Rad51-mediated homologous DNA pairing reaction. Comprehending the manner in which BRCA2 modulates Rad51 activity and the functional integrity of the homologous recombination machinery could very well pave the way for devising new strategies in breast cancer diagnosis, prevention, and treatment.
- Genetic Engineering and Molecular Biology
- Medicine and Medical Research