Roles of the BLM Helicase in Homologous Recombination and DNA Repair.

摘要

In humans, homologous recombination (HR) represents a major pathway for the repair of DNA double strand breaks (DSBs), harmful lesions that can lead to genomic instability, cell death, or tumorigenesis. There is an emerging role in the HR pathway for the RecQ family of helicases. Mutation of the BLM protein, one of five RecQ helicases in humans, causes Bloom's syndrome, a rare autosomal recessive disease in which patients are predisposed to cancer, including breast cancers. Cells isolated from these patients display genomic instability and hyper-recombination. BLM protein contains a robust ATP hydrolysis activity and the ability to unwind several complex DNA structures believed to arise during HR repair, and it interacts with components of the recombination machinery, including the Rad51 recombinase. These findings suggest that BLM functions to regulate the HR pathway; however, its mechanism of action remains elusive. In the current study, we characterize the effects of purified BLM protein on the Rad51 presynpatic filament, a key intermediate in the HR repair pathway. We also address the importance of ATP hydrolysis in the role of BLM. This study begins to elucidate how BLM functions in the HR pathway, and through this role it may act to maintain genome stability and prevent cancer formation.