Determining the effects of RAD51C ovarian cancer variants

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Project Summary/ Abstract Approximately 50% of high grade serous ovarian cancers (HGSOC) are deficient in homologous recombination (HR). HR is a high-fidelity DNA double-strand break repair pathway which uses a homologous template for accurate DNA repair. The central protein of this process, RAD51, is tightly regulated. One group of proteins that work to regulate RAD51 are the RAD51 paralogs, including RAD51C and RAD51D. Collectively, RAD51C and RAD51D are mutated in 8% of HR deficient familial ovarian cancers. Although the RAD51 paralogs were discovered 20+ years ago their exact function in HR, and how mutation in these proteins contribute to HGSOC is still unknown. We have identified two possible RAD51C protein isoforms which may perform separate function in HR. RAD51C variants that would prevent protein production of either isoform have been identified in 32 separate individuals. Thus, we propose a functional analysis of these isoforms and mutations which disrupt their production. In addition, we have also identified mutations in RAD51C which disrupt its interaction with RAD51D. Our preliminary data has determined that the yeast-three-hybrid interaction between RAD51C and RAD51D is a good indicator of HR efficiency in human cells. Yet, how this RAD51C-RAD51D interaction contributes to HR is still unknown. We will examine the effects of these variants on RAD51 protein regulation and filament dynamics using single-molecule fluorescence microscopy (C-trap). By characterizing the activity of these RAD51C variants we will uncover both the function of WT-RAD51C and how dysfunctional RAD51C variants contribute to HR deficiency in HGSOC.