Abstract A10: The impact of cancer-associated RAD51C mutations in homologous recombination

Abstract

Abstract Homologous recombination (HR) is a major pathway for the repair of DNA double-strand breaks (DSBs). Loss of function of key HR repair proteins have been linked to diseases characterized by genomic instability including cancers and Fanconi anemia. Regulation of RAD51 filaments is critical during HR repair and is mediated by several factors including the RAD51 paralogs, a group of proteins that share sequence homology with RAD51. The RAD51 paralog family consists of five proteins in humans, RAD51B, RAD51C, RAD51D, XRCC2, and XRCC3. The RAD51 paralog, RAD51C, has recently become a key protein of interest as RAD51C mutations have been linked to familial breast and ovarian cancers. However, the specific functions of RAD51C have remained enigmatic as mouse and non-tumorigenic knockout models are inviable. Given these limitations, we have identified RAD51C point mutations from breast and ovarian cancer patients to study the phenotypes of these RAD51C mutants and how they impair homologous recombination. We have found that RAD51C mutations can disrupt interactions with RAD51 paralog binding partners, RAD51B and XRCC3, required for RAD51C stability. Through yeast-two/three-hybrid and co-immunoprecipitation experiments, we isolated RAD51C mutations that disrupt interactions within RAD51 paralog complexes. These complexes have important roles in the repair of classical DSBs induced by ionizing radiation or chemotherapeutic reagents as well as in replication fork protection such as after replication stress induced by hydroxyurea. Using RAD51C mutants to complement a conditional knockout model, we investigated how the roles of RAD51C were impacted by point mutations in response to these diverse substrates to ultimately understand how tumors with RAD51C mutations can be best targeted for treatment. Citation Format: Meghan R. Sullivan, Rohit Prakash, Maria Jasin, Kara A. Bernstein. The impact of cancer-associated RAD51C mutations in homologous recombination [abstract]. In: Proceedings of the AACR Special Conference on DNA Repair: Tumor Development and Therapeutic Response; 2016 Nov 2-5; Montreal, QC, Canada. Philadelphia (PA): AACR; Mol Cancer Res 2017;15(4_Suppl):Abstract nr A10.