In our everyday lives, we are constantly being exposed to DNA damaging agents, both from internal and external sources. The most deleterious type of DNA damage a cell can suffer is the DNA double-stranded break (DSB). Breast Cancer 1 (BRCA1) is a protein necessary for the proper repair of resultant DNA DSBs through the homologous recombination (HR) pathway. Defects in BRCA1 have been linked to different types of cancer in both men and women, including breast, ovarian, and pancreatic cancer. However, the regulation of BRCA1 is not yet well understood, and in many cases, how defects in this pathway lead to an increased risk of developing cancer is also unknown, making preventative care and treatment of resulting cancers more difficult. Our lab has discovered that SIRT2, a histone deacetylase and putative human tumor suppressor, plays a crucial role in the DNA damage response (DDR) and repair of DNA DSBs. We have shown that depletion of SIRT2 impairs HR and increases cell sensitivity to IR in a deacetylase-dependent manner. A mass spectrometry analysis showed SIRT2 interacts with a number of proteins involved in DDR, including BRCA1. We validated the interaction between SIRT2 and BRCA1 and also found SIRT2 deacetylates BRCA1 both in vitro and in cells. Depletion of SIRT2 and subsequent deacetylation of BRCA1 decreases BRCA1 protein levels in cells and thus impairs HR. Our results show SIRT2 is a novel regulator of BRCA1 and is critical for the repair of DNA DSBs through HR. These findings provide insight into how dysregulation of SIRT2 or BRCA1 can result in genomic instability and lead to the development of cancer.

Citation Format: Elizabeth Minten, Hui Zhang, Chunyang Li, PamelaSara Head, David Yu. Regulation of BRCA1 by SIRT2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1363.