Abstract 1310 Investigating a role of atypical ubiquitin chains in regulating the DNA damage response

Ubquitination is a post-translational modification that helps regulate protein degradation, the DNA damage response, and signal transduction. Ubiquitin covalently binds to lysine residues on target proteins through a cascade mechanism. Ubiquitin itself has seven lysine residues, enabling the formation of different types of ubiquitin chains that serve different functions. The purpose of this study was to investigate the involvement of atypical ubiquitin chains in regulating the DNA damage response in yeast Saccharomyces cerevisiae. We examined the effects of blocking the formation of atypical poly-ubiquitin chains on the DNA damage response. Ubiquitin poly-Ub chain sites were mutated from Lysine to Arginine, thus shunting chain formation. Growth assays were conducted to study the survival of KR mutants under DNA damage conditions. Western blots were conducted to compare checkpoint activation (Rad53 and H2AX phosphorylation) in WT and KR mutant cells under DNA damage conditions. Results showed that mutating K11 and K63 to arginine residues reduces cell survival under DNA damage conditions. DNA damage induced H2AX phosphorylation is also lower in these mutants. Our findings support the importance of atypical K11 and K63 ubiquitin chains in checkpoint activation and cell survival under DNA damage conditions. This project was funded by the Knoedler Research Fund.