June 19th: Chris Sausen (Bochman) "Regulation of Pif1 Family Helicases During DNA Replication and Repair" 10:00am
Defense will be held virtually. Zoom link to be posted soon.
DNA helicases can unwind DNA and are required for many of the transactions that occur during DNA replication, recombination, and repair. The PIF1 family DNA helicases are conserved from bacteria to humans and prevent or resolve DNA damage in the nucleus and mitochondria through a multitude of functions, acting as tumor suppressors. Mutation and misregulation of the human PIF1 (hPIF1) helicase are linked to cancer, but we lack an in-depth understanding of the functions and regulation of PIF1 enzymes in genome maintenance and thus why aberrant hPIF1 function is disease linked. A PIF1 helicase in Saccharomyces cerevisiae (ScPif1) is the founding member of the PIF1 family and is the most well understood PIF1 enzyme, acting as a model for hPIF1 function. It is a multi-domain protein, which is characteristic of the PIF1 family, yet the functions of the non-helicase domains were previously unknown. Furthermore, other mechanisms of PIF1 helicase regulation such as post-translational modification (PTM) had yet to be clearly elucidated. My thesis has focused on answering these questions, determining how ScPif1 is regulated via its N-terminal domain and PTM, namely lysine acetylation. Our work demonstrates that the ScPif1 N-terminus (PiNt) is a regulatory domain, important for its enzymatic activities and function in vivo. The PiNt is also critical for ScPif1 lysine acetylation, which stimulates ScPif1 DNA binding, increasing its ability to facilitate Okazaki fragment processing. Our work has also extended to a bacterial PIF1 (TePif1) and the hPIF1 helicase, demonstrating how these mechanisms of regulation are conserved among PIF1 family helicases. Our findings demonstrate that PIF1 family helicases are regulated via non-helicase domains and acetylation, furthering our understanding of how these enzymes function in the maintenance of genome integrity.