Investigating the Regulation of the exonuclease EXO1 in genome stability.

Pennsylvania State Univ Hershey Med Ctr, Hershey PA

Investigators

Abstract

Project Summary This F31 application focuses on investigating the mechanisms of EXO1 regulation as a potential target for a novel chemotherapeutic. I am requesting support for further developing a project which I have previously published a manuscript. This proposal addresses a fundamental gap in knowledge within the DNA repair field and could significantly impact cancer treatment efficacies and overall patient survival. Additionally, the resources provided by this application would greatly benefit my development as a graduate student and allow me to reach my long-term goal of becoming an independent scientist at a research-intensive academic institution. This proposal would grant me the opportunity to learn new in vitro laboratory techniques while also applying techniques I have previously learned to new aspects of my project. Furthermore, I propose pharmacogenomic screens to identify novel genes that are synthetic lethal with EXO1 and increase cisplatin sensitivity. As I have not previously worked with CRISPR screening methods, this fellowship would allow me to further develop my laboratory skills. Receiving this award would provide me with a complex mix of critical skills that will be important for my development into a well-rounded scientist, and for which are highly attainable due to the support and resources provided by my mentorship team and at the Penn State College of Medicine. In this proposal, I focus on elucidating the mechanisms behind PCNA- and MRE11-mediated regulation of EXO1 as well as identifying other unknown genes that impact EXO1-mediated ssDNA gap processing and ultimately chemosensitivity. My recent work showed that EXO1 binds to nascent DNA after the formation of PRIMPOL- generated gaps and performs ssDNA gap expansion (Nusawardhana, et al, 2024). Moreover, I discovered that loss of USP1, a PCNA deubiquitinase, suppresses EXO1 recruitment to ssDNA gaps, indicating a role for ubiquitinated PCNA in regulation of EXO1. Here, I aim to expand on my previous work to further define the mechanism behind this DNA damage tolerance pathway, reduce this gap in knowledge, and gain information on how EXO1 can be targeted mechanistically for future chemotherapies. To investigate the regulation of EXO1 in genome stability, I will explore two aims: 1) determine how PCNA and MRE11 regulate EXO1 in genomic stability, and 2) identify genes that increase EXO1-mediated cisplatin sensitivity using CRISPR screens. Achieving these aims will expand my knowledge in the DNA repair field and uncover the mechanisms of EXO1 regulation. Not only will this work advance my personal goals, but it will significantly impact chemotherapeutic strategies by providing novel information about EXO1 as a potential cancer drug target.