Modulation of the replication stress response by the mono-ADP-ribosyltransferase PARP14
Open Access
- Author:
- Dhoonmoon, Ashna
- Graduate Program:
- Biomedical Sciences
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 10, 2022
- Committee Members:
- David Degraff, Outside Field Member
James Broach, Major Field Member
Zhonghua Gao, Major Field Member
George Moldovan, Chair & Dissertation Advisor
Ralph Keil, Program Head/Chair
Lisa Shantz, Outside Unit Member - Keywords:
- PARP14
CRISPR screen
DNA repair
Chemoresistance
Replication fork protection
Genomic stability
Replication stress
BRCA - Abstract:
- Genomic instability is a major hallmark of cancer and one of the most common causes is DNA replication stress. Mutations in genes involved in the DNA replication stress response are closely linked to cancer predisposition and progression but this has been exploited clinically. In the advent of personalized medicine, it has become clear that a better understanding of underlying mechanisms is important to advance cancer therapy, especially to address chemoresistance. In this dissertation, I present work demonstrating novel roles for PARP14, a lesser studied member of the PARP family, in regulation of the replication stress response, and subsequently genomic stability and chemo-response. I will first present a genome-wide CRISPR-Cas9 screen designed to identify synthetic lethal interactors of PARP14. PARP1 inhibitors which are synthetically lethal with BRCA-mutant tumors have demonstrated that synthetic lethal therapy is a powerful tool for cancer therapy. I will show that this unbiased approach allowed us to gain insights into the synthetic lethality mechanism between PARP14 and the ATR-CHK1 pathway via modulation of replication fork dynamics. Next, I demonstrate that PARP14 plays a central role in stabilization of stalled replication forks which arise due to high replication stress level in BRCA1/2 deficient cells. Mechanistically I show that PARP14 mediates stalled replication fork degradation via its interaction with the nuclease MRE11. Moreover, I also identify KU as an essential component of a multi-step mechanism by which the KU-PARP14 axis differentially promotes degradation by the nucleases MRE11 and EXO1. This mechanism restores genomic stability in BRCA-deficient cells and subsequently promotes chemoresistance. Overall, my work provides insights into novel mechanisms by which PARP14 affects the replication stress response and show that PARP14 can be used as a biomarker for chemo-response.