Date of Award
12-2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Biochemistry and Molecular Biology
Committee Chair/Advisor
Jennifer Mason
Committee Member
Michael Sehorn
Committee Member
James Morris
Committee Member
Lela Lackey
Abstract
Every day our cells are bombarded with DNA lesions that threaten the stability of our genome. To help maintain genomic integrity our cells evolved to have a network of enzymes dedicated to repairing DNA lesions. Upon encountering a site of DNA damage, a cell recruits enzymes that remodel the stalled replication fork by reannealing the newly synthesized DNA together known as fork regression. Loss of fork regression activity has been shown to promote replication stress resistance after induced DNA damage. In this thesis, I discuss the role F-Box Helicase 1 (FBH1) plays in fork regression and how FBH1 promotes the replication stress response. I discovered that FBH1 inhibits DNA damage tolerant polymerase PRIMPOL from facilitating unrestrained replication. I show that the role of PRIMPOL inhibition by FBH1 is different than other fork regression enzymes as it is not required to promote the replication stress response. I propose inhibiting checkpoint kinase WEE1 as a target for cancer cells with reduced FBH1 expression. I then identify possible targets by small molecule inhibitors that can be used to kill FBH1 deficient cancer cells. One of the most severe forms of DNA damage is the formation of double strand breaks (DSB). A single DSB left unrepaired can result in cell death. One of the primary mechanisms to repair DSBs is through template dependent homologous recombination (HR). HR requires filament formation of RAD51 to perform a homology search on template DNA. Regulation of HR RAD51 is common and often defective in human cancers. In this thesis I determine that overexpression of the kinase NEK8 negatively regulates HR by inhibiting RAD51 focus formation. I then propose that NEK8 overexpression, which is found in a high percentage of invasive breast cancer, can be treated by PARP inhibition. In conclusion, this work establishes a role that FBH1 plays in inhibiting alternative replication during hydroxyurea induced DNA damage. It also proposes potential chemotherapeutic targets to treat FBH1 deficient cancers. I also show that overexpression of NEK8 in cells results in decreased RAD51 focus formation leading to deficient HR and increased replication fork degradation. Overall, this work increases the understanding of how cells maintain genomic integrity and possible targets for cancers mis-regulating FBH1 or NEK8
Recommended Citation
Turner, Joshua, "Characterizing Mechanisms of DNA Repair and Genome Stability" (2024). All Dissertations. 3824.
https://open.clemson.edu/all_dissertations/3824