Regulation of replication fork stability by ssDNA binding proteins

Abstract

The replication stress response (RSR) maintains genome stability and promotes the accurate duplication of the genome. ssDNA binding proteins are integral components of the RSR and have been extensively studied for years. However, the mechanisms by which they specifically direct enzymes to the right substrates and how they regulate replication fork remodeling is less well understood. My thesis projects have focused on the regulation of fork remodeling pathways by ssDNA binding proteins. In Chapter III, I discovered how RPA enforces SMARCAL1 substrate specificity to promote appropriate fork reversal. In chapter IV, I identified a new RPA-like ssDNA binding protein, RADX, at replication forks. I characterized the function of RADX as a negative regulator of RAD51 mediated fork reversal and described RADX loss as a chemo-resistance mechanism in BRCA2-deficient U2OS cells. In chapter V, I further explored the mechanisms by which RADX regulates RAD51. Utilizing RADX as a tool, I interrogated RAD51 functions in different pathways of fork protection and discovered the differential requirements of RAD51 in fork reversal and fork protection. Overall, my thesis has made significant contributions to our understanding of the processes of fork reversal and fork protection and has identified a potential chemo-resistance mechanism for BRCA2-mutant cancers.