2020 Theses Doctoral

The role of SMARCAD1 during replication stress

Joseph, Sarah

Heterozygous mutations in BRCA1 or BRCA2 predispose carriers to an increased risk for breast or ovarian cancer. Both BRCA1 and BRCA2 (BRCA1/2) play an integral role in promoting genomic stability through their respective actions during homologous recombination (HR) mediated repair and stalled replication fork protection from nucleolytic degradation. SMARCAD1 (SD1) is a SWI/SNF chromatin remodeler that has been implicated in promoting long-range end resection and contributes to HR. Using human cell lines, we show that SMARCAD1 promotes nucleolytic degradation in BRCA1/2-deficient cells dependent on its chromatin remodeling activity. Moreover, SMARCAD1 prevents DNA break formation and promotes fork restart at stalled replication forks. These studies identify a new role for SMARCAD1 at the replication fork. In addition to the work presented here, I discuss a method for introducing stop codons (nonsense mutations) into genes using CRISPR-mediated base editing, called iSTOP, and provide an online resource for accessing the sequence of iSTOP sgRNASs (sgSTOPs) for five base editor variants (VQR-BE3, EQR-BE3, VRER-BE3, SaBE3, and SaKKH-BE3) in humans and over 3 million targetable gene coordinates for eight eukaryotic species. Ultimately, with improvements to CRISPR base editors this method can help model and study nonsense mutations in human disease.