Date of Award

Fall 2022

Document Type

Open Access Dissertation


Biological Sciences

First Advisor

Jason Stewart


The CST (CTC1-STN1-TEN1) complex is a heterotrimeric single-stranded DNA binding protein known to stimulate polymerase α-primase (Pol α) and promote telomere length regulation, genome-wide DNA replication and double strand break repair. However, much of its cellular function remains unknown. The focus of my dissertation work was to uncover novel roles of CST in DNA stress response pathways. In particular, my work relates to understanding the function of CST in sister chromatid cohesion (SCC) and base excision repair (BER) as well as characterizing CST protein interactions. SCC is established following DNA replication by loading of the cohesion complex, which encircles replicated chromatids to keep them joined until mitosis. Previous work suggested that, when replication forks stall, cohesin must be removed and re-established to prevent SCC loss. However, how this occurs is not well understood. Our findings indicate that CST interacts with the cohesion complex and helps to maintain/remodel cohesin at stalled replication forks. In addition to its role in DNA replication, CST stimulates DNA repair, particularly double strand break repair. Whether CST also participates in other repair pathways was unknown. Intriguingly, we found that CST interacts with and stimulates multiple proteins in the BER pathway, including DNA polymerase β, APE1, FEN1 and DNA ligase I. Furthermore, we demonstrated that loss of CST leads to increased oxidative damage. This work is the first to identify CST as a novel player in BER and oxidative DNA repair. Finally, we validated previously shown CST interactions in situ using the proximity ligation assay (PLA), confirming that CST interacts with Pol α, the replication helicase MCM2-7, and the telomere protection protein POT1. Combined, these findings reveal the ability of CST to serve as a multifunctional protein designed to preserve genomic integrity


© 2022, Percy Logan Schuck

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