Date of Award

Spring 2022

Degree Type



Biological Sciences

Director of Thesis

Jason Stewart

Second Reader

Perry Logan Schuck


CST (CTC1-STN1-TEN1) is a heterotrimeric RPA-like protein complex that preferentially binds to single-stranded DNA (ssDNA). CST is conserved from yeast to humans and has been found to play a role in telomere maintenance, DNA replication, and DNA repair. Mutations in CST, specifically in the subunits of CTC1 and STN1, have been implicated in the development of the genetic diseases Coats plus and dyskeratosis congenita. Despite the known functions of CST, the mechanistic relationship between its structure and function has yet to be characterized, particularly with respect to its protein-protein interactions and DNA binding. An X-ray crystallography structure of CST revealed the structure of two-winged helix (wH) domains in its STN1 subunit. Based on the previous analysis of the wH domain in RPA, a homologous protein to CST, we hypothesized that deletion of the STN1 wH domains disrupts its interaction with known binding partners. To test this, we generated STN1 mutants lacking the wH domains and investigated CST protein-protein interactions with MCM2-7, DNA polymerase alpha-primase, and TPP1. It was found that the wH domains are necessary for interaction with TPP1 and DNA polymerase alpha-primase, but not for interaction with MCM2-7. The analysis of how CST’s structure is responsible for its mechanistic action has important implications for characterizing and developing potential treatments for diseases correlated with CST mutations.

First Page


Last Page


Available for download on Sunday, April 28, 2024