Discipline: Biological Sciences
Subcategory: Cancer Research
Ji'Vone Freeman - Philander Smith College
Co-Author(s): Katie Brady and Jason Stewart, University of South Carolina, Columbia, SC
In humans, DNA replication is a process that must be carefully maintained throughout each cell cycle in order to prevent errors. These errors, which can arise from both environmental and endogenous factors, can result in mutation of the DNA and ultimately cause cancer. One way that errors can arise is by the stalling of DNA replication. Studies have shown that, if not corrected, stalled replication forks can lead to problems such as double stranded breaks and chromosome fusions. Stalled replication forks can be rescued through restart of the stalled replication fork or the firing of dormant origins. Dormant origins are licensed origins that do not typically fire during normal DNA replication. The newly discovered CST protein complex is a single stranded binding protein composed of subunits CTC1, STN1, and TEN1. Mutations in CST can lead to cancer and several genetic disorders. CST has been shown to associate with and help maintain the DNA at the end of chromosomes, known as the telomere. Due to its function during telomere replication and the finding that only 20% of CST localizes to the telomeres, it was hypothesized that CST has non-telomeric functions. Previously, CST was shown to promote replication rescue through dormant origin firing following replication stress. Based on these findings, we hypothesized that CST may play a role in dormant origin activation. To investigate the role of CST in replication initiation, western blotting and immunofluorescence were performed to determine whether knockdown or overexpression of CST affects origin activation. We found that altered CST expression affects the levels of chromatin-bound MCM and Cdc45. Cdc45 and MCM help form the core helicase machinery for origin activation. This data suggests that CST may be involved in origin initiation, likely in response to stalled replication forks. Overall, these findings suggest that CST levels must be regulated carefully within cells in order to prevent malfunctions in origin activation that may lead to double strand breaks and genomic instability.
Funder Acknowledgement(s): USC Center for Colon Cancer Research: Summer Undergraduate Minority Research Program; USC Office of Research: Support for Minority Advancement in Research Training.
Faculty Advisor: Cynthia Burroughs,