Investigating the Role of Translesion Synthesis in the Prevention of CAG Repeat Fragility in S. cerevisiae.
- Expansion of trinucleotide repeats, such as CAG/CTG repeats, is the cause of several neurological disorders and can result from mistakes during DNA replication and repair. These expanded CAG repeats create sites of chromosome fragility that are prone to breakage and require repair. There are several mechanisms linked to maintaining repeat fidelity, but a role for the DNA damage tolerance pathway ... read morecalled translesion synthesis (TLS) in suppressing repeat fragility had not yet been investigated. In S. cerevisiae, more commonly budding yeast, Rad30 (pol η), Rev1, and Rev3/Rev7 (pol ζ) are the key polymerases in the TLS pathway, forming the cellular machinery that allows replication to bypass lesions in DNA. Work from our lab has shown that deletion of only one or two of the TLS polymerases had CAG fragility levels similar to those of wild-type strains, suggesting that perhaps the polymerases can compensate for one another when one or more is missing. This project proposed a systematic deletion of all TLS polymerases in order to assess the role of TLS in preventing repeat fragility.Additionally, a fourth polymerase of interest, Trf4 had been previously shown to also protect against CAG repeat fragility. However, Trf4’s actual function is ambiguous because it has two potential roles in the cell: one as a TLS polymerase and another in RNA processing. This project examined both potential roles to determine which function is more important at CAG repeats, which will either further implicate Trf4 as a TLS polymerase or disprove its function in the TLS pathway entirely.read less