Investigating the Role of DNA Helicases and Repair Mechanisms in G-Quadruplex Processing in Saccharomyces cerevisiae

Abstract

The preservation of genomic stability and integrity is essential for life. DNA is susceptible to damage which may arise from a variety of different agents, both exogenous and endogenous. R-loops, a structure that forms during transcription consisting of a DNA-RNA hybrid and a single-stranded DNA, and G-quadruplexes, G-rich nucleic acid sequences that can form four-stranded structures via non-canonical associations of guanines, are two endogenous structures that can cause DNA damage. It is thought that Pif1 helicase unwinds and resolves G4 structures. However, in the absence of Pif1, there may be other factors involved in G4 processing. One mechanism for repairing damage is nucleotide excision repair (NER). In a previous study, it was shown that R-loops are sensitive to NER. Because of structural similarities between R-loops and G4 structures, we propose that NER may also be involved in processing G4 structures. In this study, we use the direct repeat recombination assay to show that a single naturally-occurring G4 motif can cause damage in the absence of Pif1 in vivo. With this positive control established, we are currently in the process of constructing strains deficient in NER protein Rad14 to determine whether NER mechanisms are involved in G4 processing. This study aims to expand our understanding of G4-related damage and repair mechanisms.