Genome-wide Analysis of Consensus Sites and Spectra of UV- and Cisplatin-induced Mutations in Saccharomyces cerevisiae

Abstract

Xeroderma pigmentosum (XP) is a disorder characterized by sensitivity to ultraviolet (UV) light and the development of multiple skin cancers. Defects in nucleotide excision repair (NER), a DNA damage repair system primarily responsible for excising intrastrand crosslinks, constitute the genetic basis of XP. NER is highly conserved across species; the NER gene RAD14 in the yeast Saccharomyces cerevisiae is homologous to the human NER gene XPA, which is often mutated in XP patients. Using S.cerevisiae as a model organism, we have conducted mutation accumulation experiments in wild type and rad14Δ yeast to assess the mutation spectra of yeast exposed to crosslinking agents, namely UV and the chemotherapy drug cisplatin. Whole genome sequencing revealed mutation spectra beyond the traditionally recognized UV-induced C>T transitions and cisplatin-induced G>T transversions documented in the literature. Further, novel consensus site patterns were identified in sequences from both UV- and cisplatin-treated yeast. Differences across conditions in mutation spectra and consensus sequences between wild type and rad14Δ S.cerevisiae were evident, elucidating the role of NER in repairing intrastrand crosslinks. Genome-wide analyses of sequences from UV- and cisplatin-treated yeast harboring mutations induced in vivo provide a comprehensive report on the effect of crosslinking agents on the genome, and the role nucleotide excision repair plays in detecting associated mutations.