Multiple DNA repair pathways prevent acetaldehyde-induced mutagenesis in yeast

Abstract

Acetaldehyde is the primary metabolite of alcohol and is present in many environmental sources including tobacco smoke. Acetaldehyde is genotoxic, whereby it can form DNA adducts and lead to mutagenesis. Individuals with defects in acetaldehyde clearance pathways have increased susceptibility to alcohol-associated cancers. Moreover, a mutation signature specific to acetaldehyde exposure is widespread in alcohol and smoking-associated cancers. However, the pathways that repair acetaldehyde-induced DNA damage and thus prevent mutagenesis are vaguely understood. Here, we used Saccharomyces cerevisiae to delete genes in each of the major DNA repair pathways to identify those that alter acetaldehyde-induced mutagenesis. We observed that loss of functional nucleotide excision repair (NER) had the largest effect on acetaldehyde mutagenesis. In addition, base excision repair (BER), as well as DNA protein crosslink (DPC) repair pathways were involved in modulating acetaldehyde mutagenesis, while mismatch repair (MMR), homologous recombination (HR) and post replication repair are dispensable for acetaldehyde mutagenesis. Acetaldehyde-induced mutations in an NER-deficient (Δrad1) background were dependent on translesion synthesis as well as DNA inter-strand crosslink (ICL) repair. Moreover, whole genome sequencing of the mutated isolates demonstrated an increase in C→A changes coupled with an enrichment of gCn→A changes which is diagnostic of acetaldehyde exposure in yeast and in human cancers. Finally, downregulation of the leading strand replicative polymerase Pol epsilon, but not the lagging strand polymerase, resulted in increased acetaldehyde mutagenesis, indicating that lesions are likely formed on the leading strand. Our findings demonstrate that multiple DNA repair pathways coordinate to prevent acetaldehyde-induced mutagenesis.

Keywords: Acetaldehyde; DNA protein crosslink repair; Mutagenesis; nucleotide excision repair.