Mitochondrial DNA oxidative damage and mutagenesis in Saccharomyces cerevisiae

Mutation of human mitochondrial DNA (mtDNA) has been linked to maternally inherited neuromuscular disorders and is implicated in more common diseases such as cancer, diabetes, and Parkinson's disease. Mutations in mtDNA also accumulate with age and are therefore believed to contribute to aging and age-related pathology. Housed within the mitochondrial matrix, mtDNA encodes several of the proteins involved in the production of ATP via the process of oxidative phosphorylation, which involves the flow of high-energy electrons through the electron transport chain (ETC). Because of its proximity to the ETC, mtDNA is highly vulnerable to oxidative damage mediated by reactive oxygen species (ROS) such as hydrogen peroxide, superoxide, and hydroxyl radicals that are constantly produced by this system. Therefore, it is important to be able to measure oxidative mtDNA damage under normal physiologic conditions and during environmental or disease-associated stress. The budding yeast, Saccharomyces cerevisiae, is a facile and informative model system in which to study such mtDNA oxidative damage because it is a unicellular eukaryotic facultative anaerobe that is conditionally dependent on mitochondrial oxidative phosphorylation for viability. Here, we describe methods for quantifying oxidative mtDNA damage and mutagenesis in S. cerevisiae, several of which could be applied to the development of similar assays in mammalian cells and tissues. These methods include measuring the number of point mutations that occur in mtDNA with the erythromycin resistance assay, quantifying the amount of oxidative DNA damage utilizing a modified Southern blot assay, and measuring mtDNA integrity with the "petite induction" assay.