The Role of CLU1 in Maintaining Mitochondrial Genome Stability and Morphology in S. cerevisiae

Abstract

Mitochondrial genome maintenance is essential for the normal function of the cell. Mitochondrial DNA (mtDNA) is located in the matrix, where it is in close proximity to the electron transport chain, which is within the inner mitochondrial membrane. During oxidative phosphorylation, the electron transport chain produces reactive oxygen species (ROS) that may damage the DNA and contribute to mutations within the genome. Mutations in the mitochondrial genome have long been hypothesized as a contributor to diseases, especially those of the neuromuscular system. Mitochondrial mutations have also been linked to some types of cancer, programmed cell death, and aging in humans. The ability to repair this damage is integral for cells to maintain proper fw1ction and longevity. S. cerevisiae is a facultative anaerobe that can grow in the absence of respiration under specific growth conditions, although mitochondria are still required for viability. The lab used a yeast two-hybrid assay with the known mitochondrial protein, Ilv5p, to isolate genes involved in the organization, repair, and recombination of mtDNA. The lab has identified the Clu1p in this screen. Clu1p function was previously found to be required for proper mitochondrial morphology and distribution (1). My thesis research has focused on creating clu1? strains and performing fluctuation analysis assays using different reporters that measure specific mitochondrial events. Initial characterization of CLU1 has shown that loss of Clu1p leads to an increased loss of mitochondrial function which may occur through various events, such as point mutations, recombinations or deletions, and DNA polymerase slippage. Microscopy has supported previous reports indicating that a clu1? strain displays a "clustering" phenotype (Fields et al. 1998). This deletion strain exhibits a branched mitochondrial network that is localized to one side within the yeast cell. These data provide evidence that Clu1p plays a central role in mitochondrial genome stability and morphology.