The Role of Ilv5p Interacting Factors in Mitochondrial DNA Stability

Abstract

The ease of manipulating yeast allows for advanced studies on the factors affecting the mitochondrial DNA mutation rates. The control mechanisms of the mitochondrial DNA mutation rate has been determined to involve the dual function protein, Ilv5p. The Ilv5p plays an integral role in the proper segregation of newly replicated mitochondrial DNA into daughter cells during cell division. The focus of this study is to find unknown factors involved in mitochondrial DNA stability. This study uses the Ilv5p to pull unknown factors out of the many genes that comprise the yeast genome. The identification of interacting factors of the Ilv5p is the focus of this study. We have found proteins likely to physically interact with the Ilv5p and play a role in the stabilization of mtDNA. These proteins have been identified as the Vma8p and the YOL057W gene product. These proteins have been tested and shown to affect the stability of mitochondrial DNA. The Vma8p is the D subunit that comprises the V 1 complex. The V-ATPase that is responsible for ATP synthesis possesses two complexes, the V_1 and the V_0 complex. The V_1 and the V_0 complexes readily dissociate and reassociate in response to environmental conditions optimizing acidification of vacuole components for regulation of ATPase activity in other cellular components. The loss of this particular protein increases the occurrence of ?-petite or non-functional mitochondria. A microsatellite instability assay showed that the mutation rate increased 50 times with the loss of the Vma8p. The respiration loss assay showed the loss of the YOL057W gene product caused a significant increase in the rate of ?- petite formations. This assay is the first to show that the putative open reading frame (ORF) encodes a protein whose loss of function leads to a mitochondrial defect. The exact role of this particular protein in the mitochondria has yet to be determined.