Characterization of FMP35: A novel gene and its role in mitochondrial DNA stability

Abstract

Mitochondria are essential organelles for all eukaryotic organisms with very few exceptions. The life-giving processes contributed by mitochondria are the end result of many proteins that are encoded within the mitochondria. Many nuclear encoded proteins give mitochondrial DNA (mtDNA) the high stability needed so that life can thrive. Saccharomyces cerevisiae (baker's yeast) has historically been a model organism for mitochondrial function studies. These yeast are categorized as facultative anarobes; meaning that they are able to respire or ferment depending on media available. Functional mitochondria allow baker's yeast to thrive on a 3-carbon medium (p+), while mitochondrial dysfunctions due to mtDNA defects do not allow growth on the same medium (p-). The ease of visualizing this phenotype and culturing these organisms has made S. cerevisiae an important tool for mitochondrial studies. Nuclear encoded proteins such as Abf2p and Ilv5p have been implicated in offering a degree of stability to mtDNA. Many nuclear proteins have been localized to mtDNA, creating an essential DNA-protein complex called a nucleoid. One protein that has been defined as a mitochondrial protein is Fmp35p. This is a novel protein that remains uncharacterized. A fmp35?::URA3 gene knockout yields a p- phenotype as illustrated by a respiration loss assay. Furthermore, a significant decrease in direct repeat recombination has been described by this study. A less significant increase in polymerase slippage within microsatellites has also been documented. It is the conclusion of this study that Fmp35p plays a role in a recombination pathway that gives rise to wild type yeast with a full complement of functional mtDNA. When this gene is defective and the protein is not produced yeast will not thrive.