Mechanisms and Control of Protein Synthesis in Yeast Mitochondria

Abstract

In the yeast Saccharomyces cerevisiae, eight proteins are encoded by the mitochondrial genome. Seven of them are core catalytic subunits of complexes III and IV of the respiratory chain and the ATP synthase and thus essential for oxidative phosphorylation (OXPHOS), while one protein is soluble and a constituent of the small subunit of mitochondrial ribosomes. The expression of these proteins is mainly controlled posttranscriptionally by so-called translational activators. These nuclear-encoded factors act on the 5′-untranslated region (UTR) of their specific client mRNA and stimulate translation. In addition, translational activators play multiple roles in regulation and organization of mitochondrial protein synthesis. The mitochondrial OXPHOS complexes are assembled from subunits encoded by both the nuclear and the mitochondrial DNA. During the biogenesis of OXPHOS complexes, translational activators help to coordinate cytosolic and mitochondrial translation by adjusting mitochondrial protein synthesis to levels that can successfully be assembled. This chapter summarizes the current knowledge about how mitochondrial protein synthesis in the model organism Saccharomyces cerevisiae is coordinated with OXPHOS complex assembly.