Aep3p Stabilizes the Mitochondrial Bicistronic mRNA Encoding Subunits 6 and 8 of the H⁺-translocating ATP Synthase of Saccharomyces cerevisiae

Subunits 6 and 8 of the mitochondrial ATPase in Saccharomyces cerevisiae are encoded by the mitochondrial genome and translated from bicistronic mRNAs containing both reading frames. The stability of the two major species of ATP8/ 6 mRNA, which differ in the length of the 5′-untranslated region, depends on the expression of several nuclear-encoded factors. In the present study, the product of the gene designated AEP3 (open reading frame YPL005W) is shown to be required for stabilization and/or processing of both ATP8/6 mRNA species. In an aep3-disruptant strain, the shorter ATP8/6 mRNA was undetectable, and the level of the longer mRNA was reduced to ∼35% that of wild type. Localization of a hemagglutinin-tagged version of Aep3p showed that the protein is an extrinsic constituent of the mitochondrial inner membrane facing the matrix.