Aep3p-dependent translation of yeast mitochondrial .

Translation of mitochondrial gene products in depends on mRNA-specific activators that bind to the 5' untranslated regions and promote translation on mitochondrial ribosomes. Here we find that Aep3p, previously shown to stabilize the bicistronic mRNA and facilitate initiation of translation from unformylated methionine, also activates specifically translation of This is supported by several lines of evidence. Temperature-sensitive mutants are selectively blocked in incorporating [S]methionine into Atp8p at nonpermissive but not at the permissive temperature. This phenotype is not a consequence of defective transcription or processing of the pre-mRNA. Neither is it explained by turnover of Aep3p, as evidenced by the failure of mutants to express a recoded when this normally nuclear gene is substituted for in mitochondrial DNA. Finally, translational of mRNA in mutants is partially rescued by recoded allotopic () in a high-expression plasmid or in a CEN plasmid in the presence of recessive mutations in genes involved in stability and polyadenylation of RNA.