Pet309 Is A Pentatricopeptide Repeat Protein That Interacts With The Cox1 Mrna And With The Ribosome In Yeast Mitochondria

Mitochondria have the machinery to translate the mRNAs produced inside the organelle, however very little is understood about how mitochondrial ribosomes locate the initiation codon. In yeast mitochondria a group of proteins known as translational activators recognize specific mRNAs and are thought to assist the ribosome to locate the start codon, however the mechanism of action of these proteins remains unknown. Pet309 is a translational activator specific for the COX1 mRNA (1). It acts on the COX1 5′ untranslated region (UTR) to induce translation. The protein is predicted to contain up to 23 pentatricopeptide repeats (PPR) in the sequence, with 12 repeats more strongly predicted on the central portion of the protein (2,3). These repeats are found in mitochondrial and chloroplast proteins and are involved in RNA metabolism. Through immunoprecipitation of Pet309 and reverse transcription PCR we found that Pet309 interacts with the COX1 mRNA, and that this interaction remained when the 12 central PPR motifs were eliminated. We also demonstrated that Pet309 interacts with the mitochondrial ribosome, and that this interaction is independent of the presence of the COX1 mRNA or the deletion of the 12 central PPR motifs. We conclude that Pet309 physically interacts with the COX1 mRNA and with the mitochondrial ribosomes to allow COX1 mRNA translation. Research support: CONACyT (179387), PAPIIT-UNAM (IN208711), Fundacion Miguel Aleman, AC.