Deletion of the MTO2 gene related to tRNA modification causes a failure in mitochondrial RNA metabolism in the yeast Saccharomyces cerevisiae

We report here the characterization of the yeast mto2 null mutants carrying wild-type mitochondrial DNA or 15S rRNA C1049G allele. The amounts of mitochondrial tRNALys, tRNAGlu, tRNAGln, tRNALeu, tRNAGly and tRNAMet were markedly decreased but those of tRNAArg and tRNAHis were not affected in mto2 strains. The mto2 strains exhibited significant reduction in the aminoacylation of tRNALys, tRNALeu but almost no effect in those of tRNAHis. Interestingly, the strain carrying the C1049G allele exhibited an impairment of aminoacylation of those tRNAs. Furthermore, the steady-state levels of mitochondrial mRNA CYTB, COX1, COX2, COX3, and ATP6 were markedly decreased in mto2 strains. These data strongly indicate that unmodified tRNA caused by the deletion of MTO2 caused the instability of mitochondrial tRNAs and mRNAs and impairment of aminoacylation of tRNAs.