Characterization of the yeast mitochondrial locus necessary for tRNA biosynthesis: DNA sequence analysis and identification of a new transcript.

Most components necessary for the biosynthesis of mitochondrial tRNAs are coded by nuclear genes, but one mitochondrial locus other than the tRNA genes themselves is required to make functional tRNAs in the yeast Saccharomyces cerevisiae. DNA sequence analysis of this yeast mitochondrial tRNA synthesis locus is reported here. This region of mitochondrial DNA is almost exclusively A+T-rich DNA with one G+C-rich element. Despite the unusual structure of the DNA in this region, we have demonstrated that it codes for a heretofore unidentified mitochondrial transcript about 450 bases in length. Since this RNA is the only RNA encoded by the tRNA synthesis locus, it must be the active agent of the locus. This RNA could either act autonomously through RNA-RNA interactions or as part of an RNA-protein complex to effect tRNA biosynthesis.