Organization and expression of a tRNA gene cluster in Saccharomyces cerevisiae mitochondrial DNA

Abstract

We have studied the organization and expression of a group of tRNA genes located on a 2,700 base pair portion of the yeast mitochondrial genome between the genetic markers cap (chloramphenicol resistance) and oxil (cytochrome oxidase subunit II). This region is spanned by mitochondrial DNA inserts of two recombinant plasmids, pYm162 and pYm267, which have been extensively mapped and sequenced. This tRNA group is composed of six tRNA genes, coding for tRNA AAR (Lys) , tRNA AGR (Arg) , tRNA GGN (Gly) , tRNA GAY (Asp) , tRNA AGY (Ser) , and tRNA CGN (Arg) . We report the sequence for the majority of the 2,700 base pair region including the genes for all six tRNAs. All six genes are oriented in the same direction and are, therefore, transcribed from the same DNA strand. Further, a comparison of the organization of this region with the analogous region of a related wild type strain shows that the tRNA gene order in the two strains is the same. Five of the six tRNA genes have corresponding transcripts in wild type RNA. Although a potential structural gene for tRNA CGN (Arg) is present, we do not detect a tRNA CGN (Arg) gene transcript.