The tRNAAGYSer and tRNACGYArg genes from a gene cluster in yeast mitochondrial DNA.

Yeast mitochondrial DNA-pBR322 recombinant DNA molecules screened for rRNA genes were used as a source of DNA for mitochondrial tRNA gene sequence analysis. We report here the sequences of yeast mitochondrial tRNA genes coding for a tRNAAGYSer and a tRNACGYArg. The tRNAAGYSer sequence deduced from the gene is the first reported sequence of a yeast tRNAAGYSer. It is also the second yeast mitochondrial tRNASer gene to be sequenced, and demonstrates unequivocally the presence of mitochondrial encoded serine tRNA isoacceptors. The tRNACGYArg sequence deduced from the gene is the most AT-rich (82%) tRNA sequence ever reported. Whereas all the mitochondrial genes sequenced to date exist singly on the genome and are separated by long stretches of AT-rich DNA, the tRNAACYSer and tRNAcgyarg genes exist in tandem, separated by only 3 bp. This gene arrangement strongly suggests that mitochondrial tRNA genes may be transcribed into multicistronic precursors.