Comparative hybridization of mitochondrial and cytoplasmic aminoacyl transfer RNA with mitochondrial DNA from rat liver.

We have tested the specificity of hybridization of mitochondrial tRNA with mitochondrial DNA. Techniques are now available for performing RNA-DNA hybridization at low temperatures in the presence of 50 per cent formamide. With this technique, specific aminoacyl-tRNA-DNA hybridization can be followed in the presence of other species of RNA if the tRNA is acylated with radioactive amino acids. With this technique, mitochondrial leucyl-tRNA from rat liver has been found to anneal to mitochondrial DNA. Competitive hybridization between mitochondrial leucyl-tRNA and mitochondrial or cytoplasmic aminoacyl-tRNA shows that mitochondrial tRNA competes much more efficiently than cytoplasmic tRNA for sites of annealing to mitochondrial DNA. These results show that mitochondrial leucyl-tRNA differs from cytoplasmic leucyl-tRNA in its primary base sequence. They also imply that mitochondrial DNA may be the template from which mitochondrial tRNA is transcribed.