An insert in the single gene for the large ribosomal RNA in yeast mitochondrial DNA

Abstract

MITOCHONDRIAL DNA (mtDNA) contains genes for the ribosomal RNAs (rRNAs) and transfer RNAs (tRNAs) used in mitochondrial protein synthesis and for a limited number of proteins of the mitochondrial inner membrane1–4. By a combination of genetic and physical mapping, the location of most of these genes on yeast mtDNA has been determined3,4. There is a single gene for the RNA from the large subunit of yeast mitochondrial ribosomes5, but, nevertheless, this RNA hybridises to non-adjacent fragments on the physical map of mtDNA6. Although this suggested that the gene for this RNA is split, like some eukaryotic nuclear genes7, the presence of partial gene duplications complicated the interpretation of our hybridisation experiments6. By electron microscopy of RNA–DNA hybrids we now present direct evidence for an insertion in this rRNA gene.