The ribosomal RNA genes ofDrosophilamitochondrial DNA

Abstract

The nucleotide sequence of a segment of the mtDNA molecule of Drosophila yakuba which contains the A+T-rich region and the small and large rRNA genes separated by the tRNA^val gene has been determined. The 5 end of the small rRNA gene was located by Sl protection analysis. In contrast to mammalian mtDNA, a tRNA gene was not found at the 5′ end of the D. yakuba small rRNA gene. The small and large rRNA genes are 20.7% and 16.7% G+C and contain only 789 and 1326 nucleotides. The 5′ regions of the small rRNA gene (371 nucleotldes) and of the large rRNA gene (643 nucleotidea) are extremely low in G+C (14.6% and 9.5%, respectively) and convincing sequence homologies between these regions and the corresponding regions of mouse mt-rRNA genes were found only for a few short segments. Nevertheless, the entire lengths of both of the D. yakuba mt-rRNA genes can be folded into secondary structures which are remarkably similar to secondary structures proposed for the rRNAs of mouse mtDNA. The replication origin-containing, A+T-rich region (1077 nucleotides; 92.8% A+T), which lies between the tRNA^ile gene and the small rRNA gene, lacks open reading frames greater than 123 nucleotides.