Transcription of rat mitochondrial NADH-dehydrogenase subunits. Presence of antisense and precursor RNA species

We have characterized the transcriptional pattern of the rat mitochondrial ND6-containing region in vivo. We have identified a stable polyadenylated RNA species complementary for the full length of the ND6 mRNA. The analysis of the ND5 region has revealed the presence of an antisense RNA only at its 3? end. The presence of these stable antisense species complementary to structural genes is intriguing and suggests a possible regulatory function. The quantitative analyses have demonstrated that the H transcripts, both codogenic and non-codogenic, are more stable than the L transcripts. We have defined the 5? end of the ND6 mRNA at the level of the ATG downstream of the tRNAGlu. The mapping of the ND1 5? end has demonstrated that GTG is the first codon of the mRNA. Our findings suggest that the post-transcriptional mechanisms involved in the expression of the mt genome are much more numerous and complex than those already described in the literature.