Differential expression of sense and antisense transcripts of the mitochondrial DNA region coding for ATPase 6 in fetal and adult porcine brain: Identification of novel unusually assembled mitochondrial RNAs

The mammalian mitochondrial genome is a double-stranded circular DNA molecu le, which is transcribed from both strands as polycistronic RNAs, which are further processed to yield the mature polyadenylated mRNAs, rRNAs and tRNA s. me compared the gene expression patterns of foetal and adult porcine bra ins and identified a sequence tag from the ATPase 6 region of the mitochond rial genome which, in adult brain, was more abundant in the sense (H-strand ) form, but, in foetal brain, more abundant in the antisense form (L-strand ). By means of solution hybridisation/S1 nuclease protection assay, Norther n blotting, and PCR based techniques, we demonstrated that the ATPase 6 reg ion of the porcine mitochondrial genome is transcribed as co-existing, stab le sense and antisense RNAs. Furthermore, we identified sense and antisense transcripts from this region consisting of inversely assembled fragments j oined together at a direct repeat of 7 nucleotides. Our results suggest tha t transcription and post-transcriptional processing of mitochondrial RNAs a re much more complex than presently thought. (C) 2000 Academic Press.