DETECTION, LOCALIZATION, AND SEQUENCE ANALYSES OF MITOCHONDRIAL REGULATORY REGION RNAS IN SEVERAL MAMMALIAN-SPECIES

The mitochondrial regulatory region (mrr) located between the tRNA(Phe ) and tRNA(Pro) genes of mitochondrial DNA (mtDNA) is essential for re gulation of replication and transcription of the mitochondrial genome, Polyadenylated short RNAs complementary to the L-strand of the mrr in human cells and similar RNAs (polyadenylation status unknown) in rat and mouse cells have been reported, We now report detection of ca, 0.2 kb polyadenylated mrrRNAs in cultured cells of Chinese hamster, Afric an green monkey, mouse, rat, and human, We isolated a cDNA clone to a rat polyadenylated mrrRNA of 158 bp in length excluding the polyadenyl tail, which spans the region from the light strand promoter (LSP) to the origin of heavy strand replication (OriH), This cDNA contains both an open reading frame encoding a 26 amino acid polypeptide and a 12 n ucleotide sequence complementary to the 3'-terminus of rat mitochondri al 12S rRNA, A cDNA clone to a human HeLa cell polyadenylated mrrRNA a lso contains a 12 nucleotide region complementary to the human mitocho ndrial 12S rRNA, We used a mitochondrial genome-deficient HeLa cell li ne, rho(0) HeLa, and a derived cybrid cell line, HeEB, with a reconsti tuted mitochondrial genome, to demonstrate that the occurrence of the mrrRNA is dependent on the presence of a mitochondrial genome, and the se polyadenylated mrrRNAs are transcribed from the mitochondrial genom e, Our results further substantiate the common existence of polyadenyl ated mrrRNAs among mammals and support previously proposed hypotheses for the multi-functional nature of polyadenylated mrrRNA.