The RNA component of mitochondrial ribonuclease P from Aspergillus nidulans.

Several RNA molecules that copurified with Aspergillus nidulans mitochondrial ribonuclease (RNase) P were identified [Lee, Y C., Lee, B. J., Hwang, D. S. & Kang, H. S. (1996) Eur J. Biochem. 235, 289-296], and their partial sequences were determined. Using an oligonucleotide probe, we cloned and mapped the gene encoding this putative RNA component of RNase P (RNase P-RNA), situated between URFA3 (unidentified reading frame A3) and cobA (apocytochrome b) genes in the mitochondrial genome of A. nidulans. The gene is extremely (A+T)-rich and contains two regions of sequence similarity conserved among the known mitochondrial RNase P-RNAs and the eubacterial RNase P-RNAs. The determination of 5' and 3' termini by primer extension and sequencing indicated that the length of the RNA transcript is 232 nucleotides. Northern-blot analysis revealed that its only subcellular location was the mitochondria. Two RNase P-RNA fragments of 110 nucleotides and 80 nucleotides, each containing one of the two conserved regions, could be recovered from the nuclease-treated enzyme without significant loss of activity. The sizes of these fragments appeared to be the minimum lengths required for the vitro activity of the enzyme.