RNase P RNA inCandida glabratamitochondria is transcribed with substrate tRNAs

Abstract

The biosynthesis of some mitochondrial enzymes requires contributions of both the mitochondrial and nuclear genomes. The ribonucleoprotein enzyme Ribonuclease P (RNase P) is composed of a mitochondrial encoded RNA and nuclear coded protein in many yeasts, including C. glabrata. We have determined that there are at least two sites of transcription initiation that contribute to the expression of the mitochondrial RNase P RNA. A nonanucleotide promoter sequence is located upstream of the initiator tRNA while the other site of initiation of transcription is at an undetermined upstream site. An analysis of the transcripts from the region of the RNase P gene demonstrates directly that the RNase P RNA is present in large primary transcripts and located between the precursors to the initiator tRNAf(Met) and tRNA(Pro) genes. Thus this enzyme subunit is synthesized with some of its substrate tRNAs. An activity with cleavage site specificity like a previously described endonuclease that cleaves near the 3' end of tRNAs, RNase P activity and one or more additional endonucleases or exonucleases not described previously are required to convert the primary transcript to its final functional RNAs.