In vitro transcription analysis of the region of Saccharomyces cerevisiae mitochondrial DNA containing the tRNA(fMet) gene.

Prior work has indicated that an octanucleotide [5'TATAAGTA(+1)3'] sequence is used as a promoter in yeast mitochondria. Two such sequences (FP1 and FP2) are present upstream of the tRNA(fMet)-RNAse P RNA -tRNA(Pro) gene cluster but only the FP1 promoter but not the FP2 appears to be active in vivo and in vitro. The results presented in this paper suggest that the downstream ATTAATT sequence close to the initiation site of FP2 causes premature termination of transcription and effectively inhibits transcription from the FP2 octanucleotide sequence. Thus the different levels of RNA synthesis from these tRNA(fMet) promoters might be determined by variable transcriptional initiation and elongation blockage events. Since FP1 is found to be the only active promoter in this gene cluster, these three genes are thought to be transcribed together from the FP1 promoter. In this study, a new promoter (SP) between the tRNA(fMet) and RNase P RNA genes has been identified which may participate in RNase P RNA gene expression. The sequence of the new promoter does not match perfectly to the mitochondrial conserved promoter sequence but does match to the consensus promoter sequence.