A nonanucleotide sequence involved in promotion of ribosomal RNA synthesis and RNA priming of DNA replication on yeast mitochondria

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Abstract
We have examined the initiation of transcription of the mitochondrial genes for ribosomal RNA (rRNA) in the yeast Kluyveromyces lactis and show that these are transcribed independently from individual promoters. The mature large rRNA contains a 5‘ di-or triphosphate end which can be labeled in vitro with [α32p]GTP using guanylyltransferase and this enabled us to determine the nucleotide sequence of its 5‘ terminus. For the small rRNA, a minor in vitro capped RNA species hybridizes in the region where – as judged from S1 nuclease protection experiments – the precursor of this RNA starts. We have determined the DNA sequence around the beginning of both rRNA genes and this reveals the existence of an indentical nonanucleotide sequence (5‘ –ATATAAGTS– 3’) just preceding the positions where the rRNAs start. This sequence is identical to the one preceding the rRNA genes in the mtDNA of the distantly related yeast Saccharomyces cerevisiae (Osinga, K.A. and Tabak, H.F.(1982) Nucl. Acids Res. 10,3617-3626) and supports out proposal that this sequence motif is part of a yeast mitochondrial promoter.