Biogenesis of mitochondria: Mapping of transcripts from the oli2 region of mitochondrial DNA in two grande strains of Saccharomyces cerevisiae.

A series of 14 contiguous restriction fragments of yeast mitochondrial DNA that cover a 5.2 kb segment including the oli2 gene provided a set of hybridization probes that were used to analyze gel fractionated mitochondrial RNA immobilized on diazotized paper. Of the nine oli2 region transcripts in grande strain J69-1B (class I), the five largest (5,100, 4,500 (most prominent), 3,900, 3,600 and 3,000 nucleotides) contain the oli2 coding sequence; all appear to have the same 3' end. The four smallest J69-1B transcripts (1,900, 1,700, 800 and 600 nucleotides) contain only sequences down-stream of the oli2 gene. A 1.8 kb DNA region specifying these four transcripts is deleted from grande strain JM6 (class 11); these transcripts are thus dispensible for respiratory function. The five oli2 transcripts of JM6 (3,000, 2,400 (most prominent), 2,000, 1,700 and 1,150 nucleotides) all contain the oli2 coding sequence and are each related to a corresponding J69-1B transcript; the 5' and 3' ends match in each case, but the JM6 transcripts are about 2,000 nucleotides shorter. In particular, the putative oli2 mRNA has a 5' leader of about 1,400 nucleotides, a coding region of 780 nucleotides, and a variant 3' tail that is about 2,300 nucleotides in J69-1 B, and about 200 nucleotides in JM6.