Mapping and 5′ end determination of kinetoplast maxicircle gene transcripts from Leishmania tarentolae

Transcripts for six Leishmania tarentolse maxicircle structural genes (cytochrome oxidase subunits I, II and III, cytochrome b, human mitochondrial unidentified reading frames 4 and 5) and several unidentified open reading frames were mapped, and the locations of the 5′ ends determined by primer runoff analysis. All genes studied here are transcribed from the same strand as the 12$ and 9$ ribosomal RHAs except for the cytochrome oxidase subunit I gene. In two cases (ORF3 and ORF4, ORF5 and 0RF6), a single transcript covers two contiguous overlapping readinge frames. The 5′ ends of the RMAs are located 20-64 nt from the putative translation initiation codons. Primary transcripts from a mitochondrial RNA preparation were 5′ end-labeled with guanylyltransferase and ∞-32P-GTP; the major labeled species comigrated with the 12$ and 9$ mitochondrial rRNAs, and in addition there were at least four higher molecular weight labeled species.