Transcription of kinetoplast DNA in Trypanosoma brucei bloodstream and culture forms.

Kinetoplast DNA is the unusual mitochondrial DNA of trypanosomes. In Trypanosoma brucei it consists of about lo* minicircles (0.3 km) and lo* maxicircles (6 pm) catenated into a single network. The maxicircles are probably the equivalent of mitochondrial DNA in other organisms. Here we report that a fraction of the total cellular RNA from bloodstream form and culture form T. brucei hybridizes with the maxicircle; we find no minicircle transcripts. Preferential hybridization with a 1 .8-kb2 maxicircle segment is shown to be due to two abundant RNA species, the 9 S and 12 S RNAs. After glyoxylation the apparent size of these putative rRNAs in gels is 1080 and 590 nucleofides, respectively; they are present in approximately equimolar amounts, lack poly(A) tails, their genes are adjacent, and they are transcribed from the same strand in the order 12 S-9 S. Six’additional RNA species, varying in size from 360 to 1110 nucleotides, are transcribed from segments covering 50% of the maxicircle. These transcripts are specifically retained on oligo(dT)-cellulose and presumably represent mitochondrial messenger RNAs. Recombinant DNA plasmids containing DNA