De. Ochs et al., MAXICIRCLE GENOMIC ORGANIZATION AND EDITING OF AN ATPASE SUBUNIT-6 RNA IN TRYPANOSOMA-CRUZI, Molecular and biochemical parasitology, 76(1-2), 1996, pp. 267-278
The DNA sequence of a 5736-nucleotide (nt) Trypanosoma cruzi maxicircl
e fragment was determined. Sequence comparisons indicate that its 5' t
erminus is the homologue of the downstream portion of the NADH dehydro
genase subunit 7 gene and that its 3' region is homologous to the maxi
circle unidentified reading frame II gene. The region between these tw
o gene segments contains six additional genes that encode mitochondria
l proteins, including ATPase subunit 6 (A6). Comparison of the A6 maxi
circle DNA sequence with that of an A6 cDNA indicates that the A6 RNA
is extensively edited throughout its length. A 49-nt sequence that cou
ld serve as template for transcription of a guide RNA for editing a se
gment of the A6 RNA was found in one of 24 minicircle variable regions
sequenced. Moreover, the presence of an RNA having this sequence was
demonstrated in an RNAse protection assay. This is the first identific
ation of a guide RNA template in a T. cruzi minicircle. Taken together
, our findings suggest that T, cruzi and Trypanosoma brucei brucei are
phylogenetically closer to each other than they are to Leishmania tar
entolae, despite the relative similarity of the life cycles of the lat
ter and T. cruzi.