STRUCTURE OF MINICIRCLE KINETOPLAST DNA FROM A RIVER PERCH TRYPANOSOME

For the first time the complete primary structure (1599 bp) was determ ined for a minicircle kinetoplast DNA (kpDNA) of a lower-vertebrate tr ypanosome. Some features were common with all Trypanosomatidae minicir cles, such as the presence of conserved and variable regions within on e minicircle, and invariant dodecameric 5'-d(GGGGTTGGTGTA>-3' and hexa meric 5'-d(GGGCGT)-3' sequences. On the other hand, the kpDNA under st udy had some features distinguishing it from the minicircles of higher -vertebrate trypanosomes. It proved to be an incomplete dimer based on two unversal dodecamers as the nuclei of symmetry, the sequences arou nd which form a 130-bp direct repeat with a few substitutions. No bent -helix structures were found. The regions of maximal homology between the minicircle examined and those of other trypanosomatids formed disc rete clusters along the molecule. PCR analysis demonstrated that such dimeric type of organization (with two conserved regions) is typical o f many minicircle kpDNAs from freshwater fish trypanosomes. At the sam e time, the kpDNA associates of the latter appear to contain a minor p ortion of minicircles with a single conserved region.