KINETOPLAST DNA MINICIRCLES OF TRYPANOSOMA-BRUCEI SHARE REGIONS OF SEQUENCE HOMOLOGY

Kinetoplast DNA (kDNA) of Trypanosoma brucei consists of massive networks of 10,000 or more interlocked molecules of maxicircle DNA (about 23 kb each) and minicircle DNA (1.1 kb each). Individual minicircle DNA molecules were released from the network by digestion with HaeIII, HpaII, AluI, HhaI, PstI, or HindIII and cloned in E. coli via the plasmid pBR322 and the poly(dG):poly(dC) tailing technique or the DNA ligase technique. The cloned minicircle DNA molecules were compared (i) by two types of filter hybridization, (ii) by renaturation kinetics, and (iii) by heteroduplex analysis. The sequence complexity of total network kDNA is about 300 times that of a single cloned minicircle kDNA molecule. The filter hybridizations and heteroduplex analyses suggest that minicircle molecules possess sequences in common with each other. The renaturation kinetics indicates that these homologous regions comprise about one-fourth of the 1.1-kb minicircle molecule. Therefore each minicircle molecule appears to have about one-fourth of its sequence in common with a large percentage of the total minicircle population and the remaining three-fourths in common with about 1 out of 300 minicircle molecules. © 1979.