Maxi-circles are a minor component of kinetoplast DNAs from all trypanosomatids studied, but they have not previously been found in Trypanosoma cruzi; We have spread intact kinetoplast DNA from the epimastigotes of strain Y in protein monolayers and analysed the mini-circle networks by electron microscopy. Long loops up to 10 micrometer were present, extending from the network rim; these are considered typical of maxi-circles.The presence of maxi-circles was proven by digestion of kinetoplast DNA with restriction endonucleases and S1 nuclease. This released a minor DNA component, detectable by agarose gel electrophoresis, which hybridized to maxi-circle DNA from Trypanosoma brucei. The molecular weight of the linearized maxi-circle of Trypanosoma cruzi is 26 . 10(6), as judged from its electrophoretic mobility in 0.6% agarose. Our restriction enzyme analysis of the mini-circles of Trypanosoma cruzi has confirmed their sequence heterogeneity and internally-repeated structure. We have found that more than 90% of the mini-circles are cut into 1/4 length molecules by endonuclease TaqI. Denaturation and renaturation of mini-circles, cut once with endonuclease MboI, mainly yields linear and circular molecules with single-stranded eyes and tails in electron micrographs. This shows that 1/4 repeats contain sub-segments in which sequence divergence is extensive. Our EcoRI and HapII digests differ in fragment size distribution from those previously reported. This suggests that this distribution may not be a stable characteristic of the Y strain.

9007-49-2 (dna), Animals, DNA Restriction Enzymes, DNA/*analysis, EC 3.1.21 (DNA Restriction Enzymes), Electrophoresis, Agar Gel, Microscopy, Electron, Molecular Weight, Nucleic Acid Hybridization, Trypanosoma cruzi/*analysis
hdl.handle.net/1765/2951
Biochimica et Biophysica Acta - General Subjects
Erasmus MC: University Medical Center Rotterdam

Leon, W, Frasch, A.C.C, Hoeijmakers, J.H.J, Fase-Fowler, F, Borst, P, Brunel, F, & Davison, J. (1980). Maxi-circles and mini-circles in kinetoplast DNA from Trypanosoma cruzi. Biochimica et Biophysica Acta - General Subjects, 607, 221–231. Retrieved from http://hdl.handle.net/1765/2951