Kinetoplast-associated DNA topoisomerase in Crithidia fasciculata: crosslinking of mitochondrial topoisomerase II to both minicircles and maxicircles in cells treated with the topoisomerase inhibitor VP16

摘要

The mitochondrial DNA of the trypanosomatid Crithidia fasciculate consists of thousands of copies of a 2.5 kb mlnlcircle and a small number of 37kb maxicircles catenated into a single enormous network. Treatment of C. fasciculata with the type II DNA topoisomerase Inhibitor VP16 produces cleavable complexes of a type II DNA topoisomerase with both minicircles and maxicircles. A combined Southern and Western blot analysis of the cleaved DNA species released from the network by SDS treatment has Identified topollmt, the kinetoplast-associated topoisomerase, in covalent complexes with linear forms of minicircle and maxicircle DNAs. These results directly implicate topollmt in the topological reactions required for the duplication of the klnetoplast network.