Zf. Wang et Pt. Englund, RNA interference of a trypanosome topoisomerase II causes progressive lossof mitochondrial DNA, EMBO J, 20(17), 2001, pp. 4674-4683
We studied the function of a Trypanosoma brucei topoisomerase II using RNA
interference (RNAi). Expression of a topoisomerase II double-stranded RNA a
s a stem-loop caused specific degradation of mRNA followed by loss of prote
in. After 6 days of RNAi, the parasites' growth rate declined and the cells
subsequently died. The most striking phenotype upon induction of RNAi was
the loss of kinetoplast DNA (kDNA), the cell's catenated mitochondrial DNA
network. The loss of kDNA was preceded by gradual shrinkage of the network
and accumulation of gapped free minicircle replication intermediates. These
facts, together with the localization of the enzyme in two antipodal sites
flanking the kDNA, show that a function of this topoisomerase II is to att
ach free minicircles to the network periphery following their replication.