The Killing of African Trypanosomes by Ethidium Bromide

摘要: Introduced in the 1950s, ethidium bromide (EB) is still used as an anti-trypanosomal drug for African cattle although its mechanism of killing has been unclear and controversial. EB long known to cause loss mitochondrial genome, named kinetoplast DNA (kDNA), a giant network interlocked minicircles maxicircles. However, existence viable parasites lacking kDNA (dyskinetoplastic) led many think that could not be killing. When recent studies indicated indeed essential bloodstream trypanosomes dyskinetoplastic cells survive only if they have compensating mutation nuclear we investigated effect on replication. We here report some remarkable effects EB. Using EM other techniques, found binding low, probably because their association with proteins prevent helix unwinding. In contrast, covalently-closed had released from replication bind extensively, causing them, after isolation, become highly supertwisted develop regions left-handed Z-DNA (without EB, these circles are fully relaxed). vivo, causes distortion free minicircles, preventing initiation resulting cell death. Unexpectedly, also kills trypanosomes, kDNA, by inhibiting Since occurs at >10-fold lower concentration than DNA, conclude minicircle likely EB's most vulnerable target, but may contribute