Weissig V, Vetro-Widenhouse T S, Rowe T C
Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville 32610-0267, USA.
DNA Cell Biol. 1997 Dec;16(12):1483-92. doi: 10.1089/dna.1997.16.1483.
The topoisomerase II-specific inhibitors VP-16 and ciprofloxacin were used to investigate the presence of topoisomerase II activities associated with nuclear and 35-kb plastid DNAs of the malarial parasite Plasmodium falciparum. The eukaryotic topoisomerase II inhibitor VP-16 induced cleavage of both nuclear and 35-kb parasite DNAs. In contrast, ciprofloxacin, a fluoroquinolone drug known to act on the bacterial type II topoisomerase DNA gyrase, only induced cleavage of the Plasmodial 35-kb DNA. Drug-induced cleavage resulted in the protection of the 5'- but not 3'- ends of the cleaved nuclear and 35-kb DNAs from exonuclease digestion, suggesting that the 5'-ends of the broken DNA were protein-linked, a property reminiscent of DNA cleavage mediated by topoisomerase II enzymes. Furthermore, DNA cleavage induced by both VP-16 and ciprofloxacin was heat-reversible. This is the first evidence that P. falciparum contains two distinct topoisomerase II activities that are molecular targets for chemotherapeutic agents.
拓扑异构酶II特异性抑制剂依托泊苷（VP - 16）和环丙沙星被用于研究恶性疟原虫核DNA和35 kb质体DNA相关的拓扑异构酶II活性的存在情况。真核拓扑异构酶II抑制剂依托泊苷（VP - 16）可诱导核DNA和35 kb疟原虫DNA的断裂。相比之下，已知作用于细菌II型拓扑异构酶DNA促旋酶的氟喹诺酮类药物环丙沙星，仅能诱导疟原虫35 kb DNA的断裂。药物诱导的断裂导致切割后的核DNA和35 kb DNA的5'端而非3'端受到核酸外切酶消化的保护，这表明断裂DNA的5'端与蛋白质相连，这一特性类似于拓扑异构酶II介导的DNA切割。此外，依托泊苷（VP - 16）和环丙沙星诱导的DNA切割是热可逆的。这是首次有证据表明恶性疟原虫含有两种不同的拓扑异构酶II活性，它们是化疗药物的分子靶点。
