Tosh K, Cheesman S, Horrocks P, Kilbey B
Institute of Cell and Molecular Biology, University of Edinburgh, United Kingdom.
Exp Parasitol. 1999 Feb;91(2):126-32. doi: 10.1006/expr.1998.4362.
The expression and activity of topoisomerase I (PfTopoI) has been examined during the intraerythrocytic stages of the Plasmodium falciparum life cycle. The promoter is inactive during the early ring stage and becomes active only during the later trophozoite and schizont stages. The PfTOP1 transcript starts to accumulate in the trophozoite stage parasite, decreasing again in the schizont stage. Using both stage-specific Western analysis and immunofluorescent assays we show that PfTopoI is present at low levels in rings and accumulates to approximately equal levels in the trophozoite and schizont stages. Experiments to determine the activity of PfTopoI, using a topoisomerase I relaxation assay, show that there is a low level of PfTopoI activity in both ring and trophozoite stages, but activity increases dramatically in the schizont stage. The PfTopoI activity can be inhibited by treatment with specific antiserum and by the type I topoisomerase-specific inhibitor camptothecin.
在恶性疟原虫生命周期的红细胞内阶段，对拓扑异构酶I（PfTopoI）的表达和活性进行了检测。启动子在早期环状体阶段无活性，仅在后期滋养体和裂殖体阶段才变得活跃。PfTOP1转录本在滋养体阶段的寄生虫中开始积累，在裂殖体阶段又再次减少。使用阶段特异性蛋白质免疫印迹分析和免疫荧光测定，我们发现PfTopoI在环状体中含量较低，而在滋养体和裂殖体阶段积累到大致相同的水平。使用拓扑异构酶I松弛测定法来确定PfTopoI活性的实验表明，在环状体和滋养体阶段PfTopoI活性水平较低，但在裂殖体阶段活性显著增加。PfTopoI活性可通过用特异性抗血清处理以及用I型拓扑异构酶特异性抑制剂喜树碱处理来抑制。
