Arrest of replication forks by drug-stabilized topoisomerase I-DNA cleavable complexes as a mechanism of cell killing by camptothecin.
Arrest of replication forks by drug-stabilized topoisomerase I-DNA cleavable complexes as a mechanism of cell killing by camptothecin.
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发表时间：
1989-09
期刊：
影响因子：
11.2
通讯作者：
Y. Hsiang;M. G. Lihou;Leroy F. Liu
中科院分区：
文献类型：
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作者：
Y. Hsiang;M. G. Lihou;Leroy F. Liu
喜树碱通过将细胞拓扑异构酶I以药物 - 酶 - DNA可切割复合物的形式捕获在染色体DNA上，诱导一种不同寻常的DNA损伤类型，它抑制DNA合成并特异性地杀死S期细胞。用复制型DNA聚合酶抑制剂阿非迪霉素共同处理L1210细胞，完全消除了喜树碱的细胞毒性，这表明DNA复制参与了喜树碱的细胞毒性。为了研究DNA复制在药物作用中的作用，本研究使用了无细胞的SV40 DNA复制系统。在无细胞系统中，只有在拓扑异构酶I存在的情况下，喜树碱才会抑制SV40 DNA复制。在喜树碱存在的情况下，向该提取系统中添加过量纯化的小牛胸腺DNA拓扑异构酶I，会导致SV40 DNA复制受到严重抑制以及线性化复制产物的积累，这些产物含有共价结合的DNA拓扑异构酶I。我们提出，移动的复制叉与喜树碱稳定的拓扑异构酶I - DNA可切割复合物之间的碰撞导致复制叉停滞，并可能导致复制叉断裂，这对增殖细胞是致命的。
Camptothecin, which induces an unusual type of DNA damage by trapping cellular topoisomerase I on chromosomal DNA in the form of drug-enzyme-DNA cleavable complexes, inhibits DNA synthesis and specifically kills S-phase cells. Cotreatment of L1210 cells with aphidicolin, which is an inhibitor of replicative DNA polymerases, completely abolished camptothecin cytotoxicity, suggesting the involvement of DNA replication in camptothecin cytotoxicity. In order to study the role of DNA replication in drug action, a cell-free SV40 DNA replication system was used in the present study. Camptothecin inhibited SV40 DNA replication in this cell-free system only in the presence of topoisomerase I. Addition of excess purified calf thymus DNA topoisomerase I to this extract system in the presence of camptothecin resulted in severe inhibition of SV40 DNA replication and the accumulation of linearized replication products, which contained covalently bound DNA topoisomerase I. We propose that the collision between moving replication forks and camptothecin-stabilized topoisomerase I-DNA cleavable complexes results in fork arrest and possibly fork breakage, which are lethal to proliferating cells.