Wang L K, Rogers B D, Hecht S M
Department of Chemistry, University of Virginia, Charlottesville 22901, USA.
Chem Res Toxicol. 1996 Jan-Feb;9(1):75-83. doi: 10.1021/tx950080y.
The antitumor agent coralyne and a number of structural analogues were found to be inhibitors of DNA topoisomerase I and were characterized biochemically. Several of these analogues stabilized the covalent binary complex formed between calf thymus topoisomerase I and pSP64 plasmid DNA; coralyne and 5,6-dihydrocoralyne had the greatest potency as inhibitors in this assay. In common with camptothecin, the effects of coralyne and 5,6-dihydrocoralyne were reversed in the presence of increasing salt concentration or temperature, consistent with the interpretation that both functioned mechanistically in a fashion analogous to camptothecin. The sequence specificity of DNA cleavage by coralyne and 5,6-dihydrocoralyne was also studied in comparison with camptothecin using a 471-bp DNA duplex as a substrate for topoisomerase I. Seven sites of cleavage were apparent, four of which were shared in common by coralyne, 5,6-dihydrocoralyne and camptothecin. Coralyne and 5,6-dihydrocoralyne produced cleavage at one sequence, 5'-TCTC decreases GTAA=3', that was not apparent in the presence of camptothecin; correspondingly, two cleavage bands appeared only when camptothecin was present. Coralyne and 5,6-dihydrocoralyne also inhibited topoisomerase I-mediated relaxation of supercoiled plasmid DNA. Coralyne was the most potent inhibitor of DNA relaxation; the effects of camptothecin and 5,6-dihydrocoralyne were roughly equal. At high concentrations, coralyne completely suppressed the formation of the topoisomerase I-DNA covalent binary complex.
抗肿瘤药物珊瑚碱及一些结构类似物被发现是DNA拓扑异构酶I的抑制剂，并对其进行了生化特性分析。其中几种类似物稳定了小牛胸腺拓扑异构酶I与pSP64质粒DNA形成的共价二元复合物；在该检测中，珊瑚碱和5,6-二氢珊瑚碱作为抑制剂的效力最强。与喜树碱一样，随着盐浓度或温度升高，珊瑚碱和5,6-二氢珊瑚碱的作用会逆转，这与二者在作用机制上与喜树碱类似的解释一致。还使用471碱基对的DNA双链体作为拓扑异构酶I的底物，与喜树碱比较研究了珊瑚碱和5,6-二氢珊瑚碱切割DNA的序列特异性。明显有7个切割位点，其中4个是珊瑚碱、5,6-二氢珊瑚碱和喜树碱共有的。珊瑚碱和5,6-二氢珊瑚碱在一个序列（5'-TCTC decreases GTAA=3'）处产生切割，而在喜树碱存在时不明显；相应地，只有在喜树碱存在时才出现两条切割带。珊瑚碱和5,6-二氢珊瑚碱还抑制拓扑异构酶I介导的超螺旋质粒DNA的松弛。珊瑚碱是DNA松弛的最有效抑制剂；喜树碱和5,6-二氢珊瑚碱的作用大致相当。在高浓度下，珊瑚碱完全抑制拓扑异构酶I-DNA共价二元复合物的形成。
