Xu Z, Li T K, Kim J S, LaVoie E J, Breslauer K J, Liu L F, Pilch D S
Department of Pharmacology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway 08854, USA.
Biochemistry. 1998 Mar 10;37(10):3558-66. doi: 10.1021/bi9727747.
We have employed a broad range of spectroscopic, calorimetric, DNA cleavage, and DNA winding/unwinding measurements to characterize the DNA binding and topoisomerase I (TOP1) poisoning properties of three terbenzimidazole analogues, 5-phenylterbenzimidazole (5PTB), terbenzimidazole (TB), and 5-(naphthyl[2,3-d]imidazo-2-yl)bibenzimidazole (5NIBB), which differ with respect to the substitutions at their C5 and/or C6 positions. Our results reveal the following significant features. (i) The overall extent to which the three terbenzimidazole analogues poison human TOP1 follows the hierarchy 5PTB > TB >> 5NIBB. (ii) The impact of the three terbenzimidazole analogues on the superhelical state of plasmid DNA depends on the [total ligand] to [base pair] ratio (rbp), having no effect on DNA superhelicity at rbp ratios < or = 0.1, while weakly unwinding DNA at rbp ratios > 0.1. This weak DNA unwinding activity exhibited by the three terbenzimidazoles does not appear to be correlated with the abilities of these compounds to poison TOP1. (iii) Upon complexation with both poly(dA).poly(dT) and salmon testes DNA, the three terbenzimidazole analogues exhibit flow linear dichroism properties characteristic of a minor groove-directed mode of binding to these host DNA duplexes. (iv) The apparent minor groove binding affinities of the three terbenzimidazole analogues for the d(GA4T4C)2 duplex follow a qualitatively similar hierarchy to that noted above for ligand-induced poisoning of human TOP1-namely, 5PTB > TB > 5NIBB. In the aggregate, our results suggest that DNA minor groove binding, but not DNA unwinding, is important in the poisoning of TOP1 by terbenzimidazoles.
我们采用了广泛的光谱、量热、DNA切割以及DNA缠绕/解旋测量方法，来表征三种三联苯并咪唑类似物，即5-苯基三联苯并咪唑（5PTB）、三联苯并咪唑（TB）和5-（萘基[2,3-d]咪唑-2-基）联苯并咪唑（5NIBB）的DNA结合和拓扑异构酶I（TOP1）中毒特性，这三种类似物在其C5和/或C6位置的取代情况有所不同。我们的结果揭示了以下显著特征。（i）三种三联苯并咪唑类似物使人类TOP1中毒的总体程度遵循5PTB > TB >> 5NIBB的顺序。（ii）三种三联苯并咪唑类似物对质粒DNA超螺旋状态的影响取决于[总配体]与[碱基对]的比例（rbp），在rbp比例≤0.1时对DNA超螺旋性无影响，而在rbp比例>0.1时会使DNA轻微解旋。这三种三联苯并咪唑表现出的这种微弱的DNA解旋活性似乎与这些化合物使TOP1中毒的能力无关。（iii）与聚（dA）·聚（dT）和鲑鱼精巢DNA络合后，三种三联苯并咪唑类似物表现出与这些宿主DNA双链体小沟定向结合模式相关的流动线性二色性特性。（iv）三种三联苯并咪唑类似物对d（GA4T4C）2双链体的表观小沟结合亲和力遵循与上述配体诱导人类TOP1中毒情况定性相似的顺序，即5PTB > TB > 5NIBB。总体而言，我们的结果表明，DNA小沟结合而非DNA解旋在三联苯并咪唑使TOP1中毒过程中起重要作用。
