Selective interactions of cationic porphyrins with G-quadruplex structures
Selective interactions of cationic porphyrins with G-quadruplex structures
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DOI：
10.1021/ja002179j
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发表时间：
2001-09-19
影响因子：
15
通讯作者：
Hurley, LH
中科院分区：
文献类型：
--
作者：
Han, HY;Langley, DR;Hurley, LH
G-四链DNA为设计和开发新型抗癌药物提供了一个潜在的靶点。由于G-四链DNA表现出结构多态，不同的G-四链类型可能与不同的细胞过程有关。因此，为了利用G-四链作为药物设计的靶点来实现治疗的选择性，有必要使用G-四链相互作用剂来区分不同类型的G-四链。在这项研究中，我们通过凝胶迁移率改变实验和解旋酶实验比较了三种阳离子卟啉TMPyP2、TMPyP3和TMPyP4与平行和反平行类型的G-四链体的相互作用。凝胶迁移率移动实验表明，TMPyP3特异性地促进了平行G-四链体结构的形成。G-四链解旋酶解离实验表明，这三种卟啉在阻止酵母SGS1解旋酶(SGS1p)对平行四聚体G-四链体和反平行发夹二聚体G-四链体DNA解离的能力上存在很大差异。对于平行的G-四链，TMPyP3对Sgs1p的抑制作用最强，TMPyP4次之，而对反平行的G-四链的抑制作用则相反。TMPyP2似乎对解旋酶催化的两种类型的G-四链的解离都没有任何影响。用光裂解实验研究了三种卟啉与平行G-四链体的结合方式。结果表明，TMPyP3和TMPyP4似乎是通过末端的外部堆积结合到平行的G-四链结构上，而不是通过插入G-四联体。由于G-四联体之间的插层先前被认为是TMPyP4到G-四链体的一种替代结合模式，所以这种结合模式与这里描述的光切割分析(外部堆积)所确定的结合模式相比，被分子动力学计算来确定络合物的相对稳定性和导致这些差异的因素。外部结合模式的DeltaG度被发现由DeltaH度驱动，具有小的不利的T Deltaas度项。插层结合模型的DeltaG度由大的T Deltaas度项驱动，并由小的DeltaH度项补充。外键模型的主要稳定成分之一是溶剂化能，它比插层模型的溶剂化能高-67.94kcal/mol。最后，我们认为，虽然插层结合不像外部结合那么有利，但由于插层结合的性质，它对于光切割分析是不可见的。这项研究首次对如何通过在一组G-四链相互作用药物中使用结构变体来实现不同G-四链的选择性提供了实验见解。
G-quadruplex DNA presents a potential target for the design and development of novel anticancer drugs. Because G-quadruplex DNA exhibits structural polymorphism, different G-quadruplex typologies may be associated with different cellular processes. Therefore, to achieve therapeutic selectivity using G-quadruplexes as targets for drug design, it will be necessary to differentiate between different types of G-quadruplexes using G-quadruplex-interactive agents. In this study, we compare the interactions of three cationic porphyrins, TMPyP2, TMPyP3, and TMPyP4, with parallel and antiparallel types of G-quadruplexes using gel mobility shift experiments and a helicase assay. Gel mobility shift experiments indicate that TMPyP3 specifically promotes the formation of parallel G-quadruplex structures. A G-quadruplex helicase unwinding assay reveals that the three porphyrins vary dramatically in their abilities to prevent the unwinding of both the parallel tetrameric G-quadruplex and the antiparallel hairpin dimer G-quadruplex DNA by yeast Sgs1 helicase (Sgs1p). For the parallel G-quadruplex, TMPyP3 has the strongest inhibitory effect on Sgs1p, followed by TMPyP4, but the reverse is true for the antiparallel G-quadruplex. TMPyP2 does not appear to have any effect on the helicase-catalyzed unwinding of either type of G-quadruplex. Photocleavage experiments were carried out to investigate the bindin- modes of all three porphyrins with parallel G-quadruplexes. The results reveal that TMPyP3 and TMPyP4 appear to bind to parallel G-quadruplex structures through external stacking at the ends rather than through intercalation between the G-tetrads. Since intercalation between G-tetrads has been previously proposed as an alternative binding mode for TMPyP4 to G-quadruplexes, this mode of binding, versus that determined by a photocleavage assay described here (external stacking), was subjected to molecular dynamics calculations to identify the relative stabilities of the complexes and the factors that contribute to these differences. The DeltaG degrees for the external binding mode was found to be driven by DeltaH degrees with a small unfavorable T DeltaS degrees term. The DeltaG degrees for the intercalation binding model was driven by a large T DeltaS degrees term and complemented by a small DeltaH degrees term. One of the main stabilizing components of the external binding model is the energy of solvation, which favors the external model over the intercalation model by -67.94 kcal/mol. Finally, we propose that intercalative binding, although less favored than external binding, may occur, but because of the nature of the intercalative binding, it is invisible to the photocleavage assay. This study provides the first experimental insight into how selectivity might be achieved for different G-quadruplexes by using structural variants within a single group of G-quadruplex-interactive drugs.