Interactions of TMPyP4 and TMPyP2 with quadruplex DNA. Structural basis for the differential effects on telomerase inhibition
Interactions of TMPyP4 and TMPyP2 with quadruplex DNA. Structural basis for the differential effects on telomerase inhibition
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DOI：
10.1021/ja984153m
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发表时间：
1999-04-21
影响因子：
15
通讯作者：
Hurley, LH
中科院分区：
文献类型：
--
作者：
Han, FXG;Wheelhouse, RT;Hurley, LH
阳离子卟啉TMPyP4和TMPyP2具有相似的结构，但具有显著不同的端粒酶抑制活性。为了解释这种差异，我们研究了TMPyP4和TMPyP2与反平行四链DNA的相互作用。设计了一个含有四个人端粒重复序列的单链DNA寡核苷酸(G4A)，形成了分子内四链DNA，并通过DNA连接酶分析、DMS足迹分析和圆二色谱分析证实了G4A在100 mM KCl中形成了这种结构。通过对G4A-卟啉络合物的热熔融曲线的紫外光谱研究，我们提供了TMPyP4和TMPyP2对四链DNA稳定程度大致相同的证据。用光切割实验确定TMPyP4和TMPyP2与四链DNA相互作用的精确位置。结果表明，TMPyP4与分子内四链DNA的结合方式是在GT步骤的鸟嘌呤四聚体的外部，而TMPyP2主要是通过与TTA环的外部结合与相同的G4 DNA结构结合。我们认为，TMPyP2不能通过堆积在鸟嘌呤四元体的外部与G4A结合，这是TMPyP4和TMPyP2对端粒酶抑制作用不同的原因。
The cationic porphyrins TMPyP4 and TMPyP2 possess similar structures but have strikingly different potencies for telomerase inhibition. To rationalize this difference, the interactions of TMPyP4 and TMPyP2 with an antiparallel quadruplex DNA were investigated. A single-stranded DNA oligonucleotide (G4A) containing four human telomere repeats of GGGTTA has been designed to form an intramolecular quadruplex DNA and was confirmed to form such a structure under 100 mM KCl by a DNA ligase assay, DMS footprinting, and CD spectrum analysis. By carrying out UV spectroscopic studies of the thermal melting profiles of G4A-porphyrin complexes, we provide evidence that TMPyP4 and TMPyP2 both stabilize quadruplex DNA to about the same extent. A photocleavage assay was used to determine the precise location for TMPyP4 and TMPyP2 in their interactions with quadruplex DNA. The results shaw that TMPyP4 binds to the intramolecular quadruplex DNA by stacking externally to the guanine tetrad at the GT step, while TMPyP2 binds predominantly to the same G4 DNA structure via external binding to the TTA loop. We propose that the inability of TMPyP2 to bind to the G4A by stacking externally to the guanine tetrad accounts for the differential effects on telomerase inhibition by TMPyP4 and TMPyP2.