Structure variations of TBA G-quadruplex induced by 2'-O-methyl nucleotide in K+ and Ca2+ environments.
Structure variations of TBA G-quadruplex induced by 2'-O-methyl nucleotide in K+ and Ca2+ environments.
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DOI：
10.1093/abbs/gmu077
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发表时间：
2014-10
影响因子：
3.7
通讯作者：
Xiaoyang Zhao;Bo Liu;Jing Yan;Ying Yuan;Liwen An;Y. Guan
中科院分区：
文献类型：
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作者：
Xiaoyang Zhao;Bo Liu;Jing Yan;Ying Yuan;Liwen An;Y. Guan
凝血酶结合适体(TBA)是D(GGTTGGGTGTGGGGTTGGTTGG)序列的15聚体寡核苷酸，在K(+)环境中折叠成椅型反平行G-四联体，两个G-四联体都具有同步-反-反糖苷构象。为了探索其折叠拓扑结构和结构稳定性，用具有C3‘-内糖折叠构象和反糖苷角的2’-O-甲基核苷酸(OME)选择性地取代TBA的G-四元体鸟嘌呤残基，并用圆二色谱、热差光谱、紫外稳定性分析、凝胶迁移率分析和热力学分析对其在K(+)和Ca(2+)环境中的结构进行了表征。结果表明，单一取代syn-dG残基会破坏G-四链体结构的稳定性，而单一取代抗dG残基可以在K(+)环境中保持G-四链体结构。当一个或两个G-四分体被OME修饰时，TBA变得无结构。相反，在Ca(2+)环境中，天然的TBA似乎是非结构化的。当两个G-四分体被OME取代时，TBA似乎成为更稳定的平行G-4结构。进一步的热力学数据表明，OMe取代是由热焓驱动的事件。本研究结果丰富了我们对核苷酸衍生物在不同离子环境下对G-四链体结构稳定性影响的认识，为设计具有生物和医学应用的G-四链体奠定了基础。
Thrombin binding aptamer (TBA), a 15-mer oligonucleotide of d(GGTTGGTGTGGTTGG) sequence, folds into a chair-type antiparallel G-quadruplex in the K(+) environment, and each of two G-tetrads is characterized by a syn-anti-syn-anti glycosidic conformation arrangement. To explore its folding topology and structural stability, 2'-O-methyl nucleotide (OMe) with the C3'-endo sugar pucker conformation and anti glycosidic angle was used to selectively substitute for the guanine residues of G-tetrads of TBA, and these substituted TBAs were characterized using a circular dichroism spectrum, thermally differential spectrum, ultraviolet stability analysis, electrophoresis mobility shift assay, and thermodynamic analysis in K(+) and Ca(2+) environments. Results showed that single substitutions for syn-dG residues destabilized the G-quadruplex structure, while single substitutions for anti-dG residues could preserve the G-quadruplex in the K(+) environment. When one or two G-tetrads were modified with OMe, TBA became unstructured. In contrast, in Ca(2+) environment, the native TBA appeared to be unstructured. When two G-tetrads were substituted with OMe, TBA seemed to become a more stable parallel G-4 structure. Further thermodynamic data suggested that OMe-substitutions were an enthalpy-driven event. The results in this study enrich our understanding about the effects of nucleotide derivatives on the G-quadruplex structure stability in different ionic environments, which will help to design G-quadruplex for biological and medical applications.