Characterization of structure and stability of long telomeric DNA G-quadruplexes
Characterization of structure and stability of long telomeric DNA G-quadruplexes
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DOI：
10.1021/ja064536h
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发表时间：
2006-12-06
影响因子：
15
通讯作者：
Sugimoto, Naoki
中科院分区：
文献类型：
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作者：
Yu, Hai-Qing;Miyoshi, Daisuke;Sugimoto, Naoki
在目前的研究中，我们使用了凝胶电泳，圆二色性，UV熔解分析相结合，以调查的结构和稳定性的G-四链体形成的长端粒DNA从尖毛藻和人类，其中重复的长度（n）= 4至12。我们发现具有序列（TTTTGGGG）（n）的尖毛霉端粒DNA根据离子条件折叠成分子内和分子间G-四链体，而具有序列（TTAGGG）n的人端粒DNA在所有测试条件下仅形成分子内G-四链体。我们进一步估算了分子内G-四链体的热力学参数。我们发现，G-四链体结构的长端粒DNA（n = 5至12）的热力学稳定性大多是独立的序列长度，虽然端粒DNA更稳定，当n = 4比当n >= 5。最重要的是，当n是4的倍数时，G-四链体形成的焓和熵的变化逐渐增加，表明单个G-四链体单元由四个重复组成，并且单个单元不相互作用。因此，我们提出由长端粒DNA（n >= 8）形成的G-四链体是珠串结构，其中G-四链体单元通过一个TTTT（Oxytricha）或TTA（human）接头连接。这些结果将有助于理解端粒的结构和功能，并为开发改进的治疗药物靶向端粒DNA。
In the current study, we used a combination of gel electrophoresis, circular dichroism, and UV melting analysis to investigate the structure and stability of G-quadruplexes formed by long telomeric DNAs from Oxytricha and human, where the length of the repeat (n) = 4 to 12. We found that the Oxytricha telomeric DNAs, which have the sequence (TTTTGGGG)(n), folded into intramolecular and intermolecular G-quadruplexes depending on the ionic conditions, whereas human telomeric DNAs, which have the sequence (TTAGGG) n, formed only intramolecular G-quadruplexes in all the tested conditions. We further estimated the thermodynamic parameters of the intramolecular G-quadruplex. We found that thermodynamic stabilities of G-quadruplex structures of long telomeric DNAs (n = 5 to 12) are mostly independent of sequence length, although telomeric DNAs are more stable when n = 4 than when n >= 5. Most importantly, when n is a multiple of four, the change in enthalpy and entropy for G-quadruplex formation increased gradually, demonstrating that the individual G-quadruplex units are composed of four repeats and that the individual units do not interact. Therefore, we propose that the G-quadruplexes formed by long telomeric DNAs (n >= 8) are bead-on-a-string structures in which the G-quadruplex units are connected by one TTTT (Oxytricha) or TTA (human) linker. These results should be useful for understanding the structure and function of telomeres and for developing improved therapeutic agents targeting telomeric DNAs.