Extreme conformational diversity in human telomeric DNA
Extreme conformational diversity in human telomeric DNA
复制标题
DOI：
10.1073/pnas.0506144102
复制
发表时间：
2005-12-27
影响因子：
11.1
通讯作者：
Ha, TJ
中科院分区：
文献类型：
--
作者：
Lee, JY;Okumus, B;Ha, TJ
带有串联重复的鸟嘌呤的DNA折叠成由一堆G-四联体组成的G-四联体。在体外，G-四链的形成抑制了端粒的延伸，POT1与单链端粒DNA的结合通过破坏G-四链结构而增强了端粒酶的活性，突显了G-四链结构在体内调节端粒长度的潜在重要性。我们已经使用单分子光谱学来探测人类端粒DNA的动力学。在钾溶液中观察到三种构象，一种是未折叠的，两种是折叠的，每种构象可以进一步分为长寿命和短寿命两种，根据寿命分别为分钟和秒。囊泡包裹研究表明，这里检测到的总共六种状态是DNA固有的。替换一个鸟嘌呤严重阻碍了折叠，只显示了短暂的物种。长寿命的折叠状态在生理相关的条件下占主导地位，可能对应于高分辨率结构研究中看到的平行和反平行的G-四链。尽管在这些条件下很少见，但短命物种决定了整体的动态，因为它们连接了不同的长寿物种。我们认为这些先前未观察到的瞬态态代表了形成稳定的G-四链体的早期和晚期中间产物。主要的压实作用发生在早期和晚期中间体之间，局部重排可能足以将晚期中间体锁定为稳定折叠的形式。人类端粒DNA的极其多样化的构象可能对识别富含G的序列的蛋白质和药物具有机械意义。
DNA with tandem repeats of guanines folds into G-quadruplexes made of a stack of G-quartets. In vitro, G-quadruplex formation inhibits telomere extension, and POT1 binding to the single-stranded telomeric DNA enhances telomerase activity by disrupting the G-quadruplex structure, highlighting the potential importance of the G-quadruplex structure in regulating telomere length in vivo. We have used single-molecule spectroscopy to probe the dynamics of human telomeric DNA. Three conformations were observed in potassium solution, one unfolded and two folded, and each conformation could be further divided into two species, long-lived and short-lived, based on lifetimes of minutes vs. seconds. Vesicle encapsulation studies suggest that the total of six states detected here is intrinsic to the DNA. Folding was severely hindered by replacing a single guanine, showing only the short-lived species. The long-lived folded states are dominant in physiologically relevant conditions and probably correspond to the parallel and antiparallel G-quadruplexes seen in high-resolution structural studies. Although rare under these conditions, the short-lived species determine the overall dynamics because they bridge the different long-lived species. We propose that these previously unobserved transient states represent the early and late intermediates toward the formation of stable G-quadruplexes. The major compaction occurs between the early and late intermediates, and it is possible that local rearrangements are sufficient in locking the late intermediates into the stably folded forms. The extremely diverse conformations of the human telomeric DNA may have mechanistic implications for the proteins and drugs that recognize G-rich sequences.