NMR structural study on the self-trimerization of d(GTTAGG) into a dynamic trimolecular G-quadruplex assembly preferentially in Na+ solution with a moderate K+ tolerance.
NMR structural study on the self-trimerization of d(GTTAGG) into a dynamic trimolecular G-quadruplex assembly preferentially in Na+ solution with a moderate K+ tolerance.
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d(GTTAGG) 在具有中等 K 耐受性的 Na 溶液中优先自三聚成动态三分子 G-四链体组装的 NMR 结构研究
DOI：
10.1093/nar/gkab028
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发表时间：
2021-02-26
影响因子：
14.9
通讯作者：
Zhang N
中科院分区：
文献类型：
--
作者：
Jing H;Fu W;Hu W;Xu S;Xu X;He M;Liu Y;Zhang N
巨大的G-四链体（GQ）主要由一个，两个或四个富含G的寡聚体折叠，很少有例外。在这里，我们提出了第一个NMR溶液结构的三分子GQ（三GQ），这是唯一的组装通过自三聚的d（GTTAGG），优先在Na+溶液耐受等量的K+阳离子。八个鸟嘌呤从三个不对称折叠链的d（GTTAGG）被组织成一个两个四分体核心，其特征是一个破碎的G柱和两个宽度不规则的凹槽。在17°C下，在折叠的tri-GQ和未折叠的单链d（GTTAGG）之间自发地发生秒级的快速链交换，两种物质在动态平衡中共存。因此，这个tri-GQ不仅仅是一个静态的组件，而是一个动态的组件。此外，另一个次要的tetra-GQ，具有puronically四聚体（2+2）的反平行拓扑结构变得明显，只有在一个非常高的链浓度超过18 mM。主要的三-GQ和次要的tetra-GQ被认为是相互关联的，并提出了相应的可逆相互转化途径。序列d（GTTAGG）既可以看作是人端粒DNA的一个阅读码移码单重复序列，也可以看作是家蚕端粒DNA的一个1.5重复序列。总的来说，我们的研究结果提供了新的见解GQ，并期待更多的功能应用。
Vast G-quadruplexes (GQs) are primarily folded by one, two, or four G-rich oligomers, rarely with an exception. Here, we present the first NMR solution structure of a trimolecular GQ (tri-GQ) that is solely assembled by the self-trimerization of d(GTTAGG), preferentially in Na+ solution tolerant to an equal amount of K+ cation. Eight guanines from three asymmetrically folded strands of d(GTTAGG) are organized into a two-tetrad core, which features a broken G-column and two width-irregular grooves. Fast strand exchanges on a timescale of second at 17°C spontaneously occur between folded tri-GQ and unfolded single-strand of d(GTTAGG) that both species coexist in dynamic equilibrium. Thus, this tri-GQ is not just simply a static assembly but rather a dynamic assembly. Moreover, another minor tetra-GQ that has putatively tetrameric (2+2) antiparallel topology becomes noticeable only at an extremely high strand concentration above 18 mM. The major tri-GQ and minor tetra-GQ are considered to be mutually related, and their reversible interconversion pathways are proposed accordingly. The sequence d(GTTAGG) could be regarded as either a reading frame shifted single repeat of human telomeric DNA or a 1.5 repeat of Bombyx mori telomeric DNA. Overall, our findings provide new insight into GQs and expect more functional applications.
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