College of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China.
Key Laboratory of Ecology and Environment in Minority Areas (Minzu University of China), National Ethnic Affairs Commission, Beijing 100081, China.
Molecules. 2023 Jun 9;28(12):4671. doi: 10.3390/molecules28124671.
The G-quadruplex (GQ)-forming hexanucleotide repeat expansion (HRE) in the (C9) gene has been found to be the most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) (collectively, C9ALS/FTD), implying the great significance of modulating C9-HRE GQ structures in C9ALS/FTD therapeutic treatment strategies. In this study, we investigated the GQ structures formed by varied lengths of C9-HRE DNA sequences d(GGGGCC) (C9-24mer) and d(GGGGCC) (C9-48mer), and found that the C9-24mer forms anti-parallel GQ (AP-GQ) in the presence of potassium ions, while the long C9-48mer bearing eight guanine tracts forms unstacked tandem GQ consisting of two C9-24mer unimolecular AP-GQs. Moreover, the natural small molecule Fangchinoline was screened out in order to be able to stabilize and alter the C9-HRE DNA to parallel GQ topology. Further study of the interaction of Fangchinoline with the C9-HRE RNA GQ unit r(GGGGCC) (C9-RNA) revealed that it can also recognize and improve the thermal stability of C9-HRE RNA GQ. Finally, use of AutoDock simulation results indicated that Fangchinoline binds to the groove regions of the parallel C9-HRE GQs. These findings pave the way for further studies of GQ structures formed by pathologically related long C9-HRE sequences, and also provide a natural small-molecule ligand that modulates the structure and stability of C9-HRE GQ, both in DNA and RNA levels. Altogether, this work may contribute to therapeutic approaches of C9ALS/FTD which take the upstream C9-HRE DNA region, as well as the toxic C9-HRE RNA, as targets.
（C9）基因中的 G-四链体（GQ）形成六核苷酸重复扩展（HRE）已被发现是肌萎缩侧索硬化症（ALS）和额颞叶痴呆（FTD）（统称 C9ALS/FTD）的最常见原因，这意味着调节 C9-HRE GQ 结构在 C9ALS/FTD 治疗策略中具有重要意义。在这项研究中，我们研究了不同长度的 C9-HRE DNA 序列 d(GGGGCC)（C9-24mer）和 d(GGGGCC)（C9-48mer）形成的 GQ 结构，发现 C9-24mer 在钾离子存在下形成反平行 GQ（AP-GQ），而长的 C9-48mer 带有八个鸟嘌呤链形成未堆叠的串联 GQ，由两个 C9-24mer 单分子 AP-GQ 组成。此外，筛选出天然小分子汉防己甲素，以能够稳定和改变 C9-HRE DNA 为平行 GQ 拓扑结构。进一步研究汉防己甲素与 C9-HRE RNA GQ 单元 r(GGGGCC)（C9-RNA）的相互作用表明，它还可以识别并提高 C9-HRE RNA GQ 的热稳定性。最后，使用 AutoDock 模拟结果表明，汉防己甲素结合到平行 C9-HRE GQ 的沟区。这些发现为进一步研究与病理相关的长 C9-HRE 序列形成的 GQ 结构铺平了道路，并提供了一种天然的小分子配体，可调节 C9-HRE GQ 在 DNA 和 RNA 水平上的结构和稳定性。总之，这项工作可能有助于以 C9-HRE DNA 上游区域以及毒性 C9-HRE RNA 为靶点的 C9ALS/FTD 治疗方法。
