Stabilizing interactions and rational design of non-canonical G-quadruplexes

由于其可能的生物学作用，G-四链体（G4）作为药物干预的新靶点引起了相当大的兴趣。此外，G4也越来越多地被用作各种技术应用中的强大工具，例如，作为适体、传感器或电子开关。它们的高度多态性为它们的特异性识别和功能优化提供了极好的机会。然而，由于缺乏对驱动富G序列进入特定折叠的关键相互作用的理解，任意四链体拓扑结构的合理设计和基于序列的结构预测受到限制，特别是对于具有断裂G柱的非规范G4结构。在一个正在进行的项目的延续，竞争性折叠规范和非规范结构将通过优化的G-道干预序列，以选择定义的结构进行研究。重点将放在经常出现的非规范拓扑与V形或snapback循环。高分辨率NMR结构的测定结合量热衍生的热力学稳定性，预计将提供有价值的洞察关键的相互作用，能够执行和稳定相应的G4物种。用于引导折叠的有吸引力的工具包括四链体-双链体（Q-D）界面，其在结构重排后形成为靶G4。这里，Q-D连接处的特异性配体的结合，也用作基因组内的推定识别热点，可以另外改变平衡，因此用于诱导替代折叠。研究结果预计将促进结构预测和规范，特别是非规范的G4结构基序的合理设计。

Because of their possible biological role, G-quadruplexes (G4s) have attracted considerable interest as novel targets for pharmaceutical interventions. Additionally, G4s have also been increasingly employed as powerful tools in various technological applications, e.g., as aptamers, sensors, or electronic switches. Their highly polymorphous nature offers excellent opportunities for their specific recognition and functional optimization. However, due to poor understanding of critical interactions that drive a G-rich sequence into a particular fold, the rational design of arbitrary quadruplex topologies and sequencebased structural predictions are restricted, especially for noncanonical G4 structures featuring broken G-columns. In continuation of an ongoing project, competitive folding to canonical and noncanonical structures will be studied through the optimization of G-tract intervening sequences to select for defined structures. Emphasis will be placed on frequently occurring non-canonical topologies with Vshaped or snapback loops. The determination of high-resolution NMR structures combined with calorimetry-derived thermodynamic stabilities is expected to give valuable insight into critical interactions that are able to enforce and stabilize corresponding G4 species. An attractive tool for guiding a fold includes quadruplex-duplex (Q-D) interfaces when formed upon structural rearrangements to the target G4. Here, binding of specific ligands at the Q-D junction, also serving as putative recognition hotspots within the genome, may additionally shift equilibria and thus be employed for inducing alternative folds. Findings are expected to promote both structure predictions and the rational design of canonical and in particular non-canonical G4 structural motifs.