State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry & Chemical Engineering, Nanjing University , Nanjing 210023, China.
Université de Bordeaux , INSERM U1212, CNRS UMR 5320, ARNA Laboratory, IECB, F-33600 Pessac, France.
J Am Chem Soc. 2017 Jun 14;139(23):7768-7779. doi: 10.1021/jacs.7b00648. Epub 2017 Jun 5.
To understand the role of ribose G-quartets and how they affect the properties of G-quadruplex structures, we studied three systems in which one, two, three, or four deoxyribose G-quartets were substituted with ribose G-quartets. These systems were a parallel DNA intramolecular G-quadruplex, d(TTGGGTGGGTTGGGTGGGTT), and two tetramolecular G-quadruplexes, d(TGGGT) and d(TGGGGT). Thermal denaturation experiments revealed that ribose G-quartets have position-dependent and cumulative effects on G-quadruplex stability. An unexpected destabilization was observed when rG quartets were presented at the 5'-end of the G stack. This observation challenges the general belief that RNA residues stabilize G-quadruplexes. Furthermore, in contrast to past proposals, hydration is not the main factor determining the stability of our RNA/DNA chimeric G-quadruplexes. Interestingly, the presence of rG residues in a central G-quartet facilitated the formation of additional tetramolecular G-quadruplex topologies showing positive circular dichroism signals at 295 nm. 2D NMR analysis of the tetramolecular TGgGGT (lowercase letter indicates ribose) indicates that Gs in the 5'-most G-quartet adopt the syn conformation. These analyses highlight several new aspects of the role of ribose G-quartets on G-quadruplex structure and stability, and demonstrate that the positions of ribose residues are critical for tuning G-quadruplex properties.
为了理解核糖 G-四联体的作用以及它们如何影响 G-四联体结构的性质，我们研究了三个系统，其中一个、两个、三个或四个脱氧核糖 G-四联体被核糖 G-四联体取代。这些系统是一个平行的 DNA 分子内 G-四联体，d(TTGGGTGGGTTGGGTGGGTT)，和两个四聚体 G-四联体，d(TGGGT)和 d(TGGGGT)。热变性实验表明，核糖 G-四联体对 G-四联体的稳定性具有位置依赖性和累积效应。当 rG 四联体出现在 G 堆积的 5'-端时，观察到出乎意料的不稳定。这一观察结果挑战了 RNA 残基稳定 G-四联体的普遍观点。此外，与过去的提议相反，水合作用不是决定我们的 RNA/DNA 嵌合 G-四联体稳定性的主要因素。有趣的是，rG 残基在中央 G-四联体中的存在促进了额外的四聚体 G-四联体拓扑结构的形成，在 295nm 处显示出正圆二色性信号。对四聚体 TGgGGT（小写字母表示核糖）的 2D NMR 分析表明，5'-最 G-四联体中的 Gs 采用顺式构象。这些分析突出了核糖 G-四联体在 G-四联体结构和稳定性中的几个新方面，并表明核糖残基的位置对于调节 G-四联体的性质至关重要。
