Thermal stabilisation of RNA·RNA duplexes and G-quadruplexes by phosphorothiolate linkages
作者:Michael M. Piperakis、James W. Gaynor、Julie Fisher、Richard Cosstick
DOI:10.1039/c2ob26940f
日期:——
The effect of 3′-S-phosphorothiolate linkages on the stability of RNA·RNA duplexes and G-quadruplex structures has been studied. 3′-Thio-2′-deoxyuridine was incorporated into RNA duplexes and thermal melting studies revealed that the resulting 3′-S-phosphorothiolate linkages increased the stability of the duplex to thermal denaturation. Additionally, and contrary to expectation, a similar effect on duplex stability was observed when the same thionucleoside was incorporated into the RNA strand of a RNA·DNA duplex. A suitably protected derivative of 3′-thio-2′-deoxyguanosine was prepared using an oxidation–reduction strategy and this residue also increased the thermal stability the [d(TGGGGT)]4 G-quadruplex when positioned centrally. The results are discussed in terms of the influence that the sulfur atom has on the conformation of the furanose ring and imply that the previously noted high thermal stability of parallel RNA quadruplexes is not derived from H-bonding interactions of the 2′-hydroxyl group, but can be attributed to conformational effects.
关于3′-S-磷硫键对RNA·RNA双链体和G-四链体结构稳定性的影响已有研究。在RNA双链体中加入了3′-巯基-2′-脱氧尿苷,热熔解研究表明,形成的3′-S-磷硫键增强了双链体对热变性的稳定性。此外,与预期相反,当同样的硫代核苷酸被引入RNA·DNA双链体的RNA链时,也观察到类似的增强双链体稳定性的效应。通过氧化还原策略制备了适当保护的3′-巯基-2′-脱氧鸟苷衍生物,并且发现该残基位于中间位置时也能提高[d(TGGGGT)]4 G-四链体的热稳定性。研究结果就硫原子对呋喃糖环构象的影响进行了讨论,并暗示,先前注意到的高温下平行RNA四链体的稳定性并非源自2′-羟基的氢键相互作用,而可能是源自构象效应。