School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA.
Proc Natl Acad Sci U S A. 2012 Jan 17;109(3):799-804. doi: 10.1073/pnas.1119057109. Epub 2011 Dec 27.
Dynamic RNA molecules carry out essential processes in the cell including translation and splicing. Base-pair interactions stabilize RNA into relatively rigid structures, while flexible non-base-paired regions allow RNA to undergo conformational changes required for function. To advance our understanding of RNA folding and dynamics it is critical to know the flexibility of these un-base-paired regions and how it depends on counterions. Yet, information about nucleic acid polymer properties is mainly derived from studies of ssDNA. Here we measure the persistence lengths (l(p)) of ssRNA. We observe valence and ionic strength-dependent differences in l(p) in a direct comparison between 40-mers of deoxythymidylate (dT(40)) and uridylate (rU(40)) measured using the powerful combination of SAXS and smFRET. We also show that nucleic acid flexibility is influenced by local environment (an adjoining double helix). Our results illustrate the complex interplay between conformation and ion environment that modulates nucleic acid function in vivo.
动态 RNA 分子在细胞中执行包括翻译和剪接在内的基本过程。碱基对相互作用将 RNA 稳定成相对刚性的结构，而灵活的非碱基配对区域允许 RNA 发生构象变化以实现其功能。为了深入了解 RNA 的折叠和动态特性，了解这些非碱基配对区域的柔韧性以及其如何依赖于抗衡离子是至关重要的。然而，关于核酸聚合物性质的信息主要来自于对 ssDNA 的研究。在这里，我们测量了 ssRNA 的持续长度（l(p)）。我们通过使用 SAXS 和 smFRET 的强大组合，直接比较脱氧胸苷（dT(40)）和尿苷（rU(40)）的 40 个核苷酸，观察到 l(p) 与价数和离子强度有关的差异。我们还表明，核酸的柔韧性受到局部环境（相邻的双链）的影响。我们的结果说明了构象和离子环境之间复杂的相互作用，这种相互作用调节了体内核酸的功能。
