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RNA Structural Modules Control the Rate and Pathway of RNA Folding and Assembly

机译：RNA结构模块控制RNA折叠和组装的速率和途径

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Structured RNAs fold through multiple pathways, but we have little understanding of the molecular features that dictate folding pathways and determine rates along a given pathway. Here, we asked whether folding of a complex RNA can be understood from its structural modules. In a two-piece version of the Tetrahymena group I ribozyme, the separated P5abc subdomain folds to local native secondary and tertiary structure in a linked transition and assembles with the ribozyme core via three tertiary contacts: a kissing loop (P14), a metal core-receptor interaction, and a tetraloop-receptor interaction, the first two of which are expected to depend on native P5abc structure from the local transition. Native gel, NMR, and chemical footprinting experiments showed that mutations that destabilize the native P5abc structure slowed assembly up to 100-fold, indicating that P5abc folds first and then assembles with the core by conformational selection. However, rate decreases beyond 100-fold were not observed because an alternative pathway becomes dominant, with nonnative P5abc binding the core and then undergoing an induced-fit rearrangement. P14 is formed in the rate-limiting step along the conformational selection pathway but after the rate-limiting step along the induced-fit pathway. Strikingly, the assembly rate along the conformational selection pathway resembles that of an isolated kissing loop similar to P14, and the rate along the induced-fit pathway resembles that of an isolated tetraloop-receptor interaction. Our results indicate substantial modularity in RNA folding and assembly and suggest that these processes can be understood in terms of underlying structural modules. (C) 2016 Elsevier Ltd. All rights reserved.
机译：结构化的RNA可以通过多种途径折叠，但我们对决定折叠途径并确定给定途径速率的分子特征了解甚少。在这里，我们问是否可以从其结构模块中了解复杂RNA的折叠。在四膜虫群I核酶的两件式版本中，分离的P5abc子域以链接的过渡折叠成局部天然的二级和三级结构，并通过三个三级接触与核酶核心组装：接吻环（P14），金属核-受体相互作用和四环-受体相互作用，预计前两个依赖于局部转变的天然P5abc结构。天然凝胶，NMR和化学足迹实验表明，破坏天然P5abc结构稳定性的突变使组装速度降低了100倍，这表明P5abc首先折叠，然后通过构象选择与核心组装。然而，未观察到速率降低超过100倍，因为替代途径占优势，非天然P5abc结合核心，然后进行诱导拟合重排。 P14在构象选择途径的限速步骤中但在诱导诱导途径的限速步骤之后形成。令人惊讶的是，沿着构象选择途径的装配速率类似于类似于P14的孤立的接吻环的装配速率，并且沿着诱导的拟合通道的装配速率类似于孤立的四环-受体相互作用的装配速率。我们的结果表明在RNA折叠和组装中具有实质性的模块化，并暗示可以根据基础结构模块来理解这些过程。 （C）2016 Elsevier Ltd.保留所有权利。

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