Intramolecular phenotypic capacitance in a modular RNA molecule
Intramolecular phenotypic capacitance in a modular RNA molecule
复制标题
DOI：
10.1073/pnas.1420902112
复制
发表时间：
2015-10-06
影响因子：
11.1
通讯作者：
Wagner, Andreas
中科院分区：
文献类型：
--
作者：
Hayden, Eric J.;Bendixsen, Devin P.;Wagner, Andreas
表型电容是指基因组积累突变的能力，这些突变是有条件隐藏的，只有在某些环境或遗传变化后才能显示表型改变效应。电容对新形式和功能的进化具有重要意义，但电容背后的实验研究机制大多限于复杂的多组分系统，通常涉及几个相互作用的蛋白质分子。在这里，我们展示了一个更简单的系统，一个单独的RNA分子的催化活性（核酶）内的表型电容。这种天然存在的RNA分子具有模块化结构，其中支架模块充当分子内伴侣，其促进第二催化模块的折叠。先前的研究表明，支架模块不是活性所绝对需要的，但显著降低了活性位点形成所需的镁离子浓度。在这里，我们使用镁离子浓度的实验扰动，破坏这种核酶的某些遗传变体的折叠，并使用体外选择，然后进行深度测序，以确定具有改变的表型（催化活性）的基因型。我们确定了多个条件突变，改变野生型核酶表型下的压力环境条件下的低镁离子浓度，但在更宽松的条件下保持表型。这种有条件的缓冲被限制在支架模块，但控制催化表型，展示了模块化如何能够在单个大分子内实现表型电容。RNA在生命中的古老作用表明，自生命起源以来，表型电容可能影响了进化。
Phenotypic capacitance refers to the ability of a genome to accumulate mutations that are conditionally hidden and only reveal phenotype-altering effects after certain environmental or genetic changes. Capacitance has important implications for the evolution of novel forms and functions, but experimentally studied mechanisms behind capacitance are mostly limited to complex, multicomponent systems often involving several interacting protein molecules. Here we demonstrate phenotypic capacitance within a much simpler system, an individual RNA molecule with catalytic activity (ribozyme). This naturally occurring RNA molecule has a modular structure, where a scaffold module acts as an intramolecular chaperone that facilitates folding of a second catalytic module. Previous studies have shown that the scaffold module is not absolutely required for activity, but dramatically decreases the concentration of magnesium ions required for the formation of an active site. Here, we use an experimental perturbation of magnesium ion concentration that disrupts the folding of certain genetic variants of this ribozyme and use in vitro selection followed by deep sequencing to identify genotypes with altered phenotypes (catalytic activity). We identify multiple conditional mutations that alter the wild-type ribozyme phenotype under a stressful environmental condition of low magnesium ion concentration, but preserve the phenotype under more relaxed conditions. This conditional buffering is confined to the scaffold module, but controls the catalytic phenotype, demonstrating how modularity can enable phenotypic capacitance within a single macromolecule. RNA's ancient role in life suggests that phenotypic capacitance may have influenced evolution since life's origins.