An RNA polymerase ribozyme that has been the subject of extensive directed evolution efforts has attained the ability to synthesize complex functional RNAs, including a full-length copy of its own evolutionary ancestor. During the course of evolution, the catalytic core of the ribozyme has undergone a major structural rearrangement, resulting in a novel tertiary structural element that lies in close proximity to the active site. Through a combination of site-directed mutagenesis, structural probing, and deep sequencing analysis, the trajectory of evolution was seen to involve the progressive stabilization of the new structure, which provides the basis for improved catalytic activity of the ribozyme. Multiple paths to the new structure were explored by the evolving population, converging upon a common solution. Tertiary structural remodeling of RNA is known to occur in nature, as evidenced by the phylogenetic analysis of extant organisms, but this type of structural innovation had not previously been observed in an experimental setting. Despite prior speculation that the catalytic core of the ribozyme had become trapped in a narrow local fitness optimum, the evolving population has broken through to a new fitness locale, raising the possibility that further improvement of polymerase activity may be achievable.

中文翻译：

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见证 RNA 酶的结构进化

已成为广泛定向进化研究对象的 RNA 聚合酶核酶已获得合成复杂功能性 RNA 的能力，包括其自身进化祖先的全长拷贝。在进化过程中，核酶的催化核心发生了重大的结构重排，产生了一个新的三级结构元件，靠近活性位点。通过结合定点诱变、结构探测和深度测序分析，可以看出进化轨迹涉及新结构的逐步稳定，这为提高核酶的催化活性提供了基础。不断发展的人口探索了通往新结构的多条途径，并汇聚在一个共同的解决方案上。已知 RNA 的三级结构重塑发生在自然界中，现存生物的系统发育分析证明了这一点，但这种类型的结构创新以前没有在实验环境中观察到。尽管先前推测核酶的催化核心已陷入狭窄的局部适应性最佳状态，但不断发展的种群已突破到新的适应性区域，提高了聚合酶活性进一步提高的可能性。