Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204, USA.
RNA. 2022 Mar;28(3):340-352. doi: 10.1261/rna.079006.121. Epub 2021 Dec 7.
The ribosome is the molecular factory that catalyzes all coded protein synthesis in extant organisms. Eukaryotic ribosomes are typically assembled out of four rRNAs; namely, 5S, 5.8S, 18S, and 28S. However, the 28S rRNA of some trypanosomatid organisms has been found to be segmented into six independent rRNAs of different sizes. The two largest segments have multiple sites where they jointly form stems comprised of standard base pairs that can hold them together. However, such regions of interaction are not observed among the four smaller RNAs. Early reports suggested that trypanosomatid segmented ribosome assembly was essentially achieved thanks to their association with rProteins. However, examination of cryo-EM ribosomal structures from , , and reveals several long-range nonstandard RNA/RNA interactions. Most of these interactions are clusters of individual hydrogen bonds and so are not readily predictable. However, taken as a whole, they represent significant stabilizing energy that likely facilitates rRNA assembly and the overall stability of the segmented ribosomes. In the context of origin of life studies, the current results provide a better understanding of the true nature of RNA sequence space and what might be possible without an RNA replicase.
核糖体是催化现存生物所有编码蛋白合成的分子工厂。真核核糖体通常由四个 rRNA 组装而成：5S、5.8S、18S 和 28S。然而，一些鞭毛原生动物生物的 28S rRNA 已被发现被分割成六个不同大小的独立 rRNA。两个最大的片段有多个位点，它们共同形成由标准碱基对组成的茎，这些茎可以将它们固定在一起。然而，在四个较小的 RNA 之间没有观察到这种相互作用的区域。早期的报告表明，鞭毛原生动物分段核糖体的组装基本上是由于它们与 r 蛋白的结合而实现的。然而，对 、 和 的 cryo-EM 核糖体结构的检查揭示了几个长程非标准 RNA/RNA 相互作用。这些相互作用中的大多数是单个氢键的簇，因此不容易预测。然而，总体而言，它们代表了显著的稳定能量，可能有助于 rRNA 的组装和分段核糖体的整体稳定性。在生命起源研究的背景下，目前的结果提供了对 RNA 序列空间的真实性质以及在没有 RNA 复制酶的情况下可能实现的功能的更好理解。
