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Nature:一个IRES掌管一切

摘要 : Jeffrey Kieft及同事想知道是否会有一种被真核生物和原核生物都能识别的普遍信号,他们现在介绍了具有这种性质的一个真核病毒IRES (内部核糖体进入点)元素。

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翻译对所有活生物的基因表达来说都至关重要,但用来招募核糖体和启动蛋白合成的信号在不同生命领域却截然不同。虽然真核生物和原核生物都通过一个高度保守的核心核糖体结构来翻译mRNA,但mRNA内被核糖体识别的两种信号是却相互排斥的。

Jeffrey Kieft及同事想知道是否会有一种被真核生物和原核生物都能识别的普遍信号,他们现在介绍了具有这种性质的一个真核病毒IRES (内部核糖体进入点)元素。该IRES与细菌和真核生物核糖体都能够相似地、以依赖于结构的方式结合,但在细菌中该元素的结合会诱导核糖体位置发生一个变化,这种变化在真核生物核糖体中没有被看到。

原文链接:Initiation of translation in bacteria by a structured eukaryotic IRES RNA

The central dogma of gene expression (DNA to RNA to protein) is universal, but in different domains of life there are fundamental mechanistic differences within this pathway. For example, the canonical molecular signals used to initiate protein synthesis in bacteria and eukaryotes are mutually exclusive. However, the core structures and conformational dynamics of ribosomes that are responsible for the translation steps that take place after initiation are ancient and conserved across the domains of life. We wanted to explore whether an undiscovered RNA-based signal might be able to use these conserved features, bypassing mechanisms specific to each domain of life, and initiate protein synthesis in both bacteria and eukaryotes. Although structured internal ribosome entry site (IRES) RNAs can manipulate ribosomes to initiate translation in eukaryotic cells, an analogous RNA structure-based mechanism has not been observed in bacteria. Here we report our discovery that a eukaryotic viral IRES can initiate translation in live bacteria. We solved the crystal structure of this IRES bound to a bacterial ribosome to 3.8 Å resolution, revealing that despite differences between bacterial and eukaryotic ribosomes this IRES binds directly to both and occupies the space normally used by transfer RNAs. Initiation in both bacteria and eukaryotes depends on the structure of the IRES RNA, but in bacteria this RNA uses a different mechanism that includes a form of ribosome repositioning after initial recruitment. This IRES RNA bridges billions of years of evolutionary divergence and provides an example of an RNA structure-based translation initiation signal capable of operating in two domains of life.

对应Nature杂志: 2015年3月5日Nature杂志精选

来源: Nature 浏览次数:101

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