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Nature. 2015 Mar 5;519(7541):110-3. doi: 10.1038/nature14219. Epub 2015 Feb 4.

Initiation of translation in bacteria by a structured eukaryotic IRES RNA.

Author information

1
1] Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, USA [2] Howard Hughes Medical Institute, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, USA.
2
Center for Molecular Biology of RNA and Department of Molecular, Cell and Developmental Biology, Sinsheimer Labs, University of California at Santa Cruz, Santa Cruz, California 95064, USA.
3
Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, USA.

Abstract

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.

PMID:
25652826
PMCID:
PMC4352134
DOI:
10.1038/nature14219
[Indexed for MEDLINE]
Free PMC Article

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