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Nat Struct Mol Biol. 2016 Sep;23(9):859-64. doi: 10.1038/nsmb.3280. Epub 2016 Aug 15.

An accurately preorganized IRES RNA structure enables eIF4G capture for initiation of viral translation.

Author information

1
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA.
2
Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York, USA.
3
Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, USA.

Abstract

Many viruses bypass canonical cap-dependent translation in host cells by using internal ribosomal entry sites (IRESs) in their transcripts; IRESs hijack initiation factors for the assembly of initiation complexes. However, it is currently unknown how IRES RNAs recognize initiation factors that have no endogenous RNA binding partners; in a prominent example, the IRES of encephalomyocarditis virus (EMCV) interacts with the HEAT-1 domain of eukaryotic initiation factor 4G (eIF4G). Here we report the solution structure of the J-K region of this IRES and show that its stems are precisely organized to position protein-recognition bulges. This multisite interaction mechanism operates on an all-or-nothing principle in which all domains are required. This preorganization is accomplished by an 'adjuster module': a pentaloop motif that acts as a dual-sided docking station for base-pair receptors. Because subtle changes in the orientation abrogate protein capture, our study highlights how a viral RNA acquires affinity for a target protein.

PMID:
27525590
PMCID:
PMC5061125
DOI:
10.1038/nsmb.3280
[Indexed for MEDLINE]
Free PMC Article

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