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Eukaryotic translation initiation machinery can operate in a bacterial-like mode without eIF2

Nature Structural & Molecular Biology volume 15, pages 836–841 (2008)Cite this article

Abstract

Unlike bacteria, a specialized eukaryotic initiation factor (eIF)-2, in the form of the ternary complex eIF2–GTP–Met-tRNAi Met, is used to deliver the initiator tRNA to the ribosome in all eukaryotic cells. Here we show that the hepatitis C virus (HCV) internal ribosome entry site (IRES) can direct translation without eIF2 and its GTPase-activating protein eIF5. In addition to the general eIF2- and eIF5-dependent pathway of 80S complex assembly, the HCV IRES makes use of a bacterial-like pathway requiring as initiation factors only eIF5B (an analog of bacterial IF2) and eIF3. The switch from the conventional eukaryotic mode of translation initiation to the eIF2-independent mechanism occurs when eIF2 is inactivated by phosphorylation under stress conditions.

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Figure 1: Assembly of translation initiation complexes on the HCV IRES and β-globin mRNAs and their analysis by sucrose density gradient centrifugation.
Figure 2: 80S complexes formed without eIF2 are competent for translational elongation.
Figure 3: eIF2 phosphorylation activates the alternative pathway for 80S formation on the HCV IRES in RRL.
Figure 4: HCV IRES–directed translation is relatively resistant to eIF2 inactivation in vivo.
Figure 5: Alternative pathways of the 80S initiation complex formation on the HCV IRES.

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Acknowledgements

We thank L.P. Ovchinnikov (Institute of Protein Research, Pushchino, Russia) for the kind gift of eEF2 and W.C. Merrick (Case Western Reserve University, Cleveland, USA) for anti-eIF2α antibodies. We appreciate the advice from P. Lukavsky on eIF5B expression. We are also grateful to G. Belsham, A. Hinnebusch and N. Sonenberg for critical reading of the manuscript and valuable suggestions. This work was supported by grants 07-04-01222 and 05-04-49704 from the Russian Foundation for Basic Research (RFBR) to I.M.T. and I.N.S., respectively.

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Author notes

  1. Ilya M Terenin and Sergey E Dmitriev: These authors contributed equally to this work.

Authors and Affiliations

  1. A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Building A, Moscow, 119992, Russia

    Ilya M Terenin, Sergey E Dmitriev, Dmitry E Andreev & Ivan N Shatsky

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  1. Ilya M Terenin
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Contributions

I.M.T. and S.E.D. contributed equally to this work. I.M.T. and D.E.A. performed in vitro experiments; S.E.D. carried out cell transfection studies; and I.N.S., S.E.D. and I.M.T. wrote the article. All authors discussed the results and commented on the manuscript.

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Correspondence to Ivan N Shatsky.

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Terenin, I., Dmitriev, S., Andreev, D. et al. Eukaryotic translation initiation machinery can operate in a bacterial-like mode without eIF2. Nat Struct Mol Biol 15, 836–841 (2008). https://doi.org/10.1038/nsmb.1445

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