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The joining of ribosomal subunits in eukaryotes requires eIF5B

Nature volume 403, pages 332–335 (2000)Cite this article

Abstract

Initiation of eukaryotic protein synthesis begins with the ribosome separated into its 40S and 60S subunits1. The 40S subunit first binds eukaryotic initiation factor (eIF) 3 and an eIF2–GTP–initiator transfer RNA ternary complex. The resulting complex requires eIF1, eIF1A, eIF4A, eIF4B and eIF4F to bind to a messenger RNA and to scan to the initiation codon2. eIF5 stimulates hydrolysis of eIF2-bound GTP and eIF2 is released from the 48S complex formed at the initiation codon before it is joined by a 60S subunit to form an active 80S ribosome3,4,5,6,7,8. Here we show that hydrolysis of eIF2-bound GTP induced by eIF5 in 48S complexes is necessary but not sufficient for the subunits to join. A second factor termed eIF5B (relative molecular mass 175,000) is essential for this process. It is a homologue of the prokaryotic initiation factor IF2 (refs 6, 7) and, like it8,9,10,11,12, mediates joining of subunits and has a ribosome-dependent GTPase activity that is essential for its function.

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Figure 1: Formation of 80S complexes on β-globin mRNA requires eIF5 and eIF5B.
Figure 2: Dependence of the activities of eIF5 and eIF5B on the presence of eIF1 and eIF3.
Figure 3: GTP binding and hydrolysis by eIF5B.
Figure 4: Catalytic activity of eIF5B.
Figure 5: Hydrolysis of GTP bound to cIF5B is required for release of eIF5B from ribosomes.

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Acknowledgements

We thank W. Merrick for discussions, D. Etchison and R. Schneider for antibodies, and L. Siconolfi-Baez for sequencing eIF5B. These studies were supported by grants from the NIH to C.U.T.H. and T.V.P.

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Authors and Affiliations

  1. Department of Microbiology and Immunology State University of New York Health Science Center at Brooklyn, 450 Clarkson Avenue, Brooklyn, 11203, New York, USA

    Tatyana V. Pestova, Ivan B. Lomakin & Christopher U. T. Hellen

  2. A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, 119899, Russia

    Tatyana V. Pestova

  3. Laboratory of Eukaryotic Gene Regulation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, 20892-2716, Maryland, USA

    Joon H. Lee, Sang Ki Choi & Thomas E. Dever

Authors
  1. Tatyana V. Pestova
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  6. Christopher U. T. Hellen
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Correspondence to Tatyana V. Pestova.

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Pestova, T., Lomakin, I., Lee, J. et al. The joining of ribosomal subunits in eukaryotes requires eIF5B. Nature 403, 332–335 (2000). https://doi.org/10.1038/35002118

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