The Saccharomyces cerevisiae translation initiation factor Tif3 and its mammalian homologue, eIF-4B, have RNA annealing activity.

Altmann, Michael; Wittmer, B.; Méthot, Nathalie; Sonenberg, Nahum; Trachsel, Hans

doi:10.1002/j.1460-2075.1995.tb00051.x

Cited by 96 publications

(85 citation statements)

References 38 publications

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“…The absence of yeIF4B in a tif3Δ mutant extract confers cold-sensitive translation in a manner rescued by mammalian eIF4B, indicating that the yeast and mammalian proteins share a conserved critical function. Surprisingly, however, yeIF4B does not stimulate the helicase activity of eIF4A in vitro (Altmann et al 1995;Rajagopal et al 2012), and consistent with this, the C-terminal domain (CTD) (Fig. 1A,B) of yeIF4B shows no obvious similarity to that of mammalian eIF4B (Altmann et al 1993;Coppolecchia et al 1993).…”

Section: Introductionsupporting

confidence: 60%

Yeast eIF4B binds to the head of the 40S ribosomal subunit and promotes mRNA recruitment through its N-terminal and internal repeat domains

Walker

Zhou

Mitchell

et al. 2012

RNA

154

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Eukaryotic translation initiation factor (eIF)4B stimulates recruitment of mRNA to the 43S ribosomal pre-initiation complex (PIC). Yeast eIF4B (yeIF4B), shown previously to bind single-stranded (ss) RNA, consists of an N-terminal domain (NTD), predicted to be unstructured in solution; an RNA-recognition motif (RRM); an unusual domain comprised of seven imperfect repeats of 26 amino acids; and a C-terminal domain. Although the mechanism of yeIF4B action has remained obscure, most models have suggested central roles for its RRM and ssRNA-binding activity. We have dissected the functions of yeIF4B's domains and show that the RRM and its ssRNA-binding activity are dispensable in vitro and in vivo. Instead, our data indicate that the 7-repeats and NTD are the most critical domains, which mediate binding of yeIF4B to the head of the 40S ribosomal subunit via interaction with Rps20. This interaction induces structural changes in the ribosome's mRNA entry channel that could facilitate mRNA loading. We also show that yeIF4B strongly promotes productive interaction of eIF4A with the 43S•mRNA PIC in a manner required for efficient mRNA recruitment.

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Section: Introductionsupporting

confidence: 60%

Yeast eIF4B binds to the head of the 40S ribosomal subunit and promotes mRNA recruitment through its N-terminal and internal repeat domains

Walker

Zhou

Mitchell

et al. 2012

RNA

154

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“…The significance of the 3'-5' RNA duplex unwinding activity of eIF4F, demonstrated in vitro with uncapped RNA substrates [66], needs to be elucidated; possible functions could be in internal initiation or in transient melting of structures in exposed regions of rRNA involved in ribosome-mRNA interactions during initiation. For eIF4B, long regarded on the basis of in vitro assays as a mere facilitator of eIF4A-catalysed RNA unwinding, a whole new area of interest is opened up by a recent paper demonstrating duplex annealing activity of this factor [351]. It should be remembered, however, that a great deal of the experimental evidence currently available on the function of the individual initiation factors, particularly those of the eIF4 group, is derived from in vitro assays performed in the absence of other components, such as ribosomal subunits and eIF3, with which they would be associated in the intact cell ; caution is therefore needed in extrapolating these data to the situation in vivo.…”

Section: Functions and Molecular Interactions Involving Initiation Famentioning

confidence: 99%

Initiation of Protein Synthesis in Eukaryotic Cells

Pain

1996

European Journal of Biochemistry

676

471

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It is becoming increasingly apparent that translational control plays an important role in the regulation of gene expression in eukaryotic cells. Most of the known physiological effects on translation are exerted at the level of polypeptide chain initiation. Research on initiation of translation over the past five years has yielded much new information, which can be divided into three main areas: (a) structure and function of initiation factors (including identification by sequencing studies of consensus domains and motifs) and investigation of protein-protein and protein-RNA interactions during initiation ; (b) physiological regulation of initiation factor activities and (c) identification of features in the 5' and 3' untranslated regions of messenger RNA molecules that regulate the selection of these mRNAs for translation. This review aims to assess recent progress in these three areas and to explore their interrelationships.Keywords: translation; initiation; mRNA ; review, regulation.In 1986 I published a review describing the mechanism and regulation of initiation of translation in mammalian cells 121. By that time most of the polypeptide initiation factors catalysing this process had been extensively purified and their individual activities studied in various in vitro systems. Several of them had been shown to be phosphoproteins and, in one case, eukaryotic initiation factor-2 (eIF-2), the effects of phosphorylation had been elucidated and two physiological kinases had been identified. There seemed to be a feeling in some circles that the most interesting problems in protein synthesis had been solved, and that only a few rather boring nuts and bolts awaited discovery.Over the intervening ten years there has been an explosion of research activity in this area, largely fuelled by information yielded by molecular biology and genetic techniques. Cloning of cDNAs encoding initiation factors has revealed domain structures indicative of function and potential regulatory mechanisms. Experiments exploiting the ability to elucidate and manipulate mRNA sequences have demonstrated that translational control contributes to changes in patterns of gene expression during growth, differentiation and development to an extent that would have seemed inconceivable in 1985. Such experiments have, in particular, revealed important roles for structural fea- UTR, untranslated region (in mRNA); RRM, RNA recognition motif; ORF, open reading frame; EMCV, encephalomyocarditis virus ; FMDV, foot-and-mouth disease virus ; IRES, internal ribosome entry segment ; PTB, polypyrimidine tract binding protein ; HCR, heme-controlled repressor; PKR, protein kinase activated by RNA; dsRNA, doublestranded RNA; p70ShK and p 9 0 k , 70 kDa and 90-92 kDa ribosomal protein S6 kinases ; GSK, glycogen synthase kinase ; IRE, iron-regulatory element; IRP, iron regulatory protein ; PABP, poly(A) binding protein; AMV, alfalfa mosaic virus ; CPE, cytoplasmic polyadenylation element (also known as ACE, adenylation control element); MAP, mitogenactivated protei...

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“…Surprisingly, the yeast TIF3 gene is not essential for growth despite the fact that no obvious duplicated gene exists. So far, attempts to stimulate eIF4 helicase activity by the yeast eIF4B failed (Altmann et al, 1995). Thus, the precise function of eIF4B in translation initiation and the difference in helicase stimulation between the yeast and mammalian proteins remain a mystery.…”

Section: Eif4a Is a Rna Helicase In Vitromentioning

confidence: 99%

Yeast RNA helicases of the DEAD‐box family involved in translation initiation

Linder¹

2003

Biology of the Cell

100

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RNA helicases of the DEAD-box and related families have been found to be required for all processes involving RNA molecules. Biochemical and genetic analyses have shown that at least two RNA helicases are required for translation initiation in yeast. Although it is generally believed that these enzymes are necessary to unwind secondary structures in the 5' untranslated region of mRNAs, their exact role has not been convincingly shown. We discuss here our present knowledge of the function of eIF4A and Ded1p, two DEAD-box proteins required for translation in eukaryotic cells.

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The Saccharomyces cerevisiae translation initiation factor Tif3 and its mammalian homologue, eIF-4B, have RNA annealing activity.

Cited by 96 publications

References 38 publications

Yeast eIF4B binds to the head of the 40S ribosomal subunit and promotes mRNA recruitment through its N-terminal and internal repeat domains

Yeast eIF4B binds to the head of the 40S ribosomal subunit and promotes mRNA recruitment through its N-terminal and internal repeat domains

Initiation of Protein Synthesis in Eukaryotic Cells

Yeast RNA helicases of the DEAD‐box family involved in translation initiation

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