Free Poly(A) Stimulates Capped mRNA Translation in Vitro through the eIF4G-Poly(A)-binding Protein Interaction

Borman, Andrew M.; Michel, Yanne; Malnou, Cécile E.; Kean, Katherine M.

doi:10.1074/jbc.m205065200

Cited by 43 publications

(25 citation statements)

References 28 publications

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“…This trans stimulation exhibits the same properties as previously described: PABP-eIF4GI interaction, synergistic activity of the cap and exogenous poly(A) tail and increased association of eIF4F-PABP complex to the cap (Borman et al, 2002). In plants, association of PABP with eIF4F was shown to increase the affinity of eIF4F for the cap structure by about 40-fold (Wei et al, 1998) with the PABP-eIF4F complex showing a tighter affinity for poly(A) than free PABP (Le et al, 1997).…”

Section: Physiological Relevance Of the Eif4g-pabp Interactionsupporting

confidence: 76%

Conducting the initiation of protein synthesis: the role of eIF4G

Prévot

Darlix

Ohlmann

2003

Biology of the Cell

197

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The eukaryotic initiation factor eIF4G is a large modular protein which serves as a docking site for initiation factors and proteins involved in RNA translation. Together with eIF4E and eIF4A, eIF4G constitutes the eIF4F complex which is a key component in promoting ribosome binding to the mRNA. Thus, the central role of eIF4G in initiation makes it a valid target for events aimed at modulating translation. Such events occur during viral infection by picornaviruses and lentiviruses and result in the hijack of the translational machinery through cleavage of eIF4G. Proteolysis of eIF4G is also mediated by caspases during the onset of apoptosis causing inhibition of protein synthesis. We will review the role of eIF4G and protein partners as well as the cellular and viral events that modulate eIF4G activity in the initiation of translation.

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Section: Physiological Relevance Of the Eif4g-pabp Interactionsupporting

confidence: 76%

Conducting the initiation of protein synthesis: the role of eIF4G

Prévot

Darlix

Ohlmann

2003

Biology of the Cell

197

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“…Here, both 100 and 200 ng of poly(rA) stimulated the translation of capped A0 control and PLE-containing luciferase mRNA two-to threefold. This trans stimulation of A0 mRNA translation by poly(rA) was observed previously in ribosome-depleted rabbit reticulocyte lysate (Borman et al 2002), and it disappeared at poly(A) lengths !54 nt for both control and PLE- Table 1 were transfected together with Renilla luciferase mRNA into LM(tkÀ) cells. Extracts prepared 1 h after transfection were analyzed for luciferase activity as in Figure 4, with the results for capped A0 control mRNA arbitrarily set to 1.…”

Section: Impact Of Inhibiting Pabp On the Translation Of Ple-containimentioning

confidence: 61%

mRNA with a <20-nt poly(A) tail imparted by the poly(A)-limiting element is translated as efficiently in vivo as long poly(A) mRNA

Peng

Schoenberg²

2005

RNA

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The poly(A)-limiting element (PLE) is a conserved sequence that restricts the length of the poly(A) tail to <20 nt. This study compared the translation of PLE-containing short poly(A) mRNA expressed in cells with translation in vitro of mRNAs with varying length poly(A) tails. In transfected cells, PLE-containing mRNA had a <20-nt poly(A) and accumulated to a level 20% higher than a matching control without a PLE. It was translated as well as the matching control mRNA with long poly(A) and showed equivalent binding to polysomes. Translation in a HeLa cell cytoplasmic extract was used to examine the impact of the PLE in the context of varying length poly(A) tails. Here the overall translation of +PLE mRNA was less than control mRNA with the same length poly(A), and the PLE did not overcome the effect of a short poly(A) tail. Because poly(A)-binding protein (PABP) is a dominant effector of poly(A)-dependent translation we reasoned excess PABP in our extract might overwhelm PLE regulation of translation. This was confirmed by experiments where PABP was inactivated with poly(rA) or Paip2, and the effect of both treatments was reversed by addition of recombinant PABP. These data indicate that the PLE functionally substitutes for bound PABP to stimulate translation of short poly(A) mRNA.

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“…One possibility that could explain such an observation is that the eviction of PABP from eIF4G by NSP3 abolishes the competition between polyadenylated and nonpolyadenylated RNA and renders all RNAs equally competent for translation regardless of their 3= ends. A similar phenomenon was observed when short poly(A) RNAs were added to an in vitro translation assay using ribosome-depleted RRL (36) or when nonpolyadenylated mRNA degradation was abolished in yeast (37). However, our data showing that NSP3 promotes the eIF4E-eIF4G interaction provides a more direct explanation for this unexpected observation and actually suggests that through its interaction with eIF4G, NSP3, independently of its binding to any 3= end, can substitute for the PABP-poly(A) complex in facilitating the initiation of capped mRNA translation.…”

Section: Discussionmentioning

confidence: 86%

Rotavirus NSP3 Is a Translational Surrogate of the Poly(A) Binding Protein-Poly(A) Complex

Gratia

Sarot

Vende

et al. 2015

J Virol

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Through its interaction with the 5= translation initiation factor eIF4G, poly(A) binding protein (PABP) facilitates the translation of 5=-capped and 3=-poly(A)-tailed mRNAs. Rotavirus mRNAs are capped but not polyadenylated, instead terminating in a 3= GACC motif that is recognized by the viral protein NSP3, which competes with PABP for eIF4G binding. Upon rotavirus infection, viral, GACC-tailed mRNAs are efficiently translated, while host poly(A)-tailed mRNA translation is, in contrast, severely impaired. To explore the roles of NSP3 in these two opposing events, the translational capabilities of three capped mRNAs, distinguished by either a GACC, a poly(A), or a non-GACC and nonpoly(A) 3= end, have been monitored after electroporation of cells expressing all rotavirus proteins (infected cells) or only NSP3 (stably or transiently transfected cells). In infected cells, we found that the magnitudes of translation induction (GACC-tailed mRNA) and translation reduction [poly(A)-tailed mRNA] both depended on the rotavirus strain used but that translation reduction not genetically linked to NSP3. In transfected cells, even a small amount of NSP3 was sufficient to dramatically enhance GACC-tailed mRNA translation and, surprisingly, to slightly favor the translation of both poly(A)-and nonpoly(A)-tailed mRNAs, likely by stabilizing the eIF4E-eIF4G interaction. These data suggest that NSP3 is a translational surrogate of the PABP-poly(A) complex; therefore, it cannot by itself be responsible for inhibiting the translation of host poly(A)-tailed mRNAs upon rotavirus infection. IMPORTANCETo control host cell physiology and to circumvent innate immunity, many viruses have evolved powerful mechanisms aimed at inhibiting host mRNA translation while stimulating translation of their own mRNAs. How rotavirus tackles this challenge is still a matter of debate. Using rotavirus-infected cells, we show that the magnitude of cellular poly(A) mRNA translation differs with respect to rotavirus strains but is not genetically linked to NSP3. Using cells expressing rotavirus NSP3, we show that NSP3 alone not only dramatically enhances rotavirus-like mRNA translation but also enhances poly(A) mRNA translation rather than inhibiting it, likely by stabilizing the eIF4E-eIF4G complex. Thus, the inhibition of cellular polyadenylated mRNA translation during rotavirus infection cannot be attributed solely to NSP3 and is more likely the result of global competition between viral and host mRNAs for the cellular translation machinery. W hen delivered into or synthesized by the host cell, viral mRNAs compete with cellular mRNAs already present in the cytoplasm for access to the protein synthesis machinery. Recruitment of the 40S ribosomal subunit onto mRNA (translation initiation) is the rate-limiting and most controlled step of eukaryotic protein biosynthesis; hence, it is highly competitive for both cellular and viral mRNAs. The 5= cap and 3= poly(A) tail of most cellular mRNAs are joined by a protein complex containing the cap binding pr...

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Free Poly(A) Stimulates Capped mRNA Translation in Vitro through the eIF4G-Poly(A)-binding Protein Interaction

Cited by 43 publications

References 28 publications

Conducting the initiation of protein synthesis: the role of eIF4G

Conducting the initiation of protein synthesis: the role of eIF4G

mRNA with a <20-nt poly(A) tail imparted by the poly(A)-limiting element is translated as efficiently in vivo as long poly(A) mRNA

Rotavirus NSP3 Is a Translational Surrogate of the Poly(A) Binding Protein-Poly(A) Complex

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