TIF4631 and TIF4632: two yeast genes encoding the high-molecular-weight subunits of the cap-binding protein complex (eukaryotic initiation factor 4F) contain an RNA recognition motif-like sequence and carry out an essential function.

Goyer, C; Altmann, Michael; Lee, H. S.; Blanc, A; Deshmukh, Mohanish; Woolford, John L.; Trachsel, Hans; Sonenberg, Nahum

doi:10.1128/mcb.13.8.4860

Cited by 174 publications

(229 citation statements)

References 86 publications

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“…More importantly, in Saccharomyces cerevisiae two genes were identified (TIF4631 and TIF4632) as encoding eIF4G proteins. Although TIF4631-disrupted strains exhibited a slowgrowth phenotype, disruption of TIF4632 failed to show any phenotype, while a double disruption of these genes was lethal (7). These last observations also emphasized some functional difference between the two forms of eIF4G, which fits well with our data.…”

Section: Discussionsupporting

confidence: 81%

“…eIF4G proteins contain a central region that interacts with specific RNA domains such as internal ribosomal entry sites of viral RNAs and also short motifs that exhibit general RNA-binding activities that are critical for ribosome scanning (7,22,38). Also, yeast eIF4G interacts with eIF1 and eIF5, and this interaction is required for the optimal AUG selection, indicating that yeIF4G participates in the selection of the initiation codon (14).…”

Section: Discussionmentioning

confidence: 99%

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Selective Modification of Eukaryotic Initiation Factor 4F (eIF4F) at the Onset of Cell Differentiation: Recruitment of eIF4GII and Long-Lasting Phosphorylation of eIF4E

Caron

Charon

Cramer

et al. 2004

Molecular and Cellular Biology

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mRNA translation is mainly regulated at the level of initiation, a process that involves the synergistic action of the 5 cap structure and the 3 poly(A) tail at the ends of eukaryotic mRNA. The eukaryote initiation factor 4G(eIF4G) is a pivotal scaffold protein that forms a critical link between mRNA cap structure, poly(A) tail, and the small ribosomal subunit. There are two functional homologs of eIF4G in mammals, the original eIF4G, renamed eIF4GI, and eIF4GII that functionally complements eIF4GI. To date, biochemical and functional analysis have not identified differential activities for eIF4GI and eIF4GII. In this report, we demonstrate that eIF4GII, but not eIF4GI, is selectively recruited to capped mRNA at the onset of cell differentiation. This recruitment is coincident with a strong and long-lasting phosphorylation of eIF4E and the release of 4E-BP1, a suppressor of eIF4E function, from the cap structure, without a concomitant change in 4E-BP1's phosphorylation. Our data further indicate that cytokines such as thrombopoietin can differentially regulate eIF4GI/II activities. These results provide the first evidence that eIF4GI/II does fulfill selective roles in mammalian cells.

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Section: Discussionsupporting

confidence: 81%

Section: Discussionmentioning

confidence: 99%

Selective Modification of Eukaryotic Initiation Factor 4F (eIF4F) at the Onset of Cell Differentiation: Recruitment of eIF4GII and Long-Lasting Phosphorylation of eIF4E

Caron

Charon

Cramer

et al. 2004

Molecular and Cellular Biology

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“…5). Similar results are described for other translation initiation factors (eIF4G, eIF5A) whose genes are duplicated, and their products do not contribute equally to growth (25,43).…”

Section: Discussionsupporting

confidence: 69%

“…23. A 1.9-kb PstI fragment from pUC13-TIF2 (24) was cloned into the PstI site of the above vectors; a 3.5-kb EcoRI fragment from pUC19-STM1 (19) was cloned into the EcoRI site; a 1.9-kb HindIII-PstI fragment of pUC9-CDC33 (M. Altmann) was cloned into the HindIII-PstI sites; a 6.7-kb EcoRI fragment from YCG206 containing the TIF4631 gene (25) was cloned into the EcoRI site; and a 1.85-kb EcoRI fragment from YEp131-2 containing the CAF20 gene (M. Altmann) was cloned into the EcoRI site. The 1.4-kb KpnI-SalI fragments containing either cdc33-42, cdc33-43, or cdc33-44 alleles from the pMDA101 plasmids (10) were cloned into YCplac33 or YEplac195.…”

mentioning

confidence: 99%

The p20 and Ded1 proteins have antagonistic roles in eIF4E-dependent translation in Saccharomyces cerevisiae

Cruz¹,

Iost²,

Kressler³

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

197

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The translation initiation factor eIF4E mediates the binding of the small ribosomal subunit to the cap structure at the 5 end of the mRNA. In Saccharomyces cerevisiae, the cap-binding protein eIF4E is mainly associated with eIF4G, forming the cap-binding complex eIF4F. Other proteins are detected upon purification of the complex on cap-affinity columns. Among them is p20, a protein of unknown function encoded by the CAF20 gene. Here, we show a negative regulatory role for the p20 protein in translation initiation. Deletion of CAF20 partially suppresses mutations in translation initiation factors. Overexpression of the p20 protein results in a synthetic enhancement of translation mutation phenotypes. Similar effects are observed for mutations in the DED1 gene, which we have isolated as a multicopy suppressor of a temperature-sensitive eIF4E mutation. The DED1 gene encodes a putative RNA helicase of the DEAD-box family. The analyses of its suppressor activity, of polysome profiles of ded1 mutant strains, and of synthetic lethal interactions with different translation mutants indicate that the Ded1 protein has a role in translation initiation in S. cerevisiae.

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“…They also identified two longer primer extension products (−390 and −580), one of which corresponds to that previously reported by Goyer et al (1993), and that was used in our study. In their discussion, Verge et al (2004) concede that "we cannot exclude that additional longer forms of the TIF4631 mRNA are produced and perhaps translated by internal initiation".…”

mentioning

confidence: 60%

Reevaluation of the conclusion that IRES-activity reported within the 5′ leader of the TIF4631 gene is due to promoter activity

Mauro

Edelman²,

Zhou³

2004

RNA

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We previously reported that the 5 leader of the mRNA-encoding initiation factor eIF4G in Saccharomyces cerevisiae can function as a translational enhancer and as an internal ribosome entry site (IRES) when tested in cells. However, Verge and colleagues recently suggested that this sequence does not facilitate translation initiation, but inhibits translation in vitro and has promoter activity when tested in cells. We disagree with these conclusions and respond by showing that the data are most consistent with an internal initiation mechanism.Keywords: IRES; TIF4631; eIF4G; translation; mRNA Verge et al. (2004), in the February issue of RNA, reported that contrary to our earlier publication (Zhou et al. 2001), the 5Ј leader of the TIF4631 mRNA does not enhance translation initiation or contain an IRES. The authors assert that they have identified a promoter, located 36-112 nucleotides upstream of the translation initiation site, and concluded in their abstract, "The data show that the IRES activity reported earlier is due to this promoter". However, in our study, the IRES activity was localized primarily to a segment of the 5Ј leader that is completely independent of this putative promoter (nucleotides 250-390, see Fig. 1). Moreover, we showed that a segment of the TIF4631 gene containing the putative promoter had a background level of activity when tested in the intercistronic region of a dicistronic mRNA (construct p150 ). This low level of activity was ∼1% of the activity of the full-length 5Ј leader.The notion that the IRES activities observed in our study were derived from the translation of a shorter monocistronic mRNA is also not consistent with the high levels of activity reported in our paper. By accounting for the differences in luminescence between the Renilla and Photinus luciferases, we estimate that the second cistron expressed ∼40% as much protein as the first cistron in constructs containing the TIF4631 5Ј leader. Inasmuch as the dicistronic mRNA was easily detected in our study, a shorter monocistronic transcript should also have been easily identified; however, we found no evidence for such a transcript, even when our Northern blots were overexposed. Verge et al. (2004) reported promoter activity within the 5Ј leader of the TIF4631 mRNA; however, they did not directly test for this activity, for example, by testing the fragment in question in a promoterless vector or with Northern blots. Instead, indirect methods were used to assess promoter activity. For example, mRNA species were detected by PCR analysis. This is a highly sensitive technique that will detect trace amounts of RNA; however, their experiments were not performed in a quantitative manner, consequently it is not possible to compare mRNA levels or to draw conclusions about the production of a monocistronic mRNA from this data. This limitation is indicated by an internal inconsistency in their data: In transformed cells for which the expression of the dicistronic mRNAs was not induced, the authors obtained a PCR band correspond...

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TIF4631 and TIF4632: two yeast genes encoding the high-molecular-weight subunits of the cap-binding protein complex (eukaryotic initiation factor 4F) contain an RNA recognition motif-like sequence and carry out an essential function.

Cited by 174 publications

References 86 publications

Selective Modification of Eukaryotic Initiation Factor 4F (eIF4F) at the Onset of Cell Differentiation: Recruitment of eIF4GII and Long-Lasting Phosphorylation of eIF4E

Selective Modification of Eukaryotic Initiation Factor 4F (eIF4F) at the Onset of Cell Differentiation: Recruitment of eIF4GII and Long-Lasting Phosphorylation of eIF4E

The p20 and Ded1 proteins have antagonistic roles in eIF4E-dependent translation in Saccharomyces cerevisiae

Reevaluation of the conclusion that IRES-activity reported within the 5′ leader of the TIF4631 gene is due to promoter activity

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