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PMID: 9671055 Published · ppublish English Comparative Study Journal Article Research Support, Non-U.S. Gov't

Translational activation of uncapped mRNAs by the central part of human eIF4G is 5' end-dependent.

RNA (New York, N.Y.) ·Vol. 4 ·No. 7 ·1998-07-00 ·Pages 828-36

De Gregorio E, Preiss T, Hentze MW

Abstract

Translation initiation factor (eIF) 4G represents a critical link between mRNAs and 40S ribosomal subunits during translation initiation. It interacts directly with the cap-binding protein eIF4E through its N-terminal part, and binds eIF3 and eIF4A through the central and C-terminal region. We expressed and purified recombinant variants of human eIF4G lacking the N-terminal domain as GST-fusion proteins, and studied their function in cell-free translation reactions. Both eIF4G lacking its N-terminal part (aa 486-1404) and the central part alone (aa 486-935) exert a dominant negative effect on the translation of capped mRNAs. Furthermore, these polypeptides potently stimulate the translation of uncapped mRNAs. Although this stimulation is cap-independent, it is shown to be dependent on the accessibility of the mRNA 5' end. These results reveal two unexpected features of eIF4G-mediated translation. First, the C-terminal eIF4A binding site is dispensable for activation of uncapped mRNA translation. Second, translation of uncapped mRNA still requires 5' end-dependent ribosome binding. These new findings are incorporated into existing models of mammalian translation initiation.

MeSH Terms
Escherichia coli/genetics Eukaryotic Initiation Factor-4G Humans Iron-Regulatory Proteins Iron-Sulfur Proteins Oligonucleotides, Antisense Peptide Initiation Factors/genetics,metabolism Protein Biosynthesis RNA Caps/metabolism RNA, Messenger/metabolism RNA-Binding Proteins Recombinant Proteins/metabolism
Chemicals
Eukaryotic Initiation Factor-4G Iron-Regulatory Proteins Iron-Sulfur Proteins Oligonucleotides, Antisense Peptide Initiation Factors RNA Caps RNA, Messenger RNA-Binding Proteins Recombinant Proteins
Authors & Affiliations
3 authors, click to expand affiliations / ORCID
De Gregorio E
Gene Expression Programme, European Molecular Biology Laboratory, Heidelberg, Germany.
Preiss T
Hentze M W
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Article Info
Journal
RNA (New York, N.Y.)
Abbr.
RNA
ISSN
1355-8382
DOI
10.1017/s1355838298980372
Published
1998-07-00
Pages
828-36
Language
English
Region
United States
NLM ID
9509184
PMCID
PMC1369662
Subset
IM
External Links
PubMed source DOI: 10.1017/s1355838298980372 PMC Full Text View journal details
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