Ubiquitination and proteasome-dependent degradation of human eukaryotic translation initiation factor 4E.

Translation initiation factor 4E (eIF4E) is a cytoplasmic cap-binding protein that is required for cap-dependent translation initiation. Here, we have shown that eIF4E is ubiquitinated primarily at Lys-159 and incubation of cells with a proteasome inhibitor leads to increased eIF4E levels, suggesting the proteasome-dependent proteolysis of ubiquitinated eIF4E. Ubiquitinated eIF4E ...
retained its cap binding ability, whereas eIF4E phosphorylation and eIF4G binding were reduced by ubiquitination. The W73A mutant of eIF4E exhibited enhanced ubiquitination/degradation, and 4E-BP overexpression protected eIF4E from ubiquitination/degradation. Because heat shock or the expression of the carboxyl terminus of heat shock cognate protein 70-interacting protein (Chip) dramatically increased eIF4E ubiquitination, Chip may be at least one ubiquitin E3 ligase responsible for eIF4E ubiquitination.
Mesh Terms:
Cell Line, Cytoplasm, Eukaryotic Initiation Factor-4E, Humans, Lysine, Mutation, Phosphorylation, Proteasome Endopeptidase Complex, Protein Biosynthesis, Protein Structure, Tertiary, RNA Caps, Sepharose, Ubiquitin, Ubiquitin-Protein Ligases
J. Biol. Chem.
Date: Jul. 28, 2006
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