Control of eIF4E cellular localization by eIF4E-binding proteins, 4E-BPs |
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Authors: | Rong Liwei Livingstone Mark Sukarieh Rami Petroulakis Emmanuel Gingras Anne-Claude Crosby Katherine Smith Bradley Polakiewicz Roberto D Pelletier Jerry Ferraiuolo Maria A Sonenberg Nahum |
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Institution: | Department of Biochemistry, McGill University, Montréal, Québec H3G 1Y6, Canada. |
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Abstract: | Eukaryotic initiation factor (eIF) 4E, the mRNA 5'-cap-binding protein, mediates the association of eIF4F with the mRNA 5'-cap structure to stimulate cap-dependent translation initiation in the cytoplasm. The assembly of eIF4E into the eIF4F complex is negatively regulated through a family of repressor proteins, called the eIF4E-binding proteins (4E-BPs). eIF4E is also present in the nucleus, where it is thought to stimulate nuclear-cytoplasmic transport of certain mRNAs. eIF4E is transported to the nucleus via its interaction with 4E-T (4E-transporter), but it is unclear how it is retained in the nucleus. Here we show that a sizable fraction (approximately 30%) of 4E-BP1 is localized to the nucleus, where it binds eIF4E. In mouse embryo fibroblasts (MEFs) subjected to serum starvation and/or rapamycin treatment, nuclear 4E-BPs sequester eIF4E in the nucleus. A dramatic loss of nuclear 4E-BP1 occurs in c-Ha-Ras-expressing MEFs, which fail to show starvation-induced nuclear accumulation of eIF4E. Therefore, 4E-BP1 is a regulator of eIF4E cellular localization. |
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Keywords: | extracellular stimuli intracellular localization mRNA translation control mTor signaling |
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