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Published on: December 28, 2016
Cell cycle-dependent phosphorylation of the translational repressor eIF-4E binding protein-1 (4E-BP1)
K J Heesom1, A Gampel, H Mellor
1University of Bristol, Department of Biochemistry, School of Medical Sciences, University Walk, BS8 1TD, Bristol, United Kingdom. k.heesom@bristol.ac.uk
Current Biology : CB
|September 13, 2001
Summary
Protein synthesis initiation is regulated by the eukaryotic initiation factor 4F (eIF-4F) complex. Mitotic phosphorylation of 4E-BP1 by cdc2 releases eIF-4E, activating translation.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Protein synthesis initiation is a critical regulatory step controlled by the eukaryotic initiation factor 4F (eIF-4F) complex.
- The availability of the mRNA cap-binding protein, eIF-4E, is essential for eIF-4F formation and is regulated by eIF-4E binding proteins (4E-BPs).
- Phosphorylation of 4E-BP1 promotes its dissociation from eIF-4E, thereby enabling translation initiation.
Purpose of the Study:
- To investigate the changes in 4E-BP1 phosphorylation during mitosis.
- To identify the specific sites of 4E-BP1 phosphorylation during mitosis.
- To determine the kinase responsible for phosphorylating 4E-BP1 at Thr-70.
Main Methods:
- Western blotting to detect phosphorylated 4E-BP1.
- Mass spectrometry to identify phosphorylation sites.
- In vitro kinase assays using purified cdc2 and 4E-BP1.
Main Results:
- 4E-BP1 phosphorylation significantly increases during mitosis.
- Ser-65 and Thr-70 were identified as the key phosphorylation sites on 4E-BP1.
- The cyclin-dependent kinase cdc2 was identified as the kinase that phosphorylates 4E-BP1 at Thr-70.
- Phosphorylation of Thr-70 by cdc2 is a prerequisite for Ser-65 phosphorylation.
- Increased mitotic phosphorylation of 4E-BP1 leads to its complete dissociation from eIF-4E.
Conclusions:
- Mitotic phosphorylation of 4E-BP1 by cdc2 at Thr-70 and Ser-65 is a key regulatory mechanism.
- This phosphorylation event releases eIF-4E, facilitating the formation of translationally active eIF-4F complexes.
- The findings elucidate a novel mechanism controlling protein synthesis during mitosis.
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