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Phosphorylation of eukaryotic initiation factor 4E markedly reduces its affinity for capped mRNA
Gert C Scheper1, Barbara van Kollenburg, Jianzhong Hu
1School of Life Sciences, MSI/WTB Complex, University of Dundee, Dundee DD1 5EH, United Kingdom. g.c.scheper@dundee.ac.uk
The Journal of Biological Chemistry
|November 28, 2001
Summary
Phosphorylation of eukaryotic initiation factor 4E (eIF4E) at Ser(209) reduces its affinity for mRNA caps, impacting translation initiation. This modification accelerates eIF4E dissociation from RNA, even with eIF4E-binding protein 1 present.
Area of Science:
- Molecular Biology
- Biochemistry
- Cell Biology
Background:
- Translation initiation in eukaryotes involves eukaryotic initiation factor 4E (eIF4E) binding to mRNA caps.
- Phosphorylation of eIF4E at Ser(209) by mitogens and cytokines is a known regulatory event.
- The functional impact of eIF4E phosphorylation on cap binding has been unclear.
Purpose of the Study:
- To investigate the functional consequences of eIF4E phosphorylation on mRNA cap binding affinity.
- To elucidate the role of specific residues in eIF4E's interaction with capped RNA.
Main Methods:
- Fluorescence spectroscopy
- Surface plasmon resonance (SPR) techniques
- Analysis of variant eIF4E proteins
Main Results:
- Phosphorylation of eIF4E significantly decreases its affinity for capped RNA, mainly by increasing dissociation rates.
- Negatively charged residues at position 209 mimic the effect of phosphorylation, reducing cap binding.
- A basic residue at position 159 is critical for eIF4E's cap-binding capability.
- eIF4E-binding protein 1 stabilizes phosphorylated eIF4E binding but does not fully abolish the increased dissociation rate.
Conclusions:
- eIF4E phosphorylation at Ser(209) negatively regulates its interaction with mRNA caps.
- This phosphorylation-induced decrease in cap affinity likely plays a role in controlling translation initiation.
- Specific amino acid residues, including those at positions 159 and 209, are crucial for eIF4E function in cap binding.