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Monitoring eIF4F Assembly by Measuring eIF4E-eIF4G Interaction in Live Cells
Published on: May 1, 2020
Synergistic activation of eIF4A by eIF4B and eIF4G
Klaus H Nielsen1, Manja A Behrens, Yangzi He
1Department of Molecular Biology, Aarhus University, Gustav Wieds Vej 10C, DK-8000 Aarhus, Denmark. khn@mb.au.dk
Nucleic Acids Research
|November 30, 2010
Summary
This study reveals how eukaryotic translation initiation factors eIF4B and eIF4G stimulate eIF4A. They bind eIF4A through a two-site model, with eIF4G acting catalytically to promote complex formation and synergistic ATPase activity.
Area of Science:
- Molecular Biology
- Protein Biochemistry
- Eukaryotic Gene Expression
Background:
- eIF4A is crucial for eukaryotic translation initiation.
- The precise roles of auxiliary factors eIF4B and eIF4G in stimulating eIF4A activity remain unclear.
- Understanding these interactions is key to deciphering translation regulation.
Purpose of the Study:
- To elucidate the mechanism by which eIF4B and eIF4G stimulate the function of eIF4A.
- To characterize the binding interactions between eIF4A, eIF4B, and eIF4G.
- To investigate the structural basis for eIF4G's role in translation initiation.
Main Methods:
- Isothermal titration calorimetry (ITC) to determine binding affinities.
- Small-angle X-ray scattering (SAXS) to analyze the structure of eIF4G fragments.
- In vitro RNA pull-down assays to study complex formation.
- ATPase activity assays to measure eIF4A stimulation.
Main Results:
- A two-site model for eIF4A binding to eIF4G-MC was proposed, with high (∼50 nM) and low (∼1000 nM) affinity sites.
- The eIF4G-MC fragment exhibits an elongated structure (220 Å) capable of spanning the 40S ribosomal subunit.
- A stable eIF4A-eIF4B complex requiring RNA, nucleotide, and eIF4G-MC was established.
- eIF4G-MC acts catalytically in complex formation, not as a stable component.
- eIF4B and eIF4G-MC synergistically stimulate eIF4A's ATPase activity.
Conclusions:
- eIF4G acts catalytically to facilitate the formation of the eIF4A-eIF4B-RNA-nucleotide complex.
- Synergistic stimulation of eIF4A ATPase activity by eIF4B and eIF4G is crucial for translation initiation.
- The structural and binding data provide insights into the coordinated action of these factors in regulating translation.
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