Repressor binding to a dorsal regulatory site traps human eIF4E in a high cap-affinity state

Area of Science:

• Molecular Biology
• Gene Expression Regulation
• Protein-Protein Interactions

Background:

• Eukaryotic translation initiation is regulated at the 5' mRNA cap by the eukaryotic initiation factor 4F (eIF4F) complex.
• Signal transduction pathways modulate gene expression by controlling translation initiation.
• 4E-binding proteins (4E-BPs) are repressors that inhibit the function of the cap-binding protein eIF4E.

Purpose of the Study:

• To investigate the molecular interactions between 4E-BPs and human eIF4E.
• To elucidate the mechanism by which 4E-BPs inhibit eIF4E function.
• To provide a quantitative framework for translational regulation.

Main Methods:

• Investigated molecular interactions underlying the inhibition of human eIF4E by 4E-binding proteins (4E-BPs).
• Analyzed the binding competition between 4E-BPs and eIF4G for eIF4E.
• Determined binding affinities and contacts between 4E-BP1/2 and eIF4E.

Main Results:

• 4E-BPs 1 and 2 compete with eIF4G for binding to a dorsal site on eIF4E.
• 4E-BP binding enhances cap-binding affinity of eIF4E, trapping it in inactive complexes.
• Distinct binding properties of 4E-BP1 and 4E-BP2 are attributed to three amino acids in a conserved motif.

Conclusions:

• 4E-BPs regulate translation by competitively binding to eIF4E, distinct from eIF4G.
• The interaction mechanism reveals a novel model for translational control.
• Quantitative data on binding affinities provide insights into the regulation of gene expression.