Interaction of the eukaryotic initiation factor 4E with 4E-BP2 at a dynamic bipartite interface

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• Cap-dependent translation initiation is crucial for gene expression.
• Regulation involves eukaryotic initiation factor 4E (eIF4E) and eIF4E binding proteins (4E-BPs).
• Previous studies focused on short 4E-BP peptides, lacking atomic-level detail for full-length proteins.

Purpose of the Study:

• To characterize the dynamic, structural, and binding properties of the interaction between full-length 4E-BP2 and eIF4E at atomic resolution.
• To elucidate the binding interface and its implications for translational regulation.

Main Methods:

• Isothermal titration calorimetry (ITC) was employed to assess binding thermodynamics.
• Nuclear magnetic resonance (NMR) spectroscopy was used for structural and dynamic characterization.
• Detailed analysis of the bipartite binding interface between 4E-BP2 and eIF4E.

Main Results:

• 4E-BP2, though intrinsically disordered, exhibits fluctuating secondary structures.
• A bipartite interface, including canonical ⁵⁴YXXXXLΦ⁶⁰ and ⁷⁸IPGVT⁸² sites, mediates binding to eIF4E.
• Individual binding elements show submicromolar affinity, with rapid exchange dynamics within a nanomolar complex.
• This dynamic interaction exposes regulatory phosphorylation sites.

Conclusions:

• The interaction between 4E-BP2 and eIF4E is extensive and dynamic, involving multiple binding sites.
• The 4E-BP2 binding interface on eIF4E is larger than that of eIF4G.
• These findings suggest potential for developing targeted therapeutics by differentially modulating these interactions.