Structure of translation factor eIF4E bound to m7GDP and interaction with 4E-binding protein

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Eukaryotic translation initiation is controlled by the mRNA cap-binding protein, eukaryotic initiation factor 4E (eIF4E).
• eIF4E activity is regulated by its interaction with eIF4G to form the eIF4F complex, and by 4E-binding proteins (4E-BPs) that inhibit this interaction.
• Understanding the structural basis of these interactions is crucial for deciphering translation regulation.

Purpose of the Study:

• To determine the three-dimensional structure of the yeast eIF4E in complex with its mRNA cap analog.
• To identify the binding site for 4E-BP on eIF4E.
• To elucidate the structural mechanisms underlying translation regulation by eIF4E.

Main Methods:

• X-ray crystallography was used to solve the structure of the yeast eIF4E/m7Gpp complex in a CHAPS micelle.
• The structure of a ternary complex with m7GpppA was determined to locate the second nucleotide.
• Structural analysis was performed to identify the 4E-BP binding site.

Main Results:

• The crystal structure of yeast eIF4E bound to the mRNA cap analog m7Gpp was determined.
• The structure reveals a curved eight-stranded antiparallel beta-sheet core with associated helices.
• The mRNA cap (m7G) binds within a pocket formed by a stack of tryptophans, and the 4E-BP binding site is adjacent to, but distinct from, the cap-binding site.

Conclusions:

• The solved structure provides a detailed molecular model of eIF4E bound to the mRNA cap.
• The identified 4E-BP binding site explains how 4E-BPs inhibit eIF4E activity by preventing eIF4G binding.
• These findings offer structural insights into the regulation of eukaryotic translation initiation.