The eukaryotic initiation factor (eIF) 5 HEAT domain mediates multifactor assembly and scanning with distinct...

Area of Science:

• Molecular Biology
• Protein Interactions
• Gene Expression Regulation

Background:

• Eukaryotic translation initiation factor 5 (eIF5) is essential for forming the eukaryotic preinitiation complex.
• The C-terminal HEAT domain of eIF5 mediates interactions with other initiation factors, but its specific binding sites were unknown.

Purpose of the Study:

• To identify the binding sites on the eIF5 C-terminal domain (CTD) for interacting translation factors.
• To understand the role of these binding sites in preinitiation complex assembly and function.

Main Methods:

• Homology modeling of the eIF5-CTD based on the HEAT domain of eIF2Bepsilon.
• Identification of distinct surface regions on eIF5-CTD responsible for binding eIF1, eIF2beta, eIF3c, and eIF4G.

Main Results:

• A homology model revealed specific binding sites on eIF5-CTD: aromatic/acidic boxes for eIF2beta, a basic residue region for eIF1 and eIF3c, and an overlapping interface for eIF4G.
• Mutations in these identified surface areas disrupted preinitiation complex interactions and impaired GCN4 translational control.

Conclusions:

• The eIF5 HEAT domain acts as a nucleation core for preinitiation complex assembly.
• Distinct surface areas on eIF5-CTD are critical for mediating interactions with multiple translation factors, ensuring proper complex formation and function.