Functional reconstitution of human eukaryotic translation initiation factor 3 (eIF3)

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Protein fate in eukaryotes is regulated by conserved complexes like the proteasome, COP9 signalosome, and eukaryotic translation initiation factor 3 (eIF3).
• eIF3 plays a crucial role in translation initiation, a fundamental process for protein synthesis.

Purpose of the Study:

• To reconstitute the 13-subunit human eIF3 complex in Escherichia coli.
• To elucidate the structural organization and functional interactions of the eIF3 complex.

Main Methods:

• Reconstitution of the 13-subunit human eIF3 complex in E. coli.
• Negative-stain electron microscopy (EM) for structural analysis.
• Biochemical assays to assess interactions with ribosomal subunits and RNA.

Main Results:

• The structural core of eIF3 comprises eight subunits conserved with the proteasome and COP9 signalosome.
• This core binds to the 40S ribosomal subunit, translation initiation factors, and hepatitis C viral (HCV) IRES RNA.
• The complete eIF3 complex facilitates the assembly of initiation complexes with HCV IRES RNA.

Conclusions:

• The conserved structural core of eIF3 is essential for organizing the complex and mediating translation initiation.
• eIF3's structure enables its interaction with key components of the translation machinery and viral RNA elements.
• This study provides insights into the architecture and function of a fundamental translation initiation factor.