A structural inventory of native ribosomal ABCE1-43S pre-initiation complexes

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Eukaryotic translation initiation involves persistent factors like eIF3 complex, eIF3j, and ABCE1 on ribosomal sub-complexes.
• ABCE1 (Rli1 in yeast) functions as a recycling factor but remains bound to the 40S subunit, with its role and context unclear.

Purpose of the Study:

• To elucidate the native architectural context and functional role of ABCE1 in pre-initiation complexes.
• To provide a molecular inventory of ABCE1-containing complexes during translation initiation.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to determine the architecture of native yeast and human ABCE1-containing pre-initiation complexes.
• Analysis focused on the interactions within the 43S and 48S initiation phases.

Main Results:

• ABCE1 was found in early 43S and later 48S initiation phases, adopting a novel hybrid conformation.
• ABCE1 interacted with the N-terminus of eIF3j, which occupied the mRNA entry channel via its C-terminus.
• A detailed molecular picture of the 43S-bound eIF3 complex and eIF2 ternary complex was obtained.

Conclusions:

• The study provides structural insights into the interaction network of eIF3 and eIF2 complexes during translation initiation.
• The findings clarify the antagonistic role of eIF3j in mRNA binding and the structural basis of ABCE1's function in translation.
• This work advances our understanding of the intricate mechanisms governing eukaryotic translation initiation.