mRNA reading frame maintenance during eukaryotic ribosome translocation.

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Protein synthesis involves coupled translocation of messenger RNA (mRNA) and transfer RNAs (tRNAs) to advance the reading frame.
• Eukaryotic translocation is accelerated and its fidelity maintained by elongation factor 2 (eEF2).
• Limited structural data exists for eukaryotic ribosome translocation.

Purpose of the Study:

• To elucidate the mechanism of eukaryotic ribosome translocation.
• To visualize the progression of mRNA-tRNA-peptide modules during translocation.
• To understand the role of eEF2 and eukaryote-specific elements in translational accuracy.

Main Methods:

• High-resolution cryogenic-electron microscopy (cryo-EM).
• Analysis of ten structures of the elongating eukaryotic ribosome.
• Inclusion of mRNA, peptidyl-tRNA, deacylated tRNA, and modified eEF2.

Main Results:

• Detailed structures capture translocation from eEF2 accommodation to late stages.
• Identified intricate interactions preventing translational reading frame slippage.
• Demonstrated reliance on eukaryote-specific ribosome, eEF2, and tRNA elements for accuracy.

Conclusions:

• Eukaryotic translocation accuracy is ensured by specific molecular components and interactions.
• Findings illuminate the mechanism of translation arrest by sordarin.
• Diphthamide modification in eEF2 stabilizes codon-anticodon interactions and enhances translational fidelity.