eIF5B gates the transition from translation initiation to elongation

Area of Science:

• Molecular Biology
• Biochemistry
• Cell Biology

Background:

• Translation initiation is crucial for protein synthesis, determining protein quantity and identity by setting the mRNA reading frame.
• The dynamics of translation initiation, particularly the transition to elongation in eukaryotic cells, remain incompletely understood.
• Numerous translation initiation factors are involved in preparing ribosomes for polypeptide synthesis.

Purpose of the Study:

• To investigate the dynamics of late translation initiation and the transition to elongation in a eukaryotic system.
• To elucidate the role of eukaryotic initiation factor 5B (eIF5B) in the transition from translation initiation to elongation.
• To understand the regulatory mechanisms governing the switch from translation initiation to elongation.

Main Methods:

• Utilized in vitro single-molecule fluorescence microscopy.
• Employed a purified yeast Saccharomyces cerevisiae translation system.
• Monitored the pathways of late translation initiation and the transition to elongation in real time.

Main Results:

• The transition from translation initiation to elongation in yeast is slower than in E. coli.
• A prolonged residence time of eIF5B on the 80S ribosome was observed after ribosomal subunit joining.
• Inhibiting eIF5B's GTPase activity post-subunit joining prevented eIF5B dissociation and subsequent elongation.

Conclusions:

• eIF5B dissociation serves as a kinetic checkpoint for the transition from translation initiation to elongation.
• Ribosome conformational changes triggering GTP hydrolysis likely govern eIF5B release.
• Understanding this checkpoint is vital for comprehending eukaryotic protein synthesis regulation.