EF-G-induced ribosome sliding along the noncoding mRNA

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Translational bypassing allows ribosomes to synthesize proteins from discontinuous reading frames on mRNA.
• The mechanisms initiating ribosome sliding over noncoding mRNA regions are not fully understood.

Purpose of the Study:

• To elucidate the mechanism by which ribosomes initiate translational bypassing.
• To identify the factors and events involved in ribosome sliding over noncoding mRNA sequences.

Main Methods:

• Investigated ribosome dynamics during translational bypassing using structural and biochemical assays.
• Utilized mRNA stem-loops as A-site transfer RNA mimics to study EF-G function.
• Measured guanosine 5'-triphosphate hydrolysis during the bypassing event.

Main Results:

• Elongation factor G (EF-G) triggers ribosome "take-off" via a pseudotranslocation event.
• A small mRNA stem-loop acts as an A-site transfer RNA mimic, facilitating EF-G-mediated bypassing.
• Ribosome sliding requires significant GTP hydrolysis and results in a hyper-rotated conformation, similar to stalled ribosomes.

Conclusions:

• EF-G plays a novel role in initiating translational bypassing by promoting ribosome sliding.
• The study reveals a mechanism for ribosomes to traverse untranslated mRNA regions.
• Identified common ribosome dynamics during translation stalling and bypassing events.