eIF4A alleviates the translational repression mediated by classical secondary structures more than by G-quadruplexes

Area of Science:

• Molecular Biology
• Cancer Therapeutics
• RNA Structure

Background:

• Increased eukaryotic initiation factor 4A (eIF4A) activity promotes cancer by altering mRNA translation.
• eIF4A is a target for novel cancer therapies.
• The role of G-quadruplexes in cellular mRNA regulation is debated.

Purpose of the Study:

• To investigate the structural preferences of (GGC)4 motifs in mRNA 5'UTRs.
• To determine the role of eIF4A in unwinding these structures.
• To clarify the relationship between eIF4A activity, mRNA secondary structures, and translation.

Main Methods:

• Reverse transcription stalling assays.
• 7-deazaguanine incorporation experiments.
• In vitro and cellular translation assays using the eIF4A inhibitor hippuristanol.
• G-quadruplex stabilizing ligand experiments.

Main Results:

• (GGC)4 motifs in full-length mRNAs preferentially form classical secondary structures over G-quadruplexes.
• eIF4A activity alleviates translational repression of mRNAs with classical secondary structures more than G-quadruplexes.
• Stabilizing G-quadruplex formation reduces eIF4A dependency.

Conclusions:

• The enrichment of (GGC)4 motifs in eIF4A-dependent mRNA 5'UTRs is likely due to the formation of stable hairpin structures, not G-quadruplexes.
• eIF4A primarily unwinds these hairpin structures to facilitate translation.
• This finding has implications for understanding mRNA regulation and developing targeted cancer therapies.