MLN51 stimulates the RNA-helicase activity of eIF4AIII

Area of Science:

• Molecular Biology
• RNA Biology
• Protein Biochemistry

Background:

• The exon-junction complex (EJC) is crucial for post-transcriptional gene expression regulation.
• Key EJC core components include Y14, Magoh, MLN51, and the DEAD-box RNA helicase eIF4AIII.

Purpose of the Study:

• To investigate the regulatory roles of MLN51 and the Y14-Magoh complex on the ATPase and RNA helicase activities of eIF4AIII.
• To elucidate the functional interplay between EJC core proteins and their impact on RNA binding.

Main Methods:

• Enzyme kinetics assays were performed to measure the ATPase activity of eIF4AIII in the presence of MLN51 and/or Y14-Magoh.
• RNA binding affinity studies were conducted using purified protein complexes.
• RNA helicase activity assays were utilized to assess the functional consequences of protein interactions.

Main Results:

• MLN51 significantly stimulates eIF4AIII's ATPase activity, decreasing K(M) and increasing k(cat).
• The Y14-Magoh complex inhibits MLN51-stimulated ATPase activity, but not to basal levels.
• The ATP-bound eIF4AIII-MLN51 complex exhibits a 100-fold higher affinity for RNA compared to the unbound form; ATP hydrolysis reduces RNA affinity.
• MLN51 enhances the RNA-helicase activity of eIF4AIII.

Conclusions:

• MLN51 and Y14-Magoh exert opposing regulatory effects on eIF4AIII's ATPase activity.
• The regulation of eIF4AIII's ATPase cycle by EJC core proteins is critical for modulating its RNA binding affinity.
• MLN51-stimulated RNA helicase activity suggests a direct functional role in RNA processing or transport.