Structural basis for recognition of diverse localizing mRNAs by Egl-BicD

Area of Science:

• Molecular Biology
• Cell Biology
• Structural Biology

Background:

• mRNA localization directs protein function, crucial for cellular processes.
• RNA-binding proteins (RBPs) interact with specific mRNA sequences or structures.
• Specificity in mRNA recognition by RBPs with variable signals remains a key question.

Purpose of the Study:

• Investigate the molecular mechanism of mRNA recognition by the Drosophila RBP Egalitarian (Egl).
• Determine how Egl achieves specificity in binding diverse mRNA localization signals.
• Elucidate the structural basis of Egl-RNA interactions.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to determine structures of Egl-BicD bound to six different RNAs.
• Biochemical assays to analyze RNA binding and transport initiation.
• Structural analysis of RNA stem-loop conformations and RBP interactions.

Main Results:

• Egl utilizes multiple noncanonical double-stranded RNA-binding domains to form a recognition pocket.
• mRNA localization signals adopt a bent stem-loop conformation for Egl engagement.
• Egl dimers bind RNA through coincident detection of two RNA elements, coupling binding to transport.

Conclusions:

• mRNA localization relies on a combination of RNA shape, positional sequence features, and structured elements.
• Egl employs a unique strategy to selectively bind and transport diverse mRNAs.
• This provides insight into the molecular mechanisms of spatial protein regulation in cells.