Unstructured protein domains stabilize RNA binding and mediate RNA folding by AUF1

Area of Science:

• Molecular Biology
• Biochemistry
• Gene Regulation

Background:

• AUF1 is an RNA-binding protein regulating gene expression post-transcriptionally.
• It targets AU-rich elements in mRNAs of inflammatory mediators and oncoproteins.
• Mechanisms of AUF1 RNA interaction and regulation are not fully understood.

Purpose of the Study:

• To define the biochemical basis of RNA recognition by AUF1.
• To investigate the role of different AUF1 domains in RNA binding and remodeling.
• To use the smallest AUF1 isoform (p37AUF1) as a model system.

Main Methods:

• Quantitative fluorescence anisotropy assays.
• Analysis of protein mutants and truncations.
• Biochemical characterization of RNA-protein interactions.

Main Results:

• The tandem RNA recognition motifs (RRMs) of p37AUF1 exhibit weak binding to AU-rich elements.
• N- and C-terminal flanking domains contribute to RNA:protein complex stabilization.
• Residues N-terminal to RRMs and the C-terminal domain are critical for high-affinity binding and RNA remodeling.
• The C-terminal domain engages in non-base-specific RNA contacts and may undergo conformational changes.

Conclusions:

• AUF1's flanking domains play distinct, crucial roles in RNA binding and remodeling.
• The C-terminal domain is essential for high-affinity binding and RNA structural changes.
• Findings provide insight into the molecular mechanisms of AUF1-mediated gene regulation.