The binding selectivity of ADAR2's dsRBMs contributes to RNA-editing selectivity

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• ADAR2 (Adenosine Deaminase Acting on RNA 2) is an enzyme catalyzing RNA editing.
• RNA editing involves altering specific nucleotide bases within RNA molecules.
• ADAR2 utilizes double-stranded RNA binding motifs (dsRBMs) for substrate recognition.

Purpose of the Study:

• To investigate the role of ADAR2's dsRBMs in RNA editing site selectivity.
• To understand how ADAR2 distinguishes between different RNA duplex structures.
• To correlate dsRBM binding selectivity with RNA editing efficiency.

Main Methods:

• Analysis of ADAR2 dsRBM binding to a mimic of the GluR-B Q/R editing site.
• Comparison of ADAR2 dsRBM selectivity with that of PKR's dsRBM I.
• Use of directed hydroxyl radical cleavage data to generate molecular models.
• Chemical modification of RNA to block predicted binding surfaces.
• Assessment of RNA editing activity in wild-type and mutant ADAR2 enzymes.

Main Results:

• ADAR2 dsRBMs exhibit selective binding to a specific RNA duplex mimicking the GluR-B Q/R site.
• dsRBMs from different proteins (ADAR2 vs. PKR) show distinct binding selectivities.
• Molecular models predicted key RNA recognition surfaces for ADAR2 dsRBMs.
• Blocking these RNA surfaces with benzyl modification significantly impeded ADAR2-mediated editing.
• A mutant ADAR2 lacking dsRBM I provided insights into the binding site responsible for editing at the GluR-B Q/R site.

Conclusions:

• ADAR2's dsRBMs play a critical role in conferring site selectivity for RNA editing.
• The intrinsic binding selectivity of dsRBMs contributes to ADAR2's substrate specificity.
• Specific RNA-protein interactions mediated by dsRBMs are essential for efficient and accurate RNA editing.