Double-stranded RNA adenosine deaminases ADAR1 and ADAR2 have overlapping specificities

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Adenosine deaminases that act on RNA (ADARs) modify RNA by converting adenosine to inosine.
• ADAR enzymes bind double-stranded RNA (dsRNA) but exhibit sequence-specific deamination.
• While Xenopus ADAR1 specificity is well-studied, human ADAR2 specificity remains largely uncharacterized.

Purpose of the Study:

• To directly compare the deamination specificity of human ADAR1 and ADAR2.
• To elucidate the intrinsic sequence preferences of ADAR2.
• To understand the selectivity of ADAR1 and ADAR2 in deaminating specific adenosines within an RNA molecule.

Main Methods:

• Comparative analysis of human ADAR1 and ADAR2 enzymatic activity.
• Determination of 5' and 3' neighbor nucleotide preferences for each ADAR enzyme.
• Identification of preferred trinucleotide sequences for ADAR2.
• Assessment of ADAR enzyme selectivity on various RNA substrates.

Main Results:

• Human ADAR2 exhibits both 5' neighbor preferences (A≈U>C=G) and novel 3' neighbor preferences (U=G>C=A).
• ADAR2 prefers specific trinucleotide sequences, including UAU, AAG, UAG, and AAU.
• ADAR1 and ADAR2 demonstrate similar RNA selectivity, suggesting substrate-dictated editing extent.
• Xenopus and human ADAR1 show conserved editing patterns across tested RNAs.

Conclusions:

• This study significantly advances the understanding of human ADAR2 deamination specificity.
• The identified preferences provide a basis for predicting ADAR enzyme activity at specific RNA editing sites in vivo.
• Findings highlight conserved functions of ADAR1 across species and delineate unique features of ADAR2.