Phylogenetic and structural analysis of Hydra ADAR

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Structural Biology

Background:

• Adenosine deaminases acting on RNAs (ADARs) are key enzymes catalyzing adenosine-to-inosine (A-to-I) RNA editing.
• While ADAR editing's roles in diverse animals are known, biochemical and structural data on these enzymes are scarce.

Purpose of the Study:

• To investigate the evolutionary and structural characteristics of medusozoan ADAR2 enzymes.
• To characterize the structure and activity of an ADAR ortholog from Hydra vulgaris.

Main Methods:

• Phylogenetic sequence analysis and AlphaFold computational structure prediction.
• Crystal structure determination of the hyADAR deaminase domain.
• Direct detection of A-to-I RNA editing by hyADAR.

Main Results:

• Medusozoan ADAR2s possess five dsRNA binding domains (dsRBDs) with conserved RNA binding residues.
• Evolutionary divergence observed between medusozoan and anthozoan ADARs, with distinct RNA binding loop lengths and dimerization motifs.
• Crystal structure of hyADAR deaminase domain revealed conserved active site architecture and essential cofactor binding.

Conclusions:

• Medusozoans exhibit unique ADAR structural features potentially linked to novel biological functions.
• This study provides a foundation for further biochemical and structural studies of ADARs across metazoans.
• Understanding ADAR diversity is crucial for deciphering the varied roles of RNA editing.