ADAR1 converts adenosine to inosine in dsRNA, which destabilizes the dsRNA helix. This activity is important for various functions like site-specific RNA editing of transcripts of the glutamate receptors and modifying viral RNA genomes (which may be responsible for hypermutation of certain negative-stranded viruses, e.g., measles virus). ADAR1 also binds to short interfering RNAs (siRNA) without editing them and suppresses siRNA-mediated RNA interference. This protein is ubiquitously expressed, with the highest levels being found in brain and lung.