The mammalian Adenosine Deaminases Acting on RNA (ADAR) constitute a family of sequence-related proteins involved in pre-mRNA editing of nuclear transcripts through site-speci?c adenosine modi?cation. ADARs are not active on adenosine-mononucleotide and are only distantly related by sequence to adenosine and AMP deaminases involved in purine metabolism. The ADARs convert certain adenosine bases in an RNA transcript into inosines by removing an amino group involved in Watson-Crick base pairing. The ADARs recognize a double stranded RNA (dsRNA) structure in the transcript that is formed between the editing site complementary sequence (ECS), usually located in the downstream 3