Substitutional A-to-I RNA editing.

Adenosine-to-inosine (A-to-I) editing catalyzed by adenosine deaminases acting on RNA (ADARs) entails the chemical conversion of adenosine residues to inosine residues within double-stranded RNA (dsRNA) substrates. Inosine base pairs as guanosine and A-to-I editing can therefore alter the structure and base pairing properties of the RNA molecule. This has a biological significance in controlling the amount of functional RNA molecules in the cell, in expanding the functionality of a limited set of transcripts, and in defending the cell against certain RNA viruses. A-to-I editing is not limited to any specific type of RNA substrate. Instead, it can affect any RNA molecule able to attain the required double-stranded structure. This includes microRNAs, small interfering RNAs, viral RNAs, and messenger RNAs with potential for recoding events and splice site modifications. 2010 John Wiley & Sons, Ltd