The ADAR proteins deaminate adenosine to inosine in double-stranded RNA which is one of the most abundant modifications present in mammalian RNA. Inosine can have a profound effect on the RNAs that are edited, not only changing the base-pairing properties, but can also result in recoding, as inosine behaves as if it were guanosine. In mammals there are three ADAR proteins and two ADAR-related proteins (ADAD) expressed. All have a very similar modular structure; however, both their expression and biological function differ significantly. Only two of the ADAR proteins have enzymatic activity. However, both ADAR and ADAD proteins possess the ability to bind double-strand RNA. Mutations in ADARs have been associated with many diseases ranging from cancer, innate immunity to neurological disorders. Here, we will discuss in detail the domain structure of mammalian ADARs, the effects of RNA editing, and the role of ADARs in human diseases.

CEITEC Central European Institute of Technology Masaryk University Kamenice 5 Brno 625 00 Czech Republic

Oncohaematoogy Department Ospedale Pediatrico Bambino Gesù Viale di San Paolo Roma 15 00146 Italy

Paul O'Gorman Leukaemia Research Centre Institute of Cancer Sciences College of Medical Veterinary and Life Sciences University of Glasgow 21 Shelley Road Glasgow G12 0ZD UK

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