The most prevalent type of RNA editing is mediated by ADAR (adenosine deaminase acting on RNA) enzymes, which convert adenosines to inosines (a process known as A—>I RNA editing) in double-stranded (ds)RNA substrates.
A—>I RNA editing was long thought to affect only selected transcripts by altering the proteins they encode. However, genome-wide screening has revealed numerous editing sites within inverted Alu repeats in introns and untranslated regions.
A—>I RNA editing crosstalks with RNA-interference pathways, which, like A—>I RNA editing, involve dsRNAs. A—>I RNA editing therefore seems to have additional functions, including the regulation of retrotransposons and gene silencing, which adds a new urgency to the challenges of fully understanding ADAR functions.
References
Nishikura K. Editor meets silencer: crosstalk between RNA editing and RNA interference. Nat Rev Mol Cell Biol. 2006 Dec;7(12):919-31. PMID: 17139332
Anant S, Davidson NO. Hydrolytic nucleoside and nucleotide deamination, and genetic instability: a possible link between RNA-editing enzymes and cancer? Trends Mol Med. 2003 Apr;9(4):147-52. PMID: 12727140