Editor meets silencer: crosstalk between RNA editing and RNA interference.

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. Also, recent evidence indicates that 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.