Extensive adenosine-to-inosine editing detected in Alu repeats of antisense RNAs reveals scarcity of sense–antisense duplex formation

One type of RNA editing converts adenosine residues to inosine in double-stranded regions. Recent transcriptome analysis has revealed that numerous Alu repeats, present within introns and untranslated regions of human transcripts, are subject to this A → I RNA editing. Furthermore, it revealed global transcription of antisense RNAs. Here, we demonstrate that antisense RNAs are also edited extensively but only in their Alu repeat sequences, and editing does not extend to the surrounding sequence. Our findings imply that sense and antisense RNAs form two separate intramolecular double-stranded RNAs consisting of inversely oriented Alu repeats, but rarely form intermolecular duplexes.