A-to-I RNA Editing

Adenosine-to-inosine (A-to-I) RNA editing is a post-transcriptional modification, catalyzed by ADAR enzymes, that chemically converts adenosine bases within double-stranded RNA into inosine. Because inosine is interpreted as guanosine by both the translation machinery and downstream sequencing analysis, editing can alter protein-coding sequences, splicing, and RNA structure. Editing changes RNA base-pairing in two opposite ways depending on the original mismatch: converting a normal A-U pair produces a weaker I·U wobble pair, while converting an A:C mismatch produces a more stable I-C pair. This dual effect on RNA structural stability makes A-to-I editing a key determinant of whether endogenous double-stranded RNA is recognized by innate immune RNA sensors.