  A-To-I RNA editing is common to all eukaryotes, associated with various
neurological functions. Recently, A-to-I editing was found to occur abundantly
in the human transcriptome. Here we show that the frequency of A-to-I editing
in humans is at least an order of magnitude higher as that of mouse, rat,
chicken or fly. The extraordinary frequency of RNA editing in human is
explained by the dominance of the primate-specific Alu element in the human
transcriptome, which increases the number of double-stranded RNA substrates.
