Characterization of promiscuous A-to-I RNA editing clustered in non-repetitive editing boxes. (A) Neighbor preferences of A-to-I RNA editing clustered in non-repetitive or non-Alu repetitive editing boxes. Site “0” indicates the editing sites. Probabilities of two upstream and two downstream nucleotides are indicated. (B) Structure prediction suggests a dsRNA duplex of two editing boxes in chr2. Genomic locations of two adjacent editing boxes are highlighted by different colors. (C) Editing of editing boxes is independent of adjacent IRAlus. Sequences with editing boxes were cloned into 3′UTR of egfp mRNA with a pair of adjacent IRAlus (pEGFP-2 EB-IRAlus), a single Alu (pEGFP-2 EB-Alu) or non-Alu (pEGFP-2 EB). (D) Editing levels in IRAlus, single Alu and editing boxes of each transfected plasmid shown in (C). “+++”, extensive editing; “-”, low editing; “N.A.”, not detected.