RNA editing of the microRNA-151 precursor blocks cleavage by the Dicer-TRBP complex

MicroRNAs (miRNAs) mediate translational repression or degradation of their target messenger RNAs by RNA interference (RNAi). The primary transcripts of miRNA genes (pri-miRNAs) are sequentially processed by the nuclear Drosha-DGCR8 complex to approximately 60-70 nucleotide (nt) intermediates (premiRNAs) and then by the cytoplasmic Dicer-TRBP complex to approximately 20-22 nt mature miRNAs. Certain pri-miRNAs are subject to RNA editing that converts adenosine to inosine (A -> I RNA editing); however, the fate of edited pri-miRNAs is mostly unknown. Here, we provide evidence that RNA editing of primiR-151 results in complete blockage of its cleavage by Dicer and accumulation of edited pre-miR-151 RNAs. Our results indicate that A -> I conversion at two specific positions of the pre-miRNA foldback structure can affect its interaction with the Dicer-TRBP complex, showing a new regulatory role of A -> I RNA editing in miRNA biogenesis.