Highly specific and efficient RNA A-to-I editing

RNA editing can be a promising therapeutic approach. However, ectopic expression of RNA editing enzymes was found to trigger off-target editing, and the recruitment of endogenous adenosine deaminase acting on RNA (ADAR) suffers from low efficiency and fluctuating ADAR expression. Here, we identified ADAR inhibitors (ADIs) that suppressed the activity of the fused ADAR2 deaminase domain (ADAR2DD). Using ADI, we developed an RNA transformer adenine base editor (RtABE) with both high specificity and high efficiency. With the fusion of ADI to ADAR2DD, RtABE remains inactive until it binds its target site. After binding to the target site, ADI is cleaved from ADAR2DD and RtABE becomes active. RtABE induced efficient on-target editing in various cells with different ADAR expression levels. RtABE is a highly specific and efficient RNA editing system with broad applicability.