Target-stabilized base editors enable robust high-fidelity RNA editing

RNA base editing using engineered deaminases represents a powerful tool to correct mutations at the RNA level. However, widespread off-target effects, primarily arising from dissociated free deaminases, remain a significant challenge. Here, we devise the RECODE (RNA editing with conditionally stable and enhanced ADAR1 deaminase variants) system, which employs designer degron-tagged ADAR1 deaminase (ADAR1d) with guide RNA (gRNA)-regulated stability. By promoting degradation of gRNA-unbound ADAR1d, RECODE markedly reduces transcriptome-wide edits while maintaining high on-target efficacy. Engineering gRNA for target RNA-induced conformational switching confines ADAR1d stabilization to intended editing sites, further enhancing editing precision. With structure-guided rational engineering of ADAR1d, RECODE efficiently corrects an Amyotrophic Lateral Sclerosis-relevant FUS mutation and installs a therapeutic mutation to Angptl3 in vivo, which mitigate FUS mislocalization to neuronal axons and lower plasma lipids, respectively. These findings establish RECODE as a highly stringent and efficient RNA editing technology and underscore a general principle for enhancing the specificity of RNA-guided protein effectors. Engineered RNA base editors are powerful yet limited by promiscuous deaminase activity. Here, the authors devise RECODE that enforces target-dependent deaminase stabilization, thereby reducing off-target edits, and achieving effective in vivo editing of FUS and Angptl3.