Cellular RNA substrates susceptible to off-target adenine deamination by the TadA deaminase domain (RNA off-targets of ABE)

Cellular RNA substrates susceptible to off-target adenine deamination refer to the vast array of RNA molecules unintentionally modified by Adenine Base Editors (ABEs). ABEs typically employ a laboratory-evolved TadA (tRNA-specific adenosine deaminase) domain from Escherichia coli, fused to a CRISPR-Cas protein, to perform targeted A-to-G transitions in genomic DNA (Gaudelli et al., 2017). However, studies have revealed that the TadA domain retains an inherent affinity for RNA, leading to extensive, guide-independent A-to-I (adenosine-to-inosine) deamination across the transcriptome (Grünewald et al., 2019; Rees et al., 2019). Because inosine is recognized as guanosine by the cellular translation machinery, these off-target events can result in the synthesis of synonymous or non-synonymous protein variants, potentially causing cellular toxicity or functional impairment. While RNA editing is transient and does not permanently alter the genome, the high frequency and breadth of these modifications present a significant safety hurdle for the clinical translation of base editing therapies. Consequently, next-generation ABEs are being engineered with specific mutations in the TadA domain to minimize RNA binding while maintaining high DNA editing efficiency.

Other names

Transcriptome-wide off-target RNA editingABE-induced RNA deaminationOff-target A-to-I RNA editingTadA-mediated RNA editingGuide-independent RNA editing

Hydrolytic deamination of adenosine to inosine in RNA transcripts, which is read as guanosine by the translation machinery.