Genomic DNA adenines susceptible to residual TadA-derived off-target deamination

Genomic DNA adenines susceptible to residual TadA-derived off-target deamination are specific nucleotide positions within the genome where Adenine Base Editors (ABEs) cause unintended A-to-G transitions. ABEs utilize an evolved tRNA-specific adenosine deaminase (TadA) fused to a CRISPR-Cas protein to perform targeted base editing [1]. However, the TadA domain can exhibit stochastic, guide-independent activity on single-stranded DNA (ssDNA) exposed during processes like transcription or replication [2]. This results in the conversion of adenosine to inosine, which is subsequently read as guanosine by DNA polymerases, creating permanent mutations [3]. These off-target events are a major concern in gene therapy because they can occur at high frequencies across the genome, potentially leading to the disruption of tumor suppressor genes or the activation of oncogenes [4]. Efforts to mitigate this include the engineering of high-fidelity TadA variants with reduced ssDNA affinity and the use of sensitive detection assays like Digenome-seq or GOTI to monitor genomic integrity [5].

Other names

Off-target DNA adenine sitesABE-mediated off-target sitesTadA-dependent DNA off-targetssgRNA-independent ABE off-targetsResidual TadA activity sites

Deamination of adenosine to inosine by TadA-derived enzymes, resulting in A-to-G transitions during DNA replication or repair.