Aug 2026· Biotechnology Advances· pp.
109018
· 0 citations· 203 references
Medicine
TL;DR
This review focuses on the action mode of different base editors, highlights their interplays with the TLS, summarizes their potential therapeutic applications and discusses perspective strategies to improve precision and expand targeting scope.
Abstract
Base editors (BEs) are transformative genome engineering tools that enable precise nucleotide substitutions without inducing double-strand breaks (DSBs) or requiring donor DNA templates. Since the first cytosine base editor (CBE) was developed in 2016, the field has advanced rapidly, with the creation of diverse BE variants that incorporate distinct deaminases and glycosylases. These engineered editors have significantly expanded the scope of genome editing by generating deaminated bases or apurinic/apyrimidinic (AP) site lesions, thereby harnessing endogenous DNA repair or replication mechanisms to produce base transitions and transversions. Among these endogenous pathways, trans-lesion synthesis (TLS) plays a particularly critical role in converting AP sites into specific base substitutions. TLS polymerases insert nucleotides opposite AP lesions, and the final editing outcome is dictated by the unique nucleotide preferences of individual TLS polymerases. This review focuses on the action mode of different base editors, highlights their interplays with the TLS, summarizes their potential therapeutic applications and discusses perspective strategies to improve precision and expand targeting scope.
This review compares Cas9-mediated homology-directed repair (HDR) with generations of cytosine base editors (CBE1–CBE3), adenine base editors (ABE1-ABE7), and prime editors (PE1–PE3b), focusing on their mechanistic distinctions, efficiencies, delivery challenges, and therapeutic applications.
Anoushka Sinha· American Journal of Student...· 0 citations
Key remaining challenges include bystander editing within the activity window, residual off-target DNA and RNA editing, delivery constraints, delivery constraints, immunogenicity, and the need for durable long-term safety evidence across relevant cell types and disease contexts.
Moksada Regmi, K. Ma, C. Bi et al.· Cell Genomics· 0 citations
The effectiveness of the SaCas9 modular base editors, the robustness of the platform’s modularity, and its feasibility for convenient screening of target-specific base editors are demonstrated.
J. Collantes, Kellen Xu, M. Ruiz-Urigüen et al.· The CRISPR Journal· 0 citations
A single-nucleotide resolution ABE created by fusing a nickase Cas9, nCas9-H840A, with the deaminase domain of ADAR, which acts on DNA:RNA hybrids, instead of TadA, which acts on single-stranded DNA in conventional ABEs.
Hyeon Woo Im, Bada Jeong, Yeji Lee et al.· Nature Biotechnology· 1 citation
Base editors hold great promise in endogenous mutagenesis for genetic screening. However, the development of base editors that induce saturated multi-base conversions with diverse mutation spectrum is challenging. Here, we develop triple base editors (smACGs) that simultaneously mutagenize adenine, cytosine, and guanine within the same allele. Through screening and embedding engineered deaminase and alkyladenine DNA glycosylase variants in Cas9 structure, smACGmax is generated to catalyze robust triple-base conversion efficiencies of up to 41% across varied sequence contexts while maintaining low RNA off-target effects compared to previous dual-base editors. We apply smACGmax to enable high coverage (94%) of targeted HBEGF mutagenesis that identified diphtheria toxin-resistant mutations and to dissect SF3B1 variants with alternative splicing specificity via complex single, double, and triple base conversion screening. smACGmax expands base conversion capability from single and double substrates to trinucleotide level, which facilitates the generation of high-diversity and complex genetic variants, providing a useful platform for mutagenesis-based application. Broad-spectrum base mutagenesis at the same endogenous loci with base editors remains a challenge. Here, the authors developed smACGmax to catalyze efficient multi-base conversions across adenine, cytosine and guanine, and enable high-diversity functional screening in HBEGF and SF3B1 variants.
Abstract Traditional adenine base editors (ABEs), primarily derived from TadA, suffer from bystander editing and limited diversity, while artificial intelligence (AI)-designed deaminases such as Deam-P32 exhibit lower efficiency and precision than state-of-the-art editors such as ABE8e. Here, we report the OpenABE variants through the structure-guided evolution of Deam-P32 by optimizing DNA engagement and the base-contacting pocket and incorporating C-terminal extensions from ABE8e. These variants achieved a 16–36-fold increase in A-to-G conversion efficiency over Deam-P32, matching the editing efficiency of ABE8e across 29 endogenous nuclear loci while mitigating bystander cytosine editing. OpenABEs also reduced ATC motif bystander editing and produced fewer guide RNA-independent off-target effects on DNA and RNA. Further, we adapted these variants to mitochondrial DNA editing by designing OpenABE-TALEDs, which yielded editing efficiencies comparable or superior to those of ABE8e-TALEDs. Delivery through engineered virus-like particles further enhanced specificity and product purity. These results demonstrate that structure-guided refinement of AI-designed deaminases can produce precise, versatile base editors for nuclear and mitochondrial genomes, expanding the research and therapeutic applications of genome editing toolkits.