Improved cytosine base editors generated from TadA variants.

Cytosine base editors (CBEs) enable programmable genomic C·G-to-T·A transition mutations and typically comprise a modified CRISPR-Cas enzyme, a naturally occurring cytidine deaminase, and an inhibitor of uracil repair. Previous studies have shown that CBEs utilizing naturally occurring cytidine deaminases may cause unguided, genome-wide cytosine deamination. While improved CBEs that decrease stochastic genome-wide off-targets have subsequently been reported, these editors can suffer from suboptimal on-target performance. Here, we report the generation and characterization of CBEs that use engineered variants of TadA (CBE-T) that enable high on-target C·G to T·A across a sequence-diverse set of genomic loci, demonstrate robust activity in primary cells and cause no detectable elevation in genome-wide mutation. Additionally, we report cytosine and adenine base editors (CABEs) catalyzing both A-to-I and C-to-U editing (CABE-Ts). Together with ABEs, CBE-Ts and CABE-Ts enable the programmable installation of all transition mutations using laboratory-evolved TadA variants with improved properties relative to previously reported CBEs. © 2023. The Author(s).

Citation

Dieter K Lam, Patricia R Feliciano, Amena Arif, Tanggis Bohnuud, Thomas P Fernandez, Jason M Gehrke, Phil Grayson, Kin D Lee, Manuel A Ortega, Courtney Sawyer, Noah D Schwaegerle, Leila Peraro, Lauren Young, Seung-Joo Lee, Giuseppe Ciaramella, Nicole M Gaudelli. Improved cytosine base editors generated from TadA variants. Nature biotechnology. 2023 May;41(5):686-697

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PMID: 36624149

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