Nature biotechnologySep 4, 2025

Targeted DNA modification triggers precise repair in bacteria and causes mutations in complex cells

CRISPR Gene Editing Weekly Brief ↗PubMed ↗DOI ↗OA ↗

Updated Jan 20, 2026

Abstract

This approach enables the targeted addition of ADP-ribosyl moieties to DNA, leading to distinct editing outcomes in different organisms.

Base editors create precise genomic edits without causing DNA breaks but only explore a limited range of modifications.
The bacterial antiphage toxin DarT2 is used to append chemical groups to DNA, expanding the potential for genome editing.
In tested bacteria, the targeted addition of ADP-ribosyl moieties facilitates homologous recombination, allowing for flexible genome editing.
In yeast, plant, and human cells, the modifications result in the conversion of thymine to adenine or a mix of adenine and cytosine, with minimal insertions or deletions.
The method, termed append editing, provides new editing possibilities that current base editors cannot achieve.

Simplified

Base editors create precise genomic edits by directing nucleobase deamination or removal without inducing double-stranded DNA breaks. However, a vast chemical space of other DNA modifications remains to be explored for genome editing. Here we harness the bacterial antiphage toxin DarT2 to append ADP-ribosyl moieties to DNA, unlocking distinct editing outcomes in bacteria versus eukaryotes. Fusing an attenuated DarT2 to a Cas9 nickase, we program site-specific ADP-ribosylation of thymines within a target DNA sequence. In tested bacteria, targeting drives homologous recombination, offering flexible and scar-free genome editing without base replacement or counterselection. In tested yeast, plant and human cells, targeting drives substitution of the modified thymine to adenine or a mixture of adenine and cytosine with limited insertions or deletions, offering edits inaccessible to current base editors. Altogether, our approach, called append editing, leverages the addition of chemical moieties to DNA to expand current modalities for precision gene editing.