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Precision genome engineering with programmable DNA-nicking enzymes
Zinc finger nuclease (ZFNs) are powerful tools of genome engineering but are limited by their inevitable reliance on error-prone non-homologous end-joining (NHEJ) repair of DNA double-strand breaks (DSBs), which gives rise to randomly-generated, unwanted small insertions or deletions (indels) at both on-target and off-target sites. Here, we present programmable DNA-nicking enzymes (nickases), which produce single-strand breaks (SSBs) or nicks, instead of DSBs, that are repaired by error-free homologous recombination (HR) rather than mutagenic NHEJ. Unlike their corresponding nucleases, zinc finger nickases allow site-specific genome modifications only at the on-target site, without the induction of unwanted indels. We propose that programmable nickases will be of broad utility in research, medicine, and biotechnology, enabling precision genome engineering in any cell or organism.