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. 2014 Jul;42(13):8816-29.
doi: 10.1093/nar/gku573. Epub 2014 Jul 10.

MegaTevs: single-chain dual nucleases for efficient gene disruption

Jason M Wolfs  1 , Matthew DaSilva  1 , Sarah E Meister  1 , Xu Wang  2 , Caroline Schild-Poulter  3 , David R Edgell  4
Affiliations

MegaTevs: single-chain dual nucleases for efficient gene disruption

Jason M Wolfs et al. Nucleic Acids Res. 2014 Jul.

Abstract

Targeting gene disruptions in complex genomes relies on imprecise repair by the non-homologous end-joining DNA pathway, creating mutagenic insertions or deletions (indels) at the break point. DNA end-processing enzymes are often co-expressed with genome-editing nucleases to enhance the frequency of indels, as the compatible cohesive ends generated by the nucleases can be precisely repaired, leading to a cycle of cleavage and non-mutagenic repair. Here, we present an alternative strategy to bias repair toward gene disruption by fusing two different nuclease active sites from I-TevI (a GIY-YIG enzyme) and I-OnuI E2 (an engineered meganuclease) into a single polypeptide chain. In vitro, the MegaTev enzyme generates two double-strand breaks to excise an intervening 30-bp fragment. In HEK 293 cells, we observe a high frequency of gene disruption without co-expression of DNA end-processing enzymes. Deep sequencing of disrupted target sites revealed minimal processing, consistent with the MegaTev sequestering the double-strand breaks from the DNA repair machinery. Off-target profiling revealed no detectable cleavage at sites where the I-TevI CNNNG cleavage motif is not appropriately spaced from the I-OnuI binding site. The MegaTev enzyme represents a small, programmable nuclease platform for extremely specific genome-engineering applications.

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