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. Author manuscript; available in PMC: 2018 Apr 22.
Published in final edited form as: J Allergy Clin Immunol. 2017 Mar;139(3):726–732. doi: 10.1016/j.jaci.2017.01.007

Figure 3. Gene editing using site-specific endonucleases.

Figure 3

Site-specific endonucleases (ZFNs, TALENs, or CRISPR/Cas9) can be used to create targeted double stranded DNA breaks. These DNA breaks can be repaired by non-homologous end joining, which introduces small insertions and deletions and can be used for gene knockout strategies, as is employed in the CCR5 gene therapy trials for HIV. If a corrective donor DNA sequence is also provided to the cell, it can be used for homology-directed repair of the double-stranded DNA break, incorporating the therapeutic gene sequence and maintaining its expression under its endogenous regulatory elements.