ABSTRACT
During genome editing, both ZFNs and TALENs utilize a nuclease (FokI) that requires dimerization to cut. Since the FokI cleavage domain used in ZFNs and TALENs is activated via dimerization, ZFN and TALENs require the construction and delivery of two protein halves. MegaTALs combine the easy-to-design DNA-binding domains from TALENs with the high cleavage efficiency of meganucleases in a single chimeric protein. The meganucleases cause less toxicity in cells when compared to ZFNs and TALENs. ZFNs, TALENs, and CRISPR are modular proteins. ZFNs and TALENs use FokI as the nuclease while CRISPR uses Cas proteins. MegaTALs use a combination of TAL effector nucleases and meganucleases. MegaTALs are highly specific, although they are complex to reprogram for the recognition of novel DNA targets. ZFNs, TALENs, and megaTALs tolerate small numbers of positional mismatches. Engineering in ZFNs and megaTALs is difficult, with TALENs engineering being moderately complex. CRISPR is easy to engineer. MegaTALs, ZFNs, TALENs, and CRISPR achieve efficient gene editing above 70% when in cell lines with high-level delivery and no toxicity.
