Table 2.
Comparison of protein-targeted genome engineering
| HE | ZFN | TALEN | |
|---|---|---|---|
| DNA ends at DSB | 3′ extension | 5′ extension | 5′ extension |
| Sequence availability | Limited by existing enzymes | Limited by triplet recognition of ZFs | Limited by first nucleotide (T) |
| Context effects | Common | Common | Uncommon |
| Specificity | High | Intermediate | High |
| Off-target effects | Low | Intermediate | Low |
| Enzyme engineering | Complex | Intermediate | Straightforward |
| Size compactness (modularity) | Small (monomeric) | Large (monomeric and dimeric) | Very large (dimeric) |