From: Synthetic epigenetics—towards intelligent control of epigenetic states and cell identity
 | Zinc fingers | TAL effectors | CRISPR/Cas9 |
---|---|---|---|
Origin | Eukaryotic species | Phytopathogenic bacteria | Bacterial and archaea species |
Type of DNA recognition | Protein:DNA | Protein:DNA | RNP:DNA (Watson-Crick base pairing) |
Function of the protein of origin | Transcription factors | Transcription factors | DNA nuclease (inactivated for use in epigenetic editing) |
Sensitivity to DNA modification | Sensitive to DNA modification | Sensitive to DNA modification | Not sensitive to DNA modification state |
Recognition sequence length | Potentially long, but not all sequences can be recognized, size restrictions apply | Potentially very long, constraints apply | 17–20 bp, requires an adjacent PAM sequence |
Specificity/off-target effects | Less specific than TALEs | Most specific | More relaxed sequence recognition than ZF and TALES |
Size of protein | Variable—depends on length of recognized sequence, one protein unit (approximately 3 kDa) per 3 bp of recognition sequence | Variable—depends on length of recognized sequence. Typically 50-70 kDa | Holoenzyme (~160 kDa) |
Immunogenicity | Similar to natural mammalian proteins, potentially low immunogenicity | Unknown, needs further investigation | Unnatural for mammals, potentially high immunogenicity, needs further studies |
Multiplexing | Difficult and labour intensive | Difficult and labour intensive | Easy and possible |