Table 1 Key differences between the Cas9 and Cas12a CRISPR proteins
Feature | Cas9 | Cas12a (Cpf1) |
|---|---|---|
CRISPR enzyme | Class 2, Type II-B Molecular weight: ~ 164 kDa Endonuclease domains: RuvC and HNH | Class 2, Type V-A Molecular weight: ~ 158 kDa Endonuclease domains: RuvC only |
PAM | 3′ NGG | 5′ TTTV |
guideRNA | ~ 120 nt, two RNA sequences crRNA and tracrRNA are synthetically fused to form the single guide RNA (sgRNA) | ~ 43 nt, only crRNA is required |
crRNA maturation | RNase III dependent | RNase III independent, autonomous processing |
DSB cleavage site | 3 bases upstream of the protospacer sequence PAM site often destroyed during genome editing | 18–23 bases downstream of the PAM PAM site may be preserved after genome editing |
DSB cleavage mechanism | Blunt end cuts | 5-nt staggered end cut distal to the PAM |