User:Benbest/sandbox/PAM

The canonical PAM is the sequence 5'-NGG-3' where "N" is any nucleobase followed by two guanine ("G") nucleobases. Although the canonical PAM is associated with the Cas9 nuclease of Streptococcus pyogenes, different PAMs are associated with the Cas9 proteins of the bacteria Neisseria meningitidis, Treponema denticola, and Streptococcus thermophilus. 5'-NGA-3' can be a highly efficient non-canonical PAM for human cells, but efficiency varies with genome location. Attempts have been made to engineer PAMs which could improve the efficiency of CRISPR-Cas9 gene editing for different genome locations.