Fig. 1: Overview of CRISPR-Cas nucleases.
From: Assessing and advancing the safety of CRISPR-Cas tools: from DNA to RNA editing
a–c CRISPR–Cas9 nucleases and CRISPR-Cas12 nucleases are RNA-guided DNA editing tools, whereas CRISPR-Cas13 nucleases have RNA-guided RNA endonuclease activity. Besides targeted cutting, CRISPR-Cas12/13 nucleases also have collateral cutting activity on non-target DNA/RNA templates. Streptococcus pyogenes (SpCas9) recognizes a relatively common 3’ NGG PAM, and functions optimally with 20-nt spacers, while Cas12a orthologs generally use 5’ T-rich PAMs. PAM protospacer adjacent motif, PFS protospacer flanking site.
