Fig. 2
From: CRISPR Cpf1 proteins: structure, function and implications for genome editing
Assembling and activation of CRISPR Cpf1–crRNA complex. Cpf1 (purple) recognizes a pseudoknot that formed by the repeat-derived segment of the pre-crRNA (gray). Subsequent to pre-crRNA binding, Cpf1 itself cleaves the 5′ end of the crRNA by endonucleolytic activity. But, it is currently unclear which RNase processes the crRNA 3′ end. Recognizing a 5′-TTTV-3′ PAM (yellow) in a DNA target (brown) triggers the base pairing of the spacer-derived segment of the crRNA (green) with complementary target DNA. Target DNA cleavage mediated by Cpf1 makes a PAM-distal dsDNA break with 5′ overhangs