Figure 3.

Protection of prespacers from 3′–5′ exonuclease cleavage by Cas1-Cas2. Shown are time courses of DnaQ or ExoT cleavage of an unprocessed prespacer. A, radiolabeling of the non-PAM strand in the absence of Cas1-Cas2. B, radiolabeling of the PAM strand in the absence of Cas1-Cas2. C, radiolabeling of the non-PAM strand in the presence of Cas1-Cas2. D, radiolabeling of the PAM strand in the presence of Cas1-Cas2. In all panels, a schematic of the experimental setup is shown above the gel images, with a star indicating which strand is radiolabeled. On the right side of each gel image is a schematic highlighting cleavage of the unprocessed prespacer.