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. Author manuscript; available in PMC: 2019 Jun 7.
Published in final edited form as: Mol Cell. 2018 Jun 7;70(5):814–824.e6. doi: 10.1016/j.molcel.2018.05.002

Figure 7. Characteristic features of spacer acquisition in Cas4 deletion strains.

Figure 7

(A) Adaptation frequency is inferred from PCR intensities (Figure 2A). Spacer size shows average size and size range for 90% of total spacers. PAM shows consensus motifs found upstream (PAM) and downstream (NW motif) from the protospacer. Spacer orientation indicates whether spacers were integrated into the CRISPR array in both orientations, or in the correct orientation with respect to the PAM. (B) Model for Cas4 functions in P. furiosus spacer acquisition. Cas1, Cas2, Cas4-1 and Cas4-2 can capture and trim spacers with both a PAM and a NW motif and then integrate them into the CRISPR array in the correct orientation. The resulting new spacers can produce crRNAs capable of initiating target interference.