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. Author manuscript; available in PMC: 2017 Nov 22.
Published in final edited form as: Bioessays. 2017 May 11;39(6):10.1002/bies.201700019. doi: 10.1002/bies.201700019

Figure 1.

Figure 1

Schematic recognition and processing of CRISPR repeat-spacer array by Cas6. Repeats are colored in red and spacers are in various colors. In general, the palindromic feature in CRISPR repeats leads to an RNA stem-loop structure recognized by Cas6 (represented by the crystal structure of Pyrococcus furiosus Cas6 PDB id 3I4M). The secondary elements of Cas6 involved in binding RNA are labeled for one of the Cas6 models. Cleavage at the base of the stem releases the intermediate for the Type III or mature crRNA for the Type I CRISPR systems. The intermediate is further processed by uncharacterized activities to the final crRNA that contains the 5′-tag and the spacers.