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. 2020 Mar 4;8:62. doi: 10.3389/fbioe.2020.00062

FIGURE 5.

FIGURE 5

The basic working principle of type I Cascade-based technologies. (A) Strategy for native type I Cascade-based applications. A DNA stretch immediately 5′ downstream of a PAM is selected for mini-CRISPR construction. crRNA expressed from the plasmid-borne mini-CRISPR array forms the Cascade complex with Cas proteins expressed from the genomic cas operon. (B) Architecture of type I Cascade-mediated genome engineering. (C) Architecture of type I Cascade-mediated gene expression modulation. The Cascade is directed to the target site in the host genome, either recruiting the Cas3 to generate a double-stranded DNA break (DSDB) in wild-type (WT) cells (B) or binding to the target tightly without cleaving it in a cas3 knockout background (C). (D) Schematic showing an example of genome editing by repurposing the type I-F of Zymomonas mobilis [constructed according to Zheng et al. (2019)]. (E) Schematic showing an example of selective killing by using the type I-E of E. coli [constructed according to Gomaa et al. (2014)]. (F) Schematic showing an example of gene expression control by the type I-E Cascade in E. coli [modified according to Rath et al. (2015)].