Figure 3.

The stages of a viral life cycle inhibited by CRISPR-based targeting

Cas9, orange-shaded object; Cas13, blue-shaded object; black triangles, cleavage; blue and green lines, DNA; gray lines and curves, RNA; red line, indel. Cas9 and Cas13 inhibit viral replication through the specific targeting of either the viral genome or replication intermediates. Cas9 directly targets (1) dsDNA genomes or (2) integrated viruses. Cas13 targets (3) ssRNA viral genomes or any ssRNA intermediate created during the life cycle of either RNA or DNA viruses, such as (4) viral mRNAs. All targeting activity occurs within the cell once the nucleic acid is accessible to Cas9-sgRNA or Cas13-crRNA complexes and can result in disrupted viral release.