  Type I CRISPR-Cas systems are the most common among six types of CRISPR-Cas
systems, however, non-self-targeting genome editing based on a single Cas3 of
type I CRISPR-Cas systems has not been reported. Here, we present the subtype
I-B-Svi CRISPR-Cas system (with three confirmed CRISPRs and a cas gene cluster)
and genome editing based on this system found in Streptomyces virginiae IBL14.
Importantly, like the animal-derived bacterial protein SpCas9 (1368
amino-acids), the single, compact, non-animal-derived bacterial protein SviCas3
(771 amino-acids) can also direct template-based microbial genome editing
through the target cell's own homology-directed repair system, which breaks the
view that the genome editing based on type I CRISPR-Cas systems requires a full
Cascade. Notably, no off-target changes or indel-formation were detected in the
analysis of potential off-target sites. This discovery broadens our
understanding of the diversity of type I CRISPR-Cas systems and will facilitate
new developments in genome editing tools.
