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Publication Abstract from PubMed

Type I CRISPR-Cas systems utilize the RNA-guided Cascade complex to identify matching DNA targets and the nuclease-helicase Cas3 to degrade them. Among the seven subtypes, type I-C is compact in size and highly active in creating large-sized genome deletions in human cells. Here, we use four cryoelectron microscopy snapshots to define its RNA-guided DNA binding and cleavage mechanisms in high resolution. The non-target DNA strand (NTS) is accommodated by I-C Cascade in a continuous binding groove along the juxtaposed Cas11 subunits. Binding of Cas3 further traps a flexible bulge in NTS, enabling NTS nicking. We identified two anti-CRISPR proteins AcrIC8 and AcrIC9 that strongly inhibit Neisseria lactamica I-C function. Structural analysis showed that AcrIC8 inhibits PAM recognition through allosteric inhibition, whereas AcrIC9 achieves so through direct competition. Both Acrs potently inhibit I-C-mediated genome editing and transcriptional modulation in human cells, providing the first off-switches for type I CRISPR eukaryotic genome engineering.

Exploiting activation and inactivation mechanisms in type I-C CRISPR-Cas3 for genome-editing applications.,Hu C, Myers MT, Zhou X, Hou Z, Lozen ML, Nam KH, Zhang Y, Ke A Mol Cell. 2024 Feb 1;84(3):463-475.e5. doi: 10.1016/j.molcel.2023.12.034. Epub , 2024 Jan 18. PMID:38242128^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.