Summary information and primary citation
- PDB-id
-
8yh9;
SNAP-derived features in text and
JSON formats
- Class
- RNA binding protein-RNA
- Method
- cryo-EM (3.35 Å)
- Summary
- Type i-fhnh cascade complex
- Reference
-
Zhang C, Chen F, Wang F, Xu H, Xue J, Li Z (2024):
"Mechanisms
for HNH-mediated target DNA cleavage in type I CRISPR-Cas
systems." Mol.Cell, 84,
3141. doi: 10.1016/j.molcel.2024.06.033.
- Abstract
- The metagenome-derived type I-E and type I-F variant
CRISPR-associated complex for antiviral defense (Cascade)
complexes, fused with HNH domains, precisely cleave target
DNA, representing recently identified genome editing tools.
However, the underlying working mechanisms remain unknown.
Here, structures of type I-F<sub>HNH</sub> and
I-E<sub>HNH</sub> Cascade complexes at
different states are reported. In type
I-F<sub>HNH</sub> Cascade,
Cas8f<sub>HNH</sub> loosely attaches to Cascade
head and is adjacent to the 5' end of the target
single-stranded DNA (ssDNA). Formation of the full R-loop
drives the Cascade head to move outward, allowing
Cas8f<sub>HNH</sub> to detach and rotate ∼150°
to accommodate target ssDNA for cleavage. In type
I-E<sub>HNH</sub> Cascade,
Cas5e<sub>HNH</sub> domain is adjacent to the
5' end of the target ssDNA. Full crRNA-target pairing
drives the lift of the Cascade head, widening the substrate
channel for target ssDNA entrance. Altogether, these
analyses into both complexes revealed that crRNA-guided
positioning of target DNA and target DNA-induced HNH
unlocking are two key factors for their site-specific
cleavage of target DNA.
