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Structural basis for the type I-F Cas8-HNH system.
- Source :
-
The EMBO journal [EMBO J] 2024 Sep 09. Date of Electronic Publication: 2024 Sep 09. - Publication Year :
- 2024
- Publisher :
- Ahead of Print
-
Abstract
- The Cas3 nuclease is utilized by canonical type I CRISPR-Cas systems for processive target DNA degradation, while a newly identified type I-F CRISPR variant employs an HNH nuclease domain from the natural fusion Cas8-HNH protein for precise target cleavage both in vitro and in human cells. Here, we report multiple cryo-electron microscopy structures of the type I-F Cas8-HNH system at different functional states. The Cas8-HNH Cascade complex adopts an overall G-shaped architecture, with the HNH domain occupying the C-terminal helical bundle domain (HB) of the Cas8 protein in canonical type I systems. The Linker region connecting Cas8-NTD and HNH domains adopts a rigid conformation and interacts with the Cas7.6 subunit, enabling the HNH domain to be in a functional position. The full R-loop formation displaces the HNH domain away from the Cas6 subunit, thus activating the target DNA cleavage. Importantly, our results demonstrate that precise target cleavage is dictated by a C-terminal helix of the HNH domain. Together, our work not only delineates the structural basis for target recognition and activation of the type I-F Cas8-HNH system, but also guides further developments leveraging this system for precise DNA editing.<br /> (© 2024. The Author(s).)
Details
- Language :
- English
- ISSN :
- 1460-2075
- Database :
- MEDLINE
- Journal :
- The EMBO journal
- Publication Type :
- Academic Journal
- Accession number :
- 39251884
- Full Text :
- https://doi.org/10.1038/s44318-024-00229-8