1. Structural determinants of DNA cleavage by a CRISPR HNH-Cascade system.
- Author
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Hirano S, Altae-Tran H, Kannan S, Macrae RK, and Zhang F
- Subjects
- Bacterial Proteins genetics, Bacterial Proteins metabolism, Bacterial Proteins chemistry, Models, Molecular, DNA metabolism, DNA genetics, DNA chemistry, Protein Domains, DNA, Bacterial genetics, DNA, Bacterial metabolism, Structure-Activity Relationship, Clustered Regularly Interspaced Short Palindromic Repeats, Protein Binding, CRISPR-Cas Systems, Cryoelectron Microscopy, DNA Cleavage, CRISPR-Associated Proteins metabolism, CRISPR-Associated Proteins chemistry, CRISPR-Associated Proteins genetics
- Abstract
Canonical prokaryotic type I CRISPR-Cas adaptive immune systems contain a multicomponent effector complex called Cascade, which degrades large stretches of DNA via Cas3 helicase-nuclease activity. Recently, a highly precise subtype I-F1 CRISPR-Cas system (HNH-Cascade) was found that lacks Cas3, the absence of which is compensated for by the insertion of an HNH endonuclease domain in the Cas8 Cascade component. Here, we describe the cryo-EM structure of Selenomonas sp. HNH-Cascade (SsCascade) in complex with target DNA and characterize its mechanism of action. The Cascade scaffold is complemented by the HNH domain, creating a ring-like structure in which the unwound target DNA is precisely cleaved. This structure visualizes a unique hybrid of two extensible biological systems-Cascade, an evolutionary platform for programmable DNA effectors, and an HNH nuclease, an adaptive domain with a spectrum of enzymatic activity., Competing Interests: Declaration of interests S.H., H.A.-T., and F.Z. are coinventors on a patent application (PCT/US2023/070150) related to this work filed by the Broad Institute and MIT. F.Z. is a scientific advisor and cofounder of Editas Medicine, Beam Therapeutics, Pairwise Plants, Arbor Biotechnologies, Aera Therapeutics, and Moonwalk Biosciences. F.Z. is a scientific advisor for Octant., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2024
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