Structural determinants of DNA cleavage by a CRISPR HNH-Cascade system.

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 ev

SUBMITTER: Hirano S 

PROVIDER: S-EPMC11459484 | biostudies-literature | 2024 Aug

REPOSITORIES: biostudies-literature