Structural basis for assembly of non-canonical small subunits into type I-C Cascade
Abstract
Bacteria and archaea employ CRISPR (clustered, regularly, interspaced, short palindromic repeats)-Cas (CRISPR-associated) systems as a type of adaptive immunity to target and degrade foreign nucleic acids. While a myriad of CRISPR-Cas systems have been identified to date, type I-C is one of the most commonly found subtypes in nature. Interestingly, the type I-C system employs a minimal Cascade effector complex, which encodes only three unique subunits in its operon. Here, we present a 3.1 Å resolution cryo-EM structure of the Desulfovibrio vulgaris type I-C Cascade, revealing the molecular mechanisms that underlie RNA-directed complex assembly. We demonstrate how this minimal Cascade utilizes previously overlooked, non-canonical small subunits to stabilize R-loop formation. Furthermore, we describe putative PAM and Cas3 binding sites. These findings provide the structural basis for harnessing the type I-C Cascade as a genome-engineering tool.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Nov 23, 2020
- Source ID
- 10.1038/s41467-020-19785-8
Entities
People
- Daniel Wrapp
- David W Taylor
- Evan A. Schwartz
- Inês C. Santos
- Jack P. K. Bravo
- Jennifer S. Brodbelt
- Roisin E. O’brien
Organizations
- Army Research Office
- Cancer Prevention and Research Institute of Texas
- Robert A. Welch Foundation