Structure of a type IV CRISPR-Cas ribonucleoprotein complex

Yi Zhou; Jack P K Bravo; Hannah N Taylor; Jurre A Steens; Ryan N Jackson; Raymond H J Staals; David W Taylor

doi:10.1016/j.isci.2021.102201

Structure of a type IV CRISPR-Cas ribonucleoprotein complex

iScience. 2021 Feb 17;24(3):102201. doi: 10.1016/j.isci.2021.102201. eCollection 2021 Mar 19.

Authors

Yi Zhou¹, Jack P K Bravo¹, Hannah N Taylor², Jurre A Steens³, Ryan N Jackson², Raymond H J Staals³, David W Taylor^{1

4

5

6}

Affiliations

¹ Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, USA.
² Department of Chemistry and Biochemistry, Utah State University, Logan, UT, USA.
³ Laboratory of Microbiology, Wageningen University and Research, The Netherlands.
⁴ Institute for Cell and Molecular Biology, University of Texas at Austin, Austin, TX, USA.
⁵ Center for Systems and Synthetic Biology, University of Texas at Austin, Austin, TX, USA.
⁶ LIVESTRONG Cancer Institutes, Dell Medical School, Austin, TX, USA.

Abstract

We reveal the cryo-electron microscopy structure of a type IV-B CRISPR ribonucleoprotein (RNP) complex (Csf) at 3.9-Å resolution. The complex best resembles the type III-A CRISPR Csm effector complex, consisting of a Cas7-like (Csf2) filament intertwined with a small subunit (Cas11) filament, but the complex lacks subunits for RNA processing and target DNA cleavage. Surprisingly, instead of assembling around a CRISPR-derived RNA (crRNA), the complex assembles upon heterogeneous RNA of a regular length arranged in a pseudo-A-form configuration. These findings provide a high-resolution glimpse into the assembly and function of enigmatic type IV CRISPR systems, expanding our understanding of class I CRISPR-Cas system architecture, and suggesting a function for type IV-B RNPs that may be distinct from other class 1 CRISPR-associated systems.

Keywords: Biological Sciences; Structural Biology.

Abstract

Grants and funding