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
Affiliations
Yi Zhou
Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, USA
Jack P.K. Bravo
Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, USA
Hannah N. Taylor
Department of Chemistry and Biochemistry, Utah State University, Logan, UT, USA
Jurre A. Steens
Laboratory of Microbiology, Wageningen University and Research, The Netherlands
Ryan N. Jackson
Department of Chemistry and Biochemistry, Utah State University, Logan, UT, USA; Corresponding author
Raymond H.J. Staals
Laboratory of Microbiology, Wageningen University and Research, The Netherlands; Corresponding author
David W. Taylor
Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, USA; Institute for Cell and Molecular Biology, University of Texas at Austin, Austin, TX, USA; Center for Systems and Synthetic Biology, University of Texas at Austin, Austin, TX, USA; LIVESTRONG Cancer Institutes, Dell Medical School, Austin, TX, USA; Corresponding author
Summary: 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.
