Structure Reveals Mechanisms of Viral Suppressors that Intercept a CRISPR RNA-Guided Surveillance Complex.
Genetic conflict between viruses and their hosts drives evolution and genetic innovation. Prokaryotes evolved CRISPR-mediated adaptive immune systems for protection from viral infection, and viruses have evolved diverse anti-CRISPR (Acr) proteins that subvert these immune systems. The adaptive immune system in Pseudomonas aeruginosa (type I-F) relies on a 350 kDa CRISPR RNA (crRNA)-guided surveillance complex (Csy complex) to bind foreign DNA and recruit a trans-acting nuclease for target degradation. Here, we report the cryo-electron microscopy (cryo-EM) structure of the Csy complex bound to two different Acr proteins, AcrF1 and AcrF2, at an average resolution of 3.4 Å. The structure explains the molecular mechanism for immune system suppression, and structure-guided mutations show that the Acr proteins bind to residues essential for crRNA-mediated detection of DNA. Collectively, these data provide a snapshot of an ongoing molecular arms race between viral suppressors and the immune system they target.
Department of Integrative Structural and Computational Biology, Scripps Research Institute, La Jolla, CA 92037, USA.
Saikat
S
Chowdhury
Department of Microbiology and Immunology, Montana State University, Bozeman, MT 59717, USA.
Joshua
J
Carter
Department of Microbiology and Immunology, Montana State University, Bozeman, MT 59717, USA.
MaryClare F
MF
Rollins
Department of Microbiology and Immunology, Montana State University, Bozeman, MT 59717, USA.
Sarah M
SM
Golden
Department of Microbiology and Immunology, Montana State University, Bozeman, MT 59717, USA.
Ryan N
RN
Jackson
Department of Microbiology and Immunology, Montana State University, Bozeman, MT 59717, USA.
Connor
C
Hoffmann
Department of Integrative Structural and Computational Biology, Scripps Research Institute, La Jolla, CA 92037, USA.
Lyn'Al
L
Nosaka
Department of Microbiology and Immunology, University of California San Francisco, San Francisco, CA 94158, USA.
Joseph
J
Bondy-Denomy
Department of Biochemistry, University of Toronto, Toronto, ON, Canada.
Karen L
KL
Maxwell
Department of Biochemistry, University of Toronto, Toronto, ON, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada.
Alan R
AR
Davidson
Research Technologies Branch, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, NIH, Hamilton, MT 59840, USA.
Elizabeth R
ER
Fischer
Department of Integrative Structural and Computational Biology, Scripps Research Institute, La Jolla, CA 92037, USA. Electronic address: glander@scripps.edu.
Gabriel C
GC
Lander
Department of Microbiology and Immunology, Montana State University, Bozeman, MT 59717, USA. Electronic address: bwiedenheft@gmail.com.
Blake
B
Wiedenheft
D001435:Bacteriophages / Q000737:chemistry* / Q000145:classification / Q000235:genetics; D064130:CRISPR-Associated Proteins / Q000737:chemistry*; D064112:Clustered Regularly Interspaced Short Palindromic Repeats; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D007157:Immunologic Surveillance; D008958:Models, Molecular; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000276:immunology* / Q000821:virology*; D012329:RNA, Bacterial / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D014764:Viral Proteins / Q000737:chemistry* / Q000648:ultrastructure
D064130:CRISPR-Associated Proteins; D012329:RNA, Bacterial; D014764:Viral Proteins
Acr; CRISPR; CRISPR-Cas; Cas; Csy; anti-CRISPRs; crRNA; cryo-EM; cryo-electron microscopy; type I-F