title: Structure of an RNA silencing complex of the CRISPR-Cas immune system.
abstract: Bacterial and archaeal clustered regularly interspaced short palindromic repeat (CRISPR) loci capture virus and plasmid sequences and use them to recognize and eliminate these invaders. CRISPR RNAs (crRNAs) containing the acquired sequences are incorporated into effector complexes that destroy matching invader nucleic acids. The multicomponent Cmr effector complex cleaves RNA targets complementary to the crRNAs. Here, we report cryoelectron microscopy reconstruction of a functional Cmr complex bound with a target RNA at ~12 Å. Pairs of the Cmr4 and Cmr5 proteins form a helical core that is asymmetrically capped on each end by distinct pairs of the four remaining subunits: Cmr2 and Cmr3 at the conserved 5' crRNA tag sequence and Cmr1 and Cmr6 near the 3' end of the crRNA. The shape and organization of the RNA-targeting Cmr complex is strikingly similar to the DNA-targeting Cascade complex. Our results reveal a remarkably conserved architecture among very distantly related CRISPR-Cas complexes.
authors.affiliation: Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Spilman
authors.forename: Alexis
authors.initials: A
authors.lastname: Cocozaki
authors.forename: Caryn
authors.initials: C
authors.lastname: Hale
authors.forename: Yaming
authors.initials: Y
authors.lastname: Shao
authors.forename: Nancy
authors.initials: N
authors.lastname: Ramia
authors.forename: Rebeca
authors.initials: R
authors.lastname: Terns
authors.forename: Michael
authors.initials: M
authors.lastname: Terns
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.forename: Scott
authors.initials: S
authors.lastname: Stagg
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D064130:CRISPR-Associated Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D064112:Clustered Regularly Interspaced Short Palindromic Repeats; D020285:Cryoelectron Microscopy; D019848:Gene Expression Regulation, Archaeal; D008958:Models, Molecular; D011487:Protein Conformation; D021122:Protein Subunits; D020027:Pyrococcus furiosus / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D034622:RNA Interference; D019642:RNA, Archaeal / Q000235:genetics / Q000378:metabolism*; D012260:Ribonucleases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D019843:Archaeal Proteins; D064130:CRISPR-Associated Proteins; D021122:Protein Subunits; D019642:RNA, Archaeal; D012260:Ribonucleases