title: Interaction of the Cas6 riboendonuclease with CRISPR RNAs: recognition and cleavage.
abstract: The CRISPRs (Clustered Regularly Interspaced Short Palindromic Repeats) found in prokaryotic genomes confer small RNA-mediated protection against viruses and other invaders. CRISPR loci contain iterations of a short repeat sequence alternating with small segments of varying invader-derived sequences. Distinct families of CRISPR-associated Cas proteins function to cleave within the repeat sequence of CRISPR transcripts and produce the individual invader-targeting crRNAs. Here, we report the crystal structure of Pyrococcus furiosus Cas6 bound with a repeat RNA at 3.2 Å resolution. In contrast to other Cas families of endonucleases, Cas6 clasps nucleotides 2-9 of the repeat RNA using its two ferredoxin-like domains, and the enzyme-anchored 5' end tethers the distal cleavage site of the RNA between nucleotides 22 and 23 to the predicted enzyme active site on the opposite side of the ferrodoxin-like domains. Our findings suggest a wrap-around mechanism for CRISPR RNA recognition and cleavage by Cas6 and related processing endonucleases.
authors.affiliation: Department of Chemistry and Biochemistry and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA.
authors.forename: Ruiying
authors.initials: R
authors.lastname: Wang
authors.forename: Gan
authors.initials: G
authors.lastname: Preamplume
authors.forename: Michael P
authors.initials: MP
authors.lastname: Terns
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Terns
authors.forename: Hong
authors.initials: H
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D004720:Endonucleases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D055029:Inverted Repeat Sequences; D056265:Microbial Interactions; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D009711:Nucleotides / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary; D020027:Pyrococcus furiosus / Q000201:enzymology* / Q000235:genetics; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D009711:Nucleotides; D012329:RNA, Bacterial; D004720:Endonucleases