title: Cas5d processes pre-crRNA and is a member of a larger family of CRISPR RNA endonucleases.
abstract: Small RNAs derived from clustered, regularly interspaced, short palindromic repeat (CRISPR) loci in bacteria and archaea are involved in an adaptable and heritable gene-silencing pathway. Resistance to invasive genetic material is conferred by the incorporation of short DNA sequences derived from this material into the genome as CRISPR spacer elements separated by short repeat sequences. Processing of long primary transcripts (pre-crRNAs) containing these repeats by a CRISPR-associated (Cas) RNA endonuclease generates the mature effector RNAs that target foreign nucleic acid for degradation. Here we describe functional studies of a Cas5d ortholog, and high-resolution structural studies of a second Cas5d family member, demonstrating that Cas5d is a sequence-specific RNA endonuclease that cleaves CRISPR repeats and is thus responsible for processing of pre-crRNA. Analysis of the structural homology of Cas5d with the previously characterized Cse3 protein allows us to model the interaction of Cas5d with its RNA substrate and conclude that it is a member of a larger family of CRISPR RNA endonucleases.
authors.affiliation: Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
authors.forename: Erin L
authors.initials: EL
authors.lastname: Garside
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Schellenberg
authors.forename: Emily M
authors.initials: EM
authors.lastname: Gesner
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Bonanno
authors.forename: J Michael
authors.initials: JM
authors.lastname: Sauder
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Burley
authors.forename: Steven C
authors.initials: SC
authors.lastname: Almo
authors.forename: Garima
authors.initials: G
authors.lastname: Mehta
authors.forename: Andrew M
authors.initials: AM
authors.lastname: MacMillan
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D024202:Electrophoretic Mobility Shift Assay; D004722:Endoribonucleases / Q000737:chemistry*; D031121:Mannheimia / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D017433:Protein Structure, Secondary; D059367:RNA Cleavage; D012322:RNA Precursors / Q000737:chemistry*; D012091:Repetitive Sequences, Nucleic Acid; D040681:Structural Homology, Protein; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D012322:RNA Precursors; D004722:Endoribonucleases