title: An archaeal immune system can detect multiple protospacer adjacent motifs (PAMs) to target invader DNA.
abstract: The clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated (Cas) system provides adaptive and heritable immunity against foreign genetic elements in most archaea and many bacteria. Although this system is widespread and diverse with many subtypes, only a few species have been investigated to elucidate the precise mechanisms for the defense of viruses or plasmids. Approximately 90% of all sequenced archaea encode CRISPR/Cas systems, but their molecular details have so far only been examined in three archaeal species: Sulfolobus solfataricus, Sulfolobus islandicus, and Pyrococcus furiosus. Here, we analyzed the CRISPR/Cas system of Haloferax volcanii using a plasmid-based invader assay. Haloferax encodes a type I-B CRISPR/Cas system with eight Cas proteins and three CRISPR loci for which the identity of protospacer adjacent motifs (PAMs) was unknown until now. We identified six different PAM sequences that are required upstream of the protospacer to permit target DNA recognition. This is only the second archaeon for which PAM sequences have been determined, and the first CRISPR group with such a high number of PAM sequences. Cells could survive the plasmid challenge if their CRISPR/Cas system was altered or defective, e.g. by deletion of the cas gene cassette. Experimental PAM data were supplemented with bioinformatics data on Haloferax and Haloquadratum.
authors: Department of Biology II, Ulm University, 89069 Ulm, Germany.
authors: Susan
authors: S
authors: Fischer
authors: Lisa-Katharina
authors: LK
authors: Maier
authors: Britta
authors: B
authors: Stoll
authors: Jutta
authors: J
authors: Brendel
authors: Eike
authors: E
authors: Fischer
authors: Friedhelm
authors: F
authors: Pfeiffer
authors: Mike
authors: M
authors: Dyall-Smith
authors: Anita
authors: A
authors: Marchfelder
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001105:Archaea / Q000378:metabolism; D001483:Base Sequence; D019295:Computational Biology / Q000379:methods; D004247:DNA / Q000737:chemistry*; D019621:Haloferax / Q000276:immunology* / Q000378:metabolism*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D009696:Nucleic Acids / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D019711:Pyrococcus / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D016944:Sulfolobus / Q000276:immunology* / Q000378:metabolism*
chemical_list: D009696:Nucleic Acids; D012313:RNA; D004247:DNA