title: Processing-independent CRISPR RNAs limit natural transformation in Neisseria meningitidis.
abstract: CRISPR interference confers adaptive, sequence-based immunity against viruses and plasmids and is specified by CRISPR RNAs (crRNAs) that are transcribed and processed from spacer-repeat units. Pre-crRNA processing is essential for CRISPR interference in all systems studied thus far. Here, our studies of crRNA biogenesis and CRISPR interference in naturally competent Neisseria spp. reveal a unique crRNA maturation pathway in which crRNAs are transcribed from promoters that are embedded within each repeat, yielding crRNA 5' ends formed by transcription and not by processing. Although crRNA 3' end formation involves RNase III and trans-encoded tracrRNA, as in other type II CRISPR systems, this processing is dispensable for interference. The meningococcal pathway is the most streamlined CRISPR/Cas system characterized to date. Endogenous CRISPR spacers limit natural transformation, which is the primary source of genetic variation that contributes to immune evasion, antibiotic resistance, and virulence in the human pathogen N. meningitidis.
authors.affiliation: Department of Molecular Biosciences, Northwestern University, 2205 Tech Drive, Evanston, IL 60208-3500, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Nadja
authors.initials: N
authors.lastname: Heidrich
authors.forename: Biju Joseph
authors.initials: BJ
authors.lastname: Ampattu
authors.forename: Carl W
authors.initials: CW
authors.lastname: Gunderson
authors.forename: H Steven
authors.initials: HS
authors.lastname: Seifert
authors.forename: Christoph
authors.initials: C
authors.lastname: Schoen
authors.forename: Jörg
authors.initials: J
authors.lastname: Vogel
authors.forename: Erik J
authors.initials: EJ
authors.lastname: Sontheimer
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D005798:Genes, Bacterial / Q000235:genetics; D054884:Host-Pathogen Interactions; D006801:Humans; D055029:Inverted Repeat Sequences / Q000235:genetics*; D008589:Meningococcal Infections / Q000382:microbiology; D008957:Models, Genetic; D009345:Neisseria meningitidis / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000235:genetics; D012323:RNA Processing, Post-Transcriptional; D012329:RNA, Bacterial / Q000235:genetics* / Q000378:metabolism; D043244:Ribonuclease III / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D014169:Transformation, Bacterial; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D012329:RNA, Bacterial; D043244:Ribonuclease III