@Article{Maier_Lange_Stoll-Essen_requi_for-2013,
  author =	 {Maier, Lisa-Katharina and Lange, Sita J. and Stoll, Britta 
                  and Haas, Karina A. and Fischer, Susan and Fischer, Eike and 
                  Duchardt-Ferner, Elke and Wohnert, Jens and Backofen, Rolf 
                  and Marchfelder, Anita},
  title =	 {Essential requirements for the detection and degradation of 
                  invaders by the {Haloferax} volcanii {CRISPR}/{Cas} system 
                  {I}-{B}},
  journal =	 {RNA Biology},
  year =	 {2013},
  volume =	 {10},
  number =	 {5},
  pages =	 {865-874},
  doi = 	 {10.4161/rna.24282},
  user =	 {sita},
  pmid =	 {23594992},
  issn = 	 {1547-6286},
  issn = 	 {1555-8584},
  abstract =	 {To fend off foreign genetic elements, prokaryotes have 
                  developed several defense systems. The most recently 
                  discovered defense system, CRISPR/Cas, is sequence-specific, 
                  adaptive and heritable. The two central components of this 
                  system are the Cas proteins and the CRISPR RNA. The latter 
                  consists of repeat sequences that are interspersed with 
                  spacer sequences. The CRISPR locus is transcribed into a 
                  precursor RNA that is subsequently processed into short 
                  crRNAs. CRISPR/Cas systems have been identified in bacteria 
                  and archaea, and data show that many variations of this 
                  system exist. We analyzed the requirements for a successful 
                  defense reaction in the halophilic archaeon Haloferax 
                  volcanii. Haloferax encodes a CRISPR/Cas system of the I-B 
                  subtype, about which very little is known. Analysis of the 
                  mature crRNAs revealed that they contain a spacer as their 
                  central element, which is preceded by an 
                  eight-nucleotide-long 5' handle that originates from the 
                  upstream repeat. The repeat sequences have the potential to 
                  fold into a minimal stem loop. Sequencing of the crRNA 
                  population indicated that not all of the spacers that are 
                  encoded by the three CRISPR loci are present in the same 
                  abundance. By challenging Haloferax with an invader plasmid, 
                  we demonstrated that the interaction of the crRNA with the 
                  invader DNA requires a 10-nucleotide-long seed sequence. In 
                  addition, we found that not all of the crRNAs from the three 
                  CRISPR loci are effective at triggering the degradation of 
                  invader plasmids. The interference does not seem to be 
                  influenced by the copy number of the invader plasmid.}
}