@Article{Maier_Stachler_Saunders-activ_immun_defen-JBC2015,
  author =	 {Maier, Lisa-Katharina and Stachler, Aris-Edda and Saunders, 
                  Sita J. and Backofen, Rolf and Marchfelder, Anita},
  title =	 {An active immune defense with a minimal {CRISPR} (clustered 
                  regularly interspaced short palindromic repeats) {RNA} and 
                  without the {Cas6} protein},
  journal =	 JBC,
  year =	 {2015},
  volume =	 {290},
  number =	 {7},
  pages =	 {4192-201},
  user =	 {backofen},
  pmid =	 {25512373},
  doi = 	 {10.1074/jbc.M114.617506},
  issn = 	 {0021-9258},
  issn = 	 {1083-351X},
  abstract =	 {The prokaryotic immune system CRISPR-Cas (clustered 
                  regularly interspaced short palindromic 
                  repeats-CRISPR-associated) is a defense system that protects 
                  prokaryotes against foreign DNA. The short CRISPR RNAs 
                  (crRNAs) are central components of this immune system. In 
                  CRISPR-Cas systems type I and III, crRNAs are generated by 
                  the endonuclease Cas6. We developed a Cas6b-independent 
                  crRNA maturation pathway for the Haloferax type I-B system 
                  in vivo that expresses a functional crRNA, which we termed 
                  independently generated crRNA (icrRNA). The icrRNA is 
                  effective in triggering degradation of an invader plasmid 
                  carrying the matching protospacer sequence. The 
                  Cas6b-independent maturation of the icrRNA allowed mutation 
                  of the repeat sequence without interfering with signals 
                  important for Cas6b processing. We generated 23 variants of 
                  the icrRNA and analyzed them for activity in the 
                  interference reaction. icrRNAs with deletions or mutations 
                  of the 3' handle are still active in triggering an 
                  interference reaction. The complete 3' handle could be 
                  removed without loss of activity. However, manipulations of 
                  the 5' handle mostly led to loss of interference activity. 
                  Furthermore, we could show that in the presence of an icrRNA 
                  a strain without Cas6b (Deltacas6b) is still active in 
                  interference.}
}