@Article{Nickel_Weidenbach_Jager-Two_CRISP_syste-2013,
  author =	 {Nickel, Lisa and Weidenbach, Katrin and Jager, Dominik and 
                  Backofen, Rolf and Lange, Sita J. and Heidrich, Nadja and 
                  Schmitz, Ruth A.},
  title =	 {Two {CRISPR}-{Cas} systems in {Methanosarcina} mazei strain 
                  {Go1} display common processing features despite belonging 
                  to different types {I} and {III}},
  journal =	 {RNA Biol},
  year =	 {2013},
  volume =	 {10},
  number =	 {5},
  pages =	 {779-791},
  doi = 	 {10.4161/rna.23928},
  user =	 {sita},
  pmid =	 {23619576},
  issn = 	 {1547-6286},
  issn = 	 {1555-8584},
  abstract =	 {The clustered regularly interspaced short palindromic 
                  repeats (CRISPR) system represents a highly adaptive and 
                  heritable defense system against foreign nucleic acids in 
                  bacteria and archaea. We analyzed the two CRISPR-Cas systems 
                  in Methanosarcina mazei strain Go1. Although belonging to 
                  different subtypes (I-B and III-B), the leaders and repeats 
                  of both loci are nearly identical. Also, despite many point 
                  mutations in each array, a common hairpin motif was 
                  identified in the repeats by a bioinformatics analysis and 
                  in vitro structural probing. The expression and maturation 
                  of CRISPR-derived RNAs (crRNAs) were studied in vitro and in 
                  vivo. Both respective potential Cas6b-type endonucleases 
                  were purified and their activity tested in vitro. Each 
                  protein showed significant activity and could cleave both 
                  repeats at the same processing site. Cas6b of subtype III-B, 
                  however, was significantly more efficient in its cleavage 
                  activity compared with Cas6b of subtype I-B. Northern blot 
                  and differential RNaseq analyses were performed to 
                  investigate in vivo transcription and maturation of crRNAs, 
                  revealing generally very low expression of both systems, 
                  whereas significant induction at high NaCl concentrations 
                  was observed. crRNAs derived proximal to the leader were 
                  generally more abundant than distal ones and in vivo 
                  processing sites were clarified for both loci, confirming 
                  the previously well-established 8 nt 5' repeat tags. The 
                  3'-ends were more diverse, but generally ended in a prefix 
                  of the following repeat sequence (3'-tag). The analysis 
                  further revealed a 5'-hydroxy and 3'-phosphate termini 
                  architecture of small crRNAs specific for cleavage products 
                  of Cas6 endonucleases from type I-E and I-F and type III-B.}
}