@Article{Scholz_Lange_Hein-CRISP_Syste_the-2013,
  author =	 {Scholz, Ingeborg and Lange, Sita J. and Hein, Stephanie and 
                  Hess, Wolfgang R. and Backofen, Rolf},
  title =	 {{CRISPR}-{Cas} {Systems} in the {Cyanobacterium} 
                  {Synechocystis} sp. {PCC6803} {Exhibit} {Distinct} 
                  {Processing} {Pathways} {Involving} at {Least} {Two} {Cas6} 
                  and a {Cmr2} {Protein}},
  journal =	 {PLoS One},
  year =	 {2013},
  volume =	 {8},
  number =	 {2},
  pages =	 {e56470},
  user =	 {sita},
  pmid =	 {23441196},
  doi = 	 {10.1371/journal.pone.0056470},
  note = 	 {IS and SJL contributed equally to this work.},
  issn = 	 {1932-6203},
  abstract =	 {The CRISPR-Cas (Clustered Regularly Interspaced Short 
                  Palindrome Repeats - CRISPR associated proteins) system 
                  provides adaptive immunity in archaea and bacteria. A 
                  hallmark of CRISPR-Cas is the involvement of short crRNAs 
                  that guide associated proteins in the destruction of 
                  invading DNA or RNA. We present three fundamentally distinct 
                  processing pathways in the cyanobacterium Synechocystis sp. 
                  PCC6803 for a subtype I-D (CRISPR1), and two type III 
                  systems (CRISPR2 and CRISPR3), which are located together on 
                  the plasmid pSYSA. Using high-throughput transcriptome 
                  analyses and assays of transcript accumulation we found all 
                  CRISPR loci to be highly expressed, but the individual 
                  crRNAs had profoundly varying abundances despite single 
                  transcription start sites for each array. In a computational 
                  analysis, CRISPR3 spacers with stable secondary structures 
                  displayed a greater ratio of degradation products. These 
                  structures might interfere with the loading of the crRNAs 
                  into RNP complexes, explaining the varying abundancies. The 
                  maturation of CRISPR1 and CRISPR2 transcripts depends on at 
                  least two different Cas6 proteins. Mutation of gene sll7090, 
                  encoding a Cmr2 protein led to the disappearance of all 
                  CRISPR3-derived crRNAs, providing in vivo evidence for a 
                  function of Cmr2 in the maturation, regulation of 
                  expression, Cmr complex formation or stabilization of 
                  CRISPR3 transcripts. Finally, we optimized CRISPR repeat 
                  structure prediction and the results indicate that the 
                  spacer context can influence individual repeat structures.}
}