@article{Hou_Brenes-Alvarez_Reimann-CRISP_syste_multi-2019,
author = {Hou, Shengwei and Brenes-Alvarez, Manuel and Reimann, 
          Viktoria and Alkhnbashi, Omer S. and Backofen, Rolf and 
          Muro-Pastor, Alicia M. and Hess, Wolfgang R.},
title = {{CRISPR}-{Cas} systems in multicellular cyanobacteria},
journal = {RNA Biol},
year = {2019},
doi = {10.1080/15476286.2018.1493330},
volume = {16},
user = {backofen},
pmid = {29995583},
pages = {518-529},
number = {4},
issn = {1555-8584},
abstract = {Novel CRISPR-Cas systems possess substantial potential for 
            genome editing and manipulation of gene expression. The 
            types and numbers of CRISPR-Cas systems vary substantially 
            between different organisms. Some filamentous cyanobacteria 
            harbor > 40 different putative CRISPR repeat-spacer 
            cassettes, while the number of cas gene instances is much 
            lower. Here we addressed the types and diversity of 
            CRISPR-Cas systems and of CRISPR-like repeat-spacer arrays 
            in 171 publicly available genomes of multicellular 
            cyanobacteria. The number of 1328 repeat-spacer arrays 
            exceeded the total of 391 encoded Cas1 proteins suggesting a 
            tendency for fragmentation or the involvement of alternative 
            adaptation factors. The model cyanobacterium Anabaena sp. 
            PCC 7120 contains only three cas1 genes but hosts three 
            Class 1, possibly one Class 2 and five orphan repeat-spacer 
            arrays, all of which exhibit crRNA-typical expression 
            patterns suggesting active transcription, maturation and 
            incorporation into CRISPR complexes. The CRISPR-Cas system 
            within the element interrupting the Anabaena sp. PCC 7120 
            fdxN gene, as well as analogous arrangements in other 
            strains, occupy the genetic elements that become excised 
            during the differentiation-related programmed site-specific 
            recombination. This fact indicates the propensity of these 
            elements for the integration of CRISPR-cas systems and 
            points to a previously not recognized connection. The gene 
            all3613 resembling a possible Class 2 effector protein is 
            linked to a short repeat-spacer array and a single tRNA 
            gene, similar to its homologs in other cyanobacteria. The 
            diversity and presence of numerous CRISPR-Cas systems in DNA 
            elements that are programmed for homologous recombination 
            make filamentous cyanobacteria a prolific resource for their 
            study. Abbreviations: Cas: CRISPR associated sequences; 
            CRISPR: Clustered Regularly Interspaced Short Palindromic 
            Repeats; C2c: Class 2 candidate; SDR: small dispersed 
            repeat; TSS: transcriptional start site; UTR: untranslated 
            region.}
}