@article{Nickel_Ulbricht_Alkhnbashi-Cross_activ_Cas-2019,
author = {Nickel, Lisa and Ulbricht, Andrea and Alkhnbashi, Omer S. 
          and Forstner, Konrad U. and Cassidy, Liam and Weidenbach, 
          Katrin and Backofen, Rolf and Schmitz, Ruth A.},
title = {Cross-cleavage activity of {Cas6b} in {crRNA} processing of 
         two different {CRISPR}-{Cas} systems in {Methanosarcina} 
         mazei {Go1}},
journal = {RNA Biol},
year = {2019},
doi = {10.1080/15476286.2018.1514234},
volume = {16},
user = {alkhanbo},
pmid = {30153081},
pages = {492-503},
number = {4},
issn = {1547-6286},
abstract = {The clustered regularly interspaced short palindromic 
            repeat (CRISPR) system is a prokaryotic adaptive defense 
            system against foreign nucleic acids. In the methanoarchaeon 
            Methanosarcina mazei Go1, two types of CRISPR-Cas systems 
            are present (type I-B and type III-C). Both loci encode a 
            Cas6 endonuclease, Cas6b-IB and Cas6b-IIIC, typically 
            responsible for maturation of functional short CRISPR RNAs 
            (crRNAs). To evaluate potential cross cleavage activity, we 
            biochemically characterized both Cas6b proteins regarding 
            their crRNA binding behavior and their ability to process 
            pre-crRNA from the respective CRISPR array in vivo. 
            Maturation of crRNA was studied in the respective single 
            deletion mutants by northern blot and RNA-Seq analysis 
            demonstrating that in vivo primarily Cas6b-IB is responsible 
            for crRNA processing of both CRISPR arrays. Tentative 
            protein level evidence for the translation of both Cas6b 
            proteins under standard growth conditions was detected, 
            arguing for different activities or a potential 
            non-redundant role of Cas6b-IIIC within the cell. 
            Conservation of both Cas6 endonucleases was observed in 
            several other M. mazei isolates, though a wide variety was 
            displayed. In general, repeat and leader sequence 
            conservation revealed a close correlation in the M. mazei 
            strains. The repeat sequences from both CRISPR arrays from 
            M. mazei Go1 contain the same sequence motif with 
            differences only in two nucleotides. These data stand in 
            contrast to all other analyzed M. mazei isolates, which have 
            at least one additional CRISPR array with repeats belonging 
            to another sequence motif. This conforms to the finding that 
            Cas6b-IB is the crucial and functional endonuclease in M. 
            mazei Go1. Abbreviations: sRNA: small RNA; crRNA: CRISPR 
            RNA; pre-crRNAs: Precursor CRISPR RNA; CRISPR: clustered 
            regularly interspaced short palindromic repeats; Cas: CRISPR 
            associated; nt: nucleotide; RNP: ribonucleoprotein; RBS: 
            ribosome binding site.}
}