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Science 15 August 2008:
Vol. 321. no. 5891, pp. 960 - 964
DOI: 10.1126/science.1159689
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Reports

Small CRISPR RNAs Guide Antiviral Defense in Prokaryotes

Stan J. J. Brouns,1* Matthijs M. Jore,1* Magnus Lundgren,1 Edze R. Westra,1 Rik J. H. Slijkhuis,1 Ambrosius P. L. Snijders,2 Mark J. Dickman,2 Kira S. Makarova,3 Eugene V. Koonin,3 John van der Oost1{dagger}

Prokaryotes acquire virus resistance by integrating short fragments of viral nucleic acid into clusters of regularly interspaced short palindromic repeats (CRISPRs). Here we show how virus-derived sequences contained in CRISPRs are used by CRISPR-associated (Cas) proteins from the host to mediate an antiviral response that counteracts infection. After transcription of the CRISPR, a complex of Cas proteins termed Cascade cleaves a CRISPR RNA precursor in each repeat and retains the cleavage products containing the virus-derived sequence. Assisted by the helicase Cas3, these mature CRISPR RNAs then serve as small guide RNAs that enable Cascade to interfere with virus proliferation. Our results demonstrate that the formation of mature guide RNAs by the CRISPR RNA endonuclease subunit of Cascade is a mechanistic requirement for antiviral defense.

1 Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Dreijenplein 10, 6703 HB Wageningen, Netherlands.
2 Biological and Environmental Systems, Department of Chemical and Process Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, UK.
3 National Center for Biotechnology Information, National Library of Medicine, NIH, Bethesda, MD 20894, USA.

* These authors contributed equally to this work.

{dagger} To whom correspondence should be addressed. E-mail: john.vanderoost{at}wur.nl

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
A diversity of uncharacterized reverse transcriptases in bacteria.
D. M. Simon and S. Zimmerly (2008)
Nucleic Acids Res.
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Science. ISSN 0036-8075 (print), 1095-9203 (online)