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  • 1
    Publication Date: 2014-02-18
    Description: RNA interference is widely distributed in eukaryotes and has a variety of functions, including antiviral defence and gene regulation. All RNA interference pathways use small single-stranded RNA (ssRNA) molecules that guide proteins of the Argonaute (Ago) family to complementary ssRNA targets: RNA-guided RNA interference. The role of prokaryotic Ago variants has remained elusive, although bioinformatics analysis has suggested their involvement in host defence. Here we demonstrate that Ago of the bacterium Thermus thermophilus (TtAgo) acts as a barrier for the uptake and propagation of foreign DNA. In vivo, TtAgo is loaded with 5'-phosphorylated DNA guides, 13-25 nucleotides in length, that are mostly plasmid derived and have a strong bias for a 5'-end deoxycytidine. These small interfering DNAs guide TtAgo to cleave complementary DNA strands. Hence, despite structural homology to its eukaryotic counterparts, TtAgo functions in host defence by DNA-guided DNA interference.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4697943/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4697943/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Swarts, Daan C -- Jore, Matthijs M -- Westra, Edze R -- Zhu, Yifan -- Janssen, Jorijn H -- Snijders, Ambrosius P -- Wang, Yanli -- Patel, Dinshaw J -- Berenguer, Jose -- Brouns, Stan J J -- van der Oost, John -- P30 CA008748/CA/NCI NIH HHS/ -- R01 GM104962/GM/NIGMS NIH HHS/ -- England -- Nature. 2014 Mar 13;507(7491):258-61. doi: 10.1038/nature12971. Epub 2014 Feb 16.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Dreijenplein 10, 6703 HB Wageningen, the Netherlands [2]. ; Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Dreijenplein 10, 6703 HB Wageningen, the Netherlands. ; Clare Hall Laboratories, Cancer Research UK, London Research Institute, South Mimms EN6 3LD, UK. ; Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China. ; Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA. ; Centro de Biologia Molecular Severo Ochoa, UAM-CSIC, Campus de Cantoblanco, 28049 Madrid, Spain.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24531762" target="_blank"〉PubMed〈/a〉
    Keywords: Argonaute Proteins/*metabolism ; Base Pairing/genetics ; Base Sequence ; DNA/genetics/*metabolism ; *DNA Cleavage ; Deoxycytidine/genetics/metabolism ; *Gene Silencing ; Phosphorylation ; Plasmids/genetics ; Prokaryotic Cells/*metabolism ; Thermus thermophilus/*genetics/*metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2008-08-16
    Description: 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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Brouns, Stan J J -- Jore, Matthijs M -- Lundgren, Magnus -- Westra, Edze R -- Slijkhuis, Rik J H -- Snijders, Ambrosius P L -- Dickman, Mark J -- Makarova, Kira S -- Koonin, Eugene V -- van der Oost, John -- New York, N.Y. -- Science. 2008 Aug 15;321(5891):960-4. doi: 10.1126/science.1159689.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Dreijenplein 10, 6703 HB Wageningen, Netherlands.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18703739" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Bacteriophage lambda/*genetics/*growth & development ; Base Sequence ; DNA, Intergenic ; DNA, Viral/metabolism ; Escherichia coli/genetics/metabolism ; Escherichia coli K12/*genetics/metabolism/*virology ; Escherichia coli Proteins/chemistry/genetics/*metabolism ; Genes, Bacterial ; Molecular Sequence Data ; RNA Precursors/metabolism ; RNA, Bacterial/*genetics/metabolism ; RNA, Guide/genetics/metabolism ; *Repetitive Sequences, Nucleic Acid ; Transcription, Genetic ; Viral Plaque Assay
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2014-08-12
    Description: Clustered regularly interspaced short palindromic repeats (CRISPRs) are essential components of RNA-guided adaptive immune systems that protect bacteria and archaea from viruses and plasmids. In Escherichia coli, short CRISPR-derived RNAs (crRNAs) assemble into a 405-kilodalton multisubunit surveillance complex called Cascade (CRISPR-associated complex for antiviral defense). Here we present the 3.24 angstrom resolution x-ray crystal structure of Cascade. Eleven proteins and a 61-nucleotide crRNA assemble into a seahorse-shaped architecture that binds double-stranded DNA targets complementary to the crRNA-guide sequence. Conserved sequences on the 3' and 5' ends of the crRNA are anchored by proteins at opposite ends of the complex, whereas the guide sequence is displayed along a helical assembly of six interwoven subunits that present five-nucleotide segments of the crRNA in pseudo-A-form configuration. The structure of Cascade suggests a mechanism for assembly and provides insights into the mechanisms of target recognition.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4188430/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4188430/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jackson, Ryan N -- Golden, Sarah M -- van Erp, Paul B G -- Carter, Joshua -- Westra, Edze R -- Brouns, Stan J J -- van der Oost, John -- Terwilliger, Thomas C -- Read, Randy J -- Wiedenheft, Blake -- 082961/Wellcome Trust/United Kingdom -- 082961/Z/07/Z/Wellcome Trust/United Kingdom -- 100140/Wellcome Trust/United Kingdom -- 52006931/Howard Hughes Medical Institute/ -- F32 GM108436/GM/NIGMS NIH HHS/ -- GM063210/GM/NIGMS NIH HHS/ -- P01 GM063210/GM/NIGMS NIH HHS/ -- P20GM103500/GM/NIGMS NIH HHS/ -- P41GM103393/GM/NIGMS NIH HHS/ -- R01 GM108888/GM/NIGMS NIH HHS/ -- R01GM108888/GM/NIGMS NIH HHS/ -- Y1-GM-1104/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2014 Sep 19;345(6203):1473-9. doi: 10.1126/science.1256328. Epub 2014 Aug 7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology and Immunology, Montana State University, Bozeman, MT 59717, USA. ; Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Dreijenplein 10, 6703 HB Wageningen, Netherlands. ; Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. ; Department of Haematology, University of Cambridge, Cambridge Institute for Medical Research, Cambridge CB2 0XY, UK. ; Department of Microbiology and Immunology, Montana State University, Bozeman, MT 59717, USA. bwiedenheft@gmail.com.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25103409" target="_blank"〉PubMed〈/a〉
    Keywords: CRISPR-Associated Proteins/*chemistry ; *CRISPR-Cas Systems ; *Clustered Regularly Interspaced Short Palindromic Repeats ; Crystallography, X-Ray ; Escherichia coli/*genetics ; Escherichia coli Proteins/*chemistry ; RNA Editing ; RNA, Bacterial/*chemistry ; RNA, Guide/*chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2016-04-14
    Description: Prokaryotic CRISPR-Cas adaptive immune systems insert spacers derived from viruses and other parasitic DNA elements into CRISPR loci to provide sequence-specific immunity. This frequently results in high within-population spacer diversity, but it is unclear if and why this is important. Here we show that, as a result of this spacer diversity, viruses can no longer evolve to overcome CRISPR-Cas by point mutation, which results in rapid virus extinction. This effect arises from synergy between spacer diversity and the high specificity of infection, which greatly increases overall population resistance. We propose that the resulting short-lived nature of CRISPR-dependent bacteria-virus coevolution has provided strong selection for the evolution of sophisticated virus-encoded anti-CRISPR mechanisms.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉van Houte, Stineke -- Ekroth, Alice K E -- Broniewski, Jenny M -- Chabas, Helene -- Ashby, Ben -- Bondy-Denomy, Joseph -- Gandon, Sylvain -- Boots, Mike -- Paterson, Steve -- Buckling, Angus -- Westra, Edze R -- DP5-OD021344/OD/NIH HHS/ -- Biotechnology and Biological Sciences Research Council/United Kingdom -- Wellcome Trust/United Kingdom -- England -- Nature. 2016 Apr 21;532(7599):385-8. doi: 10.1038/nature17436. Epub 2016 Apr 13.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉ESI and CEC, Biosciences, University of Exeter, Cornwall Campus, Penryn TR10 9EZ, UK. ; CEFE UMR 5175, CNRS-Universite de Montpellier, Universite Paul-Valery Montpellier, EPHE, 1919, route de Mende 34293, Montpellier Cedex 5, France. ; Department of Integrative Biology, University of California, Berkeley, California 94720, USA. ; CEC, Biosciences, University of Exeter, Cornwall Campus, Penryn TR10 9EZ, UK. ; Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California 94158, USA. ; Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/27074511" target="_blank"〉PubMed〈/a〉
    Keywords: Bacteriophages/genetics/immunology/physiology ; *Biological Evolution ; CRISPR-Cas Systems/*genetics/*immunology ; Extinction, Biological ; Genetic Fitness/genetics/physiology ; Point Mutation/genetics ; Pseudomonas aeruginosa/*genetics/*immunology/virology
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 5
  • 6
    Publication Date: 2011-06-22
    Description: Prokaryotic clustered regularly interspaced short palindromic repeat (CRISPR)/Cas (CRISPR-associated sequences) systems provide adaptive immunity against viruses when a spacer sequence of small CRISPR RNA (crRNA) matches a protospacer sequence in the viral genome. Viruses that escape CRISPR/Cas resistance carry point mutations in protospacers, though not all protospacer mutations lead to escape. Here, we show that in the case of Escherichia coli subtype CRISPR/Cas system, the requirements for crRNA matching are strict only for a seven-nucleotide seed region of a protospacer immediately following the essential protospacer-adjacent motif. Mutations in the seed region abolish CRISPR/Cas mediated immunity by reducing the binding affinity of the crRNA-guided Cascade complex to protospacer DNA. We propose that the crRNA seed sequence plays a role in the initial scanning of invader DNA for a match, before base pairing of the full-length spacer occurs, which may enhance the protospacer locating efficiency of the E. coli Cascade complex. In agreement with this proposal, single or multiple mutations within the protospacer but outside the seed region do not lead to escape. The relaxed specificity of the CRISPR/Cas system limits escape possibilities and allows a single crRNA to effectively target numerous related viruses.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 7
    Publication Date: 2013-05-29
    Description: Proteins that recognize and bind specific sites in DNA are essential for regulation of numerous biological functions. Such proteins often require a negative supercoiled DNA topology to function correctly. In current research, short linear DNA is often used to study DNA–protein interactions. Although linear DNA can easily be modified, for capture on a surface, its relaxed topology does not accurately resemble the natural situation in which DNA is generally negatively supercoiled. Moreover, specific binding sequences are flanked by large stretches of non-target sequence in vivo . Here, we present a straightforward method for capturing negatively supercoiled plasmid DNA on a streptavidin surface. It relies on the formation of a temporary parallel triplex, using a triple helix forming oligonucleotide containing locked nucleic acid nucleotides. All materials required for this method are commercially available. Lac repressor binding to its operator was used as model system. Although the dissociation constants for both the linear and plasmid-based operator are in the range of 4 nM, the association and dissociation rates of Lac repressor binding to the plasmid-based operator are ~18 times slower than on a linear fragment. This difference underscores the importance of using a physiologically relevant DNA topology for studying DNA–protein interactions.
    Keywords: Phsyical and Biochemical Characterisation of DNA
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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