title: CRISPR-Cas type I-A Cascade complex couples viral infection surveillance to host transcriptional regulation in the dependence of Csa3b.
abstract: CRISPR-Cas (clustered regularly interspaced short palindromic repeats and the associated genes) constitute adaptive immune systems in bacteria and archaea and they provide sequence specific immunity against foreign nucleic acids. CRISPR-Cas systems are activated by viral infection. However, little is known about how CRISPR-Cas systems are activated in response to viral infection or how their expression is controlled in the absence of viral infection. Here, we demonstrate that both the transcriptional regulator Csa3b, and the type I-A interference complex Cascade, are required to transcriptionally repress the interference gene cassette in the archaeon Sulfolobus. Csa3b binds to two palindromic repeat sites in the promoter region of the cassette and facilitates binding of the Cascade to the promoter region. Upon viral infection, loading of Cascade complexes onto crRNA-matching protospacers leads to relief of the transcriptional repression. Our data demonstrate a mechanism coupling CRISPR-Cas surveillance of protospacers to transcriptional regulation of the interference gene cassette thereby allowing a fast response to viral infection.
authors.affiliation: Archaea Centre, Department of Biology, Copenhagen University, DK2200 Copenhagen N, Denmark.
authors.forename: Fei
authors.initials: F
authors.lastname: He
authors.affiliation: Helmholtz Zentrum München, Research Unit Environmental Genomics, Ingolstädter Landstraße 1, 85764 Oberschleißheim, Germany.
authors.forename: Gisle
authors.initials: G
authors.lastname: Vestergaard
authors.affiliation: Archaea Centre, Department of Biology, Copenhagen University, DK2200 Copenhagen N, Denmark.
authors.forename: Wenfang
authors.initials: W
authors.lastname: Peng
authors.affiliation: Archaea Centre, Department of Biology, Copenhagen University, DK2200 Copenhagen N, Denmark.
authors.forename: Qunxin
authors.initials: Q
authors.lastname: She
authors.affiliation: Archaea Centre, Department of Biology, Copenhagen University, DK2200 Copenhagen N, Denmark.
authors.forename: Xu
authors.initials: X
authors.lastname: Peng
mesh_terms: D001105:Archaea / Q000235:genetics; D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism*; D064130:CRISPR-Associated Proteins / Q000378:metabolism*; D064113:CRISPR-Cas Systems; D064112:Clustered Regularly Interspaced Short Palindromic Repeats; D019143:Evolution, Molecular; D019848:Gene Expression Regulation, Archaeal; D055786:Gene Knockout Techniques; D010802:Phylogeny; D016944:Sulfolobus / Q000235:genetics* / Q000378:metabolism / Q000821:virology*; D014158:Transcription, Genetic
chemical_list: D019843:Archaeal Proteins; D064130:CRISPR-Associated Proteins