title: KSHV SOX mediated host shutoff: the molecular mechanism underlying mRNA transcript processing.
abstract: Onset of the lytic phase in the KSHV life cycle is accompanied by the rapid, global degradation of host (and viral) mRNA transcripts in a process termed host shutoff. Key to this destruction is the virally encoded alkaline exonuclease SOX. While SOX has been shown to possess an intrinsic RNase activity and a potential consensus sequence for endonucleolytic cleavage identified, the structures of the RNA substrates targeted remained unclear. Based on an analysis of three reported target transcripts, we were able to identify common structures and confirm that these are indeed degraded by SOX in vitro as well as predict the presence of such elements in the KSHV pre-microRNA transcript K12-2. From these studies, we were able to determine the crystal structure of SOX productively bound to a 31 nucleotide K12-2 fragment. This complex not only reveals the structural determinants required for RNA recognition and degradation but, together with biochemical and biophysical studies, reveals distinct roles for residues implicated in host shutoff. Our results further confirm that SOX and the host exoribonuclease Xrn1 act in concert to elicit the rapid degradation of mRNA substrates observed in vivo, and that the activities of the two ribonucleases are co-ordinated.
authors.affiliation: Institute for Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, Malet Street, London WC1E 7HX, UK.|Department of Structural and Molecular Biology, University College London, London, WC1E 6BT, UK.
authors.forename: Hyunah
authors.initials: H
authors.lastname: Lee
authors.affiliation: Institute for Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, Malet Street, London WC1E 7HX, UK.
authors.forename: Anathe O M
authors.initials: AOM
authors.lastname: Patschull
authors.affiliation: Institute for Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, Malet Street, London WC1E 7HX, UK.
authors.forename: Claire
authors.initials: C
authors.lastname: Bagnéris
authors.affiliation: Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
authors.forename: Hannah
authors.initials: H
authors.lastname: Ryan
authors.affiliation: Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX, UK.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Sanderson
authors.affiliation: Department of Functional and Comparative Genomics, Institute of Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, UK.
authors.forename: Bahram
authors.initials: B
authors.lastname: Ebrahimi
authors.affiliation: Institute for Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, Malet Street, London WC1E 7HX, UK.
authors.forename: Irene
authors.initials: I
authors.lastname: Nobeli
authors.affiliation: Institute for Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, Malet Street, London WC1E 7HX, UK.
authors.forename: Tracey E
authors.initials: TE
authors.lastname: Barrett
mesh_terms: D018360:Crystallography, X-Ray; D015870:Gene Expression; D019288:Herpesvirus 8, Human / Q000737:chemistry* / Q000235:genetics; D054884:Host-Pathogen Interactions / Q000235:genetics; D006801:Humans; D008018:Life Cycle Stages / Q000235:genetics; D011487:Protein Conformation; D012313:RNA / Q000737:chemistry*; D012333:RNA, Messenger / Q000235:genetics; D016601:RNA-Binding Proteins / Q000737:chemistry*; D055748:SOXB1 Transcription Factors / Q000737:chemistry* / Q000235:genetics
chemical_list: D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D055748:SOXB1 Transcription Factors; D012313:RNA