title: Functional characterization of a conserved archaeal viral operon revealing single-stranded DNA binding, annealing and nuclease activities.
abstract: The majority of archaeal viral genes are of unknown function hindering our understanding of the virus life cycle and viral interactions with their host. Here, we first describe functional characterization of ORF131b (gp17) and ORF436 (gp18) of Sulfolobus islandicus rod-shaped virus 2 (SIRV2), both encoding proteins of unknown function and forming an operon with ORF207 (gp19). SIRV2 gp17 was found to be a single-stranded DNA (ssDNA) binding protein different in structure from all previously characterized ssDNA binding proteins. Mutagenesis of a few conserved basic residues suggested a U-shaped binding path for ssDNA. The recombinant gp18 showed an ssDNA annealing activity often associated with helicases and recombinases. To gain insight into the biological role of the entire operon, we characterized SIRV2 gp19 and showed it to possess a 5' → 3' ssDNA exonuclease activity, in addition to the previously demonstrated ssDNA endonuclease activity. Further, in vitro pull-down assay demonstrated interactions between gp17 and gp18 and between gp18 and gp19 with the former being mediated by the intrinsically disordered C-terminus of gp17. The strand-displacement replication mode proposed previously for rudiviruses and the close interaction among the ssDNA binding, annealing and nuclease proteins strongly point to a role of the gene operon in genome maturation and/or DNA recombination that may function in viral DNA replication/repair.
authors.affiliation: Department of Biology, University of Copenhagen, Ole Maaloes Vej 5, DK-2200 Copenhagen N, Denmark.
authors.forename: Yang
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Department of Biology, University of Copenhagen, Ole Maaloes Vej 5, DK-2200 Copenhagen N, Denmark.
authors.forename: Birthe B
authors.initials: BB
authors.lastname: Kragelund
authors.affiliation: Biomedical Sciences Research Complex, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9ST, United Kingdom.
authors.forename: Malcolm F
authors.initials: MF
authors.lastname: White
authors.affiliation: Department of Biology, University of Copenhagen, Ole Maaloes Vej 5, DK-2200 Copenhagen N, Denmark. Electronic address: peng@bio.ku.dk.
authors.forename: Xu
authors.initials: X
authors.lastname: Peng
mesh_terms: D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004252:DNA Mutational Analysis; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D003851:Deoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D009876:Operon; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D023642:Rudiviridae / Q000201:enzymology* / Q000235:genetics; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D014764:Viral Proteins; D003851:Deoxyribonucleases; D004265:DNA Helicases
keywords: Archaea virus; DNA replication/repair; genome maturation; ssDNA metabolism