title: Chilo iridescent virus encodes a putative helicase belonging to a distinct family within the "DEAD/H" superfamily: implications for the evolution of large DNA viruses.
abstract: The complete nucleotide sequence of the EcoRI DNA fragment M (7099 bp; 0.310-0.345 map units) of the genome of insect iridescent virus type 6--Chilo iridescent virus (CIV)--was determined. A 606 codon open reading frame located in this region encoded a protein (p69) related to a distinct family of putative DNA and/or RNA helicases belonging to the "DEAD/H" superfamily. Unique sequence signatures were derived that allowed selective retrieval of the putative helicases of the new family from amino acid sequence databases. The family includes yeast, Drosophila, mammalian, and bacterial proteins involved in transcription regulation and in repair of damaged DNA. It is hypothesized that p69 of CIV may be a DNA or RNA helicase possibly involved in viral transcription. A distant relationship was observed to exist between this family of helicases and another group of proteins that consists of putative helicases of poxviruses, African swine fever virus, and yeast mitochondrial plasmids. It is shown that p69 of CIV is much more closely related to cellular helicases than any of the other known viral helicases. Phylogenetic analysis suggested an independent origin for the p69 gene and the genes encoding other viral helicases.
authors.affiliation: Institut für Medizinsche Virologie der Universität Heidelberg, FRG.
authors.forename: K C
authors.initials: KC
authors.lastname: Sonntag
authors.forename: P
authors.initials: P
authors.lastname: Schnitzler
authors.forename: E V
authors.initials: EV
authors.lastname: Koonin
authors.forename: G
authors.initials: G
authors.lastname: Darai
mesh_terms: D000595:Amino Acid Sequence; D001482:Base Composition; D001483:Base Sequence; D005075:Biological Evolution; D016384:Consensus Sequence; D004265:DNA Helicases / Q000737:chemistry / Q000235:genetics*; D005814:Genes, Viral / Q000235:genetics*; D017994:Iridovirus / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D020365:RNA Helicases; D012316:RNA Nucleotidyltransferases / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015678:Viral Structural Proteins / Q000235:genetics*
chemical_list: D015678:Viral Structural Proteins; D012316:RNA Nucleotidyltransferases; D004265:DNA Helicases; D020365:RNA Helicases