The genome of Melanoplus sanguinipes Entomopoxvirus

The family Poxpiridae contains two subfamilies: the Entomopoxvirinae (poxvi ruses of insects) and the Chordopoxvirinae (poxviruses of vertebrates), Her e we present the first characterization of the genome of an entomopoxvirus (EPV) which infects the North American migratory grasshopper Melanoplus san guinipes and other important orthopteran pests. The 236-kbp M. sanguinipes EPV (MsEPV) genome consists of a central coding region bounded by 7-kbp inv erted terminal repeats and contains 267 open reading frames (ORFs), of whic h 107 exhibit similarity to previously described genes. The presence of gen es not previously described in poxviruses, and in some cases in any other k nown virus, suggests significant viral adaptation to the arthropod host and the external environment. Genes predicting interactions with host cellular mechanisms include homologues of the inhibitor of apoptosis protein, stres s response protein phosphatase 2C, extracellular matrixin metalloproteases, ubiquitin, calcium binding EF-hand protein, glycosyltransferase, and a tri acylglyceride lipase, MsEPV genes with putative functions in prevention and repair of DNA damage include a complete base excision repair pathway (urac il DNA glycosylase, AP endonuclease, DNA polymerase beta, and an NAD(+)-dep endent DNA ligase), a photoreactivation repair pathway (cyclobutane pyrimid ine dimer photolyase), a LINE-type reverse transcriptase, and a mutT homolo gue, The presence of these specific repair pathways may represent viral ada ptation for repair of environmentally induced DNA damage. The absence of pr eviously described poxvirus enzymes involved in nucleotide metabolism and t he presence of a novel thymidylate synthase homologue suggest that MsEPV is heavily reliant on host cell nucleotide pools and the de novo nucleotide b iosynthesis pathway. MsEPV and lepidopteran genus B EPVs lack genome coline arity and exhibit a low level of amino acid identity among homologous genes (20 to 59%), perhaps reflecting a significant evolutionary distance betwee n lepidopteran and orthopteran viruses. Divergence between MsEPV and the Ch ordopoxvirinae is indicated by the presence of only 49 identifiable chordop oxvirus homologues, low-level amino acid identity among these genes (20 to 48%), and the presence in MsEPV of 43 novel ORFs in five gene families. Gen es common to both poxvirus subfamilies, which include those encoding enzyme s involved in RNA transcription and modification, DNA replication, protein processing, virion assembly, and virion structural proteins, define the gen etic core of the Poxviridae.