Vaccinia virus morphogenesis is blocked by a temperature-sensitive mutation in the I7 gene that encodes a virion component.
The ts16 mutation of vaccinia virus WR (R. C. Condit, A. Motyczka, and G. Spizz, Virology 128:429-443, 1983) has been mapped by marker rescue to the I7L open reading frame located within the genomic HindIII I DNA fragment. The I7 gene encodes a 423-amino-acid polypeptide. Thermolabile growth was attributed to an amino acid substitution, Pro-344-->Leu, in the predicted I7 protein. A normal temporal pattern of viral protein synthesis was elicited in cells infected with ts16 at the nonpermissive temperature (40 degrees C). Electron microscopy revealed a defect in virion assembly at 40 degrees C. Morphogenesis was arrested at a stage subsequent to formation of spherical immature particles. Western immunoblot analysis with antiserum directed against the I7 polypeptide demonstrated an immunoreactive 47-kDa polypeptide accumulating during the late phase of synchronous vaccinia virus infection. Immunoblotting of extracts of wild-type virions showed that the I7 protein is encapsidated within the virus core. The I7 polypeptide displays amino acid sequence similarity to the type II DNA topoisomerase of Saccharomyces cerevisiae.
Program in Molecular Biology, Sloan-Kettering Institute, New York, New York 10021.
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D000595:Amino Acid Sequence; D004250:DNA Topoisomerases, Type II / Q000235:genetics; D005814:Genes, Viral / Q000235:genetics*; D008969:Molecular Sequence Data; D009024:Morphogenesis; D009154:Mutation; D017421:Sequence Analysis; D017386:Sequence Homology, Amino Acid; D014616:Vaccinia virus / Q000235:genetics / Q000254:growth & development* / Q000648:ultrastructure; D014758:Viral Core Proteins / Q000096:biosynthesis / Q000235:genetics*; D014771:Virion / Q000235:genetics / Q000254:growth & development* / Q000648:ultrastructure
D014758:Viral Core Proteins; C080700:protein I7, vaccinia virus; D004250:DNA Topoisomerases, Type II