Identification of the point mutations in two vaccinia virus nucleoside triphosphate phosphohydrolase I temperature-sensitive mutants and role of this DNA-dependent ATPase enzyme in virus gene expression.
The biological function of the nucleoside triphosphate phosphohydrolase I (NTPase I) enzyme of vaccinia virus is not yet known. In this investigation we have identified the genetic lesion of two temperature-sensitive mutants of vaccinia virus, ts50 and ts36, as single point mutations contained within the 5'615 nucleotides of the NTPase I gene (ts50, G to A at position 131; ts36, C to T at position 556). The point mutations result in amino acid substitutions of Gly to Glu-44 (ts50) and Pro to Ser-186 (ts36). In monkey BSC-40 cells, ts50 and ts36 behave phenotypically like wild-type virus with respect to replication and synthesis of viral DNA but are defective in late polypeptide synthesis. However, these two ts mutants displayed a drastically different phenotype in virus-infected human HeLa cells at the restrictive temperature; viral DNA replication did not occur and late polypeptide synthesis was absent. Moreover, if the early block was overcome by a temperature shift-up, then HeLa cells infected with the ts mutants displayed a profile characteristic of defective late viral polypeptide synthesis. Our results reveal that vaccinia NTPase I enzyme functions early and late in the viral replication cycle and that the phenotype of these ts mutants is dependent upon the cell type.
Kahn
J S
JS
Department of Biochemistry, State University of New York, Brooklyn 11203.
Esteban
M
M
D001483:Base Sequence; D004279:DNA, Viral / Q000032:analysis / Q000096:biosynthesis; D015870:Gene Expression; D006918:Hydroxyurea / Q000494:pharmacology; D008969:Molecular Sequence Data; D009154:Mutation; D043583:Nucleoside-Triphosphatase; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000502:physiology*; D013696:Temperature; D014616:Vaccinia virus / Q000201:enzymology / Q000235:genetics*; D014764:Viral Proteins / Q000096:biosynthesis; D014779:Virus Replication
D004279:DNA, Viral; D014764:Viral Proteins; D010744:Phosphoric Monoester Hydrolases; D043583:Nucleoside-Triphosphatase; D006918:Hydroxyurea