Simian virus 40 small-t antigen stimulates viral DNA replication in permissive monkey cells.
The simian virus 40 (SV40) large-T antigen is essential for SV40 DNA replication and for late viral gene expression, but the role of the SV40 small-t antigen in these processes is still unclear. We have previously demonstrated that small t inhibits SV40 DNA replication in vitro. In this study, we investigated the effect of small t on SV40 replication in cultured cells. CV1 monkey cell infection experiments indicated that mutant viruses that lack small t replicate less efficiently than the wild-type virus. We next microinjected CV1 cells with SV40 DNA with and without purified small-t protein and analyzed viral DNA replication efficiency by Southern blotting. Replication of either wild-type SV40 or small-t deletion mutant DNA was increased three- to fivefold in cells coinjected with purified small t. Thus, in contrast to our in vitro observation, small t stimulated viral DNA replication in vivo. This result suggests that small t has cellular effects that are not detectable in a reconstituted in vitro replication system. We also found that small t stimulated progression of permissive monkey cells--but not of nonpermissive rodent cells--from G0-G1 to the S phase of the cell cycle, possibly leading to an optimal intracellular environment for viral replication.
Cicala
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Section on DNA Replication, Repair, and Mutagenesis, National Institute of Child Health and Human Development, Bethesda, Maryland 20892.
Avantaggiati
M L
ML
Graessmann
A
A
Rundell
K
K
Levine
A S
AS
Carbone
M
M
D000818:Animals; D000957:Antigens, Viral, Tumor / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D004261:DNA Replication / Q000187:drug effects*; D004279:DNA, Viral / Q000096:biosynthesis*; D051379:Mice; D008845:Microinjections; D009154:Mutation; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D013539:Simian virus 40 / Q000254:growth & development* / Q000276:immunology; D014779:Virus Replication
D000957:Antigens, Viral, Tumor; D004279:DNA, Viral; D011494:Protein Kinases