title: Control of Polyomavirus T-antigen and DNA synthesis in mouse embryo fibroblast cells by vitamin A.
abstract: Vitamin A (retinoic acid, 10(-6) M) treatment of confluent mouse embryo cells for only 7 h resulted in optimal inhibition of Polyomavirus replication. Depending upon the input multiplicity of virus, one could wait until between 12 and 18 h postinfection to add vitamin A and still observe maximal inhibition of virus yields. Taken together, and assuming the same kinetics before and after virus infection, these results suggested that the inhibitory action of vitamin A occurred between 19 and 25 h into the Polyomavirus replication cycle. In this model system, such a time corresponded to the onset of T-antigen expression and virus-induced cellular DNA synthesis. Analysis of both viral and virus-induced cellular DNA synthesis by the method of Hirt (J. Mol. Biol., 26: 365-369, 1967) and by cesium chloride gradients suggested that vitamin A preferentially inhibited viral, more than virus-induced cellular, DNA synthesis in confluent cell monolayers. Vitamin A also concomitantly inhibited Polyomavirus T-antigen expression in such confluent cultures. In contrast, viral DNA synthesis and infectious virus yields were not significantly inhibited by vitamin A in subconfluent cell cultures. The antagonistic effect of vitamin A on Polyomavirus replication in confluent monolayers could be blocked with cycloheximide, a reversible protein synthesis inhibitor. This suggested that vitamin A inhibition of Polyomavirus replication was indirect and mediated by a newly synthesized protein. Taken together, these results suggest that vitamin A induced a protein in confluent, but not subconfluent, cells, which blocked the expression of Polyomavirus T-antigen. Decreased amounts of T-antigen most likely reduced Polyomavirus and cellular DNA synthesis and virus yield.
authors.forename: J K
authors.initials: JK
authors.lastname: Russell
authors.forename: J E
authors.initials: JE
authors.lastname: Blalock
mesh_terms: D000818:Animals; D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor / Q000032:analysis*; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis*; D004279:DNA, Viral / Q000096:biosynthesis; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000378:metabolism; D051379:Mice; D011120:Polyomavirus / Q000187:drug effects* / Q000502:physiology; D014764:Viral Proteins / Q000032:analysis*; D014779:Virus Replication / Q000187:drug effects; D014801:Vitamin A / Q000494:pharmacology*
chemical_list: D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor; D004279:DNA, Viral; D014764:Viral Proteins; D014801:Vitamin A; D004247:DNA; D003513:Cycloheximide