Quantitation of simian virus 40 T-antigen correlated with the cell cycle of permissive and non-permissive cells.
These studies examined cell cycle progression and quantitative changes in T-antigen following infection by SV40. Single cells were assayed by multiparameter flow cytometric analysis (FCM) for DNA content and T-antigen expression. Conditions were used which permitted permissive, semi-permissive, and non-permissive cells to be monitored through two rounds of DNA synthesis induced by SV40. The permissive cells included the monkey kidney cell lines; CV-1, Vero and BSC-1 and the COS-1 and COS-7 which are CV-1 cells transformed with an origin defective SV40. The non-permissive cell strains included mouse embryo fibroblasts, Chinese hamster fibroblasts, and IMR-90, a human diploid fibroblast. Cell types differed in the maximal amount of T-antigen expressed per cell. Additionally, all cell types expressed a limited quantity of T-antigen for each cell cycle phase and the quantity increased in each successive phase. The level in each phase was increased only two-fold when 100 times more virus was used. Thus, for an infected population the quantity of T-antigen was dependent on cell cycle distribution. High levels of T-antigen were not required for permissive infection; however, permissive cells were distinguished from non-permissive cells by the G2 levels. Permissive G2 cells had more than double the T-antigen content expressed in G1, while nonpermissive G2 cells had less than a two-fold increase over G1 levels. The appearance of cells with tetraploid DNA content and the failure to undergo mitosis correlated to the higher T-antigen levels in the G2 of the permissive cells. Two other strains of SV40, 776, and VA45 exhibit similar values for T-antigen expression and movement into tetraploid DNA content. This study establishes the levels of T-antigen correlated to the cell cycle and cell type.
Department of Microbiology, Immunology and Molecular Genetics, Albany Medical College, New York 12208.
J M
JM
Lehman
T D
TD
Friedrich
J
J
Laffin
D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000032:analysis* / Q000096:biosynthesis; D002453:Cell Cycle; D002460:Cell Line; D002472:Cell Transformation, Viral; D002522:Chlorocebus aethiops; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000032:analysis; D003673:Defective Viruses / Q000502:physiology; D005347:Fibroblasts / Q000382:microbiology*; D005434:Flow Cytometry; D006801:Humans; D051379:Mice / Q000196:embryology; D013539:Simian virus 40 / Q000276:immunology / Q000502:physiology; D013045:Species Specificity; D014779:Virus Replication
D000952:Antigens, Polyomavirus Transforming; D004247:DNA