Abstract
Transport-defective mutants of PARA, an SV40-adenovirus 7 hybrid virus, induce the synthesis of SV40 large T-antigen (T-ag) that is not transported to the nucleus and accumulates in the cytoplasm (cT-ag) of infected and transformed cells. The ability of cT mutants of PARA to induce phenotypic transformation of hamster embryo fibroblasts was examined. The cytoplasmic localization of T-ag was not stable, as extensive subculturing resulted in cell populations comprised of mixtures of cells which expressed T-ag in either the nucleus and/or the cytoplasm. Clonal analysis resulted in the selection of two cell populations: one cell type expressed T-ag solely in the cytoplasm and the second contained a mixture of cells which expressed T-ag in the nucleus and/or the cytoplasm. Serial subculture of clonal cell lines containing T-ag exclusively in the cytoplasm resulted again in the evolution of mixed populations which expressed T-ag in the nucleus and/or the cytoplasm. Analysis of synchronized cultures of such mixed clonal lines revealed that the intracellular distribution of T-ag was under the influence of the cell cycle; T-ag was present in the nucleus during S-phase, the period of maximal DNA synthesis, and in the cytoplasm during other phases of the cell cycle. These results suggest that a selective advantage exists during in vitro culturing for cells with a partial reversion of the cT phenotype. Examination of the growth properties of clonal lines in vitro indicated that cells in which T-ag could be detected in the cytoplasm, either continuously or during certain phases of the cell cycle, exhibited reduced growth potential under stringent culture conditions relative to wild-type transformants, behaving more like minimal transformants. In addition, the capacity for tumor induction in weanling hamsters by PARA(cT)-transformed hamster cells was reduced substantially in comparison to wild-type transformed cells. These results suggest that the constant presence of SV40 T-ag in the nucleus promotes maximal expression of the transformed cell phenotype.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 147-158 |
| Number of pages | 12 |
| Journal | Virology |
| Volume | 110 |
| Issue number | 1 |
| DOIs | |
| State | Published - Apr 15 1981 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Virology
- Infectious Diseases
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Effect of nuclear localization of large tumor antigen on growth potential of SV40-transformed cells. / Lanford, Robert E.; Butel, Janet S.
In: Virology, Vol. 110, No. 1, 15.04.1981, p. 147-158.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Effect of nuclear localization of large tumor antigen on growth potential of SV40-transformed cells
AU - Lanford, Robert E.
AU - Butel, Janet S.
PY - 1981/4/15
Y1 - 1981/4/15
N2 - Transport-defective mutants of PARA, an SV40-adenovirus 7 hybrid virus, induce the synthesis of SV40 large T-antigen (T-ag) that is not transported to the nucleus and accumulates in the cytoplasm (cT-ag) of infected and transformed cells. The ability of cT mutants of PARA to induce phenotypic transformation of hamster embryo fibroblasts was examined. The cytoplasmic localization of T-ag was not stable, as extensive subculturing resulted in cell populations comprised of mixtures of cells which expressed T-ag in either the nucleus and/or the cytoplasm. Clonal analysis resulted in the selection of two cell populations: one cell type expressed T-ag solely in the cytoplasm and the second contained a mixture of cells which expressed T-ag in the nucleus and/or the cytoplasm. Serial subculture of clonal cell lines containing T-ag exclusively in the cytoplasm resulted again in the evolution of mixed populations which expressed T-ag in the nucleus and/or the cytoplasm. Analysis of synchronized cultures of such mixed clonal lines revealed that the intracellular distribution of T-ag was under the influence of the cell cycle; T-ag was present in the nucleus during S-phase, the period of maximal DNA synthesis, and in the cytoplasm during other phases of the cell cycle. These results suggest that a selective advantage exists during in vitro culturing for cells with a partial reversion of the cT phenotype. Examination of the growth properties of clonal lines in vitro indicated that cells in which T-ag could be detected in the cytoplasm, either continuously or during certain phases of the cell cycle, exhibited reduced growth potential under stringent culture conditions relative to wild-type transformants, behaving more like minimal transformants. In addition, the capacity for tumor induction in weanling hamsters by PARA(cT)-transformed hamster cells was reduced substantially in comparison to wild-type transformed cells. These results suggest that the constant presence of SV40 T-ag in the nucleus promotes maximal expression of the transformed cell phenotype.
AB - Transport-defective mutants of PARA, an SV40-adenovirus 7 hybrid virus, induce the synthesis of SV40 large T-antigen (T-ag) that is not transported to the nucleus and accumulates in the cytoplasm (cT-ag) of infected and transformed cells. The ability of cT mutants of PARA to induce phenotypic transformation of hamster embryo fibroblasts was examined. The cytoplasmic localization of T-ag was not stable, as extensive subculturing resulted in cell populations comprised of mixtures of cells which expressed T-ag in either the nucleus and/or the cytoplasm. Clonal analysis resulted in the selection of two cell populations: one cell type expressed T-ag solely in the cytoplasm and the second contained a mixture of cells which expressed T-ag in the nucleus and/or the cytoplasm. Serial subculture of clonal cell lines containing T-ag exclusively in the cytoplasm resulted again in the evolution of mixed populations which expressed T-ag in the nucleus and/or the cytoplasm. Analysis of synchronized cultures of such mixed clonal lines revealed that the intracellular distribution of T-ag was under the influence of the cell cycle; T-ag was present in the nucleus during S-phase, the period of maximal DNA synthesis, and in the cytoplasm during other phases of the cell cycle. These results suggest that a selective advantage exists during in vitro culturing for cells with a partial reversion of the cT phenotype. Examination of the growth properties of clonal lines in vitro indicated that cells in which T-ag could be detected in the cytoplasm, either continuously or during certain phases of the cell cycle, exhibited reduced growth potential under stringent culture conditions relative to wild-type transformants, behaving more like minimal transformants. In addition, the capacity for tumor induction in weanling hamsters by PARA(cT)-transformed hamster cells was reduced substantially in comparison to wild-type transformed cells. These results suggest that the constant presence of SV40 T-ag in the nucleus promotes maximal expression of the transformed cell phenotype.
UR - http://www.scopus.com/inward/record.url?scp=0019414493&partnerID=8YFLogxK
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U2 - 10.1016/0042-6822(81)90016-7
DO - 10.1016/0042-6822(81)90016-7
M3 - Article
C2 - 6259826
AN - SCOPUS:0019414493
VL - 110
SP - 147
EP - 158
JO - Virology
JF - Virology
SN - 0042-6822
IS - 1
ER -