Induction of cellular DNA synthesis by a simian virus 40 mutant defective in nuclear transport of T antigen

1985 ◽  
Vol 5 (6) ◽  
pp. 1531-1533
Author(s):  
R E Lanford ◽  
J K Hyland ◽  
R Baserga ◽  
J S Butel
Keyword(s):  
Dna Synthesis ◽  
Limit Of Detection ◽  
Nuclear Transport ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Quiescent Cells ◽  
Cellular Dna

The simian virus 40 (SV40) (cT)-3 mutant [SV40(cT)-3], which is defective in nuclear transport of T antigen, was utilized to determine whether cellular DNA synthesis can be stimulated by SV40 in the absence of detectable nuclear T antigen. Cellular DNA synthesis was examined in the temperature-sensitive cell cycle mutants, BHK ts13 and BHK tsAF8, after microinjection of quiescent cells with plasmid DNA containing cloned copies of wild-type SV40 or SV40(cT)-3. The efficiency of induction of cellular DNA synthesis was identical for both wild-type SV40 and SV40(cT)-3 in both cell lines. The results suggest that cell surface-associated T antigen, either alone or possibly in combination with minimal amounts of nuclear T antigen below our limit of detection, is able to stimulate cellular DNA synthesis.

scholarly journals Induction of cellular DNA synthesis by a simian virus 40 mutant defective in nuclear transport of T antigen.

1985 ◽  
Vol 5 (6) ◽  
pp. 1531-1533 ◽  
Author(s):  
R E Lanford ◽  
J K Hyland ◽  
R Baserga ◽  
J S Butel
Keyword(s):  
Dna Synthesis ◽  
Limit Of Detection ◽  
Nuclear Transport ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Quiescent Cells ◽  
Cellular Dna

The simian virus 40 (SV40) (cT)-3 mutant [SV40(cT)-3], which is defective in nuclear transport of T antigen, was utilized to determine whether cellular DNA synthesis can be stimulated by SV40 in the absence of detectable nuclear T antigen. Cellular DNA synthesis was examined in the temperature-sensitive cell cycle mutants, BHK ts13 and BHK tsAF8, after microinjection of quiescent cells with plasmid DNA containing cloned copies of wild-type SV40 or SV40(cT)-3. The efficiency of induction of cellular DNA synthesis was identical for both wild-type SV40 and SV40(cT)-3 in both cell lines. The results suggest that cell surface-associated T antigen, either alone or possibly in combination with minimal amounts of nuclear T antigen below our limit of detection, is able to stimulate cellular DNA synthesis.

E1A induces phosphorylation of the retinoblastoma protein independently of direct physical association between the E1A and retinoblastoma products

1991 ◽  
Vol 11 (8) ◽  
pp. 4253-4265
Author(s):  
H G Wang ◽  
G Draetta ◽  
E Moran
Keyword(s):  
Cell Cycle ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Binding Activity ◽  
T Antigen ◽  
Physical Interaction ◽  
Resting Cells ◽  
Wild Type ◽  
Quiescent Cells ◽  
Kinase Expression

We have studied the initial effects of adenovirus E1A expression on the retinoblastoma (RB) gene product in normal quiescent cells. Although binding of the E1A products to pRB could, in theory, make pRB phosphorylation unnecessary for cell cycle progression, we have found that the 12S wild-type E1A product is capable of inducing phosphorylation of pRB in normal quiescent cells. The induction of pRB phosphorylation correlates with E1A-mediated induction of p34cdc2 expression and kinase activity, consistent with the possibility that p34cdc2 is a pRB kinase. Expression of simian virus 40 T antigen induces similar effects. Induction of pRB phosphorylation is independent of the pRB binding activity of the E1A products; E1A domain 2 mutants do not bind detectable levels of pRB but remain competent to induce pRB phosphorylation and to activate cdc2 protein kinase expression and activity. Although the kinetics of induction are slower, domain 2 mutants induce wild-type levels of pRB phosphorylation and host cell DNA synthesis and yet fail to induce cell proliferation. These results imply that direct physical interaction between the RB and E1A products does not play a required role in the early stages of E1A-mediated cell cycle induction and that pRB phosphorylation is not, of itself, sufficient to allow quiescent cells to divide. These results suggest that the E1A products do not need to bind pRB in order to stimulate resting cells to enter the cell cycle. Indeed, a more important role of the RB binding activity of the E1A products may be to prevent dividing cells from returning to G0.

Functional simian virus 40 T antigen is expressed in hybrid cells having finite proliferative potential

1987 ◽  
Vol 7 (4) ◽  
pp. 1541-1544
Author(s):  
O M Pereira-Smith ◽  
J R Smith
Keyword(s):  
Dna Synthesis ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Transformed Cells ◽  
Proliferative Potential ◽  
Hybrid Cells ◽  
Ras Oncogenes ◽  
Immortal Cells ◽  
Cellular Dna

Simian virus 40-transformed human cells fused with other independently derived simian virus 40-transformed cells and tumor-derived cells containing activated H-ras and N-ras oncogenes yielded hybrids capable of indefinite division. Fusions with various other immortal cells yielded hybrids that had limited division potential. T antigen expressed in limited-division hybrids was functional for the induction of cellular DNA synthesis.

scholarly journals E1A induces phosphorylation of the retinoblastoma protein independently of direct physical association between the E1A and retinoblastoma products.

1991 ◽  
Vol 11 (8) ◽  
pp. 4253-4265 ◽  
Author(s):  
H G Wang ◽  
G Draetta ◽  
E Moran
Keyword(s):  
Cell Cycle ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Binding Activity ◽  
T Antigen ◽  
Physical Interaction ◽  
Resting Cells ◽  
Wild Type ◽  
Quiescent Cells ◽  
Kinase Expression

We have studied the initial effects of adenovirus E1A expression on the retinoblastoma (RB) gene product in normal quiescent cells. Although binding of the E1A products to pRB could, in theory, make pRB phosphorylation unnecessary for cell cycle progression, we have found that the 12S wild-type E1A product is capable of inducing phosphorylation of pRB in normal quiescent cells. The induction of pRB phosphorylation correlates with E1A-mediated induction of p34cdc2 expression and kinase activity, consistent with the possibility that p34cdc2 is a pRB kinase. Expression of simian virus 40 T antigen induces similar effects. Induction of pRB phosphorylation is independent of the pRB binding activity of the E1A products; E1A domain 2 mutants do not bind detectable levels of pRB but remain competent to induce pRB phosphorylation and to activate cdc2 protein kinase expression and activity. Although the kinetics of induction are slower, domain 2 mutants induce wild-type levels of pRB phosphorylation and host cell DNA synthesis and yet fail to induce cell proliferation. These results imply that direct physical interaction between the RB and E1A products does not play a required role in the early stages of E1A-mediated cell cycle induction and that pRB phosphorylation is not, of itself, sufficient to allow quiescent cells to divide. These results suggest that the E1A products do not need to bind pRB in order to stimulate resting cells to enter the cell cycle. Indeed, a more important role of the RB binding activity of the E1A products may be to prevent dividing cells from returning to G0.

scholarly journals Induction of Duplication Reversion in Human Fibroblasts, by Wild-Type and Mutated SV40 T Antigen, Covaries With the Ability to Induce Host DNA Synthesis

Genetics ◽  
1997 ◽  
Vol 146 (4) ◽  
pp. 1417-1428
Author(s):  
Masood A Shammas ◽  
Shujuan J Xia ◽  
Robert J Shmookler Reis
Keyword(s):  
Homologous Recombination ◽  
Dna Synthesis ◽  
Human Fibroblasts ◽  
Point Mutations ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Hypoxanthine Phosphoribosyl Transferase ◽  
Wild Type ◽  
Chromosomal Recombination

Intrachromosomal homologous recombination, manifest as reversion of a 14-kbp duplication in the hypoxanthine phosphoribosyl transferase (HPRT) gene, is elevated in human cells either stably transformed or transiently transfected by the SV40 (simian virus 40) large T antigen gene. Following introduction of wild-type SV40, or any of several T-antigen point mutations in a constant SV40 background, we observed a strong correlation between the stimulation of chromosomal recombination and induction of host-cell DNA synthesis. Moreover, inhibitors of DNA replication (aphidicolin and hydroxyurea) suppress SV40-induced homologous recombination to the extent that they suppress DNA synthesis. Stable integration of plasmids encoding T antigen also augments homologous recombination, which is suppressed by aphidicolin. We infer that the mechanism by which T antigen stimulates homologous recombination in human fibroblasts involves DNA replicative synthesis.

Mutational analysis of simian virus 40 T antigen: stimulation of cellular DNA synthesis and activation of rRNA genes by mutants with deletions in the T-antigen gene

1983 ◽  
Vol 3 (2) ◽  
pp. 214-219
Author(s):  
K J Soprano ◽  
N Galanti ◽  
G J Jonak ◽  
S McKercher ◽  
J M Pipas ◽  
...  
Keyword(s):  
Dna Synthesis ◽  
Mutational Analysis ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Rrna Genes ◽  
Hybrid Cells ◽  
The Common ◽  
Cellular Dna ◽  
Stimulation Of

The biological activity of several deletion mutants of simian virus 40, cloned in pBR322, was determined. Three functions of the simian virus 40 A gene were studied: (i) the ability to express T antigen; (ii) the ability to induce cell DNA replication; and (iii) the ability to reactivate silent rRNA genes in hybrid cells. Recombinant plasmid DNA was introduced into cells by manual microinjection or by transfection. The results (together with previous reports) indicate that the critical sequences for these three functions are located separately on the simian virus 40 A gene, as follows: (i) the sequences necessary for the detection of the common antigenic determinant of T antigen extend from nucleotide 4147 to nucleotide 4001 (map units 0.45 to 0.42); (ii) the sequences critical for the stimulation of cell DNA synthesis extend from nucleotide 4327 to nucleotide 4001 (map units 0.49 to 0.42); and (iii) those critical for the reactivation of rRNA genes extend approximately from nucleotide 3827 to nucleotide 3526 (map units 0.39 to 0.33).

scholarly journals Functional simian virus 40 T antigen is expressed in hybrid cells having finite proliferative potential.

1987 ◽  
Vol 7 (4) ◽  
pp. 1541-1544 ◽  
Author(s):  
O M Pereira-Smith ◽  
J R Smith
Keyword(s):  
Dna Synthesis ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Transformed Cells ◽  
Proliferative Potential ◽  
Hybrid Cells ◽  
Ras Oncogenes ◽  
Immortal Cells ◽  
Cellular Dna

Simian virus 40-transformed human cells fused with other independently derived simian virus 40-transformed cells and tumor-derived cells containing activated H-ras and N-ras oncogenes yielded hybrids capable of indefinite division. Fusions with various other immortal cells yielded hybrids that had limited division potential. T antigen expressed in limited-division hybrids was functional for the induction of cellular DNA synthesis.

scholarly journals Mutational analysis of simian virus 40 T antigen: stimulation of cellular DNA synthesis and activation of rRNA genes by mutants with deletions in the T-antigen gene.

1983 ◽  
Vol 3 (2) ◽  
pp. 214-219 ◽  
Author(s):  
K J Soprano ◽  
N Galanti ◽  
G J Jonak ◽  
S McKercher ◽  
J M Pipas ◽  
...  
Keyword(s):  
Dna Synthesis ◽  
Mutational Analysis ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Rrna Genes ◽  
Hybrid Cells ◽  
The Common ◽  
Cellular Dna ◽  
Stimulation Of

The biological activity of several deletion mutants of simian virus 40, cloned in pBR322, was determined. Three functions of the simian virus 40 A gene were studied: (i) the ability to express T antigen; (ii) the ability to induce cell DNA replication; and (iii) the ability to reactivate silent rRNA genes in hybrid cells. Recombinant plasmid DNA was introduced into cells by manual microinjection or by transfection. The results (together with previous reports) indicate that the critical sequences for these three functions are located separately on the simian virus 40 A gene, as follows: (i) the sequences necessary for the detection of the common antigenic determinant of T antigen extend from nucleotide 4147 to nucleotide 4001 (map units 0.45 to 0.42); (ii) the sequences critical for the stimulation of cell DNA synthesis extend from nucleotide 4327 to nucleotide 4001 (map units 0.49 to 0.42); and (iii) those critical for the reactivation of rRNA genes extend approximately from nucleotide 3827 to nucleotide 3526 (map units 0.39 to 0.33).

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