scholarly journals Phosphate and the regulation of DNA replication in normal and virus-transformed 3T3 cells

1983 ◽  
Vol 214 (3) ◽  
pp. 695-702 ◽  
Author(s):  
W Engström ◽  
A Zetterberg
Keyword(s):  
Dna Synthesis ◽  
Time Course ◽  
Simian Virus 40 ◽  
Complete Removal ◽  
Simian Virus ◽  
Phosphate Concentration ◽  
Serum Starvation ◽  
Cell Multiplication ◽  
Inhibitory Effects ◽  
3T3 Cells

3T3 cells were cultured in media with different phosphate concentrations and the effects on DNA synthesis were examined. Even a modest phosphate depletion markedly inhibited DNA synthesis and cell multiplication in proliferating cultures. Furthermore, the decrease in the proportion of DNA-synthesizing cells observed after phosphate starvation followed the same time-course as the decrease seen after serum starvation. Cells starved to quiescence in a medium with a 100-fold decrease in phosphate concentration remained viable but non-proliferating for up to 3 weeks, i.e. they had entered a state of quiescence comparable with that seen after serum starvation. Addition of phosphate to phosphate-depleted cultures restored DNA synthesis within 24h. Furthermore, the kinetics of [3H]thymidine labelling after phosphate addition were nearly identical with the labelling kinetics following addition of serum to serum-depleted cultures. In contrast, phosphate deprivation had no inhibitory effects on DNA synthesis in simian-virus-40-transformed 3T3 cells. Furthermore, the inhibitory effects on DNA synthesis in such cells caused by a complete removal of serum could not be further enhanced by decreasing the phosphate concentration in the culture medium.

scholarly journals Quantitative correlation between simian virus 40 T-antigen synthesis and late viral gene expression in permissive and nonpermissive cells

1978 ◽  
Vol 77 (1) ◽  
pp. R1 ◽  
Author(s):  
A Graessmann ◽  
M Graessmann ◽  
E Guhl ◽  
C Mueller
Keyword(s):  
Time Course ◽  
Viral Gene Expression ◽  
Simian Virus 40 ◽  
Threshold Value ◽  
Simian Virus ◽  
T Antigen ◽  
Threshold Concentration ◽  
Viral Gene ◽  
3T3 Cells ◽  
V Antigen

The time-course of intranuclear Simian virus 40 (SV40) tumor (T) antigen synthesis and accumulation in permissive CV1 monkey cells and nonpermissive 3T3 mouse cells has been studied by immunofluorescence and cytofluorometry. CV1 cells accumulate T antigen continuously over a period of 48 h after infection, whereas in 3T3 cells the T-antigen content remains about constant and at a comparatively low level. Only those CV1 cells which have attained a threshold concentration of intranuclear T antigen synthesize viral capsid proteins (V antigen). In nonpermissive 3T3 cells, the T-antigen threshold value for the onset of V-antigen synthesis is higher than in CV1 cells and is never reached by infected cells. However, 3T3 cells microinjected with sufficient amounts of SV40 DNA easily surpass this value and behave permissively.

scholarly journals Genetic evidence that acute morphologic transformation, induction of cellular DNA synthesis, and focus formation are mediated by a single activity of the bovine papillomavirus E5 protein.

1989 ◽  
Vol 9 (12) ◽  
pp. 5563-5572 ◽  
Author(s):  
J Settleman ◽  
A Fazeli ◽  
J Malicki ◽  
B H Horwitz ◽  
D DiMaio
Keyword(s):  
Dna Synthesis ◽  
Mutational Analysis ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Serum Starvation ◽  
Bovine Papillomavirus ◽  
Focus Formation ◽  
E5 Protein ◽  
Cellular Dna

The bovine papillomavirus (BPV) type 1 E5 gene encodes a 44-amino-acid protein that can stably transform cultured rodent cells when expressed in the absence of all other viral genes. We have previously constructed a BPV-simian virus 40 recombinant virus (Pava-1) which efficiently expresses the BPV type 1 E5 gene in infected cells (J. Settleman and D. DiMaio, Proc. Natl. Acad. Sci. USA 85:9007-9011, 1988). Within 48 h of Pava-1 infection, the vast majority of mouse C127 cells underwent a dramatic morphologic transformation which was accompanied by cell proliferation. Infection of C127 cells made quiescent by contact inhibition and serum starvation caused a great induction of cellular DNA synthesis. These morphologic and mitogenic responses were proportional to the virus multiplicity of infection. Mutational analysis indicated that the E5 gene is both necessary and sufficient for these activities. Analysis of a variety of E5 missense mutants revealed a strong correlation between their phenotypes in the acute transformation assays following infection and in the stable focus-forming assay following transfection. Most of the defective mutants expressed normal levels of E5 protein following infection, indicating that their defective phenotypes are not due to the synthesis of an unstable protein. The failure to genetically resolve these E5 activities suggests that the ability of the E5 protein to cause acute morphologic transformation and reentry into the cell cycle may be intimately related to its ability to cause stable cell transformation and that these functions are probably mediated by a single biochemical activity of the E5 protein.

Genetic evidence that acute morphologic transformation, induction of cellular DNA synthesis, and focus formation are mediated by a single activity of the bovine papillomavirus E5 protein

1989 ◽  
Vol 9 (12) ◽  
pp. 5563-5572
Author(s):  
J Settleman ◽  
A Fazeli ◽  
J Malicki ◽  
B H Horwitz ◽  
D DiMaio
Keyword(s):  
Dna Synthesis ◽  
Mutational Analysis ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Serum Starvation ◽  
Bovine Papillomavirus ◽  
Focus Formation ◽  
E5 Protein ◽  
Cellular Dna

The bovine papillomavirus (BPV) type 1 E5 gene encodes a 44-amino-acid protein that can stably transform cultured rodent cells when expressed in the absence of all other viral genes. We have previously constructed a BPV-simian virus 40 recombinant virus (Pava-1) which efficiently expresses the BPV type 1 E5 gene in infected cells (J. Settleman and D. DiMaio, Proc. Natl. Acad. Sci. USA 85:9007-9011, 1988). Within 48 h of Pava-1 infection, the vast majority of mouse C127 cells underwent a dramatic morphologic transformation which was accompanied by cell proliferation. Infection of C127 cells made quiescent by contact inhibition and serum starvation caused a great induction of cellular DNA synthesis. These morphologic and mitogenic responses were proportional to the virus multiplicity of infection. Mutational analysis indicated that the E5 gene is both necessary and sufficient for these activities. Analysis of a variety of E5 missense mutants revealed a strong correlation between their phenotypes in the acute transformation assays following infection and in the stable focus-forming assay following transfection. Most of the defective mutants expressed normal levels of E5 protein following infection, indicating that their defective phenotypes are not due to the synthesis of an unstable protein. The failure to genetically resolve these E5 activities suggests that the ability of the E5 protein to cause acute morphologic transformation and reentry into the cell cycle may be intimately related to its ability to cause stable cell transformation and that these functions are probably mediated by a single biochemical activity of the E5 protein.

Replication of cloned DNA containing the Alu family sequence during cell extract-promoting simian virus 40 DNA synthesis

1984 ◽  
Vol 4 (8) ◽  
pp. 1476-1482
Author(s):  
H Ariga
Keyword(s):  
Dna Replication ◽  
Dna Synthesis ◽  
Rna Polymerase Iii ◽  
Simian Virus 40 ◽  
Cell Extract ◽  
Simian Virus ◽  
T Antigen ◽  
Sv40 T Antigen ◽  
Sv40 Dna

The replicating activity of several cloned DNAs containing putative origin sequences was examined in a cell-free extract that absolutely depends on simian virus 40 (SV40) T antigen promoting initiation of SV40 DNA replication in vitro. Of the three DNAs containing the human Alu family sequence (BLUR8), the origin of (Saccharomyces cerevisiae plasmid 2 micron DNA (pJD29), and the yeast autonomous replicating sequence (YRp7), only BLUR8 was active as a template. Replication in a reaction mixture with BLUR8 as a template was semiconservative and not primed by a putative RNA polymerase III transcript synthesized on the Alu family sequence in vitro. Pulse-chase experiments showed that the small-sized DNA produced in a short-term incubation was converted to full-length closed circular and open circular DNAs in alkaline sucrose gradients. DNA synthesis in extracts began in a region of the Alu family sequence and was inhibited 80% by the addition of anti-T serum. Furthermore, partially purified T antigen bound the Alu family sequence in BLUR8 by the DNA-binding immunoassay. These results suggest that SV40 T antigen recognizes the Alu family sequence, similar to the origin sequence of SV40 DNA, and initiates semiconservative DNA replication in vitro.

Induction of cellular deoxyribonucleic acid synthesis in butyrate-treated cells by simian virus 40 deoxyribonucleic acid

1981 ◽  
Vol 1 (11) ◽  
pp. 1038-1047
Author(s):  
S Kawasaki ◽  
L Diamond ◽  
R Baserga
Keyword(s):  
Ribonucleic Acid ◽  
Deoxyribonucleic Acid ◽  
Simian Virus 40 ◽  
Acid Synthesis ◽  
Simian Virus ◽  
S Phase ◽  
Temperature Sensitive ◽  
3T3 Cells ◽  
Deoxyribonucleic Acid Synthesis ◽  
G1 Cells

Sodium butyrate (3 mM) inhibited the entry into the S phase of quiescent 3T3 cells stimulated by serum, but had no effect on the accumulation of cellular ribonucleic acid. Simian virus 40 infection or manual microinjection of cloned fragments from the simian virus 40 A gene caused quiescent 3T3 cells to enter the S phase even in the presence of butyrate. NGI cells, a line of 3T3 cells transformed by simian virus 40, grew vigorously in 3 mM butyrate. Homokaryons were formed between G1 and S-phase 3T3 cells, Butyrate inhibited the induction of deoxyribonucleic acid synthesis that usually occurs in B1 nuclei when G1 cells are fused with S-phase cells. However, when G1 3T3 cells were fused with exponentially growing NGI cells, the 3T3 nuclei were induced to enter deoxyribonucleic acid synthesis. In tsAF8 cells, a ribonucleic acid polymerase II mutant that stops in the G1 phase of the cell cycle, no temporal sequence was demonstrated between the butyrate block and the temperature-sensitive block. These results confirm previous reports that certain virally coded proteins can induce cell deoxyribonucleic acid synthesis in the absence of cellular functions that are required by serum-stimulated cells. Our interpretation of these data is that butyrate inhibited cell growth by inhibiting the expression of genes required for the G0 leads to G1 leads to S transition and that the product of the simian virus 40 A gene overrode this inhibition by providing all of the necessary functions for the entry into the S phase.

scholarly journals Binding of a sequence-specific single-stranded DNA-binding factor to the simian virus 40 core origin inverted repeat domain is cell cycle regulated.

1993 ◽  
Vol 13 (1) ◽  
pp. 408-420 ◽  
Author(s):  
E P Carmichael ◽  
J M Roome ◽  
A F Wahl
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Dna Binding ◽  
Dna Synthesis ◽  
Inverted Repeat ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Single Stranded Dna ◽  
Repeat Domain

The inverted repeat domain (IR domain) within the simian virus 40 origin of replication is the site of initial DNA melting prior to the onset of DNA synthesis. The domain had previously been shown to be bound by a cellular factor in response to DNA damage. We demonstrate that two distinct cellular components bind opposite strands of the IR domain. Replication protein A (RPA), previously identified as a single-stranded DNA binding protein required for origin-specific DNA replication in vitro, is shown to have a preference for the pyrimidine-rich strand. A newly described component, IR factor B (IRF-B), specifically recognizes the opposite strand. IRF-B binding activity in nuclear extract varies significantly with cell proliferation and the cell cycle, so that binding of IRF-B to the IR domain is negatively correlated with the onset of DNA synthesis. Loss of IRF-B binding from the nucleus also occurs in response to cellular DNA damage. UV cross-linking indicates that the core binding component of IRF-B is a protein of ca. 34 kDa. We propose that RPA and IRF-B bind opposite strands of the IR domain and together may function in the regulation of origin activation.

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