scholarly journals Overproduction of protein p53 contributes to simian virus 40-mediated transformation.

1986 ◽  
Vol 6 (10) ◽  
pp. 3531-3536 ◽  
Author(s):  
D Michalovitz ◽  
D Eliyahu ◽  
M Oren
Keyword(s):  
Deletion Mutant ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Wild Type ◽  
Sv40 T Antigen ◽  
Rat Embryo ◽  
Focus Formation ◽  
Protein P53

The possible involvement of p53 overproduction in simian virus 40 (SV40)mediated transformation was studied by using the rat embryo fibroblast focus formation assay. Transformation by wild-type SV40 was enhanced two- to threefold by cotransfection of a plasmid overexpressing mouse p53. More significantly, such a plasmid could partially complement a transformation-defective deletion mutant of SV40. Hence, the ability of SV40 T antigen to induce high p53 levels may indeed be directly relevant to the viral transforming potential.

Overproduction of protein p53 contributes to simian virus 40-mediated transformation

1986 ◽  
Vol 6 (10) ◽  
pp. 3531-3536
Author(s):  
D Michalovitz ◽  
D Eliyahu ◽  
M Oren
Keyword(s):  
Deletion Mutant ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Wild Type ◽  
Sv40 T Antigen ◽  
Rat Embryo ◽  
Focus Formation ◽  
Protein P53

The possible involvement of p53 overproduction in simian virus 40 (SV40)mediated transformation was studied by using the rat embryo fibroblast focus formation assay. Transformation by wild-type SV40 was enhanced two- to threefold by cotransfection of a plasmid overexpressing mouse p53. More significantly, such a plasmid could partially complement a transformation-defective deletion mutant of SV40. Hence, the ability of SV40 T antigen to induce high p53 levels may indeed be directly relevant to the viral transforming potential.

scholarly journals Regions and Activities of Simian Virus 40 T Antigen That Cooperate with an Activated ras Oncogene in Transforming Primary Rat Embryo Fibroblasts

2002 ◽  
Vol 76 (7) ◽  
pp. 3145-3157 ◽  
Author(s):  
Tina M. Beachy ◽  
Sara L. Cole ◽  
Jane F. Cavender ◽  
Mary J. Tevethia
Keyword(s):  
Amino Acids ◽  
Simian Virus 40 ◽  
Suppressive Effect ◽  
Simian Virus ◽  
T Antigen ◽  
Wild Type ◽  
Rat Embryo ◽  
Specific Amino Acid ◽  
Antigen Fragment ◽  
Transcriptional Transactivator

ABSTRACT Prolonged expression of a ras oncogene in primary cells accelerates the natural process of senescence. This ras-induced permanent growth arrest is bypassed in cells expressing the simian virus 40 large T antigen. Previously we showed that two regions of T antigen, a region consisting of the N-terminal 147 amino acids and a region consisting of amino acids 251 to 708 (T251-708), independently overcome ras-induced senescence. Coexpression of either T-antigen fragment and Ras results in the appearance of dense foci of transformed cells. Using a series of mutants that produce shorter T-antigen fragments, we show that the C-terminal limit of the N-terminal T-antigen fragment that cooperates with Ras lies between amino acids 83 and 121. The N-terminal limit of the C-terminal T-antigen fragment lies between amino acids 252 and 271. In addition, we present evidence that cooperation between the N-terminal fragment and Ras depends upon an intact T-antigen J domain and the ability of the T antigen to bind and inactivate the growth-suppressive effect of the tumor suppressor Rb. Introduction of specific amino acid substitutions surrounding residue 400 into T251-708 prevented the fragment from cooperating with Ras. T251-708 proteins with these same substitutions inhibited the transcriptional transactivating potential of p53 as effectively as did the wild-type protein. Thus, at least one activity contained within T251-708, other than inactivating p53 as a transcriptional transactivator, is likely to be required to bypass Ras-induced senescence.

Less than 40% of the simian virus 40 large T-antigen-coding sequence is required for transformation

1984 ◽  
Vol 4 (8) ◽  
pp. 1661-1663
Author(s):  
L Sompayrac ◽  
K J Danna
Keyword(s):  
Dna Sequences ◽  
Deletion Mutant ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Large Deletion ◽  
T Antigen ◽  
Large T Antigen ◽  
Wild Type ◽  
Coding Sequence ◽  
Mouse Cells

F8dl is a simian virus 40 early-region deletion mutant that lacks the simian virus 40 DNA sequences between 0.168 and 0.424 map units. Despite this large deletion, cloned F8dl DNA transforms Fisher rat F111 cells and BALB/3T3 clone A31 mouse cells as efficiently as does cloned simian virus 40 wild-type DNA. These results indicate that less than 40% of the large T-antigen-coding sequence is required for efficient transformation.

scholarly journals Less than 40% of the simian virus 40 large T-antigen-coding sequence is required for transformation.

1984 ◽  
Vol 4 (8) ◽  
pp. 1661-1663 ◽  
Author(s):  
L Sompayrac ◽  
K J Danna
Keyword(s):  
Dna Sequences ◽  
Deletion Mutant ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Large Deletion ◽  
T Antigen ◽  
Large T Antigen ◽  
Wild Type ◽  
Coding Sequence ◽  
Mouse Cells

F8dl is a simian virus 40 early-region deletion mutant that lacks the simian virus 40 DNA sequences between 0.168 and 0.424 map units. Despite this large deletion, cloned F8dl DNA transforms Fisher rat F111 cells and BALB/3T3 clone A31 mouse cells as efficiently as does cloned simian virus 40 wild-type DNA. These results indicate that less than 40% of the large T-antigen-coding sequence is required for efficient transformation.

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.

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 Assembly of T-Antigen Double Hexamers on the Simian Virus 40 Core Origin Requires Only a Subset of the Available Binding Sites

1998 ◽  
Vol 18 (5) ◽  
pp. 2677-2687 ◽  
Author(s):  
Woo S. Joo ◽  
Henry Y. Kim ◽  
John D. Purviance ◽  
K. R. Sreekumar ◽  
Peter A. Bullock
Keyword(s):  
Structural Changes ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Wild Type ◽  
The Core ◽  
Structural Distortions ◽  
In The Wild ◽  
Sv40 Dna ◽  
Initial Assembly

ABSTRACT Initiation of simian virus 40 (SV40) DNA replication is dependent upon the assembly of two T-antigen (T-ag) hexamers on the SV40 core origin. To further define the oligomerization mechanism, the pentanucleotide requirements for T-ag assembly were investigated. Here, we demonstrate that individual pentanucleotides support hexamer formation, while particular pairs of pentanucleotides suffice for the assembly of T-ag double hexamers. Related studies demonstrate that T-ag double hexamers formed on “active pairs” of pentanucleotides catalyze a set of previously described structural distortions within the core origin. For the four-pentanucleotide-containing wild-type SV40 core origin, footprinting experiments indicate that T-ag double hexamers prefer to bind to pentanucleotides 1 and 3. Collectively, these experiments demonstrate that only two of the four pentanucleotides in the core origin are necessary for T-ag assembly and the induction of structural changes in the core origin. Since all four pentanucleotides in the wild-type origin are necessary for extensive DNA unwinding, we concluded that the second pair of pentanucleotides is required at a step subsequent to the initial assembly process.

scholarly journals Differential ability of a T-antigen transport-defective mutant of simian virus 40 to transform primary and established rodent cells.

1985 ◽  
Vol 5 (5) ◽  
pp. 1043-1050 ◽  
Author(s):  
R E Lanford ◽  
C Wong ◽  
J S Butel
Keyword(s):  
Cell Lines ◽  
Mouse Embryo ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Wild Type ◽  
Mouse Embryo Fibroblasts ◽  
Established Cell Lines ◽  
Established Cell ◽  
Embryo Fibroblasts

The transforming potential and oncogenicity of a simian virus 40 (SV40) mutant affecting T-antigen (T-ag), SV40(cT)-3, was examined in an effort to dissect T-ag functions in transformation. SV40(cT)-3 has a point mutation at nucleotide 4434 that abolishes the transport of T-ag to the nucleus but does not affect its association with the cell surface. Transfection-transformation assays were performed with primary cells and established cell lines of mouse and rat origin. The efficiency of transformation for established cell lines by SV40(cT)-3 was comparable to that of wild-type SV40, indicating that transformation of established cell lines can occur in the absence of detectable amounts of nuclear T-ag. Transformation of primary mouse embryo fibroblasts by SV40(cT)-3 was markedly influenced by culture conditions; the relative transforming frequency was dramatically reduced in assays involving focus formation in low serum concentrations or anchorage-independent growth. Immunofluorescence tests revealed that the transformed mouse embryo fibroblasts partially transport the mutant cT-ag to the cell nucleus. Transformed cell lines induced by SV40(cT)-3 did not differ in growth properties from wild-type transformants. SV40(cT)-3 was completely defective for the transformation of primary baby rat kidney cells, a primary cell type unable to transport the mutant T-ag to the nucleus. The intracellular localization of cellular protein p53 was found to mimic T-ag distribution in all the transformants analyzed. The mutant virus was weakly oncogenic in vivo: the induction of tumors in newborn hamsters by SV40(cT)-3 was reduced in incidence and delayed in appearance in comparison to wild-type SV40. These observations suggest that cellular transformation is regulated by both nuclear and surface-associated forms of SV40 T-ag.

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