scholarly journals Production of simian virus 40 large tumor antigen in bacteria: altered DNA-binding specificity and dna-replication activity of underphosphorylated large tumor antigen

1989 ◽  
Vol 86 (17) ◽  
pp. 6479-6483 ◽  
Author(s):  
I J Mohr ◽  
Y Gluzman ◽  
M P Fairman ◽  
M Strauss ◽  
D McVey ◽  
...  
Keyword(s):  
Tumor Antigen ◽  
Mammalian Cells ◽  
Expression System ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Origin Of Replication ◽  
Wild Type ◽  
Large Tumor ◽  
Large Tumor Antigen

A bacterial expression system was used to produce simian virus 40 large tumor antigen (T antigen) in the absence of the extensive posttranslational modifications that occur in mammalian cells. Wild-type T antigen produced in bacteria retained a specific subset of the biochemical activities displayed by its mammalian counterpart. Escherichia coli T antigen functioned as a helicase and bound to DNA fragments containing either site I or the wild-type origin of replication in a manner identical to mammalian T antigen. However, T antigen purified from E. coli did not efficiently bind to site II, an essential cis element within the simian virus 40 origin of replication. It therefore could not unwind origin-containing plasmids or efficiently replicate simian virus 40 DNA in vitro. The ability of protein phosphorylation to modulate the intrinsic preference of full-length T antigen for either site I or site II is discussed.

scholarly journals Simian virus 40 large tumor antigen is unable to transform mouse embryonic fibroblasts lacking type 1 insulin-like growth factor receptor

1993 ◽  
Vol 90 (23) ◽  
pp. 11217-11221 ◽  
Author(s):  
C Sell ◽  
M Rubini ◽  
R Rubin ◽  
J P Liu ◽  
A Efstratiadis ◽  
...  
Keyword(s):  
Growth Factor ◽  
Tumor Antigen ◽  
Simian Virus 40 ◽  
Soft Agar ◽  
Simian Virus ◽  
Wild Type ◽  
Large Tumor ◽  
Large Tumor Antigen ◽  
Igf I

Fibroblast cell lines were established from mouse embryos homozygous for a targeted disruption of the Igf1r gene, encoding the type 1 receptor for insulin-like growth factor I (IGF-I) and from their wild-type littermates. The cells from the wild-type embryos (W cells) grow in serum-free medium supplemented with platelet-derived growth factor, epidermal growth factor, and IGF-I, whereas the cells from Igf1r(-/-) embryos (R- cells) do not, although they grow at a reduced rate in 10% fetal calf serum. The simian virus 40 (SV40) large T antigen, expressed from a transfected plasmid, can transform W cells, which form foci in monolayer cultures and colonies in soft agar (anchorage-independent growth). In contrast, the SV40 large tumor antigen, although normally expressed from the transfected template, is unable to transform R- cells, which remain contact-inhibited and fail to grow in soft agar. The transformed phenotype is restored if the R- cells carrying the SV40 large tumor antigen are stably transfected with a plasmid expressing the human IGF-I receptor. These results demonstrate that signaling via the IGF-I receptor is an indispensable component of the SV40 transformation pathway. This conclusion is further supported from the results of antisense RNA experiments with tumor cell lines showing that interference with the function of the IGF-I receptor has a profound effect on anchorage-independent growth, even under conditions that only modestly affect growth in monolayers.

scholarly journals Nonselective expression of simian virus 40 large tumor antigen fragments in mouse cells.

1982 ◽  
Vol 79 (6) ◽  
pp. 2064-2067 ◽  
Author(s):  
V. B. Reddy ◽  
S. S. Tevethia ◽  
M. J. Tevethia ◽  
S. M. Weissman
Keyword(s):  
Tumor Antigen ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Large Tumor ◽  
Large Tumor Antigen ◽  
Mouse Cells

Differential roles of heat shock protein 70 in the in vitro nuclear import of glucocorticoid receptor and simian virus 40 large tumor antigen

1994 ◽  
Vol 14 (8) ◽  
pp. 5088-5098
Author(s):  
J Yang ◽  
D B DeFranco
Keyword(s):  
Heat Shock ◽  
Heat Shock Protein ◽  
Tumor Antigen ◽  
Nuclear Import ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Large Tumor ◽  
Large Tumor Antigen ◽  
Cell Cytosol

Nuclear import of glucocorticoid receptors (GRs) was analyzed in vitro with digitonin-permeabilized cells (S. A. Adam, R. Sterne-Marr, and L. Gerace, J. Cell Biol. 111:807-816, 1990). Indirect immunofluorescence methods were used to monitor the transport of GRs from rat hepatoma and fibroblast cell cytosol into HeLa nuclei. In vitro nuclear import of GRs was shown to be hormone dependent and to require ATP and incubation at ambient temperatures (i.e., 30 degrees C). Hormone-dependent dissociation of GR-bound proteins, such as the 90-kDa heat shock protein, hsp90, is part of an activation process that is obligatory for the expression of the receptor's DNA-binding activity. Inhibition of in vitro GR activation by Na2MoO4 blocked hormone-dependent nuclear import, demonstrating that receptor activation is required for nuclear import. The addition to GR-containing cytosol of antiserum directed against the cytosolic 70-kDa heat shock protein, hsp70, while effective in blocking the nuclear import of simian virus 40 large tumor antigen (SV40 TAg), did not affect hormone-dependent nuclear import of endogenous, full-length GRs or an exogenously added truncated GR protein (i.e., XGR556) that lacks a hormone-binding domain but possesses a constitutively active nuclear localization signal sequence (NLS). Depletion of hsp70 from HeLa cell cytosol did not affect the nuclear import of exogenously added XGR556 but led to inhibition of SV40 TAg nuclear import. Thus, two closely related NLSs, one contained within GRs and the other contained within SV40 TAg, are distinguished by their differential requirements for hsp70 in vitro.

scholarly journals Simian Virus 40 Large Tumor Antigen Modulates the Raf Signaling Pathway

2001 ◽  
Vol 276 (30) ◽  
pp. 27840-27845 ◽  
Author(s):  
Nicholas Grammatikakis ◽  
Katarzyna Jaronczyk ◽  
Aliki Siganou ◽  
Adina Vultur ◽  
Heather Lee Brownell ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Tumor Antigen ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Large Tumor ◽  
Large Tumor Antigen

scholarly journals Specific in vitro adenylylation of the simian virus 40 large tumor antigen.

1984 ◽  
Vol 81 (21) ◽  
pp. 6574-6578 ◽  
Author(s):  
M. K. Bradley ◽  
J. Hudson ◽  
M. S. Villanueva ◽  
D. M. Livingston
Keyword(s):  
Tumor Antigen ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Large Tumor ◽  
Large Tumor Antigen
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