Functions of T antigens of SV40 and polyomavirus

Hand, Roger

doi:10.1016/0304-419x(81)90002-0

Cited by 17 publications

(15 citation statements)

References 150 publications

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“…(However, there are other experiments which can imply that transformation and T antigen synthesis in certain cases may be uncoupled from DNA synthesis [114]). There are recent reviews on SV40 cell biology which use discernment and carefully evaluate the conditions for the experimental data, define how the term "transformation" is being used, and are explicit or cautious when they discuss experiments or expectations extending findings to tumorigenicity [37,66]. Thus experiments can be unambiguously and properly interpreted, only when the authors carefully define their use of the term cellular "transformation".…”

Section: Changes In 7issuementioning

confidence: 98%

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The immunopathology of SV40-induced transformation

Mora

1982

Springer Semin Immunopathol

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Section: Changes In 7issuementioning

confidence: 98%

“…I will conclude with a generally critical assessment but also with a very broad suggestion for extending one particular study, which may turn out to be of interest to immunologically oriented research clinicians. Some of the topics were reviewed recently [5,20,37,44,57,66,99,103,106, and especially 108].…”

mentioning

confidence: 99%

The immunopathology of SV40-induced transformation

Mora

1982

Springer Semin Immunopathol

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“…The SV40 small tantigen seems to act mainly as a tumor promoter. The large T-antigen, with an apparent molecular weight (Mr) of 88,000 (88K), is involved in multiple functions during both the lytic cycle and cell transformation (for reviews see references 12 and 18). Large T-antigen, particularly in transformed cells, forms specific heteropolymeric complexes with cellular 48K to 55K phosphoproteins, designated p53 proteins.…”

mentioning

confidence: 99%

Protein kinase activities in immune complexes of simian virus 40 large T-antigen and transformation-associated cellular p53 protein.

Roy¹,

Fransen²,

Fiers³

1984

Mol. Cell. Biol.

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Immune complex kinase assays in the simian virus 40 system were performed by incubation of immunoprecipitates containing tumor antigens with [-y-32P]ATP, followed by analysis of any phosphoacceptor proteins. These assays yielded mainly the viral large T-antigen and, in particular, the associated cellular p53 as endogenous substrates. The nature of these substrates was confirmed by proteolysis techniques. Under specific conditions, casein could be used as an exogenous substrate as well. The kinase reactions showed preference for ATP and MgCl2 instead of GTP or MnCl2. Both phosphoserine and phosphothreonine, but in no case phosphotyrosine, were detected after an immune complex kinase reaction. Apparently, several in vivo phosphorylation sites were recognized in vitro in both large T-antigen and p53, but the presence of some artifactual sites could not be completely excluded. Although contaminating kinases were detectable in the immune complexes, at least the p53 molecules were phosphorylated in vitro in a more specific way. This followed from several characteristics of the immune complex kinase reactions and especially from the strong inhibition of p53 phosphorylation by two anti-large-T monoclonal antibodies. It was shown that large T-antigen showed associated kinase activity, although none of our results could unambiguously demonstrate an intrinsic kinase activity of this protein. Finally, anti-p53 monoclonal antibodies only slightly affected in vitro phosphorylation reactions, whereas a p53 molecule from a simian virus 40-free, chemically transformed human cell line was not phosphorylated in vitro under any condition tested. Thus, it is highly unlikely that the p53 molecule per se carries intrinsic or even associated kinase activities.

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“…1) [9, for reviews see refs. 7,8]. There are two possible hypotheses for this difference: (1) SV40 induces cellular DNA synthesis by a mechanism different from that of serum-induced DNA synthesis, and (2) SV40 induces cellular DNA synthesis by a mechanism similar to that of serum induction, and the differences in lag time is due to the difference in strength of the driv ing force between them (just like a difference in serum concentration).…”

mentioning

confidence: 99%

“…These cells also are induced to enter S phase when infected with SV40, and the ex pression of T antigen is required for the in duction [for reviews, see refs. 7,8]. The effects of external factors after SV40 infection on the interval between T antigen expression and entry into S phase have been reported.…”

mentioning

confidence: 99%

Deeper ‘GO’ Phase in Rat Fibroblasts Affects the Lag Time Required for T Antigen Induced DNA Synthesis, but not the Lag Time Required for SV40 T Antigen Expression

Zaitsu¹,

Kimura²

1989

Intervirology

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In density-arrested rat 3YltsG125 cells, the time required for entry into S phase after serum stimulation is prolonged with increase in duration of the arrest. When these cells were infected with simian virus 40, the time required for expression of T antigen did not change, but the time required for entry into S phase was prolonged with increase in duration of the arrest. The extent of prolongation of the interval between T antigen expression and entry into S phase correlated well with the extent of the prolongation detected with serum stimulation. These observations suggest that: (1) expression of T antigen was not affected by the level of cellular preparedness for entry into S phase, i.e., it did not depend on cellular functions directly involved in the preparedness, and (2) T antigen induced cellular DNA synthesis, at least in part, by a mechanism similar to that of serum-induced DNA synthesis.

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Functions of T antigens of SV40 and polyomavirus

Cited by 17 publications

References 150 publications

The immunopathology of SV40-induced transformation

The immunopathology of SV40-induced transformation

Protein kinase activities in immune complexes of simian virus 40 large T-antigen and transformation-associated cellular p53 protein.

Deeper ‘GO’ Phase in Rat Fibroblasts Affects the Lag Time Required for T Antigen Induced DNA Synthesis, but not the Lag Time Required for SV40 T Antigen Expression

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