DNA sequences of polyoma virus early deletion mutants

Smolar, Nina; Griffin, Beverly E.

doi:10.1128/jvi.38.3.958-967.1981

Cited by 50 publications

(29 citation statements)

References 44 publications

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“…In the present work, this result was confirmed with the aPy MT7 antibody. It is interesting that although the dl-23 middle T-antigen polypeptide lacks the tyrosine residue (Smolar and Griffin, 1981) previously shown to be phosphorylated in the protein kinase reaction (Schaffhausen and Benjamin, 1981), it is still phosphorylated on a tyrosine residue. This suggest that there is more than one site of tyrosine phosphorylation on the middle T-antigen molecule, or that an alternative site can be used in the absence of the normal phosphorylation site.…”

Section: Discussionmentioning

confidence: 97%

Protein kinase activities associated with distinct antigenic forms of polyoma virus middle T-antigen.

Sm¹

1982

The EMBO Journal

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The tyrosine‐specific protein kinase activity previously described in T‐antigens of polyoma virus immunoprecipitated with anti‐tumour sera has been investigated using monoclonal antibodies. This activity is associated with middle T‐antigen but it can be separated by selective antibody precipitation from the majority of this protein. The difference between active and inactive forms can be accounted for by an antigenic difference at the N terminus of middle T‐antigen molecules. Moreover, the two different mol. wt. forms of middle T‐antigen that can act as phosphoacceptors have been separated by antibody precipitation and therefore shown to be immunologically distinct. The binding position of the antibody used for immunoprecipitation has been observed to have a quantitative influence on the in vitro protein kinase reaction, in one case appearing to stimulate the activity. The detection of the in vitro protein kinase activity in immunoprecipitates obtained with several different monoclonal antibodies directed against the middle T‐antigen indicates that the activity is a property tightly associated with this polyoma virus‐coded protein.

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Section: Discussionmentioning

confidence: 97%

Protein kinase activities associated with distinct antigenic forms of polyoma virus middle T-antigen.

Sm¹

1982

The EMBO Journal

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“…These results suggest that either Py-encoded MTAg or small TAg might be responsible for the observed increase in pp6OC-"' kinase activity. Since the d123 mutant encodes a normal small TAg [17,18], which is synthesized at approximately the same level as wt-encoded small TAg in infected cells, the low level of pp60c-src kinase stimulation in d 123-infected MEC suggests that MTAg synthesis is responsible for the increased pp60'-"'" kinase activity. The lack of early pp60'-"" kinase activity stimulation of NG 18-infected cells further argues that this increased activity is not a nonspecific response to virus infection or the conditions utilized for virus adsorption in our experiments.…”

Section: Discussionmentioning

confidence: 99%

Stimulation of pp60^c‐src tyrosyl kinase activity in polyoma virus–infected mouse cells is closely associated with polyoma middle tumor antigen synthesis

Bolen

Lewis

Israel

1985

J of Cellular Biochemistry

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We have examined the effect of polyoma virus infection of primary mouse embryo cells on the tyrosyl kinase activity associated with the cellular src gene product, pp60c-src. The results of our studies demonstrate that infection of mouse cells with wild-type polyoma virus or viral mutants capable of transforming rodent cells in culture and inducing tumors in animals results in the stimulation of pp60c-src tyrosyl kinase activity. The level of pp60c-src kinase stimulation in infected cells was found to be proportional to both the oncogenic potential of the virus strain used for infection and the characteristic phenotype of rodent cells transformed by the various strains of polyoma virus. Stimulation of pp60c-src kinase activity was not observed in mouse cells infected with transformation-defective strains of polyoma virus. In examining the kinetics of pp60c-src kinase stimulation in mouse cells at various times following wild-type polyoma virus infection, we found that the level of pp60c-src kinase activity correlated directly with the synthesis of polyoma virus-encoded tumor antigens. By comparing wild-type polyoma virus with other viral mutants in these experiments, we conclude that the stimulation of pp60c-src kinase activity in mouse cells following polyoma virus infection is associated with the synthesis of middle tumor antigen.

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“…Two proteins with molecular masses of 36 and 63 kilodaltons (kDa) present in MTAg immunoprecipitates have been recently determined to be the catalytic and regulatory subunits of protein phosphatase 2a (37). Again, genetic analysis suggests that the presence of these proteins is necessary but TRANSFORMATION-DEFECTIVE MIDDLE T ANTIGEN MUTANT not sufficient for transformation by MTAg (19,30,35,41,45). However, this conclusion is based on data regarding the association of the 36and 63-kDa proteins with various MTAg mutants, rather than measurements of phosphatase activity.…”

Section: * Corresponding Authormentioning

confidence: 99%

A completely transformation-defective point mutant of polyomavirus middle T antigen which retains full associated phosphatidylinositol kinase activity

Druker

Ling

Cohen

et al. 1990

J Virol

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By using a random mutagenesis procedure combined with a recombinant retrovirus vector, mutants of polyomavirus middle T antigen (MTAg) were generated. Three new MTAg mutants with various degrees of transformation competence were more thoroughly characterized. All of the mutants produced a stable MTAg, as assessed by metabolic labeling or immunoblotting, and each mutant possessed wild-type levels of associated tyrosine kinase activity and associated phosphatidylinositol-3 (PI-3) kinase activity. One of these mutants, with a substitution of leucine for proline at amino acid 248 of MTAg (248m) was completely transformation defective, as measured in a focus-forming assay. Furthermore, the pattern of phosphorylation of 248m in vivo was identical to that of wild-type MTAg, and the kinetics of association of MTAg with an 85-kilodalton protein, the putative PI kinase, was not altered. Similarly, the pattern of PI derivatives obtained in an in vitro kinase assay was not altered by the substitution at amino acid 248. Since the single base pair mutation at amino acid 248 resulted in an MTAg that was completely transformation defective despite possessing wild-type levels of kinase activities, this suggests that neither tyrosine kinase nor PI-3 kinase activity nor the combination of both are sufficient for transformation by MTAg.on July 6, 2020 by guest

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DNA sequences of polyoma virus early deletion mutants

Cited by 50 publications

References 44 publications

Protein kinase activities associated with distinct antigenic forms of polyoma virus middle T-antigen.

Protein kinase activities associated with distinct antigenic forms of polyoma virus middle T-antigen.

Stimulation of pp60^c‐src tyrosyl kinase activity in polyoma virus–infected mouse cells is closely associated with polyoma middle tumor antigen synthesis

A completely transformation-defective point mutant of polyomavirus middle T antigen which retains full associated phosphatidylinositol kinase activity

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DNA sequences of polyoma virus early deletion mutants

Cited by 50 publications

References 44 publications

Protein kinase activities associated with distinct antigenic forms of polyoma virus middle T-antigen.

Protein kinase activities associated with distinct antigenic forms of polyoma virus middle T-antigen.

Stimulation of pp60c‐src tyrosyl kinase activity in polyoma virus–infected mouse cells is closely associated with polyoma middle tumor antigen synthesis

A completely transformation-defective point mutant of polyomavirus middle T antigen which retains full associated phosphatidylinositol kinase activity

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Stimulation of pp60^c‐src tyrosyl kinase activity in polyoma virus–infected mouse cells is closely associated with polyoma middle tumor antigen synthesis