Characterization of an Immunologically Distinct Population of Simian Virus 40 Large Tumor Antigen

Covey, Lori R.; Kwok, Perry; Prives, Carol

doi:10.1007/978-1-4613-2087-6_8

Cited by 2 publications

(3 citation statements)

References 55 publications

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“…T antigen undergoes several modifications after translation, which are believed to result in functionally distinct forms of the protein (see reference 10 for a review). T-antigen-specific MAbs have been used to identify different forms of T antigen enriched for different activities in vitro (10,13,28,32,33). We used 10 of these MAbs (PAbs 100, 101, 103, 104, 105, 106, 107, 108, 109, and 416) to determine whether expression of a particular form of T antigen might correlate with SV40 DNA replication in A172 cells.…”

Section: Resultsmentioning

confidence: 99%

“…T antigen is known to undergo several posttranslational modifications and T-antigen-specific MAbs have been used to identify and characterize structurally and functionally distinct forms of T antigen. Those studies distinguished newly synthesized and old T antigen and identified forms active in origin binding and forms that are free or associated with replicating or mature SV40 chromosomes (10,28,(32)(33)(34).…”

Section: Discussionmentioning

confidence: 99%

“…We wanted to determine whether SV40 DNA replication in individual A172 cells might correlate with the expression of a particular subclass of T antigen. For this purpose, we obtained a panel of 10 T-antigen-specific monoclonal antibodies (MAbs) which have been used to identify and partially characterize structurally and functionally distinct forms of SV40 T antigen (10,13,28,32,33). We found that 9 of the 10 MAbs reacted with approximately the same percentage of infected A172 cells, always in excess of the percentage replicating viral DNA.…”

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confidence: 99%

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Simian virus 40 DNA replication correlates with expression of a particular subclass of T antigen in a human glial cell line

Deminie

Norkin

1990

J Virol

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Immunocytochemistry and in situ hybridization were used to identify simian virus 40 (SV40) large T-antigen expression and viral DNA replication in individual cells of infected semipermissive human cell lines. SV40 infection aborts before T-antigen expression in many cells of each of the human cell lines examined. In all but one of the human cell lines, most of the T-antigen-producing cells replicated viral DNA. However, in the A172 line of human glial cells only a small percentage of the T-antigen-expressing cells replicated viral DNA. Since different structural and functional classes of T antigen can be recognized with anti-T monoclonal antibodies, we examined infected A172 cells with a panel of 10 anti-T monoclonal antibodies to determine whether viral DNA replication might correlate with the expression of a particular epitope of T antigen. One anti-T monoclonal antibody, PAb 100, did specifically recognize that subset of A172 cells which replicated SV40 DNA. The percentage of PAb 100-reactive A172 cells was dramatically increased by the DNA synthesis inhibitors hydroxyurea and aphidicolin. Removal of the hydroxyurea was followed by an increase in the percentage of cells replicating viral DNA corresponding to the increased percentage reactive with PAb 100. The pattern of SV40 infection in A172 cells was not altered by infection with viable viral mutants containing lesions in the small t protein, the agnoprotein, or the enhancer region. Finally, in situ hybridization was used to show that the percentage of human cells expressing T antigen was similar to the percentage transcribing early SV40 mRNA. Thus, the block to T-antigen expression in human cells is at a stage prior to transcription of early SV40 mRNA.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Simian virus 40 DNA replication correlates with expression of a particular subclass of T antigen in a human glial cell line

Deminie

Norkin

1990

J Virol

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Helicase, DNA-binding, and immunological properties of replication-defective simian virus 40 mutant T antigens

Auborn

Guo

Prives

1989

J Virol

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Simian virus 40 T antigen (TAg) exhibits nonspecific and origin-specific DNA binding (ori binding) and ATPase and helicase activities, all of which are related to its roles in viral DNA replication. We have characterized some of the properties of four replication-defective but transformation-competent mutant TAgs, C6-2, T22, Cil, and C8A. C6-2 and T22 TAgs were each previously determined to lack ori-binding properties, while Cll TAg was reported to lack ATPase activity. The C8A TAg did not exhibit defects in either ori-binding or ATPase functions. We have analyzed additional aspects of these mutant TAgs pertaining to their helicase, DNA-binding, and immunological properties. With the exception of the C11 TAg, all the other TAgs exhibited helicase activity. The lack of helicase activity by Cll TAg was consistent with its previously shown inability to hydrolyze ATP or to replicate viral DNA. These results therefore show that on-binding and helicase activities are separate functions of TAg. Wild-type and mutant TAgs bound with similar efficiency to either native or denatured calf thymus DNA-cellulose, indicating no marked differences in their nonspecific DNA-binding properties. We also tested the binding of wild-type and mutant TAgs to a monoclonal antibody, PAb 100, that was previously shown to recognize an extremely small class of TAg that may represent a unique conformational form of the protein. Interestingly, while less than 10% of the wild-type, C6-2, Cll, and T22 mutant TAgs were recognized by PAb 100, more than 60% of the C8A mutant TAg was bound by this antibody. Therefore, although no defect in biochemical function was observed with the C8A TAg, its deficiency in viral DNA replication may be related to an unusual conformation, as detected by its dramatically increased recognition by PAb 100. These results show that the helicase activity of TAg is not required for its transformation function.

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Characterization of an Immunologically Distinct Population of Simian Virus 40 Large Tumor Antigen

Cited by 2 publications

References 55 publications

Simian virus 40 DNA replication correlates with expression of a particular subclass of T antigen in a human glial cell line

Simian virus 40 DNA replication correlates with expression of a particular subclass of T antigen in a human glial cell line

Helicase, DNA-binding, and immunological properties of replication-defective simian virus 40 mutant T antigens

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