scholarly journals DNA-binding properties of simian virus 40 T-antigen mutants defective in viral DNA replication.

1983 ◽  
Vol 3 (11) ◽  
pp. 1958-1966 ◽  
Author(s):  
C Prives ◽  
L Covey ◽  
A Scheller ◽  
Y Gluzman
Keyword(s):  
Amino Acid ◽  
Dna Sequences ◽  
Simian Virus 40 ◽  
Amino Acid Position ◽  
Simian Virus ◽  
T Antigen ◽  
Regulatory Sequences ◽  
Viral Dna ◽  
Viral Origin ◽  
Specific Affinity

Three simian virus 40 (SV40)-transformed monkey cell lines, C2, C6, and C11, producing T-antigen variants that are unable to initiate viral DNA replication, were analyzed with respect to their affinity for regulatory sequences at the viral origin of replication. C2 and C11 T antigens both bound specifically to sequences at sites 1 and 2 at the viral origin region, whereas C6 T antigen showed no specific affinity for any viral DNA sequences under all conditions tested. Viral DNA sequences encoding the C6 T antigen have recently been cloned out of C6 cells and used to transform an established rat cell line. T antigen from several cloned C6-SV40-transformed rat lines failed to bind specifically to the origin. C6 DNA contains three mutations: two located close to the amino terminus of T antigen at amino acid positions 30 and 51 and a third located internally at amino acid position 153. Two recombinant SV40 DNA mutants were prepared containing either the amino-terminal mutations at positions 30 and 51 (C6-1) or the internally located mutation at position 153 (C6-2) and used to transform Rat 2 cells. Whereas T antigen from C6-2-transformed cells lacked any specific affinity for these sequences. Therefore, the single mutation at amino acid position 153 (Asn leads to Thr) is sufficient to abolish the origin-binding property of T antigen. A T antigen-specific monoclonal antibody, PAb 100, which had been previously shown to immunoprecipitate an immunologically distinct origin-binding subclass of T antigen, recognized wild-type or C6-1 antigens, but failed to react with C6 or C6-2 T antigens. These results indicate that viral replication function comprises properties of T antigen that exist in addition to its ability to bind specifically to the SV40 regulatory sequences. Furthermore, it is concluded from these data that specific viral origin binding is not a necessary feature of the transforming function of T antigen.

DNA-binding properties of simian virus 40 T-antigen mutants defective in viral DNA replication

1983 ◽  
Vol 3 (11) ◽  
pp. 1958-1966
Author(s):  
C Prives ◽  
L Covey ◽  
A Scheller ◽  
Y Gluzman
Keyword(s):  
Amino Acid ◽  
Dna Sequences ◽  
Simian Virus 40 ◽  
Amino Acid Position ◽  
Simian Virus ◽  
T Antigen ◽  
Regulatory Sequences ◽  
Viral Dna ◽  
Viral Origin ◽  
Specific Affinity

Three simian virus 40 (SV40)-transformed monkey cell lines, C2, C6, and C11, producing T-antigen variants that are unable to initiate viral DNA replication, were analyzed with respect to their affinity for regulatory sequences at the viral origin of replication. C2 and C11 T antigens both bound specifically to sequences at sites 1 and 2 at the viral origin region, whereas C6 T antigen showed no specific affinity for any viral DNA sequences under all conditions tested. Viral DNA sequences encoding the C6 T antigen have recently been cloned out of C6 cells and used to transform an established rat cell line. T antigen from several cloned C6-SV40-transformed rat lines failed to bind specifically to the origin. C6 DNA contains three mutations: two located close to the amino terminus of T antigen at amino acid positions 30 and 51 and a third located internally at amino acid position 153. Two recombinant SV40 DNA mutants were prepared containing either the amino-terminal mutations at positions 30 and 51 (C6-1) or the internally located mutation at position 153 (C6-2) and used to transform Rat 2 cells. Whereas T antigen from C6-2-transformed cells lacked any specific affinity for these sequences. Therefore, the single mutation at amino acid position 153 (Asn leads to Thr) is sufficient to abolish the origin-binding property of T antigen. A T antigen-specific monoclonal antibody, PAb 100, which had been previously shown to immunoprecipitate an immunologically distinct origin-binding subclass of T antigen, recognized wild-type or C6-1 antigens, but failed to react with C6 or C6-2 T antigens. These results indicate that viral replication function comprises properties of T antigen that exist in addition to its ability to bind specifically to the SV40 regulatory sequences. Furthermore, it is concluded from these data that specific viral origin binding is not a necessary feature of the transforming function of T antigen.

Simian virus 40 large T-antigen point mutants that are defective in viral DNA replication but competent in oncogenic transformation

1984 ◽  
Vol 4 (6) ◽  
pp. 1125-1133
Author(s):  
M M Manos ◽  
Y Gluzman
Keyword(s):  
Amino Acid ◽  
Dna Replication ◽  
Atpase Activity ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Large T Antigen ◽  
Oncogenic Transformation ◽  
Viral Dna ◽  
Viral Dna Replication

The large T antigen of simian virus 40 (SV40) is a multifunctional protein that is essential in both the virus lytic cycle and the oncogenic transformation of cells by SV40. To investigate the role of the numerous biochemical and physiological activities of T antigen in the lytic and transformation processes, we have studied DNA replication-deficient, transformation-competent large T-antigen mutants. Here we describe the genetic and biochemical analyses of two such mutants, C2/SV40 and C11/SV40. The mutants were isolated by rescuing the integrated SV40 DNA from C2 and C11 cells (CV-1 cell lines transformed with UV-irradiated SV40). The mutant viral early regions were cloned into the plasmid vector pK1 to generate pC2 and pC11. The mutations that are responsible for the deficiency in viral DNA replication were localized by marker rescue. Subsequent DNA sequencing revealed point mutations that predict amino acid substitutions in the carboxyl third of the protein in both mutants. The pC2 mutation predicts the change of Lys----Arg at amino acid 516. pC11 has two mutations, one predicting a change of Pro----Ser at residue 522, and another predicting a Pro----Arg change at amino acid 549. The two C11 mutations were separated from each other to form two distinct viral genomes in pC11A and pC11B. pC2, pC11, pC11A, and pC11B are able to transform both primary and established rodent cell cultures. The C11 and C11A T antigens are defective in ATPase activity, suggesting that wild-type levels of ATPase activity are not necessary for the oncogenic transformation of cells by T antigen.

scholarly journals Simian virus 40 large T-antigen point mutants that are defective in viral DNA replication but competent in oncogenic transformation.

1984 ◽  
Vol 4 (6) ◽  
pp. 1125-1133 ◽  
Author(s):  
M M Manos ◽  
Y Gluzman
Keyword(s):  
Amino Acid ◽  
Dna Replication ◽  
Atpase Activity ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Large T Antigen ◽  
Oncogenic Transformation ◽  
Viral Dna ◽  
Viral Dna Replication

The large T antigen of simian virus 40 (SV40) is a multifunctional protein that is essential in both the virus lytic cycle and the oncogenic transformation of cells by SV40. To investigate the role of the numerous biochemical and physiological activities of T antigen in the lytic and transformation processes, we have studied DNA replication-deficient, transformation-competent large T-antigen mutants. Here we describe the genetic and biochemical analyses of two such mutants, C2/SV40 and C11/SV40. The mutants were isolated by rescuing the integrated SV40 DNA from C2 and C11 cells (CV-1 cell lines transformed with UV-irradiated SV40). The mutant viral early regions were cloned into the plasmid vector pK1 to generate pC2 and pC11. The mutations that are responsible for the deficiency in viral DNA replication were localized by marker rescue. Subsequent DNA sequencing revealed point mutations that predict amino acid substitutions in the carboxyl third of the protein in both mutants. The pC2 mutation predicts the change of Lys----Arg at amino acid 516. pC11 has two mutations, one predicting a change of Pro----Ser at residue 522, and another predicting a Pro----Arg change at amino acid 549. The two C11 mutations were separated from each other to form two distinct viral genomes in pC11A and pC11B. pC2, pC11, pC11A, and pC11B are able to transform both primary and established rodent cell cultures. The C11 and C11A T antigens are defective in ATPase activity, suggesting that wild-type levels of ATPase activity are not necessary for the oncogenic transformation of cells by T antigen.

scholarly journals Association of simian virus 40 T antigen with the nuclear matrix of infected and transformed monkey cells.

1984 ◽  
Vol 4 (7) ◽  
pp. 1384-1392 ◽  
Author(s):  
L Covey ◽  
Y Choi ◽  
C Prives
Keyword(s):  
Amino Acid ◽  
Dna Replication ◽  
Viral Replication ◽  
Nuclear Matrix ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Binding Property ◽  
Viral Dna ◽  
Cos Cells

The subnuclear distribution of simian virus 40 large T antigen within nuclei of transformed Cos and C6 monkey cells was examined. Cos cells express wild-type T antigen but lack viral sequences required for DNA replication, whereas C6 cells contain a functional viral origin but express a replication-defective mutant T antigen which is unable to bind specifically to viral DNA. Discrete subpopulations of T antigen were isolated from the soluble nucleoplasm, chromatin, and nuclear matrix of both cell lines. Although only a small quantity (2 to 12%) of the total nuclear T antigen from Cos cells was associated with the nuclear matrix, a high proportion (25 to 50%) of C6 T antigen was bound to this structure. Results obtained from lytically infected monkey cells showed that early in infection, before viral replication was initiated, a higher proportion (22%) of T antigen was found associated with the nuclear matrix compared with amounts found associated with this structure later in infection (5 to 8%). These results suggest that an increased association of T antigen with this structure is not correlated with viral replication. T antigen isolated from the C6 nuclear matrix was more highly phosphorylated than was soluble C6 T antigen and was capable of binding to the host p53 protein. C6 DNA contains three mutations: two corresponding to N-terminal changes at amino acid positions 30 and 51 and a third located internally at amino acid position 153. By analysis of the subnuclear distribution of T antigen from rat cells transformed by C6 submutant T antigens, it was determined that one or both of the mutations at the NH2 terminus are responsible for the increased quantity of C6 T antigen associated with the nuclear matrix. These results suggest that neither a functional viral DNA replication origin nor the origin binding property of T antigen is required for association of this protein with the nuclear matrix.

A second domain of simian virus 40 T antigen in which mutations can alter the cellular localization of the antigen

1986 ◽  
Vol 6 (6) ◽  
pp. 2207-2212
Author(s):  
J D Welsh ◽  
C Swimmer ◽  
T Cocke ◽  
T Shenk
Keyword(s):  
Amino Acid ◽  
Dna Replication ◽  
Cellular Localization ◽  
Tumor Antigens ◽  
Simian Virus 40 ◽  
Amino Acid Position ◽  
Simian Virus ◽  
T Antigen ◽  
Nuclear Antigen ◽  
Origin Of Dna Replication

Previous studies have demonstrated that mutations at amino acid position 128 of the simian virus 40 large T antigen can alter the subcellular localization of the antigen. A second domain in which mutations can alter localization of the nuclear antigen has been identified by mutations at amino acid positions 185, 186, and 199. Mutations in this region cause the polypeptide to accumulate in both the nucleus and cytoplasm of monkey cells. These T-antigen variants accumulate to near normal levels, but they don't bind to the simian virus 40 origin of DNA replication and are unable to mediate DNA replication. Furthermore, the altered tumor antigens can no longer transform secondary rat cells at normal efficiency, but they retain the ability to transform established mouse and rat cell lines.

Association of simian virus 40 T antigen with the nuclear matrix of infected and transformed monkey cells

1984 ◽  
Vol 4 (7) ◽  
pp. 1384-1392
Author(s):  
L Covey ◽  
Y Choi ◽  
C Prives
Keyword(s):  
Amino Acid ◽  
Dna Replication ◽  
Viral Replication ◽  
Nuclear Matrix ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Binding Property ◽  
Viral Dna ◽  
Cos Cells

The subnuclear distribution of simian virus 40 large T antigen within nuclei of transformed Cos and C6 monkey cells was examined. Cos cells express wild-type T antigen but lack viral sequences required for DNA replication, whereas C6 cells contain a functional viral origin but express a replication-defective mutant T antigen which is unable to bind specifically to viral DNA. Discrete subpopulations of T antigen were isolated from the soluble nucleoplasm, chromatin, and nuclear matrix of both cell lines. Although only a small quantity (2 to 12%) of the total nuclear T antigen from Cos cells was associated with the nuclear matrix, a high proportion (25 to 50%) of C6 T antigen was bound to this structure. Results obtained from lytically infected monkey cells showed that early in infection, before viral replication was initiated, a higher proportion (22%) of T antigen was found associated with the nuclear matrix compared with amounts found associated with this structure later in infection (5 to 8%). These results suggest that an increased association of T antigen with this structure is not correlated with viral replication. T antigen isolated from the C6 nuclear matrix was more highly phosphorylated than was soluble C6 T antigen and was capable of binding to the host p53 protein. C6 DNA contains three mutations: two corresponding to N-terminal changes at amino acid positions 30 and 51 and a third located internally at amino acid position 153. By analysis of the subnuclear distribution of T antigen from rat cells transformed by C6 submutant T antigens, it was determined that one or both of the mutations at the NH2 terminus are responsible for the increased quantity of C6 T antigen associated with the nuclear matrix. These results suggest that neither a functional viral DNA replication origin nor the origin binding property of T antigen is required for association of this protein with the nuclear matrix.

scholarly journals A second domain of simian virus 40 T antigen in which mutations can alter the cellular localization of the antigen.

1986 ◽  
Vol 6 (6) ◽  
pp. 2207-2212 ◽  
Author(s):  
J D Welsh ◽  
C Swimmer ◽  
T Cocke ◽  
T Shenk
Keyword(s):  
Amino Acid ◽  
Dna Replication ◽  
Cellular Localization ◽  
Tumor Antigens ◽  
Simian Virus 40 ◽  
Amino Acid Position ◽  
Simian Virus ◽  
T Antigen ◽  
Nuclear Antigen ◽  
Origin Of Dna Replication

Previous studies have demonstrated that mutations at amino acid position 128 of the simian virus 40 large T antigen can alter the subcellular localization of the antigen. A second domain in which mutations can alter localization of the nuclear antigen has been identified by mutations at amino acid positions 185, 186, and 199. Mutations in this region cause the polypeptide to accumulate in both the nucleus and cytoplasm of monkey cells. These T-antigen variants accumulate to near normal levels, but they don't bind to the simian virus 40 origin of DNA replication and are unable to mediate DNA replication. Furthermore, the altered tumor antigens can no longer transform secondary rat cells at normal efficiency, but they retain the ability to transform established mouse and rat cell lines.

Carcinogen-induced DNA amplification in vitro: overreplication of the simian virus 40 origin region in extracts from carcinogen-treated CO60 cells

1990 ◽  
Vol 10 (1) ◽  
pp. 75-83
Author(s):  
Y Berko-Flint ◽  
S Karby ◽  
D Hassin ◽  
S Lavi
Keyword(s):  
De Novo ◽  
Chinese Hamster ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Dna Molecules ◽  
Viral Origin ◽  
Cell Extracts ◽  
Origin Region

An in vitro system to study carcinogen-induced amplification in simian virus 40 (SV40)-transformed Chinese hamster (CO60) cells is described. SV40 amplification in this system resembled in many aspects the viral overreplication observed in drug-treated CO60 cells. Cytosolic extracts from N-methyl-N'-nitro-N-nitrosoguanidine-treated cells supported de novo DNA synthesis in the presence of excess exogenous T antigen and the SV40-containing plasmid pSVK1. The pattern of viral replication in these extracts was unique, since only the 2.4-kilobase-pair region spanning the origin was overreplicated, whereas distal sequences were not replicated significantly. Extracts from control cells supported only marginal levels of replication. In HeLa extracts, complete SV40 DNA molecules were replicated efficiently. The overreplication of the origin region in CO60 cell extracts was bidirectional and symmetrical. A fraction of the newly synthesized DNA molecules underwent a second round of replication, yielding MboI-sensitive fragments representing the 2.4-kilobase-pair region around the origin. The mechanisms controlling the amplification of the viral origin region, the nature of the cellular factors induced in the carcinogen-treated cells, and their putative association with general drug-induced SOS-like responses are discussed.

scholarly journals Regulation of simian virus 40 gene expression in Xenopus laevis oocytes.

1985 ◽  
Vol 5 (8) ◽  
pp. 2019-2028 ◽  
Author(s):  
T Michaeli ◽  
C Prives
Keyword(s):  
Xenopus Laevis ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Oocyte Nucleus ◽  
Xenopus Laevis Oocytes ◽  
Large T Antigen ◽  
Viral Dna ◽  
Infected Monkey ◽  
Sv40 Dna

Expression of the simian virus 40 (SV40) early and late regions was examined in Xenopus laevis oocytes microinjected with viral DNA. In contrast to the situation in monkey cells, both late-strand-specific (L-strand) RNA and early-strand-specific (E-strand) RNA could be detected as early as 2 h after injection. At all time points tested thereafter, L-strand RNA was synthesized in excess over E-strand RNA. Significantly greater quantities of L-strand, relative to E-strand, RNA were detected over a 100-fold range of DNA concentrations injected. Analysis of the subcellular distribution of [35S]methionine-labeled viral proteins revealed that while the majority of the VP-1 and all detectable small t antigen were found in the oocyte cytoplasm, most of the large T antigen was located in the oocyte nucleus. The presence of the large T antigen in the nucleus led us to investigate whether this viral product influences the relative synthesis of late or early RNA in the oocyte as it does in infected monkey cells. Microinjection of either mutant C6 SV40 DNA, which encodes a large T antigen unable to bind specifically to viral regulatory sequences, or deleted viral DNA lacking part of the large T antigen coding sequences yielded ratios of L-strand to E-strand RNA that were similar to those observed with wild-type SV40 DNA. Taken together, these observations suggest that the regulation of SV40 RNA synthesis in X. laevis oocytes occurs by a fundamentally different mechanism than that observed in infected monkey cells. This notion was further supported by the observation that the major 5' ends of L-strand RNA synthesized in oocytes were different from those detected in infected cells. Furthermore, only a subset of those L-strand RNAs were polyadenylated.

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