Acquisition of enzyme function by mouse kidney cells abortively infected with papovavirus SV40

Initiation of DNA synthesis and uptake of T antigen by chick erythrocyte nuclei in hterokaryons with SV40-transformed human cells

Nonsynchronized and hydroxyurea (HU)-synchronized SV40-transformed human cells (W98VaD) were fused with chick embryo erythrocytes (CE). The uptake of T antigen by CE nuclei was compared with initiation of chick nuclear DNA synthesis. Uptake of T antigen by CE nuclei occurred at about the same time after fusion with asynchronous as with HU-synchronized cells. CE nuclei rapidly became T antigen-positive between 16 h and 28 h after fusion and usually almost all CE nuclei were T antigen-positive by 48 h after fusion. In contrast, initiation of chick nuclear DNA synthesis occurred as a function of time after reversal of the HU block, when the host cell nuclei were also synthesizing DNA. Chick nuclear DNA synthesis occurred in many heterokaryons before the CE nuclei became T antigen-positive by immunofluorescence.

"Early" simian-virus-40-specific RNA contains information for tumor antigen formation and chromatin replication

Simian virus 40 (SV40) induces tumor (T)-antigen formation, chromatin replication, and mitosis in primary mouse kidney cells arrested in G0 phase of the mitotic cycle. The temporal and quantitative relation between these early virus-specific reactions led to the hypothesis that the early SV40 mRNA contains information necessary for T-antigen formation and induction of cellular DNA synthesis. To get direct experimental evidence for this hypothesis, the early strand of SV40 DNA was transcribed in vitro by Escherichia coli DNA-dependent RNA polymerase and the SV40-specific cRNA was transferred by microinjection into epitheloid cells of confluent primary mouse kidney cultures. T-antigen formation and stimulation of DNA synthesis were investigated in the recipient cells. The experimental results obtained agree with the hypothesis that T-antigen is a virus-coded protein and that the early virus-specific mRNA contains information necessary for stimulation of cellular DNA replication in the arrested cells.

Nonproductive infection and induction of cellular deoxyribonucleic acid synthesis by bovine adenovirus type 3 in a contact-inhibited mouse cell line

Bovine adenovirus type 3 (BAV-3), which has been reported to produce tumors in newborn hamsters, induced cellular deoxyribonucleic acid (DNA) synthesis in a contact-inhibited mouse kidney cell line (C3H2K). In this system, the virus did not multiply, whereas virus-specific tumor antigen (T antigen) was detected in nearly all cells. Replication of viral DNA could not be detected by DNA-DNA hybridization on membrane filters. The cellular DNA synthesis induced by BAV-3 did occur in the absence of added serum. Extent of induction of cellular DNA synthesis was closely correlated with the multiplicity of infection. Cells activated to synthesize DNA in the serum-free medium by the virus infection progressed to cell division without noticeable cell killing.

Analysis of the events leading to SV40-induced chromosome replication and mitosis in primary mouse kidney cell cultures

Abortive infection with simian virus 40 in confluent, "contact-inhibited", mouse kidney cell cultures was studied. The sequential events, in individual cells, are tentatively represented by the simplified scheme: (a) transcription of early virus-specific (messenger) RNA; (b) appearance of T-antigen; (c) [psychrosensitive event(s)]; (d) chromosome replication; (e) normal or abnormal mitosis. No evidence for the replication of viral progeny DNA was obtained. The sequence of the events (a)-(d) is analogous to that observed in contact-inhibited mouse kidney tissue culture cells during lytic infection with polyoma virus.

Rescue of Simian Virus 40 from Cell Lines Transformed at High and at Low Input Multiplicities by Unirradiated or Ultraviolet-irradiated Virus

The relation between simian virus 40 (SV40) input multiplicity during transformation of primary mouse kidney cultures and the subsequent rescue of SV40 from clonal lines of transformed cells has been studied. Primary mouse kidney cultures were transformed with unirradiated SV40 at input multiplicities varying from 0.06 to 200 plaque-forming units (PFU) /cell or with SV40 irradiated with ultraviolet (UV) light to a survival of 0.04 to 0.01. All of the transformed lines contained the intranuclear SV40 T antigen, but cell-free extracts prepared from the transformed cell lines failed to yield infectious virus when assayed on monkey kidney cell (CV-1) monolayers. After fusion with susceptible CV-1 cells induced by UV-inactivated Sendai, all of the lines transformed by unirradiated virus yielded infectious SV40. The frequency of induction and the incidence of successful trials did not depend on the multiplicity of infection. “Good” yielders were obtained from mouse kidney cells transformed at the low input multiplicity of 0.06 PFU /cell. In contrast, only 4 of 12 clonal lines transformed at moderately low input multiplicity, and none of the lines transformed at very low input multiplicity with UV-irradiated virus yielded infectious SV40. The four positive lines have been classified as “poor” or “rare” yielders.

Propagation or elimination of viral infection in carrier cells

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Thymidine kinase from normal, simian virus 40-transformed and simian virus 40-lytically infected cells

Simian virus 40 (SV40) infection of human diploid cells failed to cause an enhanced production of thymidine kinase during the first 10 days after infection. Thymidine kinase activities from extracts of SV40-transformed cultures (human or simian) were considerably higher than the activity levels in extracts from the normal cells of origin. In addition, whereas the kinase activities obtained for human diploid cultures decreased as the cell sheet became confluent, the kinase activities for SV40-transformed human cells remained high after confluence was reached. Antisera obtained from hamsters bearing SV40 or adeno-7-SV40 hybrid virus tumors selectively inhibited enzyme from transformed sources (human or simian). Also, the antisera selectively inhibited enzyme extracted from SV40-lytically infected monkey cells. Sera from normal animals or from hamsters bearing polyoma tumors failed to inhibit enzymes from normal, SV40-transformed, or SV40-lytically infected cells. The Michaelis constant of partially purified enzyme from SV40-transformed cells was two to five times as high as that obtained for partially purified enzyme from human diploid cell cultures.

Virogenic properties of bromodeoxyuridine-sensitive and bromodeoxyuridine-resistant simian virus 40-transformed mouse kidney cells

When simian virus 40 (SV40)-transformed mouse kidney cells (mKS) were grown in the presence of susceptible indicator cells, SV40 was readily recovered from: (i) 15 transformed cell lines, (ii) transformed cells subcultured 45 times over a 7-month period in medium containing antiviral serum and bromodeoxyuridine (dBU), (iii) 45 of 46 clonal lines isolated in the presence of antiviral serum, (iv) 19 of 19 secondary clones isolated from two clonal lines, and (v) dBU-resistant transformed cell lines. dBU-resistant SV40-transformed mouse kidney cell lines were selected and shown to contain the T antigen and to have normal levels of thymidylate kinase and deoxyribonucleic acid (DNA) polymerase, but to be deficient in thymidine (dT) kinase. Radioautographic and biochemical experiments demonstrated that very little (3)H-dT was incorporated into DNA of dBU-resistant cells during a 6-hr labeling period. After infection of dT kinase-deficient mKS cells with vaccinia virus, high levels of dT kinase were induced. The properties of SV40 recovered from dBU-sensitive and dBU-resistant cells were studied. SV40 recovered from transformed cells was shown to express in CV-1 cells at least six functions characteristic of parental virus: synthesis of capsid antigen, synthesis of T antigen, synthesis of viral DNA, induction of dT kinase, induction of DNA polymerase, and induction of host cell DNA synthesis. In addition, SV40 recovered from the transformed cells induced T antigen, dT kinase, deoxycytidylate deaminase, thymidylate kinase, and DNA polymerase in abortively infected mouse kidney cultures, and the virus was also capable of transforming primary cultures of mouse kidney cells.

Induction of cellular deoxyribonuleic acid synthesis by simian virus 40

The incorporation of (3)H-thymidine ((3)H-dT) into deoxyribonucleic acid (DNA) has been studied in uninfected confluent monolayer cultures of monkey kidney and mouse kidney cells, simian virus 40 (SV40)-infected cells, and in SV40-transformed mouse kidney cells. Radioautographic measurements revealed that during the period from 28 to 51 hr after productive SV40 infection of monkey kidney cultures about 80% of the cells synthesized DNA, compared to about 16% in uninfected cultures. At 28 to 43 hr after abortive SV40 infection of mouse kidney cultures, 24 to 37% of the cells synthesized DNA, compared to about 6 to 8% in uninfected cultures. The infected monkey kidney and mouse kidney cultures, respectively, incorporated about 5 to 10 times and 3 to 5 times as much (3)H-dT into DNA as did uninfected cultures. Moreover, the net DNA synthesized by SV40-infected monkey kidney cultures, estimated by colorimetric methods, substantially exceeded that of uninfected cultures. Nitrocellulose chromatography and band centrifugation experiments were performed to elucidate the kinds of DNA synthesized in the cultures. In uninfected monkey kidney cultures and at 2 to 12 hr after SV40 infection, almost all of the (3)H-dT labeled DNA sedimented more rapidly than SV40 DNA, and the radioactive DNA was denatured by heating for 12 min at 100 C (cellular DNA). Almost all of the labeled DNA obtained from abortively infected mouse kidney cultures and from SV40-transformed cells also had the properties of cellular DNA. However, approximately one-third to one-half of the labeled DNA obtained from monkey kidney cultures 28 to 51 hr after infection sedimented more slowly than cellular DNA and was not denatured by the heating (SV40 DNA). It is concluded that cellular DNA synthesis was induced during either the productive or abortive SV40 infections.

Nonidentiy of some simian virus 40-induced enzymes with tumor antigen

The complement-fixing tumor (T) antigen induced by simian virus 40 (SV40) has been prepared from SV40-infected cell cultures, from infected cell cultures treated at the time of infection with 1-beta-d-arabinofuranosylcytosine (ara-C), and from SV40-transformed cells. Upon partial purification, the T antigen exhibited the following properties: it was tightly adsorbed by calcium phosphate gel, it was precipitated by acetic acid at pH 5 or by ammonium sulfate at about 20 to 32% saturation, and it had a molecular weight greater than 250,000, as estimated by Sephadex G-200 gel chromatography. In contrast, deoxycytidylate (dCMP) deaminase, thymidylate (dTMP) kinase, and thymidine (dT) kinase were less strongly bound to calcium phosphate and were not precipitated at pH 5; these enzymes also had much lower molecular weights than the T antigen, as did dihydrofolic (FH(2)) reductase. Furthermore, higher ammonium sulfate concentrations were required to precipitate dCMP deaminase, dTMP kinase, and FH(2) reductase activities than to precipitate the T antigen. Another difference was that the T antigen was not stabilized, but dCMP deaminase, dTMP kinase, and dT kinase, were stabilized, respectively, by dCTP, dTMP, and dT or dTTP. Deoxyribonucleic acid (DNA) polymerase activity resembled the T antigen in adsorption to calcium phosphate, in precipitation by ammonium sulfate or at pH 5, and in the rate of inactivation when incubated at 38 C. However, the polymerase activity could be partly separated from the T antigen by Sephadex G-200 gel chromatography. The cell fraction containing partially purified T antigen also contained a soluble complement-fixing antigen (presumably a subunit of the viral capsid) which reacted with hyperimmune monkey sera. The latter antigen was present in very low titers or absent from cell extracts prepared from SV40-infected monkey kidney cell cultures which had been treated with ara-C at the time of infection, or from SV40-transformed mouse kidney (mKS) or hamster tumor (H-50) cells. The T antigen, however, was present in usual amounts in SV40-transformed cells or ara-C treated, infected cells.

Enzyme induction in green monkey kidney cultures infected with simian adenovirus

Thymidine kinase was induced after infection of an established strain of green monkey kidney cells (CV-1) with simian adenovirus SV15. Increased levels of thymidine kinase were first observed 8 to 10 hr postinoculation (PI), and the levels increased four- to eightfold by 16 to 24 hr PI. A transient increase (1.5- to 3-fold) of deoxyribonucleic acid (DNA) polymerase activity was also observed about 18 hr PI, but the level of deoxycytidylic deaminase was not enhanced. The inductions of thymidine kinase and DNA polymerase were not obtained when protein synthesis was inhibited with 10(-5) M cycloheximide. However, the enzyme increases did take place when infected cultures were treated with 1-beta-D-arabinofuranosylcytosine (ara-C), an inhibitor of DNA synthesis and SV15 replication. The incorporation of tritium-labeled thymidine (H(3)-dT) into DNA was also stimulated 8 to 24 hr after infection with SV15.