Virus-specific nucleic acids in SV40-exposed hamster embryo cell lines: correlation with S and T antigens

Surface antigens on HeLa cells persistently infected with HVJ (Sendai virus)

Surface antigens of HeLaHVJ cells, a cell line persistently infected with HVJ, were studied by fluorescent antibody staining. After absorption with concentrated HVJ virions and HeLa cells, anti-HeLaHVJ antiserum was able to demonstrate specific surface fluorescence on HeLaHVJ cells, while this serum no longer reacted with original HeLa cells nor with HVJ virions. During cytolytic infection of HeLa cells with HVJ, this specific surface antigen appeared at an early stage of infection prior to the appearance of newly synthesized HVJ viral antigens and moreover appeared in spite of the inhibition of viral protein synthesis. This antigen was detected neither on HeLa cells infected with other myxoviruses except HVJ nor on various other kinds of cells infected with HVJ. The specific surface antigen was still found on the HeLaHVJ cell surface after incubation at 38 degrees C for two days, while HVJ structural antigens on the cell surface no longer could be detected. Mild short-term treatment of HeLa cells with trypsin, neuraminidase from vibrio cholerae, phospholipase-C and hyaluronidase failed to expose specific antigen. The antigen was distinguishable from the Forssman and human blood type antigens. The mechanism of appearance of a new antigen on the surface of HeLaHVJ cells remains unclear.

Simian virus 40 DNA replication, transcription, and antigen induction during infection with two adenovirus 2-SV40 hybrids that contain the entire SV40 genome

The Ad2++hey hybrid virus population produces simian virus 40 (SV40) efficiently during lytic infection, whereas Ad2++ley does not, although both hybrids contain a complete SV40 genome. In this report, we demonstrate the synthesis of nonhydrid SV40 DNA in Ad2++HEY-infected Vero cells, but only early SV40 RNA is transcribed efficiently in Ad2++LEY-infected cells. Ad2++HEY induces SV40 U, T, and V antigens during lytic infection of African green monkey kidney cells, whereas Ad2++LEY induces only SV40 U and T antigens. These variations in the behavior of Ad2++HEY and Ad2++LEY regarding expression of SV40 functions probably reflect differences in the rate of SV40 excision from the hybrid genomes.

Studies of nondefective adenovirus 2-simian virus 40 hybrid viruses. Transformation of hamster kidney cells by adenovirus 2 and the nondefective hybrid viruses

Nonhybrid adenovirus 2 (Ad2) and five nondefective Ad2-simian virus 40 (SV40) hybrids (Ad2(+)ND(1)-Ad2(+)ND(5)) failed to produce tumors when injected into newborn hamsters. However, each of these agents transformed hamster kidney cells in vitro, and the transformed cell lines produced tumors when injected into suckling hamsters. Foci of cells transformed by the hybrids could not be distinguished from foci of cells transformed by nonhybrid Ad2. Histopathologically, tumors induced by the nondefective hybrid-transformed lines were of the adenovirus type with no areas of SV40-type fibrosarcoma. All of the cell lines studied contained Ad2 T antigen and Ad2 RNA. Only the B55HK(1) line contained the three early SV40 antigens, U, TSTA, and T. The ND(4)HK(1) line contained SV40 T and TSTA antigens (the latter antigen being detected only after 48 to 49 tissue culture passages) and SV40 RNA. The ND(2)HK(2) line contained SV40 RNA but no detectable SV40 antigens; the other hybrid-transformed lines contained no SV40 RNA. The transformation of hamster cells by the nondefective Ad2-SV40 hybrids seemed to be caused by the Ad2 genome and could not be attributed to the regions of the SV40 genome contained within the hybrids. Additionally, these results indicate that interactions between the genomes of the nondefective hybrid viruses and the hamster cells they transform are complex and could involve the site of integration, the size of the incorporated viral genome, the transcription or translation of the viral genome, or various combinations of these processes.

Control of simian virus 40 gene expression in adenovirus-simian virus 40 hybrid viruses. Synthesis of hybrid adenovirus 2-simian virus 40 RNA molecules in cells infected with a nondefective adenovirus 2-simian virus 40 hybrid virus

The effect of interferon on simian virus 40 (SV40) and adenovirus 2 (Ad2) T antigen synthesis has been examined in cells infected with SV40, with Ad2, and with a nondefective Ad2-SV40 hybrid virus, Ad2(+)ND(4). The induction of SV40 T antigen by SV40 was highly sensitive to interferon, whereas the induction of Ad2 T-antigen by Ad2 was resistant. This difference in interferon sensitivity was also noted in cells simultaneously infected with both viruses. However, the induction of SV40 T antigen by Ad2(+)ND(4), which contains covalently linked SV40 and Ad2 DNAs, was as resistant to interferon as the induction of Ad2 T antigen. This change in the interferon sensitivity of SV40 T antigen synthesis suggests that the expression of at least this portion of the SV40 genetic information in Ad2(+)ND(4) is under Ad2 genetic control. When RNA extracted from Ad2(+)ND(4)-infected cells was examined by means of sequential hybridization with Ad2 DNA, elution, and rehybridization with SV40 DNA, 27% of the SV40-specific RNA was found to be linked to Ad2 RNA. No such linkage was detected in control mixtures of Ad2 and SV40 RNAs. The presence of Ad2 and SV40 nucleotide sequences in the same RNA molecule implies that, in Ad2(+)ND(4) infection, transcription is initiated in the DNA of one virus (Ad2 or SV40) and continues without interruption across the point of junction into the DNA of the other virus. Furthermore, the interferon resistance of Ad2(+)ND(4)-induced SV40 T antigen synthesis suggests that transcription of the genetic information for SV40 T antigen is initiated in a region of Ad2 DNA.

Evidence that the AKR murine-leukemia-virus genome is complete in DNA of the high-virus AKR mouse and incomplete in the DNA of the "virus-negative" NIH mouse

The AKR mouse has a high titer of murine leukemia virus early in life, and virus-negative cells derived from embryos of this mouse strain can be activated to yield murine leukemia virus by treatment with 5-iododeoxyuridine. In contrast to this high-virus strain, the NIH Swiss mouse has a low incidence of leukemia and no murine leukemia virus has been isolated from it (virus-negative). We have investigated this difference between AKR and NIH mice by examining the sequences specific for murine leukemia virus in nucleic acids of these mice. A single-stranded viral-DNA probe synthesized in vitro using murine-leukemia-virus from the AKR mouse contains at least 87% of the sequences present in the 70S viral RNA; most of these sequences are in proportions similar to their content in the 70S RNA. Using this probe in nucleic acid hybridization experiments, we have shown that NIH-mouse-cell DNA and AKR-mouse-cell DNA differ with respect to sequences specific for AKR murine-leukemia-virus: NIH-mouse-cell DNA lacks some of the virus-specific sequences present in AKR-mouse-cell DNA, and there are two distinct sets of virus-specific sequences in AKR-mouse-cell DNA, whereas there is only one set in NIH-mouse-cell DNA.RNA from virus-negative AKR-mouse cells grown in tissue culture contains some, but not all, virus-specific RNA sequences; however, within 48 hr after initiating treatment of these cells with 5-iododeoxyuridine, the complete viral genome is represented in cellular RNA.

Variants of simian virus 40-transformed 3T3 cells that are resistant to concanavalin A

By treating populations of simian virus 40 (SV40)-transformed 3T3 cells with concanavalin A, variants have been isolated which are resistant to the killing action of the lectin. The variants (i) resemble 3T3 cells morphologically and in some of their growth characteristics; (ii) are not agglutinated by high concentrations of concanavalin A or wheat germ agglutinin, but can be rendered agglutinable by treatment with low concentrations of trypsin; (iii) bind the same number of concanavalin A molecules as 3T3 or SV3T3 cells; (iv) cannot be transformed by SV40 and are resistant to focus formation after infection with murine sarcoma virus; (v) contain SV40-specific T antigen and RNA and; (vi) yield wild-type SV40 virus after heterokaryon formation with BS-C-1 cells.

Studies of nondefective adenovirus 2-simian virus 40 hybrid viruses. VI. Characterization of the DNA from five nondefective hybrid viruses

Certain biophysical characteristics of the DNA from each of the five nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid viruses (Ad2(+)ND(1), Ad2(+)ND(2), Ad2(+)ND(3), Ad2(+)ND(4), Ad2(+)ND(5)) have been determined. The guanine plus cytosine content varied from 55 to 57% and was not significantly different from that of nonhybrid Ad2 (56%), and the hybrid DNA molecules had mean molecular lengths which were similar to that of the standard, Ad2. The Ad2 and SV40 components of each hybrid were linked by alkali-resistant, presumably covalent bonds. The percentage of SV40 DNA in each hybrid virus was determined by hybridization with SV40 complementary RNA in a calibrated system. The results indicate that each hybrid virus DNA contains a different percentage of SV40 nucleotide sequences. The estimated size of the SV40 DNA component varies from 48,000 daltons for Ad2(+)ND(3) to 840,000 daltons for Ad2(+)ND(4), the latter being equivalent to between one-fourth and one-third of the SV40 genome.

Studies of nondefective adenovirus 2-simian virus 40 hybrid viruses. V. Isolation of additional hybrids which differ in their simian virus 40-specific biological properties

Four new nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid viruses have been isolated. Although these viruses (designated Ad2(+)ND(2), Ad2(+)ND(3), Ad2(+)ND(4), and Ad2(+)ND(5)) were clonal derivatives of the same Ad2-SV40 hybrid population, they differ significantly from each other and from the previously isolated nondefective hybrid, Ad2(+)ND(1), in their biological properties or in the amount of SV40-specific RNA induced during lytic infection.Like Ad2(+)ND(1), Ad2(+)ND(2), and Ad2(+)ND(4) pass serially in both human embryonic kidney (HEK) and primary African green monkey kidney cells. In contrast, Ad2(+)ND(3) and Ad2(+)ND(5) pass serially only in HEK cells. Ad2(+)ND(2) is like Ad2(+)ND(1) in that it induces the SV40 U antigen, but not SV40 T antigen; however, in contrast to the perinuclear SV40 antigen induced by Ad2(+)ND(1), the SV40 antigen induced by Ad2(+)ND(2) is located peripherally in the cytoplasm as well as in the perinuclear region of infected cells. Ad2(+)ND(4) induces both the SV40 T and U antigens. Ad2(+)ND(3) and Ad2(+)ND(5) do not induce serologically detectable SV40 antigens and are distinguished from each other on the basis of the relative quantities of SV40-specific RNA which they induce. The induction of different SV40-specific functions suggests the incorporation of different segments of SV40 DNA within the genomes of the respective hybrid viruses.

Studies of nondefective adenovirus 2-simian virus 40 hybrid viruses. VII. Characterization of the simian virus 40 RNA species induced by five nondefective hybrid viruses

Five nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid viruses have been isolated and found to contain segments of SV40 DNA covalently linked to Ad2 DNA. The quantity of SV40 DNA present is a stable characteristic of each hybrid virus, and varies from less than 5% (in Ad2(+)ND(3)) to more than 30% (in Ad2(+)ND(4)) of the SV40 genome. We have characterized the SV40 portions of these hybrids by relating the SV40-specific RNA sequences transcribed in cells infected with each hybrid virus to those transcribed in cells infected with each of the other hybrid viruses and with SV40 itself. RNA-DNA hybridization-competition experiments indicate that the number of unique SV40 RNA sequences transcribed in infected cells is proportional to the size of the SV40 DNA segment contained within each hybrid and, in the case of the three hybrids which induce detectable SV40-specific antigens, to the number of SV40 antigens induced. Furthermore, the SV40-specific RNA sequences transcribed from any one of the hybrids are completely represented in the RNA transcribed from all other hybrids with longer SV40 segments. Thus, the SV40 DNA regions in the five hybrid viruses appear to contain some nucleotide sequences in common. The SV40-specific RNA transcribed from Ad2(+)ND(4), the hybrid containing the largest SV40 segment, is qualitatively similar to the SV40-specific RNA transcribed early (i.e., prior to viral DNA replication) in SV40 lytic infection. Thus, it appears that no significant amount of late SV40 DNA is transcribed during infection by any of the five nondefective Ad2-SV40 hybrid viruses.

Evidence for a transcription-control region of Simian virus 40 in the adenovirus 2--Simian virus 40 hybrid, Ad2+ND 1

The complementary DNA strands of the nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid virus, Ad2(+)ND(1), were separated by isopycnic banding in a CsCl density gradient in the presence of synthetic polyribonucleotides. Separated strands were used in DNA-RNA hybridization reactions with RNA from cells productively infected by Ad2 or SV40, and with complementary SV40 RNA transcribed asymmetrically in vitro. About five times as much Ad2 RNA hybridized to the light stand of Ad2(+)ND(1) as to the heavy strand. Complementary RNA and early SV40 RNA (RNA synthesized before viral DNA replication) had significant homology only with the light strand. Only half as much of a preparation of RNA synthesized before and after viral DNA replication (early-plus-late SV40 RNA) hybridized to the light strand as to the heavy strand. These results indicate that templates for both late and early SV40 RNA are present in Ad2(+)ND(1). Therefore, the small SV40 segment within this virus (10-18% of the SV40 genome) must contain a transcription-control region. Ad2(+)ND(1) should thus be useful in the selective study of transcription as it occurs in cells infected by the oncogenic virus SV40.

Studies of nondefective adenovirus 2-simian virus 40 hybrid viruses. IV. Characterization of the simian virus 40 ribonucleic acid species induced by wild-type simian virus 40 and by the nondefective hybrid virus, Ad2 + ND 1

Ad2(+)ND(1), a nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid virus, has been previously shown to contain a small segment of the SV40 genome covalently linked to Ad2 deoxyribonucleic acid (DNA). The SV40 portion of this hybrid virus has been characterized by relating the SV40-specific ribonucleic acid (RNA) sequences transcribed from the Ad2(+)ND(1) DNA to those transcribed from the DNA of SV40 itself. RNA-DNA hybridization-competition studies indicate that the SV40 component of Ad2(+)ND(1) consists of some, but not all, of that part of the SV40 genome which is transcribed early, i.e., prior to viral DNA replication, in SV40 lytic infection.

Quantitative in vitro measurement of simian virus 40 tumor-specific antigens

Humoral antibodies, specific for the SV40 tumor-specific transplantation antigen, can be detected by an in vitro cytotoxic assay. (51)Cr-labeled SV40-transformed target cells are selectively killed in the presence of specific antibody and rabbit complement. Inhibition of cytotoxicity can be used to measure the antigen concentration and specific activity on different SV40-transformed cell lines. The assay described has several advantages when compared to other methods currently available to detect the specific SV40 antigen: it is simple, rapid, objective, reproducible, and quantitative.

Studies of nondefective adenovirus 2-simian virus 40 hybrid viruses. II. Relationship of adenovirus 2 deoxyribonucleic acid and simian virus 40 deoxyribonucleic acid in the Ad2+ND genome

A nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid virus, Ad2(+)ND(1), has been plaque-isolated from an Ad2-SV40 hybrid population. This virus, unlike the defective Ad-SV40 hybrid populations previously described, replicates without the aid of nonhybrid adenovirus helper. Consequently, the hybrid virus deoxyribonucleic acid (DNA) can be obtained free of nonhybrid adenovirus DNA. The DNA of the Ad2(+)ND(1) virus was shown by ribonucleic acid (RNA)-DNA hybridization to consist of nucleotide sequences complementary to Ad2- and SV40-specific RNA. Techniques of equilibrium density and rate zonal centrifugation were employed to demonstrate that these Ad2 and SV40 nucleotide sequences were linked together in the same DNA molecules by alkali-resistant bonds. Calibration curves were established relating the amount of tritium-labeled SV40-specific RNA (prepared in vitro or in vivo) bound to given amounts of SV40 DNA in a hybridization reaction, and these curves were employed to determine the equivalent amount of SV40 DNA in the Ad2(+)ND(1) molecule. From the results obtained, it was estimated that 1% of the Ad2(+)ND(1) DNA consists of SV40 nucleotide sequences.

Interferon and transcription of early virus-specific RNA in cells infected with simian virus 40

Treatment with interferon reduced the content of early virus-specific RNA, as well as the content of an early viral protein (T antigen), in monkey cells acutely infected with simian virus 40 (SV40). This unexpected finding suggests either that the action of interferon involves inhibition of the transcription of early SV40 messenger RNA, or that the SV40 genome contains a "proto-early" gene whose product is required for the transcription of the remaining early genes.

Studies on nondefective adenovirus-simian virus 40 hybrid viruses. I. A newly characterized simian virus 40 antigen induced by the Ad2+ND 1 virus

The nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid virus, Ad2(+)ND(1), does not induce heat-labile SV40 T antigen but does induce a previously uncharacterized heat-stable SV40 antigen-the SV40 "U" antigen. This antigen is detectable by both immunofluorescence and complement fixation by using sera from hamsters with SV40 tumors. Sera from hamsters bearing SV40 tumors can be divided into two groups, those that react with both SV40 T and U antigens (T(+)U(+) sera) and those that react with SV40 T antigen only (T(+)U(-) sera). SV40 U-specific sera from monkeys immunized with Ad2(+)ND(1)-infected cells do not react with SV40 T antigen by immunofluorescence but do react with an antigen in the nucleus of SV40-transformed cells and with an early, cytosine arabinoside-resistant antigen present in the nucleus of SV40-infected cells. A heat-stable SV40 antigen detectable by complement fixation with T(+)U(+) hamster sera is present in extracts of SV40-induced hamster tumors and in cell packs of SV40-infected or -transformed cells. SV40 U-antigen synthesis by Ad2(+)ND(1) virus is partially sensitive to inhibitors of deoxyribonucleic acid synthesis, whereas U-antigen synthesis by SV40 virus is an early cytosine arabinoside-resistant event. As an early SV40 antigen differing from SV40 T antigen, U antigen may play a role in malignant transformation mediated by SV40.

Adenovirus type 2-simian virus 40 hybrid population: evidence for a hybrid deoxyribonucleic acid molecule and the absence of adenovirus-encapsidated circular simian virus 40 deoxyribonucleic acid

The deoxyribonucleic acid (DNA) from the adenovirus-encapsidated particles of the adenovirus type 2 (Ad2)-simian virus 40 (SV40) hybrid population plaque variant (Ad2(++) HEY), known to yield SV40 virus with high efficiency, was studied by equilibrium density centrifugation followed by ribonucleic acid-DNA hybridization employing virus-specific complementary ribonucleic acids synthesized in vitro. These techniques establish linkage between the Ad2 and SV40 components in the adenovirus-encapsidated particles of this population. The linkage is alkali-resistant and presumably covalent; thus, the Ad2 DNA and SV40 DNA are present in a hybrid molecule. Velocity centrifugation studies in alkaline sucrose gradients eliminated the possibility that supercoiled circular SV40 DNA is present in the adenovirus capsids. The DNA obtained from the adenovirus-encapsidated particles of the Ad2(++) HEY population appears to consist of nonhybrid Ad2 DNA and Ad2-SV40 hybrid DNA molecules.

Virus-specific deoxyribonucleic acid in simian virus 40-exposed hamster cells: correlation with S and T antigens

Several homologous hamster embryonic cell lines, transformed in association with simian virus (SV) 40 infection, were examined for the presence of deoxyribonucleic acid (DNA) complementary to SV40 ribonucleic acid (RNA) made in vitro. The methods employed permitted the detection of 10(-5) mug of viral DNA in 100 mug of cellular DNA, corresponding to one-fifth of an SV40 DNA molecule per cell. Those lines which contained both the SV40 surface (S) and tumor (T) antigens also contained DNA complementary to SV40 RNA synthesized in vitro. In contrast, neither of two lines which contained S, but not T, antigen contained detectable DNA complementary to SV40 RNA. These findings suggest that the production of S antigen does not depend upon the persistence of SV40 DNA in transformed cells.

In vitro transformation by the adenovirus-simian virus 40 hybrid viruses. V. Virus-specific ribonucleic acid in cell lines transformed by the adenovirus 2-simian virus 40 and adenovirus 12-simian virus 40 transcapsidant hybrid viruses

The ribonucleic acid-deoxyribonucleic acid hybridization technique was utilized to determine the presence of adenovirus (ad) and SV40 genetic information and to determine which ad genomes were present in clones of hamster cells transformed with the ad 2-SV40 and ad 12-SV40 transcapsidant hybrid virus populations. The results were correlated with the morphology of the transformed cells and colonies. It was found that cells transformed by either transcapsidant virus which had an SV40 morphology contained the ad 7 and SV40 genomes, whereas cells with a typical ad morphology contained only ad genetic information. Cells and colonies with morphological features of both ad- and SV40-transformed cells contained either the ad 2, or ad 12 genomes, depending on the transcapsidant used, together with the ad 7 and SV40 genomes. The results indicate the following: at least three different events occurred during transformation of hamster cells by the transcapsidant virus populations; the morphology of the resulting clones is determined by the viral genome(s) present; the linkage of the ad 7-SV40 genomes is confirmed since the ad 7- SV40 genomes were never found to be dissociated; the defective ad 7-SV40 genomes are capable of causing transformation; and the transcapsidant particle is probably composed of only ad 7 and SV40 genetic information.

A nondefective (competent) adenovirus-SV40 hybrid isolated from the AD.2-SV40 hybrid population

A new nondefective hybrid virus has been plaque-isolated from the Ad.2-SV40 hybrid population. This virus replicates efficiently with one-hit kinetics in both human embryonic kidney and African green monkey kidney cells, induces an SV40 specific antigen which is detectable by immunofluorescence and complement-fixation using sera from SV40 tumor-bearing hamsters, and produces SV40-specific RNA detectable by DNA-RNA hybridization. The SV40-specific antigen induced by this virus is heat-stable, sensitive to inhibitors of DNA synthesis, serologically different from SV40 T and viral antigens, and is an unrecognized SV40 antigen.