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

Synthesis of the Ad2+ND5-specified 42K protein is regulated posttranscriptionally in abortively infected monkey cells

In abortive infections of monkey cells by Ad2+ND5, the synthesis of the simian virus 40-specific 42,000-molecular-weight (42K) protein was reduced approximately 10-fold compared with a productive coinfection by Ad2+ND5 plus Ad2hr400 and about 20-fold compared with productive infections by Ad2+ND5 plus simian virus 40 or by Ad2+ND2 alone. However, the level of Ad2+ND5-specific mRNA was depressed twofold or less in abortive infections compared with productive infections. Moreover, the 42K mRNA isolated from abortive Ad2+ND5 infections translated in vitro with the same efficiency as the mRNA isolated from productive coinfections. This is analogous to the block to synthesis of the adenovirus fiber polypeptide in monkey cells (Anderson and Klessig, J. Mol. Appl. Genet. 2:31-43, 1983). Also like fiber protein, the increased level of the 42K protein found in productive infections was due to enhanced synthesis, not increased stability of the protein. Our results suggest that the synthesis of the Ad2+ND5-specified 42K protein and the adenovirus fiber protein are regulated in similar posttranscriptional manners.

Similar regulation of the synthesis of adenovirus fiber and of simian virus 40-specific proteins encoded by the helper-defective Ad2+SV40 hybrid viruses Ad2+ND5 and Ad2+ND4del

Human adenoviruses fail to multiply effectively in monkey cells. The block to the replication of these viruses can be overcome by coinfection with simian virus 40 (SV40) or when part of the SV40 genome is integrated into and expressed as part of the adenovirus type 2 (Ad2) genome, as occurs in several Ad2+SV40 hybrid viruses, such as Ad2+ND1, Ad2+ND2, and Ad2+ND4. The SV40 helper-defective Ad2+SV40 hybrid viruses Ad2+ND5 and Ad2+ND4del were analyzed to determine why they are unable to grow efficiently in monkey cells even though they contain the appropriate SV40 genetic information. Characterization of the Ad2+ND5-SV40-specific 42,000-molecular-weight (42K) protein revealed that this protein is closely related, but not identical, to the SV40-specific 42K protein of the SV40 helper-competent Ad2+ND2 hybrid virus. Although the minor differences between these proteins may be sufficient to account for the poor growth of Ad2+ND5 in monkey cells, the most striking difference between helper-competent Ad2+ND2 and helper-defective Ad2+ND5 is in the production of the SV40-specific protein after infection of monkey cells. Whereas synthesis of the SV40-specific proteins of Ad2+ND2 is very similar in human and in monkey cells, production of the 42K protein of Ad2+ND5 is dramatically reduced in monkey cells compared with human cells. Similarly, the synthesis of the SV40-specific proteins of Ad2+ND4del is markedly reduced in monkey cells. Thus, it is likely that both Ad2+ND5 and Ad2+ND4del are helper defective because of a block in the production of their SV40-specific proteins rather than because their SV40-specific proteins are nonfunctional. This block, like the block to adenovirus fiber synthesis, is overcome by coinfection with SV40, with helper-competent hybrid viruses, or with host range mutants of adenoviruses. This suggests that the synthesis of fiber and the synthesis of SV40-specific proteins are similarly regulated in Ad2+SV40 hybrid viruses.

Monoclonal antibodies against simian virus 40 tumor antigens: analysis of antigenic binding sites, using adenovirus type 2-simian virus 40 hybrid viruses

The antigenic binding sites of two monoclonal antibodies are located in the COOH-terminal region (clone 412) and probably in an internal region (clone 7) of simian virus 40 large T antigen. A third monoclonal antibody (clone 122), which has been shown to bind nonviral T antigen, does not react with HeLa cells infected with nondefective adenovirus type 2 (Ad2)-simian virus 40 hybrid viruses Ad2+ND1, Ad2+ND2, or Ad2+ND4.

Mechanisms of photodynamic inactivation of herpes simplex viruses: comparison between methylene blue, light plus electricity, and hematoporhyrin plus light

Herpes simplex virus (HSV) types 1 and 2 have been inactivated in vitro using low concentrations of methylene blue (MB), light (lambda) plus electricity (E), or hematoporphyrin derivative (HPD) plus lambda. Both techniques introduce single strand interruptions into viral DNA, but do not make double strand ruptions into viral DNA, but do not make double strand breaks. MB, lambda plus E-treated virions adsorb normally to and penetrate susceptible cells, whereas HSV inactivated with HPC and light does not. This difference is emphasized by the induction of new viral and cell DNA synthesis after infection with MB, lambda plus E-treated virions, whereas only cell, DNA but no HSV DNA, is made subsequent to HPD and lambda exposure. These observations reflect disparate mechanisms of viral inactivation. A block(s) in viral maturation, subsequent to viral DNA synthesis, occurs as a result of treatment with MB, lambda and E, whereas HPD plus lambda-treated particles fail to enter a susceptible cell, and therefore do not initiate an infection.

Identification of amber and ochre mutants of the human virus Ad2+ND1

Although human adenoviruses grow poorly in monkey cells, this defect can be overcome either by coinfection of cells with simian virus 40 (SV40) or by insertion of the relevant portion of the SV40 genome into the adenovirus genome to form an adenovirus-SV40 hybrid virus. The nondefective adenovirus-2-SV40 hybrid virus, Ad2+ND1, contains an insertion of 17% of the SV40 genome, which codes for at least part of a 30,000 dalton protein. A set of Ad2+ND1 host-range mutants that have lost the ability to grow in monkey cells and behave as point mutants fail to synthesize the 30,000 dalton ND1 protein. Translation in vitro of SV40-specific mRNA from mutant-infected cells produces unique short polypeptides instead of the 30,000 dalton protein. Here we show that this set of host-range mutants includes both ochre and amber nonsense mutations. When the SV40-specific mRNA from the host-range mutants is translated in vitro to produce the polypeptide fragments, yeast suppressor tRNA can partially restore synthesis of wild-type-size 30,000 dalton protein. By this assay, one mutant is ochre and two are amber.

Evidence for simian virus 40 (SV40) coding of SV40 T-antigen and the SV40-specific proteins in HeLa cells infected with nondefective adenovirus type 2-SV40 hybrid viruses

HeLa cells infected with the nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid viruses (Ad2(+)ND1, Ad2(+)ND2, Ad2(+)ND4, and Ad2(+)ND5) synthesize SV40-specific proteins ranging in size from 28,000 to 100,000 daltons. By analysis of their methionine-containing tryptic peptides, we demonstrated that all these proteins shared common amino acid sequences. Most methionine-containing tryptic peptides derived from proteins of smaller size were contained within the proteins of larger size. Seventeen of the 21 methionine-containing tryptic peptides of the largest SV40-specific protein (100,000 daltons) from Ad2(+)ND4-infected cells were identical to methionine-containing peptides of SV40 T-antigen immunoprecipitated from extracts of SV40-infected cells. All of the methionine-containing tryptic peptides of the Ad2(+)ND4 100,000-dalton protein were found in SV40 T-antigen immunoprecipitated from SV40-transformed cells. All SV40-specific proteins observed in vivo could be synthesized in vitro using the wheat germ cell-free system and SV40-specific RNA from hybrid virus-infected cells that was purified by hybridization to SV40 DNA. As proof of identity, the in vitro products were shown to have methionine-containing tryptic peptides identical to those of their in vivo counterparts. Based on the extensive overlap in amino acid sequence between the SV40-specific proteins from hybrid virus-infected cells and SV40 T-antigen from SV40-infected and -transformed cells, we conclude that at least the major portion of the SV40-specific proteins cannot be Ad2 coded. From the in vitro synthesis experiments with SV40-selected RNA, we further conclude that the SV40-specific proteins must be SV40 coded and not host coded. Since SV40 T-antigen is related to the SV40-specific proteins, it must also be SV40 coded.

Specificity of initiation of transcription of simian virus 40 DNA I by Escherichia coli RNA polymerase: identification and localization of five sites for initiation with [gamma-32P]ATP

Simian virus 40 (SV40) DNA I was transcribed with Escherichia coli RNA polymerase in the presence of gamma-32P-labeled ribonucleoside triphosphates in order to investigate the specificity of initiation of in vitro transcription. ATP and GTP served as predominant initiating nucleotides, the former being incorporated about twice as much as the latter. Cleavage of [gamma-32P]ATP-labeled SV40 complementary RNA (cRNA) with T1 RNase followed by homochromatographic analysis of the resultant 5' initiation fragments revealed the presence of four specific initiation fragments 6 to 9 nucleotides in length, designated AI, AII, AIIIa, and AIIIb. By means of hybridization of [gamma-32P]ATP-labeled SV40 cRNA to DNA from specific adenovirus 2-SV40 hybrids and specific restriction endonuclease fragments of SV40 DNA before chromatographic analysis, it was possible to identify and determine approximate localizations of five [gamma-32P]ATP initiation sites on the SV40 genome: one in Hin-G close to the Hin-G-B junction, giving rise to the AII fragment, two in the overalpping fragment Hin-A-Hae-A,giving rise to AI and AIII fragments, and two in the fragment Hin-A-Hae-E, also giving rise to AI and AIII fragments. All five sites either fall within or lie near regions of the genome that are cleaved by S1 nuclease and subject to partial alkaline denaturation. These five sites lie on the minus strand of SV40 DNA and initiate RNAs that are copied in a leftward direction. Cleavage of [gamma-32P]GTP-labeled cRNA with pancreatic RNase liberated three major 5' initiation fragments of short length, GI, GII, and GIII, suggesting the presence of three principal GTP initiation sites.

Simian virus 40 tumor-specific proteins: subcellular distribution and metabolic stability in HeLa cells infected with nondefective adenovirus type 2-simian virus 40 hybrid viruses

HeLa cells infected with adenovirus type 2 (Ad2)-simian virus 40 (SV40) hybrid viruses produce several SV40-specific proteins. These include the previously reported 28,000-dalton protein of Ad2+ND1, and 42,000- and 56,000-dalton proteins of Ad2+ND2, the 56,000-dalton protein of Ad2+ND4, and the 42,000-dalton protein of Ad2+ND5. In this report, we extend the list of SV40-specific proteins induced by Ad2+ND4 to include proteins of apparent molecular weights of 28,000 42,000, 60,000, 64,000, 72,000, 74,000, and a doublet of 95,000. Cell fractionation studies demonstrate that the SV40-specific proteins are detectable in the nuclear, cytoplasmic, and plasma membrane fractions. By pulse-chase and cell fractionation experiments, three classes of SV40-specific proteins can be distinguished with regard to metabolic stability: (i) unstable in the cytoplasmic but stable in the nuclear and plasma membrane fractions; (ii) stable in the nuclear, cytoplasmic, and plasma membrane fractions; and (iii) unstable in all subcellular fractions. Immunoprecipitation of infected cell extracts demonstrates that most of the above proteins share antigenic determinants with proteins expressed in hamsters bearing SV40-induced tumors. Only the 42,000-dalton protein of Ad2+ND5 is not immunoprecipitable.

Content and expression of integrated viral DNA in hamster cells transformed by nondefective adenovirus type 2- simian virus 40 hybrid viruses

Hamster cells transformed by adenovirus 2 (Ad2) and five nondefective Ad2-simian virus 40 (SV40) hybrid viruses are all of the Ad2-transformed phenotype. All lines accumulate Ad2 RNA and Ad2 T antigen; two hybrid-transformed lines accumulate SV40 RNA, but only one contains detectable amounts of SV40 antigens. We examines selected lines from this group of transformed hamster cells for Ad2 DNA content and viral RNA expression by using hydroxyapatite chromatography and separated strands of labeled viral DNA as probes. All lines studies contain 1 to 2 Ad2 genome equivalents per haploid equivalent of cell DNA. The expression of Ad2 RNA exhibits two distinct patterns. In one pattern, transcription of the heavy strand of Ad2 DNA is less than that of the light strand, whereas in the second pattern of Ad2 RNA expression the extent of heavy-strand transcription is greatly increased. In the two lines containing SV40 RNA, the entire SV40 (-) strand is transcribed; the (+) strand is not expressed in these cells. These patterns of viral RNA expression suggest the possibility that host promoters may play a role in regulating transcription of integrated viral DNA.

Conditional lethal mutants of adenovirus type 2-simian virus 40 hybrids. II. Ad2+ND1 host-range mutants that synthesize fragments of the Ad2+ND1 30K protein

Adenovirus type 2 (Ad2) grows 1,000 times less well in monkey cells than in human cells. This defect can be overcome, not only upon co-infection of cells with simian virus 40 (SV40), but also when the relevant part of the SV40 genome is integrated into the adenovirus genome to form an adenovirus-SV40 hybrid virus. We have used the nondefective Ad2-SV40 hybrid virus Ad2+ND1, which contains an insertion of 17% of the SV40 genome, to isolate host-range mutants which are defective in growth on monkey cells although they grow normally on human cells. Like Ad2, these mutants are defective in the synthesis of late proteins in monkey cells. A 30,000-molecular-weight protein (30K), unique to Ad2+ND1-infected cells, can be synthesized in vitro, using Ad2+ND1 mRNA that contains SV40 sequences. 30K is not seen in cells infected with those host-range mutants that are most defective in growth on monkey cells, and translation in vitro of SV40-specific mRNA from these cells produces new unique polypeptides, instead of 30K. Genetic and biochemical analyses indicate that these mutants carry point mutations rather than deletions.

Simian virus 40-specific proteins in HeLa cells infected with nondefective adenovirus 2-simian virus 40 hybrid viruses

The synthesis of simian virus 40 (SV40)-specific proteins in HeLa cells infected with the nondefective adenovirus 2 (Ad2)-SV40 hybrid viruses, Ad2+ND2, Ad2+ND3, Ad2+ND4, and Ad2+ND5, was investigated. Infected-cell proteins were labeled with radioactive amino acids late after infection, when host protein synthesis was shut off, and analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. All polypeptides normally seen in Ad2-infected cells were found in cells infected by the hybrid viruses. In addition to the Ad2-specific proteins, cells infected with Ad2+ND2 contain two SV40-specific proteins with apparent molecular weights of 42,000 and 56,000, cells infected with Ad2+ND4 contain one protein with an apparent molecular weight of 56,000, and cells infected with Ad2+ND5 contain one protein with an apparent molecular weight of 42,000. Cells infected with Ad2+ND3 do not contain detectable amounts of proteins not seen during Ad2 infection. Pulse-chase experiments demonstrate that the SV40-specific proteins induced by Ad2+ND2, Ad2+ND4, and Ad2+ND5 are metabolically unstable. These proteins are not present in purified virions. Two nonstructural Ad2-specific proteins have been demonstrated in Ad2 and hybrid virus-infected cells which have a smaller apparent molecular weight after a short pulse than after a pulse followed by a chase. The molecular weight increase during the chase may be caused by the addition of carbohydrate to a polypeptide backbone.

Adenovirus transcription. II. RNA sequences complementary to simian virus 40 and adenovirus 2DNA in AD2+ND1- and AD2+ND3-infected cells

The genomes of the two nondefective adenovirus 2/simian virus 40 (Ad2/SV 40) hybrid viruses, nondefective Ad2/SV 40 hybrid virus 1 (Ad2+ND1) and nondefective hybrid virus 3 (Ad2+ND3), WERE FORMED BY A DELETION OF ABOUT 5% OF Ad2 DNA and insertion of part of the SV40 genome. We have compared the cytoplasmic RNA synthesized during both the early and late stages of lytic infection of human cells by these hybrid viruses to that expressed in Ad2-infected and SV40-infected cells. Separated strands of the six fragments of 32P-labeled Ad2 DNA produced by cleavage with the restriction endonuclease EcoRI (isolated from Escherichia coli) and the four fragments of 32P-labeled SV40 DNA produced by cleavage with both a restriction nuclease isolated from Haemophilus parainfluenzae, Hpa1, and EcoRI were prepared by electrophoresis of denatured DNA in agarose gels. The fraction of each fragment strand expressed as cytoplasmic RNA was determined by annealing fragmented 32P-labeled strands to an excess of cellular RNA extracted from infected cells. The segment of Ad2 DNA deleted from both hybrid virus genomes is transcribed into cytoplasmic mRNA during the early phase of Ad2 infection. Hence, we suggest that Ad2 codes for at least one "early" gene product which is nonessential for virus growth in cell culture. In both early Ad2+ND1 and Ad2+ND3-infected cells, 1,000 bases of Ad2 DNA adjacent to the integrated SV40 sequences are expressed as cytoplasmic RNA but are not similarly expressed in early Ad2-infected cells. The 3' termini of this early hybrid virus RNA maps in the vicinity of 0.18 on the conventional SV40 map and probably terminates at the same position as early lytic SV40 cytoplasmic RNA. Therefore, the base sequence in this region of SV40 DNA specifies the 3' termini of early messenger RNA present in both hybrid virus and SV40-infected cells.

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.

Properties of cells transformed by DNA tumor viruses

Transformation by the papovaviruses, SV40 and polyoma, is reviewed briefly, including factors that affect the frequency of transformation. Virus markers useful in the determination of the etiology of virus-free tumors are described, including viral DNA, viral mRNA, virus-induced antigens, and the rescue of infectious virus. Finally, the evidence that viral genes are involved in the maintenance of transformation is presented.

Conditional lethal mutants of adenovirus 2-simian virus 40 hybrids. I. Host range mutants of Ad2+ND1

Human adenovirus type 2 (Ad2) grows poorly in monkey cells, although this defect can be overcome by co-infection with simian virus 40 (SV40). The nondefective Ad2-SV40 hybrid virus, Ad2(+)ND1, replicates efficiently in both human and African green monkey kidney cells, presumably due to the insertion of SV40 sequences into the Ad2 DNA. Several mutants of Ad2(+)ND1 have been isolated that grow and plaque poorly in monkey cells, although they retain the ability to replicate and plaque efficiently in HeLa cells. One of these mutants (H39) has been examined in detail. Studies comparing the DNA of the mutant with Ad2(+)ND1 either by the cleavage patterns produced by Escherichia coli R.RI restriction endonuclease digestion or by heteroduplexing reveal no differences. The pattern of protein synthesis of Ad2(+)ND1 and H39 in monkey cells is quite different with the mutant resembling Ad2, which is defective in the synthesis of late proteins. However, in human cells, the proteins synthesized by H39 and the parent Ad2(+)ND1 are very similar. The production of SV40 U antigen in H39-infected cells is different from that in Ad2(+)ND1-infected cells. Finally, the growth of H39 in monkey cells can be complemented by SV40.

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.

Studies of nondefective adenovirus 2-simian virus 40 hybrid viruses. IX. Template topography in the early region of simian virus 40

The DNAs of the five nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid viruses contain overlapping segments of the early region of wild-type SV40 DNA. The complementary DNA strands of these five viruses have been separated with synthetic polyribonucleotides in isopycnic cesium chloride gradients. The relative amounts of early and late SV40 template in the DNA of each virus were determined by RNA-DNA hybridization with late lytic SV40 RNA, which contains sequences complementary to both templates. From the distribution of early and late templates in the five overlapping SV40 segments, we conclude that either the entire early region of SV40 is symmetrically transcribed in vivo, or, more probably, that the early SV40 templates are not contiguous.

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.

A colinear map relating the simian virus 40 (SV40) DNA segments of six adenovirus-SV40 hybrids to the DNA fragments produced by restriction endonuclease cleavage of SV40 DNA

The simian virus 40 (SV40) DNA segments present in a series of adenovirus-SV40 hybrids have been mapped with respect to the sites of cleavage of SV40 DNA by restriction endonucleases. Two approaches have been used. First, nucleic acid hybridizations were performed between equimolar quantities of the denatured DNAs of SV40 and each hybrid virus and the radiolabeled transcripts of 11 DNA fragments obtained by cleavage of SV40 DNA by restriction endonuclease from Hemophilus influenzae. Secondly, selected fragments of SV40 DNA produced by the H. influenzae or H. parainfluenzae restriction endonucleases were used to form heteroduplex DNA molecules with adenovirus and adenovirus-SV40 hybrid DNA, which were then analyzed by electron microscopy. The two sets of data were consistent and have permitted alignment of the map of the SV40 segments of the hybrid viruses with the H. influenzae and H. parainfluenzae cleavage maps of SV40. Since cells infected with some of the hybrid viruses contain one or more SV40-specific antigens, the genetic determinants of these antigens could be localized on the cleavage map.

Induction of cellular DNA synthesis by the nondefective Adenovirus 2-Simian virus 40 hybrid viruses

Induction of cellular DNA synthesis by the nondefective adenovirus 2-simian virus 40 hybrid viruses was examined in monkey and hamster cells. It was not possible to discriminate the effects of the hybrid viruses from those of wild-type adenovirus 2.

Studies of nondefective Adenovirus 2-Simian virus 40 hybrid viruses. 8. Association of Simian virus 40 transplantation antigen with a specific region of the early viral genome

Two of the five nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrids induce SV40 transplantation resistance in immunized hamsters. These two hybrids, Ad2(+)ND(2) and Ad2(+)ND(4), contain 32 and 43% of the SV40 genome, respectively. The pattern of induction of SV40 transplantation antigen (TSTA) by the various hybrids differentiates TSTA from both SV40 U and T antigens. Since the SV40 RNA induced by both these hybrids is early SV40 RNA, these findings confirm that TSTA is an early SV40 function. By combining available data on SV40 antigen induction by these hybrids with electron microscopy heteroduplex mapping studies, the DNA segment responsible for the induction of SV40 TSTA can be inferred to lie in the region between 0.17 and 0.43 SV40 units from the site on the SV40 chromosome cleaved by E. coli R(1) restriction endonuclease.

Use of nondefective adenovirus-simian virus 40 hybrids for mapping the simian virus 40 genome

A series of viable recombinants between adenovirus 2 (Ad2) and simian virus 40 (SV40) (nondefective Ad2-SV40 hybrids) have been isolated. The members of this series (designated Ad2(+)ND(1) through Ad2(+)ND(5)) differ from one another in the early SV40-specific antigens and the SV40-specific RNA species which they induce in infected cells. They also contain different amounts of SV40 DNA as shown by RNA-DNA hybridization techniques. We have examined the structure of the DNA molecules from these hybrids, using electron microscope heteroduplex mapping techniques. Each hybrid was found to contain a single segment of SV40 DNA of characteristic size covalently inserted at a unique location in the adenovirus 2 DNA molecule. The SV40 segments of the various hybrids formed an overlapping series with a common end point. When the results of the electron microscopic study were combined with data on antigen induction, it was found that a self-consistent map could be constructed which related specific regions of the SV40 genome to the induction of specific antigens. The order of these early SV40 antigen inducing regions in the SV40 DNA segments contained in the nondefective hybrids is: U antigen, tumor specific transplantation antigen, and T antigen with the U antigen region being nearest the common end point.

Mapping of simian virus 40 early functions on the viral chromosome

The simian virus 40 (SV40) DNA segment in the nondefective adenovirus 2-SV40 hybrid, Ad2(+)ND(4), is colinear with the segment between 0.11 and 0.59 SV40 fractional length from the site at which the R(1) restriction endonuclease cleaves SV40 DNA. This specifies the region of the SV40 DNA molecule which induces the early SV40 antigens: U antigen, tumor specific transplantation antigen, and T antigen. A variant of Ad2(+)ND(4), called Ad2(+)ND(4del), was found which has a deletion of the DNA segment between 0.50 and 0.57 SV40 fractional length from the R(1) endonuclease cleavage point.

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.

Preferred site for initiation of RNA transcription by Escherichia coli RNA polymerase within the simian virus 40 DNA segment of the nondefective adenovirus-simian virus 40 hybrid viruses Ad2 + ND 1 and Ad2 + ND 3

The DNA of simian virus 40 (SV40) was transcribed into RNA by Escherichia coli RNA polymerase at 18 to 24 C after synchronization of the initiation of RNA synthesis. After a brief synthetic period the RNA product contained relatively large amounts of sequences derived from a limited segment of SV40 DNA. The source for this pulse-labeled RNA was found to be a portion of the segment of SV40 DNA included within the nondefective adenovirus (Ad)-SV40 hybrid viruses, Ad2(+)ND(1) and Ad2(+)ND(3). After synthesis with [gamma-(32)P] ATP, Ad2(+)ND(1) and Ad2(+)ND(3) DNA transcripts contained an initial sequence missing from Ad2 transcripts. This sequence was identified as an initiation sequence for polymerase transcription of the SV40 DNA. Thus, there is a preferred site for initiation of in vitro transcription on the segment of SV40 DNA common to the nondefective Ad2(+)ND(1) and Ad2(+)ND(3) hybrid viruses.