Regulation of herpesvirus thymidine kinase activity in LM(TK) cells transformed by ultraviolet light-irradiated herpes simplex virus

Properties of cells carrying the herpes simplex virus type 2 thymidine kinase gene: mechanisms of reversion to a thymidine kinase-negative phenotype

We have isolated cells with a thymidine kinase-negative (tk(-)) phenotype from cells which carry the herpes simplex virus type 2 tk gene by selection in 5-bromodeoxyuridine or 9-(2-hydroxyethoxymethyl)guanine. Both selection routines generated revertants with a frequency of 10(-3) to 10(-4), and resistance to either compound conferred simultaneous resistance to the other. tk(-) revertants fell into three classes: (i) cells that arose by deletion of all virus sequences, (ii) cells that had lost the virus tk gene but retained a nonselected virus-specific function and arose by deletion of part of the virus-specific sequence, and (iii) cells that retained the potential to express all of the virus-specific functions of the parental cells and retained all of the virus-specific DNA sequences.

Assessment of the specificity of cytotoxic T lymphocytes for the nucleoprotein of Pichinde virus using recombinant vaccinia viruses

Pichinde virus (PV) infection of mice results in induction of a strong H-2 restricted, virus-specific cytotoxic T lymphocyte (CTL) response and rapid clearance of the virus. To define the specificities of CTL induced by PV infection, we constructed vaccinia virus recombinants containing cloned cDNAs corresponding to full-length (VVNP) and a truncated form (VVNP 51-561) of the nucleoprotein (NP) gene of PV. Radioimmunoprecipitation analysis of infected cell lysates indicated that VVNP expressed a PV-specific product identical in size to that of authentic NP, while vaccinia virus recombinants containing truncated NP produced a polypeptide consistent with the synthesis of amino acids 51-561 of Pichinde virus NP. Interestingly, cells infected with VVNP synthesized easily detectable, but much lower levels of nucleoprotein relative to both PV and VVNP51-561. Primary virus-specific CTL induced in three different strains of inbred mice following intravenous infection with PV were able to lyse syngeneic target cells infected with PV but did not markedly lyse syngeneic targets expressing full-length or truncated NP following recombinant vaccinia virus infection. Similarly, secondary anti-PV specific CTL generated following in vitro restimulation by PV or selectively restimulated with vaccinia recombinants did not significantly lyse target cells expressing NP. Further, infection of mice with VVNP and VVNP51-561 did not induce CTLs specific for PV and did not prime mice for the generation of memory anti-PV CTL in vivo. These results suggest that PV gene products other than NP, such as the GPC or L protein, contain the major target epitope(s) recognized by PV-specific CTL.

Differential metabolism of (E)-5-(2-iodovinyl)-2'-deoxyuridine (IVDU) by equine herpesvirus type 1- and herpes simplex virus-infected cells

Thymidine kinase (TK) enzymes encoded by herpes simplex viruses types 1 and 2 (HSV-1, HSV-2), and equine herpesvirus type 1 (EHV-1) catalyze the phosphorylation of thymidine (dThd) and (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU). The replication of HSV-1 is sensitive to BVDU, but the replication of HSV-2 and EHV-1 is not. To investigate the differential sensitivity of the viruses to halogenated vinyldeoxyuridine drugs, the phosphorylation of 125I-labeled (E)-5-(2-iodovinyl)-2'-deoxyuridine (IVDU) was studied. Cytosol enzymes from cells infected by HSV-2 and EHV-1 phosphorylated [125I]IVDU to the monophosphate, IVDUMP, but did not convert IVDUMP to higher di- plus triphosphates (IVDUDP plus IVDUTP) forms. In contrast, enzymes from HSV-1-infected cells converted [125I]IVDU to radioactive IVDUMP and IVDUDP plus IVDUTP. Experiments with mixtures of EHV-1- and HSV-1-induced enzymes showed that the EHV-1 enzyme did not inhibit formation of the IVDUDP plus IVDUTP by the HSV-1 enzyme. With [125I]IVDU as substrate, the Km values for the EHV-1 and HSV-1 TKs were 1.82 and 0.34 microM, respectively, and the Ki (dThd) value for the EHV-1 TK was 0.35 microM. In vivo experiments showed that HSV-1-infected cells converted IVDU to the mono- and the di- plus triphosphate forms. In contrast, EHV-1-infected cells converted IVDU to the monophosphate to a lesser extent than did HSV-1-infected cells, and did not produce the di- plus triphosphates. Thus, inefficient phosphorylation of the monophosphates probably contributes to the insensitivity of EHV-1 replication to IVDU, as it does to the insensitivity of HSV-2 replication to this drug.

In cell lines constitutively synthesizing a temperature-sensitive ICP4 protein of herpes simplex virus type 1, amount and function of ICP4 are both regulated by temperature

We have established two cell lines that constitutively synthesize a temperature-sensitive form of ICP4, the herpes simplex virus immediate-early protein that activates early and late transcription. ICP4 in both cell lines was confirmed to be functionally temperature sensitive when tested by complementation of an ICP4 deletion mutant virus for expression of viral early and late genes. When grown at the permissive temperature the two cell lines contained approximately 5 and 25%, respectively, of the ICP4 present in control HSV-infected cells. If the cells were grown at the nonpermissive temperature, ICP4 levels were reduced by approximately fourfold; a twofold reduction was observed in control cells synthesizing the wild-type protein. The lower levels of ICP4 at the nonpermissive temperature were the result of two effects: a decrease in mRNA which was similar in cells producing the mutant or wild-type form of ICP4 and a more rapid turnover of the protein which was greater for the mutant than for the wild-type form. Our observations of lower levels of ICP4 in producer cells differ from published reports of overproduction of immediate-early proteins at the nonpermissive temperature in human or hamster cells infected with ICP4 temperature-sensitive mutant viruses. This discrepancy may be related to cell species differences since we observed only a modest twofold overproduction of immediate-early proteins at the nonpermissive temperature in infections of mouse cell lines with an ICP4 temperature-sensitive mutant virus.

Phosphorylation of nucleoside analogs by equine herpesvirus type 1 pyrimidine deoxyribonucleoside kinase

Replication of equine herpesvirus type 1 (EHV-1) was sensitive to 9-(1,3-dihydroxy-2-propoxymethyl)guanine(DHPG) but relatively resistant to E-5-(2-bromovinyl)-2'-deoxyuridine (BVDU). Likewise, plaque formation by EHV-1 was inhibited by DHPG, but not by BVDU. Plaque formation by a thymidine kinase-negative (tk-) mutant of EHV-1 was not inhibited by DHPG. In order to investigate biochemical mechanisms determining the differential sensitivity of EHV-1 to these drugs, the EHV-1-encoded thymidine kinase enzyme activity (TK)1 was partially purified from EHV-1-infected cells and analyzed. The EHV-1-induced enzyme utilized both ATP and CTP as phosphate donors and differed in relative electrophoretic mobility from the TKs of mock-infected and HSV-1-infected cells. Phosphorylation of 3H-dThd by the EHV-1 TK was inhibited by AraT, IdUrd, BVDU, and DHPG. The EHV-1 TK phosphorylated 125I-dCyd and 3H-ACV. The results indicate that EHV-1 encodes a pyrimidine deoxyribonucleoside kinase with broad nucleoside substrate specificity. These observations suggest that the failure of BVDU to inhibit EHV-1 replication is not attributable to an inability of the EHV-1 TK to phosphorylate BVDU, but may result from the incapacity of the viral TK to convert BVDU monophosphate to the triphosphate or from lack of inhibitory effect of BVDU triphosphate on viral DNA polymerase reactions.

Expression of the cloned S4 gene of reovirus serotype 3 in transformed eucaryotic cells: enrichment of the viral protein in the crude initiation factor fraction

The sigma 3 protein of reovirus is believed to play a role in the control of protein synthesis in reovirus-infected cells. In this paper we describe the establishment of a line of L-cells expressing the sigma 3 protein from the cloned S4 gene of reovirus serotype 3, under the control of the SV40 early promoter. The protein was enriched in the crude initiation factor fraction prepared by a high-salt wash of ribosomes. There was no apparent detrimental effect on the cell line.

Thymidine kinase-deficient herpes simplex virus type 2 genital infection in guinea pigs

In guinea pigs, thymidine kinase-producing strains of herpes simplex virus type 2 replicated to high titer in the vagina and spinal cord, and animals developed severe clinical disease. Infection with thymidine kinase-deficient virus resulted in similar vaginal virus titers; however, animals exhibited little or no clinical illness and only low titers of virus were detected in spinal cord homogenate cultures. Neural and extraneural latent infection as well as recurrent infection were noted in animals inoculated with either thymidine kinase-producing or -deficient viruses. These data suggest that neural pathways are important in the pathogenesis of genital herpes and that virus-coded thymidine kinase may influence virulence but is not required for latency.

Insertion mutagenesis to increase secondary structure within the 5' noncoding region of a eukaryotic mRNA reduces translational efficiency

The thymidine kinase gene of herpes simplex virus 1 was mutated by inserting oligodeoxynucleotide linkers into the region of the gene corresponding to the 5' untranslated portion of the mRNA. These linkers, when transcribed into mRNA, might be expected to form hairpin loops and hence to increase the secondary structure of the 5' end of the mRNA. Thymidine kinase insertion derivatives were examined in vivo and in vitro to determine translational efficiency. For the in vivo studies, thymidine kinase insertion derivatives were transfected into thymidine kinase deficient L cells alone and together with a selectable dominant marker, or were assayed in the COS-1 transient expression system. For in vitro studies, thymidine kinase insertion derivatives were subcloned into pSP64. Capped transcripts were analyzed for their ability to bind ribosomes and translate in rabbit reticulocyte lysates and wheat-germ extracts. The results demonstrate that translation efficiency is decreased as the number of linkers is increased and support the view that excessive secondary structure at the 5' end of eukaryotic mRNA impedes translation.

Effects of deletions on expression of the herpes simplex virus thymidine kinase gene from the intact viral genome: the amino terminus of the enzyme is dispensable for catalytic activity

We have transferred two deletions affecting the 5' end of the herpes simplex virus thymidine kinase (TK) gene into the intact viral genome. One, extending from -12 to +189, had no effect on TK mRNA synthesis and only a small effect on TK activity, although the first 27 codons of the TK polypeptide were deleted. The other, extending from -85 to +85, severely impaired TK mRNA synthesis. We conclude that the amino terminus of the TK polypeptide is dispensable for catalytic activity, and that expression of TK in viral infections requires some of the same promoter elements used in uninfected cells.

A detailed analysis of an HSV-1 early promoter: sequences involved in trans-activation by viral immediate-early gene products are not early-gene specific

This report describes a detailed analysis of the functional DNA sequences within the HSV-1 glycoprotein D gene promoter. The transcriptional activity of deletion and insertion promoter mutants was studied after both trans activation, mediated by viral products, and cis activation by a linked SV40 enhancer. Two G-rich areas (upstream of a TATA signal) were identified as important regions of the promoter. These "upstream" signals were active in both orientations. A functional TATA-box region was detected. A second region, not homologous to the concensus TATA sequence, also appeared to have a role in the positioning of the RNA cap-sites, which included both purine and pyrimidine 5' ends. Deletion of the cap-site region resulted in a moderate reduction in transcription. All the promoter elements were important for both cis and trans activated transcription. No sequence specific for viral (trans) regulation was detected, implying that Early promoters are not distinguished by specific sequences. Since HSV-1 and some other animal viruses can activate transcription from unrelated promoters, this process is probably non-specific and applicable to many, particularly extra-chromosomal, genes. The possible mechanisms of this activation are discussed.

Expression of herpes simplex virus beta and gamma genes integrated in mammalian cells and their induction by an alpha gene product

The proteins of herpes simplex virus type 1 (HSV-1) form three kinetic groups termed alpha, beta, and gamma, whose synthesis is regulated in a cascade fashion. alpha products are synthesized first during infection, and they are required for synthesis of beta and gamma proteins. To examine the expression of several HSV-1 beta and gamma genes in the absence of alpha functions, we transferred into mammalian cells a plasmid containing a region of the HSV-1 genome that codes for only beta and gamma genes (0.315 to 0.421 map units). We found stable integration of at least one copy of the intact plasmid in each cell line. Four HSV-1 transcripts of the beta and gamma classes were transcribed constitutively in the cells, including the genes for glycoprotein B and DNA-binding protein. No constitutive synthesis of these two proteins could be demonstrated, however. The integrated HSV-1 genes responded to viral regulatory signals in that they could be induced by infection with HSV-1 mutants resulting in a high level of synthesis of both glycoprotein B and DNA-binding protein. The HSV-1 alpha gene product ICP4 was necessary for this induction, and it was found to be most efficient at a low multiplicity of infection. Functional expression of four genes was demonstrated in that the cell lines complemented infecting HSV-1 temperature-sensitive mutants. The same genes were not available for homologous recombination with infecting virus, however, since no recombinant wild-type virus could be detected. These data demonstrate that HSV-1 beta and gamma genes can be transcribed in the absence of alpha functions in mammalian cells, but that they still respond to HSV-1 regulatory signals such as the alpha gene product ICP4.

Expression of herpes simplex virus beta and gamma genes integrated in mammalian cells and their induction by an alpha gene product

The proteins of herpes simplex virus type 1 (HSV-1) form three kinetic groups termed alpha, beta, and gamma, whose synthesis is regulated in a cascade fashion. alpha products are synthesized first during infection, and they are required for synthesis of beta and gamma proteins. To examine the expression of several HSV-1 beta and gamma genes in the absence of alpha functions, we transferred into mammalian cells a plasmid containing a region of the HSV-1 genome that codes for only beta and gamma genes (0.315 to 0.421 map units). We found stable integration of at least one copy of the intact plasmid in each cell line. Four HSV-1 transcripts of the beta and gamma classes were transcribed constitutively in the cells, including the genes for glycoprotein B and DNA-binding protein. No constitutive synthesis of these two proteins could be demonstrated, however. The integrated HSV-1 genes responded to viral regulatory signals in that they could be induced by infection with HSV-1 mutants resulting in a high level of synthesis of both glycoprotein B and DNA-binding protein. The HSV-1 alpha gene product ICP4 was necessary for this induction, and it was found to be most efficient at a low multiplicity of infection. Functional expression of four genes was demonstrated in that the cell lines complemented infecting HSV-1 temperature-sensitive mutants. The same genes were not available for homologous recombination with infecting virus, however, since no recombinant wild-type virus could be detected. These data demonstrate that HSV-1 beta and gamma genes can be transcribed in the absence of alpha functions in mammalian cells, but that they still respond to HSV-1 regulatory signals such as the alpha gene product ICP4.

DNA sequence elements required for regulated expression of the HSV-1 glycoprotein D gene lie within 83 bp of the RNA capsites

The genes of Herpes simplex virus type 1 (HSV-1) are classified into three temporally regulated groups. The Immediate-Early (IE) genes are transcribed first by the pre-existing transcription apparatus of the cell. The Early genes are transcribed only after IE-gene expression, and finally the Late genes are activated. The control of transcription of the HSV-1 glycoprotein D (gD) gene (an Early function) was studied by quantitative S1 mapping of RNA produced in HSV-1 infected HeLa cells after short-term transfection experiments using plasmids containing the gD promoter linked to the rabbit beta-globin gene. The viral promoter in the plasmid was activated in the same way as that in the virus itself; the RNA showed a similar time-course of appearance, dependence on prior IE-gene expression and pattern of RNA cap-sites. Deletion analysis showed that the DNA sequences necessary for Early promoter activation lie within 83 bp of the RNA cap-sites in this instance. Surprisingly, a plasmid-borne beta-globin promoter was also activated by HSV-1 infection. The mechanism of this activation, and DNA sequence similarities between the promoters of HSV-1 Early and rabbit beta-globin genes are discussed.

Nucleotide sequence of the herpes simplex virus type 2 thymidine kinase gene

We have determined the complete nucleotide sequence of the thymidine kinase gene of herpes simplex virus (HSV) type 2 strain 333. The sequence of the thymidine kinase gene exhibits an open translational reading frame of 1,128 nucleotides encoding a protein of 376 amino acids. The DNA sequence was compared with that of the HSV type 1 thymidine kinase gene from strain MP (S. L. McKnight, Nucleic Acids Res. 8:5949-5964, 1980) and from strain CL 101 (M. J. Wagner, J. A. Sharp, and W. C. Summers, Proc. Natl. Acad. Sci. U.S.A. 78:1441-1445, 1981) to assess the extent of intra- and intertypic variation for one viral gene. The nucleotides encoding the structural gene varied 1.7% between the two HSV type 1 strains and 19% between HSV type 1 and HSV type 2, which translated to differences in the amino acid sequence of the two proteins of 1.9 and 27%, respectively. The DNA encoding the 5' regulatory sequences appeared to be more conserved than the DNA coding for the structural gene, and the DNA at the 3' end of the gene was the least homologous.

Mapping thymidine kinase-deficient mutants of vaccinia virus by marker rescue with hybrid plasmid DNAs containing portions of the HindIII-J fragment of virus DNA

Five hybrid plasmids were constructed, each containing a portion of the vaccinia virus DNA HindIII-J fragment. These plasmid DNAs were used in marker rescue experiments to map the mutations in the thymidine kinase (TK) gene of three TK- vaccinia virus mutants. The TK gene of each of the three mutants was rescued by DNA from plasmid pPJ701, which contained about one-half of the HindIII-J fragment. Two mutants, 1004B and 1017-1, but not the third, 1016-1, were rescued by DNA of two plasmids, pPJ702 and pPJ703, which contained 16 and 18%, respectively, of one end of the J fragment. Mutant 1016-1 could be rescued by plasmid pPJ705 containing a 1.69-kb fragment of the HindIII-J fragment. The J fragment DNA in plasmid pPJ705 is located adjacent to that and separated by an EcoRI site from pPJ703 in the vaccinia virus genome. These results indicate that the mutation site in the TK gene of 1016-1 differs from that in 1004B or 1017-1 and suggests that the structural gene for the vaccinia virus TK lies near one end of the HindIII-J fragment and spans the EcoRI site.

Activation of early adenovirus transcription by the herpesvirus immediate early gene: evidence for a common cellular control factor

Adenovirus mutants carrying a defective E1A gene, such as dl312, are unable to express any of the early viral genes upon infection of HeLa cells. However, efficient expression of the other early adenovirus genes was obtained when dl312-infected HeLa cells were coinfected with pseudorabies virus, a herpesvirus. By employing a temperature-sensitive pseudorabies mutant (tsG1) it was demonstrated that the herpesvirus function responsible for the induction of adenovirus transcription was the immediate early gene, a gene required for the activation of herpesvirus early gene expression and the maintenance of early and late herpesvirus transcription. Specifically, HeLa cells coinfected with dl312 and tsG1, when shifted to the nonpermissive temperature, lost their capacity to express the early adenovirus genes. Furthermore, activation of early adenovirus gene expression in herpesvirus coinfection occurred earlier and at a higher level than in wild-type adenovirus infection. Therefore, the herpesvirus immediate early protein not only activates the early adenovirus transcription units but apparently does so more efficiently than the adenovirus E1A gene product. Because of this fact, we argue that the activation, either by the E1A protein or the herpesvirus immediately early protein, most likely occurs indirectly through interaction with a cellular protein rather than by a direct recognition of regulatory sequences at the adenovirus promoters.

Mapping functional domains in the promoter region of the herpes thymidine kinase gene

The cloned herpes simplex virus type 1 (HSV-1) thymidine kinase (TK; ATP:thymidine 5'-phosphotransferase, EC 2.7.1.21) gene can be used to transform TK- cells to a TK+ phenotype. Transformants generated in this way express TK at a basal constitutive level that is inducible to a higher level by infection with TK- herpes virus. We have studied the effect of mutations generated in vitro on both the constitutive and virus-induced expression of TK in transformants. Four Xho I linker insertions and two deletions in the 5' untranscribed region of the cloned HSV-1 TK gene were generated in vitro. A deletion that removed all but nine base pairs of the 5' untranscribed region virtually eliminated constitutive expression and completely prevented induction by herpes virus infection. Two of the insertions have particularly interesting properties. One, nine base pairs upstream from the cap site, inactivates constitutive expression without stopping induction. The other, 50 base pairs upstream from the cap site has the opposite effect (i.e., normal constitutive expression but no induction). Analysis of these results leads us to propose that the 5' untranscribed region of the HSV-1 TK gene is quite complex with several functional domains having differential roles in the constitutive and herpes-induced expression of the TK gene.

Identification and mapping of two polypeptides encoded within the herpes simplex virus type 1 thymidine kinase gene sequences

mRNA's homologous to the herpes simplex virus type 1 DNA restriction endonuclease fragment BamHI p, which contains the thymidine kinase gene, have been identified and mapped by hybrid-arrested translation and mRNA selection. Such mRNA's, when translated in vitro, directed the synthesis of polypeptides of apparent molecular weights 43,000 (VI43) and 39,000 (VI39). mRNA for enzymatically active thymidine kinase was enriched by more than 20-fold after selection. Mapping was carried out with restriction endonuclease fragments of BamHI p, and locations of the 5' and 3' termini of VI43 mRNA were deduced. Analysis of nucleotide sequences around the 5' terminus revealed several consensus sequences commonly found at the start of eucaryotic mRNA's and which are presumably involved in initiation of transcription by RNA polymerase II. Translation of mRNA's for VI43, VI39, and the thymidine kinase enzyme was arrested only by a 1,170-base-pair region of BamHI p. Since this region is insufficient for adjacent genes, coding sequences for VI43 and VI39 must overlap; the possible relationship of these two polypeptides is discussed. A virus-induced product equivalent to VI39 was detected in infected cells.

Factors governing expression of the herpes simplex virus gene for thymidine kinase in clonal derivatives of transformed mouse L cells

The cells used in this study are sublines of a transformed mouse L cell line (designated H2) that carries the herpes simplex virus (HSV) gene for thymidine kinase (tk) as well as other viral genetic information acquired after exposure of the parental Ltk(-) cells to UV-irradiated HSV type 1. These sublines of the H2 cell line were isolated by cloning under nonselective conditions and were shown to express widely different levels of viral tk. Selective media were used to isolate phenotypically tk(-) and tk(+) variants in sequence from one of the clonal derivatives. As previously reported, superinfection of the tk(+) cell lines with tk(-) HSV type 1 resulted in enhancement of tk activity. A new finding was that viral tk activity could be induced by superinfection in at least 30% of cells from the phenotypically tk(-) sublines, indicating that a functional viral tk gene was retained in a significant proportion of the cells. Experiments were designed to test for the presence of regulatory factors that could influence tk expression in the nonsuperinfected sublines of H2. Absence of freely diffusible regulatory factors was indicated by the finding that the fusion of phenotypically tk(-) and tk(+) cells and untransformed cells in appropriate combinations did not affect the levels of tk detected. Moreover, there was no evidence for the presence in phenotypically tk(+) transformed cells of HSV-specific regulatory factors that could influence expression of tk from a superinfecting viral genome. Phenotypically tk(+) sublines of H2 were found to differ from the phenotypically tk(-) sublines and from untransformed cells in that the tk(+) cells synthesized viral proteins earlier and produced greater yields of infectious HSV progeny after superinfection with wild-type tk(+) virus. We can conclude that the absence of tk expression in the tk(-) H2 sublines cannot be accounted for by rearrangements or loss of DNA sequences encoding the enzyme itself or of sequences necessary for induction of the gene by superinfecting HSV. Moreover, it appears that the expression of tk in the tk(+) H2 sublines correlates with the presence of some factor that can enhance (or the absence of some factor that can depress) HSV replication and gene expression.

Biochemical transformation of thymidine kinase (TK)-deficient mouse cells by herpes simplex virus type 1 DNA fragments purified from hybrid plasmids

The thymidine kinase (TK) gene of HSV-1 has been cloned in Escherichia coli K12 plasmids, pMH1, pMH1A, and pMH4. These plasmids contain a 1,92Obp HSV-1 TK DNA sequence, which replaces a 2,067 bp EcoR I to Pvu II sequence of plasmid pBR322 DNA. Superhelical DNAs of plasmids pMH1, pMH1A, and pMH4 as well as plasmid DNAs cleaved by EcoR I, Hinc II, Bg1 II, Sma I, and Pvu II transformed TK-deficient LM(TK-) cells to the TK+ phenotype. A 1,230bp EcoR I-Sma I fragment purified from pMH1 DNA (and from plasmid pAGO, DNA, the parent of pMH1) also transformed LM(TK-) cells. Serological and disc PAGE studies demonstrated that the TK activity expressed in biochemically transformed cells were HSV-1-specific. The experiments suggest that the HSV-1 TK coding region may be contained within a l.1kbp DNA sequence extending from about the Hinc II (or Bgl II) cleavage site to the Sma I site. 35S-methionine labeling experiments carried out on cell lines transformed by Hinc II-cleaved pMH1 DNA and by the EcoR I-Sma I fragment showed that the TKs purified from the transformed cells consisted of about 39-40,000 dalton polypeptides.

Isozyme studies on the association of the herpes simplex virus type 1 thymidine kinase gene with human chromosomes in somatic cell hybrids

To investigate chromosomal site(s) of integration of the herpes simplex virus type 1 (HSV-1) thymidine kinase (TK) gene in biochemically transformed [HeLa(BU25)/KOS 8-1] cells, these human cells which had been transformed by ultraviolet light-irradiated HSV-1 were fused with TK-negative mouse LM(TK-) cells, human-mouse somatic cell hybrid clones (LH81 clones 1-20) were isolated by HATG-ouabain selection and their chromosomes and isozymes were analyzed. Electrophoretic and serological analyses showed that all 20 clones expressed type-specific HSV-1 TK. Isozyme analyses on 29 gene-enzyme systems representing 22 human chromosomes revealed that all of the HSV-1 TK-positive clones expressed human aminoacylase-1 (ACY-1) and esterase D (ESD), which have been mapped to human chromosomes 3 and 13, respectively. Other human isozymes were detected in only one to four clones or in none of the clones. Chromosome analyses showed that: (1) the hybrid clones retained only a few human chromosomes; (2) a marker chromosome, designated M7, consisting of a chromosome 17 translocated to the short arm of chromosome 3, occurred in 36 out of the 41 metaphases examined of LH81-4 clones 1 to 4 and in 31 out of the 33 metaphases examined of LH81-12 clone 10; (3) a modified M7 chromosome, (M7/m), in which the distal 2/3 of the long arm of M7 was translocated to a small acrocentric mouse chromosome, was the only human chromosome found in metaphases of LH81-13 clone 17; and (4) an intact human chromosome 13 was not present in LH81-12 clone 10 or LH81-13 clone 17 cells. Counterselection with BrdUrd resulted in the isolation of subclones lacking HSV-1 TK, human ACY-1 and ESD, and the human marker M7 chromosomes. The experiments indicate that the HSV-1 TK gene is probably associated in HeLa (BU25)/KOS 8-1 cells with marker chromosome M7, but the possibility is not excluded that the segment of human chromosome 13 which codes for ESD is involved.

Detection of herpes simplex virus-related antigens in the nuclei and cytoplasm of biochemically transformed cells with peroxidase/anti-peroxidase immunological staining and indirect immunofluorescence

Herpes simplex virus (HSV)-related antigens have been demonstrated in the nuclei and cytoplasm of human and mouse cells biochemically transformed by ultraviolet light-irradiated HSV. This was accomplished by using peroxidase/anti-peroxidase immunological staining and indirect immunofluorescence with rabbit antisera that had high neutralizing titers against the HSV-specific thymidine kinase activity and virus infectivity. HSV-1 antisera reacted with antigens in cells biochemically transformed by type 1 HSV, but not with those of cells biochemically transformed by type 2 HSV. Similarly, HSV-2 antisera reacted with antigens in cells biochemically transformed by HSV-2, but not with those in cells biochemically transformed by HSV-1. In contrast, herpes virus-related antigens were detected in cells cytolytically infected with HSV-1 and with HSV-2 by either type 1 or type 2 HSV antisera. These observations suggest that the antigens detected in the biochemically transformed cells were a type-specific subset of the HSV-related antigens synthesized in cells undergoing productive infection by HSV-1 and HSV-2.