Conformational change in the herpes simplex single-strand binding protein induced by DNA

Protease digestion of the herpes simplex virus type 1 major single-strand DNA binding protein ICP8 showed that the cleavage patterns observed in the presence and absence of single-stranded DNA oligonucleotides are substantially different with protection of cleavage sites between amino acids 293 and 806 observed in the presence of oligonucleotide. Experiments using ICP8 modified with fluorescein-5-maleimide (FM) showed that the fluorescence signal exhibited increased susceptibility to antibody quenching and a significant decrease in polarization of the FM fluorescence was observed in the presence compared to the absence of oligonucleotide. Taken together, these results indicate that ICP8 undergoes a conformational change upon binding to single-stranded DNA.

Interactions among structural proteins of varicella zoster virus

Varicella zoster virus tegument components include the regulatory proteins IE4, IE62, IE63 and the ORFI0 protein, a protein kinase (ORF47) and an abundant protein encoded in ORF9 which is the homolog of HSV VP22. The kinase is able to phosphorylate IE62 and the ORF9 protein specifically in viral particles. We show that interactions among these proteins are, at least in part, dependent on the presence or absence of phosphate groups and we suggest models for tegument formation and for its dissolution in the infected cell.

Cis and trans elements regulating expression of the varicella zoster virus gI gene

We have identified cis- and trans-acting elements involved in the VZV IE62 protein-activated expression of the varicella zoster virus (VZV) gene which encodes the viral gI glycoprotein. The cis-acting elements include a non-canonical TATA box and a novel 19 base pair sequence located just upstream of the TATA element designated the "activating upstream sequence" or AUS. The AUS is a movable element and its presence results in IE62 activation of a chimeric promoter consisting of the VZV gC TATA box and the gI AUS. We have also determined that the VZV ORF 29 protein modulates the regulatory activity of the IE62 protein at the gI promoter. In combination with the IE62 transactivator, it yields a 10 to 15-fold increase in expression over the levels seen with the IE62 protein alone in T lymphocytes. The upmodulatory activity requires the presence of a 40 base pair sequence, designated the 29RE, which maps between positions -220 and -180 in the gI promoter. In this paper we review these and earlier findings from our laboratories concerning the regulation of the gI promoter.

Varicella-zoster virus gE escape mutant VZV-MSP exhibits an accelerated cell-to-cell spread phenotype in both infected cell cultures and SCID-hu mice

Varicella-zoster virus is considered to have one of the most stable genomes of all human herpesviruses. In 1998, we reported the unanticipated discovery of a wild-type virus that had lost an immunodominant B-cell epitope on the gE ectodomain (VZV-MSP); the gE escape mutant virus exhibited an unusual pattern of egress. Further studies have now documented a markedly enhanced cell-to-cell spread by the mutant virus in cell culture. This property was investigated by laser scanning confocal microscopy combined with a software program that allows the measurement of pixel intensity of the fluorescent signal. For this new application of imaging technology, the VZV immediate early protein 62 (IE 62) was selected as the fluoresceinated marker. By 48 h postinfection, the number of IE 62-positive pixels in the VZV-MSP-infected culture was nearly fourfold greater than the number of pixels in a culture infected with a low-passage laboratory strain. Titrations by infectious center assays supported the above image analysis data. Confirmatory studies in the SCID-hu mouse documented that VZV-MSP spread more rapidly than other VZV strains in human fetal skin implants. Generally, the cytopathology and vesicle formation produced by other strains at 21 days postinfection were demonstrable with VZV-MSP at 14 days. To assess whether additional genes were contributing to the unusual VZV-MSP phenotype, approximately 20 kb of the VZV-MSP genome was sequenced, including ORFs 31 (gB), 37 (gH), 47, 60 (gL), 61, 62 (IE 62), 66, 67 (gI), and 68 (gE). Except for a few polymorphisms, as well as the previously discovered mutation within gE, the nucleotide sequences within most open reading frames were identical to the prototype VZV-Dumas strain. In short, VZV-MSP represents a novel variant virus with a distinguishable phenotype demonstrable in both infected cell cultures and SCID-hu mice.

Physical interaction between two varicella zoster virus gene regulatory proteins, IE4 and IE62

Transfection assays demonstrate that the varicella zoster virus (VZV) immediate-early 62 (IE62) protein is a major transactivator of VZV gene expression, whereas a second immediate-early protein, IE4, can act as a major coactivator of transactivation mediated through IE62. To test whether IE62 and IE4 interact physically, we performed several protein-protein interaction assays. Coimmunoprecipitation analyses using VZV-infected cell lysates as well as purified protein mixtures demonstrate that IE62 and IE4 form stable complexes in solution under stringent salt conditions. Enzyme-linked immunosorbent assay protein-protein interaction assays and maltose-binding protein capture assays demonstrate that IE62 binds IE4 in a concentration- and dose-dependent manner. Far Western blot analyses show that IE4 binds to an undermodified form of IE62, and the use of calf intestinal phosphatase and protein kinases suggests that the interaction with IE4 is dependent on the phosphorylation state of IE62. An IE4 binding domain on IE62 has been mapped using a set of truncated IE62 fusion peptides. Collectively, these results imply a direct and specific physical interaction between IE4 and less-phosphorylated forms of IE62. These data have implications for virion assembly, as well as for the regulation of gene expression in VZV-infected cells.

Identification of a region of the herpes simplex virus single-stranded DNA-binding protein involved in cooperative binding

We have identified a region of the herpes simplex virus major DNA-binding protein (ICP8) which is involved in cooperative binding to single-stranded DNA. This has been accomplished by analysis of ICP8 which was covalently modified by reaction with the extrinsic fluorophore fluorescein-5-maleimide (FM). Reaction conditions which result in the incorporation of 1 mol of FM per mol of ICP8 have been established. The binding properties of the modified protein were analyzed by polyacrylamide gel shift analysis with model oligonucleotides. This analysis indicates that while intrinsic binding is similar to that observed with unmodified protein, the cooperative binding of the modified protein to single-stranded DNA is significantly altered. Helix-destabilizing assays, whose results are a reflection of cooperative binding, also indicate that this property of ICP8 is decreased upon modification with FM. Mapping of the site of modification by cyanogen bromide cleavage and peptide sequencing has shown that the major site of modification is cysteine 254. This position in the primary structure of ICP8 is distinct from the regions previously shown to be involved in the interaction of this protein with single-stranded DNA.

Phosphorylation and nuclear localization of the varicella-zoster virus gene 63 protein

The protein encoded by varicella-zoster virus open reading frame 63 and carboxy-terminal deletions of the same were expressed either as fusion proteins at the carboxy terminus of the maltose-binding protein in Escherichia coli or independently in transfected mammalian cells. The truncations contained amino acids 1 to 142 (63 delta N) or 1 to 210 (63 delta K) of the complete 278-amino-acid primary sequence. Recombinant casein kinase II phosphorylated the 63F and 63 delta KF fusion proteins in vitro but did not phosphorylate the 63 delta NF fusion protein, implying that phosphorylation occurred between amino acids 142 and 210. Immunoprecipitation of 35S- or 32P-labelled extracts of cells transfected with plasmids expressing 63, 63 delta N, or 63 delta K also indicated that in situ phosphorylation most likely occurred between amino acids 142 and 210. These combined results suggest that casein kinase II plays a significant role in the phosphorylation of the varicella-zoster virus 63 protein. Indirect immunofluorescence of transfected cells indicated nuclear localization of the 63 protein and cytoplasmic localization of 63 delta K and 63 delta N, implying a requirement for sequences between amino acids 210 and 278 for efficient nuclear localization.

Retention of the herpes simplex virus type 1 (HSV-1) UL37 protein on single-stranded DNA columns requires the HSV-1 ICP8 protein

The UL37 and ICP8 proteins present in herpes simplex virus type 1 (HSV-1)-infected-cell extracts produced at 24 h postinfection coeluted from single-stranded-DNA-cellulose columns. Experiments carried out with the UL37 protein expressed by a vaccinia virus recombinant (V37) revealed that the UL37 protein did not exhibit DNA-binding activity in the absence of other HSV proteins. Analysis of extracts derived from cells coinfected with V37 and an ICP8-expressing vaccinia virus recombinant (V8) and analysis of extracts prepared from cells infected with the HSV-1 ICP8 deletion mutants d21 and n10 revealed that the retention of the UL37 protein on single-stranded DNA columns required a DNA-binding-competent ICP8 protein.

Immunization with the immediate-early tegument protein (open reading frame 62) of varicella-zoster virus protects guinea pigs against virus challenge

The IE62 protein, the primary regulatory protein of varicella-zoster virus (VZV) and the major component of the virion tegument, was an effective immunogen in the guinea pig model of VZV infection, whereas the ORF 29 gene product, a nonstructural DNA replication protein, did not elicit protection. All animals immunized with the ORF 29 protein had cell-associated viremia compared with 2 of 11 guinea pigs given the IE62 protein (P = 0.005). VZV was detected in ganglia from 38% of the animals given the ORF 29 protein and 44% of the control animals compared with 9% of the animals immunized with the IE62 protein (P = 0.04). In contrast to the IE62 protein, immunization with the ORF 29 protein did not prime the animals for an enhanced T-cell response upon challenge with infectious virus. The VZV IE62 protein has potential value as a vaccine component.

A major transactivator of varicella-zoster virus, the immediate-early protein IE62, contains a potent N-terminal activation domain

Accumulating evidence indicates that the product of the putative immediate-early gene ORF62 (IE62) activates varicella-zoster virus (VZV) genes thought to represent all three kinetic classes, namely, immediate-early (alpha), early (beta), and late (gamma) classes, of VZV genes as well as a variety heterologous gene promoters. However, the mechanism(s) by which IE62 protein mediates transactivation of these diverse VZV and heterologous gene promoters remains to be elucidated. In this study, by using yeast GAL4 protein chimeras, the coding regions of VZV ORF62 possessing activation domains have been assessed. We demonstrate that the VZV IE62 protein contains a potent activation domain in the N-terminal portion of the molecule, encoded within the first 86 codons of ORF62. The predicted secondary structure profile and the acid-base composition of this IE62 domain resemble those of other transregulatory proteins whose activation is mediated through acidic, hydrophobic elements. In addition, we show that deletion of this activation domain from the 1,310-residue native IE62 protein results in ablation of the transactivator function of IE62. We also present evidence that the mutant IE62 protein lacking the activation domain, though devoid of transactivation ability, was still capable of interfering with the activation of target promoters by the native, full-length IE62.

The varicella-zoster virus immediate early protein, IE62, can positively regulate its cognate promoter

Varicella-Zoster virus (VZV) is a neurotropic alphaherpes virus closely related to herpes simplex virus (HSV). However, unlike its close relative HSV, VZV lacks a functional alpha-TIF (alpha-gene transinducing factor) that activates the transcription of immediate early genes during the initial events of the virus life cycle. Hence, in the absence of a functional alpha-TIF, the mechanism triggering the expression of immediate early genes in VZV at present remains unclear. Accumulating evidence indicates that the gene product of the putative immediate early gene ORF62 (IE62) plays a pivotal role in activating VZV genes of all three putative kinetic classes, namely immediate early (alpha), early (beta), and late (gamma) classes of VZV genes. In the present study, we show that IE62 can positively autoregulate its cognate promoter using a transient transfection assay, both in lymphocytes and in neural cells. In the same system, we can also demonstrate activation of the VZV IE62 promoter by HSV ICP4. By deletion analysis and oligonucleotide-directed site-specific mutagenesis we have localized specific regions in the IE62 promoter/upstream sequences that mediate inducibility by IE62 and HSV ICP4, and provide evidence that this promoter activation by these two proteins may be through different mechanisms. These data, taken together with the recent demonstration of the presence of IE62 in the VZ virion tegument (Kinchington, P.R., Hoagland, J.K., Arvin, A.M., Ruyechan, W.T., and Hay, J. 1992. J. Virol. 66, 359-366) provides a possible mechanism by which the triggering of VZV gene expression occurs in the absence of a functional alpha-TIF protein.

Surface lysine and tyrosine residues are required for interaction of the major herpes simplex virus type 1 DNA-binding protein with single-stranded DNA

Modification of the herpes simplex virus type 1 major DNA-binding protein (ICP8) with reagents and conditions specific for arginine, lysine, and tyrosine residues indicates that surface lysine and tyrosine residues are required for the interaction of this protein with single-stranded DNA. Modification of either of these two amino acids resulted in a loss and/or modification of binding activity as judged by nitrocellulose filter assays and gel shift. Modification specific for arginine residues did not affect binding within the limits of the assays used. Finally, quenching of the intrinsic tryptophan fluorescence of ICP8 in the presence of single-stranded DNA either suggests involvement of this amino acid in the binding reaction or reflects a conformational change in the protein upon binding.

Regulation of varicella-zoster virus gene expression in human T lymphocytes

Varicella-zoster virus (VZV), a neurotropic alphaherpesvirus, is the etiologic agent of chicken pox and shingles (zoster) in humans. Using an in vitro transient expression assay, we have evaluated the ability of the putative immediate early VZV genes, ORF4, ORF61, and ORF62 (the analogs of the herpes simplex virus alpha 27, alpha 0, and alpha 4 genes, respectively), to modulate the expression of VZV genes of different putative kinetic classes in a human T lymphocyte cell line. These cells are of the type in which VZV can be readily detected in the viremic phase of human infection. We present evidence to indicate that, in this system, the gene product of ORF62 (IE62) is a major regulatory protein in VZV and is capable of activating VZV genes of all putative kinetic classes. In addition, we demonstrate that the gene product of ORF4 and, unlike the apparent situation in Vero cells, the gene product of ORF61 may play an accessory regulatory role in synergizing the activation of VZV genes induced by the gene product of ORF62 in human T lymphocytes.

Transcription from varicella-zoster virus gene 67 (glycoprotein IV)

Three transcripts map to the varicella-zoster virus (VZV) open reading frame (ORF) 67, which encodes glycoprotein IV (gpIV). All of these transcripts are polyadenylated and are transcribed from left to right towards the genomic terminal short repeats. Previous Northern (RNA) blot analyses suggested that the most abundant of these transcripts (1.65 kb) might code for gpIV. We performed S1 nuclease protection and primer extension assays and determined that the 5' terminus of the 1.65-kb transcript maps 91 bp upstream from the gpIV initiation codon. An AT-rich region (ATAAA), -28 bp from the cap site, is a potential TATA box, and at -71 bp there is a consensus CCAAT box motif. The 3' end of the 1.65-kb transcript is 20 bp downstream of two overlapping polyadenylation signals, AATAAA and ATTAAA, and just downstream of the 3' terminus is a GU-rich sequence. These results are reminiscent of data from our analysis of the VZV gpV gene, confirming that VZV appears able to use unusual TATA box motifs. Many canonical TATA sequences are present upstream from these VZV transcriptional start sites but, apparently, are not used. We tested sequences upstream from the gpIV cap site for promoter activity in transient expression experiments by cloning a DNA fragment (+63 to -343 bp) into pCAT3M, which contains a chloramphenicol acetyltransferase reporter gene. This clone showed little constitutive promoter activity but was activated more than 200-fold by infection with VZV and 5-fold with herpes simplex virus. The two known VZV transactivating genes (those for ORF 4 and ORF 62) were tested for their abilities to activate expression from the gpIV promoter by using their cognate promoters. The ORF 4 gene was minimally active, whereas the ORF 62 gene gave twofold induction; both genes, acting together, gave fivefold induction. However, replacement of the IE62 promoter with the immediate-early cytomegalovirus promoter in the ORF 62 construct gave over 40-fold induction of chloramphenicol acetyltransferase activity under the gpIV promoter in the same assay.

Kinetics and viral protein specificity of the cytotoxic T lymphocyte response in healthy adults immunized with live attenuated varicella vaccine

The cytotoxic T lymphocyte (CTL) response was evaluated in adults given live attenuated varicella vaccine, using target cells expressing varicella-zoster virus (VZV) immediate-early protein (IE62) or VZV glycoproteins gpI, gpIV, or gpV to determine viral protein specificity. The frequency of CTL that recognized IE62 was 1:171,000 +/- 46,000 SE in subjects tested 10 days to 8 weeks after the initial vaccine dose; the induction of CTL specific for gpI was equivalent. CTL recognition of VZV proteins was mediated by CD4+ or CD8+ cells. CTL recognition of IE62 and gpIV persisted in vaccinees (tested approximately 4 years later) and was comparable to that in the naturally immune. The mean frequency of CTL specific for gpV was lower (but not significantly) in vaccinees than in naturally immune subjects. Assay of responder cell frequencies showed persistence of equivalent numbers of T lymphocytes that recognized IE62 and gpI in vaccinees and naturally immune subjects. Immunization with this vaccine elicited memory T lymphocyte responses to VZV comparable to those induced by natural infection.

Immunity in strain 2 guinea-pigs inoculated with vaccinia virus recombinants expressing varicella-zoster virus glycoproteins I, IV, V or the protein product of the immediate early gene 62

The immunogenicity of specific varicella-zoster virus (VZV) proteins, with emphasis upon cell-mediated immune responses, was evaluated by immunizing strain 2 guinea-pigs with vaccinia virus recombinants that express gpI (vac-gpI), gpIV (vac-gpIV) and gpV (vac-gpV) or the IE-62 protein (vac-IE-62). Vac-gpI elicited the highest initial mean T cell proliferation response [stimulation index (S.I.) 3.8 +/- 0.9 S.E.M.] whereas inoculation with vac-gpV produced the lowest primary T cell response (S.I. 2.5 +/- 1.1 S.E.M.). T cell proliferation was detected for a shorter period after immunization with vac-gpV compared to vac-gpI, vac-gpIV or vac-IE-62. A comparison of the immunogenicity of vac-gpI and vac-IE-62 with the same proteins prepared by immunoaffinity purification showed that immunization with these proteins in either form elicited virus-specific IgG antibodies and T cell recognition. The presence or absence of IgG antibodies to the IE-62 protein was used to assess protection against challenge with guinea-pig cell-adapted infectious VZV in animals that had been inoculated with vac-gpI, vac-gpIV or vac-gpV. Immunization with vac-gpI and vac-gpIV restricted VZV replication but all animals given vac-gpV developed antibodies to IE-62 after challenge with infectious VZV. Priming of the T lymphocyte response was observed in all animals immunized with VZV-vaccinia virus recombinants after subsequent exposure to infectious VZV. These experiments with VZV vac-gpI, vac-gpIV and vac-gpV in guinea-pigs suggest variability in the capacity of herpesviral glycoproteins to elicit cell-mediated immunity in vivo. Induction of virus-specific immunity using IE-62 means that this major tegument protein of VZV could be a useful component for vaccine development.

The simian varicella virus and varicella zoster virus genomes are similar in size and structure

Simian varicella virus (SVV) DNA was purified from viral nucleocapsids and the molecular structure of the SVV genome was determined. SVV DNA was analyzed by agarose gel electrophoresis of BamHI, BglII, EcoRI, and PstI restriction endonuclease digests. SVV and varicella zoster virus (VZV) DNAs were demonstrated to have distinct restriction endonuclease profiles. Summation of the sizes of individual restriction endonuclease fragments indicate the size of SVV DNA is congruent to 121 kilobase pairs (kbp) or congruent to 76.8 megadaltons (Md). Electron microscopy, lambda exonuclease analysis, and Southern blot DNA hybridizations were utilized to determine the molecular structure of the SVV genome and to construct restriction endonuclease maps. The results indicate that SVV DNA consists of a long component (L, congruent to 100 kbp) covalently linked to a short component (S, congruent to 20 kbp) which is composed of a unique short sequence (Us, 5.3 +/- 0.7 kbp) bracketed by inverted repeat sequences (TRs and IRs, congruent to 7.2 kbp). The presence of 0.5 M PstI restriction endonuclease fragments indicates that the S component may invert relative to the L component and that the genome exists in two major isomeric forms. The findings demonstrate that the SVV and VZV genomes are similar in size and structure.

The varicella-zoster virus immediate-early protein IE62 is a major component of virus particles

Varicella-zoster virus (VZV) open reading frame (ORF) 62 potentially encodes a protein with considerable amino acid homology to the herpes simplex virus (HSV) immediate-early regulatory polypeptide ICP4 (or IE3). To identify and characterize its protein product(s) (IE62), we used a rabbit antiserum prepared against a synthetic peptide corresponding to the C-terminal 13 amino acids of the predicted protein. This antiserum reacted with phosphorylated polypeptides of 175 to 180 kDa that were made in VZV-infected cells and in cells infected with a vaccinia virus recombinant expressing IE62, but not in control-infected cells, confirming its specificity and reactivity to the IE62 protein. The antiserum recognized a 175-kDa polypeptide in purified virions that comigrated with a major structural protein. Comparison of this reactivity with that of an antipeptide antiserum directed against the VZV ORF 10 product (homologous to the HSV major structural protein VP16) indicates similar levels of ORF 62 and ORF 10 polypeptides in VZV virions. In contrast, antipeptide antiserum directed against the VZV ORF 29 product, the homolog of the HSV major DNA-binding protein, failed to recognize any protein in our virion preparations. Treatment of virions with detergents that disrupt the virion envelope did not dissociate IE62 from the nucleocapsid-tegument structure of the virion. Differential sensitivity of VZV virion IE62 to trypsin digestion in the presence or absence of Triton X-100 indicates that IE62 is protected from trypsin degradation by the virus envelope; since it is not a nucleocapsid protein, we conclude that it is part of the tegument. Finally, we show that the virion 175-kDa protein either can autophosphorylate or is a major substrate in vitro for virion-associated protein kinase activity.

A detailed analysis of transcripts mapping to varicella zoster virus gene 14 (glycoprotein V)

We have characterized in detail those transcripts mapping to the varicella zoster virus (VZV) glycoprotein V (gpV) open reading frame (ORF). The analyses revealed that a major 1.95-kb and a minor 2.5-kb transcript map to these sequences for VZV strain Scott, with 1.8- and 2.3-kb transcripts in a vaccine Oka strain, consistent with intragenic repeat (R2) copy number differences. The transcripts for each strain are 5' coterminal, are polyadenylated, and do not seem to be spliced. Upstream of the cap site there are few obvious regulatory consensus sequences, but there is a potential CCAAT box at -59 bp and an unusual sequence at -25 to -33, ATTTAAATT, which may serve as the TATA box for this gene. The 3' termini map 10 to 20 bases downstream from potential polyadenylation signals: ATAAA for the 1.95-kb transcript and ACGTAAA for the 2.5-kb transcript. This transcript pattern is quite different from that observed for the gpV homologue in herpes simplex virus (HSV-1), glycoprotein C (gC). Strain Scott synthesizes about 20-fold more gpV-specific transcripts than a strain of the Oka vaccine virus, reflecting the amounts of gpV polypeptide accumulating in both strains; this implies that the defect in Oka gpV polypeptide production is at the level of transcription.

The mitochondrial ATP synthase of Trypanosoma brucei: developmental regulation through the life cycle

The mitochondrial H(+)-ATPase of the parasitic protozoan Trypanosoma brucei is shown to be developmentally regulated through the T. brucei life cycle as has been shown for components of the mitochondrial electron transport chain. We have substantiated our results by assaying not only for oligomycin-sensitive ATPase activity but also by determining the level of ATP synthetic activity. These results show that the level of ATPase present in the procyclic form of T. brucei is increased by at least threefold from that of the early bloodstream form while the ATPase activity in the late bloodstream form is only about twofold higher than the early form. ATP synthesis activity shows these same results. We have determined the level of ATP synthase protein present in the life cycle stages by Western analysis employing the antibodies that we have raised against both the water soluble F1 and the membrane-associated F0 moieties which we have purified from T. brucei. The Western blots of the procyclic form show strong reactivity with both the F0 and F1 antibodies. The other two life cycle stages, the early and the late bloodstream forms, show considerably less reactivity, paralleling the activity results. Electron micrographs of the sonicated mitochondrial fraction show inverted vesicles which are studded with knobby H(+)-ATPase in the procyclic form. The early bloodstream vesicles show very few of these characteristic structures, while the late bloodstream form shows a range of vesicles from nearly nude to partially studded.

The major herpes simplex virus type-1 DNA-binding protein is a zinc metalloprotein

The primary amino acid sequence of the major herpes simplex virus type 1 (HSV-1)-infected cell polypeptide 8 (ICP8) deduced from the DNA sequence of the unique long open reading frame 29 (UL29 ORF) contains a potential metal-binding domain of the form Cys-X2-5-Cys-X2-15-A-X2-4-A where A may be either histidine or cysteine and X is any amino acid. The putative metal-binding sequence in ICP8 encompasses residues 499-512 as follows: C-N-L-C-T-F-D-T-R-H-A-C-V-H-. Atomic absorption analysis of several preparations of ICP8 indicates the presence of 1 mol of zinc/mol of protein. The zinc is resistant to removal by dialysis against concentrations of EDTA which deplete zinc from alcohol dehydrogenase. The bound zinc can be removed by reaction with the reversible sulfhydryl reagent p-hydroxymercurimethylsulfonate and the zinc-depleted protein transiently retains DNA binding activity. Digestion of both native and zinc-depleted ICP8 with V8 protease indicates that the bound zinc is required for the structural integrity of the protein.

Evidence for DNA binding activity of numatrin (B23), a cell cycle-regulated nuclear matrix protein

Stimulation of various cell types with growth factors is associated with a rapid induction in the synthesis of a nuclear matrix protein, termed 'numatrin' which was shown to be identical to the nucleolar protein B23. The abundance of numatrin was shown to be correlated with entry and progression through the S-phase. Thus, experiments were undertaken to examine whether numatrin also has DNA binding activity. Using whole nuclear extract, we showed that numatrin binds to both double-stranded (DS) DNA and to single-stranded (SS) DNA cellulose columns. Purified numatrin, which was extracted either under native conditions (in oligomeric form) or under urea conditions (in monomeric form), demonstrated significant binding to either [3H]DS-DNA or [3H]DS-DNA as shown by nitrocellulose filter binding assay. However, numatrin binding to DS-DNA was qualitatively and quantitatively different from its binding to SS-DNA. Thus, the binding of numatrin was several fold higher to DS-DNA as compared to SS-DNA. The binding to DS-DNA was reduced by 77% in the presence of 0.5 M NaCl, while the binding to SS-DNA was not affected under this condition. Furthermore, treatment of the native numatrin under conditions which caused monomerization of the protein resulted in a significant enhancement of numatrin binding to SS-DNA but did not affect the binding to DS-DNA. Following heparin-Sepharose chromatography purification (under native conditions), numatrin at picomole amounts showed significant binding to both DS-DNA and SS-DNA. Finally, numatrin was found to copurify with the complex of DNA polymerase alpha primase together with other proteins required for SV-40 in vitro replication activity. These results demonstrate that numatrin has DNA binding activity, and imply a possible role for numatrin/B23 in DNA-associated processes.

The glycoprotein products of varicella-zoster virus gene 14 and their defective accumulation in a vaccine strain (Oka)

Many characteristics of the putative protein encoded by varicella-zoster virus (VZV) open reading fram (ORF) 14 indicate that it is a glycoprotein, which has been designated gpV. To identify the protein products of the gene, the coding sequences were placed under the control of the vaccinia virus p7.5 promoter and recombinant vaccinia viruses were constructed. Heterogeneous polypeptides with molecular weights of 95,000 to 105,000 (95K to 105K polypeptides) were expressed in cells infected by a vaccinia virus recombinant (vKIP5) containing ORF 14 from VZV Scott but were not expressed by control vaccinia viruses. These polypeptides were recognized by antibodies present in human sera that contained high levels of anti-VZV antibodies. Conversely, antisera raised in rabbits inoculated with vKIP5 reacted specifically with heterogeneous 95K to 105K polypeptides present in VZV Scott-infected but not uninfected cells; these polypeptides show a patchy plasma membrane fluorescence pattern in VZV Scott-infected cells. These same antisera neutralized VZV strain Scott infectivity in the absence of complement. Endoglycosidase F treatment of isolated gpV polypeptides and tunicamycin treatment of cells infected with the vKIP5 recombinant indicated that the polypeptides were glycosylated. Three sets of data imply that the VZV strain Oka, which has been used to produce a live attenuated virus vaccine, accumulates low levels of gpV polypeptides relative to wild-type strains: (i) blocking of antibodies in human sera with excess VZV Oka-infected cell antigen yielded residual antibodies which were reactive with the 95K to 105K gpV polypeptides expressed in cells infected by VZV strain Scott and by the vKIP5 vaccinia virus recombinant, but not with Oka-infected cell polypeptides; (ii) antisera raised to vKIP5 detected very low levels of reactive polypeptides made in VZV Oka-infected cells and neutralized VZV Oka virus much less efficiently than VZV Scott; and (iii) comparisons of the reactivity of sera from live attenuated virus vaccine vaccinees with sera derived from patients recovering from wild-type infections indicated greatly reduced levels of gpV-specific antibodies in some vaccinees.

Expression of herpes simplex virus type 1 DNA polymerase in Saccharomyces cerevisiae and detection of virus-specific enzyme activity in cell-free lysates

The herpes simplex virus type 1 (HSV-1) (strain 17) DNA polymerase gene has been cloned into an Escherichia coli-yeast shuttle vector fused to the galactokinase gene (GAL-1) promoter. Genes controlled by the GAL-1 promoter are induced by galactose, uninduced by raffinose, and repressed by glucose. Cell extracts from a strain of Saccharomyces cerevisiae harboring this vector (Y-MH202, expresser cells) grown in the presence of galactose and assayed in high salt (100 mM ammonium sulfate) contained a novel DNA polymerase activity. No significant high-salt DNA polymerase activity was detected in extracts from expresser cells grown in the presence of raffinose or in extracts from control cells containing the E. coli-yeast shuttle vector without the HSV-1 DNA polymerase gene grown in the presence of raffinose of galactose. Immunoblot analysis of the cell extracts by using a polyclonal rabbit antiserum prepared against a highly purified HSV-1 DNA polymerase preparation revealed the specific induction of the HSV-1 approximately 140-kilodalton DNA polymerase polypeptide in expresser cells grown in galactose. Extracts from the same cells grown in raffinose or control cells grown in either raffinose or galactose did not contain this immunoreactive polypeptide. The high-salt DNA polymerase activity in the extracts from expresser cells grown in galactose was inhibited greater than 90% by either acyclovir triphosphate or aphidicolin, as expected for HSV-1 DNA polymerase. In addition, the high-salt polymerase enzyme activity could be depleted from extracts by immunoprecipitation by using purified immunoglobulin G from this same polyclonal rabbit antiserum. These results demonstrate the successful expression of functional HSV-1 DNA polymerase enzyme in S. cerevisiae.

Identification and characterization of a DNA primase activity present in herpes simplex virus type 1-infected HeLa cells

A novel DNA primase activity has been identified in HeLa cells infected with herpes simplex virus type 1 (HSV-1). Such an activity has not been detected in mock-infected cells. The primase activity coeluted with a portion of HSV-1 DNA polymerase from single-stranded DNA agarose columns loaded with high-salt extracts derived from infected cells. This DNA primase activity could be distinguished from host HeLa cell DNA primase by several criteria. First, the pH optimum of the HSV primase was relatively broad and peaked at 8.2 to 8.7 pH units. In contrast, the pH optimum of the HeLa DNA primase was very sharp and fell between pH 7.9 and 8.2. Second, freshly isolated HSV DNA primase was less salt sensitive than the HeLa primase and was eluted from single-stranded DNA agarose at higher salt concentrations than the host primase. Third, antibodies raised against individual peptides of the calf thymus DNA polymerase:primase complex cross-reacted with the HeLa primase but did not react with the HSV DNA primase. Fourth, freshly prepared HSV DNA primase appeared to be associated with the HSV polymerase, but after storage at 4 degrees C for several weeks, the DNA primase separated from the viral DNA polymerase. Separation or decoupling could also be achieved by gel filtration of the HSV polymerase:primase. This free DNA primase had an apparent molecular size of approximately 40 kilodaltons, whereas free HeLa DNA primase had an apparent molecular size of approximately 110 kilodaltons. On the basis of these data, we believe that the novel DNA primase activity in HSV-infected cells may be virus coded and that this enzyme represents a new and important function involved in the replication of HSV DNA.

Identification and characterization of a varicella-zoster virus DNA-binding protein by using antisera directed against a predicted synthetic oligopeptide

We have identified, in varicella-zoster virus (VZV)-infected cells, the product of the gene predicted to code for the VZV analog of the herpes simplex virus major DNA-binding protein. The open reading frame of the VZV gene has the potential to code for a protein with a predicted molecular weight of 132,000 (a 132K protein). To detect the protein, a 12-amino-acid oligopeptide corresponding to the carboxyl terminus of the putative open reading frame was synthesized and used to prepare antisera in rabbits. The resulting antibodies reacted specifically in Western immunoblot analysis and immunoprecipitation with a single 130K polypeptide found in VZV-infected cells. The specific reactivity of the antisera with the 130K polypeptide was inhibited by the addition of synthetic peptide. Immunofluorescence studies with the antisera as probe for the 130K polypeptide suggested that this peptide is located predominantly within the nuclei of infected cells. Analysis of proteins that bind to single-stranded DNA immobilized on cellulose matrices indicated that 30 to 50% of the 130K polypeptide is capable of interacting with single-stranded DNA and that this interaction is overcome with 0.5 M NaCl. Thus, we have prepared a specific polyclonal antiserum that identifies a VZV DNA-binding protein whose properties are similar to those of the herpes simplex virus ICP8 (Vmw130) DNA-binding protein.

N-ethylmaleimide inhibition of the DNA-binding activity of the herpes simplex virus type 1 major DNA-binding protein

The major herpes simplex virus DNA-binding protein, designated ICP8, binds tightly to single-stranded DNA and is required for replication of viral DNA. The sensitivity of the DNA-binding activity of ICP8 to the action of the sulfhydryl reagent N-ethylmaleimide has been examined by using nitrocellulose filter-binding and agarose gel electrophoresis assays. Incubation of ICP8 with N-ethylmaleimide results in a rapid loss of DNA-binding activity. Preincubation of ICP8 with single-stranded DNA markedly inhibits this loss of binding activity. These results imply that a free sulfhydryl group is involved in the interaction of ICP8 with single-stranded DNA and that this sulfhydryl group becomes less accessible to the environment upon binding. Agarose gel electrophoretic analysis of the binding interaction in the presence and absence of N-ethylmaleimide indicates that the cooperative binding exhibited by ICP8 is lost upon treatment with this reagent but that some residual noncooperative binding may remain. This last result was confirmed by equilibrium dialysis experiments with the 32P-labeled oligonucleotide dT10 and native and N-ethylmaleimide-treated ICP8.

Physical characterization of the genome of feline herpesvirus-1

The physical structure of the genome of feline herpesvirus-1, a major upper respiratory tract pathogen of cats, was studied. Purified FHV-1 DNA was analyzed by restriction endonuclease and gamma 5' exonuclease digestion, blot hybridization, and electron microscopy. To facilitate further studies, nine bacteriophage clones were isolated which contained 85% of the viral genome as SalI inserts, and DNA from these clones was used in blot hybridization experiments and as substrates for restriction digest analysis. Data from these studies permitted construction of a SalI and partial HindII and EcoRI restriction maps of the viral genome. FHV-1 DNA is approximately 134 kb in size and is composed of a long (L) and a short (S) segment. The long segment (U1) is 104 kb in size and is composed of unique DNA. The adjacent S segment is approximately 30 kb in size and contains a central portion of unique DNA (Us) which is approximately 8 kb in size. The Us region is bounded by inverted repeat sequences which are 11 kb in size. Therefore, the physical structure of the FHV-1 genome is similar to the genomes of other alpha-herpesviruses.

Putative glycoprotein gene of varicella-zoster virus with variable copy numbers of a 42-base-pair repeat sequence has homology to herpes simplex virus glycoprotein C

A strain variation of varicella-zoster virus that maps to the UL region of the genome was found to be due to different copy numbers of a high GC 42-base-pair repeat. DNA sequence analysis of this variable region showed the sequence to be 5-GCGGGATCGGGCTTTCGGG(A/T)AGCGGCCGAGGTGGGCGCGACG-3. Strains Scott and Webster both contain 7 and 32/42 copies of the repeat, whereas strain Oka has exactly 4 copies less. Microheterogeneity exists within the repeated sequences, depending on the strain and the repeat number. Sequencing of the entire EcoRI P fragment (which contains the repeated sequences) and part of the adjacent EcoRI M and EcoRI Q fragments from strain Scott showed that the repeats are part of a large open reading frame that could code for a polypeptide core with a molecular weight of 66,000. Several potential TATA boxes exist upstream and two polyadenylation signals are found downstream of the open reading frame. The predicted protein bears several characteristics of a glycoprotein. The region is transcriptionally active in varicella-zoster virus-infected cells, specifying at least three RNA species of 1.7, 1.95, and 2.5 kilobases, which are transcribed from the same DNA strand. Part of the predicted protein has a high degree of homology to the herpes simplex virus type 1 glycoprotein gC.

In vitro characterization of a thermolabile herpes simplex virus DNA-binding protein

The major herpes simplex virus DNA-binding protein, ICP8, was purified from cells infected with the herpes simplex virus type 1 temperature-sensitive strain tsHA1. tsHA1 ICP8 bound single-stranded DNA in filter binding assays carried out at room temperature and exhibited nonrandom binding to single-stranded bacteriophage fd DNA circles as determined by electron microscopy. The filter binding assay results and the apparent nucleotide spacing of the DNA complexed with protein were identical, within experimental error, to those observed with wild-type ICP8. Thermal inactivation assays, however, showed that the DNA-binding activity of tsHA1 ICP8 was 50% inactivated at approximately 39 degrees C as compared with 45 degrees C for the wild-type protein. Both wild-type and tsHA1 ICP8 were capable of stimulating viral DNA polymerase activity at permissive temperatures. The stimulatory effect of both proteins was lost at 39 degrees C.

Distribution of G + C-rich regions in varicella-zoster virus DNA

The distribution of G + C-rich sequences in the genome of varicella-zoster virus (VZV) was investigated by partial denaturation, equilibrium sedimentation and Southern blot analyses. Portions of the IRS and TRS repeat sequences bounding the US region of the DNA were found to have a G + C content 10 to 20% greater than the overall 47% G + C content of the VZV genome. A stretch of DNA (approx. 1500 base pairs) at the UL-IRS junction and repeated at the terminus of the TRS sequences was found to be about 64% G + C, based on sedimentation equilibrium measurements. We also report the cloning of a novel fragment containing sequences from both the UL and TRS termini of the VZV genome. Our ability to clone this fragment suggests that unusual forms of VZV DNA including closed circular molecules and molecules with an inverted UL region can be packaged into nucleocapsids.

Interaction with nucleic acids and stimulation of the viral DNA polymerase by the herpes simplex virus type 1 major DNA-binding protein

The interaction of the herpes simplex virus type 1 (HSV-1) major DNA-binding protein, infected-cell polypeptide 8 (ICP8), with nucleic acids has been examined by a filter-binding assay and electron microscopy. Filter-binding assays done over a broad pH range indicated that the optimum pH for the protein-DNA interaction is approximately 7.6. Heat inactivation studies showed that ICP8 is stable at temperatures up to 40 degrees C with a rapid loss of binding activity on incubation at 45 degrees C and above. Competition binding experiments have established the following relative affinities of ICP8 for the following nucleic acids: single-stranded HSV-1 DNA congruent to bacteriophage fd DNA greater than polyriboadenylate much greater than double-stranded HSV-1 DNA congruent to d(pCpT)5. Observation of negatively stained ICP8-single-stranded DNA complexes indicated that ICP8 binds along the length of the DNA in a regular repeating fashion. The average width of these complexes is 9.3 +/- 0.8 nms. Finally. Finally, addition of purified ICP8 to HSV-1 DNA polymerase reactions resulted in a stimulation of the viral polymerase activity.

Evidence that a new enterotoxin of Escherichia coli which activates adenylate cyclase in eucaryotic target cells is not plasmid mediated

Escherichia coli SA53 produces a new enterotoxin that has a biological activity similar to that of E. coli heat-labile enterotoxin (LT) but is not neutralized by antiserum against LT or cholera enterotoxin. Strain SA53 contained two plasmids, pRB1 (69.2 +/- 4.3 megadaltons) and pRB2 (57.6 +/- 5.3 megadaltons). Studies were undertaken to determine whether either plasmid was required for production of the LT-like toxin. We isolated a derivative of SA53 lacking both plasmids and confirmed that radioactively labeled pRB1 and pRB2 DNAs failed to hybridize to total DNA digests of the cured strain. The new enterotoxin was still produced by the cured strain, demonstrating that the gene(s) encoding the toxin was not located on pRB1 or pRB2 and was most likely on the bacterial chromosome. Although sonic extracts from SA53 contained no detectable LT antigen, plasmid pRB1 DNA did contain sequences with partial homology to the LT-A and LT-B genes. No sequence homology with LT genes was detected with pRB2 DNA. When the enterotoxin plasmid pCG86 was introduced into a rifampin-resistant derivative of SA53, LT was produced. Thus, plasmid-coded LT could be produced in the E. coli SA53 host, and the sequences homologous to LT in pRB1 were cryptic.

The major herpes simplex virus DNA-binding protein holds single-stranded DNA in an extended configuration

Properties of the major DNA-binding protein found in herpes simplex virus-infected cells were investigated by using a filter binding assay and electron microscopy. Filter binding indicated that the stoichiometry of binding of the protein with single-stranded DNA is approximately 40 nucleotides per protein molecule at saturation. Strong clustering of the protein in DNA-protein complexes, indicative of cooperative binding, was seen with the electron microscope. Measurements of single-stranded fd DNA molecules saturated with protein and spread for electron microscopy by using both the aqueous and formamide spreading techniques indicated that the DNA is held in an extended configuration with a base spacing of approximately 0.13 nm per base.

Purification and characterization of yeast topoisomerase I

Yeast topoisomerase I (Mr = 76,000) has been purified to 80% homogeneity using a combination of ion exchange, gel filtration, and DNA-cellulose chromatography. The enzyme was characterized with respect to its ability to relax supercoiled DNA and to catenate nicked circular DNA. Yeast topoisomerase I will remove both positive and negative turns in DNA supercoils in the absence of ATP and magnesium ion. The products of the catenating activity of the enzyme were examined on agarose gels and in the electron microscope. These analyses indicate that yeast topoisomerase I will generate large catenated DNA networks which appear to rearrange to multimeric linear structures upon long incubation time.

Electron microscopic study of equine herpesvirus type 1 DNA

Electron microscopic studies of equine herpesvirus DNA revealed that single strands that were allowed to reanneal formed single-stranded loops with double-stranded stems only at one end of the molecule. These observations support restriction enzyme analyses which indicate that the 92-megadalton DNA molecule exists as a long region of unique sequences covalently linked to a short region. The short region is comprised of an internal unique sequence, which forms the loop during reannealing of single strands, and two terminal inverted repeat sequences that bracket the unique sequence and form the double-stranded stem structure observed upon reannealing of single strands. Measurements of the unique sequence and terminal inverted repeat subgenomic sequences indicate a size of 6.4 megadaltons for each and thus fix the size of the short region at approximately 19.2 megadaltons.

Molecular cloning and physical mapping of varicella-zoster virus DNA

Varicella-zoster virus (VZV) DNA was cleaved with restriction endonuclease EcoRI, and most of the resulting fragments were successfully cloned in the phage vector lambda gtWES . lambda B. Double digestions of cloned fragments with EcoRI and BamHI and hybridizations to blot-transferred BamHI digests of VZV DNA were used to construct a physical map of the genome. The molecular termini of the DNA were identified by restriction enzyme analysis after exonuclease III digestion. The data indicate that VZV DNA exists in two isomeric forms that differ by inversion of one short terminal genome segment. Electron microscopic studies revealed that the short genome segment consists of a terminal revealed that the short genome segment consists of a terminal sequence of about 3.4 X 10(6) daltons that is separated from an internal inverted repeat of itself by a 5.8 X 10(60)-dalton unique DNA segment.

Structure of varicella-zoster virus DNA

Varicella-zoster virus (VZV) DNA was prepared from nucleocapsids and from enveloped virions of a laboratory strain (Ellen) and directly from the vesicle fluids of patients with zoster infections. VZV Ellen nucleocapsid DNA was cleaved with 11 different restriction endonucleases and electrophoresed in agarose gels. The restriction profiles of the nucleocapsid DNA were identical to those of the DNA recovered from purified virions, but differed from those of another VZV strain (KM). In vitro-labeled VZV K.M. DNA purified directly from vesicle fluid yielded a distinct restriction pattern which appeared to be unchanged after several tissue culture passages of the isolate from that fluid. Restriction endonuclease analysis (EcoRI or BglII) of VZV DNA revealed the presence of four cleavage fragments with a molar ratio of approximately 0.5. No individual fragments with molar ratios of 0.25 were noted. This observation suggests that the VZV genome may contain one invertible segment. Comparison of the electrophoretic migrations of VZV DNA fragments relative to those of DNAs of known size permitted calculation of the VZV genome size to be 72 X 10(6) to 80 X 10(6) daltons. These results were confirmed by electron microscopy which demonstrated a genome size of about 76 X 10(6) daltons for passaged and unpassaged VZV DNA. Electron microscopy also revealed that some of the DNA molecules recovered from nucleocapsids or directly from vesicle fluids were superhelical circles.

Denaturation and renaturation of Penicillium chrysogenum mycophage double-stranded ribonucleic acid in tetraalkylammonium salt solutions

The base composition dependence of double-stranded ribonucleic acid (RNA) melting was studied by observing the structure and widths of melting transitions for Penicillium chrysogenum mycophage RNA as well as differences in melting temperatures of two RNAs of different base composition. Double-stranded RNA melting is independent of base compositions in 3.5 M Et4NCl and 4.6 M Me4NCl, where the melting temperatures are 25 and 92 degrees C, respectively. Double-stranded RNA renaturation rate constants are reported in Et4NCl solutions. The nucleation rate constant is about 10 times lower than that for double-stranded deoxyribonucleic acid. Analyses of renaturation kinetics results lead to the conclusion that each of the three similar but separable RNA segments of Penicillium chrysogenum mycophage is unique.

Molecular genetics of herpes simplex virus: the terminal a sequences of the L and S components are obligatorily identical and constitute a part of a structural gene mapping predominantly in the S component

In herpes simplex virus 1 (HSV-1) DNA, a small sequence, designated the a sequence, flanks the reiterated sequences at the ends of both the L and S components. The a sequence is the only sequence shared by the termini of all isomeric arrangements of HSV-1 DNA that arise from inversions of the covalently linked L and S components. We report that the a sequence, although present in both components, is a part of a structural gene mapping predominantly in the reiterated sequences of the S component. This conclusion is based on the observations that the mutant HSV-1(13)tsC75 is rescued by transfection of cells with the mutant DNA and any one of the four terminal or four L-S junction fragments of wild-type DNA. Furthermore, in doubly infected cells, this mutant shows little or no recombination or complementation with other ts mutants previously mapped within the reiterated sequences of the S component. Because it is otherwise difficult to explain the isolation of a mutant with several independent, equivalent mutations, the data argue for a mechanism that maintains the identity of the multiple copies of the a sequence.The paradox arising from the two observations that all termini rescue the ts mutant but that in coinfection tests the ts lesion is closely linked to the reiterated sequences of the S component could be accounted for by postulating that either recombination occurs while the DNA is in a circular form-in which case all a sequences would be adjacent to the reiterated sequence of the S component-or recombination can occur while the DNA is in a linear form. In this case the only effective substitution of the a sequence that is perpetuated is the one occurring at the L-S junction or in the S component. In light of the observations that tsC75 and the other mutants tested in this study map in the reiterated sequences and fail to yield appreciable recombinational frequencies, it is unlikely that isomerization of the DNA occurs by intramolecular recombination between reiterated sequences.

Molecular genetics of herpes simplex virus. II. Mapping of the major viral glycoproteins and of the genetic loci specifying the social behavior of infected cells

We have mapped the location in herpes simplex virus (HSV) DNA of (i) three mutations at different loci (syn loci) which alter the social behavior of infected cells from clumping of rounded cells to polykaryocytosis, (ii) a mutation which determines the accumulation of one major glycoprotein [VP8.0(C(2))], and (iii) the sequences encoding four major virus glycoproteins [VP8.0(C(2)), VP7(B(2)), VP8.5(A), and VP19E(D(2))]. The experimental design and results were as follows. (i) Analysis of HSV-1 x HSV-2 recombinants showed that the sequences encoding the VP19E(D(2)) glycoprotein map in the S component, whereas the sequences encoding the other three major glycoproteins are in two locations in the L component of HSV DNA. The templates specifying the HSV-1 and HSV-2 glycoprotein VP8.0(C(2)) appear not to be colinear; we isolated recombinants specifying glycoproteins comigrating in sodium dodecyl sulfate-polyacrylamide gels with VP8.0(C(2)) of both HSV-1 and HSV-2. (ii) Marker rescue of a ts mutant defective in accumulation of glycoprotein VP7(B(2)) showed that the mutation maps within a region containing the sequences encoding that glycoprotein. (iii) Marker transfer experiments involving transfection of rabbit skin cells with donor HSV-1(F) DNA and fragments from several donor strains causing fusion of Vero or both Vero and HEp-2 cells revealed the existence of three syn loci specifying the social behavior of cells and one locus (Cr) determining the accumulation of glycoprotein VP8.0(C(2)). The Cr locus maps to the right of the template specifying VP8.0(C(2)) glycoprotein. Loci syn 1 and syn 2 map at or near the Cr locus but can be segregated from it. Locus syn 3 maps at or near the template specifying glycoproteins VP7(B(2)) and VP8.5(A). The expression of mutations in the syn 1 and syn 3 loci appear to be cell type dependent, in that recombinants with these mutations fuse Vero cells but not HEp-2 cells. Recipients of the syn 2 locus or of both syn 2 and syn 1 loci fuse both Vero and HEp-2 cells.

Molecular genetics of herpes simplex virus. III. Fine mapping of a genetic locus determining resistance to phosphonoacetate by two methods of marker transfer

We have transferred a genetic locus determining resistance to phosphonoacetic acid (PAAr) from one herpes simplex viral genome to another by two methods of marker transfer. One method requires recombination between an intact DNA molecule and a restriction endonuclease DNA fragment, whereas the other requires repair of a partial heteroduplex formed between the two DNA molecules. These two methods mapped the PAAr locus between positions 0.45 and 0.53 map units on the physical map of the viral DNA. Fine mapping of the PAAr locus showed that it maps at or near an EcoRI restriction endonuclease site at either 0.46 or 0.49 map units. We also describe and compare the two methods of marker transfer.

Molecular genetics of herpes simplex virus: demonstration of regions of obligatory and nonobligatory identity within diploid regions of the genome by sequence replacement and insertion

The DNAs of herpes simplex virus (HSV) 1 and 2 consist of two components, L and S, each composed of unique sequences bracketed by inverted repeats. In this study we have probed the structure of the reiterated regions of the S component in marker rescue experiments involving transfection of cells with mixtures of intact HSV-1 mutant viral DNA and individual DNA fragments generated by restriction endonuclease digestion of wild-type HSV-1 or HSV-2 DNAs. The results were as follows: (i) HSV is diploid for the wild-type sequences that rescue two temperature-sensitive (ts) mutants. DNA fragments from both reiterated regions of the S component of HSV-1(F) DNA can rescue tsLB2 and tsD mutants. (ii) Identity of the entire reiterated sequence at both ends of S is not obligatory because only one end of the S component of wild phenotype virus HSV-1(1061) rescues tsD even though both ends rescue tsLB2. (iii) Genes in both reiterated sequences can be expressed. We produced, by marker rescue experiments, recombinants with heterotypic ends of the S component, and these specified corresponding polypeptides characteristic of both HSV-1 and HSV-2. (iv) The reiterated sequences of the S component may contain a region of obligatory identity. Thus, several recombinant clones produced by rescue with HSV-2 DNA contained identical HSV-2 DNA insertions within both reiterated regions of the HSV-1 S component. Consistent with this conclusion, the termini of the S component in the heterodiploids described in iii were identical by restriction enzyme analysis. (v) The observation that HSV DNA can be expanded by at least 5 x 10(6) by means of insertion in the S component suggests that it can be a vehicle for exogenous DNA.