Immediate-early mRNA-2 of herpes simplex viruses types 1 and 2 is unspliced: conserved sequences around the 5' and 3' termini correspond to transcription regulatory signals

Targets for Antiviral Chemotherapy: Herpes Simplex Virus Regulatory Protein, Vmw65

The virion protein, Vmw65, of herpes simplex virus selectively induces the transcription of the virus immediate–early genes and is required for normal virus replication and for virulence in animal models. Vmw65 operates by interacting with a host cell transcription factor (Oct-1) and analysis of the structure/function relationship within Vmw65 has facilitated the design of a peptide, corresponding to a local domain of the protein, which interferes with the Vmw65–Oct-1 interaction. The selective interference of protein–protein interactions involved in gene regulation may provide a suitable target for the inhibition of virus replication.

The genome sequence of herpes simplex virus type 2

The genomic DNA sequence of herpes simplex virus type 2 (HSV-2) strain HG52 was determined as 154,746 bp with a G+C content of 70.4%. A total of 74 genes encoding distinct proteins was identified; three of these were each present in two copies, within major repeat elements of the genome. The HSV-2 gene set corresponds closely with that of HSV-1, and the HSV-2 sequence prompted several local revisions to the published HSV-1 sequence (D. J. McGeoch, M. A. Dalrymple, A. J. Davison, A. Dolan, M. C. Frame, D. McNab, L. J. Perry, J. E. Scott, and P. Taylor, J. Gen. Virol. 69:1531-1574, 1988). No compelling evidence for the existence of any additional protein-coding genes in HSV-2 was identified.

Herpes simplex ICP27 mutant viruses exhibit reduced expression of specific DNA replication genes

Herpes simplex virus type 1 mutants with certain lesions in the ICP27 gene show a 5- to 10-fold reduction in viral DNA synthesis. To determine how ICP27 promotes amplification of viral DNA, we examined the synthesis, accumulation, and stability of the essential viral replication proteins and steady-state levels of the replication gene transcripts throughout the course of ICP27 mutant virus infections. These studies reveal that in the absence of ICP27, expression of the UL5, UL8, UL52, UL9, UL42, and UL30 genes is significantly reduced at the level of mRNA accumulation. In contrast to that of these beta genes, ICP8 expression is unaltered in mutant virus-infected cells, indicating that ICP27 selectively stimulates only a subset of herpes simplex virus beta genes. Analysis of multiple ICP27 mutant viruses indicates a quantitative correlation between the ability of these mutants to replicate viral DNA and the level of replication proteins produced by each mutant. Therefore, we conclude that the primary defect responsible for restricted viral DNA synthesis in cells infected with ICP27 mutants is insufficient expression of most of the essential replication genes. Of further interest, this analysis also provides new information about the structure of the UL52 gene transcripts.

Inhibition of herpes simplex virus in culture by oligonucleotides composed entirely of deoxyguanosine and thymidine

Oligodeoxynucleotides (ODNs) composed entirely of deoxyguanosine and thymidine, but not specifically designed to act as antisense agents, were able to significantly inhibit herpes simplex virus growth in acute infection assay systems. The guanosine/thymidine (GT) ODNs which demonstrated this antiviral activity contained either natural phosphodiester (PO) or phosphorothioate (PS) modified internucleoside linkages. In all experiments, the antiviral activity of the ODNs was enhanced when the backbone was modified to contain the PS linkages. When present during the time of virus addition, the ODNs were able to block the adsorption of virus to Vero cells. In this assay the PS-containing ODNs had ID50 values of approximately 0.020 microM for HSV-2 and of 0.3 microM for HSV-1. When these same PS-containing ODNs were used against HSV-2 in single-cycle viral yield assays, designed to minimize the effects due to external blockage of virus, the ID50 values rose to 0.2 microM. Analysis of viral DNA obtained 14 h post-HSV-2 infections in the single-cycle assay, revealed a decrease in replicated viral DNA in cells treated with PS-ODNs. Analysis of viral mRNA obtained 4 h post-HSV-2 infection revealed, in cells treated with the PS-ODNs, a decrease in measurable HSV-2 alpha- and beta-mRNAs. Although the mechanism of action of the antiviral activity (beyond adsorption blocking) is not fully understood, the toxicity of these compounds was low, giving high therapeutic indices for the GT-rich PS-ODNs. The good therapeutic index of GT-ODNs make this a class of compounds which warrant investigation as therapeutic agents to be used against herpes viruses.

Identification of a promoter mapping within the reiterated sequences that flank the herpes simplex virus type 1 UL region

Analysis of the promoter for the herpes simplex virus (HSV) immediate-early (alpha) gene alpha 0 in a short-term transient expression assay revealed that a SacI-to-NcoI fragment from -786 to +148 relative to the cap site directed the synthesis of chloramphenicol acetyltransferase when the fragment was present in either orientation. Although the constitutive levels of promoter activity were similar with either orientation, the reverse-orientation promoter was not induced in response to infection with HSV. Analysis of sequences composing the putative promoter in the opposite orientation revealed the presence of important regulatory elements associated with alpha promoters. These include an alpha-trans-inducing factor (alpha-TIF)-like response element, a high-affinity ICP4-binding site, numerous Sp1-binding sites, and a TATA box. Sequences contained within this region formed specific DNA-protein complexes in extracts from mock-infected and HSV-infected HeLa cells. Transient expression assays revealed that this sequence was positively regulated by the alpha 0 and alpha-TIF genes but negatively regulated by alpha 4. Finally, nuclear run-on transcription assays revealed that this promoter is active in its correct genomic context during the course of virus infection. We suggest that the promoter is a hybrid between an alpha and beta promoter because it exhibits maximal expression at 8 h postinfection and is expressed in the presence of cycloheximide.

Mapping of a major surface-exposed site in herpes simplex virus protein Vmw65 to a region of direct interaction in a transcription complex assembly

The cellular factor Oct-1 is selectively recruited, together with at least one other cellular protein (CFF), into a multicomponent transcription complex whose assembly is directed by the herpes simplex virus regulatory protein Vmw65 (VP16). The acidic carboxy terminus of Vmw65 is not involved in assembly of the complex but is absolutely required for subsequent transcriptional activation. Elucidation of the mechanism of action of Vmw65 is important for an understanding not only of combinatorial control of gene expression by POU- and homeodomain proteins but also of the interaction(s) between activation domains of regulatory proteins and components of the basal transcriptional apparatus. We used a combination of limited proteolysis with a number of site-specific proteases and immunological detection to demonstrate the presence of two main surface-exposed regions in Vmw65. We mapped these sites to within a few amino acids at positions 365-370 408/409. The site at 408/409 is indicative of a flexible exposed linker region between the acidic carboxy-terminal activation domain (residues 430-480) and an N-terminal domain involved in complex formation with the two cellular factors. The site around residues 365-370 is precisely within a region that results from this and other laboratories have shown to be critical for complex formation. Furthermore, we show that this site is selectively protected from proteolysis after complex assembly. Finally, using a series of overlapping peptide encompassing this region, we show that the eight amino acids, R-E-H-A-Y-S-R-A, from positions 360 through 367 are sufficient to inhibit complex formation by intact Vmw65. We propose that these residues contain sufficient information to selectively bind one of the cellular partners involved in complex assembly and that these residues are located in a physical surface-exposed domain of the protein.

Structural studies of the acidic transactivation domain of the Vmw65 protein of herpes simplex virus using 1H NMR

We have overproduced and purified the carboxy-terminal transactivation domain of Vmw65 (VP16) of herpes simplex virus, and studied potential folding of the domain by 1H NMR. Two species of the acidic domain were obtained from the bacterial expression system, and we demonstrate that one of these represents read-through of the natural amber termination codon of the Vmw65 reading frame producing a larger polypeptide. Additional residues in the read-through product were identified by total amino acid analysis and by NMR. Study of the correctly terminated product by 1D NMR gave resonances which were clustered into groups around their random-coil chemical shift positions, and 2D NMR demonstrated that, even in mixed solvents containing up to 80% MeOH, there was very little evidence of secondary structure. Together these results indicate that the isolated acid domain has little if any alpha-helical content of any stable nature. We discuss these results with reference to the demonstrated activity of the acidic domain in a wide variety of polypeptide contexts.

Mutations in the activation region of herpes simplex virus regulatory protein ICP27 can be trans dominant

The herpes simplex virus type 1 (HSV-1) immediate-early protein ICP27 is an essential regulatory protein which is required for virus replication. Transfection experiments have demonstrated that ICP27 along with the HSV-1 transactivators ICP4 and ICP0 can positively regulate the expression of some late HSV-1 target plasmids and can negatively regulate the expression of some immediate-early and early target plasmids. We previously showed that mutants defective in the activation of a late target plasmid mapped to the carboxy-terminal half of the protein, whereas mutants defective in the repression of an early target plasmid mapped within the C-terminal 78 amino acids of ICP27 (M. A. Hardwicke, P. J. Vaughan, R. E. Sekulovich, R. O'Conner, and R. M. Sandri-Goldin, J. Virol. 63:4590-4602, 1989). In this study, we cotransfected ICP27 activator and repressor mutants along with wild-type ICP27 plasmid to determine whether these mutants could interfere with the wild-type activities. Mutants which were defective only in the activation function were dominant to the wild-type protein and inhibited the activation of the late target plasmid pVP5-CAT, whereas mutants defective in the repressor function did not inhibit either the activation of pVP5-CAT or the repression of the early target plasmid pTK-CAT. Furthermore, cell lines which stably carried three different activator mutants were impaired in their ability to support the growth of wild-type HSV-1 strain KOS, resulting in virus yields 5- to 40-fold lower than in control cells. The defect in virus replication appeared to stem from a decrease in the expression of HSV-1 late gene products during infection as measured by steady-state mRNA levels and by immunoprecipitation analysis of specific polypeptides. These results indicate that ICP27 activator mutations specifically interfere with the activation function of the protein both in transfection and during infection. Moreover, these results suggest that the repressor region may be important for binding of the polypeptide, since mutations in this region did not interfere with the activities of wild-type ICP27 and therefore presumably could not compete for binding.

In vitro transcription and translation of proteins encoded by the BamHI-B genomic fragment of herpes simplex virus-1

The BamHI-B DNA fragment of herpes simplex virus type-1 (HSV-1) is associated with intraperitoneal pathogenicity. Among the recently mapped RNA transcripts from this fragment (15), one was reported to be associated with latency. To relate the RNA transcripts to virus pathogenicity, the in vitro-transcribed RNAs from BamHI-B fragments of three HSV-1 strains--F (pathogenic), R19, and HFEM (apathogenic), were studied by in vitro translation. When the BamHI-HpaI (0.738-0.755 map units) DNA fragment from HSV-1 strain F was transcribed rightward and translated, three proteins of 70, 63, and 51 kD were detected. The 63 kD protein resembles in size and orientation the protein encoded by the ICP-27 (IE-2) gene (0.740-0.749 mu). The 51 kD polypeptide is assumed to be a prematurely terminated form of this protein. No proteins were obtained from RNA transcribed in the opposite direction. The SalI-NcoI (0.746-0.761 mu) fragment of the three HSV-1 strains yielded two proteins of 25 and approximately 15 kD when transcribed rightward and a 35 kD polypeptide from RNA transcribed in the opposite direction. As a result of the genomic deletion in HFEM, it was possible to obtain the 35 kD protein from the SalI-SalI DNA fragment (0.746-0.761 mu) as well. In vitro transcription and translation of the PstI-SalI (0.778-0.790 mu) DNA fragment (the right-hand side of HpaI-P) did not result in protein synthesis. The possibility that the UL56 gene is connected with the intraperitoneal pathogenicity of HSV-1 is discussed.

Seroepidemiology of herpes simplex virus and restriction endonuclease cleavages analysis of herpes simplex virus type 2 in Okinawa

A seroepidemiologic study of herpes simplex virus (HSV) in Okinawa was performed. A total of 423 serum samples were collected from all over Okinawa, and the positivity rate of antibody against HSV was measured using a passive hemagglutination method. The sero-positive rate for HSV in age groups of over 40 years was 100%. Seven HSV type 2 (HSV 2) isolates were obtained in Okinawa, and DNA preparations from Vero cells infected with the isolates were analyzed using five restriction endonucleases: Bam HI, Hind III, Kpn I, Bgl II and Eco RI. Variations in the genomic region were demonstrated in five of the isolates. Such variations have not been reported previously in HSV 2 in mainland Japan. This is the first report of a seroepidemiologic study of HSV and restriction endonuclease cleavage analysis of HSV 2 in Okinawa, is a subtropical island where HSV is endemic.

Structural requirements in the herpes simplex virus type 1 transactivator Vmw65 for interaction with the cellular octamer-binding protein and target TAATGARAT sequences

Herpes simplex virus type 1 virion protein Vmw65 forms a complex (TRF.C) with TAATGARAT sequences and the cellular transcription factor oct-1, which has been implicated as an intermediate in the activation of gene expression by Vmw65. To examine structural requirements within Vmw65 for this interaction, we analyzed extracts of transfected cells that express mutant Vmw65 proteins by gel retardation assay and identified two regions in the primary sequence of Vmw65 which are necessary for in vitro assembly of TRF.C. The amino-terminal boundary for complex assembly and trans activation mapped between residues 49 and 75. At the carboxyl terminus, deletion as far as residue 388 did not affect in vitro TRF.C assembly, although trans-activating activity was abolished. Deletion beyond residue 388 rapidly impaired the ability of the protein to participate in the TRF.C complex, such that a truncated mutant of 380 residues was completely inactive. These requirements towards the carboxyl terminus overlap a region of strong local sequence similarity between Vmw65 and terminal protein p3 of bacteriophage phi 29. Although substitution of corresponding p3 residues into Vmw65 failed to produce a functional chimera, site-directed mutagenesis within the region of similarity identified a number of single-point mutant proteins which were completely deficient for TRF.C formation. These mutant proteins were also unable to trans activate expression from immediate-early promoters, despite the integrity of the acidic carboxyl terminus. The extreme sensitivity of both TRF.C formation and trans activation to single-residue substitutions within this region of Vmw65 suggests that it is directly involved in the protein-protein or protein-DNA interactions required for assembly of a transcriptional complex containing oct-1.

Analysis of the human ornithine aminotransferase gene family

Ornithine aminotransferase is a mitochondrial matrix enzyme that is deficient in patients with gyrate atrophy, an autosomal recessive disease of the eye. Southern blots of human DNA probed with a previously characterized OAT cDNA showed a complex pattern of gene fragments, suggesting a gene family. Hybridization of these blots with 5' and 3' OAT cDNA probes indicated that there are at least three to four copies of the OAT (approximately 22 kbp) and OAT-related gene sequence(s). We have isolated and partially characterized human OAT gene clones from total genomic and X-chromosome DNA libraries. Sequence analysis confirmed the following previously reported findings on the functional OAT gene: 11 exons, ten introns, an atypical TATA box (TTTAA), two CCAAT boxes, several GC-rich binding sites, 5' sequence homologous to SV40 enhancer core sequence (GTGGA/GA/GA/GG) and promoter region of three urea cycle enzymes (GTATCCTGCCCTC). In addition, we extended the OAT gene sequence in both the 5' and 3' directions and found its promoter region also contained a sequence homologous to the progesterone receptor (TGTTCA/TCC/T), several of the glucocorticoid responsive element (AGAACA), a cyclic AMP-responsive element (TGACGTCG), and recognition motifs for transcription factors AP-2, NF1 and Sp1. Partial sequence analyses of X-chromosome clones demonstrated an intron-less pseudogene with 77% identity to the functional OAT gene. These results demonstrate that the OAT gene is a gene family that contains both functional and related OAT gene sequence(s).

The regions important for the activator and repressor functions of herpes simplex virus type 1 alpha protein ICP27 map to the C-terminal half of the molecule

The herpes simplex virus type 1 (HSV-1) alpha or immediate-early proteins ICP4 (IE175), ICP0 (IE110), and ICP27 (IE63) are trans-acting proteins which affect HSV-1 gene expression. We previously showed that ICP27 in combination with ICP4 and ICP0 could act as a repressor or an activator in transfection assays, depending on the target gene (R. E. Sekulovich, K. Leary, and R. M. Sandri-Goldin, J. Virol. 62:4510-4522, 1988). To investigate the regions of the ICP27 protein which specify these functions, we constructed a series of in-frame insertion and deletion mutants in the ICP27 gene. These mutants were analyzed in transient expression assays for the ability to repress or to activate two different target genes. The target plasmids used consisted of the promoter regions from the HSV-1 beta or early gene which encodes thymidine kinase and from the beta-gamma or leaky late gene. VP5, which encodes the major capsid protein, each fused to the chloramphenicol acetyltransferase gene. Our previous studies showed that induction of pTK-CAT expression by ICP4 and ICP0 was repressed by ICP27, whereas the stimulation of pVP5-CAT expression seen with ICP4 and ICP0 was significantly increased when ICP27 was also added. In this study, a series of transfection assays was performed with each of the ICP27 mutant plasmids in combination with plasmids containing the ICP4 and ICP0 genes with each target. The results of these experiments showed that mutants containing insertions or deletions in the region from amino acids 262 to 406 in the carboxy-terminal half of the protein were unable to stimulate expression of pVP5-CAT but were able to repress induction of pTK-CAT activity by ICP4 and ICP0. Mutants in the carboxy-terminal 78 amino acids lost both activities; that is, these mutants did not show repression of pTK-CAT activity or stimulation of pVP5-CAT activity, whereas mutants in the hydrophilic amino-terminal half of ICP27 were able to perform both functions. These results show that the carboxy-terminal half of ICP27 is important for the activation and repression functions. Furthermore, the carboxy-terminal 62 amino acids are required for the repressor activity, because mutants with this region intact were able to repress. Analysis of the DNA sequence showed that there are a number of cysteine and histidine residues encoded by this region which have some similarity to zinc finger metal-binding regions found in other eucaryotic regulatory proteins. These results suggest that the structural integrity of this region is important for the function of ICP27.

Overlapping octamer and TAATGARAT motifs in the VF65-response elements in herpes simplex virus immediate-early promoters represent independent binding sites for cellular nuclear factor III

Expression of the immediate-early (IE) genes of herpes simplex virus (HSV) is specifically stimulated by a 65-kilodalton virion transcription factor (VF65 or VP16) that is introduced as a component of infecting virions. In both the IE175(ICP4) and IE110(ICP0) promoters, this activation requires an upstream cis-acting target response element that contains a single TAATGARAT consensus element. Furthermore, many HSV IE TAATGARAT elements overlap with ATGCTAAT octamer motifs that are similar to the OTF-1-binding sites found in both immunoglobulin and histone H2b genes and to the nuclear factor III (NFIII)-binding site within the adenovirus type 2 origin of DNA replication. Purified HeLa cell NFIII protein proved to form specific DNA-protein complexes with several upstream regions from both the IE110 and IE175 promoters, and this interaction was subject to efficient competition with an adenovirus type 2 DNA fragment containing an intact NFIII-binding site. Surprisingly, the NFIII protein bound to synthetic oligonucleotides containing only the TAATGARAT consensus elements as well as to those containing the ATGCTAAT octamer sequence, although the former exhibited lower affinity and gave complexes with slightly different electrophoretic mobility. The ATGCTAAT oligonucleotide also competed more efficiently than the TAATGARAT sequence itself for binding to a TAATGARAT probe, indicating that the same protein species binds to both sites. The oligonucleotides also formed novel supershifted complexes with lysed virion proteins, but only in the presence of a crude nuclear extract and not with affinity-purified NFIII alone. We conclude that the cellular NFIII protein can recognize both the ATGCTAAT and TAATGARAT elements independently but that only the interaction with TAATGARAT represents an intermediate step in the transcriptional stimulation of IE genes by the HSV virion factor.

DNA binding by the herpes simplex virus type 1 ICP4 protein is necessary for efficient down regulation of the ICP0 promoter

The herpes simplex virus type 1 ICP4 and ICP0 polypeptides are immediate-early proteins that positively and negatively regulate expression of other viral genes in trans. ICP4 has recently been shown to bind DNA bearing the consensus sequence 5'-ATCGTCNNNN(T/C)CG(A/G)C-3', present upstream of a number of viral genes. To test the hypothesis that this DNA-binding activity is involved in ICP4-mediated gene regulation, site-specific mutagenesis was employed to mutate the version of this sequence in the promoter of the ICP0 gene. The mutation eliminated detectable binding of ICP4 to the promoter as measured in vitro by a gel electrophoresis band shift assay. The ability of the mutated ICP0 promoter to direct synthesis of a reporter gene was also investigated in a transient transfection assay. Whereas ICP4 was found to transactivate the wild-type ICP0 promoter two- to threefold, the mutated promoter was transactivated seven- to ninefold. In assays containing the ICP0 transactivator gene, ICP4 down regulated the wild-type promoter far more efficiently than the mutated promoter. Finally, both the wild-type and mutated ICP0 promoters exhibited a similar response to ICP4 in transfections that included a vector expressing the viral transactivator protein VP16. These experiments suggest that the sequence-specific DNA-binding activity of ICP4 is an essential element of its role as a negative regulator of gene expression.

Herpes simplex virus type 2 mutants with deletions in the intergenic region between ICP4 and ICP22/47: identification of nonessential cis-acting elements in the context of the viral genome

In herpes simplex virus type 2, the mRNAs of ICP4 and ICP22/47 are divergently transcribed and their transcription initiation sites are separated by 750 base pairs (L. J. Whitton and J. B. Clements, Nucleic Acids Res. 12:2061-2078, 1984). This 750-base-pair region contains many recognized cis-acting elements, including two TATA boxes, numerous Sp1-binding sites, four TAATGARAT motifs, at least one ICP4-binding site, and two origins of replication (oriS) linked in tandem. In this report, we describe the construction of mutant viruses with defined deletions that eliminate these elements either singly or in combination. The phenotypic properties of these mutants indicate that (i) the TAATGARAT motifs and their neighboring elements affect the levels of transcription of both ICP4 and ICP22/47 similarly, (ii) the TATA box serving ICP4 is required for efficient ICP4 mRNA synthesis and for determining the initiation site of transcription, (iii) the ICP4-binding site located at the start of ICP4 transcription is at least partially responsible for the decreased levels of ICP4 mRNA observed in the presence of immediate-early and early gene products, and (iv) mutants bearing deletions that eliminate the entire conventionally recognized ICP4 promoter generate sufficient ICP4 mRNA to maintain viability in cells not expressing ICP4. Additionally, our inability to generate viable deletion mutants lacking all copies of oriS suggests that at least one copy of oriS may be essential for virus replication.

Separation of requirements for protein-DNA complex assembly from those for functional activity in the herpes simplex virus regulatory protein Vmw65

A transient expression system was developed which results in efficient synthesis of the regulatory protein Vmw65 of herpes simplex virus type 1 in eucaryotic cells. The gene for Vmw65 was linked to the cytomegalovirus immediate-early (IE) promoter-enhancer region in a plasmid containing the simian virus 40 origin of replication. When transfected into COS cells, Vmw65 was expressed from this vector in 25 to 50% of the cells, with total levels of the protein approaching 20% of those observed in infected cells. Vmw65 expressed in this system is functional for specific DNA-binding complex formation with the host cell octamer-binding protein TRF and for transactivation of IE gene expression. We therefore produced a series of carboxy-terminal truncated forms of Vmw65 to examine the structural requirements of the protein for these activities. Deletion of the acidic carboxy-terminal 56 amino acids had no effect on DNA-binding complex formation but completely abolished the ability to transactivate. Amino acids between residues 434 and 453, a region which exhibits a high negative charge, were critical for IE transactivation. In contrast, the requirements for complex formation are located entirely within the N-terminal 403 amino acids, and our results indicate a requirement for this activity for residues between 316 and 403. Together with our previous work, the results presented here indicate that recruitment of TRF into a specific DNA-binding complex on IE consensus signals is required but not sufficient for functional IE transactivation by Vmw65.

Characterization of RNA transcripts from herpes simplex virus-1 DNA fragment BamHI-B

Herpes simplex virus type 1 (HSV-1) DNA fragment BamHI-B (0.738-0.809 map units) was recently reported to be associated with the phenotype of intraperitoneal pathogenicity and to encode a latency-associated RNA transcript. Part of this fragment resides within the internal repeat sequence of the long (L) region of the viral genome. In this study, RNA transcripts from BamHI-B were characterized. In addition to immediate-early mRNAs IE-1 and IE-2, eight novel RNA species were found. Three transcripts were mapped in the repeat regions of this fragment and five transcripts in the unique L region of BamHI-B. In addition, transcription activity from these regions was compared in several HSV-1 strains. These included the intraperitoneal virulent F and KOS strains, the avirulent strain HFEM, as well as the HFEM/F intratypic virulent recombinant R-MIC1. Several differences were noted and their possible relevance to virulence is discussed.

Genomic organization of a sex specific gene: the primary sperm receptor of the mouse zona pellucida

The zona pellucida is an extracellular matrix which surrounds mammalian oocytes and plays an important role in the species-specific fertilization of mammals. The mouse zona is composed of three sulfated glycoproteins one of which, ZP3, serves as the primary sperm receptor in the initial interaction between egg and sperm. We have previously cloned a ZP3 cDNA and shown that the gene for ZP3 is expressed in a precise temporal and spatial fashion only in growing oocytes. We now describe the genomic organization of this gene whose expression is germ-line and female sex-specific. The gene contains 8 exons spanning approximately 8.6 kilobases in the mouse genome where it appears to be present as a single copy gene. S1 analyses of the 5' and 3' ends of the gene define the transcription start and stop sites and show that ZP3 mRNA has very short untranslated regions. Sequence determination has revealed a novel tandem repeat which is reiterated six times in the 5' flanking region and five times in the seventh intron.

Direct correlation between a negative autoregulatory response element at the cap site of the herpes simplex virus type 1 IE175 (alpha 4) promoter and a specific binding site for the IE175 (ICP4) protein

In transient-expression assays, the IE175 (alpha 4) promoter region of herpes simple virus is down-regulated after cotransfection with DNA encoding its own protein product (IE175 or ICP4). The inhibition by IE175 proved to be highly specific for its own promoter region and did not act on either the herpes simplex virus type 1 IE110 (alpha 0) or human cytomegalovirus major immediate-early promoters. Furthermore, the inhibition was still exhibited by IE175 effector plasmids driven by strong heterologous promoters and therefore must be a direct autoregulatory response that cannot be explained by promoter competition effects. In gel mobility retardation assays with infected-cell nuclear extracts, a prominent and specific DNA-protein complex was formed with DNA fragments containing sequences from -108 to +30 in the IE175 promoter region. This activity was not present in mock-infected samples. Even stronger binding occurred with a fragment containing sequences from -128 to +120 in the IE110 promoter, but this second locus was not associated with any detectable response phenotype in cotransfection assays. Supershift experiments with an anti-IE175 monoclonal antibody confirmed the presence of the IE175 protein in both DNA-protein complexes. In the IE175 promoter, specific binding correlated closely with the presence of an intact autoregulatory signal near the cap site as judged by the loss of both activities in a 3'-deleted promoter fragment lacking sequences from -7 to +30. Insertion of a cloned 30-mer synthetic oligonucleotide sequence from positions -8 to +18 in IE175 restored both IE175 binding activity and the down-regulation phenotype. Direct shift-up assays with a similar 30-base-pair (bp) oligonucleotide containing 21 bp from positions -75 to -55 of IE110 (which encompasses a consensus ATCGTC motif) also produced a specific DNA-protein complex containing the IE175 protein. This ATCGTC motif proved to be a necessary component of both the IE110 and IE175 binding sites, but was insufficient on its own for complex formation. Finally, deletion of 2 bp from positions -3 and -4 within the ATCGTC sequence in the IE175 cap site region abolished both binding activity and the IE175-dependent autoregulation phenotype.

Expression of herpes simplex virus type 1 (HSV-1) latency-associated transcripts and transcripts affected by the deletion in avirulent mutant HFEM: evidence for a new class of HSV-1 genes

During latent herpes simplex virus type 1 (HSV-1) infection in the trigeminal ganglia of mice, three virus-specific transcripts, 2.0, 1.5, and 1.45 kilobases (kb), are detectable by Northern (RNA) blot analysis, but only the 2.0-kb transcript can be detected in HSV-1-infected tissue culture cells (J.G. Spivack and N. W. Fraser, J. Virol. 61:3842-3847, 1987). Since these latency-associated genes map to a diploid region of the genome, transcription from the deletion mutant HFEM, which contains only one complete copy of these genes, was investigated to determine the effect of gene dosage. The 4.1-kb HFEM deletion is located between the alpha genes ICP0 and ICP27. ICP0 mRNA and the 2.0-kb latency-associated transcript were present at normal levels during HFEM infection, but ICP27 mRNA and 0.9- and 1.1-kb transcripts that map near the deletion were not readily detectable. The levels of expression of one or more of these genes might be an important determinant of HSV-1 virulence in animal hosts. ICP27 mRNA accumulated when protein synthesis was inhibited before HFEM infection, implying that the deletion may affect ICP27 regulatory rather than coding elements. Expression of the 2.0-kb latency-associated transcript was characterized in infected CV-1 cells with metabolic inhibitors and strand-specific probes. On the basis of metabolic inhibitor studies, the gene encoding the 2.0-kb latency-associated transcript is not an alpha gene. During HSV-1 replication in infected tissue culture cells, the beta and gamma genes require the prior expression of alpha gene products. However, the latency-associated RNAs are expressed in the absence of detectable levels of alpha transcripts in latently infected mice. Thus, this latency-associated gene family appear to be regulated quite differently than alpha, beta, or gamma genes. For these reasons, and because the latency-associated genes may perform latent rather than replicative functions, we propose that they should be considered members of a new HSV-1 gene class, the lambda genes.

Association of herpes simplex virus regulatory protein ICP4 with sequences spanning the ICP4 gene transcription initiation site

The HSV gene encoding ICP4 is negatively regulated and the HSV gene encoding thymidine kinase is positively regulated by ICP4 in vivo. We report that ICP4 is a component of a stable complex that contains protein and a sequence of approximately 28 nucleotides that span the ICP4 gene transcription initiation site. The association of ICP4 with DNA sequences between positions -103 and +32 relative to the ICP4 mRNA start site was demonstrated by DNA binding immunoassays. DNase footprinting revealed that nucleotides between positions -8 and +20 are protected by ICP4. In contrast, binding of ICP4 to sequences flanking the mRNA start site in the thymidine kinase gene was not observed. Models for ICP4-mediated positive or negative regulation of HSV gene transcription are discussed.

Dissection of immediate-early gene promoters from herpes simplex virus: sequences that respond to the virus transcriptional activators

The immediate-early promoters of herpes simplex virus give rise to the first series of transcripts after infection. These promoters are composed of compound sequence elements that govern basal level and regulated transcription. The response of three core (truncated) promoters from the herpes simplex virus type 1 IE-4, IE-0, and IE-27 genes to a battery of virus-encoded trans-acting proteins was examined in a short-term transient expression assay system. The results of this study reveal (i) a role for a sequence, 5'---GGGGG---3', flanked by 3 to 5 base pairs of symmetry (the G box), which is present in the upstream region of all immediate-early gene promoters, (ii) a requirement for the consensus sequence protected by ICP4 for autoregulation by this immediate-early gene product, and (iii) an alternative, sequence-independent mechanism for the augmentation of alpha gene expression by the virion-associated transcriptional activator Vmw65, now designated as TIF.

Epstein-Barr virus gene expression in P3HR1-superinfected Raji cells

The pattern of Epstein-Barr virus (EBV) RNAs expressed in Raji cells superinfected with P3HR1 EBV was examined. RNAs whose expression was of an immediate-early type (resistant to treatment of the cells with anisomycin) were identified. These RNAs, encoding the EBV reading frames BZLF1 and BRLF1, were probably expressed from defective virus within the P3HR1 preparation, and some of them were responsible for the induction of the EBV productive cycle in the Raji cells. The structures of the B95-8 RNAs equivalent to the anisomycin-resistant RNAs were determined. The RNA encoding the BZLF1 reading frame contained two splices which extended and modified the reading frame from that previously described.

Sequences of herpes simplex virus type 1 that inhibit formation of stable TK+ transformants

We have identified two regions of the herpes simplex virus type 1 (HSV-1) genome that inhibit DNA-mediated transformation of thymidine kinase-less L (Ltk-) cells by the cloned HSV-1 tk gene. When plasmids containing the EcoRI fragments EK or JK were mixed at 30 fmol/ml with the tk gene and transfected into Ltk- cells, the frequency of transformation was inhibited 80 to more than 90% relative to the control. Of the remaining 10 EcoRI fragments of the HSV-1 genome, 8 were inactive and 2 were weakly active. A 6.1-kilobase PstI subclone between 0.743 and 0.782 map units was isolated from pEK. This clone, pEK-P3P4, exhibited antitransformation activity toward HSV-1 tk and also the bacterial genes gpt and neo. pEK-P3P4 contains the alpha 27 gene, and restriction endonuclease inactivation and subcloning studies established that alpha 27 alone did not inhibit transformation. However, alpha 27 plus sequences both upstream and downstream of alpha 27 did inhibit transformation. In addition, alpha 0 or alpha 4 could substitute for alpha 27 in effecting antitransformation with these sequences. Therefore, an alpha gene and two additional loci in pEK-P3P4 are required for antitransformation. A second antitransforming locus in the reiterated sequences common to EK and JK and distinct from those in pEK-P3P4 was also identified but not characterized in detail. How antitransformation may be an expression of regulation of viral and host cell gene expression is discussed.

Intertypic recombinants of herpes simplex virus types 1 and 2 infected-cell polypeptide 4

The wild-type ICP4s (infected-cell polypeptide 4) encoded by herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) are functionally interchangeable. In order to test the functional interchangeability of their intramolecular domains, a series of intertypic ICP4 genes was constructed and characterized to determine if any of the encoded chimeric proteins were functionally impaired. We generated the recombinants in Escherichia coli using cloned ICP4 genes and the lambda recombination vectors developed by D. Carroll and R. S. Ajioka (1980, Gene 10, 273-281) and D. Carroll, R. S. Ajioka, and C. Georgopoulos (1980, Gene 10, 261-271). We chose to generate the recombinants in E. coli in order to avoid imposing any restrictions with respect to the biological activities of their chimeric protein products. Six different recombinants encoding chimeric ICP4s were studied. As determined by restriction enzyme analysis, one of the six encodes an ICP4 protein whose amino-terminus is type 1 and whose carboxy-terminus is type 2. Five recombinants encode ICP4 proteins whose amino-termini are type 2 and carboxy-termini, type 1. The recombinant ICP4 proteins were assessed for their ability to stimulate transcription driven by the HSV-1 thymidine kinase promoter and for their ability to complement the growth of d120 and hr259, deletion mutants in HSV-1 and HSV-2 ICP4, respectively. All six recombinants exhibited wild-type levels of functional activity in both assay systems, demonstrating the colinearity of sequences specifying the intramolecular domains of HSV-1 and HSV-2 ICP4 and their functional interchangeability.

The 65,000-Mr DNA-binding and virion trans-inducing proteins of herpes simplex virus type 1

The possible identity of the herpes simplex virus type 1 (HSV-1) 65K (65,000-Mr) virion protein which stimulates transcription from immediate-early genes with the HSV-1 65K DNA-binding protein was investigated. The two proteins were found to be distinct by the three separate criteria of immunological reactivity, tryptic peptide fingerprinting, and mobility in two-dimensional gels. Using HSV-1/HSV-2 intertypic recombinants and a serotype-specific antiserum, we located the gene encoding the 65K DNA-binding protein between coordinates 0.574 and 0.682 on the HSV-1 genome. The protein is posttranslationally modified by phosphorylation. In crude extracts of HSV-1-infected cells the 65K trans-inducing protein did not detectably bind to double-stranded calf thymus DNA under the conditions of our assay.

Herpes simplex virus virion stimulatory protein mRNA leader contains sequence elements which increase both virus-induced transcription and mRNA stability

To investigate the role of 5' noncoding leader sequence of herpes simplex virus type 1 (HSV-1) mRNA in infected cells, the promoter for the 65,000-dalton virion stimulatory protein (VSP), a beta-gamma polypeptide, was introduced into plasmids bearing the chloramphenicol acetyltransferase (cat) gene together with various lengths of adjacent viral leader sequences. Plasmids containing longer lengths of leader sequence gave rise to significantly higher levels of CAT enzyme in transfected cells superinfected with HSV-1. RNase T2 protection assays of CAT mRNA showed that transcription was initiated from an authentic viral cap site in all VSP-CAT constructs and that CAT mRNA levels corresponded to CAT enzyme levels. Use of cis-linked simian virus 40 enhancer sequences demonstrated that the effect was virus specific. Constructs containing 12 and 48 base pairs of the VSP mRNA leader gave HSV infection-induced CAT activities intermediate between those of the leaderless construct and the VSP-(+77)-CAT construct. Actinomycin D chase experiments demonstrated that the longest leader sequences increased hybrid CAT mRNA stability at least twofold in infected cells. Cotransfection experiments with a cosmid bearing four virus-specified transcription factors (ICP4, ICP0, ICP27, and VSP-65K) showed that sequences from -3 to +77, with respect to the viral mRNA cap site, also contained signals responsive to transcriptional activation.

Herpes simplex virus immediate-early promoters are responsive to virus and cell trans-acting factors

The promoters for each of the immediate-early genes from herpes simplex virus type 1 were cloned and fused to a chloramphenicol acetyltransferase cassette. These chimeric genes were used as targets in a transient expression assay to determine how the immediate-early gene products ICP4 and ICP0 and the virion-associated stimulatory protein Vmw65 affected their expression in HeLa and Vero cells. The basal level of expression from these cassettes differed significantly depending on the extent of 5'-flanking sequence and the cell line that served as host. The promoters from IE-4 and IE-0 behaved in a qualitatively similar fashion independent of the host cell. However, the promoter for ICP27 had a unique response pattern: in Vero cells it acted as an alpha gene promoter, whereas in HeLa cells its response was more like that of a beta gene promoter. The promoter sequences for ICP22 and ICP47 behaved as the IE-4 and IE-0 promoters did in HeLa cells, but their response to the effector molecules in Vero cells was unlike that of other alpha gene promoters we have studied. Evidence is also presented for a role for ICP27 in autoregulation.

DNA sequences which regulate the expression of the pseudorabies virus major immediate early gene

It has been shown previously that the transcription of herpes simplex virus (HSV) immediate early (IE) genes is transactivated by a component of the virus particle. The trans-inducing factor (TIF) is known to be polypeptide Vmw65. Infection with pseudorabies virus (PRV), a related herpesvirus, does not increase expression from HSV IE regulatory sequences (W. Batterson and B. Roizman, 1983, J. Virol. 46, 371-377). To examine the control of the PRV IE gene and possible sequence specificity of a TIF, the 5' terminus of the PRV major IE transcript was mapped and hybrid plasmids containing PRV upstream sequences linked to the HSV-1 TK gene were constructed. Gene expression under the control of PRV IE or HSV-1 IE gene 3 upstream regions were compared using transient expression assays. It was found that infection with uv-irradiated PRV did not stimulate expression from PRV IE or from HSV-1 IE gene 3 upstream regions, indicating that PRV did not possess an effective TIF. Infection with uv-treated HSV-1, or cotransfection with a plasmid which encodes Vmw65, stimulated expression from both PRV and HSV IE gene upstream regions. The nucleotide sequence of the 5' end of the PRV transcript and its upstream region was determined. This region was, in overall structure, unlike the upstream regions of HSV IE genes but showed a strong similarity to the enhancers of human and murine cytomegaloviruses (HCMV and MCMV). In particular, a reiterated 15-bp element of the PRV upstream region was homologous to a conserved, repeated sequence element found in both HCMV and MCMV enhancer regions and was also related to the "TAATGARATTC" motif found upstream of all HSV IE genes. Thus a conserved sequence element occurs upstream of IE genes in four herpesviruses with different genome structures and diverse biological properties.

Conserved 12-bp element downstream from mRNA polyadenylation sites

Sequences downstream from the AATAAA motif in a number of cellular and viral transcription units have been compared. A 12-bp conserved element was identified in approximately half of the cases studied, and a consensus sequence TTGANNNTTTTTT was derived from a comparison of 74 such sequences. This element is located immediately (5-20 bp) downstream from the poly(A)-addition site in every case where this is known, and it is suggested that this element may be involved in the cleavage/polyadenylation reaction. This proposal is consistent with published studies on deletion mutants of downstream regions.

Comparison of upstream sequence requirements for positive and negative regulation of a herpes simplex virus immediate-early gene by three virus-encoded trans-acting factors

Using a short-term cotransfection system with recombinant chloramphenicol acetyltransferase (CAT) target genes and intact genes for regulatory proteins, we previously demonstrated that expression from the promoter-regulatory region of the gene for the immediate-early 175,000-molecular-weight (IE175K) protein of herpes simplex virus type 1 was subject to trans-acting effects by three different virus-encoded components. In the present work we have attempted to delineate the upstream cis-acting requirements within the IE175K promoter-regulatory region for stimulation by the late structural protein Vmw65, stimulation by the IE110K protein, and repression by its own gene product, the IE175K protein. Our results augment previous reports of others by demonstrating that a construct containing only the single TAATGARAT consensus sequence, TAATGGAAT, between -115 and -106 was efficiently induced by Vmw65. Deletion to -108 effectively abolished the response to Vmw65. However, this latter construct remained responsive to IE110K stimulation and was induced as efficiently as the parental construct which contained sequences to -1900. Furthermore, not only basal levels of expression, but also Vmw65 activation of the parental construct and deletion mutants delta 380, delta 330, delta 300, and delta 160 and IE110K-activated expression of the delta 108 construct were all subject to dominant repression by the IE175K protein. Finally, we show that expression from each of the deletions was open to stimulation by linkage to the simian virus 40 enhancer region. Enhancer-stimulated expression from each construct, including the -108 deletion, was efficiently repressed by the IE175K protein. In contrast, expression from the simian virus 40 enhancer when linked to its own promoter was unaffected by IE175K. These results place sequence requirements for both IE110K stimulation and IE175K autoregulation within the minimal promoter region -108 to +30, separate from the major requirements for Vmw65 activation located further upstream.

The control of herpes simplex virus type-1 late gene transcription: a 'TATA-box'/cap site region is sufficient for fully efficient regulated activity

The transcriptional programme of herpes simplex virus type 1 (HSV-1) is organised into three principle phases; immediate-early (IE), early (E) and late. The appearance of IE gene products provides the switch for E transcription. Abundant expression of late genes requires viral DNA replication. There is some overlap between E and late genes according to their degree of dependence on DNA replication. The pattern of expression of gene US11 is regulated with 'true-late' kinetics (Johnson et al., 1986). In a transient assay system, regulation of a plasmid-borne US11 promoter mimics its viral counterpart, and has a similar dependence on DNA replication for abundant expression. Using plasmids which contain a functional HSV-1 origin of replication (ORIS), we have identified the sequence requirements for the expression of late genes. All DNA sequence elements necessary for fully efficient regulated expression of US11 lie within 31 bp of the RNA cap sites; therefore it appears that a late gene promoter consists only of a proximal 'TATA-box' and cap-site region. We tested this hypothesis by removing the distal upstream region of the gD promoter (which is required for its normal regulation as an early promoter) and linking this truncated promoter to ORIS. This resulted in the conversion of gD promoter regulation to late gene kinetics during virus superinfection. The implications of these results for the mechanisms of HSV gene regulation are discussed.

Multiple adjacent or overlapping loci affecting the level of gC and cell fusion mapped by intratypic recombinants of HSV-1

We have prepared and analyzed 40 HSV-1 intratypic recombinants with regard to plaque morphology and glycoprotein C(gC) phenotypes. Vero cells have been cotransfected with the intact genome of HSV-1(F) and cloned or uncloned DNA fragments from HSV-1(MP) and recombinants inducing the fusion of Vero cells [syncytial (Syn) recombinants] have been selected and purified. Marker transfer of the Syn phenotype has been observed with the cloned BamHI L and B fragments (0.706-0.745 and 0.745-0.810 map units, respectively) as well as with the uncloned HpaI TXO fragment (0.710-0.761) from MP DNA. No marker transfer has been observed with F DNA alone or with the cloned BamHI N fragment (0.863-0.898 map units). When viruses expressing the Syn phenotype in Vero cells were tested in HEp-2 cells, three kinds of recombinants were observed. Members of the first class expressed a wild type, cytoaggregating (Syn+), plaque morphology in these cells. Members of the second class induced the complete fusion (Syn phenotype) of the cells. Members of the third class induced an intermediate plaque morphology, characterized by the formation of groups of polykaryocytes (fused cells) but without formation of a complete syncytium. All recombinants expressing the Syn+ phenotype in HEp-2 cells were also gC+, whereas recombinants expressing the Syn phenotype in these cells were gC- with one exception, in which low levels of gC could be detected (but clearly less than with HSV-1(F]. Concerning polykaryocytic class of recombinants, some of them were gC+ while others expressed only low amounts of gC; no gC- virus was observed within this class of recombinants. The three classes of recombinants were observed with each of the cloned BamHI L and B fragments and also with the HpaI TXO fragment, suggesting the existence of multiple adjacent or overlapping loci affecting plaque morphology and the control of the accumulation or the synthesis of gC at both sides of 0.745 map units.

Analysis of DNA sequences which regulate the transcription of herpes simplex virus immediate early gene 3: DNA sequences required for enhancer-like activity and response to trans-activation by a virion polypeptide

The far upstream region of herpes simplex virus (HSV) immediate early (IE) gene 3 has previously been shown to increase gene expression in an enhancer-like manner, and to contain sequences which respond to stimulation of transcription by a virion polypeptide, Vmw65. To analyse the specific DNA sequences which mediate these functions, sequential deletions from each end of the far upstream region were made. The effects of the deletions on transcription in the absence or presence of the Vmw65 were measured by use of a transient expression assay. The enhancer-like activity was due to three separable elements, whereas two additional DNA regions were involved in the response to Vmw65. One of the responding elements corresponded to an AT-rich consensus (TAATGARATTC, where R = purine) present in all IE gene far upstream regions, and the other was a GA-rich sequence also present in IE genes 2 and 4/5. The TAATGARATTC element could mediate responsiveness to Vmw65 but it was fully active only in the presence of the GA-rich element. The GA-rich element was unable to confer a strong response alone but could activate an otherwise nonfunctional homologue of TAATGARATTC.

A modular system for the assay of transcription regulatory signals: the sequence TAATGARAT is required for herpes simplex virus immediate early gene activation

A modular system for assaying the activity of transcriptional regulatory signals based on herpes simplex virus (HSV) promoter and terminator sequences linked to the bacterial chloramphenicol acetyltransferase (CAT) gene has been used to study activation of HSV immediate early (IE) gene expression. Insertion of the SV40 72 base pair (bp) repeat increased mRNA levels by 15-fold thus demonstrating the ability of the HSV IE promoter to respond to a heterologous enhancer. A fragment containing part of the intergenic region located between HSV-2 immediate early (IE) genes-3 and -4/-5 increased mRNA levels by 5-fold in response to transactivation by an HSV virion structural polypeptide. The HSV activator fragment increased mRNA levels by 2-fold in the absence of transactivation indicating that cellular proteins are involved in IE gene expression. From HSV-1/HSV-2 DNA sequence comparisons we previously proposed that a DNA sequence, consensus TAATGARAT, present upstream of all HSV-1 and HSV-2 IE genes was required for the co-ordinate induction of IE genes. We show here that a synthetic oligonucleotide containing TAATGARAT conferred the ability to stimulate CAT activity only on transactivation: two copies of TAATGARAT stimulated expression by 2-fold while six copies gave an 8-fold increase. This activation, which was not dependent on orientation of the TAATGARAT sequence, directly demonstrates that TAATGARAT is a component of the IE gene activation sequence.

DNA sequence of the herpes simplex virus type 1 gene whose product is responsible for transcriptional activation of immediate early promoters

Previous work has shown that transcriptional activation of herpes simplex virus type 1 (HSV-1) immediate early genes is mediated by a protein species (Vmw65) present in the tegument of infecting virions. This paper describes DNA sequence analysis and mRNA mapping of the Vmw65 gene in HSV-1 strain 17. The Vmw65 coding region was identified as a 490 codon sequence encoding a polypeptide of molecular weight 54,342 and characterised by a high proportion of charged amino acid residues. A homologue to Vmw65 was detected in the genome of varicella-zoster virus, another human herpesvirus. Apart from its role in trans-activation, Vmw65 is a major constituent of the virion. Its possible significance in virus structure is discussed.

Cells that constitutively express the herpes simplex virus immediate-early protein ICP4 allow efficient activation of viral delayed-early genes in trans

To study the role of herpes simplex virus type 1 immediate-early proteins in the transcriptional activation of herpes simplex virus genes, we isolated stably transformed cells expressing herpes simplex virus type 1 ICP4, an immediate-early protein known from previous studies to be necessary for delayed-early and late transcription. These cells efficiently expressed six delayed-early herpes simplex virus genes introduced by viral superinfection, in the absence of de novo viral protein synthesis. In contrast, the delayed-early gene encoding alkaline exonuclease and the late gene encoding the capsid protein VP5 were expressed at much lower levels. Expression of a second late gene, that for glycoprotein C, was undetectable under the same experimental conditions. These results suggest that many, but not all, delayed-early genes are efficiently activated by ICP4; in addition, they demonstrate that although the late gene for VP5 is detectably activated by ICP4, its full expression requires additional factors.

The consensus sequence YGTGTTYY located downstream from the AATAAA signal is required for efficient formation of mRNA 3' termini

Our previous DNA sequence comparisons of 3' terminal portions from equivalent herpes simplex virus type 1 (HSV-1) and HSV-2 genes identified a conserved sequence (consensus YGTGTTYY; Y = pyrimidine) located approximately 30bp downstream from the AATAAA signal. We report here that this signal is located downstream from 67% of the mammalian mRNA 3' termini examined. Using constructions with the bacterial chloramphenicol acetyl transferase (CAT) gene linked to an HSV 'terminator' fragment, we show that deletions in the 'terminator' reduce CAT activities and the levels of CAT mRNA 3' termini. Specifically: (1) deletions of downstream sequences which extend up to the consensus YGTGTTYY signal reduce CAT levels to values 35% of those obtained with undeleted plasmids, (2) a deletion of a further 14bp, which removes the YGTGTTYY consensus but not the poly A site, reduces CAT activities to 1%-4%. The levels of CAT mRNA 3' termini reflect the reductions in CAT activities however, levels of mRNA 5' termini are unaffected by these deletions. The RNA produced in the absence of the YGTGTTYY signal is present in the cytoplasm although no CAT activity is detectable.

Trans activation of transcription by herpes virus products: requirement for two HSV-1 immediate-early polypeptides for maximum activity

The transcriptional programme of the herpes viruses is organised into three principal phases. The immediate-early (IE) genes are the first to be transcribed, by the pre-existing host RNA polymerase II, and their promoters are strongly stimulated by a polypeptide component of the virus particle. The E and L gene promoters become active only after the appearance of IE gene products. Genetic and biochemical evidence has shown that the HSV-1 IE polypeptide Vmw175 (ICP 4) is essential for the trans activation of HSV early promoters, but the role of none of the other four IE gene products was known. This paper describes functional tests that show, by co-transfection of recombinant plasmids into HeLa cells, that (i) Vmw175 alone can activate an HSV-1 E gene promoter, (ii) the four other HSV-1 IE gene products by themselves are unable to activate transcription, (iii) the combination of Vmw175 plus the product of IE gene 1, Vmw110 (ICP 0), is a much better activator than Vmw175 alone, (iv) cloned IE gene products of human cytomegalovirus (CMV), varicella-zoseter virus (VZV) and pseudorabies virus (PRV) can also activate transcription from an HSV-1 early promoter, and (v) this activation also occurs with cellular promoters.

Identification of herpes simplex virus DNA sequences which encode a trans-acting polypeptide responsible for stimulation of immediate early transcription

Herpes simplex virus (HSV) immediate early (IE) transcription is known to be stimulated by a structural component of the virion which interacts, either directly or indirectly, with specific regulatory sequences located far upstream from IE messenger RNA 5'-termini. The aim of the work described in this paper is the mapping and identification of the virion component. Cloned HSV DNA fragments derived from various parts of the genome were cotransfected into BHK cells together with chimaeric plasmids which contained the thymidine kinase gene under IE control. Stimulation of thymidine kinase synthesis was elicited by cloned EcoRIi (0.63 to 0.72 map units), BamHIf (0.64 to 0.69) or EcoRIb (0.72 to 0.87). Cloned BamHIf had the same specificity as the virion component, since it stimulated thymidine kinase expression only from chimaeric plasmids which contained functional IE-specific regulatory sequences. The effect of EcoRIb was not confined to plasmids with IE-specific regulatory regions, suggesting a more general stimulatory role for one or more of the polypeptides encoded by this fragment. A subclone containing a 2.7 X 10(3) base-pair fragment of BamHIf (pMC1) was active in the cotransfection assay, and the effect was abolished by an eight base-pair insertion into the middle of this fragment. The only polypeptide known to map entirely within the HSV genome region defined by pMC1 was identified as the major tegument species Vmw65. The results therefore suggest that Vmw65 is the virion component which trans-activates HSV IE transcription.

A tandemly reiterated DNA sequence in the long repeat region of herpes simplex virus type 1 found in close proximity to immediate-early mRNA 1

The 3' end of immediate-early mRNA 1 was mapped precisely within the IRL/TRL genome regions, and the DNA sequences around the 3' end were determined. An AATAAA polyadenylation signal was present 17 base pairs upstream of the 3' end, and eight tandemly repeated copies of a 16-base-pair sequence (GGGGGTGCGTGGGAGT) plus one further closely related copy were located 20 base pairs downstream. Other tandem reiterations present in the herpes simplex virus genome are described and their properties are considered.

Extensive homology between the herpes simplex virus type 2 glycoprotein F gene and the herpes simplex virus type 1 glycoprotein C gene

The region of the herpes simplex virus type 2 (HSV-2) genome which maps colinearly with the HSV-1 glycoprotein C (gC) gene has been cloned, and the DNA sequence of a 2.29-kilobase region has been determined. Contained within this sequence is a major open reading frame of 479 amino acids. The carboxyterminal three-fourths of the derived HSV-2 protein sequence showed a high degree of sequence homology to the HSV-1 gC amino acid sequence reported by Frink et al. (J. Virol. 45:634-647, 1983). The amino-terminal region of the HSV-2 sequence, however, showed very little sequence homology to HSV-1 gC. In addition, the HSV-1 gC sequence contained 27 amino acids in the amino-terminal region which were missing from the HSV-2 protein. Computer-assisted analysis of the hydrophilic and hydrophobic properties of the derived HSV-2 sequence demonstrated that the protein contained structures characteristic of membrane-bound glycoproteins, including an amino-terminal signal sequence and carboxy-terminal hydrophobic transmembrane domain and charged cytoplasmic anchor. The HSV-2 protein sequence also contained seven putative N-linked glycosylation sites. These data, in conjunction with mapping studies of Para et al. (J. Virol. 45:1223-1227, 1983) and Zezulak and Spear (J. Virol. 49:741-747, 1984), suggest that the protein sequence derived from the HSV-2 genome corresponds to gF, the HSV-2 homolog of HSV-1 gC.

Analysis of DNA sequences which regulate the transcription of a herpes simplex virus immediate early gene

The locations and functions of DNA sequences involved in transcription of the gene encoding herpes simplex virus type 1 immediate early (IE) mRNAs 4 and 5 were analyzed by use of a transient-expression assay. The region upstream of the genes encoding IE mRNAs 4 and 5 was fused to the thymidine kinase gene coding sequences, and production of enzyme or RNA was measured after transfection of plasmids into BHK cells. The effect of deletions in the upstream region was determined in the absence or presence of a virus structural component which stimulates herpes simplex virus IE transcription. Two distinct units were identified. One of these was a promoter which required not more than 69 base pairs of DNA specific for the genes encoding IE mRNAs 4 and 5 upstream from the mRNA 5' terminus. The other was a far-upstream region which mediated the response to the virion component and had an upstream boundary between nucleotides -347 and -335. An origin of DNA replication was interposed between these two units. The element TAATGAGATAC , which represents a consensus sequence present in the upstream regions of all herpes simplex type 1 IE genes, appeared to be essential for stimulation by the virion component. The activity of this element was modulated by the sequences which flank it, especially by regions having extremely high contents of guanine plus cytosine and which contain a conserved unit CCCGCCC or its complement GGGCGGG .

A 3' co-terminal family of mRNAs from the herpes simplex virus type 1 short region: two overlapping reading frames encode unrelated polypeptide one of which has highly reiterated amino acid sequence

We have used DNA sequencing, mRNA mapping and in vitro translation to characterise three partially overlapping genes in the genome of herpes simplex virus (HSV) type 1. These genes specify three mRNAs with distinct 5' termini but a common 3' terminus, the longest of which is immediate-early (IE) mRNA-5. The 12,000 MW (12K) IE polypeptide encoded by IEmRNA-5 is translated from an 88 codon open reading frame, leaving a 1200 base 3' non-translated region. The second mRNA (mRNA-B) is initiated within the coding sequence of IEmRNA-5, and encodes a 21K polypeptide. The 12K and 21K polypeptide coding regions do not overlap. The third mRNA (mRNA-C) is initiated within the coding region of mRNA-B, and encodes a 33K polypeptide. The reading frame for 33K has a 110 codon out-of-frame overlap with the 21K reading frame. This is the first instance of overlapping genes described for HSV. The 21K polypeptide is thought to be a DNA binding protein and is remarkable for an array of 24 tandem repeats of the sequence X/Pro/Arg (where X represents predominantly Glu, Asp, Thr, Ser or Val) in its C-terminal portion. This array, which occupies most of the region of overlap with 33K, can vary in repeat number between virus strains.

Replication origins and a sequence involved in coordinate induction of the immediate-early gene family are conserved in an intergenic region of herpes simplex virus

We have determined the structure of the 5' portion of herpes simplex virus type 2 (HSF-2) immediate-early (IE) mRNA-3 and have obtained the DNA sequence specifying the N terminus of its encoded polypeptide, Vmw182, its untranslated leader and the intergenic region between IEmRNAs-3 & 4/5. Comparison of the HSV-2 intergenic sequences with the HSV-1 equivalent region identifies several conserved regions: (1) an AT-rich element with core consensus TAATGARAT which is likely to be the 'activator' sequence through which coordinate induction of the IE gene family is mediated. (2) GC-rich and GA-rich tracts, found in a wide variety of eukaryotic promoters, which vary in position and orientation between HSV-2 and HSV-1 and which represent modulators of transcription. (3) TATA homologies present 15-25 base pairs (bp) upstream of mRNA 5' termini. (4) a 137bp direct repeat in HSV-2 which contains sequence almost identical to the HSV-1 replication origin.

Transcriptional regulation of a herpes simplex virus immediate early gene is mediated through an enhancer-type sequence

An enhancer-type sequence has been identified in the promoter region for the herpes simplex virus type 1 (HSV-1) immediate early (IE) mRNA 3. The enhancer-type activity is host cell dependent, being greater in human cells and Syrian hamster cells (the usual host cell for in vitro propagation of HSV) than in Chinese hamster or mouse cells. Enhancer activity is stimulated up to 10-fold after superinfection by tsK, a temperature-sensitive mutant of HSV-1. The induction of enhancer activity is independent of de novo protein synthesis, showing that trans-activation is effected by a component of the virion. We propose that trans-regulation of IE mRNA 3 is mediated through an enhancer-type sequence, and that this provides one explanation for previously described regulation of HSV IE mRNAs by virion components.