Herpes Simplex Virus DNA Synthesis Research Articles

Resveratrol suppresses nuclear factor-κB in herpes simplex virus infected cells

Resveratrol inhibits herpes simplex virus (HSV) replication by an unknown mechanism. Previously it was suggested that this inhibition may be mediated through a cellular factor essential for HSV replication [Docherty, J.J., Fu, M.M., Stiffler, B.S., Limperos, R.J., Pokabla, C.M., DeLucia, A.L., 1999. Resveratrol inhibition of herpes simplex virus replication. Antivir. Res. 43, 145–155]. After examining numerous cellular factors, we report that resveratrol suppresses NF-kappaB (NF-κB) activation in HSV infected cells. Reports have indicated that HSV activates NF-κB during productive infection and this may be an essential aspect of its replication scheme [Patel, A., Hanson, J., McLean, T.I., Olgiate, J., Hilton, M., Miller, W.E., Bachenheimer, S.L., 1998. Herpes simplex type 1 induction of persistent NF-kappa B nuclear translocation increases the efficiency of virus replication. Virology 247, 212–222; Gregory, D., Hargett, D., Holmes, D., Money, E., Bachenheimer, S.L., 2004. Efficient replication by herpes simplex virus type 1 involves activation of the IkappaB kinase-IkappaB-RelA/p65 pathway. J. Virol. 78, 13582–13590]. Electromobility shift assays determined that resveratrol, in a dose dependent and reversible manner, suppressed activation of NF-κB in Vero cells infected with HSV-1, HSV-2 and acyclovir resistant HSV-1. Furthermore, resveratrol did not protect IκBα, a cytoplasmic NF-κB inhibitor, from degradation in HSV-1 infected cells. Immunohistochemical studies demonstrated that RelA/p65, a component of the dimeric NF-κB complex, translocated to the nucleus of HSV-1 infected cells in the presence of resveratrol. Finally, direct effects on viral transcription and DNA synthesis were evaluated. Real-time RT-PCR analysis showed that resveratrol treatment of infected cells resulted in reductions of mRNA for ICP0, ICP4, ICP8 and HSV-1 DNA polymerase by 2.1-, 3.3-, 3.8- and 3.1-fold, respectively. Plus, mRNA for glycoprotein C, an HSV late gene, was completely absent in the presence of resveratrol. Lastly, quantitative PCR showed that resveratrol significantly blocked HSV DNA synthesis. Cumulatively, these data indicate that resveratrol (i) suppresses HSV induced activation of NF-κB within the nucleus and (ii) impairs expression of essential immediate-early, early and late HSV genes and synthesis of viral DNA.

Herpes Simplex Virus DNA Synthesis Is Not a Decisive Regulatory Event in the Initiation of Lytic Viral Protein Expression in Neurons In Vivo during Primary Infection or Reactivation from Latency

The herpes simplex virus genome can enter a repressed transcriptional state (latency) in sensory neurons of the host nervous system. Although reduced permissiveness of the neuronal environment is widely accepted as a causal factor, the molecular pathway(s) directing and maintaining the viral genome in the latent state remains undefined. Over the past decade, the field has been strongly influenced by the observations of Kosz-Vnenchak et al., which have been interpreted to indicate that, in sensory neurons in vivo, a critical level of viral DNA synthesis within the neuron is required for sufficient viral immediate-early (IE) and early (E) gene expression (M. Kosz-Vnenchak, J. Jacobson, D. M. Coen, and D. M. Knipe, J. Virol. 67:5383-5393, 1993). The levels of IE and E genes are, in turn, thought to regulate the decision to enter the lytic cycle or latency. We have reexamined this issue using new strategies for in situ detection and quantification of viral gene expression in whole tissues. Our results using thymidine kinase-null and rescued mutants as well as wild-type strains in conjunction with viral DNA synthesis blockers demonstrate that (i) despite inhibition of viral DNA replication, many neurons express lytic viral proteins, including IE proteins, during acute infection in the ganglion; (ii) at early times postinoculation, the number of neurons expressing viral proteins in the ganglion is not reduced by inhibition of viral DNA replication; and (iii) following a reactivation stimulus, the numbers of neurons and apparent levels of lytic viral proteins, including IE proteins, are not reduced by inhibition of viral DNA replication. We conclude that viral DNA replication in the neuron per se does not regulate IE gene expression or entry into the lytic cycle.

DNA-replication complex from cells infected with herpes virus.

Herpes simplex virus (HSV) DNA synthesis is initiated in an intact cell system by a 36-residue ribonucleotide stretch [W.E.G. Müller, R.K. Zahn, J. Arendes, and D. Falke (1979) Virology, 98, 200-210]. In the present study a nucleoplasmic fraction was isolated from rabbit kidney cells infected with HSV (type 1), which catalyzes DNA synthesis. By means of specific assays, containing single-stranded deoxyribopolymers, it was elucidated that the replication complex contains both an RNA-synthesizing and a DNA-synthesizing enzyme. These enzymes were characterized as host cell RNA polymerase II and HSV-induced DNA polymerase. The RNA polymerase II synthesizes an RNA initiator with an average chain length of 25 nucleotides, to which the newly synthesized DNA is covalently attached. The chemical nature of the RNA primer was proven by degradation experiments with endoribonuclease V. In the absence of any initiator in the reaction mixture the HSV-induced DNA polymerase is inactive. Kinetic experiments revealed that DNA synthesis in assays containing poly(dT), dNTPs and NTPs starts after a lag phase of 10 min during which the RNA initiator is synthesized. The HSV DNA NTPs starts after a lag phase of 10 min during which the RNA initiator is synthesized. The HSV DNA replication complex was further fractionated into HSV-induced DNA polymerase and the three cellular RNA polymerases. In the reconstructed system DNA synthesis, catalyzed by virus-induced DNA polymerase starts in a reaction assay, containing single-stranded DNA template, only in the presence of RNA polymerase II. The conclusion that the subnucleoplasmic complex, isolated from HSV-infected cells, is of biological significance for HSV DNA synthesis stems (a) from the the close correlations of the known biochemical events occurring during the initiation of HSV DNA synthesis in intact cells and in the nucleoplasmic system and (b) from control experiments with a subnucleoplasmic complex, isolated from uninfected cells, which is devoid of any potency to initiate DNA synthesis.

The antiviral agent 5-chloro-1,3-dihydroxyacridone interferes with assembly and maturation of herpes simplex virus

Antiviral drug screening and exploratory mechanistic work identified 5-chloro-1,3-dihydroxyacridone as a lead inhibitor of herpes simplex virus (HSV) replication, one without a primary effect on either HSV DNA or late viral protein synthesis (Antivir. Res. 45 (2000) 123). In this report, drug effects on viral DNA cleavage and packaging, HSV capsid production and virion morphogenesis in infected Vero cells were studied systematically in order to better localize the sensitive stage of the replication cycle. Maturation of replicating HSV DNA and virion production at late times were inhibited in the same dose-dependent fashion, suggesting that the drug might directly inhibit the cleavage and packaging processes. Based on density centrifugation analysis however, this possibility appears unlikely because overproduction of neither A- or B-capsids occurred upon drug treatment. Interestingly, similar studies coupled with either Western immunoblot or ultrastructural analysis showed that B-capsids with apparent normal protein composition accumulated at reduced levels (maximally about two- to three-fold) in drug-treated cells. Limited attempts to isolate drug-resistant viral mutants using standard approaches proved unsuccessful. In summery, 5-chloro-1,3-dihydroxyacridone inhibits one or more steps of HSV assembly since treatment results in reduced levels of capsids (particularly B-type) and reduced levels of encapsidated DNA. The action of the acridone derivative is an unusual one, with distinctive features when compared to a recently reported class of HSV encapsidation inhibitor and to the late replication defects of relevant viral mutants.

Roscovitine, a specific inhibitor of cellular cyclin-dependent kinases, inhibits herpes simplex virus DNA synthesis in the presence of viral early proteins.

We have previously shown that two inhibitors specific for cellular cyclin-dependent kinases (cdks), Roscovitine (Rosco) and Olomoucine (Olo), block the replication of herpes simplex virus (HSV). Based on these results, we demonstrated that HSV replication requires cellular cdks that are sensitive to these drugs (L. M. Schang, J. Phillips, and P. A. Schaffer. J. Virol. 72:5626-5637, 1998). We further established that at least two distinct steps in the viral replication cycle require cdks: transcription of immediate-early (IE) genes and transcription of early (E) genes (L. M. Schang, A. Rosenberg, and P. A. Schaffer, J. Virol. 73:2161-2172, 1999). Since Rosco inhibits HSV replication efficiently even when added to infected cells at 6 h postinfection, we postulated that cdks may also be required for viral functions that occur after E gene expression. In the study presented herein, we tested this hypothesis directly by measuring the efficiency of viral replication, viral DNA synthesis, and expression of several viral genes during infections in which Rosco was added after E proteins had already been synthesized. Rosco inhibited HSV replication, and specifically viral DNA synthesis, when the drug was added at the time of release from a 12-h phosphonoacetic acid (PAA)-induced block in viral DNA synthesis. Inhibition of DNA synthesis was not a consequence of inhibition of expression of IE or E genes in that Rosco had no effect on steady-state levels of two E transcripts under the same conditions in which it inhibited viral DNA synthesis. Moreover, viral DNA synthesis was inhibited by Rosco even in the absence of protein synthesis. In a second series of experiments, the replication of four HSV mutants harboring temperature-sensitive mutations in genes essential for viral DNA replication was inhibited when Rosco was added at the time of shift-down from the nonpermissive to the permissive temperature. Viral DNA synthesis was inhibited by Rosco under these conditions, whereas expression of viral E genes was not affected. We conclude that cellular Rosco-sensitive cdks are required for replication of viral DNA in the presence of viral E proteins. This requirement may indicate that HSV DNA synthesis is functionally linked to transcription, which requires cdks, or that both viral transcription and DNA replication, independently, require viral or cellular factors activated by Rosco-sensitive cdks.

The effects of lithium and potassium on macromolecular synthesis in herpes simplex virus-infected cells.

All herpes simplex virus (HSV) infected cell-specific polypeptides (ICSPs) were synthesized in the presence of lithium at a concentration (60 mM) inhibitory to the production of infectious virus. Yields of certain ICSPs were increased and others, in particular glycoprotein C, decreased. HSV DNA synthesis was completely inhibited; synthesis and in vitro activities of HSV DNA polymerase and thymidine kinase were decreased but to a degree insufficient to account for the complete inhibition of HSV DNA synthesis. HSV DNA synthesis was inhibited to an equivalent degree by either incubation with 60 mM-lithium or by potassium starvation; both procedures decreased intracellular potassium by an equivalent amount as adjudged by X-ray microanalysis. We conclude that lithium inhibits HSV DNA synthesis by displacement of potassium from a potassium-dependent biochemical reaction or by other physiological changes brought about by the loss of cellular potassium. The possibility that lithium also directly inhibits a virus replicative event cannot be excluded.

The DNA Binding Domain of Herpes Simplex Virus Type 1 Origin Binding Protein Is a Transdominant Inhibitor of Virus Replication

The origin binding protein (OBP) of herpes simplex virus (HSV) type 1 specifically interacts with two high-affinity sites in each HSV DNA replication origin. The sequence-specific DNA binding activity of OBP maps to the carboxy-terminal one-third of the protein. For a single binding site, recombinantly expressed forms of this DNA binding domain have the same sequence specificity and binding affinity as the full-length OBP. However, unlike the full-length protein, truncated OBP does not bind HSV replication origins in a cooperative manner. To determine if cooperative interactions between DNA-bound OBP molecules are essential for viral DNA replication, the 317-amino-acid carboxy-terminal DNA binding domain of OBP was expressed in chick embryo fibroblasts. Cells were infected with HSV type 1, and viral DNA synthesis and virus production were monitored. We found that cells expressing truncated OBP were severely restricted for virus replication and that HSV DNA synthesis was undetectable. The results demonstrate that the amino-terminal two-thirds of OBP is essential for HSV DNA replication and that the OBP DNA binding domain acts as a transdominant inhibitor of viral DNA replication. The results also suggest that this experimental approach could be used to generate a refined map of essential OBP functions and that the approach may be generally applicable to the analysis of the multifunction HSV DNA replication complex.

Herpes simplex virus-specified DNA polymerase is the target for the antiviral action of 9-(2-phosphonylmethoxyethyl)adenine.

9-(2-Phosphonylmethoxyethyl)adenine (PMEA) is a new antiviral compound with activity against herpes simplex virus (HSV) and retroviruses including human immunodeficiency virus. Although it has been suggested that the anti-HSV action of PMEA is through inhibition of the viral DNA polymerase via the diphosphorylated metabolite of PMEA (PMEApp), no conclusive evidence for this has been presented. We report that in cross-resistance studies, a PMEA-resistant HSV variant (PMEAr-1) was resistant to phosphonoformic acid, a compound which directly inhibits the HSV DNA polymerase. In addition, phosphonoformic acid-resistant HSV variants with defined drug resistance mutations within the HSV DNA polymerase gene were resistant to PMEA. Furthermore, the HSV DNA polymerase purified from PMEAr-1 was resistant to PMEApp in comparison with the enzyme from the parental virus. Moreover, PMEA inhibited HSV DNA synthesis in cell culture. These results provide strong evidence that HSV DNA polymerase is the major target for the anti-viral action of PMEA. Further studies showed that HSV DNA polymerase incorporated PMEApp into DNA in vitro, while the HSV polymerase-associated 3'-5' exonuclease was able to remove the incorporated PMEA. Thus, the inhibition of HSV DNA polymerase by PMEApp appears to involve chain termination after its incorporation into DNA.

Herpes simplex virus DNA synthesis at a preformed replication fork in vitro

Proteins from herpes simplex virus (HSV)-infected cells were used to reconstitute DNA synthesis in vitro on a preformed replication fork. The preformed replication fork consisted of a nicked, double-stranded, circular DNA molecule with a 5' single-strand tail that was noncomplementary to the template. The products of DNA synthesis on this substrate were rolling-circle molecules, as demonstrated by electron microscopy and alkaline agarose gel electrophoresis. The tails contained double-stranded regions, indicating that both leading- and lagging-strand DNA syntheses occurred. Rolling-circle DNA replication was dependent upon HSV DNA polymerase and ATP and was stimulated by a crude fraction containing ICP8 (HSV DNA-binding protein). Similar protein fractions from mock-infected cells were unable to support rolling-circle DNA replication. This in vitro DNA replication system should prove useful in the identification and characterization of the enzymatic activities required at the HSV replication fork.

Inhibition of herpes simplex virus DNA replication by ara-tubercidin

Preliminary studies of the biochemical basis for the antiviral activity of the pyrrolo[2,3- d]pyrimidine nucleoside ara-tubercidin were conducted. Herpes simplex virus DNA synthesis was 3-fold more sensitive to inhibition by ara-tubercidin than was cellular DNA synthesis. Partially purified herpes DNA polymerases were more sensitive to inhibition by ara-tubercidin 5′-triphosphate than were cellular polymerases α and β. Inhibition of viral DNA polymerase was competitive with dATP and noncompetitive with dTTP. The results suggest that the viral DNA polymerase plays a significant role in the antiviral activity of ara-tubercidin.

The effect of triterpenoid compounds on uninfected and herpes simplex virus-infected cells in culture. II. DNA and protein synthesis, polypeptide processing and transport.

The effect of the triterpenoid drugs carbenoxolone sodium (CBX) and cicloxolone sodium (CCX) on DNA and protein synthesis in uninfected and herpes simplex virus (HSV)-infected BHK-21 or Flow 2002 cells has been studied. No consistent effect of 500 microM-CBX or 300 microM-CCX on HSV DNA synthesis was identified. With 300 microM-CCX, some inhibition of cellular DNA synthesis was observed, but this was relatively slight. The restriction enzyme digest profiles of HSV DNA from drug-treated cells appeared normal. The synthesis of several HSV-specified polypeptides was much reduced by treatment with CBX or CCX and the transport of certain proteins between the nuclear and cytoplasmic compartments of infected cells was also affected. CBX or CCX treatment strongly inhibited post-translational glycosylation and sulphation of both host- and HSV-specified proteins, but the phosphorylation of only a few proteins appeared affected. The drugs induced quantitative changes in the synthesis of some BHK cell polypeptides, but these were not considered important. CCX treatment of Flow 2002 cells, however, induced the synthesis of several new polypeptides, some of which had the same apparent molecular weights as identified Flow 2002 cell stress proteins. When treated with concentrations greater than 50 microM-CCX, the plasma membranes of both uninfected and HSV-infected cells became increasingly leaky. The SDS-PAGE polypeptide profile of purified virus particles made in BHK cells treated with 300 microM-CCX differed markedly from that synthesized under drug-free conditions. The greatly reduced amount of infectious virus made in cells treated with 300 microM-CCX was more thermolabile at 42 degrees C than virus produced in the absence of the drug. Our results indicate that the antiviral activity of the triterpenoid drugs is non-specific and operates by interfering with or changing the normal function of cell membranes so that cells, although retaining their viability, can no longer assemble the virus components efficiently into infectious particles. As a consequence, the population of virus particles made is of inferior quality. While we have no evidence that there is also a specific anti-HSV effect, this possibility cannot yet be ruled out.

Inhibition of herpes simplex virus DNA synthesis by pokeweed antiviral protein.

Pokeweed antiviral protein at a concentration of 3 microM inhibited both the synthesis and release of infectious herpes simplex virus type 1 in cell culture by 90 and 99%, respectively. Addition of pokeweed antiviral protein to Vero cell monolayers before virus infection was 10 to 15% more effective in reducing virus yields than was the simultaneous addition of the antiviral protein with virus inoculum. Viral DNA synthesis was inhibited by 90% in cells which had been exposed to the antiviral protein, whereas cellular DNA synthesis was unaffected. No significant inhibition in the synthesis of the majority of viral infected-cell polypeptides was observed early postinfection (7 h), with the exception of infected cell polypeptides 4 and 41, whose syntheses were reduced by 38 and 25%, respectively. At 9 to 21 h postinfection, however, the synthesis of individual infected cell polypeptides was reduced by 48 to greater than 99%.

Selective inhibition of herpesvirus DAN synthesis by foscarnet

The inhibition of cellular and herpesvirus DNA synthesis by phosphonoformate (INN; foscarnet sodium) has been determined after isopycnic separation of cellular and viral DNA in CsCl gradients. The DNA synthesis was determined as the incorporation of ortho[ 32P]phosphate and [ 3H]thymidine into DNA. A 50% inhibition of herpes simplex virus DNA synthesis was observed at 50 μM phosphonoformate. At this concentration cellular DNA synthesis was not inhibited. At 500 μM phosphonoformate more than 95% of the viral DNA synthesis was inhibited, while the cellular DNA synthesis in infected and uninfected cells were inhibited to about 10%. The same results were obtained in both Vero and GMK cells and using either ortho[ 32P]phosphate or [ 3H]thymidine to label the newly synthesized DNA. The 50% inhibitory concentration of phosphonoformate was similar for inhibition of herpes DNA synthesis and plaque reduction.

ChemInform Abstract: STRUCTURE‐ACTIVITY RELATIONSHIPS OF PYRROLEAMIDINE ANTIVIRAL ANTIBIOTICS. 1. MODIFICATIONS OF THE ALKYLAMIDINE SIDE CHAIN

AbstractAuf den im Formelschema skizzierten Wegen werden Analoga von Distamycin A (I) dargestellt.

Herpes simplex virus DNA synthesis in a partially purified soluble extract from infected cells

HEp-2 cells were infected with herpes simplex virus type 1 and extracted with 0.25% Triton X-100 and 0.1 M NaCl. The extract was sedimented on sucrose gradients, and the fractions containing the endogenous DNA polymerizing activity (replication complex) were collected. The properties of the replication complex were partially characterized. Under optimal conditions 375 pmol of dTMP per micrograms of DNA was incorporated, which corresponds to about 50% replication of preexisting viral DNA. The replication complex was shown to contain only DNA of viral origin by its density in CsCl. By using specific assays for DNA polymerases alpha, beta, gamma, and herpes simplex virus, we found that only the viral DNA polymerase copurified with the replication complex.

Structure-activity relationships of pyrroleamidine antiviral antibiotics. 1. Modifications of the alkylamidine side chain

Representatives of three types of side-chain analogues of distamycin A (1) were synthesized. These were tested for cytotoxicity, inhibition of herpes simplex virus (HSV) replication in cultured cells, effects on the synthesis of HSV DNA in isolated nuclei in vitro, as well as on DNA synthesis by purified HSV DNA polymerase. Distamycin A was the most active compound in all three antiviral tests, as well as the most toxic. However, several compounds, in particular the aromatic analogues 15 and 16, showed no toxicity under the experimental conditions used but were still very active in the three antiviral tests.

Oligoribonucleotide initiators for herpes simplex virus DNA synthesis in vivo and in vitro

Replicating herpes simplex virus (HSV) DNA, labeled with [ 3H]thymidine or [ 3H]uridine, was isolated from infected primary rabbit kidney cells. Nascent DNA strands are covalently linked to oligoribonucleotide stretches. The chain length of this RNA segment amounts to approximately 36 nucleotides wich are located at the terminus of the replicating DNA. The extent of RNA initiator synthesis seems to be closely correlated with the rate of HSV-DNA synthesis. The half life of the RNA initiator was estimated as 35 min. Evidence is presented by comparative studies regarding the characteristics of the naturally occurring RNA initiator, that cordycepin (3′-dAdo) is an inhibitor of the synthesis of the RNA initiator: (1) identical maximal chain length of the 3′-dAMP-RNA, (2) identical half-life of the 3′-dAMP-RNA segment, and (3) susceptibility to RNases and alkali. The 3′-dAMP-RNA segment is not covalently linked to HSV-DNA. HSV-Induced DNA polymerases utilizes not only deoxyribooligomers [ d(pA) 8 ] as initiators for the DNA template-dependent DNA polymerization. The initiating activity of both the DNA and the RNA segment is abolished when it carries a 3′-dAMP moiety at its 3′-terminus.

Differential and selective inhibition of cellular and herpes simplex virus DNA synthesis by arabinofuranosyladenine

The influence of 9-β- d-arabinofuranosyladenine (βaraAdo) and of its anomer 9-α- d-arabinofuranosyladenine (αaraAdo) was studied in non-infected cells and cells infected with herpes simplex virus type 1 (HSV-1) and HSV type 2 (HSV-2). αAraAdo is a strong inhibitor of proliferation of non-infected cells. Multiplication of HSV-1 and HSV-2 is not affected at all by αaraAdo, while their growth is strongly inhibited by βaraAdo. αAraAdo exerts no effect on the incorporation of dThd into HSV DNA, but blocks the incorporation into host cell DNA. Its anomer, βaraAdo, affects the incorporation rate of both the viral DNA system and the host cell DNA system (the latter one to a lesser extent). αAraAMP is incorporated into newly synthesized cellular DNA but not into HSV DNA. Enzymic studies relevant that αaraATP has no effect on the HSV DNA polymerase system but a high inhibitory potency in the host cell DNA polymerase α system. The anomeric form, βaraATP, is a sensitive inhibitor of HSV DNA polymerase while the cellular DNA polymerases α and β are more refractory.

Synthesis of Herpes simplex virus DNA in isolated chromatin

Herpes simplex virus DNA synthesis was studied in isolated chromatin (HSV chromatin) of African green monkey kidney (RC-37) cells after HSV type 1 infection. After optimizing the in vitro system, HSV chromatin was shown to synthesize both viral and cellular DNA at ratios identical with those seen in vivo. After 30 min of DNA synthesis in vitro, the DNA products were identical in size to the prelabeled parental DNA. More than 60% of the newly synthesized single-stranded DNA fragments sedimented with a sedimentation constant of greater than 10 S. HSV DNA polymerase was found to be responsible for the synthesis of 80% of all in vitro made viral and most likely also cellular DNA sequences.

Poly(Adenosine Diphosphate Ribose) Synthesis during Herpes Simplex Virus Infection

Immediately after infection of baby hamster kidney cells with herpes simplex virus (HSV), cellular DNA synthesis was blocked, while extensive HSV DNA synthesis began. These dramatic alterations of the control mechanisms for these two DNA synthesizing systems were not accompanied by a change in the poly(adenosine diphosphate ribose) polymerase activity.