Alternative mechanisms for activation of human immunodeficiency virus enhancer in T cells

Curcumae Rhizoma: A botanical drug against infectious diseases

Curcumae Rhizoma is the dry rhizome coming from Curcuma longa L. which grow widely in tropical south and southwest Asia. It has been used to treat conditions such as dermatoses, infections, stress, and depression. Moreover, in China, Curcumae Rhizoma and its active constituents have been made into different pharmaceutical preparations. Growing evidence suggests that these preparations can exert antioxidant, anti-inflammatory, and anti-cancer effects, which may play crucial roles in the treatment of various diseases, including cancer, infectious-, autoimmune-, neurological-, and cardiovascular diseases, as well as diabetes. The anti-infective effect of Curcumae Rhizoma has become a popular field of research around the world, including for the treatment of COVID-19, influenza virus, hepatitis B virus, human immunodeficiency virus, and human papilloma virus, among others. In this paper, the basic characteristics of Curcumae Rhizoma and its active constituents are briefly introduced, and we also give an overview on their applications and mechanisms in infectious diseases.

Human Virus Transcriptional Regulators

Viral genomes encode transcriptional regulators that alter the expression of viral and host genes. Despite an emerging role in human diseases, a thorough annotation of human viral transcriptional regulators (vTRs) is currently lacking, limiting our understanding of their molecular features and functions. Here, we provide a comprehensive catalog of 419 vTRs belonging to 20 different virus families. Using this catalog, we characterize shared and unique cellular genes, proteins, and pathways targeted by particular vTRs and discuss the role of vTRs in human disease pathogenesis. Our study provides a unique and valuable resource for the fields of virology, genomics, and human disease genetics.

"Non-Essential" Proteins of HSV-1 with Essential Roles In Vivo: A Comprehensive Review

Viruses encode for structural proteins that participate in virion formation and include capsid and envelope proteins. In addition, viruses encode for an array of non-structural accessory proteins important for replication, spread, and immune evasion in the host and are often linked to virus pathogenesis. Most virus accessory proteins are non-essential for growth in cell culture because of the simplicity of the infection barriers or because they have roles only during a state of the infection that does not exist in cell cultures (i.e., tissue-specific functions), or finally because host factors in cell culture can complement their absence. For these reasons, the study of most nonessential viral factors is more complex and requires development of suitable cell culture systems and in vivo models. Approximately half of the proteins encoded by the herpes simplex virus 1 (HSV-1) genome have been classified as non-essential. These proteins have essential roles in vivo in counteracting antiviral responses, facilitating the spread of the virus from the sites of initial infection to the peripheral nervous system, where it establishes lifelong reservoirs, virus pathogenesis, and other regulatory roles during infection. Understanding the functions of the non-essential proteins of herpesviruses is important to understand mechanisms of viral pathogenesis but also to harness properties of these viruses for therapeutic purposes. Here, we have provided a comprehensive summary of the functions of HSV-1 non-essential proteins.

Exploitation of a Rapid and Sensitive Assay to Analyse Transactivation of the Human Immunodeficiency Virus type 1 (HIV-1) Long Terminal Repeat

Transregulation of the promoter within the 5′ long terminal repeat (LTR) of the human immunodeficiency virus (HIV) provirus determines the level of replication of HIV in latently, persistently or acutely infected cells. To measure rapidly the degree of transactivation of the HIV-1 LTR by various cellular and viral effectors, stably transformed cell lines containing integrated copies of the HIV LTR promoter (−122 to +80, relative to the major mRNA cap site) linked to the Escherichia coli lac Z gene were prepared by co-selection for pSV2 neo-mediated G418 resistance. One cell clone, RS 3/7, containing about 40 integrated copies of the recombinant LTR- lacZ gene was analysed further. RS 3/7 cells expressed high levels of β-galactosidase in response to co-transfection with plasmids expressing the HIV-1 transactivator, tat, infection with low multiplicities of herpes simplex virus type 1 (HSV-1), transfection with a plasmid expressing the HSV-1 immediate-early (IE) protein, ICPO, and by incubation with medium containing sodium butyrate. β-galactosidase activity was also induced by incubation of RS 3/7 cells with medium containing full length tat polypeptide. The cysteine analogue, D-penicillamine, previously reported as a potent inhibitor of tat-mediated transactivation (Chandra et al., 1988), was of limited efficacy in RS 3/7 cells transfected with tat-expressing plasmids. This cell line will be of value in identifying additional transactivators of the HIV-1 LTR, and in the selection of inhibitors of such effectors.

Infected cell protein 0 functional domains and their coordination in herpes simplex virus replication

Herpes simplex virus 1 (HSV-1) is a ubiquitous human pathogen that establishes latent infection in ganglia neurons. Its unique life cycle requires a balanced “conquer and compromise” strategy to deal with the host anti-viral defenses. One of HSV-1 α (immediate early) gene products, infected cell protein 0 (ICP0), is a multifunctional protein that interacts with and modulates a wide range of cellular defensive pathways. These pathways may locate in different cell compartments, which then migrate or exchange factors upon stimulation, for the purpose of a concerted and effective defense. ICP0 is able to simultaneously attack multiple host pathways by either degrading key restrictive factors or modifying repressive complexes. This is a viral protein that contains an E3 ubiquitin ligase, translocates among different cell compartments and interacts with major defensive complexes. The multiple functional domains of ICP0 can work independently and at the same time coordinate with each other. Dissecting the functional domains of ICP0 and delineating the coordination of these domains will help us understand HSV-1 pathogenicity as well as host defense mechanisms. This article focuses on describing individual ICP0 domains, their biochemical properties and their implication in HSV-1 infection. By putting individual domain functions back into the picture of host anti-viral defense network, this review seeks to elaborate the complex interactions between HSV-1 and its host.

Functional comparison of herpes simplex virus 1 (HSV-1) and HSV-2 ICP27 homologs reveals a role for ICP27 in virion release

Numerous studies have focused on the regulatory functions of ICP27, an immediate-early (IE) protein of herpes simplex virus 1 (HSV-1). However, its homolog in HSV-2, termed ICP27t2, has been little studied. Here, we used two different approaches to functionally compare ICP27t2 and ICP27. In transfection-based assays, ICP27t2 closely resembled ICP27 in its capacity to enhance HSV-1 late gene expression, suppress the splicing of a viral intron, and complement the growth of an HSV-1 ICP27 null mutant. To study ICP27t2 in the context of viral infection, we engineered K2F1, an HSV-1 mutant that encodes ICP27t2 in place of ICP27. In Vero cells, K2F1 replicated with wild-type (WT) kinetics and yields, expressed delayed-early and late proteins normally, and was fully capable of activating several cellular signal transduction pathways that are ICP27 dependent. Thus, we conclude that ICP27t2 and ICP27 are functionally very similar and that ICP27t2 can mediate all ICP27 activities that are required for HSV-1 replication in cell culture. Surprisingly, however, we found that K2F1 forms plaques that are morphologically different from those of WT HSV-1. Investigation of this trait demonstrated that it results from the decreased release of progeny virions into the culture medium. This appears to be due to a reduction in the detachment of K2F1 progeny from the extracellular surface of the infected cell. We identified two HSV-1 ICP27 amino-terminal deletion mutants with a similar release defect. Together, these results demonstrate that ICP27 plays a heretofore-unappreciated role in modulating the efficiency of progeny virion release.

IMPORTANCE

ICP27 is an essential, multifunctional regulatory protein that has a number of critical roles in the HSV-1 life cycle. Although ICP27 homologs are encoded by all known members of the Herpesviridae, previous work with several of these homologs has shown that they cannot substitute for ICP27 in the context of HSV-1-infected cells. Here, we identify ICP27t2 as the first homolog that can efficiently replace ICP27 in HSV-1 infection. Unexpectedly, our results also reveal that the sequence of the ICP27 gene can affect the release of HSV-1 progeny virions from the infected cell. Thus, our comparative study has revealed a novel function for ICP27 in the regulation of virus release.

A review on antibacterial, antiviral, and antifungal activity of curcumin

Curcuma longa L. (Zingiberaceae family) and its polyphenolic compound curcumin have been subjected to a variety of antimicrobial investigations due to extensive traditional uses and low side effects. Antimicrobial activities for curcumin and rhizome extract of C. longa against different bacteria, viruses, fungi, and parasites have been reported. The promising results for antimicrobial activity of curcumin made it a good candidate to enhance the inhibitory effect of existing antimicrobial agents through synergism. Indeed, different investigations have been done to increase the antimicrobial activity of curcumin, including synthesis of different chemical derivatives to increase its water solubility as well ass cell up take of curcumin. This review aims to summarize previous antimicrobial studies of curcumin towards its application in the future studies as a natural antimicrobial agent.

Genetic variation and HIV-associated neurologic disease

HIV-associated neurologic disease continues to be a significant complication in the era of highly active antiretroviral therapy. A substantial subset of the HIV-infected population shows impaired neuropsychological performance as a result of HIV-mediated neuroinflammation and eventual central nervous system (CNS) injury. CNS compartmentalization of HIV, coupled with the evolution of genetically isolated populations in the CNS, is responsible for poor prognosis in patients with AIDS, warranting further investigation and possible additions to the current therapeutic strategy. This chapter reviews key advances in the field of neuropathogenesis and studies that have highlighted how molecular diversity within the HIV genome may impact HIV-associated neurologic disease. We also discuss the possible functional implications of genetic variation within the viral promoter and possibly other regions of the viral genome, especially in the cells of monocyte-macrophage lineage, which are arguably key cellular players in HIV-associated CNS disease.

Immune adaptor ADAP in T cells regulates HIV-1 transcription and cell-cell viral spread via different co-receptors

Background

Immune cell adaptor protein ADAP (adhesion and degranulation-promoting adaptor protein) mediates aspects of T-cell adhesion and proliferation. Despite this, a connection between ADAP and infection by the HIV-1 (human immunodeficiency virus-1) has not been explored.

Results

In this paper, we show for the first time that ADAP and its binding to SLP-76 (SH2 domain-containing leukocyte protein of 76 kDa) regulate HIV-1 infection via two distinct mechanisms and co-receptors. siRNA down-regulation of ADAP, or expression of a mutant that is defective in associating to its binding partner SLP-76 (termed M12), inhibited the propagation of HIV-1 in T-cell lines and primary human T-cells. In one step, ADAP and its binding to SLP-76 were needed for the activation of NF-κB and its transcription of the HIV-1 long terminal repeat (LTR) in cooperation with ligation of co-receptor CD28, but not LFA-1. In a second step, the ADAP-SLP-76 module cooperated with LFA-1 to regulate conjugate formation between T-cells and dendritic cells or other T-cells as well as the development of the virological synapse (VS) and viral spread between immune cells.

Conclusions

These findings indicate that ADAP regulates two steps of HIV-1 infection cooperatively with two distinct receptors, and as such, serves as a new potential target in the blockade of HIV-1 infection.

Mammalian alphaherpesvirus miRNAs

Mammalian alphaherpesviruses are major causes of human and veterinary disease. During productive infection, these viruses exhibit complex and robust patterns of gene expression. These viruses also form latent infections in neurons of sensory ganglia in which productive cycle gene expression is highly repressed. Both modes of infection provide advantageous opportunities for regulation by microRNAs. Thus far, published data regarding microRNAs are available for six mammalian alphaherpesviruses. No microRNAs have yet been detected from varicella zoster virus. The five other viruses-herpes simplex viruses-1 and -2, herpes B virus, bovine herpesvirus-1, and pseudorabies virus-representing both genera of mammalian alphaherpesviruses have been shown to express microRNAs. In this article, we discuss these microRNAs in terms of where they are encoded in the viral genome relative to other viral transcripts; whether they are expressed during productive or latent infection; their potential targets; what little is known about their actual targets and functions during viral infection; and what little is known about the interactions of these viruses with the host microRNA machinery. This article is part of a Special Issue entitled: "MicroRNAs in viral gene regulation".

Identification of an ICP27-responsive element in the coding region of a herpes simplex virus type 1 late gene

During productive herpes simplex virus type 1 (HSV-1) infection, a subset of viral delayed-early (DE) and late (L) genes require the immediate-early (IE) protein ICP27 for their expression. However, the cis-acting regulatory sequences in DE and L genes that mediate their specific induction by ICP27 are unknown. One viral L gene that is highly dependent on ICP27 is that encoding glycoprotein C (gC). We previously demonstrated that this gene is posttranscriptionally transactivated by ICP27 in a plasmid cotransfection assay. Based on our past results, we hypothesized that the gC gene possesses a cis-acting inhibitory sequence and that ICP27 overcomes the effects of this sequence to enable efficient gC expression. To test this model, we systematically deleted sequences from the body of the gC gene and tested the resulting constructs for expression. In so doing, we identified a 258-bp "silencing element" (SE) in the 5' portion of the gC coding region. When present, the SE inhibits gC mRNA accumulation from a transiently transfected gC gene, unless ICP27 is present. Moreover, the SE can be transferred to another HSV-1 gene, where it inhibits mRNA accumulation in the absence of ICP27 and confers high-level expression in the presence of ICP27. Thus, for the first time, an ICP27-responsive sequence has been identified in a physiologically relevant ICP27 target gene. To see if the SE functions during viral infection, we engineered HSV-1 recombinants that lack the SE, either in a wild-type (WT) or ICP27-null genetic background. In an ICP27-null background, deletion of the SE led to ICP27-independent expression of the gC gene, demonstrating that the SE functions during viral infection. Surprisingly, the ICP27-independent gC expression seen with the mutant occurred even in the absence of viral DNA synthesis, indicating that the SE helps to regulate the tight DNA replication-dependent expression of gC.

The transactivating effect of HSV-1 ICP0 is enhanced by its interaction with the PCAF component of histone acetyltransferase

ICP0 is a multifunctional protein that plays diverse roles in herpes simplex virus type 1 (HSV-1) infection. It can promote the lytic replication of HSV-1 and activate a variety of viral or cellular genes when introduced into cells by transfection or infection. However, the exact mechanism of ICP0 action is not fully understood. In the present study, we observed the co-localization of ICP0 and PCAF (P300/CBP-associated factor), a component of histone acetyltransferase (HAT), in the ND10 (nuclear dot 10) nuclear body. We further confirmed the interaction between ICP0 and PCAF via yeast two-hybrid assay, co-immunoprecipitation, and histone acetyltransferase assays. Analysis of the functional significance of this interaction suggested that PCAF improved the ability of ICP0 to activate transcription of viral genes. Using chromatin immunoprecipitation (ChIP) assays, we observed ICP0-enhanced histone acetylation levels in both viral and cellular gene promoters. Our study suggests that ICP0 regulates transcription through specific interaction with PCAF.

15-Deoxy-Delta12,14-prostaglandin J2 inhibits HIV-1 transactivating protein, Tat, through covalent modification

Controlling the HIV/AIDS epidemic remains a major challenge, with approximately 5 million new HIV infections annually. Cyclopentenone prostaglandins (CyPG), such as 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)), are arachidonic acid-derived endogenous electrophiles that possess anti-HIV activity by an unknown mechanism. Given that the reactive alpha,beta-unsaturated ketone in the cyclopentenone ring of 15d-PGJ(2) covalently modifies key Cys thiols in select proteins, we hypothesized that 15d-PGJ(2) inhibits HIV transcription and replication by targeting Cys thiols in HIV-1 Tat. Tat is a potent transactivator of viral gene expression required for HIV transcriptional elongation and replication. Our studies indicate that 15d-PGJ(2) treatment of cells inhibits Tat-dependent transcription and replication of HIV-1, while 9,10-dihydro-15d-PGJ(2), PGE(2), PGF(2alpha), or PGD(2) that lack the reactive alpha,beta-unsaturated ketone were ineffective. The inhibition of Tat activity by 15d-PGJ(2) was dose-dependent, with an IC(50) of 1.2 microM and independent of NF-kappaB pathway. Furthermore, using a biotinylated derivative of 15d-PGJ(2), we demonstrate that 15d-PGJ(2) modifies free Cys-thiols in Tat to form covalent Michael adducts and that the interaction was further increased on reduction of Tat. 15d-PGJ(2)-modified Tat was unable to transactivate the HIV long terminal repeat in U937 human macrophages. These data demonstrate that Tat acts as a molecular target of CyPG leading to the inhibition of transcription and also suggest a novel therapeutic approach to complement current antiretroviral strategies for HIV/AIDS.

Cell type-specific induction and inhibition of apoptosis by Herpes Simplex virus type 2 ICP10

Herpes simplex virus (HSV) inhibits apoptosis induced by external stimuli in epithelial cells. In contrast, apoptosis is the primary outcome in HSV-infected lymphocytes. Here, we show that HSV type 2 (HSV-2) gene expression appears to be necessary for the induction of apoptosis in Jurkat cells, a T-cell leukemia line. HSV-2 ICP10 gene expression is sufficient to induce apoptosis in Jurkat cells, while its expression protects epithelial HEp-2 cells from apoptosis triggered by cycloheximide and tumor necrosis factor alpha. Thus, the effect of HSV-2 gene expression on the cellular apoptotic pathway appears to depend on the specific cell type.

Herpes simplex virus ICP0 promotes both histone removal and acetylation on viral DNA during lytic infection

During lytic infection, the genome of herpes simplex virus 1 (HSV-1) is associated with limited levels of histones but does not form a regular repeating nucleosomal structure. However, the previous observation that chromatin remodeling factors are recruited into viral replication compartments indicates that chromatin remodeling plays a role in HSV-1 gene expression and DNA replication. In this study we demonstrate the presence of histone H3 on HSV-1 DNA early in infection at levels equivalent to those found on a cellular gene. The proportion of viral DNA associated with histone H3 decreases at later times postinfection, independently of either viral DNA replication or transcription. We demonstrate that an immediate-early protein, infected cell protein 0 (ICP0), is required for both a reduction in the proportion of HSV-1 DNA associating with histone H3 and an increase in histone acetylation. This study provides evidence that ICP0 directly alters the chromatin structure of the HSV-1 genome during lytic infection, and this system will serve as a useful model for the reduction of histone load in higher eukaryotes.

Chromatin control of herpes simplex virus lytic and latent infection

Herpes simplex viruses (HSV) can undergo a lytic infection in epithelial cells and a latent infection in sensory neurons. During latency the virus persists until reactivation, which leads to recurrent productive infection and transmission to a new host. How does HSV undergo such different types of infection in different cell types? Recent research indicates that regulation of the assembly of chromatin on HSV DNA underlies the lytic versus latent decision of HSV. We propose a model for the decision to undergo a lytic or a latent infection in which HSV encodes gene products that modulate chromatin structure towards either euchromatin or heterochromatin, and we discuss the implications of this model for the development of therapeutics for HSV infections.

Herpes simplex virus type 1 immediate-early protein ICP27 is required for efficient incorporation of ICP0 and ICP4 into virions

Early in infection, herpes simplex virus type 1 (HSV-1) immediate-early (IE) proteins ICP0 and ICP4 localize to the nucleus, where they stimulate viral transcription. Later in infection, ICP0 and to a lesser extent ICP4 accumulate in the cytoplasm, but their biological role there is unknown. Previously, it was shown that the cytoplasmic localization of ICP0/4 requires the multifunctional IE protein ICP27, which is itself an activator of viral gene expression. Here, we identify a viral ICP27 mutant, d3-4, which is unable to efficiently localize ICP0 and ICP4 to the cytoplasm but which otherwise resembles wild-type HSV-1 in its growth and viral gene expression phenotypes. These results genetically separate the function of ICP27 that affects ICP0/4 localization from its other functions, which affect viral growth and gene expression. As both ICP0 and ICP4 are known to be minor virion components, we used d3-4 to test the hypothesis that the cytoplasmic localization of these proteins is required for their incorporation into viral particles. Consistent with this conjecture, d3-4 virions were found to lack ICP0 in their tegument and to have greatly reduced levels of ICP4. Thus, the cytoplasmic localization of ICP0 and ICP4 appears to be a prerequisite for the assembly of these important transcriptional regulatory proteins into viral particles. Furthermore, our results show that ICP27 plays a previously unrecognized role in determining the composition of HSV-1 virions.

Herpes simplex virus-infected cell protein 0 blocks the silencing of viral DNA by dissociating histone deacetylases from the CoREST-REST complex

A preeminent phenotype of the infected cell protein 0 (ICP0) of herpes simplex virus 1 (HSV-1) is that it acts as a promiscuous transactivator. In most cell lines exposed to DeltaICP0 mutant virus at low ratios of virus per cell infection, alpha genes are expressed but the transition to beta and gamma gene expression does not ensue, but can be enhanced by inhibitors of histone deacetylases (HDACs). Earlier studies have shown that ICP0 interacts with CoREST and displaces HDAC1 from the CoREST-REST-HDAC1/2 complex. HDAC1 and CoREST are then independently translocated to the cytoplasm. Here, we test the hypothesis that ICP0 blocks the silencing of HSV DNA by displacing HDAC1 from the CoREST-REST complex. Specifically, first, mapping studies led us to construct a truncated CoREST (CoREST(146-482)) that in transfected cells displaced HDAC1 from the CoREST-REST complex. Second, we constructed two viruses. In BACs encoding the entire HSV-1, we replaced the gene encoding ICP0 with AmpR to yield a DeltaICP0 mutant R8501. We also replaced ICP0 with CoREST(146-482) to yield recombinant R8502. The yield of R8502 mutant virus in Vero, HEp-2, and human embryonic lung cells exposed to 0.1 pfu of virus per cell was 100-, 10-, and 10-fold higher, respectively, than those of R8501 mutant virus. In Vero cells, the yield of R8502 was identical with that of wild-type virus. We conclude that CoREST(146-482) functionally replaced ICP0 and that, by extension, ICP0 acts to block the silencing of viral DNA by displacing HDAC1/2 from the CoREST-REST complex.

Modulation of NFAT-dependent gene expression by the RhoA signaling pathway in T cells

We have reported previously that p115Rho guanine nucleotide exchange factor, its upstream activator Galpha13, and its effector RhoA are able to inhibit HIV-1 replication. Here, we show that RhoA is able to inhibit HIV-1 gene expression through the NFAT-binding site in the HIV long-terminal repeat. Constitutively active NFAT counteracts the inhibitory activity of RhoA, and inhibition of NFAT activation also inhibits HIV-1 gene expression. We have shown further that RhoA inhibits NFAT-dependent transcription and IL-2 production in human T cells. RhoA does not inhibit nuclear localization of NFAT but rather, inhibits its transcriptional activity. In addition, RhoA decreases the level of acetylated histone H3, but not NFAT occupancy, at the IL-2 promoter. These data suggest that activation of RhoA can modulate IL-2 gene expression by inhibiting the transcriptional activity of NFAT and chromatin structure at the IL-2 promoter during T cell activation.

"UnPAKing" human immunodeficiency virus (HIV) replication: using small interfering RNA screening to identify novel cofactors and elucidate the role of group I PAKs in HIV infection

In order to identify novel proviral host factors involved in human immunodeficiency virus (HIV) infection, we performed a screen of a small interfering RNA (siRNA) library targeting 5,000 genes with the highest potential for being targets for therapeutics. Many siRNAs in the library against known host factors, such as TSG101, furin, and CXCR4, were identified as inhibitors by the screen and thus served as internal validation. In addition, many novel factors whose knockdown inhibited infection were identified, including Pak3, a member of the serine/threonine group I PAK kinases. The HIV accessory factor Nef has been shown to associate with a PAK kinase, leading to enhanced viral production; however, the exact identity of the kinase has remained controversial. Prompted by the Pak3 screen hit, we further investigated the involvement of group I PAK kinases in HIV using siRNA. Contrary to the current literature, Pak1 depletion strongly inhibited HIV infection in multiple cell systems and decreased levels of integrated provirus, while Pak2 depletion showed no effect. Overexpression of a constitutively active Pak1 mutant also enhanced HIV infection, further supporting its role as the dominant PAK involved.

Recruitment of activated IRF-3 and CBP/p300 to herpes simplex virus ICP0 nuclear foci: Potential role in blocking IFN-beta induction

The host innate response to viral infection includes the production of interferons, which is dependent on the coordinated activity of multiple transcription factors. Herpes simplex virus 1 (HSV-1) has been shown to block efficient interferon expression by multiple mechanisms. We and others have demonstrated that HSV-1 can inhibit the transcription of genes promoted by interferon regulatory factor-3 (IRF-3), including interferon beta (IFN-beta), and that the immediate-early ICP0 protein is sufficient for this function. However, the exact mechanism by which ICP0 blocks IRF-3 activity has yet to be determined. Unlike some other viral proteins that inhibit IRF-3 activity, ICP0 does not appear to affect phosphorylation and dimerization of IRF-3. Here, we show that a portion of activated IRF-3 co-localizes with nuclear foci containing ICP0 at early times after virus infection. Co-localization to ICP0-containing foci is also seen with the IRF-3-binding partners and transcriptional co-activators, CBP and p300. In addition, using immunoprecipitation of infected cell lysates, we can immunoprecipitate a complex containing ICP0, IRF-3, and CBP. Thus we hypothesize that ICP0 recruits activated IRF-3 and CBP/p300 to nuclear structures, away from the host chromatin. This leads to the inactivation and accelerated degradation of IRF-3, resulting in reduced transcription of IFN-beta and an inhibition of the host response. Therefore, ICP0 provides an example of how viruses can block IFN-beta induction by sequestration of important transcription factors essential for the host response.

Antiviral Activity of Proteasome Inhibitors in Herpes Simplex Virus-1 Infection: Role of Nuclear Factor-κB

Background

Herpes simplex virus type 1 (HSV-1) is a potent inducer of nuclear factor-κB (NF-κB), a cellular transcription factor with a crucial role in promoting inflammation and controlling cell proliferation and survival.

Objectives

On the basis of the recent demonstration that HSV-1-induced NF-κB is actively recruited to κB-binding sites in the HSV-1 infected-cell protein 0 (ICP0) promoter enhancing viral transcription and replication, we investigated the effect of proteasome inhibitors MG132, MG115 and epoxomicin, which block NF-κB function by preventing the degradation of the inhibitory proteins IκBα, on HSV-1-induced NF-κB activation and viral replication.

Methods

Antiviral activity of proteasome inhibitors was analysed in HSV-1-infected HEp2 cells by determining infective virus titres by CPE50%, viral RNA synthesis by RT-PCR, and viral protein synthesis by immunoblot analysis or immunofluorescence. ICP0 transcription was studied in transient transfection experiments using the ICP0 promoter-luciferase IE1-Luc construct. IκBα degradation and NF-κB activity were determined by immunoblot analysis and EMSA, respectively.

Results

Proteasome inhibitors were found to prevent HSV-1-induced NF-κB activation in the early phase of infection. Block of virus-induced NF-κB activation resulted in inhibiting HSV-1 ICP0 gene expression, in decreasing the level of immediate-early and late viral proteins, and ultimately in greatly suppressing viral replication. The antiviral effect was lost if treatment was started after NF-κB activation, and appeared to be independent of the HSV-1-induced activation of the JNK pathway.

Conclusions

Proteasome inhibitors possess NF-κB-dependent antiherpetic activity. The results described further identify the IKK/NF-κB pathway as a suitable target for novel antiherpetic drugs.

ICP27-dependent resistance of herpes simplex virus type 1 to leptomycin B is associated with enhanced nuclear localization of ICP4 and ICP0

It was previously shown that herpes simplex virus type 1 (HSV-1) is sensitive to leptomycin B (LMB), an inhibitor of nuclear export factor CRM1, and that a single methionine to threonine change at residue 50 (M50T) of viral immediate-early (IE) protein ICP27 can confer LMB resistance. In this work, we show that deletion of residues 21-63 from ICP27 can also confer LMB resistance. We further show that neither the M50T mutation nor the presence of LMB affects the nuclear shuttling activity of ICP27, suggesting that another function of ICP27 determines LMB resistance. A possible clue to this function emerged when it was discovered that LMB treatment of HSV-1-infected cells dramatically enhances the cytoplasmic accumulation of two other IE proteins, ICP0 and ICP4. This effect is completely dependent on ICP27 and is reversed in cells infected with LMB-resistant mutants. Moreover, LMB-resistant mutations in ICP27 enhance the nuclear localization of ICP0 and ICP4 even in the absence of LMB, and this effect can be discerned in transfected cells. Thus, the same amino (N)-terminal region of ICP27 that determines sensitivity to LMB also enhances ICP27's previously documented ability to promote the cytoplasmic accumulation of ICP4 and ICP0. We speculate that ICP27's effects on ICP4 and ICP0 may contribute to HSV-1 LMB sensitivity.

Reciprocal transactivation between HIV-1 and other human viruses

A variety of rare clinical syndromes are seen with strikingly increased prevalence in HIV-1-infected individuals, many with underlying viral etiologies. The emergence of these diseases in AIDS reflects a reduction in the ability of the immune system to mount an adequate defense against viruses in general due to the damage inflicted to the immune system by HIV-1 infection. However, in many cases, it has been found that HIV-1 can enhance the level of expression and hence the life cycle of other viruses independently of immunosuppression through specific interactions with the viruses. This can occur either directly by HIV-1 proteins such as Tat enhancing the activity of heterologous viral promoters, and/or indirectly by HIV-1 inducing the expression of cytokines and activation of their downstream signaling that eventually promotes the multiplication of the other virus. In a reciprocal manner, the effects of other viruses can enhance the pathogenicity of HIV-1 infection in individuals with AIDS through stimulation of the HIV-1 promoter activity and genome expression. The purpose of this review is to examine the cross-interactions between these viruses and HIV-1.

Cellular stress rather than stage of the cell cycle enhances the replication and plating efficiencies of herpes simplex virus type 1 ICP0- viruses

This lab reported previously that the plating efficiency of a herpes simplex virus type 1 ICP0-null mutant was enhanced upon release from an isoleucine block which synchronizes cells to G1 phase (W. Cai and P. A. Schaffer, J. Virol. 65:4078-4090, 1991). Peak plating efficiency occurred as cells cycled out of G1 and into S phase, suggesting that the enhanced plating efficiency was due to cellular activities present in late G1/early S phase. We have found, however, that the enhanced plating efficiency did not occur when cells were synchronized by alternative methods. We now report that the plating efficiency of ICP0- viruses is not enhanced at a particular stage of the cell cycle but rather is enhanced by specific cellular stresses. Both the plating and replication efficiencies of ICP0- viruses were enhanced as much as 25-fold to levels similar to that of wild-type virus when monolayers were heat shocked prior to infection. In addition to heat shock, UV-C irradiation but not cold shock of monolayers prior to infection resulted in enhanced plating efficiency. We further report that the effect of cellular stress is transient and that cell density rather than age of the monolayers is the primary determinant of ICP0- virus plating efficiency. As both cell stress and ICP0 are required for efficient reactivation from latency, the identification of cellular activities that complement ICP0- viruses may lead to the identification of cellular activities that are important for reactivation from neuronal latency.

Transactivation of a viral target gene by herpes simplex virus ICP27 is posttranscriptional and does not require the endogenous promoter or polyadenylation site

ICP27 is an essential herpes simplex virus type 1 (HSV-1) immediate-early protein that stimulates viral mRNA expression from many viral delayed-early and late genes during infection. One HSV-1 late gene which is highly dependent on ICP27 during infection is that encoding the glycoprotein C (gC). Here we report that the gC gene is specifically transactivated by ICP27 in transfected Vero cells. Using various gC plasmid constructs, we show that ICP27's stimulatory effects are independent of the gC gene's endogenous promoter and polyadenylation site. This suggests that ICP27-responsive elements lie in the transcribed body of the gC gene. We also show that transactivation of the gC gene by ICP27 is independent of other viral proteins, as ICP27 alone can transactivate the gC gene when its transcription is mediated by the human cytomegalovirus immediate-early gene promoter. However, when gC gene expression is driven by its endogenous promoter, the stimulatory effect of ICP27 requires additional transactivators. To explore the level at which ICP27 transactivates the gC gene, we established stably transfected Vero cell lines that have integrated copies of the gC gene under control of the cytomegalovirus immediate-early gene promoter. These gC genes are not constitutively expressed but can be efficiently induced by HSV-1 infection. Using nuclear run-on transcription assays, we show that transcriptional induction of the stably transfected genes is ICP27 independent. In contrast, accumulation of gC mRNA is very highly dependent on ICP27. Together, these results demonstrate that ICP27 posttranscriptionally activates mRNA expression from a biologically relevant viral target gene.

Herpesvirus quiescence in neuronal cells. V: forskolin-responsiveness of the herpes simplex virus type 1 alpha0 promoter and contribution of the putative cAMP response element

The herpes simplex virus (HSV)-1 alpha0 promoter contains a putative cAMP response element (CRE) located at positions -68 to -60 with respect to the initiation of transcription. In this report, the authors examined the functionality of this element using (1) luciferase reporter gene assays in nerve growth factor-differentiated (ND)-PC12 cells and (2) virus-induced activation from quiescently infected (QIF)-PC12 cells. The putative alpha0 CRE was completely eliminated by digestion with the restriction enzyme Tsp45I followed by mung bean nuclease treatment. The mutated region was verified by DNA sequencing and was inserted into the alpha0-luciferase reporter plasmid (pRDalpha0-LUC) creating (pRDalpha0deltaCRE-LUC), and into the HSV-1 genome of strain 17(+)(alpha0deltaCRE). Insertion into both copies of the alpha0 promoter was verified by Southern blot analysis. ND-PC12 cells transfected with pRDalpha0-LUC and pRDalpha0deltaCRE-LUC plasmids responded similarly to forskolin (50 microM), with approximately 250% increases in luciferase activity compared to mock-treated cultures as measured 3 days following treatment. When QIF-PC12 cultures established with HSV-1 strain 17(+) and alpha0deltaCRE were treated with forskolin (50 microM) 17 days post infection, virus was detected in 9/24 (37.5%) and 13/24 (54.2%) of induced cultures by day 8 post treatment, respectively. In contrast, virus was detected in 0/23 and 1/24 (4.2%) of mock-treated cultures by day 8 post treatment for wild-type and mutant viruses, respectively. These findings indicate that the alpha0 promoter is forskolin responsive, the purported CRE of the alpha0 promoter does not confer forskolin responsiveness in ND-PC12 cells, and this element is not required for reactivation of HSV-1 from QIF-PC12 cells.

HIV, 'an evolving species'. Roles of cellular activation and co-infections

Each small variation of the genome of a species can be preserved if it is useful for the survival of the species in a given environment. Within this framework, the finality of the biological cycle of HIV consists in a search for harmony (biological coherence) with man, which is to say a stable condition. Cellular activation appears to be the strategy developed by HIV in order to achieve this coherence. The price of this strategy is the AIDS. The first contact between HIV and immune system appears to determine the subsequent clinical outcome and the future of HIV. Lymphocytic activation varies during the course of the vital cycle of HIV. For each individual, this lymphocytic activation depends on both the HLA repertoire acquired during thymic ontogenesis and the antigenic experience before and after HIV infection. Thus intercurrent infections alter the immune condition of the organism and influence the outcome of HIV. We described a synthetic analysis of the effects of HIV on the surface protein expression and the cellular activation pathways which should provide insights in the evolutionary relationship between HIV and man and should permit to do a more physiological therapeutic approach.

Activation of I kappa b kinase by herpes simplex virus type 1. A novel target for anti-herpetic therapy

Herpes simplex viruses (HSV) are ubiquitous pathogens causing a variety of diseases ranging from mild illness to severe life-threatening infections. HSV utilize cellular signaling pathways and transcription factors to promote their replication. Here we report that HSV type 1 (HSV-1) induces persistent activation of transcription factor NF-kappa B, a critical regulator of genes involved in inflammation, by activating the I kappa B kinase (IKK) in the early phase of infection. Activated NF-kappa B enhances HSV-1 gene expression. HSV-1-induced NF-kappa B activation is dependent on viral early protein synthesis and is not blocked by the anti-herpetic drug acyclovir. IKK inhibition by the anti-inflammatory cyclopentenone prostaglandin A(1) blocks HSV-1 gene expression and reduces virus yield by more than 3000-fold. The results identify IKK as a potential target for anti-herpetic drugs and suggest that cyclopentenone prostaglandins or their derivatives could be used in the treatment of HSV infection.

Poly(ADP-ribose) polymerase-1 is required for efficient HIV-1 integration

Poly(ADP-ribose) polymerase-1 (PARP-1; EC ) is an abundant nuclear enzyme, activated by DNA strand breaks to attach up to 200 ADP-ribose groups to nuclear proteins. As retroviral infection requires integrase-catalyzed DNA strand breaks, we examined infection of pseudotyped HIV type I in fibroblasts from mice with a targeted deletion of PARP-1. Viral infection is almost totally abolished in PARP-1 knockout fibroblasts. This protection from infection reflects prevention of viral integration into the host genome. These findings suggest a potential for PARP inhibitors in therapy of HIV type I infection.

GLI-2 modulates retroviral gene expression

GLI proteins are involved in the development of mice, humans, zebrafish, Caenorhabditis elegans, Xenopus, and Drosophila. While these zinc finger-containing proteins bind to TG-rich promoter elements and are known to regulate gene expression in C. elegans and Drosophila, mechanistic understanding of how regulation is mediated through naturally occurring transcriptional promoters is lacking. One isoform of human GLI-2 appears to be identical to a factor previously called Tax helper protein (THP), thus named due to its ability to interact with a TG-rich element in the human T-lymphotropic virus type 1 (HTLV-1) enhancer thought to mediate transcriptional stimulation by the Tax protein of HTLV-1. We now demonstrate that, working through its TG-rich binding site and adjacent elements, GLI-2/THP actually suppresses gene expression driven by the HTLV-1 promoter. GLI-2/THP has no effect on the HTLV-2 promoter, activates expression from the promoters of human immunodeficiency virus types 1 and (HIV-1 and -2), and stimulates HIV-1 replication. Both effective suppression and activation of gene expression and viral replication require the first of the five zinc fingers, which is not necessary for DNA binding, to be intact. Thus, not only can GLI-2/THP either activate or suppress gene expression, depending on the promoter, but the same domain (first zinc finger) mediates both effects. These findings suggest a role for GLI-2 in retroviral gene regulation and shed further light on the mechanisms by which GLI proteins regulate naturally occurring promoters.

Human GLI-2 is a tat activation response element-independent Tat cofactor

Zinc finger-containing GLI proteins are involved in the development of Caenorhabditis elegans, Xenopus, Drosophila, zebrafish, mice, and humans. In this study, we show that an isoform of human GLI-2 strongly synergizes with the Tat transactivating proteins of human immunodeficiency virus types 1 and 2 (HIV-1 and -2) and markedly stimulates viral replication. GLI-2 also synergizes with the previously described Tat cofactor cyclin T1 to stimulate Tat function. Surprisingly, GLI-2/Tat synergy is not dependent on either a typical GLI DNA binding site or an intact Tat activation response element but does require an intact TATA box. Thus, GLI-2/Tat synergy results from a mechanism of action which is novel both for a GLI protein and for a Tat cofactor. These findings link the GLI family of transcriptional and developmental regulatory proteins to Tat function and HIV replication.

Processing of alpha-globin and ICP0 mRNA in cells infected with herpes simplex virus type 1 ICP27 mutants

Herpes simplex virus (HSV) ICP27 is an essential and multifunctional regulator of viral gene expression that modulates RNA splicing, polyadenylation, and nuclear export. We have previously reported that ICP27 causes the cytoplasmic accumulation of unspliced alpha-globin pre-mRNA. Here we examined the effects of a series of ICP27 mutations that alter important functional regions of the protein on the processing and nuclear transport of alpha-globin and HSV ICP0 RNA. The results demonstrate that ICP27 mutants that are impaired for growth in noncomplementing cells, including mutants in the N- and C-terminal regions, are defective in the accumulation of alpha-globin pre-mRNA. Unexpectedly, several mutants that are competent to repress the expression of reporter genes in transient transfection assays failed to accumulate unspliced RNA, implying that different mechanisms are responsible for transrepression and pre-mRNA accumulation. Several mutants caused a marked increase in the length and heterogeneity of the alpha-globin mRNA poly(A) tail, suggesting that ICP27 may directly or indirectly affect the regulation of poly(A) polymerase. ICP27 was also required for the accumulation of multiple ICP0 intron-bearing transcripts, but this effect displayed a mutational sensitivity profile different from that of accumulation of unspliced alpha-globin RNA. Moreover, unlike spliced and unspliced alpha-globin RNAs, which were efficiently exported to the cytoplasm, spliced and intron-containing ICP0 transcripts were predominantly nuclear in localization, and ICP27 was not required for nuclear retention of the spliced message. We propose that these transcript- and ICP27 allele-specific differences may be explained by the presence of a strong cis-acting ICP27 response element in the alpha-globin transcript.

Thiol homeostasis and supplements in physical exercise

Thiols are a class of organic sulfur derivatives (mercaptans) characterized by the presence of sulfhydryl residues. In biological systems, thiols have numerous functions, including a central role in coordinating the antioxidant defense network. Physical exercise may induce oxidative stress. In humans, a consistent marker of exercise-induced oxidative stress is blood glutathione oxidation. Physical training programs have specific effects on tissue glutathione metabolism that depend on the work program and the type of tissue. Experimental studies show that glutathione metabolism in several tissues sensitively responds to an exhaustive bout of exercise. Study of glutathione-deficient animals clearly indicates the central importance of having adequate tissue glutathione to protect against exercise-induced oxidative stress. Among the various thiol supplements studied, N-acetyl-L-cysteine and alpha-lipoic acid hold the most promise. These agents may have antioxidant effects at the biochemical level but are also known to influence redox-sensitive cell signaling.

The TATA motif specifies the differential activation of minimal promoters by varicella zoster virus immediate-early regulatory protein IE62

The immediate-early IE62 protein of varicella zoster virus is an acidic transcriptional activator capable of up-regulating many viral and cellular promoters with varying efficiencies. We demonstrate that, in the context of a minimal promoter, a TATA element is both sufficient and essential for IE62-mediated transcriptional activation. Differential levels of activation by IE62 in this context were conferred by a panel of naturally occurring sequence variations within the TATA motif itself. TATA motif-specific, differential induction was not obtained when the IE62 acidic activation domain was targeted as a GAL4 fusion protein to the same panel. The prototype acidic transactivator, VP16 of herpes simplex virus, failed to discriminate between these different TATA motifs when they were placed into an appropriate responsive promoter context. Nonetheless, a chimeric IE62 polypeptide substituted with the VP16 activation domain retained the ability to differentially modulate minimal promoters with various TATA motifs. Taken together with its binding to TATA box-binding protein (TBP) and transcription factor IIB in vitro, we suggest that IE62 has the unusual ability to achieve differential levels of transcriptional activation through different TATA motifs, which may be accomplished either directly or indirectly by recognizing conformational variations in DNA-bound TBP, TBP-transcription factor IIA/B, or TBP-TATA-associated factor complexes.

Sequence-specific inhibition of a transcription factor by circular dumbbell DNA oligonucleotides

The inhibition of specific transcription regulatory proteins is a new approach to control gene expression. The transcriptional activities of DNA-binding proteins can be inhibited by the use of double-stranded oligonucleotides that compete for the binding to their specific target sequences in promoters and enhancers. We used nicked (NDODN-kappaB) and circular (CDODN-kappaB) dumbbell DNA oligonucleotides containing a NF-kappaB binding site to analyze the inhibition of the NF-kappaB-dependent activation of the human immunodeficiency virus type-1 (HIV-1) enhancer. The dumbbell DNA oligonucleotides are stable, short segments of double-stranded DNA with closed nucleotide loops on each end, which confer resistance to exonucleases. The dumbbell and other oligonucleotides (decoys) with the NF-kappaB sequence were found to compete with the native strand for NF-kappaB binding. The circular dumbbell and double-stranded phosphorothioate oligonucleotides competed with the native strand for binding to the NF-kappaB binding proteins, while the nicked NF-kappaB dumbbell was a less effective competitor. In Jurkat T-cells, the dumbbell and other oligonucleotides were tested for their ability to block the activation of the plasmid HIV-NL4-3 Luc. The CDODN-kappaB strongly inhibits the specific transcriptional regulatory proteins, as compared with the NDODN-kappaB and the double stranded phosphodiester oligonucleotides. On the other hand, the double stranded phosphorothioate oligonucleotides could also block this activation, but the effect was non-specific. The circular (CDODN) dumbbell oligonucleotides may efficiently compete for the binding of specific transcription factors within cells, thus providing anti-HIV-1 or other therapeutic effects.

Perturbation of cell cycle progression and cellular gene expression as a function of herpes simplex virus ICP0

Herpes simplex virus type 1 is capable of inhibiting host cell DNA synthesis following lytic infection. However, the mechanism and nature of potential effects on cell cycle progression have not been described. In this report, we characterize the dysregulation of the cell cycle following infection with the replication-incompetent virus d106, where immediate-early gene expression is restricted to infected-cell polypeptide 0 (ICP0) and the expression of all other viral genes is dramatically reduced or is not observed. Infection with d106 resulted in the accumulation of cells in both the G(1)/S and G(2)/M compartments, consistent with cell cycle arrest at both checkpoints. The isogenic variant d109, which does not express any viral proteins, failed to induce this phenotype, suggesting that the expression of ICP0 is crucial for cell cycle arrest. Analysis of global cellular gene expression patterns following infection with d106 and d109 revealed that a relatively small subset of cellular genes were induced as a consequence of ICP0 expression. A number of these genes induced in the presence of ICP0 are classically considered p53-responsive genes, including p21, gadd45, and mdm-2. However, infection with d106 of cells with both alleles of p53 deleted resulted in the same cell cycle arrest phenotype and similar cellular gene expression patterns, suggesting that the expression of ICP0 results in cell cycle arrest potentially via p53-dependent and p53-independent mechanisms. In addition, it was found that the effects of infection with d106 on viral and cellular gene expression were similar to the effects observed following treatment of cells with the histone deacetylase inhibitor trichostatin A.

Human immunodeficiency virus type 1 tat protein activates transcription factor NF-kappaB through the cellular interferon-inducible, double-stranded RNA-dependent protein kinase, PKR

The transactivator protein of human immunodeficiency virus type 1 (HIV-1) (Tat) is a powerful activator of nuclear factor-kappaB (NF-kappaB), acting through degradation of the inhibitor IkappaB-alpha (F. Demarchi, F. d'Adda di Fagagna, A. Falaschi, and M. Giacca, J. Virol. 70:4427-4437, 1996). Here, we show that this activity of Tat requires the function of the cellular interferon-inducible protein kinase PKR. Tat-mediated NF-kappaB activation and transcriptional induction of the HIV-1 long terminal repeat were impaired in murine cells in which the PKR gene was knocked out. Both functions were restored by cotransfection of Tat with the cDNA for PKR. Expression of a dominant-negative mutant of PKR specifically reduced the levels of Tat transactivation in different human cell types. Activation of NF-kappaB by Tat required integrity of the basic domain of Tat; previous studies have indicated that this domain is necessary for specific Tat-PKR interaction.

Dual activity of pyrrolidine dithiocarbamate on kappa B-dependent gene expression in U937 cells: I. Regulation by the phorbol ester TPA

Pyrrolidine dithiocarbamate (PDTC) has been widely used as an inhibitor of the nuclear factor-kappa B, (NF-kappa B) signalling pathway. Here, we show that kappa B-dependent reporter gene expression induced by low concentrations of 12-O-tetradecanoylphorbol-13-acetate (TPA) is potentiated by PDTC in the human pro-monocytic U937 cell line. The stimulatory effect of PDTC on kappa B-dependent gene expression was shown with a 4 x kappa B chloramphenicol acetyltransferase construct and required an intact kappa B element in the human immunodeficiency virus long terminal repeat (HIV-1 LTR). Unexpectedly, an HIV-1 LTR construct with a mutation of the activator protein 2 (AP-2) binding site located between the two kappa B elements was unresponsive to the stimulatory effect of PDTC with TPA. The stimulation or inhibition of kappa B-dependent gene expression was dependent on PDTC pre-treatment and the concentration of TPA. No stimulatory effect on HIV-1 LTR activity was observed with the metal chelator dipyridyl or the anti-oxidant N-acetyl-L-cysteine. These results are consistent with the hypothesis that PDTC treatment potentiated kappa B-dependent gene expression in a manner dependent on the concentration of TPA.

A sensitive and versatile bioluminescence bioassay for HIV type 1 based on adenoviral vectors

The construction and characterization of a versatile bioassay for the quantification of HIV-1 viral infection and HIV-1 Tat protein activity based on recombinant adenoviral vectors carrying an HIV LTR-driven luciferase reporter gene is described. The assay system consists of a set of two adeno-reporter vectors, one of which is responsive to HIV-1 Tat protein activity, and the second of which is not, by virtue of a deletion of the TAR site within the HIV LTR. This configuration of the reporter genes allows one to distinguish Tat-specific activation from Tat-non-specific HIV LTR-mediated gene expression. The adenoviral HIV LTR-mediated luciferase gene expression is highly responsive to Tat and increases linearly with increasing levels of HIV-1 infection, reaching levels of between 3- and 1000-fold induction. The adeno-reporter viruses can be utilized to detect Tat activity and HIV-1 infection in a wide range of cell types, including 293, CEM, HUT-78, Jurkat, and HeLa-derived cell lines. The resulting bioassay is convenient, sensitive, and readily adaptable to automated procedures. These characteristics of the adeno-reporter assay make it a valuable reagent for studies of HIV infection and for analysis of HIV-inhibitory agents.

Pseudorabies virus early protein 0 trans-activates the TATA-associated promoter by stimulating the transcription initiation

Pseudorabies virus (PRV) early protein 0 (EP0) is a transactivator containing a RING finger domain. To assess the transactivation mechanism of PRV EP0, we performed the in vitro transcription by combining HeLa nuclear extract, purified recombinant EP0 and simple promoter constructs, and evaluated the results by primer extension. The data showed that EP0 could significantly activate the TATA-containing synthetic promoters. Moreover, EP0 activated transcription by stabilizing the formation of transcription initiation complex instead of enhancing the elongation rate. To further understand the role of EP0 on assembling the transcription initiation complex, we performed the pull-down assay using affinity precipitation of proteins from HeLa nuclear extracts and bacterially expressed glutathione-S-transferase EP0 RING finger fusion. The data showed that at least six nuclear proteins physically interacted with the EP0 RING finger. Overall, the transactivation of PRV EP0 is accomplished by enhancing the transcription initiation and is associated with at least six nuclear proteins.

Self-inactivating lentivirus vector for safe and efficient in vivo gene delivery

In vivo transduction of nondividing cells by human immunodeficiency virus type 1 (HIV-1)-based vectors results in transgene expression that is stable over several months. However, the use of HIV-1 vectors raises concerns about their safety. Here we describe a self-inactivating HIV-1 vector with a 400-nucleotide deletion in the 3' long terminal repeat (LTR). The deletion, which includes the TATA box, abolished the LTR promoter activity but did not affect vector titers or transgene expression in vitro. The self-inactivating vector transduced neurons in vivo as efficiently as a vector with full-length LTRs. The inactivation design achieved in this work improves significantly the biosafety of HIV-derived vectors, as it reduces the likelihood that replication-competent retroviruses will originate in the vector producer and target cells, and hampers recombination with wild-type HIV in an infected host. Moreover, it improves the potential performance of the vector by removing LTR sequences previously associated with transcriptional interference and suppression in vivo and by allowing the construction of more-stringent tissue-specific or regulatable vectors.

Interaction of human immunodeficiency virus type 1 Tat with the transcriptional coactivators p300 and CREB binding protein

Human immunodeficiency virus type 1 (HIV-1) encodes the transactivator protein Tat, which is essential for viral replication and progression to disease. Here we demonstrate that transcriptional activation by HIV-1 Tat involves p300 or the related cellular transcriptional coactivator CREB binding protein (CBP). Tat transactivation was inhibited by the 12S form of the adenovirus E1A gene product, which inhibits p300 function, and this inhibition was independent of its effect on NF-kappaB transcription. A biochemical interaction of p300 with Tat was demonstrated in vitro and in vivo by coimmunoprecipitation. The carboxy-terminal region of p300, which binds to E1A, was shown to bind specifically to the highly conserved basic domain of Tat, which also mediates binding to the Tat-responsive region RNA stem-loop structure. The ability of Tat to interact physically and functionally with this coactivator provides a mechanism to assemble a basal transcription complex which may subsequently respond to the effect of Tat on transcriptional elongation and represents a novel interaction between an RNA binding protein and a transcriptional coactivator.

Development of a self-inactivating lentivirus vector

We have constructed a new series of lentivirus vectors based on human immunodeficiency virus type 1 (HIV-1) that can transduce nondividing cells. The U3 region of the 5' long terminal repeat (LTR) in vector constructs was replaced with the cytomegalovirus (CMV) promoter, resulting in Tat-independent transcription but still maintaining high levels of expression. A self-inactivating (SIN) vector was constructed by deleting 133 bp in the U3 region of the 3' LTR, including the TATA box and binding sites for transcription factors Sp1 and NF-kappaB. The deletion is transferred to the 5' LTR after reverse transcription and integration in infected cells, resulting in the transcriptional inactivation of the LTR in the proviruses. SIN viruses can be generated with no significant decreases in titer. Injection of viruses into the rat brain showed that a SIN vector containing the green fluorescent protein gene under the control of the internal CMV promoter transduced neurons as efficiently as a wild-type vector. Interestingly, a wild-type vector without an internal promoter also successfully transduced neurons in the brain, indicating that the HIV-1 LTR promoter is transcriptionally active in neurons even in the absence of Tat. Furthermore, injection of viruses into the subretinal space of the rat eye showed that wild-type vector transduced predominantly retinal pigment epithelium and photoreceptor cells, while SIN vector was able to transduce other types of retinal cells, including bipolar, Müller, horizontal, and amacrine cells. This finding suggests that the HIV-1 LTR can negatively influence the internal CMV promoter in some cell types. SIN HIV vectors should be safer for gene therapy, and they also have broader applicability as a means of high-level gene transfer and expression in nondividing cells.

alpha-Lipoic acid: a metabolic antioxidant which regulates NF-kappa B signal transduction and protects against oxidative injury

Although the metabolic role of alpha-lipoic acid has been known for over 40 years, it is only recently that its effects when supplied exogenously have become known. Exogenous alpha-lipoic acid is reduced intracellularly by at least two and possibly three enzymes, and through the actions of its reduced form, it influences a number of cell process. These include direct radical scavenging, recycling of other antioxidants, accelerating GSH synthesis, and modulating transcription factor activity, especially that of NF-kappa B (Fig. 12). These mechanisms may account for the sometimes dramatic effects of alpha-lipoic acid in oxidative stress conditions (e.g., brain ischemia-reperfusion), and point the way toward its therapeutic use.

Human herpesvirus 6

Human herpesvirus 6 variant A (HHV-6A) and human herpesvirus 6 variant B (HHV-6B) are two closely related yet distinct viruses. These visuses belong to the Roseolovirus genus of the betaherpesvirus subfamily; they are most closely related to human herpesvirus 7 and then to human cytomegalovirus. Over 95% of people older than 2 years of age are seropositive for either or both HHV-6 variants, and current serologic methods are incapable of discriminating infection with one variant from infection with the other. HHV-6A has not been etiologically linked to any human disease, but such an association will probably be found soon. HHV-6B is the etiologic agent of the common childhood illness exanthem subitum (roseola infantum or sixth disease) and related febrile illnesses. These viruses are frequently active and associated with illness in immunocompromised patients and may play a role in the etiology of Hodgkin's disease and other malignancies. HHV-6 is a commensal inhabitant of brains; various neurologic manifestations, including convulsions and encephalitis, can occur during primary HHV-6 infection or in immunocompromised patients. HHV-6 and distribution in the central nervous system are altered in patients with multiple sclerosis; the significance of this is under investigation.