Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: UNIPROT:P51532 (transcriptional activator)
6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We recently have demonstrated that a C-terminal deletion mutant of the human progesterone receptor (hPRB891) fails to bind to progesterone but can bind RU 486 (Mifepristone) and other progesterone antagonists. Most significantly, this mutant receptor activates transcription of a reporter gene containing the progesterone response element in the presence of these antagonists. Taking advantage of this finding and the modular nature of functional domains of steroid receptors, we constructed a chimeric regulator (pGL-VP) by fusing the ligand-binding domain of human progesterone receptor hPRB891 to the yeast transcriptional activator GAL4 DNA-binding domain and the herpes simplex virus protein VP16 activation domain. We demonstrated that this chimeric regulator activates target genes containing the GAL4-binding sites in transient transfection assays in response to RU 486. In addition, this regulatory system has been validated by ex vivo transplantation of a stable cell line containing both the regulator and a reporter gene into rats. The dosage of RU 486 used is significantly lower than that required for antagonizing progesterone action. The gene-switch system reported here represents a regulatory system, which could be applicable for gene-transfer studies involving animals, as well as humans, in which the delivered gene(s) can be specifically turned on/off in response to an exogenous compound.
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PMID:A regulatory system for use in gene transfer. 805 76

Herpes simplex virus (HSV) virions contain at least two regulatory proteins that modulate gene expression in infected cells: the transcriptional activator VP16 and the virion host shutoff protein vhs. VP16 stimulates transcription of the HSV immediate-early genes, and vhs suppresses host protein synthesis and induces accelerated turnover of cellular and viral mRNAs. We report here that vhs binds directly to VP16: vhs and VP16 were coprecipitated from infected cells by an anti-vhs antiserum, and vhs and VP16 protein A fusions each bound intact versions of the other protein in a solid-phase capture assay. In addition, vhs and VP16 interacted in the two-hybrid activator system when coexpressed in Saccharomyces cerevisiae. vhs residues 238 to 344 were sufficient for the interaction, and the VP16 acidic transcriptional activation domain was not required. vhs blocked the ability of VP16 to enter a multiprotein complex on an immediate-early TAATGARATTC consensus sequence, indicating that vhs interacts with one or more regions of VP16 required for promoter recognition. We suggest that this interaction may play a structural role in the assembly of HSV virions and modulate the activity of vhs during infection.
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PMID:Herpes simplex virus VP16 forms a complex with the virion host shutoff protein vhs. 813 19

Varicella-zoster virus is the etiological agent of chickenpox and zoster in humans and belongs to the Alphaherpesvirinae subfamily within the family Herpesviridae. Much of the current understanding of gene regulation in alphaherpesviruses has been derived from studies of the prototype herpes simplex virus (HSV). In HSV, two virus-encoded, trans-regulatory proteins, ICP4 and ICP27, are essential for the replicative cycle of the virus. ICP4 is important in modulating HSV genes of all three kinetic classes, whereas the trans-regulatory effects of ICP27 are primarily associated with the expression of late genes. Recent evidence indicates that the trans-regulatory effects of ICP27 involve posttranscriptional processing of target gene transcripts (R. M. Sandri-Golding and G. E. Mendoza, Genes Dev. 6:848-863, 1992). The ICP27 homolog in varicella-zoster virus is a 452-amino-acid polypeptide encoded by the open reading frame 4 (ORF4) gene. Contrary to what is found with ICP27, we show that the ORF4 polypeptide is a transcriptional activator of diverse target promoters and has a critical requirement for the presence of upstream elements within these promoters to mediate its transcriptional effects. Evidence is also presented to implicate a critical role for the cysteine-rich, C-terminal region of the ORF4 polypeptide in its trans-regulatory functions. Specifically, by oligonucleotide-directed site-specific mutagenesis, we demonstrate that of 10 cysteine residues in the ORF4 polypeptide, only C-421 and C-426 are essential for transactivator function and suggest that these cysteine residues may participate in critical protein-protein interactions rather than protein-nucleic acid interactions to mediate ORF4 inducibility.
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PMID:Varicella-zoster virus open reading frame 4 encodes a transcriptional activator that is functionally distinct from that of herpes simplex virus homology ICP27. 813 31

VP16 is a herpes simplex virus (HSV)-encoded transcriptional activator protein that is essential for efficient viral replication and as such may be a target for novel therapeutic agents directed against viral gene expression. We have reconstituted transcriptional activation by VP16 in an in vitro system that is dependent on DNA sequences from HSV immediate-early gene promoters and on protein-protein interactions between VP16 and Oct-1 that are required for VP16 activation in vivo. Activation increased synergistically with the number of TAATGARAT elements (the cis-acting element for VP16 activation in vivo) upstream of the core promoter, and mutations of this element that reduce Oct-1 or VP16 DNA binding reduced transactivation in vitro. A VP16 insertion mutant unable to interact with Oct-1 was inactive, but, surprisingly, a deletion mutant lacking the activation domain was approximately 65% as active as the full-length protein. The activation domains of Oct-1 were necessary for activation in reactions containing the VP16 deletion mutant, and they contributed significantly to activation by full-length VP16. Addition of a GA-rich element present in many HSV immediate-early gene enhancers synergistically stimulated VP16-activated transcription. Finally, oligopeptides that are derived from a region of VP16 thought to contact a cellular factor known as HCF (host cell factor) and that inhibit efficient VP16 binding to the TAATGARAT element also specifically inhibited VP16-activated, but not basal, transcription. Amino acid substitutions in one of these peptides identified three residues that are absolutely required for inhibition and presumably for interaction of VP16 with HCF.
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PMID:Transcriptional activation by herpes simplex virus type 1 VP16 in vitro and its inhibition by oligopeptides. 816 93

The Epstein-Barr viral transcriptional activator ZEBRA induces expression of viral early lytic genes when introduced into cells bearing latent Epstein-Barr virus. We show here that a ZEBRA-herpes simplex viral protein 16 (VP16) fusion protein induces early viral lytic gene expression in Epstein-Barr virus-containing cells more efficiently than does wild-type ZEBRA. The fusion protein is also a more powerful transcriptional activator in these cells, as assayed with reporter constructs. Our experiments also suggest that ZEBRA manifests a function required for full activity on certain natural promoters but not on promoters bearing oligomerized ZEBRA binding sites; this function cannot be provided by VP16.
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PMID:Changing Epstein-Barr viral ZEBRA protein into a more powerful activator enhances its capacity to disrupt latency. 838 49

We have previously shown that the Tat protein of the human immunodeficiency virus type 1 (HIV-1) is a modular transcriptional activator that can be targeted upstream of either a synthetic promoter or the intact HIV promoter to activate transcription. This activation was shown to be largely dependent on the presence of consensus binding sites for the cellular transcription factor Sp1. Since the use of heterologous promoters may provide further insight into Tat-mediated transactivation, we have analyzed the transactivation of the thymidine kinase promoter of herpes simplex virus by Tat and by the acidic transcriptional transactivator VP16. The effects of mutations of defined upstream promoter elements show that Tat transactivation is dependent on Sp1 binding sites in a site-specific manner. In contrast, transactivation by the acidic transactivator VP16 is completely independent of any of the defined promoter elements upstream of the TATA box. These results suggest that Tat and the classically defined modular acidic transcriptional activators have different modes of transactivation. In addition, the substitution of the HIV-1 TATA box for the thymidine kinase TATA box substantially increases Tat transactivation, indicating that Tat transactivation may also ultimately involve TATA box-associated cellular transcription factors.
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PMID:Activation of a heterologous promoter by human immunodeficiency virus type 1 Tat requires Sp1 and is distinct from the mode of activation by acidic transcriptional activators. 841 86

Herpes simplex virus type 1 infected cell polypeptide 4 (HSV-1 ICP4) is a multifunctional phosphoprotein that is essential for viral infection. It is both a repressor and an activator of viral gene expression depending upon the promoter. ICP4 represses transcription from its own promoter. In the present study, we used general transcription factors from HeLa cell nuclear extracts, recombinant TATA binding protein (TBP) and TFIIB, and the transcriptional activator Sp1 to reconstitute in vitro transcription for the ICP4 promoter and to examine the effects of purified ICP4 on transcription. ICP4 was able to effectively repress Sp1-induced transcription from ICP4 promoter templates that contain one or multiple Sp1 binding sites. The observed inhibition required the ICP4 binding site that spans the transcription initiation site. ICP4 did not inhibit basal transcription as inferred by its inability to inhibit transcription when (i) Sp1 was not included in transcription reactions, (ii) the templates contained no Sp1 binding sites, and (iii) TBP was used in place of TFIID in the reactions. The in vitro observations were consistent with the behavior of the same constructs expressed in cells from the herpes simplex virus type 1 genome. DNase I footprinting experiments revealed that ICP4 could co-occupy the ICP4 promoter region with TBP-TFIIB, indicating that ICP4 does not necessarily exclude these factors from binding to the TATA region. The data suggest that the repressive effects of ICP4 observed in this study result from ICP4 interfering with the interactions contributing to Sp1-induced transcription.
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PMID:Herpes simplex virus infected cell polypeptide 4 preferentially represses Sp1-activated over basal transcription from its own promoter. 841 35

As ancestors of higher plants, mosses offer advantages as simple model organisms in studying complex processes such as development and signal transduction. Overexpression of transgenes after genetic transformation is a powerful technique in such studies. To establish a controllable expression system for this experimental approach we expressed a chimeric protein consisting of the Tn1O-encoded Tet repressor and the activation domain of Herpes simplex virion protein 16 in the moss Physcomitrella patens. We showed that this protein activates transcription from a suitable target promoter (Top 1O) containing seven operators upstream of a TATA box. In media containing very low levels of tetracycline (1 mg/l), expression levels of a beta-glucuronidase (GUS) reporter gene dropped to <1% of that in the absence of tetracycline. This regulation is due to interference of tetracycline with the DNA binding activity of the Tet repressor portion of the chimeric transcriptional activator. Stable transformants grown for three weeks on tetracycline-containing media showed negligible GUS activity, whereas GUS was expressed strongly within 24 h of transfer to tetracycline-free media. Potent and stringently regulated expression of other, physiologically active genes is thus readily available in the moss system using the convenient ToplO expression system.
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PMID:Tetracycline-regulated reporter gene expression in the moss Physcomitrella patens. 861 38

Herpes simplex virus (HSV) virions contain two regulatory proteins that facilitate the onset of the lytic cycle: VP16 activates transcription of the viral immediate-early genes, and vhs triggers shutoff of host protein synthesis and accelerated turnover of cellular and viral mRNAs. VP16 and vhs form a complex in infected cells, raising the possibility of a regulatory link between them. Here we show that viral protein synthesis and mRNA levels undergo a severe decline at intermediate times after infection with a VP16 null mutant, culminating in virtually complete translational arrest. This phenotype was rescued by a transcriptionally incompetent derivative of VP16 that retains vhs binding activity, and was eliminated by inactivating the vhs gene. These results indicate that VP16 dampens vhs activity, allowing HSV mRNAs to persist in infected cells. Further evidence supporting this hypothesis came from the demonstration that a stably transfected cell line expressing VP16 was resistant to host shutoff induced by superinfecting HSV virions. Thus, in addition to its well known function as a transcriptional activator, VP16 stimulates viral gene expression at a post-transcriptional level, by sparing viral mRNAs from degradation by one of the virus-induced host shutoff mechanisms.
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PMID:Herpes simplex virus VP16 rescues viral mRNA from destruction by the virion host shutoff function. 866 65

Contact between a transcriptional activator and one or more components of the RNA polymerase II transcription initiation machinery is generally believed important for activators to function. Several different molecular targets have been suggested for direct contact by herpes simplex virus virion protein VP16, including the general initiation factor TFIIB. In this report we have used several strategies to critically assess this interaction between VP16 and TFIIB. Affinity columns of VP16 bound TFIIB activity from HeLa cell extracts and the binding was reduced by mutations in the activation domain of VP16. In assays of direct binding, VP16 bound recombinant human TFIIB but not Drosophila or yeast TFIIB. Unlike binding from an extract, however, we found that the interaction between VP16 and recombinant human TFIIB was not affected by mutations in VP16 that reduce transactivation. Point mutations within human TFIIB that reduce transactivation by VP16 have been shown to reduce VP16 binding, but we show here that these same mutations critically affect both the important TBP-TFIIB interaction and the ability of TFIIB to support activator-independent basal transcription in vitro. Taken together our results suggest more evidence is needed to support the notion that TFIIB is a functionally important target for the activator VP16.
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PMID:Characterization of the interaction between the acidic activation domain of VP16 and the RNA polymerase II initiation factor TFIIB. 871 May 3


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