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)

In the present work we report the cloning of a full-length cDNA encoding the immediate-early (IE) 2 protein from human herpesvirus 6 (HHV-6) variant A (GS strain). The transcript is 4690 nucleotides long and composed of 5 exons. Translation initiation occurs within the third exon and proceeds to the end of U86. Kinetic studies indicate that the 5.5-kb IE2 mRNA is expressed under IE condition, within 2-4 h of infection. IE2 transcripts from both variants A and B are expressed under similar kinetics with IE2 transcripts accumulating up to 96 h postinfection. Although several large transcripts (>5.5 kb) hybridized with the IE2 probe, suggesting multiple transcription initiation sites, a single form of the IE2 protein, in excess of 200 kDa, was detected by Western blot. Within cells, the IE2 protein was detected (8-48 h) as intranuclear granules while at later time points (72-120 h), the IE2 protein coalesced into a few large immunoreactive patches. Transfection of cells with an IE2 expression vector (pBK-IE2A) failed to reproduce the patch-like distribution, suggesting that other viral proteins are necessary for this process to occur. Last, IE2 was found to behave as a promiscuous transcriptional activator. Cotransfection experiments in T cells indicate that IE2 can induce the transcription of a complex promoter, such as the HIV-LTR, as well as simpler promoters, whose expression is driven by a unique set of responsive elements (CRE, NFAT, NF-kB). Moreover, minimal promoters having a single TATA box or no defined eukaryotic regulatory elements were significantly activated by IE2, suggesting that IE2 is likely to play an important role in initiating the expression of several HHV-6 genes. In all, the work presented represents the first report on the successful cloning, expression, and functional characterization of the major regulatory IE2 gene/protein of HHV-6.
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PMID:Characterization of the immediate-early 2 protein of human herpesvirus 6, a promiscuous transcriptional activator. 1270 83

The in-situ conformations of peptide layers formed from the adsorption of two different synthetic 15-mer peptides at the hydrophilic silicon oxide/aqueous solution interface have been determined using neutron reflectivity (NR). The first peptide is based on the native sequence of a protein-binding domain within a heteromeric transcriptional activator, HAP2, identified from yeast Saccharomyces cerevisiae, with tyrosine (Y) present at the 1st, 8th and 15th amino acid positions, hence we denote this YYY15. Substitution of tryptophan (W) at the same locations gives WWW15. Both peptides have alpha-helical structure in phosphate buffer, as determined by circular dichroism (CD) spectra. D(2)O was used as solvent in the NR experiments to highlight structural heterogeneity across the hydrogenated peptide layers. At pH 7, YYY15 was found to form a weakly adsorbed interfacial monolayer. However, the mutant WWW15 showed strong interfacial adsorption, with the interfacial layer characterized by a middle hydrophobic sublayer of 7-8 A with lower scattering length density and two almost symmetrical hydrophilic outer sublayers of 6-8 A with higher scattering length density, suggesting the formation of a "sideways-on" helical conformation. An increase in pH to 9 resulted in the improved packing within the interfacial layer with similar structure. However, decrease in pH to 5 reduced the interfacial adsorption, mainly due to the enhanced solubility of the peptides associated with the protonation of arginine (R) and lysine (K) groups and the decreasing concentration of divalent HPO(4)(2-) in the phosphate buffer. Subsequent assessment of the reversibility of adsorption showed that once the peptide layers were formed they did not desorb. These interfacial structures may provide feasible routes to interfacial nano-templating.
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PMID:Interfacial nano-structuring of designed peptides regulated by solution pH. 1526 24

We have identified four mutations in Xenopus TFIIIA that increase the stability of TFIIIA-5 S rRNA gene complexes. In each case, the mutation has a relatively modest effect on equilibrium binding affinity. In three cases, these equilibrium binding effects can be ascribed primarily to decreases in the rate constant for protein-DNA complex dissociation. In the fourth case, however, a substitution of phenylalanine for the wild-type leucine at position 148 in TFIIIA results in much larger compensating changes in the kinetics of complex assembly and dissociation. The data support a model in which a relatively unstable population of complexes with multi-component dissociation kinetics forms rapidly; complexes then undergo a slow conformational change that results in very stable, kinetically homogeneous TFIIIA-DNA complexes. The L148F mutant protein acts as a particularly potent transcriptional activator when it is fused to the VP16 activation domain and expressed in yeast cells. Substitution of L148 to tyrosine or tryptophan produces an equally strong transcriptional activator. Substitution to histidine results in genetic and biochemical effects that are more modest than, but similar to, those observed with the L148F mutation. We propose that an amino acid with a planar side chain at position 148 can intercalate between adjacent base pairs in the intermediate element of the 5 S rRNA gene. Intercalation occurs slowly but results in a very stable DNA-protein complex. These results suggest that transcriptional activation by a cis-acting sequence element is largely dependent on the kinetic, rather than the thermodynamic, stability of the complex formed with an activator protein. Thus, transcriptional activation is dependent in large part on the lifetime of the activator-DNA complex rather than on binding site occupancy at steady state. Introduction of intercalating amino acids into zinc finger proteins may be a useful tool for producing artificial transcription factors with particularly high in vivo activity.
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PMID:Mutations in TFIIIA that increase stability of the TFIIIA-5 S rRNA gene complex: unusual effects on the kinetics of complex assembly and dissociation. 1588 46

The retroviral phenomenon of superinfection resistance (SIR) defines an interference mechanism that is established after primary infection, preventing the infected cell from being superinfected by a similar type of virus. This review describes our present understanding of the underlying mechanisms of SIR established by three characteristic retroviruses: Murine Leukaemia Virus (MuLV), Foamy Virus (FV), and Human Immunodeficiency Virus (HIV). In addition, SIR is discussed with respect to HIV superinfection of humans. MuLV resistant mice exhibit two genetic resistance traits related to SIR. The cellular Fv4 gene expresses an Env related protein that establishes resistance against MuLV infection. Another mouse gene (Fv1) mediates MuLV resistance by expression of a sequence that is distantly related to Gag and that blocks the viral infection after the reverse transcription step. FVs induce two distinct mechanisms of superinfection resistance. First, expression of the Env protein results in SIR, probably by occupancy of the cellular receptors for FV entry. Second, an increase in the concentration of the viral Bet (Between-env-and-LTR-1-and-2) protein reduces proviral FV gene expression by inhibition of the transcriptional activator protein Tas (Transactivator of spumaviruses). In contrast to SIR in FV and MuLV infection, the underlying mechanism of SIR in HIV-infected cells is poorly understood. CD4 receptor down-modulation, a major characteristic of HIV-infected cells, has been proposed to be the main mechanism of SIR against HIV, but data have been contradictory. Several recent studies report the occurrence of HIV superinfection in humans; an event associated with the generation of recombinant HIV strains and possibly with increased disease progression. The role of SIR in protecting patients from HIV superinfection has not been studied so far. The phenomenon of SIR may also be important in the protection of primates that are vaccinated with live attenuated simian immunodeficiency virus (SIV) against pathogenic SIV variants. As primate models of SIV infection closely resemble HIV infection, a better knowledge of SIR-induced mechanisms could contribute to the development of an HIV vaccine or other antiviral strategies.
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PMID:Retroviral superinfection resistance. 1610 23

The ability of Saccharomyces cerevisiae to utilize galactose is regulated by the nucleo-cytoplasmic shuttling of a transcriptional repressor, the Gal80 protein. Gal80 interacts with the transcriptional activator Gal4 in the nucleus and inhibits its function, preventing induction of the GAL genes. In response to galactose, the relative amounts of Gal80 in the cytoplasm and the nucleus are modulated by the action of a signal transducer, Gal3. Although it has been speculated that Gal3 binds galactose, this has not been experimentally demonstrated. In this study, we show that replacement of a conserved tyrosine in Gal3 by tryptophan leads to a reduction of its constitutive activity in the absence of galactose. In addition, this mutant protein was fully functional in vivo only when high concentrations of galactose were present in the medium. When overexpressed, the mutant was found to activate the genes GAL1 and GAL7/10 differentially. The implications of these findings for the fine regulation of GAL genes, and its physiological significance, are discussed.
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PMID:Replacement of a conserved tyrosine by tryptophan in Gal3p of Saccharomyces cerevisiae reduces constitutive activity: implications for signal transduction in the GAL regulon. 1616 Aug 53

The Zap1 transcription factor controls expression of genes that regulate zinc homeostasis in Saccharomyces cerevisiae. The solution structure of two zinc fingers (zf1-2(CA3)) derived from a zinc-responsive domain of Zap1 (zf1-2) has been determined. Under zinc-limiting conditions, zinc finger 2 (zf2) from this domain has been shown to be a constitutive transcriptional activator. Moreover, repression of zf2 function in zinc-replete cells required zinc coordination to both canonical finger 1 (zf1) and zf2 metal sites, suggesting zf1-zf2 cooperativity underlies Zap1 metalloregulation. A structural basis for this cooperativity is identified here. Favorable inter-helical contacts in zf1-2(CA3) extend the individual finger hydrophobic cores through the zf1-zf2 interface. Tryptophan residues at position 5 in each finger provide numerous non-helical inter-finger contacts reminiscent of those observed in GLI1 zinc fingers 1 and 2. The molecular mechanism for zf1-dependent repression of zf2 transcriptional activation is explored further using NMR and CD titration studies. While zf1 independently forms a betabetaalpha solution structure, the majority of zf2 ensemble solution states do not adopt the canonical betabetaalpha zinc finger fold without zf1-zf2 interactions. Cooperative effects on Zn(II) affinities stemming from these finger-finger interactions are observed also in calorimetric studies, in which the 160(+/-20)nM (zf1) and 250(+/-40)nM (zf2) K(d) values for each individual finger increased substantially in the context of the zf1-2 protein (apparent K(dzf1-2WT)=4.6(+/-1.2)nM). On the basis of the above observations, we propose a mechanism for Zap1 transcriptional regulation in which zf1-zf2 interactions stabilize the betabetaalpha folded "repressed state" of the zf2 activation domain in the presence of cellular Zn(II) excess. Moreover, in contrast to earlier reports of <<1 labile zinc ion/Escherichia coli cell, the zf1-zf2 zinc affinities determined calorimetrically are consistent with Zn(II) levels >>1 labile zinc ion/eukaryotic cell.
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PMID:Solution structure of a Zap1 zinc-responsive domain provides insights into metalloregulatory transcriptional repression in Saccharomyces cerevisiae. 1648 1

HIV-associated dementia results from neuronal loss and an alteration of neuronal function due to a loss of synapses. While HIV infection in astrocytes is limited, astrocytes exhibit a chronic nonproductive infection that can lead to the release of neurotoxic proteins. Additionally, infection can disrupt the normal neurotrophic role of astrocytes that results in neuronal death. Gonadal steroid hormones are known to act as trophic and protective factors in the brain under a variety of normal and pathological conditions. In the present study, to determine if estrogen plays a role in the ability of Tat to function as a transcriptional activator within astrocytes, we examined the effect of estrogen on regulation of viral transcription. We utilized an immortalized human astrocyte cell line (SVGA) stably transfected with a reporter plasmid containing the HIV-1IIIB LTR driving the chloramphenicol acetyltransferase (CAT) gene. The amount of transcriptional activity was measured by quantifying the amount of CAT produced. We determined that 17beta-estradiol treatment (1 nM) had no effect on basal LTR activity. Following transfection with a Tat-expressing plasmid, there was a 100-fold increase in CAT production. This induction was reduced by 40% in cells pretreated with 17beta-estradiol. 17beta- Estradiol only suppressed transcription stimulated by Tat. Furthermore, we determined that this effect was specific to 17beta-estradiol and estrogen receptor agonists. This activity was limited to astrocytes as no effect was observed in a monocytic cell line. Finally, the mechanism of action did not involve an alteration in levels of Cdk9 or Cyclin T1 proteins necessary for Tat activation of the HIV-1 LTR. This study demonstrates a novel activity of 17beta-estradiol in glial cells that could play a role in the maintenance of neuronal health during HIV infection of the central nervous system.
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PMID:Estradiol negatively regulates HIV-LTR promoter activity in glial cells. 1662 39

Interferon (IFN)-gamma-induced expression of indoleamine 2,3-dioxygenase (IDO), an enzyme that inhibits some pathogens by limiting tryptophan availability, is transcriptionally enhanced by tumor necrosis factor (TNF)-alpha. The expression of interferon responsive factor (IRF)-1, an IFN-gamma-induced transcriptional activator critical to IDO regulation, is also enhanced synergistically in response to IFN-gamma and TNF-alpha. The IRF-1 regulatory region contains an IFN-gamma-activated sequence (GAS) and a kappaB site, which bind STAT-1 and NF-kappaB, respectively. The TNF-alpha-mediated increase in STAT-1 activation in IFN-gamma-treated cells enhances IRF-1 transcription; however, the contribution of TNF-alpha-mediated increases in nuclear NF-kappaB is uncertain. To identify whether binding of NF-kappaB upstream of the IRF-1 gene is rate-limiting in IRF-1 expression in response to IFN-gamma and TNF-alpha, a proteasome inhibitor was utilized to maintain nuclear translocation of NF-kappaB at constitutive levels; its effect on IRF-1 expression and IDO-specific transcription was evaluated. By limiting NF-kappaB nuclear translocation, IRF-1 expression in IFN-gamma and TNF-alpha treated cells was maintained at a level comparable to that achieved in response to IFN-gamma alone, and the synergistic increase IDO transcription was blocked, suggesting that increases in NF-kappaB translocation are required for synergistic IDO expression in response to IFN-gamma and TNF-alpha.
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PMID:NF-kappa B activation contributes to indoleamine dioxygenase transcriptional synergy induced by IFN-gamma and tumor necrosis factor-alpha. 1693 Oct 33

The transcriptional activator HrpB of the bacterial wilt causing betaproteobacterium Ralstonia solanacearum represents a key regulator for pathogenicity. In particular, it drives expression of hrp genes encoding a type III secretion system (T3SS) as well as effector molecules for delivery into the host cytosol to promote disease. However, the HrpB regulon extends beyond this T3SS. We describe here an HrpB-activated operon of six genes that is responsible for the synthesis of a fluorescent isatin derivative of 149 Amu that we named HDF for HrpB-dependent factor and that we purified from culture supernatants. The structure of the labile molecule was solved by using NMR and CD spectroscopy to be (3S)-3-hydroxy-indolin-2-one and confirmed by its chemical synthesis and MS spectrometry. HDF was found to be present at 20 nM in wild-type cultures grown on minimal medium, and its synthesis increased 15-fold upon overproduction of HrpB, confirming that HrpB activates HDF synthesis. The addition of tryptophan significantly stimulated HDF biosynthesis and was shown to represent the precursor molecule for HDF synthesis. A search for the biological function of the molecule revealed that HDF induces acyl-homoserine lactone receptor-mediated reporter activity of the well studied LuxR transcriptional regulator of Vibrio fischeri. Thus, our results provide evidence that the specificity of acyl-homoserine lactone (acyl-HSL) receptors is clearly broader than previously considered. The failure to detect induction by HDF of the described endogenous quorum-sensing circuits of the pathogen points to a role in interfering with cell-cell signaling of rivalling bacteria.
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PMID:The Ralstonia solanacearum pathogenicity regulator HrpB induces 3-hydroxy-oxindole synthesis. 1789 Mar 23

The p14(ARF) tumor suppressor functions as 'oncogenic checkpoint' that prevents unrestricted cellular proliferation in response to oncogenic signaling. Albeit, the major pathway through which ARF operates is the ARF-Mdm2-p53 axis, ARF directly binds to and inactivates transcription function of a number of DNA-bound activators. In the present study we show that p14(ARF) inhibits transcription activation of HIV-1 LTR promoter activity by Tat protein. Tat protein is a RNA-bound transcriptional activator whose function is strictly required for HIV-1 replication. We determined that p14(ARF) inhibits Tat transactivation of HIV-1 LTR by promoting Tat degradation via an ubiquitin-independent pathway.
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PMID:p14ARF is capable of promoting HIV-1 tat degradation. 1841 67


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