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

The LuxR protein is a transcriptional activator which, together with a diffusible small molecule termed the autoinducer [N-(3-oxohexanoyl)-L-homo-serine lactone], represents the primary level of regulation of the bioluminescence genes in Vibrio fischeri. LuxR, in the presence of autoinducer, activates transcription of the luxICDABEG gene cluster and both positively and negatively autoregulates transcription of the divergently oriented luxR gene, activating transcription at low levels of autoinducer, and repressing synthesis at high autoinducer concentration. Seven LuxR point mutants which activate V. fischeri lux transcription in the absence of autoinducer (LuxR*) have been characterized. The LuxR* proteins activated transcription of the bioluminescence genes to levels 1.5-40 times that achieved by wild-type LuxR without autoinducer. All of the LuxR* mutants retained responsiveness to autoinducer. However, in each case the degree of stimulation in response to autoinducer was lower than that observed for wild-type LuxR. The LuxR* proteins retained the requirement for autoinducer for autoregulation of the luxR gene. We propose that the LuxR protein exists in two conformations, an inactive form, and an active form which predominates in the presence of autoinducer. The LuxR* mutations appear to shift the equilibrium distribution of these two forms so as to increase the amount of the active form in the absence of autoinducer, while autoinducer can still convert inactive to active species. The differential effects of the LuxR* proteins at the two lux promoters suggest that LuxR stimulates PluxR transcription by a different mechanism to that used at the PluxI promoter, implying that binding of LuxR to its binding site, known to be necessary for transcriptional activation, may not be sufficient.
Mol Gen Genet 1996 Oct 16
PMID:Autoinducer-independent mutants of the LuxR transcriptional activator exhibit differential effects on the two lux promoters of Vibrio fischeri. 891 23

Opaque-2 (O2) encodes a transcriptional activator of the basic domain-leucine zipper (bZIP) class, which controls the expression level in maize endosperm of the 22kD alpha-zeins and a number of non-storage proteins. The interaction of the O2 protein at three clustered binding sites on an isolated 22 kD zein gene promoter has been investigated. O2 is shown to transactivate transcription from these sites in tobacco mesophyll protoplasts as well as in maize endosperm cells transformed by particle bombardment. The binding sites have been mutated by base exchanges, singly or in different combinations, to determine their contribution to transactivation in vivo in both the leaf protoplast and the maize endosperm system. The effect of these mutations on binding of O2 in vitro was determined by electrophoretic mobility shift assays (EMSA), using O2 protein expressed in E. coli. Two of the sites seemed to be equally effective in responding to Opaque-2 in vivo in both cell types, although one of them does not contain an ACGT core sequence, and has a lower affinity for O2 in vitro than the ACGT-containing binding site. A third site, which has the lowest affinity of all three, confers no detectable O2-dependent promoter activation alone, but significantly increases activation in combination with either one of the other sites. Hence, weaker O2 binding sites can still mediate major O2-dependent effects when present in target promoters in vivo.
Mol Gen Genet 1996 Oct 28
PMID:The role of multiple binding sites in the activation of zein gene expression by Opaque-2. 891 16

The wheat bZIP protein HBP-1a(17) is a putative transcription factor regulating histone gene expression. To delineate the functional domain(s) of this factor, we made a series of effector constructs expressing fusion proteins, in which various portions of HBP-1a(17) are fused to the DNA-binding domain of the yeast transcriptional activator GAL4, in plant cells. When the beta-glucuronidase (GUS) reporter gene, driven by the wheat histone H3 core promoter harboring the GAL4-binding sequence, was co-transfected with such effector genes into tobacco protoplasts, several portions of HBP-1a(17) influenced reporter gene expression. The N-terminal one-third of HBP-1a(17), termed the P region (residues 1-118) due to its Pro content, did not activate the reporter gene, in contrast to the corresponding Pro-rich region of Arabidopsis GBF1 (residues 1-110), which functions as an activation domain. When the P region was divided into two, however, both its N-terminal (1-56; termed NP) and C-terminal (58-118; termed PC) halves were able to enhance expression of the reporter gene. When the NP region was further divided into NP(5-30) and NP(30-56), both regions still retained activating ability. These results suggest that the P region of HBP-1a(17) is composed of several modules each having activating function, and modification and/or conformational changes of the P region might influence its function.
Mol Gen Genet 1997 Feb 20
PMID:Dissection of the wheat transcription factor HBP-1a(17) reveals a modular structure for the activation domain. 906 88

The gamma subunit of eukaryotic translation initiation factor 2 is an EF-Tu-like protein that plays an essential role in protein synthesis. We have isolated an eIF-2gamma homolog from the fission yeast Schizosaccharomyces pombe that complements a gcd11 null allele in Saccharomyces cerevisiae. GCD11 is an essential gene that encodes S. cerevisiae eIF-2gamma. Comparison among three eIF-2gamma homologs from humans, S. cerevisiae, and S. pombe, and a putative Drosophila homolog, reveals the presence of a domain N-terminal to the GTP-binding (G) domain that varies in length (relative to EF-Tu) from 12 residues in S. pombe to 89 residues in S. cerevisiae. In S. cerevisiae, these sequences are not essential for function. However, unlike a deletion, a missense mutation in this domain confers a slow growth phenotype and constitutively derepresses expression of the GCN4 transcriptional activator. The eIF-2gamma homologs also contain a partially conserved 35-37 amino acid insertion in the G domain that is absent from EF-Tu and other G proteins. Unlike the variable N-terminal domain, these residues are required for the essential function of eIF-2gamma.
Mol Gen Genet 1997 Feb 27
PMID:Functional analysis of homologs of translation initiation factor 2gamma in yeast. 907 82

The yeast transcriptional activator Gcn4 requires the Ada2/Gcn5/Ada3 co-activator complex to exert part of its activation potential. Here we show that the sequence of the DNA target modulates the function of Gcn4 by modifying this requirement. Promoter configurations were generated that rendered Gcn4-induced transcription either completely dependent or completely independent of the Ada2/Gcn5/Ada3 complex. The topological constraints imposed by these configurations suggest that Gcn4 makes multiple contacts with the basic transcription machinery that are subject to modification by the incident DNA target. We propose that these modifications further determine the direction on the chromosome in which an otherwise symmetric, dimeric transcription factor will activate.
Mol Gen Genet 1997 Feb 27
PMID:The DNA target sequence influences the dependence of the yeast transcriptional activator Gcn4 on co-factors. 907 89

Murine gammaherpesvirus 68 (MHV-68) is a relatively recently discovered pathogen of wild rodents and provides a unique opportunity to explore in detail the interactions of a gammaherpesvirus with its natural host. It may also provide a much needed small animal model for human gammaherpesviruses. As a step in the detailed analysis of virus gene structure and expression we have sequenced over 20 kb of the MHV-68 genome and mapped gene transcripts by Northern blot hybridization. The region we chose to analyse contains several conserved gene blocks as well as some less well conserved genes and allowed us to estimate the relationship of this virus to other herpesvirus family members. Of particular interest is the fact that none of the characteristic Epstein-Barr virus (EBV) genes is present at this genomic locus although MHV-68 does have one gene encoding a membrane glycoprotein, 9p150, which shows similarities to the major membrane glycoprotein of EBV. Our results further confirm that MHV-68 is a gammaherpesvirus marginally more closely related to a cluster of gammaherpesviruses including herpesvirus salmiri than to EBV. Northern analysis shows that the temporal regulation of expression is broadly similar to that of other herpesviruses in this region of the genome. We also show that like other gammaherpesviruses, MHV-68 splices its homologue of the EBV transcriptional activator gene BMRF1.
J Gen Virol 1997 Jun
PMID:Genetic content and preliminary transcriptional analysis of a representative region of murine gammaherpesvirus 68. 919 40

A convenient system for the control of gene expression in Saccharomyces cerevisiae was developed. Tetracycline-responsive promoters were constructed by fusing the tetracycline operator (tetO) to the S. cerevisiae HOP1 promoter. When fused to the tetracycline repressor (tetR), trans-activation domains of both GAL4 and HAP4 were capable of promoting transcription from the tetO-HOP1 chimeric promoter, but the tetR-HAP4 fusion activator was the more efficient transcriptional activator. Addition of tetracycline nearly completely repressed activator-dependent transcription from the tetO-HOP1 promoter. Moreover, tetracycline-dependent repression of YEF3, CDC28 and RAM2 expression impaired cell growth. Thus, this system is useful for the elucidation of gene function in S. cerevisiae.
Mol Gen Genet 1997 Jul
PMID:Regulation by tetracycline of gene expression in Saccharomyces cerevisiae. 926 32

The sno gene cluster in Streptomyces nogalater ATCC 27451 contains the nogalamycin biosynthesis genes. A set of plasmid constructions carrying fragments of the sno cluster that lie downstream of snoD were used to complement the S. galilaeus mutant H039, which is blocked in rhodosamine and 2-deoxyfucose biosynthesis in the aclacinomycin pathway. Sequence analysis of this cluster revealed three contiguous open reading frames (ORFs) that were designated snoF, snoG, and snoH. Only those plasmid constructs that expressed SnoG were able to complement H039. SnoG shows similarity to GalE, a UDP-glucose-4-epimerase catalyzing the epimerization of UDP-glucose to UDP-galactose. The putative SnoF protein is similar to 3,5-epimerases involved in rhamnose biosynthesis. The deduced product of snoH is a 489-amino acid polypeptide. It is similar to the product of dau ORF3 found in the daunomycin cluster. However its function is still unclear. Based on the complementation experiments and sequence analysis, this part of the sno cluster is suggested to be involved in the biosynthesis of the sugar portion of nogalamycin. Interestingly, SnoA, a transcriptional activator for the sno minimal polyketide synthase, is also needed to express this cluster.
Mol Gen Genet 1997 Sep
PMID:Characterization of Streptomyces nogalater genes encoding enzymes involved in glycosylation steps in nogalamycin biosynthesis. 934 12

Expression of the gene GCY1 in Saccharomyces cerevisiae is induced by about 25-fold in the presence of galactose as a result of activation by Gal4p. In contrast to other Gal4p-regulated genes, such as GAL1 or GAL10, GCY1 is transcribed at a relatively high basal level. We have analysed the basis of this behaviour and have found that, in addition to a UASGAL, a binding site for the general regulatory factor Reb1p is localized 100 bp upstream of the TATA sequence and about 140 bp 3' to the UASGAL. Reb1p binds to this site with low affinity. Reb1p, an abundant, multifunctional DNA-binding protein in yeast, acts as a weak transcriptional activator in the control regions of several genes encoding unrelated functions. The action of Reb1p is assumed to be strongly position dependent. In the control region of GCY1. Reb1p acts independently of position and stimulates basal expression of GCY1 about threefold, whereas Gal4p-mediated activation is not influenced significantly. Promoter-proximal insertion of an additional Reb1p recognition site enhances basal transcription only marginally, but can largely compensate for deletion of the natural Reb1p-binding site. Either an Abf1p- or a Rap1p-binding site can substitute for the Reb1p recognition sequence, indicating that these general regulatory factors fulfill related functions in basal transcription, without affecting Gal4p-mediated activation. In addition to Reb1p, the sequence of the Gal4p-binding site influences basal transcription. This effect is independent of the Gal4 protein, as it operates in a gal4 mutant background as well. This finding suggests that the nucleotide sequence of the UASGAL in the GCY1 promoter has intrinsic properties, presumably a particular DNA structure, that influence basal transcription and act synergistically with Reb1p.
Mol Gen Genet 1997 Nov
PMID:The general regulatory factor Reb1p controls basal, but not Gal4p-mediated, transcription of the GCY1 gene in yeast. 943 93

The Epstein-Barr virus (EBV) proteins EBNA1, EBNA2, EBNA3A, EBNA3C, LMP1 and EBNA-LP are essential for the in vitro immortalization of primary B lymphocytes by EBV. EBNA2 is a transcriptional activator of viral and cellular genes. Both EBNA3A and EBNA3C have been shown to specifically inhibit EBNA2-activated transcription by direct interaction with RBP-Jkappa, a cellular DNA-binding factor known to recruit EBNA2 to EBNA2-responsive genes. This interaction interferes with the binding of RBP-Jkappa to DNA in vitro, and this is probably the mechanism by which EBNA3A and EBNA3C repress EBNA2-activated transcription in vivo. EBNA3A and EBNA3C also directly repress transcription when tethered to a promoter via the DNA-binding domain of the yeast Gal4 protein. As RBP-Jkappa has been previously shown to be a repressor in mammalian cells, this repression could be due to the recruitment of RBP-Jkappa by Gal4-EBNA3A and 3C. In this study, we have precisely mapped the domain of EBNA3A involved in the interaction with RBP-Jkappa and we have shown that interaction with RBP-Jkappa is not required for the Gal4-EBNA3A-mediated repression. Furthermore, we have characterized in EBNA3A a domain of 143 amino acids which is necessary and sufficient for EBNA3A-dependent repression.
J Gen Virol 1998 Feb
PMID:Transcriptional repression by the Epstein-Barr virus EBNA3A protein tethered to DNA does not require RBP-Jkappa. 947 21


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