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

The promoters of the Saccharomyces cerevisiae histone H3 and H4 genes were examined for cis-acting DNA sequence elements regulating transcription and cell division cycle control. Deletion and linker disruption mutations identified two classes of regulatory elements: multiple cell cycle activation (CCA) sites and a negative regulatory site (NRS). Duplicate 19-bp CCA sites are present in both the copy I and copy II histone H3-H4 promoters arranged as inverted repeats separated by 45 and 68 bp. The CCA sites are both necessary and sufficient to activate transcription under cell division cycle control. A single CCA site provides cell cycle control but is a weak transcriptional activator, while an inverted repeat comprising two CCA sites provides both strong transcriptional activation and cell division cycle control. The NRS was identified in the copy I histone H3-H4 promoter. Deletion or disruption of the NRS increased the level of the histone H3 promoter activity but did not alter the cell division cycle periodicity of transcription. When the CCA sites were deleted from the histone promoter, the NRS element was unable to confer cell division cycle control on the remaining basal level of transcription. When the NRS element was inserted into the promoter of a foreign reporter gene, transcription was constitutively repressed and did not acquire cell cycle regulation.
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PMID:Histone H3 transcription in Saccharomyces cerevisiae is controlled by multiple cell cycle activation sites and a constitutive negative regulatory element. 144 78

Upon incubation at 37 degrees C in the absence of Ca2+ ions, pathogenic yersiniae release high amounts of pYV plasmid-encoded proteins called Yops, involved in pathogenesis. Yersinia enterocolitica also express two outer membrane proteins, an adhesin called YadA and a lipoprotein called YlpA. The production of the Yops is co-ordinately regulated by a 20 kb region of the plasmid referred to as the 'Ca2+ dependence region' and containing at least four loci called virA, virB, virC, and virF. The 8.5 kb virC region, involved in the specific transport of the Yops, is a single operon containing 13 open reading frames called yscA to yscM. Gene virF encodes a key transcriptional activator of the yop, yadA and ylpA genes. It is only transcribed at 37 degrees C and its expression is modulated by a chromosome-encoded histone-like protein called YmoA. We show here that virF also controls the virC operon. By contrast, virF is not essential for the induction of virA and virB. The VirF protein binds specifically to yop promoters. In particular, it protects the region spanning nucleotides -64 to -34 of yopH. In order to analyse the role of temperature in the induction of the yop regulon, we constructed Y. enterocolitica strains expressing virF from the tac promoter. In spite of the fact that virF was transcribed at 25 degrees C, neither the Yops nor YadA were expressed at that temperature. This poor response to VirF at 25 degrees C was at least partially due to a weak and slow transcription of the genes controlled by virF. Surprisingly, when cloned on pACYC184, gene yadA was expressed even in absence of VirF, but remained thermodependent. Hence temperature and virF are both required for the induction of the yop regulon. Among other possible roles, temperature could modify the structure of either the activator itself or the yop promoter. The fact that VirF binds in vitro to yop promoters at 25 degrees C rules out the first hypothesis. In order to test the second hypothesis, we studied, in vivo, the activity of the yopH promoter in ymoA mutants. The yopH promoter became active in the absence of VirF, indicating that yop promoter activity depends upon chromatin structure. We conclude from these two observations that, in vivo, temperature is required to modify the DNA structure of the yop promoters in order to allow the action of the transcriptional activator.
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PMID:Role of the transcriptional activator, VirF, and temperature in the expression of the pYV plasmid genes of Yersinia enterocolitica. 155 53

The virulence functions of Yersinia enterocolitica include the pYV-encoded Yop proteins and YadA adhesin as well as the chromosome-encoded enterotoxin, Yst. The yop and yadA genes form a temperature-activated regulon controlled by the transcriptional activator VirF. Gene virF, also localized on pYV, is itself thermoinduced in the absence of other pYV genes. The enterotoxin yst gene is silent in some collection strains including strain W22703. This paper describes two Tn5-Tc1 chromosomal insertion mutants of W22703 transcribing virF, and hence the yop and yadA genes, at low temperature. These mutants also resumed their production of Yst, with its typical temperature dependence. Both mutations were insertions in the same gene called ymoA for 'Yersinia modulator'. The cloned ymoA gene fully complemented the two mutations. Several properties of the mutants suggest that ymoA encodes a histone-like protein. According to the nucleic acid sequence, the product of ymoA is an 8064 Da protein rich in aspartic acid (9%), glutamic acid (9%) and lysine (10.5%), but the predicted amino acid sequence shows no similarity with any described histone-like protein. This work supports recent reports which propose a role for DNA topology and bacterial chromatin structure in thermoregulation of virulence functions.
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PMID:ymoA, a Yersinia enterocolitica chromosomal gene modulating the expression of virulence functions. 195 83

The expression of the pap pilus operon of Escherichia coli is under a phase-variation control mechanism in which cells undergo a reversible transition between transcriptionally active (phase ON) and inactive (phase OFF) states. In this study, we explore the roles of leucine-responsive regulatory protein (Lrp) and the histone-like protein H-NS in the regulation of pap phase variation. Our data indicate that the phase OFF state results from repression of the intrinsically active papBA promoter by Lrp and H-NS, each of which can act independently as transcriptional repressors. Lrp requires pap DNA sequences upstream of the papBA promoter for its repressor activity whereas H-NS does not. In contrast, in the ON state, Lrp, in conjunction with PapI, activates pap transcription. This activation is not merely a result of alleviating the H-NS mediated repression, but induces a level of transcription that is eightfold higher than the basal level of transcription from the papBA promoter measured in the absence of both H-NS and Lrp. Analysis of Lrp activation mutants indicates that binding of Lrp to pap DNA sequences is not sufficient for transcription activation, consistent with a model in which an additional domain of Lrp interacts with the transcriptional apparatus. Together, our results show that Lrp functions as a transcriptional activator in phase-ON cells and as a repressor of basal transcription in phase-OFF cells. Because pap phase variation occurs in the absence of H-NS, it is not clear what role this regulatory protein plays in pap gene regulation.
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PMID:Leucine-responsive regulatory protein plays dual roles as both an activator and a repressor of the Escherichia coli pap fimbrial operon. 749 79

We have isolated a small Escherichia coli protein which stably interacts with ribosomal RNA P1 promoter DNA. We present evidence showing that the protein is identical to the histone-like E. coli protein, H-NS (H1). Binding of H-NS to the P1 promoter region is dependent on the DNA curvature. Mapping the H-NS-DNA contact sites by nuclease protection and high-resolution footprinting techniques reveal three H-NS-binding domains, and contacts of the protein in the major groove of the bent DNA. The binding region extends from position -18 to -89, relative to the P1 transcription start site, and shows an overlap with the known binding sites for Fis, another E. coli protein, which acts as transcriptional activator of P1. The binding of H-NS does not displace Fis; instead, heterologous complexes are formed. Apparently, H-NS and Fis bind to separated curved DNA segments, with the planes of the curves pointing into different directions. In vitro transcriptional analyses demonstrate that H-NS represses rRNA P1 promoter-directed transcription. Repression is most pronounced in the presence of Fis. Thus, H-NS seems specifically to antagonize Fis-dependent activation. No comparable inactivation is observed for the second rRNA promoter P2.
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PMID:Evidence for a regulatory function of the histone-like Escherichia coli protein H-NS in ribosomal RNA synthesis. 751 87

Expression of CFA/I fimbriae of Escherichia coli requires the transcriptional activator CfaD. The mechanism by which CfaD activates the CFA/I promoter is to overcome the repression by H-NS, one of the histone-like proteins in E coli. This study addresses the question of which sequences in the promoter region of CFA/I interact with CfaD and H-NS. In order to determine this, deletion mutants of the CFA/I promoter were constructed and cloned upstream of the promoterless lacZ gene. The effect of CfaD and H-NS on the expression of these constructs was determined.
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PMID:Regions of the CFA/I promoter involved in the activation by the transcriptional activator CfaD and repression by the histone-like protein H-NS. 774 26

Dps is a non-specific DNA-binding protein abundant in starved Escherichia coli cells and is important for the defence against hydrogen peroxide. We found that dps mRNA levels are controlled by rpoS-encoded sigma S, the transcriptional activator OxyR and the histone-like IHF protein. In exponentially growing cells, dps is induced by treatment with hydrogen peroxide in an OxyR-dependent manner. This OxyR-dependent induction occurs only during log phase, although the OxyR protein is present in stationary phase. In the stationary phase cells, dps is expressed in a sigma S- and IHF-dependent manner. The purified OxyR and IHF proteins are also shown to bind upstream of the dps promoter. Our results suggest that the dps promoter is recognized by both sigma 70-holoenzyme and sigma S-holoenzyme, since OxyR acts through sigma 70 and the starts of the OxyR- and sigma S-dependent transcripts are identical.
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PMID:The dps promoter is activated by OxyR during growth and by IHF and sigma S in stationary phase. 798 6

Both activation and repression have been implicated in the cell cycle-regulated transcription of the histone HTA1-HTB1 locus in Saccharomyces cerevisiae. Transcriptional repressors have been identified through the isolation of recessive mutations in the HIR1, HIR2 and HIR3 genes. These three regulatory genes encode proteins that act at a negative site in the HTA1-HTB1 promoter, and their inactivation results in cell cycle-independent transcription. We report here on the characterization of a fourth HIR mutant. The HIR4-1 mutation is dominant, and the phenotypes that it confers suggest that the mutant gene encodes an altered transcriptional activator. The function of this activator is very specific: it uniquely regulates transcription of the HTA1-HTB1 locus, and it may antagonize repressors that act through the HTA1-HTB1 negative site.
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PMID:The HIR4-1 mutation defines a new class of histone regulatory genes in Saccharomyces cerevisiae. 822 24

The chromosome of Y. enterocolitica encodes a heat-stable enterotoxin, Yst, being related to STI. The capacity to produce Yst generally disappears during storage of the strains. In these strains, the yst gene is intact but remains silent. The pYV plasmid encodes the eleven secreted antihost proteins called Yops as well as the outer membrane protein YadA. The Yops are secreted by a novel, pYV-encoded secretion mechanism. This mechanism which does not involve the removal of an N-terminal signal sequence, is encoded by the pYV virA and virC loci. The virC locus contains 13 genes called yscA-M. The virA locus encodes the LcrD membrane protein. The yop, yadA and ysc genes form the yop regulon controlled by transcriptional activator VirF. Transcription of the yop, yadA, ysc and virF genes is controlled by temperature. A chromosome-encoded histone-like protein, called YmoA, is involved in the thermoregulation of the yop regulon, which suggests that this thermoregulation could result from temperature-induced changes in DNA topology. The phenotype of ymoA mutants resembles that of osmZ or drdX mutants of E. coli but YmoA is not the Yersinia homologue of the E. coli histone H1. The YmoA histone is also involved in the silencing of the yst gene.
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PMID:Role of the transcription activator virF and the histone-like protein YmoA in the thermoregulation of virulence functions in yersiniae. 834 24

The yeast transcriptional activator ADR1, which is required for ADH2 and peroxisomal gene expression, contains four separable and partially redundant activation domains (TADs). Mutations in ADA2 or GCN5, encoding components of the ADA coactivator complex involved in histone acetylation, severely reduced LexA-ADR1-TAD activation of a LexA-lacZ reporter gene. Similarly, the ability of the wild-type ADR1 gene to activate an ADH2-driven promoter was compromised in strains deleted for ADA2 or GCN5. In contrast, defects in other general transcription cofactors such as CCR4, CAF1/POP2, and SNF/SWI displayed much less or no effect on LexA-ADR1-TAD activation. Using an in vitro protein binding assay, ADA2 and GCN5 were found to specifically contact individual ADR1 TADs. ADA2 could bind TAD II, and GCN5 physically interacted with all four TADs. Both TADs I and IV were also shown to make specific contacts to the C-terminal segment of TFIIB. In contrast, no significant binding to TBP was observed. TAD IV deletion analysis indicated that its ability to bind GCN5 and TFIIB was directly correlated with its ability to activate transcription in vivo. ADR1 TADs appear to make several contacts, which may help explain both their partial redundancy and their varying requirements at different promoters. The contact to and dependence on GCN5, a histone acetyltransferase, suggests that rearrangement of nucleosomes may be one important means by which ADR1 activates transcription.
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PMID:ADR1 activation domains contact the histone acetyltransferase GCN5 and the core transcriptional factor TFIIB. 894 99


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