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PubMed1999

The DNA binding-independent function of the glucocorticoid receptor mediates repression of AP-1-dependent genes in skin.

The glucocorticoid receptor (GR) mediates the biological effects of glucocorticoids (GCs) through activation or repression of gene expression, either by DNA binding or via interaction with other transcription factors, such as AP-1. Work in tissue culture cells on the regulation of AP-1-dependent genes, such as collagenase (MMP-13) and stromelysin (MMP-3) has suggested that the antitumor and antiinflammatory activity of GCs is mediated, at least in part, by GR-mediated downmodulation of AP-1. Here, we have identified phorbol ester-induced expression of MMP-3 and MMP-13 in mouse skin as the first example of an in vivo system to measure negative interference between AP-1 and GR in the animal. Cell type-specific induction of these genes by tumor promoters is abolished by GCs. Importantly, this is also the case in GR(dim) mice expressing a DNA binding-defective mutant version of GR. In contrast, the newly identified target genes in skin, plasma glutathione peroxidase and HSP-27, were induced by GC in wild-type, but not in GR(dim) mice. Thus, these data suggest that the DNA binding-independent function of the GR is dispensable for repression of AP-1 activity in vivo and responsible for the antitumor promoting activity of GCs.

Animals↗
PubMed1992

Regulation of the secretion of Rhizopus oligosporus extracellular carboxyl proteinase.

Secretion of the extracellular Rhizopus carboxyl proteinase (EC 3.4.23.6) by Rhizopus oligosporus is repressed in the presence of low-molecular-mass sources of nitrogen, sulphur and carbon. Proteinase is secreted when the medium is deficient in any one of these three nutrients. In the case of nitrogen metabolite repression, control is at the level of transcription. Induction of proteinase secretion by exogenous protein does not occur in any of the media examined.

Aspartic Acid Endopeptidases↗
PubMed1973

Cyclic adenosine 3',5'-monophosphate in Escherichia coli.

The concentration of cyclic adenosine 3',5'-monophosphate (c-AMP) in Escherichia coli growing on different sources of carbon was studied. Cultures utilizing a source of carbon that supported growth relatively poorly had consistently higher concentrations of c-AMP than did cultures utilizing sugars that supported rapid growth. This relationship was also observed in strains defective in c-AMP phosphodiesterase and simultaneously resistant to catabolite repression; in such strains the c-AMP concentration was slightly higher for several sources of carbon tested. Cultures continued to synthesize c-AMP and secreted it into the medium, under conditions that brought about an inhibition of the intracellular accumulation of the cyclic nucleotide. Transient repression of the synthesis of beta-galactosidase was not associated with an abrupt decrease in the cellular concentration of c-AMP.

Bacterial Proteins↗
PubMed1979

Synthesis of nitrogenase and heterocysts by Anabaena sp. CA in the presence of high levels of ammonia.

Anabaena sp. CA fails to synthesize heterocysts and nitrogenase when grown with KNO3 as the nitrogen source. By contrast, both heterocysts and proheterocysts are synthesized in NH4Cl-containing media to a level nearly commensurate with cells grown in the absence of combined nitrogen. The growth rate of the organism in NH4Cl-containing media was similar to that obtained with KNO3 as the nitrogen source and was independent of the presence of N2 in the atmosphere. Thus, our results indicate that the organism assimilated nitrate and ammonium nitrogen equally well to meet the nitrogen requirements for growth. Moreover, in contrast to previous studies with other cyanobacteria, the repressor singal for heterocyst differentiation in Anabaena sp. CA is not derived from the metabolism of ammonia but appears to be involved with nitrate metabolism. Nitrogenase activity was partially expressed in NH4Cl-grown cultures. Increasing the level of nitrogenase activity to a value representative of a N2-grown culture required both the inhibition of ammonia assimilation and de novo protein synthesis. An increase in the number of mature heterocysts was not required. The fact that high levels of exogenous ammonia only partially repress the synthesis of proteins required for the maximum expression of nitrogenase activity in Anabaena sp. CA has important implications.

Ammonia↗
PubMed1996

Integration host factor amplifies the induction of the aceBAK operon of Escherichia coli by relieving IclR repression.

A binding site for integration host factor (IHF) was identified upstream of the aceBAK promoter. Under inducing conditions, IHF activates aceB::lacZ expression by opposing IclR repression. In contrast, IHF has little effect on aceB::lacZ expression under repressing conditions. The ability of IHF to relieve repression under inducing but not repressing conditions allows this protein to amplify the induction of aceBAK.

Acetates↗
PubMed2001

The wide-domain carbon catabolite repressor CreA indirectly controls expression of the Aspergillus nidulans xlnB gene, encoding the acidic endo-beta-(1,4)-xylanase X(24).

The Aspergillus nidulans xlnB gene, which encodes the acidic endo-beta-(1,4)-xylanase X(24), is expressed when xylose is present as the sole carbon source and repressed in the presence of glucose. That the mutation creA(d)30 results in considerably elevated levels of xlnB mRNA indicates a role for the wide-domain repressor CreA in the repression of xlnB promoter (xlnBp) activity. Functional analyses of xlnBp::goxC reporter constructs show that none of the four CreA consensus target sites identified in xlnBp are functional in vivo. The CreA repressor is thus likely to exert carbon catabolite repression via an indirect mechanism rather than to influence xlnB expression by acting directly on xlnB.

Aspergillus nidulans↗
PubMed2002

Estrogen receptor-mediated repression of human hepatic lipase gene transcription.

Estrogen replacement therapy in women decreases hepatic lipase (HL) activity, which may account for the associated increase in HDL cholesterol. To investigate whether estrogen decreases HL transcription, transient cotransfection assays with HL promoter and estrogen receptor-alpha (ERalpha) expression constructs were performed in HepG2 cells. 17beta-estradiol (E(2)) decreased transcription driven by the -1557/+41 human HL promoter by up to 50% at 10(-7) M. Mutation of ERalpha by deletion of its transactivation domains or ligand-binding domain eliminated E(2)-induced repression of the promoter, whereas deletion of the DNA-binding domain of ERalpha resulted in a 7-fold activation by E(2). The E(2)-induced repression was maintained after mutation of a potential estrogen-response element in the promoter. The region of estrogen responsiveness was localized to -1557/-1175 of the HL promoter by deletion analysis. Mutation of an AP-1 site at -1493 resulted in a partial loss of E(2)-induced repression, similar to that caused by deletion of nucleotides -1557 to -1366. Gel shift assays with nuclear extracts from E(2)-treated HepG2 cells stably expressing ERalpha demonstrated an increase in binding to an AP-1 consensus oligonucleotide. The AP-1 activator, phorbol 12-myristate 13-acetate, inhibited the HL promoter by greater than 50%. Collectively, the data suggest that estrogen represses the transcription of the HL gene, possibly through an AP-1 pathway.

5' Untranslated Regions↗
PubMed1991

Spontaneous mutations changing the raffinose metabolism of Lactobacillus plantarum.

Lactobacillus plantarum ATCC 8014 grew poorly on raffinose agar plates, but large mutant colonies appeared in high frequency from a thin film of background growth. The alpha-galactosidase and beta-galactosidase activities of L. plantarum ATCC 8014 and a mutant strain were studied in static cultures and pH-controlled fermenter cultures. Both alpha-galactosidase and beta-galactosidase production were inducible in the parental strain; the induction was not needed in the mutant. The alpha-galactosidase activity of both strains was repressed by glucose but not by alpha-methyl-D-glucoside. The mutant phenomenon might be an obstacle in connection to traditional Lactobacillus identification by means of carbohydrate fermentation.

Colony Count, Microbial↗
PubMed1998

Repression of the mouse M-lysozyme gene involves both hindrance of enhancer factor binding to the methylated enhancer and histone deacetylation.

In many cases, gene repression mediated by CpG methylation has been demonstrated. Two different mechanisms have been postulated to explain the repressive effect of methylated CpG DNA: establishment of a repressive chromatin configuration and inhibition of DNA binding of transactivating factors. Using the M-lysozyme gene, we analyzed gene expression, CpG demethylation and the in vivo formation of enhancer/protein complexes after inducing demethylation or inhibiting histone deacetylases. We show that trans-cription of a methylated and silent mouse M-lysozyme gene can be induced upon the inhibition of histone deacetylases in the absence of demethylation or in vivo transactivating factor binding to the enhancer. In contrast, DNA demethylation induces both gene activity as well as enhancer complex formation. Therefore, both mechanisms play a role in lysozyme gene repression mediated by methylated DNA: (i) the enhancer cannot be loaded with transacting factors; and (ii) histone deacetylation inhibits transcription.

Acetylation↗
PubMed1975

Regulation of the hut operons of Salmonella typhimurium and Klebsiella aerogenes by the heterologous hut repressors.

In merodiploid strains of Klebsiella aerogenes with chromosomal hut genes of K. aerogenes and episomal hut genes of Salmonella typhimurium, the repressor of either species can regulate the hut operons of the other species. The repression exerted by the homologous repressor on the left-hand hut operon is, in both organisms, stronger than that exerted by the heterologous repressor.

Cell-Free System↗
PubMed1997

L-cysteine biosynthesis in Bacillus subtilis: identification, sequencing, and functional characterization of the gene coding for phosphoadenylylsulfate sulfotransferase.

Random Tn917 mutagenesis of Bacillus subtilis followed by selection of lipoic acid auxotrophs led to the isolation of the cysH gene. The gene was sequenced and found to encode a phosphoadenylylsulfate sulfotransferase with a molecular mass of 27 kDa. Expression of lacZ fused to the cysH promoter was repressed by cysteine and sulfide and induced by sulfur limitation, indicating that cysH is controlled at the level of transcription.

Amino Acid Sequence↗
PubMed2002

Loss of catabolite repression function of HPr, the phosphocarrier protein of the bacterial phosphotransferase system, affects expression of the cry4A toxin gene in Bacillus thuringiensis subsp. israelensis.

HPr, the phosphocarrier protein of the bacterial phosphotransferase system, mediates catabolite repression of a number of operons in gram-positive bacteria. In order to participate in the regulatory process, HPr is activated by phosphorylation of a conserved serine-46 residue. To study the potential role of HPr in the regulation of Cry4A protoxin synthesis in Bacillus thuringiensis subsp. israelensis, we produced a catabolite repression-negative mutant by replacing the wild-type copy of the ptsH gene with a mutated copy in which the conserved serine residue of HPr was replaced with an alanine. HPr isolated from the mutant strain was not phosphorylated at Ser-45 by HPr kinase, but phosphorylation at His-14 was found to occur normally. The enzyme I and HPr kinase activities of the mutant were not affected. Analysis of the B. thuringiensis subsp. israelensis mutant harboring ptsH-S45A in the chromosome showed that cry4A expression was derepressed from the inhibitory effect of glucose. The mutant strain produced both cry4A and sigma(35) gene transcripts 4 h ahead of the parent strain, but there was no effect on sigma(28) synthesis. In wild-type B. thuringiensis subsp. israelensis cells, cry4A mRNA was observed from 12 h onwards, while in the mutant it appeared at 8 h and was produced for a longer period. The total amount of cry4A transcripts produced by the mutant was higher than by the parent strain. There was a 60 to 70% reduction in the sporulation efficiency of the mutant B. thuringiensis subsp. israelensis strain compared to the wild-type strain.

Bacillus thuringiensis↗
PubMedDate not supplied

[Mechanism of action of glucose on L-asparaginase synthesis by Escherichia coli bacteria].

The synthesis of L-asparaginase in Escherichia coli W and E. coli K-12 was almost completely supressed if glucose was added at a concentration of 0.5 per cent to a growth medium. The level of L-asparaginase synthesis decreased by ca. 75 per cent as a result of cyamutations when the bacteria could not produce cyclo-3',5'-AMP (cAMP). Apparently, a decrease in the intracellular content of cAMP caused by glucose could not be the only factor inhibiting L-asparaginase synthesis. Lactate was found to stimulate L-asparaginase synthesis. Glucose caused the catabolite repression and catabolite inhibition of the components of a system involved in lactate transport. The inhibition of L-asparaginase synthesis by glucose seems to be due, at least partly, to the fact that it prevents the assimilation of lactate by the cells, as well as the utilization of some other compounds which stimulate synthesis of this enzyme.

Asparaginase↗
PubMed1982

Effect of nifA gene product on expression of lacZ under nifH promoter in Escherichia coli.

Gene expression of the nitrogen fixation system from Klebsiello pneumonice was studied in Escherichia coli by using compatible plasmids as vectors. One constructed plasmid carried the nifH promoter fused to the structural gene for beta-galactosidase, lac Z. Another plasmid carried the promoter of a tetracycline-resistance gene fused to nifA. We found that anaerobic synthesis of beta-galactosidase was greatly enhanced by the presence of an active nifA gene, indicating that its product is a positive control factor for transcription of nifH. In addition, anaerobic expression of lacZ was repressed by ammonium or serine in the presence of nifA. Thus the regulatory mechanism under study is of physiological relevance.

Ammonia↗
PubMed1975

Factors influencing the formation and stability of D-glucoside 3-dehydrogenase activity in cultures of Agrobacterium tumefaciens.

D-glucoside 3-dehydrogenase specific activity in Agrobacterium tumefaciens was maximal towards the end of the exponential growth phase of batch cultures; over 90% of the activity disappeared within the next 15 h. Manganese ions, although essential for growth of the organism, strongly repressed D-glucoside 3-dehydrogenase synthesis in sucrose medium but had little effect when the carbon source was methyl alpha-D-glucoside. D-Glucoside 3-dehydrogenase activity increased linearly with increasing specific growth rate in chemostat cultures limited by carbon, nitrogen, phosphate or manganese when methyl alpha-D-glucoside was the carbon source. High enzyme activity was found with sucrose as carbon source only when the growth medium was manganese-limited. D-Glucoside 3-dehydrogenase activity disappeared from A. tumefaciens incubated in carbon- and nitrogen-free medium or in nitrogen-free medium containing succinate, but on continued incubation the activity returned and was then stable. The recovery of activity could be prevented by chloramphenicol or erythromycin. Bacteria containing the recovered dehydrogenase activity could not convert sucrose to 3-ketosucrose when oxygen acted as the terminal electron acceptor, but produced 3-ketosucrose at the normal rate in the presence of ferricyanide. D-Glucoside 3-dehydrogenase activity disappeared irreversibly from bacteria incubated in nitrogen-free medium containing sucrose. Loss of activity followed first order kinetics in bacteria taken from nitrogen-, phosphate- or manganese-limited chemostat steady states; an accelerating rate of decay occurred in cells grown under carbon-limitation. 8-Hydroxyquinoline, chloramphenicol, erythromycin, 2,4-dinitrophenol and manganese ions could reduce the rate of decay.

Alcohol Oxidoreductases↗
PubMed1993

Combined purification of actinomycin synthetase I and 3-hydroxyanthranilic acid 4-methyltransferase from Streptomyces antibioticus.

Actinomycin synthetase I, which activates the precursor of the chromophore of actinomycin, has been purified nearly 1000-fold from extracts of Streptomyces antibioticus. The enzyme has an M(r) of 45,000 and appears to function as a single polypeptide chain. The formation of the enzyme is repressed when S. antibioticus mycelium is grown on glucose as a carbon source. Several benzoic acid derivatives, including intermediates in the putative pathway for actinomycin biosynthesis, were capable of supporting ATP-pyrophosphate exchange catalyzed by actinomycin synthetase I. Interestingly, three synthetic phenoxaziones also functioned as substrates in the exchange reaction. It proved possible to purify a second enzyme involved in actinomycin biosynthesis, 3-hydroxyanthranilic acid 4-methyltransferase, from the same extracts prepared for the purification of actinomycin synthetase I and by similar procedures. Streptomyces lividans, previously shown to contain a silent gene for the enzyme phenoxazione synthase, apparently does not contain a silent pathway for the complete synthesis of actinomycin since neither actinomycin synthetase I nor the methyltransferase could be detected in strains containing a cloned sequence that activates phenoxazione synthase expression.

Electrophoresis, Polyacrylamide Gel↗
PubMed1983

Pleiotropic mutations regulating resistance to glucose repression in Saccharomyces carlsbergensis are allelic to the structural gene for hexokinase B.

Previously, we described a mutation glr1-1 in Saccharomyces carlsbergensis which pleiotropically relieves the synthesis of the following enzymes from glucose repression: maltase, galactokinase, alpha-galactosidase, NADH:cytochrome c reductase, and cytochrome c oxidase (C. A. Michels and A. Romanowski, J. Bacteriol, 143:674-679, 1980.) In this report, we demonstrate that glr1-1 and two other alleles, glr1-3 and glr1-16, are also insensitive to the glucose repression of invertase synthesis. Determinations of the levels of hexokinase activity and the rate of glucose transport in these mutants show that both are reduced as compared with the parent strain. Complementation tests and genetic analysis indicate that the glr1 mutations are allelic to HXK2, the structural gene for hexokinase B. The significance of this result is discussed with regard to the mechanism of glucose repression in S. carlsbergensis.

Alleles↗
PubMed1980

Analysis of regulation of Klebsiella pneumoniae nitrogen fixation (nif) gene cluster with gene fusions.

Gene fusions in which the lac genes are under the control of each promoter in the Klebsiella pneumoniae, nitrogen fixation (nif) gene cluster have been constructed. These fusions have been used to examine positive control of the cluster and the response of individual genes to repression by ammonia and oxygen. De-repression of nif transcriptional units is coordinate and molybdate is required for maximal expression of the structural gene operon, which is autogenously regulated.

Ammonia↗