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At least 145 records · Page 8Linked to original sources

PubMed1993

Molecular analysis of the phoH gene, belonging to the phosphate regulon in Escherichia coli.

By making operon fusions with lambda placMu53, we identified, cloned, and analyzed the phoH gene belonging to the phosphate (pho) regulon. We mapped the phoH gene at 23.6 min in the Escherichia coli genomic library (Y. Kohara, K. Akiyama, and K. Isono, Cell 50:495-508, 1987). Its nucleotide sequence revealed an open reading frame of 354 amino acids which contains sequences for nucleotide-binding motifs. From comparison of the DNA sequences, phoH was found to be identical to psiH, which had been identified as a phosphate starvation-inducible gene (W.W. Metcalf, P.M. Steed, and B.L. Wanner, J. Bacteriol. 172:3191-3200, 1990). The PhoH protein was overproduced by the T7 promoter system, identified as a protein of about 39 kDa, and purified. The amino-terminal amino acid sequence of the PhoH protein agreed with the one deduced from the DNA sequence. We demonstrated that PhoH has an ATP-binding activity by a photoaffinity labeling experiment. Two transcriptional initiation sites (P1 and P2) were identified by S1 nuclease mapping. The upstream P1 promoter contains a pho box, the conserved sequence shared by the pho regulon genes. The region containing the pho box was bound by PhoB protein, the transcriptional activator of the pho regulon, as revealed by footprinting. Regulation of phoH expression in vivo was studied by constructing plasmids containing transcriptional fusions of the phoH promoters with a promoterless gene for chloramphenicol acetyltransferase. Transcription from the P1 promoter required the phoB function and was induced by phosphate limitation, while transcription from the P2 promoter was independent of phoB and constitutive under tested conditions.

Affinity Labels↗

PubMed1996

Phosphoribosyl diphosphate synthetase-independent NAD de novo synthesis in Escherichia coli: a new phenotype of phosphate regulon mutants.

Phosphoribosyl diphosphate-lacking (delta prs) mutant strains of Escherichia coli require NAD, guanosine, uridine, histidine, and tryptophan for growth. NAD is required by phosphoribosyl diphosphate-lacking mutants because of lack of one of the substrates for the quinolinate phosphoribosyltransferase reaction, an enzyme of the NAD de novo pathway. Several NAD-independent mutants of a host from which prs had been deleted were isolated; all of them were shown to have lesions in the pstSCAB-phoU operon, in which mutations lead to derepression of the Pho regulon. In addition NAD-independent growth was dependent on a functional quinolinate phosphoribosyltransferase. The prs suppressor mutations led to the synthesis of a new phosphoryl compound that may act as a precursor for a new NAD biosynthetic pathway. This compound may be synthesized by the product of an unknown phosphate starvation-inducible gene of the Pho regulon because the ability of pst or phoU mutations to suppress the NAD requirement requires PhoB, the transcriptional activator of the Pho regulon.

Escherichia coli↗

PubMed1996

The monoamine regulon including syntheses of arylsulfatase and monoamine oxidase in bacteria.

Bacterial cells respond to monoamine compounds, such as tyramine, dopamine, octopamine, or norepinephrine, and induce the syntheses of tyramine oxidase encoded by tynA and monoamine oxidase encoded by maoA. These monoamine compounds also derepress the synthesis of atsA-specified arylsulfatase that is repressed by sulfur compounds. These complex mechanisms of regulons regulated by monoamine and sulfur compounds has been analyzed by cloning and characterization of genes that are involved in the repression and derepression of the synthesis of arylsulfatase. The atsA gene forms an operon with the atsB gene, which encodes an activator of the expression of atsA. The negative regulator gene for arylsulfatase was found to code for dihydrofolate reductase (folA). The maoA gene forms an operon with the maoC gene, which has similarity to a dehydrogenase involved in the tyramine metabolism. The moaF gene encoding a 30-kDa protein, which is induced by tyramine, also forms an operon with the moaE gene. Finally, the moaR gene, which is induced by monoamine, was found to play a central role in the positive regulation of the expression of the monoamine regulon (moa) including the atsBA, maoCA, moaEF, and tyn operons. The moaR expression is subject to autogenous regulation and to cAMP-CRP control. The MoaR protein has a helix-turn-helix motif in its C terminus. Thus, the MoaR protein probably regulates the operons by binding to the regulatory region of the moa regulon.

Arylsulfatases↗

PubMed2006

[Regulon in the treatment of hyperandrogenism in teenage girls].

UNLABELLED: The aim of study was to assess the efficiency of the use of combined oral contraceptive with dezogestrel-regulon in the treatment of hyperandrogenism in teenage girls. 14-18 y.o. girls with signs of hyperandrogenism have been investigated. Investigation included: physical examination, assessment of body mass, hirsute number, ultrasonography, FSH, LH, prolactin, testosterone, 17 OH progesterone in blood. RESULTS: All the patients received Regulon from the 5th up to 21st day of menstrual cycle during 6 months. After the 6 months of treatment the regulation of menstrual cycle have been registered in 91% of patients. Reduction of hirsute number (from 24.1+/-1.0 to 11.0+/-1.2 ), ovarian volume by ultrasound (from 16.7+/-3.0 sm(3) to 7.1+/-0.9 sm(3)), level of LH (from 12.7+/-2.4 to 8.0+/-1.2 IU/L) and testosterone (from 4.2 +/-0.2 to 2.8+/-0.6 nmol/l) were registered. Regulon is effective for the treatment of hyperandrogenism in teenage girls.

Adolescent↗

PubMed1991

Purification and characterization of the Escherichia coli OxyR protein, the positive regulator for a hydrogen peroxide-inducible regulon.

The Escherichia coli oxyR gene is required for the induction of a regulon that is inducible by hydrogen peroxide and confers resistance to oxidative stresses. We constructed a plasmid system that greatly overproduced OxyR protein and purified the protein. OxyR protein specifically bound to the upstream regulatory regions of the oxyR and katG genes as demonstrated by the gel-retardation assay and the DNase I footprinting experiment, and activated the transcription initiation of the katG gene in vitro. Using a plasmid carrying an oxyR'-'lacZ fusion gene, we studied the regulation of oxyR expression in vivo. The expression of oxyR was not induced by the treatment with a low concentration of hydrogen peroxide which induces the genes in the oxyR regulon. The expression of the oxyR'-'lacZ gene was higher in an oxyR-deletion strain than in the oxyR+ strain, and was repressed by overexpressing the OxyR protein. These results suggest that OxyR protein functions as a repressor for oxyR, in addition to its known function as a transcriptional activator for the genes in the oxyR regulon.

Bacterial Proteins↗

PubMed1988

Induction of the manganese-containing superoxide dismutase in Escherichia coli is independent of the oxidative stress (oxyR-controlled) regulon.

The synthesis of manganese-superoxide dismutase in response to hydrogen peroxide and to paraquat was examined in strains of Escherichia coli with different mutations in the oxyR gene. Hydrogen peroxide treatment did not induce manganese-superoxide dismutase, but did induce the oxyR regulon. Paraquat induced this enzyme in a strain compromised in its ability to induce the defense response against oxidative stress (oxyR deletion) as well as in a strain that is constitutive and overexpresses the oxyR regulon. Catalase (HPI), but not manganese-superoxide dismutase, was over-expressed under anaerobic conditions in a strain harboring a constitutive oxyR mutation. The data clearly demonstrate that the induction of manganese-superoxide dismutase is independent of the oxyR-controlled regulon.

Anaerobiosis↗

PubMed2001

Transcription of the ibpB heat-shock gene is under control of sigma(32)- and sigma(54)-promoters, a third regulon of heat-shock response.

The expression of the ibpAibpB heat-shock operon of Escherichia coli was found previously not to conform to the known pattern of expression of the sigma(32)-regulated operons because the rpoH gene mutation inactivating the sigma(32) protein did not abolish the ibp induction. We show here that this effect can depend partly on the sigma(54)-promoter that is inducible by heat shock, located upstream of the ibpB, the distal gene of the operon. It may also depend on a metabolic signal, postulated by others, and possibly required for the expression of the ibpAB genes. Thus, the ibpB gene can be translated from the transcript covering the whole operon starting from the sigma(32)-promoter and from the ibpB gene transcript starting from the sigma(54)-promoter. These results indicate that the ibpB gene is a second member of the sigma(54)-heat-shock regulon in E. coli besides pspA-E operon. Thus, heat-shock response involves three regulons controlled by sigma(32), sigma(24), and sigma(54) RNA polymerase subunits.

Bacterial Proteins↗

PubMed2003

The ssgB gene, encoding a member of the regulon of stress-response sigma factor sigmaH, is essential for aerial mycelium septation in Streptomyces coelicolor A3(2).

The Streptomyces coelicolor A3(2) gene ssgB belongs to the regulon of stress-response sigma factor sigmaH. By integrative transformation via double cross-over, a stable null mutant of ssgB was obtained. This mutation had no obvious effect on vegetative growth, but critically affected aerial mycelium septation. The S. coelicolor ssgB mutant produced aerial hyphae without any signs of septation into spore compartments. The mutation was complemented in trans by wild-type ssgB including the sigmaH-dependent ssgBp promoter. The results proved that ssgB belongs a developmental branch of the sigmaH regulon.

Bacterial Proteins↗

PubMedDate not supplied

Analysis of the expression and function of the sigmaB-dependent general stress regulon of Bacillus subtilis during slow growth.

Glucose-limited continuous cultures were used to analyze sigmaB activity at decreasing growth rates. Expression of the sigmaB-dependent genes gsiB and ctc started to increase at a growth rate of 0.2 h-1, and both genes were induced approximately fivefold at a growth rate of 0.1 h-1 as compared to expression at the maximal growth rate. However, maximal sigmaB activity was only reached when the growth stopped as a result of the exhaustion of the carbon and energy source glucose. During glucose-limited growth, increased expression of the general stress regulon at growth rates below 0.2 h-1 did not provide wild-type cells with a growth advantage over sigB mutants. Instead, expression of the stress regulon seems to constitute a significant burden during glucose-limited growth, resulting in a selective growth advantage of the sigB mutant as compared to the wild-type at a growth rate of 0.08 h-1.

Bacillus subtilis↗

PubMed2000

Induction of the cysteine regulon of Salmonella typhimurium in LB medium affects the response of cysB mutants to mecillinam.

Rapid growth of Salmonella typhimurium LT2 in rich LB-broth caused the induction of the cysteine regulon when the culture reached an optical density at 650 nm of 1.5. Addition of 0.05 mM L-cystine to LB-broth abolished induction, while 0.025 mM L-cystine delayed it for a doubling time (30 min). Induction did not occur when lack of oxygen or a temperature shift to 19 degrees C slowed down growth in LB-broth. Uninduced cultures reached growth yield similar to that of induced cultures after overnight incubation. Growth on solid LB-medium also brought about induction, but to a lower level than in liquid medium. Leaky cysB mutants, which are sensitive to the beta-lactam antibiotic mecillinam, displayed partial induction, whereas mecillinam-resistant cysB and cysE mutants showed no induction. It is suggested that induction develops in these mutants when constitutive transport systems fail to satisfy the high uptake of cysteine demanded by fast-growing cultures. The behavior of cysB mutants agrees with the hypothesis that, under some conditions, mecillinam action would be dependent on expression of the cysteine regulon.

Amdinocillin↗

PubMed2006

Pdc2 coordinates expression of the THI regulon in the yeast Saccharomyces cerevisiae.

Coordination of gene expression in response to different metabolic signals is crucial for cellular homeostasis. In this work, we addressed the role of Pdc2 in the coordinated control of biosynthesis and demand of an essential metabolic cofactor, thiaminediphosphate (ThDP). The DNA binding protein Pdc2 was initially identified as a regulator of the genes PDC1 and PDC5, which encode isoforms of the glycolytic enzyme pyruvate decarboxylase (Pdc). The Pdc2 has also been implicated as a regulator of genes encoding enzymes in ThDP metabolism. The ThDP is the cofactor of Pdc. Using global and gene-specific expression analysis, we show that Pdc2 is required for the upregulation of all genes controlled by thiamine availability. The Pdc2 seems to act together with Thi2, a known transcriptional regulator of THI genes. The requirement for these two factors differs in a gene-specific manner. While the Thi2, in conjunction with Thi3, seems to control expression of THI genes with respect to thiamine availability, the Pdc2 may link the ThDP demand to carbon source availability. Interestingly, the enzymes Pdc1 and Pdc5 are enriched in the nucleus. Both are known to affect gene expression in an autoregulatory mechanism and expression of both is regulated by glucose and Pdc2, further pointing to a role of Pdc2 in coordinating different metabolic signals. Our analysis helps to further define the THI regulon and hence the spectrum of genes/proteins involved in the ThDP homeostasis. In particular, we identify novel proteins putatively involved in thiamine and/or ThDP transport across the plasma and the mitochondrial membrane. In conclusion, the THI regulon is the most interesting system to study principles of genes expression and metabolic coordination and deserves further attention.

Biological Transport↗

PubMed2005

Hydrogen peroxide increases the activities of soxRS regulon enzymes and the levels of oxidized proteins and lipids in Escherichia coli.

The effects of hydrogen peroxide treatments on Escherichia coli KS400 and AB1157 cells were assessed by monitoring the accumulation of oxidative damage products, carbonyl proteins and thiobarbituric acid-reactive substances (TBARS), as well as the activities of selected antioxidant enzymes. H(2)O(2) treatment stimulated increases in both TBARS and carbonyl protein levels in dose- and time-dependent manners in KS400 cells. The accumulation of TBARS was much more variable with H(2)O(2) treatment; TBARS content was significantly increased in response to 5 microM H(2)O(2), whereas a significant increase in carbonyl protein content occurred at 100 microM H(2)O(2). Similarly, treatment with 20 microM hydrogen peroxide for different lengths of time resulted in peak TBARS accumulation by 20 min, whereas carbonyl protein levels were significantly elevated only after 60 min. In AB1157 cells, treatment with 20 microM hydrogen peroxide for 20 min led to strong increases in both carbonyl protein and TBARS levels. This treatment also triggered increased activities of enzymes of the oxyR regulon (catalase, peroxidase, and glutathione reductase) in both strains. In the AB1157 strain, H(2)O(2) exposure also increased the activities of two enzymes of the soxRS regulon (superoxide dismutase and glucose-6-phosphate dehydrogenase) by 50-60%. The data show differential variability of lipids versus proteins to oxidative damage induced by H(2)O(2,) as well as strain-specific differences in the accumulation of damage products and the responses by antioxidant enzymes to H(2)O(2) stress.

Bacterial Proteins↗

PubMed2003

Two membrane proteins located in the Nag regulon of Candida albicans confer multidrug resistance.

Pathogenic fungus Candida albicans can efficiently utilize the aminosugar N-acetylglucosamine (GlcNAc) as energy source. Since the mucosal membrane, the site of infection is rich in amino sugars, this specific adaptation is important for the establishment of infection. The genes encoding for the enzymes of the GlcNAc catabolic pathway, GlcNAc kinase (HXK1), GlcNAc-6-phosphate deacetylase (DAC1), and glucosamine-6-phosphate deaminase (NAG1), are present in a cluster, the Nag regulon, which is associated with virulence. In this study, we have characterized two genes, TMP1 and TMP2, present within the Nag regulon, upstream to DAC1. They encode two membrane associated sugar transporters of the major facilitator superfamily (MFS). The null mutant of TMP1 and TMP2 is able to grow in GlcNAc, implying that they are not involved in GlcNAc transport. However, it shows increased susceptibility to a number of unrelated antifungal compounds such as cycloheximide, 4-nitroquinoline-N-oxide, and 1-10 phenanthroline. Northern blot analysis revealed that TMP1 and TMP2 are upregulated in response to these drugs, suggesting that they function as multiple drug efflux pumps.

Acetylglucosamine↗

PubMed2002

Regulation of the Escherichia coli allantoin regulon: coordinated function of the repressor AllR and the activator AllS.

The allantoin regulon of Escherichia coli, formed by three operons expressed from promoters allA(P), gcl(P) and allD(P), is involved in the anaerobic utilization of allantoin as nitrogen source. The expression of these operons is under the control of the repressor AllR. The hyperinduction of one of these promoters (allD(P)) by allantoin in an AllR defective mutant suggested the action of another regulator, presumably of activator type. In this work we have identified ybbS (proposed gene name allS), divergently transcribed from allA, as the gene encoding this activator. Analysis of the expression of the three structural operons in DeltaallS mutant showed that the expression from allD(P) was abolished, suggesting that AllS is essential for the expression of the corresponding operon. In a wild-type strain expression of allS takes place mainly anaerobically and is hyperinduced when the nitrogen source limits growth. However, expression of allS is independent of regulators of the Ntr response, NtrC or Nac. Band shift experiments showed that AllR binds to DNA containing the allS-allA intergenic region and the gcl(P) promoter and its binding is abolished by glyoxylate. Both DNA fragments contain a highly conserved inverted repeat, which after site-directed mutagenesis, has been proven to be the AllR-binding site. This site displays similarity with the IclR family recognized consensus. Interaction of AllR with the single operator present in the allS-allA intergenic region prevented binding of RNA polymerase to either of the two divergent promoters. The regulator AllS interacts only with allD(P) even in the absence of allantoin. Analysis of this promoter allowed us to identify an inverted repeat as a motif for AllS binding. We propose a model for the coordinate control of the allantoin regulon by AllR and AllS.

Allantoin↗

PubMed1996

Redox signaling and gene control in the Escherichia coli soxRS oxidative stress regulon--a review.

The soxRS regulon of Escherichia coli coordinates the induction of at least twelve genes in response to superoxide or nitric oxide. This review describes recent progress in understanding the signal transduction and transcriptional control mechanisms that activate the soxRS regulon, and some aspects of the physiological functions of this system. The SoxS protein represents a growing family of transcription activators that stimulate genes for resistance to oxidative stress and antibiotics. SoxR is an unusual transcription factor whose activity in vitro can be switched off by the removal of [2Fe-2S] centers, and activated by their reinsertion. The activated form of SoxR remodels the structure of the soxS promoter to activate transcription. When the soxRS system is activated, bacteria gain resistance to oxidants, antibiotics and immune cells that generate nitric oxide. The latter features could increase the success (virulence) of some bacterial infections.

Bacterial Proteins↗

PubMed1998

PhoP-P and RNA polymerase sigmaA holoenzyme are sufficient for transcription of Pho regulon promoters in Bacillus subtilis: PhoP-P activator sites within the coding region stimulate transcription in vitro.

The Bacillus subtilis pstS operon and phoA gene are members of the Pho regulon that is controlled by PhoR, a histidine kinase, and PhoP, a response regulator. Footprinting analysis showed that phosphorylated PhoP extended the PhoP protected region in pstS and phoA promoters, and also bound to a separate site within the coding region of each gene. Our previous in vivo studies have shown that, in contrast to other Pho regulon promoters that are not expressed in either phoP or phoR mutants, a low-level induction from the pstS promoter (25% of parent strain) can be detected in a phoR mutant. In this study, by using an in vitro transcription system, we demonstrate that (i) only phosphorylated PhoP is a transcriptional activator of the pstS operon and of the phoA gene; (ii) phosphorylated PhoP and RNA polymerase sigmaA holoenzyme are sufficient for in vitro transcription of the pstS promoter and the phoA promoter; (iii) the activation of the pstS promoter requires lower concentrations of phosphorylated PhoP than does the phoA promoter for transcription; and (iv) PhoP binding sites in both the pstS promoter core binding region and in the 5' coding region of the gene, which have been identified by footprinting analysis, are important for the transcription of the pstS promoter in vitro.

Alkaline Phosphatase↗

PubMed1998

Bacillus subtilis contains multiple Fur homologues: identification of the iron uptake (Fur) and peroxide regulon (PerR) repressors.

Fur (ferric uptake regulator) proteins control iron uptake in many Gram-negative bacteria. Although Fur homologues have been identified in Gram-positive bacteria, their roles in gene regulation are unknown. Genome sequencing has revealed three fur homologues in Bacillus subtilis: yqkL, yqfV and ygaG. We demonstrate that yqkL encodes an iron uptake repressor: both siderophore biosynthesis and transcription of ferri-siderophore uptake genes is constitutive in the yqkL mutant. Thus, yqkL encodes a repressor that is functionally as well as structurally related to Fur. B. subtilis peroxide stress genes are induced by either H2O2 or by metal ion limitation. Previous genetic studies defined a regulatory locus, perR, postulated to encode the peroxide regulon repressor. We demonstrate that a ygaG mutant has the perR phenotype: It is highly resistant to peroxides and overexpresses catalase, alkyl hydroperoxide reductase and the DNA binding protein MrgA. Nine spontaneous perR mutations, isolated by virtue of their ability to derepress mrgA transcription in the presence of managanous ion, all contain sequence changes in the ygaG locus and can be complemented by the cloned ygaG gene. Thus, ygaG encodes the peroxide regulon repressor and is allelic with perR.

Amino Acid Sequence↗

PubMed1999

The heat shock response in yeast: differential regulations and contributions of the Msn2p/Msn4p and Hsf1p regulons.

The heat shock transcription factor Hsf1p and the stress-responsive transcription factors Msn2p and Msn4p are activated by heat shock in the yeast Saccharomyces cerevisiae. Their respective contributions to heat shock protein induction have been analysed by comparison of mutants and wild-type strains using [35S]-methionine labelling and two-dimensional gel electrophoresis. Among 52 proteins induced by a shift from 25 degrees C to 38 degrees C, half of them were found to be dependent upon Msn2p and/or Msn4p (including mostly antioxidants and enzymes involved in carbon metabolism), while the other half (including mostly chaperones and associated proteins) were dependent upon Hsf1p. The two sets of proteins overlapped only slightly. Three proteins were induced independently of these transcription factors, suggesting the involvement of other transcription factor(s). The Ras/cAMP/PKA signalling pathway cAMP had a negative effect on the induction of the Msn2p/Msn4p regulon, but did not affect the Hsf1p regulon. Thus, the two types of transcription factor are regulated differently and control two sets of functionally distinct proteins, suggesting two different physiological roles in the heat shock cellular response.

Cyclic AMP↗