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PubMed1976

Mitochondrial adenosine triphosphatase of the fission yeast, Schizosaccharomyces pombe 972h-. Changes in activity and inhibitor-sensitivity in response to catabolite repression.

1. The specific activity of mitochondrial ATPase (adenosine triphosphatase) in extracts of Schizosaccharomyces pombe decreased 2.5-fold as the glucose concentration in the growth medium decreased from 50mM to 15mM. 2. During the late exponential phase of growth, ATPase activity doubled. 3. Sensitivity to oligomycin and Dio-9 as measured by values for I50(mug of inhibitor/mg of protein giving 50% inhibition) at pH 6.8 increased sixfold and ninefold respectively during the initial decrease in ATPase activity, and this degree of sensitivity was maintained for the remainder of the growth cycle. 4. Increased sensitivity to NN'-dicyclohexylcarbodi-imide, triethyltin and venturicidin was also observed during the early stage of glucose de-repression. 5. Smaller increases in sensitivity to efrapeptin, aurovertin, 7-chloro-4-nitrobenzo-2-oxa-1,3-diaz-le, quercetin and spegazzinine also occurred. 6. The ATPase of glycerol-grown cells was less sensitive to inhibitors than that of glucose-repressed cells; change in values for I50 were not so marked during the growth cycle of cells growing with glycerol. 7. When submitochondrial particles from glycerol-grown cells were tested by passage through Sephadex G-50, a fourfold increase in activity was accompanied by increased inhibitor resistance. 8. Gel filtration of submitochondrial particles from glucose-de-repressed cells gave similar results, whereas loss of ATPase occurred in submitochondrial particles from glucose-repressed cells. 9. It is proposed that alterations in sensitivity to inhibitors at different stages of glucose derepression may be partly controlled by a naturally occuring inhibitor of ATPase. 10. The inhibitors tested may be classififed into two groups on the basis of alterations of sensitivity of the ATPase during physiological modification: (a) oligomycin, Dio-9, NN'-dicyclohexylcarbodi-imide, venturicidin and triethyltin, and (b) efrapeptin, aurovertin, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, quercetin and spegazzinine.

Adenosine Triphosphatases↗

PubMed1994

Catabolite repression of cellulase biosynthesis in Streptomyces albaduncus.

The cellulase complex of S. albaduncus was found to undergo catabolite repression in the presence of glycerol accompanied by a decrease in the pH of the medium. The results of the experiments conducted at two different initial pH of the medium suggested that pH effect as well as proteases were involved in the inactivation of glucanases (exoglucanase and endoglucanase) whereas beta-glucosidase inactivation was solely due to 'pH effect'. It was also apparent that pH change followed by the addition of glycerol caused alterations in protease activities as well as pattern of their production.

Cellulase↗

PubMed1976

Structural limits of specificity of methylcholanthrene-repressible nitrosamine N-dealkylases. Inhibition by analog substrates.

The dealkylation of dimethyl-, diethyl- and dipropylnitrosamine by hepatic microsomes of Sprague-Dawley rats is repressed by pretreatment of the animals with 3-methylcholanthrene (MC), and this repression progressively decreases with the increase of alkyl chain length. In contrast to its effect on the demethylation of dimethylnitrosamine (DMN), in vivo phenobarbital induces rather than represses the deethylation of diethylnitrosamine. The rates of demethylation of the DMN analog substrates (dimethylformamide, dimethylacetamide, dimethylpropionamide, and dimethylbutyramide), although low as compared to DMN, increase with the acyl chain length. These analogs are potent in vitro inhibitors of Dmn demethylation when used in combination with DMN as substrates, and the inhibition decreases with the length of the acyl chain. Dimethylaminoacetone, which corresponds to the insertion of a CH2 group between the N atom and the carbonyl group in dimethylacetamide, is not an in vitro inhibitor of DMN demethylation; the demethylation rates are additive when theis compound is used as substrate in combination with DMN. The rate of demethylation of dimethylaminoacetone is substantially higher than the rates of the dimethylacylamides, and is significantly repressed by MC-pretreatment. The rate of demethylation of methylphenylnitrosamine is not influenced by MC-pretreatment; the compound is, however, a potent inhibitor of demethylation when used as substrate in combination with DMN. The demethylation rates of 1,1-dimethylhydrazine (the reduction product of DMN) and dimethylaniline are not influenced by MC-pretreatment; neither do they affect the overall rate of demethylation when used as substrate in combination with DMN.

Animals↗

PubMed1987

The effects of ADR1 and CCR1 gene dosage on the regulation of the glucose-repressible alcohol dehydrogenase from Saccharomyces cerevisiae.

The dosage of the transcriptional activator ADR1 was varied in order to study the regulation of the glucose-repressible alcohol dehydrogenase (ADH II) from Saccharomyces cerevisiae. ADH II activity during glucose growth conditions was shown to increase linearly with increasing ADR1 gene dosage. In contrast, under derepressed growth conditions a 100-fold increase in ADR1 copy number resulted in only a 4-fold increase in ADH II expression. Saturation of ADH II gene expression by ADR1 under derepressed conditions was shown not to result from decreased ADR1 transcription. Increases in ADH2 gene dosage in conjunction with high ADR1 gene dosages resulted in increased ADH II activity, indicating that ADH2 was the limiting factor during derepression. Under glucose-repressed conditions the activator CCR1 was not required for ADR1 activity. During derepression increasing ADR1 dosage could partially compensate for a CCR1 defect. Increasing CCR1 gene dosage, however, had no effect on ADH2 expression regardless of the ADR1 allele present. These results suggest that CCR1 acts through ADR1 in controlling ADH2 expression. It was also observed that high numbers of ADR1, or a few copies of ADR1-5c, substantially increased the cell doubling time under ethanol growth conditions, indicating that increased ADR1 activity is toxic.

Alcohol Dehydrogenase↗

PubMed1976

Methionine overproduction by Saccharomycopsis lipolytica.

Six ethionine-resistant (Etr) regulatory mutants of Saccharomycopsis lipolytica Sl/1 overproducing methionine have been isolated. Five of them are also resistant to seleno-methionine. The activity of homocysteine synthase (O-acetyl-L-hormoserine-acetate lyase, adding hydrogen sulfide) is derepressed in these mutants and is not susceptible to the methionine-mediated repression. The pool of free methionine in Etr mutants is enhanced 1.5 to 18 times, and incorporation of 35S into methionine is 1.5 to 50 times higher than that in the wild strain. Neither accumulation of endogenous free methionine in Etr mutants nor the uptake of exogenous methionine is accompanied by an increase in the S-adenosylmethionine pool. This implies compartmentation of methionine metabolism in S. lipolytica.

Ascomycota↗

PubMed1989

Elements involved in S-adenosylmethionine-mediated regulation of the Saccharomyces cerevisiae MET25 gene.

In Saccharomyces cerevisiae, the MET25 gene encodes O-acetylhomoserine sulfhydrylase. Synthesis of this enzyme is repressed by the presence of S-adenosylmethionine (AdoMet) in the growth medium. We identified cis elements required for MET25 expression by analyzing small deletions in the MET25 promoter region. The results revealed a regulatory region, acting as an upstream activation site, that activated transcription of MET25 in the absence of methionine or AdoMet. We found that, for the most part, repression of MET25 expression was due to a lack of activation at this site, reinforced by an independent repression mechanism. The activation region contained a repeated dyad sequence that is also found in the promoter regions of other unlinked but coordinately regulated genes (MET3, MET2, and SAM2). We show that the presence of the two dyads is necessary for maximal gene expression. Moreover, we demonstrate that in addition to this transcriptional regulation, a posttranscriptional regulation, probably targeted at the 5' region of mRNA, is involved in MET25 expression.

Base Sequence↗

PubMed1997

Arginine biosynthesis and regulation in Lactobacillus plantarum: the carA gene and the argCJBDF cluster are divergently transcribed.

A cluster of citrulline biosynthetic genes has been cloned and sequenced from a fragment of Lactobacillus plantarum CCM 1904 (ATCC 8014) DNA isolated as complementing a Bacillus subtilis argF mutation. The gene order was carA-argCJBDF, with carA transcribed divergently from the arg cluster. Although other gram-positive bacteria show similar arg clusters, this arrangement for carA is thus far unprecedented. Downstream from the arg cluster, two open reading frames (ORF7 and ORF8) having unknown functions were found. Sequence analysis of the end of a 10.5-kb cloned DNA fragment showed that argF was 3.5 kb from the ldhL gene coding for L-(+)-lactate dehydrogenase. A tree representation of amino acid sequence clustering relationships of 31 ornithine carbamoyltransferases (OTCases) from various organisms revealed two prokaryotic groups: one with ArgF of L. plantarum and one with ArgF of B. subtilis, which are paralogous. This divergence was not observed in vivo because an L. plantarum argF mutant (AM 1215) harboring no OTCase activity was complemented by the argF genes of L. plantarum and B. subtilis. No OTCase activity was detectable when L. plantarum was grown in the presence of saturating amounts of arginine or citrulline. Arginine may repress the citrulline biosynthetic genes in L. plantarum by using 11 identified DNA motifs which resemble the Escherichia coli ARG box consensus and which are in most cases separated by multiples of 11 bp, corresponding to a DNA helical turn. The carA and argCJBDF genes are divergently transcribed. Their putative promoters are 6 bp apart and are partially overlapped by putative ARG boxes, suggesting concerted transcription regulation.

Arginine↗

PubMed1968

Enzyme pattern and aerobic growth of Saccharomyces cerevisiae under various degrees of glucose limitation.

The enzyme pattern of Saccharomyces cerevisiae was followed during batch growth and in continuous culture in a synthetic medium limited for glucose under aerobic conditions. Seven enzymes were measured: succinate-cytochrome c oxidoreductase, malate dehydrogenase, nicotinamide adenine dinucleotide-linked glutamate dehydrogenase, malate synthase, isocitrate lyase, aldolase, and nicotinamide adenine dinucleotide phosphate (NADP(+))-linked glutamate dehydrogenase. During fermentation of glucose and high growth rate (mu) during the first log phase in batch experiments, the first five enzymes (group I) were repressed, and aldolase and NADP(+)-linked glutamate dehydrogenase (group II) were derepressed. During growth on the accumulated ethyl alcohol and lower mu, the group I enzymes were preferentially formed and the other two were repressed. A sequence of derepression of the group I enzymes was found during the shift from glucose to ethyl alcohol metabolism, which can be correlated with a strong increase in the percentage of single (nonbudding) cells in the population. A correlation between the state of cells in the budding cycle and enzyme repression and derepression is suggested. In continuous culture, the enzyme pattern was shown to be related to the growth rate. The group I enzymes were repressed at high growth rates, while the group II enzymes were derepressed. Each enzyme exhibits a different dependence. The enzyme pattern is shown to depend on the rate of substrate consumption as well as on the type of metabolism and to be correlated with the budding cycle. The enzyme pattern is considered to be controlled by changes of intracellular catabolic or metabolic conditions inherent in the division cycle.

Aldehyde-Lyases↗

PubMed1979

Regulation of melanin production by Cryptococcus neoformans.

Species of Filobasidiella, the agents of cryptococcosis, produced melanin-like pigments within 4 to 48 h with diphenol, aminophenol, and diaminobenzene compounds as substrates. The rate of phenyloxidase activity was found to be regulated by glucose and nitrogen catabolite repression. Increased glucose concentration reduced pigmentation of all serotypes of Filobasidiella, whereas repression by nitrogen sources varied with the strain. Glutamine repressed the phenyloxidases of all isolates except those of serotype B, and (NH4)2SO4 repressed the phenyloxidase of all isolates except that of serotype A. Tyrosine and glycine appeared to be near optimal for phenyloxidase activity but not necessarily for growth of all strain examined. Representatives of serotype C were unique in that their phenyloxidase system was adpative in contrast to the constitutive system found in the other serotypes. No single medium was found to support pigmentation of all strains of Cryptococcus neoformans within a 72-h incubation period; false-negative reactions can occur.

Catechol Oxidase↗

PubMed1973

Phenotypes of pleiotropic-negative sporulation mutants of Bacillus subtilis.

The phenotypic properties of representatives of the five genetic classes of pleiotropic-negative sporulation mutants have been investigated. Protease production, alkaline and neutral proteases, was curtailed in spoA mutants, but the remainder of mutant classes produced both proteases, albeit at reduced levels. The spoA and spoB mutants plaqued phi2 and phi15 at high efficiency, but the efficiency of plating of these phages on spoE, spoF, and spoH mutants was drastically reduced. Antibiotic was produced by the spoH mutants and to a degree by some spoF mutants, but the other classes did not produce detectable activity. The spoA mutants were less responsive to catabolite repression of histidase synthesis by glucose than was the wild type. Severe catabolite repression could be induced in spoA mutants by amino acid limitation, suggesting that the relaxation of catabolite repression observed is not due to a defect in the mechanism of catabolite repression. Although others have shown a perturbation in cytochrome regulation in spoA and spoB mutants, the primary dehydrogenases, succinate dehydrogenase and reduced nicotinamide adenine dinucleotide dehydrogenase, leading to these cytochromes are unimpaired in all mutant classes. A comparison of the structural components of cell walls and membranes of spoA and the wild type is made. The pleiotropic phenotypes of these mutants are discussed.

Amino Acids↗

PubMed1997

Lack of mda-6/WAF1/CIP1-mediated inhibition of cyclin-dependent kinases in interferon-alpha resistant murine B16 melanoma cells.

Previously we demonstrated that IFN-alpha augments mda-6/WAF1 and inhibits cyclin-dependent kinases in a p53-independent fashion in B 16 murine melanoma cells. On the other hand, IFN-gamma activates p53 expression without affecting the mda-6/WAF1 system. Combination of the two IFNs is additive. B16 cells acquire IFN-alpha resistant but IFN-gamma sensitive phenotype after long term IFN-alpha treatment (B16alpha cells). Here we demonstrate the absence of mda-6/WAF1-associated repression of cyclin-dependent kinases, but the existence of p53-dependent c-myc inhibition in IFN-gamma-treated B16alpha cells. Clearly, selective desensitization of IFN-alpha related growth regulation does not influence the IFN-gamma associated pathway. Our results further support the coexistence of distinct growth regulatory mechanisms in B16 cells that can be activated by different IFN-types independently of each other.

Animals↗

PubMed1972

Differential sensitivities of the two malate dehydrogenases and the maltose permease to the effect of glucose in Saccharomyces carlsbergensis.

In Saccharomyces carlsbergensis the two malate dehydrogenase activities, which are localized in different compartments of the cell, were found to differ in their response to glucose. The cytoplasmic malate dehydrogenase activity appears to be sensitive to inactivation by very low concentrations of glucose. The mitochondrial malate dehydrogenase activity is only repressed at a higher glucose concentration. Maltose permease is also sensitive to inactivation by glucose. Conditions were found such that the maltose permease was present while the cytoplasmic malate dehydrogenase was inactivated. The different sensitivities of the two malate dehydrogenases and maltose permease to the effect of glucose may explain the preferential use of glucose, maltose, and products of glucose metabolism (2- and 3-carbon skeletons) as carbon sources for growth in the order as mentioned.

Amino Acids↗

PubMed1980

Transposed LEU2 gene of Saccharomyces cerevisiae is regulated normally.

The repression of beta-isopropylmalate dehydrogenase, the LEU2 gene product, by leucine and leucine plus threonine was unaffected by the transposition of LEU2 from its original locus on chromosome III to a new locus within the ribosomal deoxyribonucleic acid gene cluster on chromosome XII. Since the expression of the LEU2 gene is probably controlled at a pretranslational level, we conclude that the recombinant plasmid used for transformation carries regulatory information in addition to LEU2 structural information.

3-Isopropylmalate Dehydrogenase↗

PubMed1992

Production of the CYS3 regulator, a bZIP DNA-binding protein, is sufficient to induce sulfur gene expression in Neurospora crassa.

The cys-3+ gene of Neurospora crassa encodes a bZIP (basic region-leucine zipper) regulatory protein that is essential for sulfur structural gene expression (e.g., ars-1+). Nuclear transcription assays confirmed that cys-3+ was under sulfur-regulated transcriptional control and that cys-3+ transcription was constitutive in sulfur controller (scon)-negative regulator mutants. Given these results, I have tested whether expression of cys-3+ under high-sulfur (repressing) conditions was sufficient to induce sulfur gene expression. The N. crassa beta-tubulin (tub) promoter was fused to the cys-3+ coding segment and used to transform a cys-3 deletion mutant. Function of the tub::cys-3 fusion in homokaryotic transformants grown under high-sulfur conditions was confirmed by Northern (RNA) and Western immunoblot analysis. The tub::cys-3 transformants showed arylsulfatase gene expression under normally repressing high-sulfur conditions. A tub::cys-3ts fusion encoding a temperature-sensitive CYS3 protein was used to confirm that the induced structural gene expression was due to CYS3 protein function. Constitutive CYS3 production did not induce scon-2+ expression under repressing conditions. In addition, a cys-3 promoter fusion to lacZ showed that CYS3 production was sufficient to induce its own expression and provides in vivo evidence for autoregulation. Finally, an apparent inhibitory effect observed with a strain carrying a point mutation at the cys-3 locus was examined by in vitro heterodimerization studies. These results support an interpretation of CYS3 as a transcriptional activator whose regulation is a crucial control point in the signal response pathway triggered by sulfur limitation.

Arylsulfatases↗

PubMed1993

Protein-protein interactions in gene regulation: the cAMP-CRP complex sets the specificity of a second DNA-binding protein, the CytR repressor.

Maximal repression by the CytR protein depends on the formation of nucleoprotein complexes in which CytR interacts with DNA and with cAMP-cAMP receptor protein (CRP). Here we demonstrate that CytR regulates transcription from deoP2 promoters in which the entire CytR recognition sequence has been eliminated. Furthermore, CytR proteins deleted for the DNA-binding domain repress deoP2 in vivo and interact with deoP2 in vitro in a strictly cAMP-CRP-dependent fashion. These experiments show that the site of action of CytR can be specified by protein-protein interactions to cAMP-CRP, whereas CytR-DNA interactions may primarily serve to stabilize the nucleo-protein complex. This type of specificity mechanism may represent a general concept in the recruitment of DNA-binding proteins in combinatorial regulatory systems.

Amino Acid Sequence↗

PubMed1996

Dra-nupC-pdp operon of Bacillus subtilis: nucleotide sequence, induction by deoxyribonucleosides, and transcriptional regulation by the deoR-encoded DeoR repressor protein.

The genes encoding deoxyriboaldolase (dra), nucleoside uptake protein (nupC), and pyrimidine nucleoside sequences were determined. Sequence analysis showed that the genes were localized immediately downstream of the hut operon. Insertional gene disruption studies indicated that the three genes constitute an operon with the gene order dra-nupC-pdp. A promoter mapping immediately upstream of the dra gene was identified, and downstream of the pdp gene the nucleotide sequence indicated the existence of a factor-independent transcription terminator structure. In wild-type cells growing in succinate minimal medium, the pyrimidine nucleoside phosphorylase and deoxyriboaldolase levels were five- to eightfold higher in the presence of thymidine and fourfold higher in the presence of deoxyadenosine. By the use of lacZ fusions, the regulation was found to be at the level of transcription. The operon expression was subject to glucose repression. Upstream of the dra gene an open reading frame of 313 amino acids was identified. Inactivation of this gene led to an approximately 10-fold increase in the levels of deoxyriboaldolase and pyrimidine nucleoside phosphorylase, and no further induction was seen upon the addition of deoxyribonucleosides. The upstream gene most likely encodes the regulator for the dra-nupC-pdp operon and was designated deoR (stands for deoxyribonucleoside regulator).

Amino Acid Sequence↗

PubMed1995

Repression of protein kinase C and stimulation of cyclic AMP response elements by fumonisin, a fungal encoded toxin which is a carcinogen.

Fusarium moniliforme (FM) is a major fungal pathogen of corn and is involved with stalk rot disease. FM is widely spread throughout the world, including the United States. Most strains of FM produce several mycotoxins, the most prominent of which is called fumonisin. Recent epidemiological studies indicated that ingestion of fumonisin correlates with a higher incidence of esophageal cancer in Southern and Northern Africa and China. Furthermore, fumonisin causes a neurodegenerative disease in horses, induces hepatic cancer in rats, and induces pulmonary edema in swine. Considering that high levels of fumonisin have been detected in healthy and diseased corn grown in the United States, fumonisin may pose a health threat to humans and livestock animals. Structurally, fumonisin resembles sphingolipids which are present in the membranes of animal and plant cells. At the present time, very little is known concerning the mechanism by which fumonisin elicits its carcinogenic effect. Our studies indicate that fumonisin represses expression of protein kinase C and AP-1-dependent transcription. In contrast, fumonisin stimulated a simple promoter containing a single cyclic AMP response element. Since fumonisin did not alter protein kinase A activity, it appears that cyclic AMP response element activation was independent of protein kinase A. It is hypothesized that the ability of fumonisin to alter signal transduction pathways plays a role in carcinogenesis.

Animals↗

PubMed1975

Isolation of a catabolite repression mutant of yeast as a revertant of a strain that is maltose negative in the respiratory-deficient state.

A character originating from Saccharomyces cerevisiae 1403-7A is described which interferes with maltose growth in the respiratory-deficient state. This character is inherited in an apparently non-Mendelian way, but at present no statement can be made concerning the localization of this character on a plasmid or the involvement of multiple genes. As a revertant of this character, a flaky mutant was isolated, showing a heavy flocculation during growth on liquid medium and resistance to catabolite repression for maltase, alpha-methyl-glucosidase, invertase, and succinate dehydrogenase. In wild-type cells, repression (caused by growth on 2% glucose) and derepression (caused by growth on 2% galactose) can be correlated with a lower and a higher level of cyclic 3',5'-adenosine monophosphate (cAMP), respectively. In cells of flaky mutant, growth on these carbon sources results in the same levels of cAMP as observed for the wild type. Consequently, in this mutant derepression in the presence of 2% glucose is not reflected in a higher level of cAMP.

Cell-Free System↗