Nucleotide sequence upstream of a glucose-repressible Drosophila gene.
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Animals↗
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Influence of low oxygen concentration on derepression of nitrogenase in Klebsiella pneumoniae.
Effects of oxygen derepression of nitrogenase were studied in Klebsiella pneumoniae, using oxyleghaemoglobin to supply and monitor very low dissolved O2 concentrations in a steady-state system. Expression of the nifH gene was studied by using a nifH::lac fusion strain, which aslo carried the Nif+ plasmid pRD1 so that the production of active nitrogenase could also be monitored. When compared with anaerobic treatments, very low concentrations of dissolved O2 inhibited derepression of both nifH::lac and pRD1 nif. Fifty percent inhibition of derepression occurred at 0.1 microM-O2. The apparent Ks of the dominant terminal oxidase was 0.08 microM-O2. These results suggest that there is a close relationship between the terminal respiratory system of these bacteria and the repression of nitrogenase by O2.
Enzyme Repression↗
The inactivation of hexokinase activity does not prevent glucose repression in Candida utilis.
High hexokinase activity was not related to glucose repression in Candida utilis IGC 3092. The addition of Cibacron Blue 3G-A to growing cells in batch culture led to a permanent in vivo hexokinase inactivation, decreased growth rate and inhibited alcohol dehydrogenase. Hexokinase inactivation up to 90% did not alleviate glucose repression of alpha-glucosidase, as has been described for Saccharomyces cerevisiae and other yeasts. Moreover, when cells were physiologically derepressed by growing them in a chemostat at low glucose concentrations, the highest hexokinase activity was shown by the derepressed cells, and decreased as repression increased. Thus, in our strain of C. utilis, hexokinase activity was inversely proportional to glucose repression.
Candida↗
Regulation of invertase synthesis by glucose in Saccharomyces cerevisiae.
Saccharomyces cerevisiae growing under repressible conditions (1% of glucose or more) produces a burst of external invertase when shifted to higher temperatures. The secretion of this invertase requires protein synthesis, but was found to be independent of RNA formation. The level of mRNA accumulated and translated was inversely proportional to the glucose present in the growth medium. These results are consistent with the hypothesis that invertase is continuously synthesized both in the presence and absence of glucose, but under repressible conditions is degraded before secretion takes place.
Enzyme Repression↗
Regulation of aroL expression by TyrR protein and Trp repressor in Escherichia coli K-12.
The promoter-operator region of the aroL gene of Escherichia coli K-12 contains three TYR R boxes and one TrpR binding site. Mutational analysis showed that TYR R boxes 1 and 3 are essential for TyrR-mediated regulation of aroL expression, while a fully functional TYR R box 2 does not appear to be essential for regulation. Regulation mediated by the TrpR protein required the TYR R boxes and TrpR site to be functional and was observed in vivo only with a tyrR+ strain. Under conditions favoring the formation of TyrR hexamers, DNase I protection experiments revealed the presence of phased hypersensitive sites, indicative of DNA backbone strain. This suggests that TyrR-mediated repression involves DNA looping. Purified TrpR protein protected the putative TrpR binding site in the presence of tryptophan, and this protection was slightly enhanced in the presence of TyrR protein. This result along with the in vivo findings implies that TyrR and TrpR are able to interact in some way. Inserting 4 bp between TYR R box 1 and the TrpR binding site results in increased tyrosine repression and the abolition of the tryptophan effect. Identification of a potential integration host factor binding site and repression studies of a himA mutant support the notion that integration host factor binding normally exerts a negative effect on tyrosine-mediated repression.
Bacterial Proteins↗
Elution of exocellular enzymes from Saccharomyces fragilis and Saccharomyces cerevisiae.
Weimberg, Ralph (Northern Regional Research Laboratory, Peoria, Ill.), and William L. Orton. Elution of exocellular enzymes from Saccharomyces fragilis and Saccharomyces cerevisiae. J. Bacteriol. 91:1-13. 1966.-Invertase and acid phosphatase are repressible exocellular enzymes in Saccharomyces fragilis and S. cerevisiae. The conditions for eluting these enzymes from both organisms were compared. Either KCl or beta-mercaptoethanol eluted the enzymes from S. fragilis, and the amounts eluted varied quantitatively according to the physiological age of the organism. In addition to eluting enzymatic activity from the cells, these reagents also caused a large increase in the amount of activity that remained associated with the cells of S. fragilis. Invertase and acid phosphatase were not removed from cells of S. cerevisiae by KCl or beta-mercaptoethanol. These enzymes were separated from S. cerevisiae cells only when there was some degree of cell-wall digestion by snail gut fluid.
Acid Phosphatase↗
Transient repression of the lac operon.
Severe transient repression of constitutive or induced beta-galactosidase synthesis occurs upon the addition of glucose to cells of Escherichia coli growing on glycerol, succinic acid, or lactic acid. Only mutants particularily well adapted to growth on glucose exhibit this phenomenon when transferred to a glucose-containing medium. No change in ribonucleic acid (RNA) metabolism was observed during transient repression. We could show that transient repression is pleiotropic, affecting all products of the lac operon. It occurs in a mutant insensitive to catabolite repression. It is established much more rapidly than catabolite repression, and is elicited by glucose analogues that are phosphorylated but not further catabolized by the cell. Thus, transient repression is not a consequence of the exclusion of inducer from the cell, does not require catabolism of the added compound, and does not involve a gross change in RNA metabolism. We conclude that transient repression is distinct from catabolite repression.
Carbon Isotopes↗
Tryptophan synthetase levels in Escherichia coli, Shigella dysenteriae, and transduction hybrids.
Eisenstein, Richard B. (Western Reserve University, Cleveland, Ohio) and Charles Yanofsky. Tryptophan synthetase levels in Escherichia coli, Shigella dysenteriae, and transduction hybrids. J. Bacteriol. 83:193-204. 1962-Shigella dysenteriae and Escherichia coli, strains K-12 and B, were found to produce low levels of tryptophan synthetase, although some hybrids, formed by the introduction of the gene cluster concerned with tryptophan synthesis from S. dysenteriae into E. coli, produced high levels of this enzyme system. A revertant obtained from a tryptophan-requiring mutant also formed high levels of tryptophan synthetase. The gene or genes responsible for high enzyme production in these strains was shown to be linked to the cluster of genes concerned with tryptophan synthesis. The cause of high enzyme production was investigated. Various lines of evidence, including stimulation of growth by tryptophan precursors, sensitivity to inhibition by 5-methyltryptophan, absence of accumulation of tryptophan, and repression of enzyme formation by anthranilic acid and tryptophan, suggested that high enzyme production in the strains examined results from a partial block in the tryptophan pathway and not from resistance to repression by tryptophan. The conversion of shikimic acid-5-phosphate to anthranilic acid appears to be the partially blocked reaction in the strains studied.
Enzymes↗
Delta-Aminolevulinic acid synthase from chick embryo liver mitochondria. II. Immunochemical correlation between synthesis and activity in induction and repression.
A specific rabbit antibody was prepared against chick embryo liver mitochondrial delta-aminolevulinic acid synthase (EC 2.3.1.37) and used to quantitate the amount of enzyme present in liver mitochondria from normal and drug-treated chick embryos. When increases in enzyme activity were produced by the drugs 2-allylisopropylacetamide, or 1,4-dihydro-3,5-dicarbethoxycollidine, quantitative immunotitrations and the Laurell electroimmunoassay showed proportional increases occurred in the amount of enzyme antigen. Conversely, decreases of induced enzyme activity produced by hemin were accompanied by corresponding decreases in enzyme antigen. The relative rate of synthesis of delta-aminolevulinic acid synthase was measured by pulse-labeling of liver proteins with L-[4,5-3H]leucine. delta-Aminolevulinic acid synthase was isolated by quantitative immunoprecipitation followed by electrophoresis of the dissolved immunoprecipitate on a sodium dodecyl sulfate-polyacrylamide gel. In normal and drug-treated chick embryo liver mitochondria, enzyme activity was closely correlated with the relative rate of enzyme synthesis. When a 360-fold increase in enzyme activity was produced in vivo by a combination of 2-allylisopropylacetamide and 1,4-dihydro-3,5-dicarbethoxycollidine in 12 hours, there was a 500-fold increase in relative synthesis, such that delta-aminolevulinic acid synthase constituted over 1% of the total intracellular protein synthesis and over 3% of the total labeled protein in liver mitochondria. Hemin administered after inducing chemicals was able to completely block the induced synthesis of delta-aminolevulinc acid synthase with no significant change in general protein synthesis. Mitochondria from untreated chick embryo livers contain delta-aminolevulinic acid synthase that migrates on sodium dodecyl sulfate gels identically with the induced enzyme.
5-Aminolevulinate Synthetase↗
Two forms of RPO41-dependent RNA polymerase. Regulation of the RNA polymerase by glucose repression may control yeast mitochondrial gene expression.
We have identified two chromatographically separable forms of mitochondrial RNA polymerase from Saccharomyces cerevisiae which utilize different DNA templates. One form is only active in a nonselective assay utilizing a poly[d(A-T)] template. The other form selectively initiates from a mitochondrial promoter consensus sequence. Both enzymes can be extracted from yeast mitochondria and all components are encoded by nuclear genes. The possibility that these two activities represent core and holoenzyme forms of the multicomponent mitochondrial RNA polymerase is supported by our observation that both enzymes are absent from a strain bearing a disrupted copy of the RPO41 gene (Greenleaf, A. L., Kelly, J. L., and Lehman, I. R. (1986) Proc. Natl. Acad. Sci. U. S. A. 83, 3391-3399). The two enzyme activities are differentially regulated by carbon source; the nonselective enzyme is repressed during growth on glucose relative to the selective enzyme. The 5-fold increase in RNA polymerase activity on a nonrepressing carbon source correlates with the increased level of transcript production from mitochondrial DNA. These results suggest that the mitochondrial RNA polymerase and, in consequence, mitochondrial transcription are regulated by carbon catabolite control.
Chromatography↗
Regulation of malic enzyme gene expression by nutrients, hormones, and growth factors in fetal hepatocyte primary cultures.
The culture of fetal hepatocytes for 64 h in medium supplemented with 5 mM glucose, T3, insulin, and dexamethasone resulted in the coordinate precocious expression of malic enzyme mRNA, protein, and specific activity. T3 was the main inducer; meanwhile, insulin exerted a small synergistic effect when added with T3. Dexamethasone had a potentiation effect on the T3 response of malic enzyme mRNA expression regardless of the presence of insulin. This effect of dexamethasone on T3 response of malic enzyme mRNA expression was time (64 h) and glucose dependent. Glucagon, and to a greater degree dibutyryl-cAMP, repressed malic enzyme mRNA as well as protein expression by T3 and dexamethasone, in the absence of insulin. Glucose and other carbon sources such as lactate-pyruvate or dihydroxyacetone induced the abundance of malic enzyme mRNA in the absence of hormones. Insulin and T3 produced a high accumulation of malic enzyme mRNA in lactate-pyruvate medium, this effect being decreased by dexamethasone. EGF suppressed the induction produced by T3 and dexamethasone on malic enzyme mRNA, while the expression of beta-actin mRNA remained essentially unmodified.
Animal Nutritional Physiological Phenomena↗
An asparaginase of Aspergillus nidulans is subject to oxygen repression in addition to nitrogen metabolite repression.
Of five amidohydrolase activities subject to nitrogen metabolite repression in Aspergillus nidulans, L-asparaginase shows clearest evidence of also being subject to repression by atmospheric oxygen. Such oxygen repressibility is only evident under nitrogen metabolite derepressed conditions. Asparaginase levels are also considerably elevated by areA300, an altered function allele of the positive acting wide domain regulatory gene areA mediating nitrogen metabolite repression and are drastically reduced by loss of function mutations in areA. A. nidulans has two L-asparaginase enzymes and it has been shown by the use of appropriate mutants that these regulatory effects are exerted on the expression of that specified by the ahrA gene but probably not that specified by the apnA gene.
Aerobiosis↗
General and lysin specific control of saccharopine dehydrogenase levels in the yeast Saccharomycopsis lipolytica.
Lysine supplementation of the growth medium of a wild type strain of the yeast Saccharomycopsis lipolytica specifically results in saccharopine dehydrogenase repression. Starvation of the strain for histidine triggers a general depression of various histidine, leucine, arginine and lysine biosynthetic enzymes, including saccharopine dehydrogenase. These two types of control, specific and general, act independently on saccharopine dehydrogenase expression, since mutants which fail to respond to the specific control still are sensitive to the general one. These mutants were first selected as unable to catabolize lysine, suggesting that a link may exist between saccharopine dehydrogenase specific regulation and activity of the catabolic pathway.
Ascomycota↗
Repression by glucose of acetohydroxy acid synthetase in Escherichia coli B.
Acetolactate formation in Escherichia coli B results from the activity of a single system, acetohydroxy acid synthetase, which has a pH optimum of 8.0 and is sensitive to end-product inhibition by l-valine. Acetohydroxy acid synthetase was found to be subject to catabolite repression, and the nature and concentration of the carbon source had a greater effect on the formation of the enzyme than had the known end products (valine, isoleucine, leucine and pantothenate) of the biosynthetic pathways of which this enzyme is a member. The results suggest that acetohydroxy acid synthetase may play an amphibolic role in E. coli B.
Enzyme Repression↗
Effect of cyclopentaneglycine on metabolism in Salmonella typhimurium.
Cyclopentaneglycine (CPG) inhibited the growth of wild-type Salmonella typhimurium. The inhibition was overcome by isoleucine or any isoleucine precursor formed after threonine. CPG appeared to mimic isoleucine as a strong inhibitor of the activity of l-threonine deaminase. The analogue was a poor inhibitor of isoleucyl-transfer ribonucleic acid synthetase. CPG did not appear to be incorporated into protein nor did it replace isoleucine in repression. Cells that had recovered from growth inhibition by CPG had derepressed levels of the isoleucine-valine biosynthetic enzymes.
Amino Acids↗
Regulation of the lactose operon in vitro. II. Repression of transcription of the lactose operon.
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Coliphages↗
Culic 3', 5', -adenosine monophosphate and catabolic repression in Escherichia coli.
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Culture Media↗
The establishment of beta-galactosidase repression in the mating system of Escherichia coli K12.
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Arginine↗