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PubMed1969

Control of isoleucine, valine, and leucine biosynthesis. VI. Effect of 5',5',5'-trifluoroleucine on repression in Salmonella typhimurium.

The leucine analogue 5',5',5',-trifluoroleucine (fluoroleucine) replaced leucine for repression of the isoleucine-valine biosynthetic enzymes in Salmonella typhimurium. In contrast, the analogue had no effect on derepression of the leucine biosynthetic enzymes in leucine auxotrophs grown on limiting amounts of leucine. The effect of fluoroleucine on repression appeared to be specific for leucine since derepression of the isoleucine-valine enzymes due to an isoleucine or valine limitation was not affected by the analogue. The prevention of derepression by fluoroleucine was probably due to repression and not to the formation of false proteins, since the analogue had no effect on the derepression of a number of enzymes unrelated to the isoleucine-valine pathway. Fluoroleucine was able to attach to leucine transfer ribonucleic acid (tRNA) as evidenced by the ability of the analogue to protect about 70% of leucine tRNA from oxidation by periodate. We propose that the differential effects of fluoroleucine on repression are due to differences in the ability of the analogue to bind to the various species of leucine tRNA.

Acyltransferases↗
PubMed1990

Glucose-induced hyperaccumulation of cyclic AMP and defective glucose repression in yeast strains with reduced activity of cyclic AMP-dependent protein kinase.

Addition of glucose or related fermentable sugars to derepressed cells of the yeast Saccharomyces cerevisiae triggers a RAS-mediated cyclic AMP (cAMP) signal that induces a protein phosphorylation cascade. In yeast mutants (tpk1w1, tpk2w1, and tpk3w1) containing reduced activity of cAMP-dependent protein kinase, fermentable sugars, as opposed to nonfermentable carbon sources, induced a permanent hyperaccumulation of cAMP. This finding confirms previous conclusions that fermentable sugars are specific stimulators of cAMP synthesis in yeast cells. Despite the huge cAMP levels present in these mutants, deletion of the gene (BCY1) coding for the regulatory subunit of cAMP-dependent protein kinase severely reduced hyperaccumulation of cAMP. Glucose-induced hyperaccumulation of cAMP was also observed in exponential-phase glucose-grown cells of the tpklw1 and tpk2w1 strains but not the tpk3w1 strain even though addition of glucose to glucose-repressed wild-type cells did not induce a cAMP signal. Investigation of mitochondrial respiration by in vivo 31P nuclear magnetic resonance spectroscopy showed the tpk1w1 and tpk2w1 strains, to be defective in glucose repression. These results are consistent with the idea that the signal transmission pathway from glucose to adenyl cyclase contains a glucose-repressible protein. They also show that a certain level of cAMP-dependent protein phosphorylation is required for glucose repression. Investigation of the glucose-induced cAMP signal and glucose-induced activation of trehalase in derepressed cells of strains containing only one of the wild-type TPK genes indicates that the transient nature of the cAMP signal is due to feedback inhibition by cAMP-dependent protein kinase.

Adenosine Triphosphate↗
PubMed1998

Targeted recruitment of the Sin3-Rpd3 histone deacetylase complex generates a highly localized domain of repressed chromatin in vivo.

Eukaryotic organisms contain a multiprotein complex that includes Rpd3 histone deacetylase and the Sin3 corepressor. The Sin3-Rpd3 complex is recruited to promoters by specific DNA-binding proteins, whereupon it represses transcription. By directly analyzing the chromatin structure of a repressed promoter in yeast cells, we demonstrate that transcriptional repression is associated with localized histone deacetylation. Specifically, we observe decreased acetylation of histones H3 and H4 (preferentially lysines 5 and 12) that depends on the DNA-binding repressor (Ume6), Sin3, and Rpd3. Mapping experiments indicate that the domain of histone deacetylation is highly localized, occurring over a range of one to two nucleosomes. Taken together with previous observations, these results define a novel mechanism of transcriptional repression which involves targeted recruitment of a histone-modifying activity and localized perturbation of chromatin structure.

Chromatin↗
PubMed1982

Identification of the genetic locus for the structural gene and a new regulatory gene for the synthesis of repressible alkaline phosphatase in Saccharomyces cerevisiae.

Two lines of evidence showed that the PHO8 gene encodes the structure of repressible, nonspecific alkaline phosphatase in Saccharomyces cerevisiae: (i) the enzyme produced by a temperature-sensitive pho8 mutant at the permissive temperature (25 degrees C) was more thermolabile than that of the wild-type strain, and (ii) the PHO8 gene showed a gene dosage effect on the enzyme activity. The pho8 locus has been mapped on chromosome IV, 8 centimorgans distal to rna3. A new mutant carrying the pho9 gene was isolated which lacks repressible alkaline phosphatase, but has the normal phenotype for the synthesis of repressible acid phosphatase. The pho9 gene segregated independently of all known pho-regulatory genes and did not show the gene dosage effect on repressible alkaline phosphatase activity. The pho9/pho9 diploid hardly sporulated and showed no commitment to intragenic recombination when it was inoculated on sporulation medium. Hence the pho9 mutant has a phenotype similar to the pep4 mutant, which was isolated as a pleiotropic mutant with reduced levels of proteinases A and B and carboxypeptidase Y. An allelism test indicated that pho9 and pep4 are allelic.

Alkaline Phosphatase↗
PubMed2004

Jumonji represses atrial natriuretic factor gene expression by inhibiting transcriptional activities of cardiac transcription factors.

Mice with a homozygous knockout of the jumonji (jmj) gene showed abnormal heart development and defective regulation of cardiac-specific genes, including the atrial natriuretic factor (ANF). ANF is one of the earliest markers of cardiac differentiation and a hallmark for cardiac hypertrophy. Here, we show that JMJ represses ANF gene expression by inhibiting transcriptional activities of Nkx2.5 and GATA4. JMJ represses the Nkx2.5- or GATA4-dependent activation of the reporter genes containing the ANF promoter-enhancer or containing the Nkx2.5 or GATA4-binding consensus sequence. JMJ physically associates with Nkx2.5 and GATA4 in vitro and in vivo as determined by glutathione S-transferase pull-down and immunoprecipitation assays. Using mutational analyses, we mapped the protein-protein interaction domains in JMJ, Nkx2.5, and GATA4. We identified two DNA-binding sites of JMJ in the ANF enhancer by gel mobility shift assays. However, these JMJ-binding sites do not seem to mediate ANF repression by JMJ. Mutational analysis of JMJ indicates that the protein-protein interaction domain of JMJ mediates the repression of ANF gene expression. Therefore, JMJ may play important roles in the down-regulation of ANF gene expression and in heart development.

Amino Acid Motifs↗
PubMed1986

Effects of null mutations in the hexokinase genes of Saccharomyces cerevisiae on catabolite repression.

Saccharomyces cerevisiae has two homologous hexokinases, I and II; they are 78% identical at the amino acid level. Either enzyme allows yeast cells to ferment fructose. Mutant strains without any hexokinase can still grow on glucose by using a third enzyme, glucokinase. Hexokinase II has been implicated in the control of catabolite repression in yeasts. We constructed null mutations in both hexokinase genes, HXK1 and HXK2, and studied their effect on the fermentation of fructose and on catabolite repression of three different genes in yeasts: SUC2, CYC1, and GAL10. The results indicate that hxk1 or hxk2 single null mutants can ferment fructose but that hxk1 hxk2 double mutants cannot. The hxk2 single mutant, as well as the double mutant, failed to show catabolite repression in all three systems, while the hxk1 null mutation had little or no effect on catabolite repression.

Enzyme Repression↗
PubMed1985

Barotolerant variant of Streptococcus faecalis with reduced sensitivity to glucose catabolite repression.

Physiological characterization of the APR-11 variant of Streptococcus faecalis ATCC 9790 revealed that the variant has reduced sensitivity to glucose catabolite repression. This reduced sensitivity was indicated by the synthesis of enzymes for catabolism of lactose or arginine in cultures growing at 0.1, 40, or 70 MPa in media with levels of glucose highly repressive for the parent strain. Reduced catabolite repression appeared to be due to reduced activity of the glucose-specific, phosphotransferase system in APR-11 cells. Conversion of pyruvate to lactate or to acetate and ethanol did not appear to be altered in the variant. The APR-11 variant produced a greater final yield of biomass than the parent at all pressures tested, and its barotolerance was especially marked in media with low levels of glucose and high levels of lactose in which derepression of the lactose catabolic system was necessary for full growth. Overall, the greater barotolerance of the APR-11 strain appeared to be due to its enhanced capacity for catabolism related to its reduced sensitivity to catabolite repression by glucose.

Acetates↗
PubMed1992

Amylase cis-acting sequences mediate the alleviation of glucose repression by cAMP in Drosophila.

alpha-Amylase gene expression is highly repressed by dietary glucose in Drosophila melanogaster. This glucose effect can be alleviated by exogenous adenosine 3':5'-cyclic monophosphate (cAMP). Here, we show that the relief of glucose repression by cAMP occurs at the level of amylase mRNA abundance. Furthermore, exogenous cAMP was shown to alleviate glucose repression of the transient expression of an amylase gene construct in transformed Amynull larvae. This construct contains only 109 base pairs of the promoter region; this is the minimal length of upstream sequence which is necessary for wild-type levels of amylase gene expression. These results indicate that cis-acting promoter elements located close to the transcriptional start site of the Drosophila amylase gene mediate both glucose repression and the cAMP-derepression effects.

Animals↗
PubMed1976

Activating posthypnotic conflict: emergent uncovering psychopathology repression, and psychopathology.

An attempt was made to observe the process of repression and symptom formation. Emergent uncovering techniques were used to weaken a spontaneous repression that was produced by the posthypnotic activation of sexual impulses stemming from an implanted oedipa paramnesia. Twelve hypnotic and ten simulating subjects were used in a modified real-simulator design. Although it was not possible to 'lift' the spontaneous repression of derivatives of oedipal strivings in the course of uncovering via visual imagery, a wide variety of spontaneous symptoms were produced in the hypnotically conditioned subjects. The type of symptom was shown to be related to the degree of repression. Simulating subjects produced only a few symptoms. The manifestation of a symptom was concomitant with an increase in the GSR, but not the blatancy of drive representation. These findings were consistent with the phenomena observed using free imagery in emergent uncovering psychotherapy.

Amnesia↗
PubMed2003

Repressive coping style and positive self-presentation.

OBJECTIVE: This paper reviews 59 studies looking at cognitive, individual differences and physiological correlates of the repressive coping style, as defined by Weinberger, Schwartz, and Davidson (1979). A central aim is to evaluate the relative importance of the anxiety and social desirability components of repression. Thus, the empirical study investigates the relationships between repression and a number of relevant, but hitherto unexamined, constructs, including trait emotional intelligence (trait EI), self-estimated intelligence, functional and dysfunctional impulsivity, and stoicism. It was hypothesized that repressors would score higher than the other three groups on trait EI, self-estimated IQ and functional impulsivity, but lower on dysfunctional impulsivity. METHOD: In total, 259 (174 females) participants from three British universities completed questionnaires measuring the dependent and independent variables. Participants were divided into four groups (truly low anxious, non-defensive/high anxious, defensive/high anxious and repressors) based on their scores on anxiety and social desirability. Analyses (moderated multiple regressions and ANOVAs) were conducted both on the total sample as well as on 'extreme-scoring' individuals. RESULTS: Where there were significant differences, the hypotheses were supported, particularly with respect to trait EI, self-estimated IQ and impulsivity. Using 'extreme-scoring' groups did not effectively change the results. The regressions revealed an absence of significant interactions between anxiety and social desirability. CONCLUSION: Results are discussed in terms of the now replicated effect that repressors present a highly positive and optimistic self-image, despite cognitive and behavioural data suggesting that their coping style is psychologically unhealthy. In addition, it is argued that many findings in the repressive coping style literature can be parsimoniously explained through main effects of anxiety or social desirability alone (i.e., without invoking a construct that combines the two).

Adaptation, Psychological↗
PubMed1981

Relationship between creativity, repression, and anxiety in first graders.

The present study dealt with the extent to which creativity may be identified in 71 first graders and raised the question of whether and how creativity is related to anxiety and repression at this young age. Furthermore, correlation of 0.62 was obtained between creativity and decrease in repression. The various subtests and the four dimensions of creativity were separately analyzed in relation to anxiety and repression, and the results were discussed. No relation was found between intelligence and the dynamic variables of anxiety and repression.

Anxiety↗
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↗
PubMed1986

Identification and characterization of thiamin repressible acid phosphatase in yeast.

We have identified a genetic locus, pho4, in Schizosaccharomyces pombe which encodes a minor expressed cell surface acid phosphatase that is repressed by low concentrations (0.5 microM) of thiamin. The enzyme was purified from a strain that overproduces the enzyme. It is an Asn-linked glycoprotein. Removal of the carbohydrates by endoglycosidase H does not abolish enzymatic activity. The molecular mass of deglycosylated and unglycosylated enzyme that accumulates in membranes when cells are grown in the presence of tunicamycin is 56 kDa as determined by sodium dodecyl sulfate-gel electrophoresis. Thiamin regulation, at least in part, operates by reducing the level of pho4-mRNA. Pho4 is not genetically linked to the phosphate repressible acid phosphatase gene pho1. Phosphate and thiamin repressible acid phosphatase differ in their substrate specificity. Their protein moieties are immunologically related. Pho4 and pho1 are the only genes in S. pombe that express cell surface acid phosphatases being enzymatically active with nitrophenyl phosphate as substrate. S. pombe is not unique in having a thiamin repressible acid phosphatase. In Saccharomyces cerevisiae this enzyme is encoded by PHO3.

Acid Phosphatase↗
PubMed1996

Probes of chromatin accessibility in the Drosophila bithorax complex respond differently to Polycomb-mediated repression.

The Polycomb group (PcG) of genes are required for maintenance of the repressed state of the homeotic genes in Drosophila. There are similarities between the PcG repression and mating-type silencing in yeast or heterochromatic position effect in Drosophila, which suggest that PcG repression may involve a highly compacted chromatin structure. To test for such a structure, heterologous DNA- binding proteins were used as probes for DNA accessibility in Drosophila embryos. Binding sites for the yeast transcriptional activator GAL4 and for bacteriophage T7 RNA polymerase were inserted into the bithorax (bx) regulatory region of the endogenous Ultrabithorax (Ubx) gene, which is regulated by the PcG. Ubiquitously expressed GAL4 protein directs transcription through its binding sites only in the posterior segments where the bx region is active. The block to GAL4 activation in the more anterior segments is dependent on Polycomb (Pc) function. In contrast, T7 RNA polymerase can transcribe from its target promoter in all segments of the embryo. Thus, Pc-mediated repression blocks activated polymerase II transcription, but does not simply exclude all proteins.

Animals↗
PubMed1996

Induction and carbon catabolite repression in the biosynthesis of beta-amylase by Bacillus megaterium B6.

Biosynthesis of extracellular beta-amylase in Bacillus megaterium B6 was induced by starch, although maltodextrin was found to be the actual inducer. Amongst the carbon sources tested, glucose was found to be the most potent repressor and when added exogenously to a starch-induced culture it brought about an immediate fall in enzyme synthesis through carbon catabolite repression. The repression was not overcome after the fall of glucose concentration in the culture medium below a critical level. This "catabolite repression" exerted by glucose was partially relieved by exogenous cyclic guanosine monophosphate (CGMP) and its dibutyryl derivative. On the other hand, guanosine monophosphate (GMP) was found to restore the original extent of enzyme synthesis in glucose repressed cells.

Anti-Bacterial Agents↗
PubMed1997

Addressing the repressed needs of the Arabic client.

In comparison to families in Western society, the traditional Arabic family plays a relatively greater role in providing support for adult progeny. This serves to condition adult offspring to continue to comply with the will and values of the family. Therefore, in exchange for familial support, Arabic individuals learn to repress authentic needs and emotions, and within that process they relinquish the need for self-actualization. Arabic society discourages individualism and opposes self-actualization by means of simultaneous punishment and moralization. Thus, there is a relatively greater development of the social value system (or superego) and comparatively less development of the self (or ego). In comparison to Western society, Arabic individuals continue to experience greater oppression during adulthood. Given these cultural differences, the processes of reliving and activating repressed needs and emotions, which ultimately serves to promote self-actualization, will transform intrapsychic conflicts into interpersonal and social ones. Thus, personal actions typically encouraged during Western psychotherapy are likely to produce significant social oppression. Indeed, promoting awareness of repressed needs and emotions often leads the Arabic client to become more helpless, because such wishes will rarely be socially sanctioned or satisfactorily fulfilled. Therefore, when addressing repressed needs and emotions in psychotherapy, ego strength, cultural identity, and degree of strictness of the client's family of origin must be considered.

Adolescent↗
PubMed1997

Impact of expert testimony on the believability of repressed memories.

Research suggests that people question the believability of trial testimony based on an alleged victim's previously repressed memories. Participants read one of six scenarios depicting the trial of a man accused of sexually assaulting a young girl. The alleged victim either reported the assault immediately (child witness) or waited 20 years to report it (adult witness). In the adult witness condition, the woman's memory for the event had either been repressed until recently or had always been available, and expert testimony was offered on behalf of the defense, the prosecution, both, or neither. Regression analyses revealed that women perceived the accuser's testimony as more believable and the defendant's testimony as less believable than men did. Similarly, the belief in the accuser's testimony decreased and the belief in the defendant's testimony increased when the accuser was an adult in contrast to a child, and when the defense offered expert testimony in contrast to its absence. In addition, guilty verdicts were associated with higher levels of accuser believability, lower levels of defendant believability and testimony based on repressed memories in contrast to testimony based on memories that were never repressed.

Adolescent↗
PubMed1998

Multiple regulatory proteins mediate repression and activation by interaction with the yeast Mig1 binding site.

A major mediator of glucose repression in yeast is Mig1, a zinc finger protein that binds to a GC-rich recognition sequence found upstream of many glucose-repressible genes. Because these Mig1 sites are found upstream of genes under different modes of regulation, we studied regulation of transcription mediated by an isolated Mig1 site placed upstream of a reporter gene under control of UAS(CYC1). The Mig1 site responded appropriately to glucose control and regulatory mutations, including snf1, reg1, cyc8, and tup1, mimicking the behavior of the SUC2 gene. Deletion of the MIG1-coding gene reduced but did not eliminate glucose repression mediated by the Mig1 site. Complete loss of repression was seen in a mig1 mig2 double mutant. When the UAS(CYC1) was replaced by UAS(ADH1) in the reporter plasmid, the Mig1 site activated transcription under most conditions. Mutations of the two Mig1 binding sites in the SUC2 promoter resulted in loss of activation of SUC2 expression. These results suggest the presence of an unknown activator or activators that binds to the Mig1 site. The activator is not any of the proteins previously proposed to bind to this site, including Mig1, Mig2, Msn2, or Msn4. Band shift assays showed that Mig1 is the major protein in yeast cell extracts that binds to the Mig1 site in vitro. This binding is not regulated by glucose or mutations in CYC8 or TUP1.

Binding Sites↗