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Sample records for derivative pentamidine represses

  1. Effects of pentamidine isethionate on Saccharomyces cerevisiae.

    PubMed

    Ludewig, G; Williams, J M; Li, Y; Staben, C

    1994-05-01

    We used Saccharomyces cerevisiae as a model system in which to examine the mechanism of action of the anti-Pneumocystis drug pentamidine. Pentamidine at low concentrations inhibited S. cerevisiae growth on nonfermentable carbon sources (50% inhibitory concentration [IC50] of 1.25 micrograms/ml in glycerol). Pentamidine inhibited growth on fermentable energy sources only at much higher concentrations (IC50 of 250 micrograms/ml in glucose). Inhibition at low pentamidine concentrations in glycerol was due to cytostatic activity rather than cytotoxic or mutagenic activity. Pentamidine also rapidly inhibited respiration by intact yeast cells, although inhibitory concentrations were much higher than those inhibitory to growth (IC50 of 100 micrograms/ml for respiration). Pentamidine also induced petite mutations, although only at concentrations much higher than those required for growth inhibition. These results suggest that a function essential for respiratory growth is inhibited by pentamidine and that pentamidine affects mitochondrial processes. We propose the hypothesis that the primary cellular target of pentamidine in S. cerevisiae is the mitochondrion.

  2. Pentamidine Is Not a Permeant but a Nanomolar Inhibitor of the Trypanosoma brucei Aquaglyceroporin-2.

    PubMed

    Song, Jie; Baker, Nicola; Rothert, Monja; Henke, Björn; Jeacock, Laura; Horn, David; Beitz, Eric

    2016-02-01

    The chemotherapeutic arsenal against human African trypanosomiasis, sleeping sickness, is limited and can cause severe, often fatal, side effects. One of the classic and most widely used drugs is pentamidine, an aromatic diamidine compound introduced in the 1940s. Recently, a genome-wide loss-of-function screen and a subsequently generated trypanosome knockout strain revealed a specific aquaglyceroporin, TbAQP2, to be required for high-affinity uptake of pentamidine. Yet, the underlying mechanism remained unclear. Here, we show that TbAQP2 is not a direct transporter for the di-basic, positively charged pentamidine. Even though one of the two common cation filters of aquaglyceroporins, i.e. the aromatic/arginine selectivity filter, is unconventional in TbAQP2, positively charged compounds are still excluded from passing the channel. We found, instead, that the unique selectivity filter layout renders pentamidine a nanomolar inhibitor of TbAQP2 glycerol permeability. Full, non-covalent inhibition of an aqua(glycero)porin in the nanomolar range has not been achieved before. The remarkable affinity derives from an electrostatic interaction with Asp265 and shielding from water as shown by structure-function evaluation and point mutation of Asp265. Exchange of the preceding Leu264 to arginine abolished pentamidine-binding and parasites expressing this mutant were pentamidine-resistant. Our results indicate that TbAQP2 is a high-affinity receptor for pentamidine. Taken together with localization of TbAQP2 in the flagellar pocket of bloodstream trypanosomes, we propose that pentamidine uptake is by endocytosis. PMID:26828608

  3. Pentamidine Is Not a Permeant but a Nanomolar Inhibitor of the Trypanosoma brucei Aquaglyceroporin-2

    PubMed Central

    Baker, Nicola; Henke, Björn; Jeacock, Laura; Horn, David; Beitz, Eric

    2016-01-01

    The chemotherapeutic arsenal against human African trypanosomiasis, sleeping sickness, is limited and can cause severe, often fatal, side effects. One of the classic and most widely used drugs is pentamidine, an aromatic diamidine compound introduced in the 1940s. Recently, a genome-wide loss-of-function screen and a subsequently generated trypanosome knockout strain revealed a specific aquaglyceroporin, TbAQP2, to be required for high-affinity uptake of pentamidine. Yet, the underlying mechanism remained unclear. Here, we show that TbAQP2 is not a direct transporter for the di-basic, positively charged pentamidine. Even though one of the two common cation filters of aquaglyceroporins, i.e. the aromatic/arginine selectivity filter, is unconventional in TbAQP2, positively charged compounds are still excluded from passing the channel. We found, instead, that the unique selectivity filter layout renders pentamidine a nanomolar inhibitor of TbAQP2 glycerol permeability. Full, non-covalent inhibition of an aqua(glycero)porin in the nanomolar range has not been achieved before. The remarkable affinity derives from an electrostatic interaction with Asp265 and shielding from water as shown by structure-function evaluation and point mutation of Asp265. Exchange of the preceding Leu264 to arginine abolished pentamidine-binding and parasites expressing this mutant were pentamidine-resistant. Our results indicate that TbAQP2 is a high-affinity receptor for pentamidine. Taken together with localization of TbAQP2 in the flagellar pocket of bloodstream trypanosomes, we propose that pentamidine uptake is by endocytosis. PMID:26828608

  4. Structure-Based Discovery of a Novel Pentamidine-Related Inhibitor of the Calcium-Binding Protein S100B.

    PubMed

    McKnight, Laura E; Raman, E Prabhu; Bezawada, Padmavani; Kudrimoti, Sucheta; Wilder, Paul T; Hartman, Kira G; Godoy-Ruiz, Raquel; Toth, Eric A; Coop, Andrew; Mackerell, Alexander D; Weber, David J

    2012-12-13

    Molecular Dynamics simulations of the pentamidine-S100B complex, where two molecules of pentamidine bind per monomer of S100B, were performed in an effort to determine what properties would be desirable in a pentamidine-derived compound as an inhibitor for S100B. These simulations predicted that increasing the linker length of the compound would allow a single molecule to span both pentamidine binding sites on the protein. The resulting compound, SBi4211 (also known as heptamidine), was synthesized and experiments to study its inhibition of S100B were performed. The 1.65 Å X-ray crystal structure was determined for Ca(2+)-S100B-heptamdine and gives high-resolution information about key contacts that facilitate the interaction between heptamidine and S100B. Additionally, NMR HSQC experiments with both compounds show that heptamidine interacts with the same region of S100B as pentamidine. Heptamidine is able to selectively kill melanoma cells with S100B over those without S100B, indicating that its binding to S100B has an inhibitory effect and that this compound may be useful in designing higher-affinity S100B inhibitors as a treatment for melanoma and other S100B-related cancers. PMID:23264854

  5. Pentamidine is a specific, non-peptide, GPIIb/IIIa antagonist.

    PubMed

    Cox, D; Aoki, T; Seki, J; Motoyama, Y; Yoshida, K

    1996-03-01

    Pentamidine was previously shown to act on glycoprotein (GP) IIb/IIIa (Cox et al., Thromb Haemost 1992; 68: 731). In this paper we study the effect of pentamidine on other RGD-dependent receptors. In a cell adhesion assay, pentamidine was 500 times more potent than RGDS at inhibiting platelet adhesion to fibrinogen. While RGDS inhibited platelet adhesion to fibronectin, endothelial cell adhesion to vitronectin or fibronectin, 293 cell adhesion to vitronectin, IMR 32 cell adhesion to fibronectin and C32 cell adhesion to vitronectin; pentamidine failed to inhibit these interactions at doses as high as 1 mM. Resting platelets fixed in the presence of 1 mM RGDS had increased binding of fibrinogen, i.e., RGDS activated GPIIb/IIIa, while pentamidine at 100 microM had no effect. Similarly, RGDS induced the binding of an anti-LIBS monoclonal antibody, while pentamidine had no effect. Pentamidine partially, but significantly, inhibited lysosome and alpha-granule release induced by the thrombin agonist peptide, while RGDS had no effect. Neither pentamidine nor RGDS affected ADP-induced Ca2+ influx. Pentamidine had no effect on ADP-induced intracellular pH changes while RGDS prevented the pH from returning to normal. Thus, pentamidine is a non-peptide GPIIb/IIIa antagonist that is non-activating and is specific for GPIIb/IIIa.

  6. The inhibition of monoamine oxidase by phenformin and pentamidine.

    PubMed

    Barkhuizen, M; Petzer, A; Petzer, J P

    2014-09-01

    A computational study has suggested that phenformin, an oral hypoglycaemic drug, may bind to the active sites of the monoamine oxidase (MAO) A and B enzymes. The present study therefore investigates the MAO inhibitory properties of phenformin. Pentamidine, a structurally related diamidine compound, has previously been reported to be a MAO inhibitor and was included in this study as a reference compound. Using recombinant human MAO-A and MAO-B, this study finds that phenformin acts as a moderately potent MAO-A selective inhibitor with an IC50 value of 41 µM. Pentamidine, on the other hand, potently inhibits both MAO-A and MAO-B with IC50 values of 0.61 μM and 0.22 μM, respectively. An examination of the recoveries of the enzymatic activities after dilution and dialysis of the enzyme-inhibitor complexes shows that both compounds interact reversibly with the MAO enzymes. A kinetic analysis suggests that pentamidine acts as a competitive inhibitor with estimated Ki values of 0.41 μM and 0.22 μM for the inhibition of MAO-A and MAO-B, respectively. Phenformin also exhibited a competitive mode of MAO-A inhibition with an estimated Ki value of 65 µM. This study concludes that biguanide and amidine functional groups are most likely important structural features for the inhibition of the MAOs by phenformin and pentamidine, and compounds containing these and closely related functional groups should be considered as potential MAO inhibitors. Furthermore, the biguanide and amidine functional groups may act as useful moieties in the future design of MAO inhibitors.

  7. Alveolar targeting of aerosol pentamidine. Toward a rational delivery system

    SciTech Connect

    Simonds, A.K.; Newman, S.P.; Johnson, M.A.; Talaee, N.; Lee, C.A.; Clarke, S.W. )

    1990-04-01

    Nebulizer systems that deposit a high proportion of aerosolized pentamidine on large airways are likely to be associated with marked adverse side effects, which may lead to premature cessation of treatment. We have measured alveolar deposition and large airway-related side effects (e.g., cough, breathlessness, and effect on pulmonary function) after aerosolization of 150 mg pentamidine isethionate labeled with {sup 99m}Tc-Sn-colloid. Nine patients with AIDS were studied using three nebulizer systems producing different droplet size profiles: the Acorn System 22, Respirgard II, and Respirgard II with the inspiratory baffle removed. Alveolar deposition was greatest and side effects least with the nebulizer producing the smallest droplet size profile (Respirgard II), whereas large airway-related side effects were prominent and alveolar deposition lowest with the nebulizer producing the largest droplet size (Acorn System 22). Values for alveolar deposition and adverse airway effects were intermediate using the Respirgard with inspiratory baffle removed, thus indicating the importance of the baffle valve in determining droplet size. Addition of a similar baffle valve to the Acorn System 22 produced a marked improvement in droplet size profile. Selection of a nebulizer that produces an optimal droplet size range offers the advantage of enhancing alveolar targeting of aerosolized pentamidine while reducing large airway-related side effects.

  8. Mutation of the mitochondrial large ribosomal RNA can provide pentamidine resistance to Saccharomyces cerevisiae.

    PubMed

    Örs, Ş Tomris; Akdoğan, Emel; Dunn, Cory D

    2014-09-01

    Pentamidine is used to treat several trypanosomal diseases, as well as opportunistic infection by pathogenic fungi. However, the relevant targets of this drug are unknown. We isolated dominant mutations providing pentamidine resistance to Saccharomyces cerevisiae, one of which was localized to mitochondrial DNA. Next-generation sequencing revealed alteration of a widely conserved base at the peptidyl transferase center of the mitochondrial 21S ribosomal RNA. Our results provide a potential rationale for the toxicity of this drug to patients, and we discuss whether blockade of mitochondrial translation is the mechanism by which pathogenic fungi or protists are killed by pentamidine.

  9. Molecular determinants of pentamidine-induced hERG trafficking inhibition.

    PubMed

    Dennis, Adrienne T; Wang, Lu; Wan, Hanlin; Nassal, Drew; Deschenes, Isabelle; Ficker, Eckhard

    2012-02-01

    Pentamidine is an antiprotozoal compound that clinically causes acquired long QT syndrome (acLQTS), which is associated with prolonged QT intervals, tachycardias, and sudden cardiac arrest. Pentamidine delays terminal repolarization in human heart by acutely blocking cardiac inward rectifier currents. At the same time, pentamidine reduces surface expression of the cardiac potassium channel I(Kr)/human ether à-go-go-related gene (hERG). This is unusual in that acLQTS is caused most often by direct block of the cardiac potassium current I(Kr)/hERG. The present study was designed to provide a more complete picture of how hERG surface expression is disrupted by pentamidine at the cellular and molecular levels. Using biochemical and electrophysiological methods, we found that pentamidine exclusively inhibits hERG export from the endoplasmic reticulum to the cell surface in a heterologous expression system as well as in cardiomyocytes. hERG trafficking inhibition could be rescued in the presence of the pharmacological chaperone astemizole. We used rescue experiments in combination with an extensive mutational analysis to locate an interaction site for pentamidine at phenylalanine 656, a crucial residue in the canonical drug binding site of terminally folded hERG. Our data suggest that pentamidine binding to a folding intermediate of hERG arrests channel maturation in a conformational state that cannot be exported from the endoplasmic reticulum. We propose that pentamidine is the founding member of a novel pharmacological entity whose members act as small molecule antichaperones. PMID:22046004

  10. Osteoblast-derived WNT16 represses osteoclastogenesis and prevents cortical bone fragility fractures

    PubMed Central

    Movérare-Skrtic, Sofia; Henning, Petra; Liu, Xianwen; Nagano, Kenichi; Saito, Hiroaki; Börjesson, Anna E; Sjögren, Klara; Windahl, Sara H; Farman, Helen; Kindlund, Bert; Engdahl, Cecilia; Koskela, Antti; Zhang, Fu-Ping; Eriksson, Emma E; Zaman, Farasat; Hammarstedt, Ann; Isaksson, Hanna; Bally, Marta; Kassem, Ali; Lindholm, Catharina; Sandberg, Olof; Aspenberg, Per; Sävendahl, Lars; Feng, Jian Q; Tuckermann, Jan; Tuukkanen, Juha; Poutanen, Matti; Baron, Roland; Lerner, Ulf H; Gori, Francesca; Ohlsson, Claes

    2015-01-01

    The WNT16 locus is a major determinant of cortical bone thickness and nonvertebral fracture risk in humans. The disability, mortality and costs caused by osteoporosis-induced nonvertebral fractures are enormous. We demonstrate here that Wnt16-deficient mice develop spontaneous fractures as a result of low cortical thickness and high cortical porosity. In contrast, trabecular bone volume is not altered in these mice. Mechanistic studies revealed that WNT16 is osteoblast derived and inhibits human and mouse osteoclastogenesis both directly by acting on osteoclast progenitors and indirectly by increasing expression of osteoprotegerin (Opg) in osteoblasts. The signaling pathway activated by WNT16 in osteoclast progenitors is noncanonical, whereas the pathway activated in osteoblasts is both canonical and noncanonical. Conditional Wnt16 inactivation revealed that osteoblast-lineage cells are the principal source of WNT16, and its targeted deletion in osteoblasts increases fracture susceptibility. Thus, osteoblast-derived WNT16 is a previously unreported key regulator of osteoclastogenesis and fracture susceptibility. These findings open new avenues for the specific prevention or treatment of nonvertebral fractures, a substantial unmet medical need. PMID:25306233

  11. Pentamidine binds to tRNA through non-specific hydrophobic interactions and inhibits aminoacylation and translation.

    PubMed

    Sun, Tao; Zhang, Yi

    2008-03-01

    The selective and potent inhibition of mitochondrial translation in Saccharomyces cerevisiae by pentamidine suggests a novel antimicrobial action for this drug. Electrophoresis mobility shift assay, T1 ribonuclease footprinting, hydroxyl radical footprinting and isothermal titration calorimetry collectively demonstrated that pentamidine non-specifically binds to two distinct classes of sites on tRNA. The binding was driven by favorable entropy changes indicative of a large hydrophobic interaction, suggesting that the aromatic rings of pentamidine are inserted into the stacked base pairs of tRNA helices. Pentamidine binding disrupts the tRNA secondary structure and masks the anticodon loop in the tertiary structure. Consistently, we showed that pentamidine specifically inhibits tRNA aminoacylation but not the cognate amino acid adenylation. Pentamidine inhibited protein translation in vitro with an EC(50) equivalent to that binds to tRNA and inhibits tRNA aminoacylation in vitro, but drastically higher than that inhibits translation in vivo, supporting the established notion that the antimicrobial activity of pentamidine is largely due to its selective accumulation by the pathogen rather than by the host cell. Therefore, interrupting tRNA aminoacylation by the entropy-driven non-specific binding is an important mechanism of pentamidine in inhibiting protein translation, providing new insights into the development of antimicrobial drugs.

  12. Pentamidine exerts in vitro and in vivo anti Trypanosoma cruzi activity and inhibits the polyamine transport in Trypanosoma cruzi.

    PubMed

    Díaz, María V; Miranda, Mariana R; Campos-Estrada, Carolina; Reigada, Chantal; Maya, Juan D; Pereira, Claudio A; López-Muñoz, Rodrigo

    2014-06-01

    Pentamidine is an antiprotozoal and fungicide drug used in the treatment of leishmaniasis and African trypanosomiasis. Despite its extensive use as antiparasitic drug, little evidence exists about the effect of pentamidine in Trypanosoma cruzi, the etiological agent of Chagas' disease. Recent studies have shown that pentamidine blocks a polyamine transporter present in Leishmania major; consequently, its might also block these transporters in T. cruzi. Considering that T. cruzi lacks the ability to synthesize putrescine de novo, the inhibition of polyamine transport can bring a new therapeutic target against the parasite. In this work, we show that pentamidine decreases, not only the viability of T. cruzi trypomastigotes, but also the parasite burden of infected cells. In T. cruzi-infected mice pentamidine decreases the inflammation and parasite burden in hearts from infected mice. The treatment also decreases parasitemia, resulting in an increased survival rate. In addition, pentamidine strongly inhibits the putrescine and spermidine transport in T. cruzi epimastigotes and amastigotes. Thus, this study points to reevaluate the utility of pentamidine and introduce evidence of a potential new action mechanism. In the quest of new therapeutic strategies against Chagas disease, the extensive use of pentamidine in human has led to a well-known clinical profile, which could be an advantage over newly synthesized molecules that require more comprehensive trials prior to their clinical use.

  13. Pentamidine blocks the interaction between mutant S100A5 and RAGE V domain and inhibits the RAGE signaling pathway.

    PubMed

    Cho, Ching Chang; Chou, Ruey Hwang; Yu, Chin

    2016-08-19

    The human S100 protein family contains small, dimeric and acidic proteins that contain two EF-hand motifs and bind calcium. When S100A5 binds calcium, its conformation changes and promotes interaction with the target protein. The extracellular domain of RAGE (Receptor of Advanced Glycation End products) contain three domains: C1, C2 and V. The RAGE V domain is the target protein of S100A5 that promotes cell survival, growth and differentiation by activating several signaling pathways. Pentamidine is an apoptotic and antiparasitic drug that is used to treat or prevent pneumonia. Here, we found that pentamidine interacts with S100A5 using HSQC titration. We elucidated the interactions of S100A5 with RAGE V domain and pentamidine using fluorescence and NMR spectroscopy. We generated two binary models-the S100A5-RAGE V domain and S100A5-Pentamidine complex-and then observed that the pentamidine and RAGE V domain share a similar binding region in mS100A5. We also used the WST-1 assay to investigate the bioactivity of S100A5, RAGE V domain and pentamidine. These results indicated that pentamidine blocks the binding between S100A5 and RAGE V domain. This finding is useful for the development of new anti-proliferation drugs.

  14. Pentamidine blocks the interaction between mutant S100A5 and RAGE V domain and inhibits the RAGE signaling pathway.

    PubMed

    Cho, Ching Chang; Chou, Ruey Hwang; Yu, Chin

    2016-08-19

    The human S100 protein family contains small, dimeric and acidic proteins that contain two EF-hand motifs and bind calcium. When S100A5 binds calcium, its conformation changes and promotes interaction with the target protein. The extracellular domain of RAGE (Receptor of Advanced Glycation End products) contain three domains: C1, C2 and V. The RAGE V domain is the target protein of S100A5 that promotes cell survival, growth and differentiation by activating several signaling pathways. Pentamidine is an apoptotic and antiparasitic drug that is used to treat or prevent pneumonia. Here, we found that pentamidine interacts with S100A5 using HSQC titration. We elucidated the interactions of S100A5 with RAGE V domain and pentamidine using fluorescence and NMR spectroscopy. We generated two binary models-the S100A5-RAGE V domain and S100A5-Pentamidine complex-and then observed that the pentamidine and RAGE V domain share a similar binding region in mS100A5. We also used the WST-1 assay to investigate the bioactivity of S100A5, RAGE V domain and pentamidine. These results indicated that pentamidine blocks the binding between S100A5 and RAGE V domain. This finding is useful for the development of new anti-proliferation drugs. PMID:27297108

  15. Nebulised pentamidine as treatment for Pneumocystis carinii pneumonia in the acquired immunodeficiency syndrome.

    PubMed Central

    Miller, R F; Godfrey-Faussett, P; Semple, S J

    1989-01-01

    Nebulised pentamidine was used to treat 30 patients with Pneumocystis carinii pneumonia. Fourteen patients (group 1) received pentamidine isethionate 4 mg/kg (six patients) or 8 mg/kg (eight patients) via a standard jet nebuliser (Acorn, system 22) with a flow rate of 8 l/min. The aerosol droplets had a mass median aerodynamic diameter of 2.6 microns (geometric standard deviation (GSD) 2.9) and 46% of droplets were less than 3.9 microns. A further 16 patients (group 2) received 8 mg/kg pentamidine via a jet nebuliser with baffles to limit droplet size to below 4 microns (Respirgard II). This generated aerosol droplets with a mass median aerodynamic diameter of 0.8 micron (GSD 1.5) and 98% were less than 3.9 microns. Only three of the 14 patients in group 1 responded clinically to treatment, one after the lower dose of pentamidine. Treatment was discontinued in 10 patients and one patient died at bronchoscopy from haemorrhage. Thirteen of the 16 patients in group 2 responded. Side effects occurred infrequently; two patients from group 1 had a cough, six patients (four from group 2) had contact bleeding at bronchoscopy, and two further patients had haemoptysis. The differing response rate may be due to differences in the mean droplet size of the aerosols produced by the nebulisers. Nebulised pentamidine (8 mg/kg) when delivered by Respirgard II nebuliser appears to be as effective as conventional treatment for Pneumocystis carinii pneumonia of mild to moderate severity. PMID:2788936

  16. Synthesis of oxadiazole-morpholine derivatives and manifestation of the repressed CD31 Microvessel Density (MVD) as tumoral angiogenic parameters in Dalton's Lymphoma.

    PubMed

    Al-Ghorbani, Mohammed; Vigneshwaran, V; Ranganatha, V Lakshmi; Prabhakar, B T; Khanum, Shaukath Ara

    2015-06-01

    A series of oxadiazole derivatives possessing morpholine 6a-l were synthesized by nucleophilic substitution reaction of key intermediates [1,3,4]-oxadiazole-2-thiol derivatives 5a-l with 4-(2-chloroethyl) morpholine. Compounds 6a-l were evaluated for their in vitro and in vivo antitumor potential in Dalton's Lymphoma Ascites (DLA) tumor cells. Among 6a-l series, compound 6a with concentration ∼8.5μM have shown extensive cytotoxicity in vitro and 85% reduction in tumor volume in vivo, attributing an excellent anti-proliferative capability towards the cancer cells. Compound 6a has extensively inhibited the Microvessel Density (MVD) or tumoral neovasculature which was evident from the CD31 immuno staining and peritoneal H&E staining. The major reason for the antiproliferative activity of compound 6a was due to the repression of tumor vasculature. PMID:26005956

  17. Upregulation of miR-22 Promotes Osteogenic Differentiation and Inhibits Adipogenic Differentiation of Human Adipose Tissue-Derived Mesenchymal Stem Cells by Repressing HDAC6 Protein Expression

    PubMed Central

    Huang, Shan; Wang, Shihua; Bian, Chunjing; Yang, Zhuo; Zhou, Hong; Zeng, Yang; Li, Hongling; Han, Qin

    2012-01-01

    Mesenchmal stem cells (MSCs) can be differentiated into either adipocytes or osteoblasts, and a reciprocal relationship exists between adipogenesis and osteogenesis. Multiple transcription factors and signaling pathways have been reported to regulate adipogenic or osteogenic differentiation, respectively, yet the molecular mechanism underlying the cell fate alteration between adipogenesis and osteogenesis still remains to be illustrated. MicroRNAs are important regulators in diverse biological processes by repressing protein expression of their targets. Here, miR-22 was found to regulate adipogenic and osteogenic differentiation of human adipose tissue-derived mesenchymal stem cells (hADMSCs) in opposite directions. Our data showed that miR-22 decreased during the process of adipogenic differentiation but increased during osteogenic differentiation. On one hand, overexpression of miR-22 in hADMSCs could inhibit lipid droplets accumulation and repress the expression of adipogenic transcription factors and adipogenic-specific genes. On the other hand, enhanced alkaline phosphatase activity and matrix mineralization, as well as increased expression of osteo-specific genes, indicated a positive role of miR-22 in regulating osteogenic differentiation. Target databases prediction and validation by Dual Luciferase Reporter Assay, western blot, and real-time polymerase chain reaction identified histone deacetylase 6 (HDAC6) as a direct downstream target of miR-22 in hADMSCs. Inhibition of endogenous HDAC6 by small-interfering RNAs suppressed adipogenesis and stimulated osteogenesis, consistent with the effect of miR-22 overexpression in hADMSCs. Together, our results suggested that miR-22 acted as a critical regulator of balance between adipogenic and osteogenic differentiation of hADMSCs by repressing its target HDAC6. PMID:22375943

  18. Aerosolized pentamidine: Effect on diagnosis and presentation of Pneumocystis carinii pneumonia

    SciTech Connect

    Jules-Elysee, K.M.; Stover, D.E.; Zaman, M.B.; Bernard, E.M.; White, D.A. )

    1990-05-15

    The objective of this study was to determine the effect of previous aerosolized pentamidine therapy on diagnosis and presentation of Pneumocystis carinii pneumonia. This was a retrospective study of fifty-two consecutive patients with P. carinii pneumonia and underlying infection with the human immunodeficiency virus (HIV) who had bronchoscopy. Twenty-one patients who were on aerosolized pentamidine therapy served as the study group. Thirty-one patients who had not received the drug served as the control group. The yield of bronchoalveolar lavage for P. carinii pneumonia was 62% for the study group and 100% for the control group (P less than 0.05). This lower yield was significant for the subset of patients having their first episode of P. carinii pneumonia. The yield of transbronchial biopsy was similar for both groups of patients (81% compared with 84%). The yield of bronchoscopy was not influenced by use of zidovudine. Review of lavage specimen slides suggested that there may be fewer organisms present in patients receiving aerosolized pentamidine. An atypical roentgenographic presentation of upper lobe predominant infiltrates was seen in 38% of the study patients and 7% of the control patients. In addition, pneumothoraces and cystic changes were also frequently seen in the study patients. Gallium scans, when done, were also atypical in the study group. Markers of the severity of disease, however, were similar in both groups. The yield of bronchoalveolar lavage for P. carinii pneumonia in HIV-infected patients is lower in patients receiving aerosolized pentamidine. Unusual roentgenographic presentations and atypical gallium scans are also found in this setting.

  19. Prostate-derived ets factor represses tumorigenesis and modulates epithelial-to-mesenchymal transition in bladder carcinoma cells.

    PubMed

    Tsui, Ke-Hung; Lin, Yu-Hsiang; Chung, Li-Chuan; Chuang, Sung-Ting; Feng, Tsui-Hsia; Chiang, Kun-Chun; Chang, Phei-Lang; Yeh, Chi-Ju; Juang, Horng-Heng

    2016-05-28

    Prostate-derived Ets (E-twenty six) factor (PDEF), an epithelium-specific member of the Ets family of transcription factors, has been shown to play a role in suppressing the development of many epithelium-derived cancers such as prostate and breast cancer. It is not clear, however, whether PDEF is involved in the development or progression of bladder cancer. In a comparison between normal urothelium and bladder tumor tissue, we identified significant decreases of PDEF in the tumor tissue. Further, the immunohistochemistry assays indicated a significantly higher immunostaining of PDEF in low-grade bladder tumors. Additionally, the highly differentiated transitional-cell bladder carcinoma RT-4 cells expressed significantly more PDEF levels than the bladder carcinoma HT1376 and the T24 cells. Ectopic overexpression of PDEF attenuated proliferation, invasion, and tumorigenesis of bladder carcinoma cells in vitro and in vivo. PDEF enhanced the expression levels of mammary serine protease inhibitor (MASPIN), N-myc downstream regulated gene 1 (NDRG1), KAI1, and B-cell translocation gene 2 (BTG2). PDEF modulated epithelial-mesenchymal-transition (EMT) by upregulating E-cadherin expression and downregulating the expression of N-cadherin, SNAIL, SLUG, and vimentin, leading to lower migration and invasion abilities of bladder carcinoma cells. Filamentous actin (F-actin) polarization and remodeling were observed in PDEF-knockdown RT-4 cells. Our results suggest that PDEF gene expression is associated with the extent of bladder neoplasia and PDEF modulated the expressions of EMT-related genes. The induction of BTG2, NDRG1, MASPIN, and KAI1 gene expressions by PDEF may explain the inhibitory functions of PDEF on the proliferation, invasion, and tumorigenesis in bladder carcinoma cells.

  20. Glycosaminoglycans are potential pharmacological targets for classic DNA minor groove binder drugs berenil and pentamidine.

    PubMed

    Zsila, Ferenc

    2015-10-14

    It is shown that the antiprotozoal drugs berenil and pentamidine, conventional minor groove binders of DNA, form non-covalent complexes with polyanionic glycosaminoglycans. Induced circular dichroism (CD) spectra as well as UV hypochromism confirmed drug binding to the asymmetric template of heparin and chondroitin 6-sulfate. The biphasic nature of the CD signals refers to intermolecular chiral exciton coupling between the dicationic guest molecules forming a right- or a left-handed helical array along the GAG chains. Quantitative evaluation of the spectroscopic data measured in pH 7.0 buffer solution (80 mM NaCl) indicated a higher (Ka ∼ 10(6) M(-1) for berenil) and a lower (Ka ∼ 10(5) M(-1) for pentamidine) affinity heparin binding of these agents, similar to that reported for DNA. Drug-chondroitin sulfate complexes (Ka ∼ 10(4)-10(5) M(-1)) could be detected only at low ionic strength. These results imply that besides nucleic acids, GAGs may be another pharmacological targets for diarylamidine drugs.

  1. Trypanosoma brucei aquaglyceroporin 2 is a high-affinity transporter for pentamidine and melaminophenyl arsenic drugs and the main genetic determinant of resistance to these drugs

    PubMed Central

    Munday, Jane C.; Eze, Anthonius A.; Baker, Nicola; Glover, Lucy; Clucas, Caroline; Aguinaga Andrés, David; Natto, Manal J.; Teka, Ibrahim A.; McDonald, Jennifer; Lee, Rebecca S.; Graf, Fabrice E.; Ludin, Philipp; Burchmore, Richard J. S.; Turner, C. Michael R.; Tait, Andy; MacLeod, Annette; Mäser, Pascal; Barrett, Michael P.; Horn, David; De Koning, Harry P.

    2014-01-01

    Objectives Trypanosoma brucei drug transporters include the TbAT1/P2 aminopurine transporter and the high-affinity pentamidine transporter (HAPT1), but the genetic identity of HAPT1 is unknown. We recently reported that loss of T. brucei aquaglyceroporin 2 (TbAQP2) caused melarsoprol/pentamidine cross-resistance (MPXR) in these parasites and the current study aims to delineate the mechanism by which this occurs. Methods The TbAQP2 loci of isogenic pairs of drug-susceptible and MPXR strains of T. brucei subspecies were sequenced. Drug susceptibility profiles of trypanosome strains were correlated with expression of mutated TbAQP2 alleles. Pentamidine transport was studied in T. brucei subspecies expressing TbAQP2 variants. Results All MPXR strains examined contained TbAQP2 deletions or rearrangements, regardless of whether the strains were originally adapted in vitro or in vivo to arsenicals or to pentamidine. The MPXR strains and AQP2 knockout strains had lost HAPT1 activity. Reintroduction of TbAQP2 in MPXR trypanosomes restored susceptibility to the drugs and reinstated HAPT1 activity, but did not change the activity of TbAT1/P2. Expression of TbAQP2 sensitized Leishmania mexicana promastigotes 40-fold to pentamidine and >1000-fold to melaminophenyl arsenicals and induced a high-affinity pentamidine transport activity indistinguishable from HAPT1 by Km and inhibitor profile. Grafting the TbAQP2 selectivity filter amino acid residues onto a chimeric allele of AQP2 and AQP3 partly restored susceptibility to pentamidine and an arsenical. Conclusions TbAQP2 mediates high-affinity uptake of pentamidine and melaminophenyl arsenicals in trypanosomes and TbAQP2 encodes the previously reported HAPT1 activity. This finding establishes TbAQP2 as an important drug transporter. PMID:24235095

  2. Pentamidine rescues contractility and rhythmicity in a Drosophila model of myotonic dystrophy heart dysfunction.

    PubMed

    Chakraborty, Mouli; Selma-Soriano, Estela; Magny, Emile; Couso, Juan Pablo; Pérez-Alonso, Manuel; Charlet-Berguerand, Nicolas; Artero, Ruben; Llamusi, Beatriz

    2015-12-01

    Up to 80% of individuals with myotonic dystrophy type 1 (DM1) will develop cardiac abnormalities at some point during the progression of their disease, the most common of which is heart blockage of varying degrees. Such blockage is characterized by conduction defects and supraventricular and ventricular tachycardia, and carries a high risk of sudden cardiac death. Despite its importance, very few animal model studies have focused on the heart dysfunction in DM1. Here, we describe the characterization of the heart phenotype in a Drosophila model expressing pure expanded CUG repeats under the control of the cardiomyocyte-specific driver GMH5-Gal4. Morphologically, expression of 250 CUG repeats caused abnormalities in the parallel alignment of the spiral myofibrils in dissected fly hearts, as revealed by phalloidin staining. Moreover, combined immunofluorescence and in situ hybridization of Muscleblind and CUG repeats, respectively, confirmed detectable ribonuclear foci and Muscleblind sequestration, characteristic features of DM1, exclusively in flies expressing the expanded CTG repeats. Similarly to what has been reported in humans with DM1, heart-specific expression of toxic RNA resulted in reduced survival, increased arrhythmia, altered diastolic and systolic function, reduced heart tube diameters and reduced contractility in the model flies. As a proof of concept that the fly heart model can be used for in vivo testing of promising therapeutic compounds, we fed flies with pentamidine, a compound previously described to improve DM1 phenotypes. Pentamidine not only released Muscleblind from the CUG RNA repeats and reduced ribonuclear formation in the Drosophila heart, but also rescued heart arrhythmicity and contractility, and improved fly survival in animals expressing 250 CUG repeats.

  3. Pentamidine rescues contractility and rhythmicity in a Drosophila model of myotonic dystrophy heart dysfunction

    PubMed Central

    Chakraborty, Mouli; Selma-Soriano, Estela; Magny, Emile; Couso, Juan Pablo; Pérez-Alonso, Manuel; Charlet-Berguerand, Nicolas; Artero, Ruben; Llamusi, Beatriz

    2015-01-01

    ABSTRACT Up to 80% of individuals with myotonic dystrophy type 1 (DM1) will develop cardiac abnormalities at some point during the progression of their disease, the most common of which is heart blockage of varying degrees. Such blockage is characterized by conduction defects and supraventricular and ventricular tachycardia, and carries a high risk of sudden cardiac death. Despite its importance, very few animal model studies have focused on the heart dysfunction in DM1. Here, we describe the characterization of the heart phenotype in a Drosophila model expressing pure expanded CUG repeats under the control of the cardiomyocyte-specific driver GMH5-Gal4. Morphologically, expression of 250 CUG repeats caused abnormalities in the parallel alignment of the spiral myofibrils in dissected fly hearts, as revealed by phalloidin staining. Moreover, combined immunofluorescence and in situ hybridization of Muscleblind and CUG repeats, respectively, confirmed detectable ribonuclear foci and Muscleblind sequestration, characteristic features of DM1, exclusively in flies expressing the expanded CTG repeats. Similarly to what has been reported in humans with DM1, heart-specific expression of toxic RNA resulted in reduced survival, increased arrhythmia, altered diastolic and systolic function, reduced heart tube diameters and reduced contractility in the model flies. As a proof of concept that the fly heart model can be used for in vivo testing of promising therapeutic compounds, we fed flies with pentamidine, a compound previously described to improve DM1 phenotypes. Pentamidine not only released Muscleblind from the CUG RNA repeats and reduced ribonuclear formation in the Drosophila heart, but also rescued heart arrhythmicity and contractility, and improved fly survival in animals expressing 250 CUG repeats. PMID:26515653

  4. Menin represses tumorigenesis via repressing cell proliferation

    PubMed Central

    Wu, Ting; Hua, Xianxin

    2011-01-01

    Multiple endocrine neoplasia type 1 (MEN1) results from mutations in the tumor suppressor gene, MEN1, which encodes nuclear protein menin. Menin is important for suppressing tumorigenesis in various endocrine and certain non-endocrine tissues. Although menin suppresses MEN1 through a variety of mechanisms including regulating apoptosis and DNA repair, the role of menin in regulating cell proliferation is one of the best-studied functions. Here, we focus on reviewing various mechanisms underlying menin-mediated inhibition of cell proliferation. Menin inhibits cell proliferation to repress MEN1 through multiple mechanisms. 1) Menin interacts with various histonemodifying enzymes, such as MLL, EZH2 and HDACs, to affect gene transcription, leading to repression of cell proliferation. 2) Menin also interacts with various transcription factors, such as JunD, NF-κB, PPARγ and VDR, to induce or suppress gene transcription. As these various transcription factors are known to regulate cell proliferation, their interaction with menin may be relevant to menin's role in inhibiting cell proliferation. 3) Menin inhibits cell proliferation via TGF-β signaling and Wnt/β-catenin signaling pathways. 4) Menin represses certain pro-proliferative factors involved in endocrine tumors such as IGFBP-2, IGF2 and PTHrP to repress cell proliferation. 5) Menin affects cell cycle progression to inhibit cell proliferation. This review is helpful in our understanding of the comprehensive mechanisms whereby menin represses MEN1 through inhibiting cell proliferation. PMID:22016823

  5. [Management of American cutaneous leishmaniasis. Outcome apropos of 326 cases treated with high-dose pentamidine isethionate].

    PubMed

    Lightburn, E; Morand, J J; Meynard, J B; Kraemer, P; Chaudier, B; Pages, F; Garnotel, E; Patte, J H; Banzet, S; Dampierre, H; Lepage, J; Morillon, M; Boutin, J P; Hovette, P; Chouc, C

    2003-01-01

    The purpose of this retrospective analysis was to evaluate the outcome of pentamidine isethionate treatment (4 mg/kg of Pentamidine by the intramuscular route on Days 1 and 3) of cutaneous leishmaniasis in 326 cases that occurred during an outbreak among French military personnel in French Guyana from 1998 to 1999. A great difference was found between the 205 patients treated in French Guyana (series G) and 32 patients treated at the Laveran Military Hospital in Marseille, France (series L). Failure rate, i.e. 25% in series L versus 5% in series G, was significantly correlated with the delay to treatment which was much longer in series L. Extensive rhabdomyolysis was observed in all cases tested: this side-effect has not been reported. Based on these findings and a review of the literature on pentamidine isethionate, the authors recommend prompt treatment using lower doses. Other treatment alternatives for American cutaneous leishmaniasis are also presented including two of the latest developments in the field, i.e., oral treatment using miltefosine and topical treatment using agents such as paromomycine.

  6. Chimerization at the AQP2–AQP3 locus is the genetic basis of melarsoprol–pentamidine cross-resistance in clinical Trypanosoma brucei gambiense isolates

    PubMed Central

    Graf, Fabrice E.; Baker, Nicola; Munday, Jane C.; de Koning, Harry P.; Horn, David; Mäser, Pascal

    2015-01-01

    Aquaglyceroporin-2 is a known determinant of melarsoprol–pentamidine cross-resistance in Trypanosoma brucei brucei laboratory strains. Recently, chimerization at the AQP2–AQP3 tandem locus was described from melarsoprol–pentamidine cross-resistant Trypanosoma brucei gambiense isolates from sleeping sickness patients in the Democratic Republic of the Congo. Here, we demonstrate that reintroduction of wild-type AQP2 into one of these isolates fully restores drug susceptibility while expression of the chimeric AQP2/3 gene in aqp2–aqp3 null T. b. brucei does not. This proves that AQP2–AQP3 chimerization is the cause of melarsoprol–pentamidine cross-resistance in the T. b. gambiense isolates. PMID:26042196

  7. Searching for repressed memory.

    PubMed

    McNally, Richard J

    2012-01-01

    This chapter summarizes the work of my research group on adults who report either repressed, recovered, or continuous memories of childhood sexual abuse (CSA) or who report no history of CSA. Adapting paradigms from cognitive psychology, we tested hypotheses inspired by both the "repressed memory" and "false memory" perspectives on recovered memories of CSA. We found some evidence for the false memory perspective, but no evidence for the repressed memory perspective. However, our work also suggests a third perspective on recovered memories that does not require the concept of repression. Some children do not understand their CSA when it occurs, and do not experience terror. Years later, they recall the experience, and understanding it as abuse, suffer intense distress. The memory failed to come to mind for years, partly because the child did not encode it as terrifying (i.e., traumatic), not because the person was unable to recall it.

  8. Yeast carbon catabolite repression.

    PubMed

    Gancedo, J M

    1998-06-01

    Glucose and related sugars repress the transcription of genes encoding enzymes required for the utilization of alternative carbon sources; some of these genes are also repressed by other sugars such as galactose, and the process is known as catabolite repression. The different sugars produce signals which modify the conformation of certain proteins that, in turn, directly or through a regulatory cascade affect the expression of the genes subject to catabolite repression. These genes are not all controlled by a single set of regulatory proteins, but there are different circuits of repression for different groups of genes. However, the protein kinase Snf1/Cat1 is shared by the various circuits and is therefore a central element in the regulatory process. Snf1 is not operative in the presence of glucose, and preliminary evidence suggests that Snf1 is in a dephosphorylated state under these conditions. However, the enzymes that phosphorylate and dephosphorylate Snf1 have not been identified, and it is not known how the presence of glucose may affect their activity. What has been established is that Snf1 remains active in mutants lacking either the proteins Grr1/Cat80 or Hxk2 or the Glc7 complex, which functions as a protein phosphatase. One of the main roles of Snf1 is to relieve repression by the Mig1 complex, but it is also required for the operation of transcription factors such as Adr1 and possibly other factors that are still unidentified. Although our knowledge of catabolite repression is still very incomplete, it is possible in certain cases to propose a partial model of the way in which the different elements involved in catabolite repression may be integrated.

  9. Divalent Metal Ion Complexes of S100B in the Absence And Presence 5 of Pentamidine

    SciTech Connect

    Charpentier, T.H.; Wilder, P.T.; Liriano, M.A.; Varney, K.M.; Pozharski, E.; MacKerell, A.D.; Jr.; Coop, A.; Toth, E.A.; Weber, D.J.

    2009-05-12

    As part of an effort to inhibit S100B, structures of pentamidine (Pnt) bound to Ca{sup 2+}-loaded and Zn{sup 2+},Ca{sup 2+}-loaded S100B were determined by X-ray crystallography at 2.15 {angstrom} (R{sub free} = 0.266) and 1.85 {angstrom} (R{sub free} = 0.243) resolution, respectively. These data were compared to X-ray structures solved in the absence of Pnt, including Ca{sup 2+}-loaded S100B and Zn{sup 2+},Ca{sup 2+}-loaded S100B determined here (1.88 {angstrom}; R{sub free} = 0.267). In the presence and absence of Zn{sup 2+}, electron density corresponding to two Pnt molecules per S100B subunit was mapped for both drug-bound structures. One Pnt binding site (site 1) was adjacent to a p53 peptide binding site on S100B ({+-} Zn{sup 2+}), and the second Pnt molecule was mapped to the dimer interface (site 2; {+-} Zn{sup 2+}) and in a pocket near residues that define the Zn{sup 2+} binding site on S100B. In addition, a conformational change in S100B was observed upon the addition of Zn{sup 2+} to Ca{sup 2+}-S100B, which changed the conformation and orientation of Pnt bound to sites 1 and 2 of Pnt-Zn{sup 2+},Ca{sup 2+}-S100B when compared to Pnt-Ca{sup 2+}-S100B. That Pnt can adapt to this Zn{sup 2+}-dependent conformational change was unexpected and provides a new mode for S100B inhibition by this drug. These data will be useful for developing novel inhibitors of both Ca{sup 2+}- and Ca{sup 2+},Zn{sup 2+}-bound S100B.

  10. Structure-In Vitro Activity Relationships of Pentamidine Analogues and Dication-Substituted Bis-Benzimidazoles as New Antifungal Agents

    PubMed Central

    Del Poeta, Maurizio; Schell, Wiley A.; Dykstra, Christine C.; Jones, Susan; Tidwell, Richard R.; Czarny, Agnieszka; Bajic, Miroslav; Bajic, Marina; Kumar, Arvind; Boykin, David; Perfect, John R.

    1998-01-01

    Twenty analogues of pentamidine, 7 primary metabolites of pentamidine, and 30 dicationic substituted bis-benzimidazoles were screened for their inhibitory and fungicidal activities against Candida albicans and Cryptococcus neoformans. A majority of the compounds had MICs at which 80% of the strains were inhibited (MIC80s) comparable to those of amphotericin B and fluconazole. Unlike fluconazole, many of these compounds were found to have potent fungicidal activity. The most potent compound against C. albicans had an MIC80 of ≤0.09 μg/ml, and the most potent compound against C. neoformans had an MIC80 of 0.19 μg/ml. Selected compounds were also found to be active against Aspergillus fumigatus, Fusarium solani, Candida species other than C. albicans, and fluconazole-resistant strains of C. albicans and C. neoformans. It is clear from the data presented here that further studies on the structure-activity relationships, mechanisms of action and toxicities, and in vivo efficacies of these compounds are warranted to determine their clinical potential. PMID:9756747

  11. Efficacy and safety of a single dose pentamidine (7mg/kg) for patients with cutaneous leishmaniasis caused by L. guyanensis: a pilot study*

    PubMed Central

    Gadelha, Ellen Priscilla Nunes; Talhari, Sinésio; Guerra, Jorge Augusto de Oliveira; Neves, Leandro Ourives; Talhari, Carolina; Gontijo, Bernardo; da Silva Junior, Roberto Moreira; Talhari, Anette Chrusciak

    2015-01-01

    BACKGROUND There have been few studies on pentamidine in the Americas; and there is no consensus regarding the dose that should be applied. OBJECTIVES To evaluate the use of pentamidine in a single dose to treat cutaneous leishmaniasis. METHODS Clinical trial of phase II pilot study with 20 patients. Pentamidine was used at a dose of 7 mg/kg, in a single dose. Safety and adverse effects were also assessed. Patients were reviewed one, two, and six months after the end of treatments. RESULTS there was no difference between the treatment groups in relation to gender, age, number or location of the lesions. Pentamidine, applied in a single dose, obtained an effectiveness of 55%. Mild adverse events were reported by 17 (85%) patients, mainly transient pain at the site of applications (85%), while nausea (5%), malaise (5%) and dizziness (5%) were reported in one patient. No patient had sterile abscess after taking medication at a single dose of 7mg/kg. CONCLUSIONS Clinical studies with larger samples of patients would enable a better clinical response of pent amidine at a single dose of 7mg, allowing the application of more powerful statistical tests, thus providing more evidences of the decrease in the effectiveness of that medication. Hence, it is important to have larger studies with new diagrams and/or new medications. PMID:26734860

  12. Racism and Surplus Repression.

    ERIC Educational Resources Information Center

    Johnson, Howard

    1983-01-01

    Explores the relationship between Herbert Marcuse's theory of "surplus repression" and Freud's theory of the "unconscious" with respect to latent, hidden, covert, or subliminal aspects of racism in the United States. Argues that unconscious racism, manifested in evasion/avoidance, acting out/projection, and attempted justification, perpetuates…

  13. Efficacy and Safety of Pafuramidine versus Pentamidine Maleate for Treatment of First Stage Sleeping Sickness in a Randomized, Comparator-Controlled, International Phase 3 Clinical Trial

    PubMed Central

    Pohlig, Gabriele; Bernhard, Sonja C.; Blum, Johannes; Burri, Christian; Mpanya, Alain; Lubaki, Jean-Pierre Fina; Mpoto, Alfred Mpoo; Munungu, Blaise Fungula; N’tombe, Patrick Mangoni; Deo, Gratias Kambau Manesa; Mutantu, Pierre Nsele; Kuikumbi, Florent Mbo; Mintwo, Alain Fukinsia; Munungi, Augustin Kayeye; Dala, Amadeu; Macharia, Stephen; Mesu, Victor Kande Betu Ku; Franco, Jose Ramon; Dituvanga, Ndinga Dieyi; Tidwell, Richard R.; Olson, Carol A.

    2016-01-01

    Background Sleeping sickness (human African trypanosomiasis [HAT]) is a neglected tropical disease with limited treatment options that currently require parenteral administration. In previous studies, orally administered pafuramidine was well tolerated in healthy patients (for up to 21 days) and stage 1 HAT patients (for up to 10 days), and demonstrated efficacy comparable to pentamidine. Methods This was a Phase 3, multi-center, randomized, open-label, parallel-group, active control study where 273 male and female patients with first stage Trypanosoma brucei gambiense HAT were treated at six sites: one trypanosomiasis reference center in Angola, one hospital in South Sudan, and four hospitals in the Democratic Republic of the Congo between August 2005 and September 2009 to support the registration of pafuramidine for treatment of first stage HAT in collaboration with the United States Food and Drug Administration. Patients were treated with either 100 mg of pafuramidine orally twice a day for 10 days or 4 mg/kg pentamidine intramuscularly once daily for 7 days to assess the efficacy and safety of pafuramidine versus pentamidine. Pregnant and lactating women as well as adolescents were included. The primary efficacy endpoint was the combined rate of clinical and parasitological cure at 12 months. The primary safety outcome was the frequency and severity of adverse events. The study was registered on the International Clinical Trials Registry Platform at www.clinicaltrials.gov with the number ISRCTN85534673. Findings/Conclusions The overall cure rate at 12 months was 89% in the pafuramidine group and 95% in the pentamidine group; pafuramidine was non-inferior to pentamidine as the upper bound of the 95% confidence interval did not exceed 15%. The safety profile of pafuramidine was superior to pentamidine; however, 3 patients in the pafuramidine group had glomerulonephritis or nephropathy approximately 8 weeks post-treatment. Two of these events were judged as

  14. S100B-p53 disengagement by pentamidine promotes apoptosis and inhibits cellular migration via aquaporin-4 and metalloproteinase-2 inhibition in C6 glioma cells

    PubMed Central

    CAPOCCIA, ELENA; CIRILLO, CARLA; MARCHETTO, ANNALISA; TIBERI, SAMANTA; SAWIKR, YOUSSEF; PESCE, MARCELLA; D'ALESSANDRO, ALESSANDRA; SCUDERI, CATERINA; SARNELLI, GIOVANNI; CUOMO, ROSARIO; STEARDO, LUCA; ESPOSITO, GIUSEPPE

    2015-01-01

    S100 calcium-binding protein B (S100B) is highly expressed in glioma cells and promotes cancer cell survival via inhibition of the p53 protein. In melanoma cells, this S100B-p53 interaction is known to be inhibited by pentamidine isethionate, an antiprotozoal agent. Thus, the aim of the present study was to evaluate the effect of pentamidine on rat C6 glioma cell proliferation, migration and apoptosis in vitro. The change in C6 cell proliferation following treatment with pentamidine was determined by performing a 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide-formazan assay. Significant dose-dependent decreases in proliferation were observed at pentamidine concentrations of 0.05 µM (58.5±5%; P<0.05), 0.5 µM (40.6±7%; P<0.01) and 5 µM (13±4%; P<0.001) compared with the control (100% viability). Furthermore, treatment with 0.05, 0.5 and 5 µM pentamidine was associated with a significant increase in apoptosis versus the untreated cells, as determined by DNA fragmentation assays, immunofluorescence analysis of C6 chromatin using Hoechst staining, and immunoblot analysis of B-cell lymphoma-2 (Bcl-2)-associated X protein (100%, P<0.05; 453%, P<0.01; and 1000%, P<0.001, respectively) and Bcl-2 (-60%, P<0.001; −80.13%, P<0.001; −95%, P<0.001, respectively). In addition, the administration of 0.05, 0.5 and 5 µM pentamidine significantly upregulated the protein expression levels of p53 (681±87.5%, P<0.05; 1244±94.3%, P<0.01; and 2244±111%, P<0.001, respectively), and significantly downregulated the expression levels of matrix metalloproteinase-2 (42±2.3%, P<0.05; 71±2.5%, P<0.01; and 95.8±3.3%, P<0.001, respectively) and aquaporin 4 (38±2.5%, P<0.05; 69±2.6%, P<0.01; and 88±3.0%, P<0.001, respectively), compared with the untreated cells. The wound healing assay demonstrated that cell migration was significantly impaired by treatment with 0.05, 0.5 and 5 µM pentamidine compared with untreated cells (88±4.2%, P<0.05; 64±2%, P<0.01; and 42

  15. A Combination of Human Embryonic Stem Cell-Derived Pancreatic Endoderm Transplant with LDHA-Repressing miRNA Can Attenuate High-Fat Diet Induced Type II Diabetes in Mice

    PubMed Central

    Chen, Yunya; Wang, Xiujie; Shao, Xinyu

    2015-01-01

    Type II diabetes mellitus (T2D) is a chronic metabolic disorder that results from defects in both insulin secretion and insulin action. The deficit and dysfunction of insulin secreting β-cell are signature symptom for T2D. Additionally, in pancreatic β-cell, a small group of genes which are abundantly expressed in most other tissues are highly selectively repressed. Lactate dehydrogenase A (LDHA) is one of such genes. Upregulation of LDHA is found in both human T2D and rodent T2D models. In this study, we identified a LDHA-suppressing microRNA (hsa-miR-590-3p) and used it together with human embryonic stem cell (hESC) derived pancreatic endoderm (PE) transplantation into a high-fat diet induced T2D mouse model. The procedure significantly improved glucose metabolism and other symptoms of T2D. Our findings support the potential T2D treatment using the combination of microRNA and hESC-differentiated PE cells. PMID:26770982

  16. Technique Selectively Represses Immune System

    MedlinePlus

    ... Research Matters December 3, 2012 Technique Selectively Represses Immune System Myelin (green) encases and protects nerve fibers (brown). A new technique prevents the immune system from attacking myelin in a mouse model of ...

  17. Amplification of KP elements associated with the repression of hybrid dysgenesis in Drosophila melanogaster.

    PubMed

    Jackson, M S; Black, D M; Dover, G A

    1988-12-01

    Mobile P elements in Drosophila melanogaster cause hybrid dysgenesis if their mobility is not repressed. One type of repression, termed P cytotype, is a complex interaction between chromosomes carrying P elements and cytoplasm and is transmitted through the cytoplasm only of females. Another type of repression is found in worldwide M' strains that contain approximately 30 copies per individual of one particular P element deletion-derivative termed the KP element. This repression is transmitted equally through both sexes. In the present study we show that biparentally transmitted repression increases in magnitude together with a rapid increase in KP copy-number in genotypes starting with one or a few KP elements and no other deletion-derivatives. Such correlated increases in repression and KP number per genome occur only in the presence of complete P elements, supporting the interpretation that they are probably a consequence of the selective advantage enjoyed by flies carrying the highest numbers of KP elements. Analysis of Q strains also reveals the presence of qualitative differences in the way the repression of dysgenesis is transmitted. In general, Q strains not containing KP elements have the P cytotype mode of repression, whereas Q strains with KP elements transmit repression through both sexes. This difference among Q strains further supports the existence of at least two types of repression of P-induced hybrid dysgenesis in natural populations of D. melanogaster. PMID:2852140

  18. Amplification of KP elements associated with the repression of hybrid dysgenesis in Drosophila melanogaster.

    PubMed

    Jackson, M S; Black, D M; Dover, G A

    1988-12-01

    Mobile P elements in Drosophila melanogaster cause hybrid dysgenesis if their mobility is not repressed. One type of repression, termed P cytotype, is a complex interaction between chromosomes carrying P elements and cytoplasm and is transmitted through the cytoplasm only of females. Another type of repression is found in worldwide M' strains that contain approximately 30 copies per individual of one particular P element deletion-derivative termed the KP element. This repression is transmitted equally through both sexes. In the present study we show that biparentally transmitted repression increases in magnitude together with a rapid increase in KP copy-number in genotypes starting with one or a few KP elements and no other deletion-derivatives. Such correlated increases in repression and KP number per genome occur only in the presence of complete P elements, supporting the interpretation that they are probably a consequence of the selective advantage enjoyed by flies carrying the highest numbers of KP elements. Analysis of Q strains also reveals the presence of qualitative differences in the way the repression of dysgenesis is transmitted. In general, Q strains not containing KP elements have the P cytotype mode of repression, whereas Q strains with KP elements transmit repression through both sexes. This difference among Q strains further supports the existence of at least two types of repression of P-induced hybrid dysgenesis in natural populations of D. melanogaster.

  19. American cutaneous leishmaniasis caused by Leishmania (Viannia) braziliensis resistant to meglumine antimoniate, but with good response to pentamidine: a case report.

    PubMed

    Pimentel, Maria Inês Fernandes; Baptista, Cibele; Rubin, Evelyn Figueiredo; Vasconcellos, Erica de Camargo Ferreira e; Lyra, Marcelo Rosandiski; Salgueiro, Mariza de Matos; Saheki, Maurício Naoto; Rosalino, Cláudia Maria Valete; Madeira, Maria de Fátima; Silva, Aline Fagundes da; Confort, Eliame Mouta; Schubach, Armando de Oliveira

    2011-01-01

    This is a case report of a Brazilian soldier with cutaneous leishmaniasis. The lesion relapsed following two systemic treatments with meglumine antimoniate. The patient was treated with amphotericin B, which was interrupted due to poor tolerance. Following isolation of Leishmania sp., six intralesional infiltrations of meglumine antimoniate resulted in no response. Leishmania sp promastigotes were again isolated. The patient was submitted to intramuscular 4 mg/kg pentamidine. Parasites from the first and second biopsies were identified as Leishmania (Viannia) braziliensis; those isolated from the first biopsy were more sensitive to meglumine antimoniate in vitro than those isolated from the second biopsy. No relapse was observed.

  20. American cutaneous leishmaniasis caused by Leishmania (Viannia) braziliensis resistant to meglumine antimoniate, but with good response to pentamidine: a case report.

    PubMed

    Pimentel, Maria Inês Fernandes; Baptista, Cibele; Rubin, Evelyn Figueiredo; Vasconcellos, Erica de Camargo Ferreira e; Lyra, Marcelo Rosandiski; Salgueiro, Mariza de Matos; Saheki, Maurício Naoto; Rosalino, Cláudia Maria Valete; Madeira, Maria de Fátima; Silva, Aline Fagundes da; Confort, Eliame Mouta; Schubach, Armando de Oliveira

    2011-01-01

    This is a case report of a Brazilian soldier with cutaneous leishmaniasis. The lesion relapsed following two systemic treatments with meglumine antimoniate. The patient was treated with amphotericin B, which was interrupted due to poor tolerance. Following isolation of Leishmania sp., six intralesional infiltrations of meglumine antimoniate resulted in no response. Leishmania sp promastigotes were again isolated. The patient was submitted to intramuscular 4 mg/kg pentamidine. Parasites from the first and second biopsies were identified as Leishmania (Viannia) braziliensis; those isolated from the first biopsy were more sensitive to meglumine antimoniate in vitro than those isolated from the second biopsy. No relapse was observed. PMID:21552747

  1. Glucose repression in Saccharomyces cerevisiae.

    PubMed

    Kayikci, Ömur; Nielsen, Jens

    2015-09-01

    Glucose is the primary source of energy for the budding yeast Saccharomyces cerevisiae. Although yeast cells can utilize a wide range of carbon sources, presence of glucose suppresses molecular activities involved in the use of alternate carbon sources as well as it represses respiration and gluconeogenesis. This dominant effect of glucose on yeast carbon metabolism is coordinated by several signaling and metabolic interactions that mainly regulate transcriptional activity but are also effective at post-transcriptional and post-translational levels. This review describes effects of glucose repression on yeast carbon metabolism with a focus on roles of the Snf3/Rgt2 glucose-sensing pathway and Snf1 signal transduction in establishment and relief of glucose repression.

  2. Glucose repression in Saccharomyces cerevisiae

    PubMed Central

    Kayikci, Ömur; Nielsen, Jens

    2015-01-01

    Glucose is the primary source of energy for the budding yeast Saccharomyces cerevisiae. Although yeast cells can utilize a wide range of carbon sources, presence of glucose suppresses molecular activities involved in the use of alternate carbon sources as well as it represses respiration and gluconeogenesis. This dominant effect of glucose on yeast carbon metabolism is coordinated by several signaling and metabolic interactions that mainly regulate transcriptional activity but are also effective at post-transcriptional and post-translational levels. This review describes effects of glucose repression on yeast carbon metabolism with a focus on roles of the Snf3/Rgt2 glucose-sensing pathway and Snf1 signal transduction in establishment and relief of glucose repression. PMID:26205245

  3. Pentamidine analogs as inhibitors of [3H]MK-801 and [3H]ifenprodil binding to rat brain NMDA receptors

    PubMed Central

    Berger, Michael L.; Maciejewska, Dorota; Vanden Eynde, Jean Jacques; Mottamal, Madhusoodanan; Żabiński, Jerzy; Kaźmierczak, Paweł; Rezler, Mateusz; Jarak, Ivana; Piantanida, Ivo; Karminski-Zamola, Grace; Mayence, Annie; Rebernik, Patrick; Kumar, Arvind; Ismail, Mohamed A.; Boykin, David W.; Huang, Tien L.

    2016-01-01

    The anti-protozoal drug pentamidine is active against opportunistic Pneumocystis pneumonia, but in addition has several other biological targets, including the NMDA receptor (NR). Here we describe the inhibitory potencies of 76 pentamidine analogs at 2 binding sites of the NR, the channel binding site labeled with [3H]MK-801 and the [3H]ifenprodil binding site. Most analogs acted weaker at the ifenprodil than at the channel site. The spermine-sensitivity of NR inhibition by the majority of the compounds was reminiscent of other long-chain dicationic NR blockers. The potency of the parent compound as NR blocker was increased by modifying the heteroatoms in the bridge connecting the 2 benzamidine moieties and also by integrating the bridge into a seven-membered ring. Docking of the 45 most spermine-sensitive bisbenzamidines to a recently described acidic interface between the N-terminal domains of GluN1 and GluN2B mediating polyamine stimulation of the NR revealed the domain contributed by GluN1 as the most relevant target. PMID:26117647

  4. Pharmacological repression of PPARγ promotes osteogenesis.

    PubMed

    Marciano, David P; Kuruvilla, Dana S; Boregowda, Siddaraju V; Asteian, Alice; Hughes, Travis S; Garcia-Ordonez, Ruben; Corzo, Cesar A; Khan, Tanya M; Novick, Scott J; Park, HaJeung; Kojetin, Douglas J; Phinney, Donald G; Bruning, John B; Kamenecka, Theodore M; Griffin, Patrick R

    2015-06-12

    The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) is the master regulator of adipogenesis and the pharmacological target of the thiazolidinedione (TZD) class of insulin sensitizers. Activation of PPARγ by TZDs promotes adipogenesis at the expense of osteoblast formation, contributing to their associated adverse effects on bone. Recently, we reported the development of PPARγ antagonist SR1664, designed to block the obesity-induced phosphorylation of serine 273 (S273) in the absence of classical agonism, to derive insulin-sensitizing efficacy with improved therapeutic index. Here we identify the structural mechanism by which SR1664 actively antagonizes PPARγ, and extend these findings to develop the inverse agonist SR2595. Treatment of isolated bone marrow-derived mesenchymal stem cells with SR2595 promotes induction of osteogenic differentiation. Together these results identify the structural determinants of ligand-mediated PPARγ repression, and suggest a therapeutic approach to promote bone formation.

  5. Pharmacological Repression of PPARγ Promotes Osteogenesis

    PubMed Central

    Marciano, David P.; Kuruvilla, Dana S.; Boregowda, Siddaraju V.; Asteian, Alice; Hughes, Travis S.; Garcia-Ordonez, Ruben; Corzo, Cesar A.; Khan, Tanya M.; Novick, Scott J.; Park, HaJeung; Kojetin, Douglas J.; Phinney, Donald G.; Bruning, John B.; Kamenecka, Theodore M.; Griffin, Patrick R.

    2015-01-01

    The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) is the master regulator of adipogenesis and the pharmacological target of the thiazolidinedione (TZD) class of insulin sensitizers. Activation of PPARγ by TZDs promotes adipogenesis at the expense of osteoblast formation, contributing to their associated adverse effects on bone. Recently we reported the development of PPARγ antagonist SR1664, designed to block the obesity induced phosphorylation of serine 273 (S273) in the absence of classical agonism, to derive insulin sensitizing efficacy with improved therapeutic index. Here we identify the structural mechanism by which SR1664 actively antagonizes PPARγ, and extend these findings to develop the inverse agonist SR2595. Treatment of isolated bone marrow derived mesenchymal stem cells (MSCs) with SR2595 promotes induction of osteogenic differentiation. Together these results identify the structural determinants of ligand mediated PPARγ repression, and suggest a therapeutic approach to promote bone formation. PMID:26068133

  6. Transient repression of the lac operon.

    PubMed

    Tyler, B; Loomis, W F; Magasanik, B

    1967-12-01

    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. PMID:4864411

  7. Violent repression of environmental protests.

    PubMed

    Poulos, Helen M; Haddad, Mary Alice

    2016-01-01

    As global sea levels and natural resource demands rise, people around the world are increasingly protesting environmental threats to their lives and livelihoods. What are the conditions under which these peaceful environmental protests are violently repressed? This paper uses the random forest algorithm to conduct an event analysis of grassroots environmental protests around the world. Utilizing a database of 175 grassroots environmental protests, we found that: (1) a large proportion (37 %) of the protests involved violent repression; (2) most of the violence (56 %) was directed against marginalized groups; and (3) violence was geographically concentrated the global south in Latin America and Asia. The primary predictors of violence were political empowerment, GDP per capita, industry type, the presence of marginalized groups, and geographic region. Our analysis reveals a complex relationship between governance, resource extraction, and international funding that often resulted in human rights violations against marginalized groups. PMID:27026924

  8. Pentamidine Oral Inhalation

    MedlinePlus

    ... Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for ...

  9. Pentamidine Isethionate Injection

    MedlinePlus

    ... effectiveness and side effects of your treatment using laboratory tests and physical examinations. It is important to keep all appointments with your doctor and the laboratory. The length of treatment depends on how your ...

  10. Gibberellins repress photomorphogenesis in darkness.

    PubMed

    Alabadí, David; Gil, Joan; Blázquez, Miguel A; García-Martínez, José L

    2004-03-01

    Plants undergo two different developmental programs depending on whether they are growing in darkness (skotomorphogenesis) or in the presence of light (photomorphogenesis). It has been proposed that the latter is the default pathway followed by many plants after germination and before the seedling emerges from soil. The transition between the two pathways is tightly regulated. The conserved COP1-based complex is central in the light-dependent repression of photomorphogenesis in darkness. Besides this control, hormones such as brassinosteroids (BRs), cytokinins, auxins, or ethylene also have been shown to regulate, to different extents, this developmental switch. In the present work, we show that the hormone gibberellin (GA) widely participates in this regulation. Studies from Arabidopsis show that both chemical and genetic reductions of endogenous GA levels partially derepress photomorphogenesis in darkness. This is based both on morphological phenotypes, such as hypocotyl elongation and hook and cotyledon opening, and on molecular phenotypes, such as misregulation of the light-controlled genes CAB2 and RbcS. Genetic studies indicate that the GA signaling elements GAI and RGA participate in these responses. Our results also suggest that GA regulation of this response partially depends on BRs. This regulation seems to be conserved across species because lowering endogenous GA levels in pea (Pisum sativum) induces full de-etiolation in darkness, which is not reverted by BR application. Our results, therefore, attribute an important role for GAs in the establishment of etiolated growth and in repression of photomorphogenesis. PMID:14963246

  11. Corepressor system for catabolite repression of the lac operon in Escherichia coli.

    PubMed

    Dobrogosz, W J

    1969-03-01

    Acetylated amino sugars, normally used in the biosynthesis of cell walls and cell membranes, were found to play a role as corepressors for catabolite repression of the lac operon in Escherichia coli. This conclusion was derived from studies conducted on mutants of E. coli that were able to assimilate an exogenous source of N-acetylglucosamine (AcGN) but were unable to dissimilate or grow on this compound. At concentrations less than 10(-4)m, AcGN caused severe catabolite repression of beta-galactosidase synthesis in cultures grown under either nonrepressed or partially repressed conditions. This repression occurred in the absence of any effect of AcGN on either the carbon and energy metabolism or the growth of the organism. In addition, this repression by AcGN occurred in a mutant strain that is constitutive for beta-galactosidase production, demonstrating that the AcGN effect does not involve the uptake of inducer. This model for the corepressor system of catabolite repression is discussed in relation to the existing theories on repression of the lac operon. PMID:4887497

  12. Mitosis-associated repression in development.

    PubMed

    Esposito, Emilia; Lim, Bomyi; Guessous, Ghita; Falahati, Hanieh; Levine, Michael

    2016-07-01

    Transcriptional repression is a pervasive feature of animal development. Here, we employ live-imaging methods to visualize the Snail repressor, which establishes the boundary between the presumptive mesoderm and neurogenic ectoderm of early Drosophila embryos. Snail target enhancers were attached to an MS2 reporter gene, permitting detection of nascent transcripts in living embryos. The transgenes exhibit initially broad patterns of transcription but are refined by repression in the mesoderm following mitosis. These observations reveal a correlation between mitotic silencing and Snail repression. We propose that mitosis and other inherent discontinuities in transcription boost the activities of sequence-specific repressors, such as Snail. PMID:27401553

  13. Perfluoroalkyl Acids Inhibit Reductive Dechlorination of Trichloroethene by Repressing Dehalococcoides.

    PubMed

    Weathers, Tess S; Harding-Marjanovic, Katie; Higgins, Christopher P; Alvarez-Cohen, Lisa; Sharp, Jonathan O

    2016-01-01

    The subsurface recalcitrance of perfluoroalkyl acids (PFAAs) derived from aqueous film-forming foams could have adverse impacts on the microbiological processes used for the bioremediation of co-mingled chlorinated solvents such as trichloroethene (TCE). Here, we show that reductive dechlorination by a methanogenic, mixed culture was significantly inhibited when exposed to concentrations representative of PFAA source zones (>66 mg/L total of 11 PFAA analytes, 6 mg/L each). TCE dechlorination, cis-dichloroethene and vinyl chloride production and dechlorination, and ethene generation were all inhibited at these PFAA concentrations. Phylogenetic analysis revealed that the abundances of 65% of the operational taxonomic units (OTUs) changed significantly when grown in the presence of PFAAs, although repression or enhancement resulting from PFAA exposure did not correlate with putative function or phylogeny. Notably, there was significant repression of Dehalococcoides (8-fold decrease in abundance) coupled with a corresponding enhancement of methane-generating Archaea (a 9-fold increase). Growth and dechlorination by axenic cultures of Dehalococcoides mccartyi strain 195 were similarly repressed under these conditions, confirming an inhibitory response of this pivotal genus to PFAA presence. These results suggest that chlorinated solvent bioattenuation rates could be impeded in subsurface environments near PFAA source zones. PMID:26636352

  14. REPRESSION OF TRYPTOPHANASE SYNTHESIS IN ESCHERICHIA COLI.

    PubMed

    BEGGS, W H; LICHSTEIN, H C

    1965-04-01

    Beggs, William H. (University of Cincinnati, Cincinnati, Ohio), and Herman C. Lichstein. Repression of tryptophanase synthesis in Escherichia coli. J. Bacteriol. 89:996-1004. 1965.-The nature of the glucose effect on tryptophanase in Escherichia coli (Crookes) was investigated to test the catabolite-repression hypothesis. Under static conditions of growth in the presence of 0.005 m glucose, tryptophanase was repressed and remained so upon continued static incubation subsequent to glucose exhaustion. Aeration following glucose exhaustion under static cultural conditions resulted in rapid enzyme synthesis. In the absence of glucose, certain amino acids repressed tryptophanase synthesis early in the growth cycle under aerated conditions. An inverse relationship was observed between the concentration of acid-hydrolyzed casein and the level of tryptophanase. At 3 hr, enzyme activity in cells grown in media containing 0.05% acid-hydrolyzed casein was at least five times that of cells grown in the presence of 1% casein. Addition of 0.005 m d- or l-serine to a 0.05% acid-hydrolyzed casein medium rendered the medium capable of strongly repressing tryptophanase. Glucose-expended medium was prepared by allowing cells to grow and exhaust glucose in static culture. When this expended medium was recovered and inoculated with fresh cells not previously exposed to glucose, tryptophanase synthesis was repressed for a short period in shake culture, but in static culture enzyme synthesis was only slightly affected. When the expended medium was prepared from shake cultures, fresh cells were not repressed strongly when subsequent incubation was carried out aerobically. The tryptophan pool in glucose-repressed cells grown in shake culture was appreciably less than in cells grown in the absence of glucose or in cells undergoing synthesis of tryptophanase after exhaustion of the sugar.

  15. Primal repression: clinical and theoretical aspects.

    PubMed

    Kinston, W; Cohen, J

    1986-01-01

    Primal repression, long an obscure and unusable concept, has been given a precise place in a recent re-working of the theory of repression (Cohen & Kinston, 1984); and this paper specifically examines its properties and presentation. Primal repression refers to an absence of psychic structure which can be made good in the process of emotional growth. It is a part of the mind where trauma persists; and it has a close connexion to the unrepressed unconscious. Direct emergence of primal repression is a threat to life and its activation is therefore risky. During psychoanalysis, primal repression is normally avoided by object-narcissism buttressed by neurotic defences, but it may be reached and worked with in the presence of a non-internalizable valuing and nurturing relationship which we label 'primary relatedness'. This relation is therefore the interactional context for emotional growth. Numerous clinical examples are provided to demonstrate characteristic features of this region of the mind as seen in psychoanalyses. Vignettes illustrate the experiences of patient and analyst as primary relatedness is established; the consequent re-emergence of traumatic states and unmet needs, often initially in the form of severe physical and psychological deterioration; primitive forms of symbolization in the course of repairing primal repression; and the role of action in emotional growth. PMID:2427464

  16. Repression of Escherichia coli carbamoylphosphate synthase: relationships with enzyme synthesis in the arginine and pyrimidine pathways.

    PubMed Central

    Piérard, A; Glansdorff, N; Gigot, D; Crabeel, M; Halleux, P; Thiry, L

    1976-01-01

    Cumulative repression of Escherichia coli carbamoylphosphate synthase (CPSase; EC 2.7.2.9) by arginine and pyrimidine was analyzed in relation to control enzyme synthesis in the arginine and pyrimidine pathways. The expression of carA and carB, the adjacent genes that specify the two subunits of the enzyme, was estimated by means of an in vitro complementation assay. The synthesis of each gene product was found to be under repression control. Coordinate expression of the two genes was observed under most conditions investigated. They might thus form an operon. The preparation of strains blocked in the degradation of cytidine and harboring leaky mutations affecting several steps of pyrimidine nucleotide synthesis made it possible to distinguish between the effects of cytidine and uridine compounds in the repression of the pyrimidine pathway enzymes. The data obtained suggest that derivatives of both cytidine and uridine participate in the repression of CPSase. In addition, repression of CPSase by arginine did not appear to occur unless pyrimidines were present at a significant intracellular concentration. This observation, together with our previous report that argR mutations impair the cumulative repression of CPSase, suggests that this control is mediated through the concerted effects of regulatory elements specific for the arginine and pyrimidine pathways. PMID:179975

  17. CD4 T Cell-Derived IFN-γ Plays a Minimal Role in Control of Pulmonary Mycobacterium tuberculosis Infection and Must Be Actively Repressed by PD-1 to Prevent Lethal Disease

    PubMed Central

    Sakai, Shunsuke; Kauffman, Keith D.; Sallin, Michelle A.; Sharpe, Arlene H.; Young, Howard A.; Ganusov, Vitaly V.; Barber, Daniel L.

    2016-01-01

    IFN-γ–producing CD4 T cells are required for protection against Mycobacterium tuberculosis (Mtb) infection, but the extent to which IFN-γ contributes to overall CD4 T cell-mediated protection remains unclear. Furthermore, it is not known if increasing IFN-γ production by CD4 T cells is desirable in Mtb infection. Here we show that IFN-γ accounts for only ~30% of CD4 T cell-dependent cumulative bacterial control in the lungs over the first six weeks of infection, but >80% of control in the spleen. Moreover, increasing the IFN-γ–producing capacity of CD4 T cells by ~2 fold exacerbates lung infection and leads to the early death of the host, despite enhancing control in the spleen. In addition, we show that the inhibitory receptor PD-1 facilitates host resistance to Mtb by preventing the detrimental over-production of IFN-γ by CD4 T cells. Specifically, PD-1 suppressed the parenchymal accumulation of and pathogenic IFN-γ production by the CXCR3+KLRG1-CX3CR1- subset of lung-homing CD4 T cells that otherwise mediates control of Mtb infection. Therefore, the primary role for T cell-derived IFN-γ in Mtb infection is at extra-pulmonary sites, and the host-protective subset of CD4 T cells requires negative regulation of IFN-γ production by PD-1 to prevent lethal immune-mediated pathology. PMID:27244558

  18. Fluticasone propionate and pentamidine isethionate reduce airway hyperreactivity, pulmonary eosinophilia and pulmonary dendritic cell response in a guinea pig model of asthma.

    PubMed

    Lawrence, T E; Millecchia, L L; Fedan, J S

    1998-01-01

    In this study, we examined the effects of fluticasone propionate (FP) and pentamidine isethionate (PI) on antigen-induced lung inflammation and airway hyperreactivity in guinea pigs. Male guinea pigs were sensitized on days 0 and 14 with 10 micrograms of ovalbumin (OVA) plus 1 mg of Al(OH)3. On day 21, animals were challenged with a 2% OVA aerosol inhalation until they developed pulmonary obstruction. Animals were treated with aerosol inhalation of FP (2 ml of 0.5 mg/ml, five consecutive doses at 12-hr intervals with the last dose given 6 hr before OVA challenge) or PI (30 mg/ml for 30 min 1 hr before OVA challenge), and control animals received no drug before OVA challenge. Airway reactivity to methacholine (MCh) was assessed before sensitization and 18 hr after OVA challenge. At 18 hr after challenge, histological sections of trachea and lung were examined for eosinophil, dendritic cell (DC) and macrophage cell densities in the airways. In control animals, OVA evoked airway hyperreactivity to MCh in conjunction with pulmonary eosinophilia and increases in DC prevalence in the trachea and bronchi. Treatment with FP or PI abolished the OVA-induced hyperresponsiveness and significantly reduced the OVA-induced increases in eosinophils and DCs in the airways. FP and PI had no effect on saline-treated animals. Our study indicates that both inhaled FP and inhaled PI reduce antigen-induced airway hyperreactivity and pulmonary inflammation in guinea pigs. The results also suggest that the DC is a target of the anti-inflammatory effects of these drugs in the airways. PMID:9435182

  19. Efficient transgene expression by alleviation of translational repression in plant cells.

    PubMed

    Ueda, Kiyotaka; Okawara, Renya; Yamasaki, Shotaro; Sanada, Yuji; Kinoshita, Eri; Yoneda, Arata; Demura, Taku; Kato, Ko

    2014-10-01

    Global translational repression under abiotic stress influences translation of both endogenous and transgene mRNAs. Even in plant cell culture, hypoxia and nutrient deficient stress arise during the growth process. In this study, we first demonstrated the existence of global translational repression in Arabidopsis T87 cultured cells over a time course following inoculation. Next, we performed genome-wide analysis, which revealed that the translational states of endogenous mRNAs differed significantly between growth and stationary phase cells. This analysis showed that translation from most mRNAs was repressed upon stationary phase. Otherwise, a part of mRNA including alcohol dehydrogenase (ADH) gene was recalcitrant to the repression. Furthermore, by polysome analysis and followed quantitative reverse transcription PCR analysis of transformants having 5'untranslated regions (UTRs) of ADH or translationally repressed At3g47610 mRNA fused to reporter gene, we demonstrated that polysomal associations of reporter mRNAs were in accordance with those the mRNAs from which their 5'UTR derived, suggesting that the 5'UTR is an important determinant of the translational state of mRNAs in stationary phase cells. Finally, we demonstrated the effectiveness of 5'UTR of ADH mRNA in transformants derived from the BY-2 tobacco cell line. These results suggested that 5'UTR of ADH mRNA would be a useful element for efficient transgene expression upon stationary phase.

  20. The great repression: chromatin and cryptic transcription.

    PubMed

    Hennig, Bianca P; Fischer, Tamás

    2013-01-01

    The eukaryotic chromatin structure is essential in correctly defining transcription units. Impairing this structure can activate cryptic promoters, and lead to the accumulation of aberrant RNA transcripts. Here we discuss critical pathways that are responsible for the repression of cryptic transcription and the maintenance of genome integrity.

  1. Repression of Pseudomonas putida phenanthrene-degrading activity by plant root extracts and exudates.

    PubMed

    Rentz, Jeremy A; Alvarez, Pedro J J; Schnoor, Jerald L

    2004-06-01

    The phenanthrene-degrading activity (PDA) of Pseudomonas putida ATCC 17484 was repressed after incubation with plant root extracts of oat (Avena sativa), osage orange (Maclura pomifera), hybrid willow (Salix alba x matsudana), kou (Cordia subcordata) and milo (Thespesia populnea) and plant root exudates of oat (Avena sativa) and hybrid poplar (Populus deltoides x nigra DN34). Total organic carbon content of root extracts ranged from 103 to 395 mg l(-1). Characterization of root extracts identified acetate (not detectable to 8.0 mg l(-1)), amino acids (1.7-17.3 mg l(-1)) and glucose (1.6-14.0 mg l(-1)), indicating a complex mixture of substrates. Repression was also observed after exposure to potential root-derived substrates, including organic acids, glucose (carbohydrate) and glutamate (amino acid). Carbon source regulation (e.g. catabolite repression) was apparently responsible for the observed repression of P. putida PDA by root extracts. However, we showed that P. putida grows on root extracts and exudates as sole carbon and energy sources. Enhanced growth on root products may compensate for partial repression, because larger microbial populations are conducive to faster degradation rates. This would explain the commonly reported increase in phenanthrene removal in the rhizosphere.

  2. MYCN repression of Lifeguard/FAIM2 enhances neuroblastoma aggressiveness.

    PubMed

    Planells-Ferrer, L; Urresti, J; Soriano, A; Reix, S; Murphy, D M; Ferreres, J C; Borràs, F; Gallego, S; Stallings, R L; Moubarak, R S; Segura, M F; Comella, J X

    2014-09-04

    Neuroblastoma (NBL) is the most common solid tumor in infants and accounts for 15% of all pediatric cancer deaths. Several risk factors predict NBL outcome: age at the time of diagnosis, stage, chromosome alterations and MYCN (V-Myc Avian Myelocytomatosis Viral Oncogene Neuroblastoma-Derived Homolog) amplification, which characterizes the subset of the most aggressive NBLs with an overall survival below 30%. MYCN-amplified tumors develop exceptional chemoresistance and metastatic capacity. These properties have been linked to defects in the apoptotic machinery, either by silencing components of the extrinsic apoptotic pathway (e.g. caspase-8) or by overexpression of antiapoptotic regulators (e.g. Bcl-2, Mcl-1 or FLIP). Very little is known on the implication of death receptors and their antagonists in NBL. In this work, the expression levels of several death receptor antagonists were analyzed in multiple human NBL data sets. We report that Lifeguard (LFG/FAIM2 (Fas apoptosis inhibitory molecule 2)/NMP35) is downregulated in the most aggressive and undifferentiated tumors. Intringuingly, although LFG has been initially characterized as an antiapoptotic protein, we have found a new association with NBL differentiation. Moreover, LFG repression resulted in reduced cell adhesion, increased sphere growth and enhanced migration, thus conferring a higher metastatic capacity to NBL cells. Furthermore, LFG expression was found to be directly repressed by MYCN at the transcriptional level. Our data, which support a new functional role for a hitherto undiscovered MYCN target, provide a new link between MYCN overexpression and increased NBL metastatic properties.

  3. Nuclear AXIN2 represses MYC gene expression

    SciTech Connect

    Rennoll, Sherri A.; Konsavage, Wesley M.; Yochum, Gregory S.

    2014-01-03

    Highlights: •AXIN2 localizes to cytoplasmic and nuclear compartments in colorectal cancer cells. •Nuclear AXIN2 represses the activity of Wnt-responsive luciferase reporters. •β-Catenin bridges AXIN2 to TCF transcription factors. •AXIN2 binds the MYC promoter and represses MYC gene expression. -- Abstract: The β-catenin transcriptional coactivator is the key mediator of the canonical Wnt signaling pathway. In the absence of Wnt, β-catenin associates with a cytosolic and multi-protein destruction complex where it is phosphorylated and targeted for proteasomal degradation. In the presence of Wnt, the destruction complex is inactivated and β-catenin translocates into the nucleus. In the nucleus, β-catenin binds T-cell factor (TCF) transcription factors to activate expression of c-MYC (MYC) and Axis inhibition protein 2 (AXIN2). AXIN2 is a member of the destruction complex and, thus, serves in a negative feedback loop to control Wnt/β-catenin signaling. AXIN2 is also present in the nucleus, but its function within this compartment is unknown. Here, we demonstrate that AXIN2 localizes to the nuclei of epithelial cells within normal and colonic tumor tissues as well as colorectal cancer cell lines. In the nucleus, AXIN2 represses expression of Wnt/β-catenin-responsive luciferase reporters and forms a complex with β-catenin and TCF. We demonstrate that AXIN2 co-occupies β-catenin/TCF complexes at the MYC promoter region. When constitutively localized to the nucleus, AXIN2 alters the chromatin structure at the MYC promoter and directly represses MYC gene expression. These findings suggest that nuclear AXIN2 functions as a rheostat to control MYC expression in response to Wnt/β-catenin signaling.

  4. Transthyretin represses neovascularization in diabetic retinopathy

    PubMed Central

    Shao, Jun

    2016-01-01

    Purpose The apoptosis of human umbilical vein endothelial cells has been reportedly induced by the protein transthyretin (TTR). In human ocular tissue, TTR is generally considered to be secreted mainly by retinal pigment epithelial cells (hRPECs); however, whether TTR affects the development of neovascularization in diabetic retinopathy (DR) remains unclear. Methods Natural and simulated DR media were used to culture human retinal microvascular endothelial cells (hRECs). Hyperglycemia was simulated by increasing the glucose concentration from 5.5 mM up to 25 mM, while hypoxia was induced with 200 µM CoCl2. To understand the effects of TTR on hRECs, cell proliferation was investigated under natural and DR conditions. Overexpression of TTR, an in vitro wound-healing assay, and a tube formation assay were employed to study the repression of TTR on hRECs. Real-time fluorescence quantitative PCR (qRT-PCR) was used to study the mRNA levels of DR-related genes, such as Tie2, VEGFR1, VEGFR2, Angpt1, and Angpt2. Results The proliferation of hRECs was significantly decreased in the simulated hyperglycemic and hypoxic DR environments. The cells were further repressed by added exogenous or endogenous TTR only under hyperglycemic conditions. The in vitro migration and tube formation processes of the hRECs were inhibited with TTR; furthermore, in the hyperglycemia and hyperglycemia/hypoxia environments, the levels of Tie2 and Angpt1 mRNA were enhanced with exogenous TTR, while those of VEGFR1, VEGFR2, and Angpt1 were repressed. Conclusions In hyperglycemia, the proliferation, migration, and neovascularization of hRECs were significantly inhibited by TTR. The key genes for DR neovascularization, including Tie2, VEGFR1, VEGFR2, Angpt1, and Angpt2, were regulated by TTR. Under DR conditions, TTR significantly represses neovascularization by inhibiting the proliferation, migration and tube formation of hRECs. PMID:27746673

  5. Memory repression: brain mechanisms underlying dissociative amnesia.

    PubMed

    Kikuchi, Hirokazu; Fujii, Toshikatsu; Abe, Nobuhito; Suzuki, Maki; Takagi, Masahito; Mugikura, Shunji; Takahashi, Shoki; Mori, Etsuro

    2010-03-01

    Dissociative amnesia usually follows a stressful event and cannot be attributable to explicit brain damage. It is thought to reflect a reversible deficit in memory retrieval probably due to memory repression. However, the neural mechanisms underlying this condition are not clear. We used fMRI to investigate neural activity associated with memory retrieval in two patients with dissociative amnesia. For each patient, three categories of face photographs and three categories of people's names corresponding to the photographs were prepared: those of "recognizable" high school friends who were acquainted with and recognizable to the patients, those of "unrecognizable" colleagues who were actually acquainted with but unrecognizable to the patients due to their memory impairments, and "control" distracters who were unacquainted with the patients. During fMRI, the patients were visually presented with these stimuli and asked to indicate whether they were personally acquainted with them. In the comparison of the unrecognizable condition with the recognizable condition, we found increased activity in the pFC and decreased activity in the hippocampus in both patients. After treatment for retrograde amnesia, the altered pattern of brain activation disappeared in one patient whose retrograde memories were recovered, whereas it remained unchanged in the other patient whose retrograde memories were not recovered. Our findings provide direct evidence that memory repression in dissociative amnesia is associated with an altered pattern of neural activity, and they suggest the possibility that the pFC has an important role in inhibiting the activity of the hippocampus in memory repression.

  6. Benzamidine derivatives inhibit the virulence of Porphyromonas gingivalis

    PubMed Central

    Fröhlich, Esther; Kantyka, Tomasz; Plaza, Karolina; Schmidt, Karl-Hermann; Pfister, Wolfgang; Potempa, Jan; Eick, Sigrun

    2012-01-01

    SUMMARY We have previously shown that benzamidine-type compoundscan inhibit the activity of arginine-specific cysteine proteinases (gingipainsHRgpA and RgpB); well-known virulence factors of Porphyromonas gingivalis. They also hinder in vitro growth of this important period on to pathogenic bacterium. Apparently growth arrest is not associated with their ability to inhibit these proteases, as pentamidine, which is a 20-fold less efficient inhibitor of gingipainthan 2,6-bis-(4-amidinobenzyl)-cyclohexanone (ACH), blocked P. gingivalis growth far more effectively. To identify targets for benzamidine-derived compounds other than Arg-gingipains, and to explain their bacteriostatic effects, P. gingivalis ATCC 33277 and P. gingivalis M5-1-2 (clinical isolate) cell extracts were subjected to affinity chromatography using a benzamidine-Sepharose column to identify proteins interacting withbenzamidine. In addition to HRgpA and RgpB the analysis revealed heat-shock protein GroELas another ligand forbenzamidine. To better understand the effect ofbenzamidine-derived compounds on P. gingivalis, bacteria were exposed to benzamidine, pentamidine, ACH and heat, and the expression of gingipains and GroEL was determined. Exposure to heat and benzamidine-derived compounds caused significant increasesin GroEL, both at the mRNA and protein levels. Interestingly, despite the fact that gingipains were shown to be the main virulence factors in a fertilized egg model of infection, mortality rates were strongly reduced, not only by ACH, but also bypentamidine, a relatively week gingipain inhibitor. This effect may depend not only ongingipain inhibition but also oninteraction of benzamidine derivatives with GroEL. Therefore these compounds may find use in supportive periodontitis treatment. PMID:23279840

  7. Zeste maintains repression of Ubx transgenes: Support for a new model of polycomb repression

    SciTech Connect

    Hur, Man-Wook; Laney, Jeffrey D.; Jeon, Sang-Hack; Ali, Janann; Biggin, Mark D.

    2001-09-01

    During late embryogenesis, the expression domains of homeotic genes are maintained by two groups of ubiquitously expressed regulators: the Polycomb repressors and the Trithorax activators. It is not known how the activities of the two maintenance systems are initially targeted to the correct genes. Zeste and GAGA are sequence specific DNA binding proteins previously shown to be Trithorax group activators of the homeotic gene Ultrabithorax (Ubx). Here we demonstrate that Zeste and GAGA DNA binding sites at the proximal promoter are also required to maintain, but not to initiate, repression of Ubx. Further, the repression mediated by Zeste DNA binding site is abolished in zeste null embryos. These data imply that Zeste and probably GAGA mediate Polycomb repression. We present a model in which the dual transcriptional activities of Zeste and GAGA are an essential component of the mechanism that chooses which maintenance system is to be targeted to a given promoter.

  8. [Induction and repression of the collagenase synthesis in Acinetobacter sp].

    PubMed

    Monboisse, J C; Labadie, J; Gouet, P

    1979-05-01

    The synthesis of collagenase in Acinetobacter sp. was found to be inducible by denatured collagen and by its high molecular weight fragments. The presence in the inducer of part of the tertiary structure appear to be indispensable. On the other hand, an addition of Casamino acids, meat protein hydrolysate, or a mixture of amino acids with a similar composition to gelatin does not stimulate collagenase synthesis. Enzyme production was severely repressed in the early phase of growth by glucose, arabinose, and ribose, single amino acids, proline, hydroxyproline, alanine, glutamic acid or casein acid hydrolysate. A mechanism of repression similar to catabolite repression was involved in the phenomenon caused by carbohydrates. However, the fact that cyclic adenosine 3'5-monophosphate did not overcome the repression caused by amino acids or Casamino acids, in contrast to classical catabolite repression, suggests that these two forms of repression may be distinct.

  9. MeCP2 repression of G9a in regulation of pain and morphine reward.

    PubMed

    Zhang, Zhi; Tao, Wenjuan; Hou, Yuan-Yuan; Wang, Wei; Kenny, Paul J; Pan, Zhizhong Z

    2014-07-01

    Opioids are commonly used for pain relief, but their strong rewarding effects drive opioid misuse and abuse. How pain affects the liability of opioid abuse is unknown at present. In this study, we identified an epigenetic regulating cascade activated by both pain and the opioid morphine. Both persistent pain and repeated morphine upregulated the transcriptional regulator MeCP2 in mouse central nucleus of the amygdala (CeA). Chromatin immunoprecipitation analysis revealed that MeCP2 bound to and repressed the transcriptional repressor histone dimethyltransferase G9a, reducing G9a-catalyzed repressive mark H3K9me2 in CeA. Repression of G9a activity increased expression of brain-derived neurotrophic factor (BDNF). Behaviorally, persistent inflammatory pain increased the sensitivity to acquiring morphine-induced, reward-related behavior of conditioned place preference in mice. Local viral vector-mediated MeCP2 overexpression, Cre-induced G9a knockdown, and CeA application of BDNF mimicked, whereas MeCP2 knockdown inhibited, the pain effect. These results suggest that MeCP2 directly represses G9a as a shared mechanism in central amygdala for regulation of emotional responses to pain and opioid reward, and for their behavioral interaction.

  10. Mechanism of catabolite repression of tryptophanase synthesis in Escherichia coli.

    PubMed

    Isaacs, H; Chao, D; Yanofsky, C; Saier, M H

    1994-08-01

    Repression of tryptophanase (tryptophan indole-lyase) by glucose and its non-metabolizable analogue methyl alpha-glucoside has been studied employing a series of isogenic strains of Escherichia coli lacking cyclic AMP phosphodiesterase and altered for two of the proteins of the phosphoenolpyruvate:sugar phosphotransferase system (PTS), Enzyme I and Enzyme IIAGlc. Basal activity of tryptophanase was depressed mildly by inclusion of glucose in the growth medium, but inducible tryptophanase synthesis was subject to strong glucose repression in the parental strain, which exhibited normal PTS enzyme activities. Methyl alpha-glucoside was without effect in this strain. Loss of Enzyme I decreased sensitivity to repression by glucose but enhanced sensitivity to repression by methyl alpha-glucoside. Loss of Enzyme IIAGlc activity largely abolished repression by methyl alpha-glucoside but had a less severe effect on glucose repression. The repressive effects of both sugars were fully reversed by inclusion of cyclic AMP in the growth medium. Tryptophan uptake under the same conditions was inhibited weakly by glucose and more strongly by methyl alpha-glucoside in the parental strain. Inhibition by both sugars was alleviated by partial loss of Enzyme I. Inhibition by methyl alpha-glucoside appeared to be largely due to energy competition and was not responsible for repression of tryptophanase synthesis. Measurement of net production of cyclic AMP as well as intracellular concentrations of cyclic AMP revealed a good correlation with intensity of repression. The results suggest that while basal tryptophanase synthesis is relatively insensitive to catabolite repression, inducible synthesis is subject to strong repression by two distinct mechanisms, one dependent on enzyme IIAGlc of the PTS and the other independent of this protein. Both mechanisms are attributable to depressed rates of cyclic AMP synthesis. No evidence for a cyclic-AMP-independent mechanism of catabolite

  11. BEND3 mediates transcriptional repression and heterochromatin organization.

    PubMed

    Khan, Abid; Prasanth, Supriya G

    2015-01-01

    Transcription repression plays a central role in gene regulation. Transcription repressors utilize diverse strategies to mediate transcriptional repression. We have recently demonstrated that BEND3 (BANP, E5R and Nac1 domain) protein represses rDNA transcription by stabilizing a NoRC component. We discuss the role of BEND3 as a global regulator of gene expression and propose a model whereby BEND3 associates with chromatin remodeling complexes to modulate gene expression and heterochromatin organization.

  12. BEND3 mediates transcriptional repression and heterochromatin organization

    PubMed Central

    Khan, Abid; Prasanth, Supriya G

    2015-01-01

    Transcription repression plays a central role in gene regulation. Transcription repressors utilize diverse strategies to mediate transcriptional repression. We have recently demonstrated that BEND3 (BANP, E5R and Nac1 domain) protein represses rDNA transcription by stabilizing a NoRC component. We discuss the role of BEND3 as a global regulator of gene expression and propose a model whereby BEND3 associates with chromatin remodeling complexes to modulate gene expression and heterochromatin organization. PMID:26507581

  13. BEND3 mediates transcriptional repression and heterochromatin organization.

    PubMed

    Khan, Abid; Prasanth, Supriya G

    2015-01-01

    Transcription repression plays a central role in gene regulation. Transcription repressors utilize diverse strategies to mediate transcriptional repression. We have recently demonstrated that BEND3 (BANP, E5R and Nac1 domain) protein represses rDNA transcription by stabilizing a NoRC component. We discuss the role of BEND3 as a global regulator of gene expression and propose a model whereby BEND3 associates with chromatin remodeling complexes to modulate gene expression and heterochromatin organization. PMID:26507581

  14. MYCN repression of Lifeguard/FAIM2 enhances neuroblastoma aggressiveness

    PubMed Central

    Planells-Ferrer, L; Urresti, J; Soriano, A; Reix, S; Murphy, D M; Ferreres, J C; Borràs, F; Gallego, S; Stallings, R L; Moubarak, R S; Segura, M F; Comella, J X

    2014-01-01

    Neuroblastoma (NBL) is the most common solid tumor in infants and accounts for 15% of all pediatric cancer deaths. Several risk factors predict NBL outcome: age at the time of diagnosis, stage, chromosome alterations and MYCN (V-Myc Avian Myelocytomatosis Viral Oncogene Neuroblastoma-Derived Homolog) amplification, which characterizes the subset of the most aggressive NBLs with an overall survival below 30%. MYCN-amplified tumors develop exceptional chemoresistance and metastatic capacity. These properties have been linked to defects in the apoptotic machinery, either by silencing components of the extrinsic apoptotic pathway (e.g. caspase-8) or by overexpression of antiapoptotic regulators (e.g. Bcl-2, Mcl-1 or FLIP). Very little is known on the implication of death receptors and their antagonists in NBL. In this work, the expression levels of several death receptor antagonists were analyzed in multiple human NBL data sets. We report that Lifeguard (LFG/FAIM2 (Fas apoptosis inhibitory molecule 2)/NMP35) is downregulated in the most aggressive and undifferentiated tumors. Intringuingly, although LFG has been initially characterized as an antiapoptotic protein, we have found a new association with NBL differentiation. Moreover, LFG repression resulted in reduced cell adhesion, increased sphere growth and enhanced migration, thus conferring a higher metastatic capacity to NBL cells. Furthermore, LFG expression was found to be directly repressed by MYCN at the transcriptional level. Our data, which support a new functional role for a hitherto undiscovered MYCN target, provide a new link between MYCN overexpression and increased NBL metastatic properties. PMID:25188511

  15. ATRX represses alternative lengthening of telomeres.

    PubMed

    Napier, Christine E; Huschtscha, Lily I; Harvey, Adam; Bower, Kylie; Noble, Jane R; Hendrickson, Eric A; Reddel, Roger R

    2015-06-30

    The unlimited proliferation of cancer cells requires a mechanism to prevent telomere shortening. Alternative Lengthening of Telomeres (ALT) is an homologous recombination-mediated mechanism of telomere elongation used in tumors, including osteosarcomas, soft tissue sarcoma subtypes, and glial brain tumors. Mutations in the ATRX/DAXX chromatin remodeling complex have been reported in tumors and cell lines that use the ALT mechanism, suggesting that ATRX may be an ALT repressor. We show here that knockout or knockdown of ATRX in mortal cells or immortal telomerase-positive cells is insufficient to activate ALT. Notably, however, in SV40-transformed mortal fibroblasts ATRX loss results in either a significant increase in the proportion of cell lines activating ALT (instead of telomerase) or in a significant decrease in the time prior to ALT activation. These data indicate that loss of ATRX function cooperates with one or more as-yet unidentified genetic or epigenetic alterations to activate ALT. Moreover, transient ATRX expression in ALT-positive/ATRX-negative cells represses ALT activity. These data provide the first direct, functional evidence that ATRX represses ALT.

  16. Repression of gene expression by oxidative stress.

    PubMed Central

    Morel, Y; Barouki, R

    1999-01-01

    Gene expression is modulated by both physiological signals (hormones, cytokines, etc.) and environmental stimuli (physical parameters, xenobiotics, etc.). Oxidative stress appears to be a key pleiotropic modulator which may be involved in either pathway. Indeed, reactive oxygen species (ROS) have been described as second messengers for several growth factors and cytokines, but have also been shown to rise following cellular insults such as xenobiotic metabolism or enzymic deficiency. Extensive studies on the induction of stress-response genes by oxidative stress have been reported. In contrast, owing to the historical focus on gene induction, less attention has been paid to gene repression by ROS. However, a growing number of studies have shown that moderate (i.e. non-cytotoxic) oxidative stress specifically down-regulates the expression of various genes. In this review, we describe the alteration of several physiological functions resulting from oxidative-stress-mediated inhibition of gene transcription. We will then focus on the repressive oxidative modulation of various transcription factors elicited by ROS. PMID:10477257

  17. Laser Isotope Separation Employing Condensation Repression

    SciTech Connect

    Eerkens, Jeff W.; Miller, William H.

    2004-09-15

    Molecular laser isotope separation (MLIS) techniques using condensation repression (CR) harvesting are reviewed and compared with atomic vapor laser isotope separation (AVLIS), gaseous diffusion (DIF), ultracentrifuges (UCF), and electromagnetic separations (EMS). Two different CR-MLIS or CRISLA (Condensation Repression Isotope Separation by Laser Activation) approaches have been under investigation at the University of Missouri (MU), one involving supersonic super-cooled free jets and dimer formation, and the other subsonic cold-wall condensation. Both employ mixtures of an isotopomer (e.g. {sup i}QF{sub 6}) and a carrier gas, operated at low temperatures and pressures. Present theories of VT relaxation, dimerization, and condensation are found to be unsatisfactory to explain/predict experimental CRISLA results. They were replaced by fundamentally new models that allow ab-initio calculation of isotope enrichments and predictions of condensation parameters for laser-excited and non-excited vapors which are in good agreement with experiment. Because of supersonic speeds, throughputs for free-jet CRISLA are a thousand times higher than cold-wall CRISLA schemes, and thus preferred for large-quantity Uranium enrichments. For small-quantity separations of (radioactive) medical isotopes, the simpler coldwall CRISLA method may be adequate.

  18. Repression of somatic cell fate in the germline.

    PubMed

    Robert, Valérie J; Garvis, Steve; Palladino, Francesca

    2015-10-01

    Germ cells must transmit genetic information across generations, and produce gametes while also maintaining the potential to form all cell types after fertilization. Preventing the activation of somatic programs is, therefore, crucial to the maintenance of germ cell identity. Studies in Caenorhabditis elegans, Drosophila melanogaster, and mouse have revealed both similarities and differences in how somatic gene expression is repressed in germ cells, thereby preventing their conversion into somatic tissues. This review will focus on recent developments in our understanding of how global or gene-specific transcriptional repression, chromatin regulation, and translational repression operate in the germline to maintain germ cell identity and repress somatic differentiation programs. PMID:26043973

  19. SAGA complex components and acetate repression in Aspergillus nidulans.

    PubMed

    Georgakopoulos, Paraskevi; Lockington, Robin A; Kelly, Joan M

    2012-11-01

    Alongside the well-established carbon catabolite repression by glucose and other sugars, acetate causes repression in Aspergillus nidulans. Mutations in creA, encoding the transcriptional repressor involved in glucose repression, also affect acetate repression, but mutations in creB or creC, encoding components of a deubiquitination system, do not. To understand the effects of acetate, we used a mutational screen that was similar to screens that uncovered mutations in creA, creB, and creC, except that glucose was replaced by acetate to identify mutations that were affected for repression by acetate but not by glucose. We uncovered mutations in acdX, homologous to the yeast SAGA component gene SPT8, which in growth tests showed derepression for acetate repression but not for glucose repression. We also made mutations in sptC, homologous to the yeast SAGA component gene SPT3, which showed a similar phenotype. We found that acetate repression is complex, and analysis of facA mutations (lacking acetyl CoA synthetase) indicates that acetate metabolism is required for repression of some systems (proline metabolism) but not for others (acetamide metabolism). Although plate tests indicated that acdX- and sptC-null mutations led to derepressed alcohol dehydrogenase activity, reverse-transcription quantitative real-time polymerase chain reaction showed no derepression of alcA or aldA but rather elevated induced levels. Our results indicate that acetate repression is due to repression via CreA together with metabolic changes rather than due to an independent regulatory control mechanism.

  20. Catabolite repression and inducer control in Gram-positive bacteria.

    PubMed

    Saier, M H; Chauvaux, S; Cook, G M; Deutscher, J; Paulsen, I T; Reizer, J; Ye, J J

    1996-02-01

    Results currently available clearly indicate that the metabolite-activated protein kinase-mediated phosphorylation of Ser-46 in HPr plays a key role in catabolite repression and the control of inducer levels in low-GC Gram-positive bacteria. This protein kinase is not found in enteric bacteria such as E. coli and Salmonella typhimurium where an entirely different PTS-mediated regulatory mechanism is responsible for catabolite repression and inducer concentration control. In Table 2 these two mechanistically dissimilar but functionally related processes are compared (Saier et al., 1995b). In Gram-negative enteric bacteria, an external sugar is sensed by the sugar-recognition constituent of an Enzyme II complex of the PTS (IIC), and a dephosphorylating signal is transmitted via the Enzyme IIB/HPr proteins to the central regulatory protein, IIAGlc. Targets regulated include (1) permeases specific for lactose, maltose, melibiose and raffinose, (2) catabolic enzymes such as glycerol kinase that generate cytoplasmic inducers, and (3) the cAMP biosynthetic enzyme, adenylate cyclase that mediates catabolite repression (Saier, 1989, 1993). In low-GC Gram-positive bacteria, cytoplasmic phosphorylated sugar metabolites are sensed by the HPr kinase which is allostericlaly activated. HPr becomes phosphorylated on Ser-46, and this phosphorylated derivative regulates the activities of its target proteins. These targets include (1) the PTS, (2) non-PTS permeases (both of which are inhibited) and (3) a cytoplasmic sugar-P phosphatase which is activated to reduce cytoplasmic inducer levels. Other important targets of HPr(ser-P) action are (4) the CcpA protein and probably (5) the CepB transcription factor. These two proteins together are believed to determine the intensity of catabolite repression. Their relative importance depends on physiological conditions. Both proteins may respond to the cytoplasmic concentration of HPr(ser-P) and appropriate metabolites. CepA possibly binds

  1. Transcriptional repression in normal human keratinocytes by wild-type and mutant p53.

    PubMed

    Alvarez-Salas, L M; Velazquez, A; Lopez-Bayghen, E; Woodworth, C D; Garrido, E; Gariglio, P; DiPaolo, J A

    1995-05-01

    Wild-type p53 is a nuclear phosphoprotein that inhibits cell proliferation and represses transcriptionally most TATA box-containing promoters in transformed or tumor-derived cell lines. This study demonstrates that p53 alters transcription of the long control region (LCR) of human papillomavirus type 18 (HPV-18). Wild-type and mutant p53 143Val to Ala repressed the HPV-18 LCR promoter in normal human keratinocytes, the natural host cell for HPV infections. Repression by wild-type p53 was also observed in C-33A cells and in an HPV-16-immortalized cell line with an inducible wild-type p53. However, when C-33A cells were cotransfected with the HPV-18 LCR and mutant 143Val to Ala, repression did not occur. Mutant p53 135Cys to Ser did not induce repression in either normal human keratinocytes or in the C-33A line; although like 143Val to Ala, it is thought to affect the DNA binding activity of the wild-type protein. The ability of mutant p53 143Val to Ala to inactivate the HPV early promoter in normal cells (by approximately 60% reduction) suggests that this mutant may be able to associate with wild-type p53 and interact with TATA box-binding proteins. Therefore, these results demonstrate that the transcriptional activities of p53 mutants may be dependent upon the cell type assayed and the form of its endogenous p53. Furthermore, normal human keratinocytes represent an alternative model for determining the activities of p53 mutants.

  2. Plant callus: mechanisms of induction and repression.

    PubMed

    Ikeuchi, Momoko; Sugimoto, Keiko; Iwase, Akira

    2013-09-01

    Plants develop unorganized cell masses like callus and tumors in response to various biotic and abiotic stimuli. Since the historical discovery that the combination of two growth-promoting hormones, auxin and cytokinin, induces callus from plant explants in vitro, this experimental system has been used extensively in both basic research and horticultural applications. The molecular basis of callus formation has long been obscure, but we are finally beginning to understand how unscheduled cell proliferation is suppressed during normal plant development and how genetic and environmental cues override these repressions to induce callus formation. In this review, we will first provide a brief overview of callus development in nature and in vitro and then describe our current knowledge of genetic and epigenetic mechanisms underlying callus formation. PMID:24076977

  3. Hypnotizability as a Function of Repression, Adaptive Regression, and Mood

    ERIC Educational Resources Information Center

    Silver, Maurice Joseph

    1974-01-01

    Forty male undergraduates were assessed in a personality assessment session and a hypnosis session. The personality traits studied were repressive style and adaptive regression, while the transitory variable was mood prior to hypnosis. Hypnotizability was a significant interactive function of repressive style and mood, but not of adaptive…

  4. Dream Recall And Repression: Evidence For An Alternative Hypothesis

    ERIC Educational Resources Information Center

    Cohen, David B.; Wolfe, Gary

    1973-01-01

    An "Inner-rejectant" life style committed to repressing dreams has been described in terms of external locus of control, field dependence, and "poor inner life." However, in empirical studies reported here, results do not provide strong support for the (repression) formulation. The results suggest a distinction between life-style variables related…

  5. Multiple Poliovirus Proteins Repress Cytoplasmic RNA Granules

    PubMed Central

    Dougherty, Jonathan D.; Tsai, Wei-Chih; Lloyd, Richard E.

    2015-01-01

    We have previously shown that poliovirus (PV) infection induces stress granule (SG) formation early in infection and then inhibits the formation of SG and disperses processing bodies (PBs) by the mid-phase of infection. Loss of SG was linked to cleavage of G3BP1 by viral 3C proteinase (3Cpro), however dispersal of PBs was not strongly linked to cleavage of specific factors by viral proteinases, suggesting other viral proteins may play roles in inhibition of SG or PB formation. Here we have screened all viral proteins for roles in inducing or inhibiting the formation of RNA granules by creating fusions with mCherry and expressing them individually in cells. Expression of viral proteins separately revealed that the capsid region P1, 2Apro, 3A, 3Cpro, the protease precursor 3CD and 3D polymerase all affect RNA granules to varying extents, whereas 2BC does not. 2Apro, which cleaves eIF4GI, induced SGs as expected, and entered novel foci containing the SG nucleating protein G3BP1. Of the two forms of G3BP, only G3BP1 is cleaved by a virus proteinase, 3Cpro, whereas G3BP2 is not cleaved by 3Cpro or 2Apro. Surprisingly, 3CD, which contains proteinase activity, differentially repressed PBs but not SGs. Further, both 2Apro and 3Cpro expression dispersed PBs, however molecular targets were different since PB dispersal due to 2Apro and heat shock protein (Hsp)90 inhibition but not 3Cpro, could be rescued by application of oxidative stress to cells. The data indicate that PV repression of SGs and PBs is multifactorial, though protease function is dominant. PMID:26610553

  6. Huntingtin facilitates polycomb repressive complex 2

    PubMed Central

    Seong, Ihn Sik; Woda, Juliana M.; Song, Ji-Joon; Lloret, Alejandro; Abeyrathne, Priyanka D.; Woo, Caroline J.; Gregory, Gillian; Lee, Jong-Min; Wheeler, Vanessa C.; Walz, Thomas; Kingston, Robert E.; Gusella, James F.; Conlon, Ronald A.; MacDonald, Marcy E.

    2010-01-01

    Huntington's disease (HD) is caused by expansion of the polymorphic polyglutamine segment in the huntingtin protein. Full-length huntingtin is thought to be a predominant HEAT repeat α-solenoid, implying a role as a facilitator of macromolecular complexes. Here we have investigated huntingtin's domain structure and potential intersection with epigenetic silencer polycomb repressive complex 2 (PRC2), suggested by shared embryonic deficiency phenotypes. Analysis of a set of full-length recombinant huntingtins, with different polyglutamine regions, demonstrated dramatic conformational flexibility, with an accessible hinge separating two large α-helical domains. Moreover, embryos lacking huntingtin exhibited impaired PRC2 regulation of Hox gene expression, trophoblast giant cell differentiation, paternal X chromosome inactivation and histone H3K27 tri-methylation, while full-length endogenous nuclear huntingtin in wild-type embryoid bodies (EBs) was associated with PRC2 subunits and was detected with trimethylated histone H3K27 at Hoxb9. Supporting a direct stimulatory role, full-length recombinant huntingtin significantly increased the histone H3K27 tri-methylase activity of reconstituted PRC2 in vitro, and structure–function analysis demonstrated that the polyglutamine region augmented full-length huntingtin PRC2 stimulation, both in HdhQ111 EBs and in vitro, with reconstituted PRC2. Knowledge of full-length huntingtin's α-helical organization and role as a facilitator of the multi-subunit PRC2 complex provides a novel starting point for studying PRC2 regulation, implicates this chromatin repressive complex in a neurodegenerative disorder and sets the stage for further study of huntingtin's molecular function and the impact of its modulatory polyglutamine region. PMID:19933700

  7. Polycomb repressive complex 1 controls uterine decidualization

    PubMed Central

    Bian, Fenghua; Gao, Fei; Kartashov, Andrey V.; Jegga, Anil G.; Barski, Artem; Das, Sanjoy K.

    2016-01-01

    Uterine stromal cell decidualization is an essential part of the reproductive process. Decidual tissue development requires a highly regulated control of the extracellular tissue remodeling; however the mechanism of this regulation remains unknown. Through systematic expression studies, we detected that Cbx4/2, Rybp, and Ring1B [components of polycomb repressive complex 1 (PRC1)] are predominantly utilized in antimesometrial decidualization with polyploidy. Immunofluorescence analyses revealed that PRC1 members are co-localized with its functional histone modifier H2AK119ub1 (mono ubiquitination of histone-H2A at lysine-119) in polyploid cell. A potent small-molecule inhibitor of Ring1A/B E3-ubiquitin ligase or siRNA-mediated suppression of Cbx4 caused inhibition of H2AK119ub1, in conjunction with perturbation of decidualization and polyploidy development, suggesting a role for Cbx4/Ring1B-containing PRC1 in these processes. Analyses of genetic signatures by RNA-seq studies showed that the inhibition of PRC1 function affects 238 genes (154 up and 84 down) during decidualization. Functional enrichment analyses identified that about 38% genes primarily involved in extracellular processes are specifically targeted by PRC1. Furthermore, ~15% of upregulated genes exhibited a significant overlap with the upregulated Bmp2 null-induced genes in mice. Overall, Cbx4/Ring1B-containing PRC1 controls decidualization via regulation of extracellular gene remodeling functions and sheds new insights into underlying molecular mechanism(s) through transcriptional repression regulation. PMID:27181215

  8. p53-dependent gene repression through p21 is mediated by recruitment of E2F4 repression complexes.

    PubMed

    Benson, E K; Mungamuri, S K; Attie, O; Kracikova, M; Sachidanandam, R; Manfredi, J J; Aaronson, S A

    2014-07-24

    The p53 tumor suppressor protein is a major sensor of cellular stresses, and upon stabilization, activates or represses many genes that control cell fate decisions. While the mechanism of p53-mediated transactivation is well established, several mechanisms have been proposed for p53-mediated repression. Here, we demonstrate that the cyclin-dependent kinase inhibitor p21 is both necessary and sufficient for the downregulation of known p53-repression targets, including survivin, CDC25C, and CDC25B in response to p53 induction. These same targets are similarly repressed in response to p16 overexpression, implicating the involvement of the shared downstream retinoblastoma (RB)-E2F pathway. We further show that in response to either p53 or p21 induction, E2F4 complexes are specifically recruited onto the promoters of these p53-repression targets. Moreover, abrogation of E2F4 recruitment via the inactivation of RB pocket proteins, but not by RB loss of function alone, prevents the repression of these genes. Finally, our results indicate that E2F4 promoter occupancy is globally associated with p53-repression targets, but not with p53 activation targets, implicating E2F4 complexes as effectors of p21-dependent p53-mediated repression.

  9. Secularization versus religious revival in Eastern Europe: Church institutional resilience, state repression and divergent paths.

    PubMed

    Northmore-Ball, Ksenia; Evans, Geoffrey

    2016-05-01

    Despite continuing for over two decades, the debate about the nature of the trends in religiosity in post-Communist Eastern Europe remains unresolved: some arguing that these countries are undergoing the same process of secularization as the West, while others insist that the entire region is experiencing a religious revival. Using national sample surveys from the early 1990s to 2007 to examine the change in demographic predictors of religiosity, we show that Catholic and Orthodox countries are experiencing different trends, the first group displaying evidence of secularization and the second of revival, and that these two different trends are likely to derive from the legacies of state repression and the differing abilities of the churches to resist such repression. We argue that the current literature has thus taken a mistakenly general approach, and that the post-Communist region consists of at least two distinct groups of societies with different trends in religiosity. PMID:26973030

  10. MafG Sumoylation Is Required for Active Transcriptional Repression

    PubMed Central

    Motohashi, Hozumi; Katsuoka, Fumiki; Miyoshi, Chika; Uchimura, Yasuhiro; Saitoh, Hisato; Francastel, Claire; Engel, James Douglas; Yamamoto, Masayuki

    2006-01-01

    A straightforward mechanism for eliciting transcriptional repression would be to simply block the DNA binding site for activators. Such passive repression is often mediated by transcription factors that lack an intrinsic repressor activity. MafG is a bidirectional regulator of transcription, a repressor in its homodimeric state but an activator when heterodimerized with p45. Here, we report that MafG is conjugated to SUMO-2/3 in vivo. To clarify the possible physiological role(s) for sumoylation in regulating MafG activity, we evaluated mutant and wild-type MafG in transgenic mice and cultured cells. Whereas sumoylation-deficient MafG activated p45-dependent transcription normally and did not affect heterodimer activity, repression by the sumoylation-deficient MafG mutant was severely compromised in vivo. Furthermore, the SUMO-dependent repression activity of MafG was sensitive to histone deacetylase inhibition. Thus, repression by MafG is not achieved through simple passive repression by competing for the activator binding site but requires sumoylation, which then mediates transcriptional repression through recruitment of a repressor complex containing histone deacetylase activity. PMID:16738329

  11. Osterix represses adipogenesis by negatively regulating PPARγ transcriptional activity

    PubMed Central

    Han, Younho; Kim, Chae Yul; Cheong, Heesun; Lee, Kwang Youl

    2016-01-01

    Osterix is a novel bone-related transcription factor involved in osteoblast differentiation, and bone maturation. Because a reciprocal relationship exists between adipocyte and osteoblast differentiation of bone marrow derived mesenchymal stem cells, we hypothesized that Osterix might have a role in adipogenesis. Ablation of Osterix enhanced adipogenesis in 3T3-L1 cells, whereas overexpression suppressed this process and inhibited the expression of adipogenic markers including CCAAT/enhancer-binding protein alpha (C/EBPα) and peroxisome proliferator-activated receptor gamma (PPARγ). Further studies indicated that Osterix significantly decreased PPARγ-induced transcriptional activity. Using co-immunoprecipitation and GST-pull down analysis, we found that Osterix directly interacts with PPARγ. The ligand-binding domain (LBD) of PPARγ was responsible for this interaction, which was followed by repression of PPARγ-induced transcriptional activity, even in the presence of rosiglitazone. Taken together, we identified the Osterix has an important regulatory role on PPARγ activity, which contributed to the mechanism of adipogenesis. PMID:27752121

  12. Repressed mRNAs of muscle cells

    SciTech Connect

    Bag, J.; Pramanik, S.

    1986-05-01

    In rat L-6 muscle cells cytoplasmic mRNAs have been found in two compartments polysome bound and free (or non polysomal). The mRNAs were differentially distributed in these two compartments. The mRNA for a polypeptide of molecular weight 60,000 daltons was present predominantly in the free or non polysomal fraction. We have prepared a cDNA library from the non polysomal mRNAs of L-6 myoblasts. This library was screened by using /sup 32/P labeled cDNA prepared from both polysomal and non polysomal mRNAs. We were able to isolate ten colonies which produced strong signals only when /sup 32/P cDNA from non polysomal mRNAs were used. The DNA from two of these colonies hybridized to two different mRNAs. These two clones were used to quantitate the mRNAs in polysomal and non polysomal fractions. It was found that one clone (D-12) hybridized to a mRNA 60% of which was present in the non polysomal fraction. On the other hand a second clone (P-5) hybridized to a mRNA 80% of which was repressed (non polysomal). Further studies are in progress to examine the mechanism of translational block of these two mRNAs.

  13. Salmonella promotes virulence by repressing cellulose production.

    PubMed

    Pontes, Mauricio H; Lee, Eun-Jin; Choi, Jeongjoon; Groisman, Eduardo A

    2015-04-21

    Cellulose is the most abundant organic polymer on Earth. In bacteria, cellulose confers protection against environmental insults and is a constituent of biofilms typically formed on abiotic surfaces. We report that, surprisingly, Salmonella enterica serovar Typhimurium makes cellulose when inside macrophages. We determine that preventing cellulose synthesis increases virulence, whereas stimulation of cellulose synthesis inside macrophages decreases virulence. An attenuated mutant lacking the mgtC gene exhibited increased cellulose levels due to increased expression of the cellulose synthase gene bcsA and of cyclic diguanylate, the allosteric activator of the BcsA protein. Inactivation of bcsA restored wild-type virulence to the Salmonella mgtC mutant, but not to other attenuated mutants displaying a wild-type phenotype regarding cellulose. Our findings indicate that a virulence determinant can promote pathogenicity by repressing a pathogen's antivirulence trait. Moreover, they suggest that controlling antivirulence traits increases long-term pathogen fitness by mediating a trade-off between acute virulence and transmission.

  14. Salmonella promotes virulence by repressing cellulose production

    PubMed Central

    Pontes, Mauricio H.; Lee, Eun-Jin; Choi, Jeongjoon; Groisman, Eduardo A.

    2015-01-01

    Cellulose is the most abundant organic polymer on Earth. In bacteria, cellulose confers protection against environmental insults and is a constituent of biofilms typically formed on abiotic surfaces. We report that, surprisingly, Salmonella enterica serovar Typhimurium makes cellulose when inside macrophages. We determine that preventing cellulose synthesis increases virulence, whereas stimulation of cellulose synthesis inside macrophages decreases virulence. An attenuated mutant lacking the mgtC gene exhibited increased cellulose levels due to increased expression of the cellulose synthase gene bcsA and of cyclic diguanylate, the allosteric activator of the BcsA protein. Inactivation of bcsA restored wild-type virulence to the Salmonella mgtC mutant, but not to other attenuated mutants displaying a wild-type phenotype regarding cellulose. Our findings indicate that a virulence determinant can promote pathogenicity by repressing a pathogen's antivirulence trait. Moreover, they suggest that controlling antivirulence traits increases long-term pathogen fitness by mediating a trade-off between acute virulence and transmission. PMID:25848006

  15. Salmonella promotes virulence by repressing cellulose production.

    PubMed

    Pontes, Mauricio H; Lee, Eun-Jin; Choi, Jeongjoon; Groisman, Eduardo A

    2015-04-21

    Cellulose is the most abundant organic polymer on Earth. In bacteria, cellulose confers protection against environmental insults and is a constituent of biofilms typically formed on abiotic surfaces. We report that, surprisingly, Salmonella enterica serovar Typhimurium makes cellulose when inside macrophages. We determine that preventing cellulose synthesis increases virulence, whereas stimulation of cellulose synthesis inside macrophages decreases virulence. An attenuated mutant lacking the mgtC gene exhibited increased cellulose levels due to increased expression of the cellulose synthase gene bcsA and of cyclic diguanylate, the allosteric activator of the BcsA protein. Inactivation of bcsA restored wild-type virulence to the Salmonella mgtC mutant, but not to other attenuated mutants displaying a wild-type phenotype regarding cellulose. Our findings indicate that a virulence determinant can promote pathogenicity by repressing a pathogen's antivirulence trait. Moreover, they suggest that controlling antivirulence traits increases long-term pathogen fitness by mediating a trade-off between acute virulence and transmission. PMID:25848006

  16. Repression of the Drosophila proliferating-cell nuclear antigen gene promoter by zerknuellt protein

    SciTech Connect

    Yamaguchi, Masamitsu; Hirose, Fumiko; Nishida, Yasuyoshi; Matsukage, Akio )

    1991-10-01

    A 631-bp fragment containing the 5{prime}-flanking region of the Drosophila melanogaster proliferating-cell nuclear antigen (PCNA) gene was placed upstream of the chloramphenicol acetyltransferase (CAT) gene of a CAT vector. A transient expression assay of CAT activity in Drosophila Kc cells transfected with this plasmid and a set of 5{prime}-deletion derivatives revealed that the promoter function resided within a 192-bp region. Cotransfection with a zerknuellt (zen)-expressing plasmid specifically repressed CAT expression. However, cotransfection with expression plasmids for a nonfunctional zen mutation, even skipped, or bicoid showed no significant effect on CAT expression. RNase protection analysis revealed that the repression by zen was at the transcription step. The target sequence of zen was mapped within the 34-bp region of the PCNA gene promoter, even though it lacked zen protein-binding sites. Transgenic flies carrying the PCNA gene regulatory region fused with lacZ were established. These results indicate that zen indirectly represses PCNA gene expression, probably by regulating the expression of some transcription factor(s) that binds to the PCNA gene promoter.

  17. Pyrimidine biosynthetic enzymes of Salmonella typhimurium, repressed specifically by growth in the presence of cytidine.

    PubMed Central

    Kelln, R A; Kinahan, J J; Foltermann, K F; O'Donovan, G A

    1975-01-01

    The repressive effects of exogenous cytidine on growing cells was examined in a specially constructed strain in which the pool sizes of endogenous uridine 5'-diphosphate and uridine 5'-triphosphate cannot be varied by the addition of uracil and/or uridine to the medium. Five enzymes of the pyrimidine biosynthetic pathway and one enzyme of the arginine biosynthetic pathway were assayed from cells grown under a variety of conditions. Cytidine repressed the synthesis of dihydroorotase (encoded by pyrC), dihydroorotate dehydrogenase (encoded by pyrD), and ornithine transcarbamylase (encoded by argI). Moreover, aspartate transcarbamylase (encoded by pyrB) became further derepressed upon cytidine addition, whereas no change occurred in the levels of the last two enzymes (encoded by pyrE and pyrF) of the pyrimidine pathway. Quantitative nucleotide pool determinations have provided evidence that any individual ribo- or deoxyribonucleoside mono-, di-, or triphosphate of cytosine or uracil is not a repressing metabolite for the pyrimidine biosynthetic enzymes. Other nucleotide derivatives or ratios must be considered. PMID:1102530

  18. Multiple repressive mechanisms in the hippocampus during memory formation.

    PubMed

    Cho, Jun; Yu, Nam-Kyung; Choi, Jun-Hyeok; Sim, Su-Eon; Kang, SukJae Joshua; Kwak, Chuljung; Lee, Seung-Woo; Kim, Ji-il; Choi, Dong Il; Kim, V Narry; Kaang, Bong-Kiun

    2015-10-01

    Memory stabilization after learning requires translational and transcriptional regulations in the brain, yet the temporal molecular changes that occur after learning have not been explored at the genomic scale. We used ribosome profiling and RNA sequencing to quantify the translational status and transcript levels in the mouse hippocampus after contextual fear conditioning. We revealed three types of repressive regulations: translational suppression of ribosomal protein-coding genes in the hippocampus, learning-induced early translational repression of specific genes, and late persistent suppression of a subset of genes via inhibition of estrogen receptor 1 (ESR1/ERα) signaling. In behavioral analyses, overexpressing Nrsn1, one of the newly identified genes undergoing rapid translational repression, or activating ESR1 in the hippocampus impaired memory formation. Collectively, this study unveils the yet-unappreciated importance of gene repression mechanisms for memory formation.

  19. Targeted Transcriptional Repression in Bacteria Using CRISPR Interference (CRISPRi).

    PubMed

    Hawkins, John S; Wong, Spencer; Peters, Jason M; Almeida, Ricardo; Qi, Lei S

    2015-01-01

    Clustered regularly interspersed short palindromic repeats (CRISPR) interference (CRISPRi) is a powerful technology for sequence-specifically repressing gene expression in bacterial cells. CRISPRi requires only a single protein and a custom-designed guide RNA for specific gene targeting. In Escherichia coli, CRISPRi repression efficiency is high (~300-fold), and there are no observable off-target effects. The method can be scaled up as a general strategy for the repression of many genes simultaneously using multiple designed guide RNAs. Here we provide a protocol for efficient guide RNA design, cloning, and assay of the CRISPRi system in E. coli. In principle, this protocol can be used to construct CRISPRi systems for gene repression in other species of bacteria.

  20. Organic acid mediated repression of sugar utilization in rhizobia.

    PubMed

    Iyer, Bhagya; Rajput, Mahendrapal Singh; Jog, Rahul; Joshi, Ekta; Bharwad, Krishna; Rajkumar, Shalini

    2016-11-01

    Rhizobia are a class of symbiotic diazotrophic bacteria which utilize C4 acids in preference to sugars and the sugar utilization is repressed as long as C4 acids are present. This can be manifested as a diauxie when rhizobia are grown in the presence of a sugar and a C4 acid together. Succinate, a C4 acid is known to repress utilization of sugars, sugar alcohols, hydrocarbons, etc by a mechanism termed as Succinate Mediated Catabolite Repression (SMCR). Mechanism of catabolite repression determines the hierarchy of carbon source utilization in bacteria. Though the mechanism of catabolite repression has been well studied in model organisms like E. coli, B. subtilis and Pseudomonas sp., mechanism of SMCR in rhizobia has not been well elucidated. C4 acid uptake is important for effective symbioses while mutation in the sugar transport and utilization genes does not affect symbioses. Deletion of hpr and sma0113 resulted in the partial relief of SMCR of utilization of galactosides like lactose, raffinose and maltose in the presence of succinate. However, no such regulators governing SMCR of glucoside utilization have been identified till date. Though rhizobia can utilize multitude of sugars, high affinity transporters for many sugars are yet to be identified. Identifying high affinity sugar transporters and studying the mechanism of catabolite repression in rhizobia is important to understand the level of regulation of SMCR and the key regulators involved in SMCR. PMID:27664739

  1. CRISPR Technology for Genome Activation and Repression in Mammalian Cells.

    PubMed

    Du, Dan; Qi, Lei S

    2016-01-01

    Targeted modulation of transcription is necessary for understanding complex gene networks and has great potential for medical and industrial applications. CRISPR is emerging as a powerful system for targeted genome activation and repression, in addition to its use in genome editing. This protocol describes how to design, construct, and experimentally validate the function of sequence-specific single guide RNAs (sgRNAs) for sequence-specific repression (CRISPRi) or activation (CRISPRa) of transcription in mammalian cells. In this technology, the CRISPR-associated protein Cas9 is catalytically deactivated (dCas9) to provide a general platform for RNA-guided DNA targeting of any locus in the genome. Fusion of dCas9 to effector domains with distinct regulatory functions enables stable and efficient transcriptional repression or activation in mammalian cells. Delivery of multiple sgRNAs further enables activation or repression of multiple genes. By using scaffold RNAs (scRNAs), different effectors can be recruited to different genes for simultaneous activation of some and repression of others. The CRISPRi and CRISPRa methods provide powerful tools for sequence-specific control of gene expression on a genome-wide scale to aid understanding gene functions and for engineering genetic regulatory systems. PMID:26729910

  2. Mechanism of promoter repression by Lac repressor-DNA loops.

    PubMed

    Becker, Nicole A; Peters, Justin P; Maher, L James; Lionberger, Troy A

    2013-01-01

    The Escherichia coli lactose (lac) operon encodes the first genetic switch to be discovered, and lac remains a paradigm for studying negative and positive control of gene expression. Negative control is believed to involve competition of RNA polymerase and Lac repressor for overlapping binding sites. Contributions to the local Lac repressor concentration come from free repressor and repressor delivered to the operator from remote auxiliary operators by DNA looping. Long-standing questions persist concerning the actual role of DNA looping in the mechanism of promoter repression. Here, we use experiments in living bacteria to resolve four of these questions. We show that the distance dependence of repression enhancement is comparable for upstream and downstream auxiliary operators, confirming the hypothesis that repressor concentration increase is the principal mechanism of repression loops. We find that as few as four turns of DNA can be constrained in a stable loop by Lac repressor. We show that RNA polymerase is not trapped at repressed promoters. Finally, we show that constraining a promoter in a tight DNA loop is sufficient for repression even when promoter and operator do not overlap. PMID:23143103

  3. Salt stress represses production of extracellular proteases in Bacillus pumilus.

    PubMed

    Liu, R F; Huang, C L; Feng, H

    2015-05-11

    Bacillus pumilus is able to secrete subtilisin-like prote-ases, one of which has been purified and characterized biochemically, demonstrating great potential for use in industrial applications. In the current study, the biosynthesis and transcription of extracellular pro-teases in B. pumilus (BA06) under salt stress were investigated using various methods, including a proteolytic assay, zymogram analysis, and real-time PCR. Our results showed that total extracellular proteolytic activity, both in fermentation broth and on milk-containing agar plates, was considerably repressed by salt in a dosage-dependent manner. As Bacillus species usually secret multiple extracellular proteases, a vari-ety of individual extracellular protease encoding genes were selected for real-time PCR analysis. It was shown that proteases encoded by the aprE and aprX genes were the major proteases in the fermentation broth in terms of their transcripts in B. pumilus. Further, transcription of aprE, aprX, and epr genes was indeed repressed by salt stress. In con-trast, transcription of other genes (e.g., vpr and wprA) was not repressed or significantly affected by the salt. Conclusively, salt stress represses total extracellular proteolytic activity in B. pumilus, which can largely be ascribed to suppression of the major protease-encoding genes (aprE, aprX) at the transcriptional level. In contrast, transcription of other pro-tease-encoding genes (e.g., vpr, wprA) was not repressed by salt stress.

  4. CRISPR Technology for Genome Activation and Repression in Mammalian Cells.

    PubMed

    Du, Dan; Qi, Lei S

    2016-01-04

    Targeted modulation of transcription is necessary for understanding complex gene networks and has great potential for medical and industrial applications. CRISPR is emerging as a powerful system for targeted genome activation and repression, in addition to its use in genome editing. This protocol describes how to design, construct, and experimentally validate the function of sequence-specific single guide RNAs (sgRNAs) for sequence-specific repression (CRISPRi) or activation (CRISPRa) of transcription in mammalian cells. In this technology, the CRISPR-associated protein Cas9 is catalytically deactivated (dCas9) to provide a general platform for RNA-guided DNA targeting of any locus in the genome. Fusion of dCas9 to effector domains with distinct regulatory functions enables stable and efficient transcriptional repression or activation in mammalian cells. Delivery of multiple sgRNAs further enables activation or repression of multiple genes. By using scaffold RNAs (scRNAs), different effectors can be recruited to different genes for simultaneous activation of some and repression of others. The CRISPRi and CRISPRa methods provide powerful tools for sequence-specific control of gene expression on a genome-wide scale to aid understanding gene functions and for engineering genetic regulatory systems.

  5. Nrf2-dependent repression of interleukin-12 expression in human dendritic cells exposed to inorganic arsenic.

    PubMed

    Macoch, Mélinda; Morzadec, Claudie; Génard, Romain; Pallardy, Marc; Kerdine-Römer, Saadia; Fardel, Olivier; Vernhet, Laurent

    2015-11-01

    Inorganic arsenic, a well-known Nrf2 inducer, exerts immunosuppressive properties. In this context, we recently reported that the differentiation of human blood monocytes into immature dendritic cells (DCs), in the presence of low and noncytotoxic concentrations of arsenic, represses the ability of DCs to release key cytokines in response to different stimulating agents. Particularly, arsenic inhibits the expression of human interleukin-12 (IL-12, also named IL-12p70), a major proinflammatory cytokine that controls the differentiation of Th1 lymphocytes. In the present study, we determined if Nrf2 could contribute to these arsenic immunotoxic effects. To this goal, human monocyte-derived DCs were first differentiated in the absence of metalloid and then pretreated with arsenic just before DC stimulation with lipopolysaccharide (LPS). Under these experimental conditions, arsenic rapidly and stably activates Nrf2 and increases the expression of Nrf2 target genes. It also significantly inhibits IL-12 expression in activated DCs, at both mRNA and protein levels. Particularly, arsenic reduces mRNA levels of IL12A and IL12B genes which encodes the p35 and p40 subunits of IL-12p70, respectively. tert-Butylhydroquinone (tBHQ), a reference Nrf2 inducer, mimics arsenic effects and potently inhibits IL-12 expression. Genetic inhibition of Nrf2 expression markedly prevents the repression of both IL12 mRNA and IL-12 protein levels triggered by arsenic and tBHQ in human LPS-stimulated DCs. In addition, arsenic significantly reduces IL-12 mRNA levels in LPS-activated bone marrow-derived DCs from Nrf2+/+ mice but not in DCs from Nrf2-/- mice. Finally, we show that, besides IL-12, arsenic significantly reduces the expression of IL-23, another heterodimer containing the p40 subunit. In conclusion, our study demonstrated that arsenic represses IL-12 expression in human-activated DCs by specifically stimulating Nrf2 activity.

  6. Leishmanicidal Activities of Novel Synthetic Furoxan and Benzofuroxan Derivatives

    PubMed Central

    Dutra, Luiz Antônio; de Almeida, Letícia; Passalacqua, Thais G.; Reis, Juliana Santana; Torres, Fabio A. E.; Martinez, Isabel; Peccinini, Rosangela Gonçalves; Chin, Chung Man; Chegaev, Konstantin; Guglielmo, Stefano; Fruttero, Roberta

    2014-01-01

    A novel series of furoxan (1,2,5-oxadiazole 2-oxide) (compounds 3, 4a and -b, 13a and -b, and 14a to -f) and benzofuroxan (benzo[c][1,2,5]oxadiazole 1-oxide) (compounds 7 and 8a to -c) derivatives were synthesized, characterized, and evaluated for in vitro activity against promastigote and intracellular amastigote forms of Leishmania amazonensis. The furoxan derivatives exhibited the ability to generate nitric oxide at different levels (7.8% to 27.4%). The benzofuroxan derivative 8a was able to increase nitrite production in medium supernatant from murine macrophages infected with L. amazonensis at 0.75 mM after 48 h. Furoxan and benzofuroxan derivatives showed remarkable leishmanicidal activity against both promastigote and intracellular amastigote forms. Compounds 8a, 14a and -b, and 14d exerted selective leishmanicidal activities superior to those of amphotericin B and pentamidine. In vitro studies at pH 5.4 reveal that compound 8a is stable until 8 h and that compound 14a behaves as a prodrug, releasing the active aldehyde 13a. These compounds have emerged as promising novel drug candidates for the treatment of leishmaniasis. PMID:24913171

  7. Polycomb repressive complex 2 in embryonic stem cells: an overview.

    PubMed

    Jones, Amanda; Wang, Hengbin

    2010-12-01

    Polycomb Group Proteins (PcG) are a family of epigenetic regulators responsible for the repression of an array of genes important in development and cell fate specification. PcG proteins complex to form two types of epigenetic regulators: Polycomb Repressive Complex 1 and 2 (PRC1 and PRC2). Although the mechanisms regulating PRC2 recruitment and activity in mammals remain poorly understood, recent work has identified a non-canonical PRC2 in mouse embryonic stem cells (mESC) with unique activities required for repression of PRC2 target genes and necessary for mESC differentiation and somatic cell reprogramming. Here we review the functions of PRC2 in embryonic stem cells and explore the role of the newly identified mESC specific PRC2 regulatory subunits Jarid2 (jumonji, AT rich interactive domain 2), Mtf2 (metal response element binding transcription factor 2) and esPRC2p48.

  8. The interaction of induction and repression mechanisms in the regulation of galacturonic acid-induced genes in Aspergillus niger.

    PubMed

    Niu, Jing; Homan, Tim G; Arentshorst, Mark; de Vries, Ronald P; Visser, Jaap; Ram, Arthur F J

    2015-09-01

    catabolite repression for most promoters. Interestingly, the pgxC promoter was still repressed by glucose even in the creA null background, suggesting a role for alternative repression mechanisms. Finally, we showed that low concentrations of GA are required to induce gene expression of pgaX, pgxB, and pgxC even under derepressing conditions. The results obtained are consistent with a model in which a GA-specific transcription factor is activated by GA or a GA-derivative, which binds to the conserved motif, possibly in combination with the HAP-complex, to drive GA-specific gene expression.

  9. miRNA-Dependent Translational Repression in the Drosophila Ovary

    PubMed Central

    Reich, John; Snee, Mark J.; Macdonald, Paul M.

    2009-01-01

    Background The Drosophila ovary is a tissue rich in post-transcriptional regulation of gene expression. Many of the regulatory factors are proteins identified via genetic screens. The more recent discovery of microRNAs, which in other animals and tissues appear to regulate translation of a large fraction of all mRNAs, raised the possibility that they too might act during oogenesis. However, there has been no direct demonstration of microRNA-dependent translational repression in the ovary. Methodology/Principal Findings Here, quantitative analyses of transcript and protein levels of transgenes with or without synthetic miR-312 binding sites show that the binding sites do confer translational repression. This effect is dependent on the ability of the cells to produce microRNAs. By comparison with microRNA-dependent translational repression in other cell types, the regulated mRNAs and the protein factors that mediate repression were expected to be enriched in sponge bodies, subcellular structures with extensive similarities to the P bodies found in other cells. However, no such enrichment was observed. Conclusions/Significance Our results reveal the variety of post-transcriptional regulatory mechanisms that operate in the Drosophila ovary, and have implications for the mechanisms of miRNA-dependent translational control used in the ovary. PMID:19252745

  10. Intellectual Performance as a Function of Repression and Menstrual Cycle.

    ERIC Educational Resources Information Center

    Englander-Golden, Paula; And Others

    Performance on complex (Space Relations and Verbal Reasoning) and simple (Digit Symbol) tests was investigated as a function of Byrne's Repression-Sensitization (RS) dimension, phase of menstrual cycle and premenstrual-menstrual (PM) symptomatology in a group of females not taking oral contraceptives. Two control groups, consisting of males and…

  11. Catabolite repression control of flagellum production by Serratia marcescens

    PubMed Central

    Stella, Nicholas A.; Kalivoda, Eric J.; O’Dee, Dawn M.; Nau, Gerard J.; Shanks, Robert M. Q.

    2008-01-01

    Serratia marcescens is an emerging opportunistic pathogen with a remarkably broad host range. The cAMP-regulated catabolite repression system of S. marcescens has recently been identified and demonstrated to regulate biofilm formation through the production of surface adhesions. Here we report that mutations in components of the catabolite repression system (cyaA and crp) eliminate flagellum production and swimming motility. Exogenous cAMP was able to restore flagellum production to adenylate cyclase mutants, as determined by transmission electron microscopy and PAGE analysis. A transposon-generated suppressor mutation of the crp motility defect mapped to upstream of the flhDC operon. This suppressor mutation resulted in an upregulation of flhD expression and flagellum production, indicating that flhDC expression is sufficient to restore flagellum production to crp mutants. Lastly, and contrary to a previous report, we found that flhD expression is controlled by the catabolite repression system using quantitative RT-PCR. Together, these data indicate that flagellum production is regulated by the cAMP-dependent catabolite repression system. Given the role of flagella in bacterial pathogenicity, the regulatory pathway described here may assist us in better understanding the putative role of motility in dissemination and virulence of this opportunistic pathogen. PMID:18718529

  12. MicroRNA-mediated repression of nonsense mRNAs

    PubMed Central

    Zhao, Ya; Lin, Jimin; Xu, Beiying; Hu, Sida; Zhang, Xue; Wu, Ligang

    2014-01-01

    Numerous studies have established important roles for microRNAs (miRNAs) in regulating gene expression. Here, we report that miRNAs also serve as a surveillance system to repress the expression of nonsense mRNAs that may produce harmful truncated proteins. Upon recognition of the premature termination codon by the translating ribosome, the downstream portion of the coding region of an mRNA is redefined as part of the 3′ untranslated region; as a result, the miRNA-responsive elements embedded in this region can be detected by miRNAs, triggering accelerated mRNA deadenylation and translational inhibition. We demonstrate that naturally occurring cancer-causing APC (adenomatous polyposis coli) nonsense mutants which escape nonsense-mediated mRNA decay (NMD) are repressed by miRNA-mediated surveillance. In addition, we show that miRNA-mediated surveillance and exon–exon junction complex-mediated NMD are not mutually exclusive and act additively to enhance the repressive activity. Therefore, we have uncovered a new role for miRNAs in repressing nonsense mutant mRNAs. DOI: http://dx.doi.org/10.7554/eLife.03032.001 PMID:25107276

  13. Impact of expert testimony on the believability of repressed memories.

    PubMed

    Sugarman, D B; Boney-McCoy, S

    1997-01-01

    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. PMID:9403982

  14. Functional repression of cAMP response element in 6-hydroxydopamine-treated neuronal cells.

    PubMed

    Chalovich, Elisabeth M; Zhu, Jian-hui; Caltagarone, John; Bowser, Robert; Chu, Charleen T

    2006-06-30

    Impaired survival signaling may represent a central mechanism in neurodegeneration. 6-Hydroxydopamine (6-OHDA) is an oxidative neurotoxin used to injure catecholaminergic cells of the central and peripheral nervous systems. Although 6-OHDA elicits phosphorylation of several kinases, downstream transcriptional effects that influence neuronal cell death are less defined. The cAMP response element (CRE) is present in the promoter sequences of several important neuronal survival factors. Treatment of catecholaminergic neuronal cell lines (B65 and SH-SY5Y) with 6-OHDA resulted in repression of basal CRE transactivation. Message levels of CRE-driven genes such as brain-derived neurotrophic factor and the survival factor Bcl-2 were decreased in 6-OHDA-treated cells, but message levels of genes lacking CRE sequences were not affected. Repression of CRE could be reversed by delayed treatment with cAMP several hours after initiation of 6-OHDA injury. Furthermore, restoration of CRE-driven transcription was associated with significant neuroprotection. In contrast to observations in other model systems, the mechanism of CRE repression did not involve decreased phosphorylation of its binding protein CREB. Instead, total CREB and phospho-CREB (pCREB) were increased in the cytoplasm and decreased in the nucleus of 6-OHDA-treated cells. 6-OHDA also decreased nuclear pCREB in dopaminergic neurons of primary mouse midbrain cultures. Co-treatment with cAMP promoted/restored nuclear localization of pCREB in both immortalized and primary culture systems. Increased cytoplasmic pCREB was observed in degenerating human Parkinson/Lewy body disease substantia nigra neurons but not in age-matched controls. Notably, cytoplasmic accumulation of activated upstream CREB kinases has been observed previously in both 6-OHDA-treated cells and degenerating human neurons, supporting a potential role for impaired nuclear import of phosphorylated signaling proteins.

  15. A vir-repressed gene of Bordetella pertussis is required for virulence.

    PubMed Central

    Beattie, D T; Shahin, R; Mekalanos, J J

    1992-01-01

    Coordinate regulation of gene expression in Bordetella pertussis is controlled by the products of the vir locus, BvgA and BvgS. In the presence of modulating signals such as MgSO4 and nicotinic acid, expression of vir-activated genes (vag) is reduced, while expression of vir-repressed genes (vrg) is maximal. We have cloned one of these vir-repressed genes, vrg-6, in Escherichia coli. DNA sequencing has shown that vrg-6 is contained on a single EcoRI restriction endonuclease fragment and is predicted to code for a protein of 105 amino acids with a molecular weight of 11,441. The predicted protein product appears to have two domains, one consisting of seven hydrophobic proline-rich pentameric repeats and the other consisting of five alkaline trimeric repeats. Southern blot analysis has revealed vrg-6-homologous sequences in the chromosomes of Bordetella bronchiseptica and Bordetella parapertussis, but, unlike Bordetella pertussis, these species do not express vrg-6-homologous RNA when grown under modulating conditions. In order to assess the role of vrg gene products in B. pertussis pathogenesis, two 18323 derivatives which harbor TnphoA insertions in vrg genes were analyzed in a mouse model of respiratory infection. Strain SK6, which carries a vrg-6::TnphoA mutation, failed to induce lymphocytosis and was significantly less able to colonize lungs and trachea than its parent strain 18323 or than SK18, which harbors a TnphoA fusion in the vrg-18 locus. This is the first evidence that a vir-repressed gene may play an important role in the virulence of B. pertussis and the pathogenesis of whooping cough. Images PMID:1730491

  16. Ligand-dependent repression of the erythroid transcription factor GATA-1 by the estrogen receptor.

    PubMed Central

    Blobel, G A; Sieff, C A; Orkin, S H

    1995-01-01

    High-dose estrogen administration induces anemia in mammals. In chickens, estrogens stimulate outgrowth of bone marrow-derived erythroid progenitor cells and delay their maturation. This delay is associated with down-regulation of many erythroid cell-specific genes, including alpha- and beta-globin, band 3, band 4.1, and the erythroid cell-specific histone H5. We show here that estrogens also reduce the number of erythroid progenitor cells in primary human bone marrow cultures. To address potential mechanisms by which estrogens suppress erythropoiesis, we have examined their effects on GATA-1, an erythroid transcription factor that participates in the regulation of the majority of erythroid cell-specific genes and is necessary for full maturation of erythrocytes. We demonstrate that the transcriptional activity of GATA-1 is strongly repressed by the estrogen receptor (ER) in a ligand-dependent manner and that this repression is reversible in the presence of 4-hydroxytamoxifen. ER-mediated repression of GATA-1 activity occurs on an artificial promoter containing a single GATA-binding site, as well as in the context of an intact promoter which is normally regulated by GATA-1. GATA-1 and ER bind to each other in vitro in the absence of DNA. In coimmunoprecipitation experiments using transfected COS cells, GATA-1 and ER associate in a ligand-dependent manner. Mapping experiments indicate that GATA-1 and the ER form at least two contacts, which involve the finger region and the N-terminal activation domain of GATA-1. We speculate that estrogens exert effects on erythropoiesis by modulating GATA-1 activity through protein-protein interaction with the ER. Interference with GATA-binding proteins may be one mechanism by which steroid hormones modulate cellular differentiation. PMID:7760810

  17. Unintended Consequences of Repression: Alliance Formation in South Korea's Democracy Movement (1970-1979)

    ERIC Educational Resources Information Center

    Chang, Paul Y.

    2008-01-01

    Research regarding the impact of repression on social movements has yielded conflicting findings; some argue that repression decreases the total quantity of protest events while others argue that it motivates protest. To move beyond this impasse, various scholars have suggested exploring how repression influences the quality of social movements.…

  18. EBV reactivation as a target of luteolin to repress NPC tumorigenesis

    PubMed Central

    Wu, Chung-Chun; Fang, Chih-Yeu; Hsu, Hui-Yu; Chuang, Hsin-Ying; Cheng, Yu-Jhen; Chen, Yen-Ju; Chou, Sheng-Ping; Huang, Sheng-Yen; Lin, Su-Fang; Chang, Yao; Tsai, Ching-Hwa; Chen, Jen-Yang

    2016-01-01

    Nasopharyngeal carcinoma (NPC) is a malignancy derived from the epithelial cells of the nasopharynx. Although a combination of radiotherapy with chemotherapy is effective for therapy, relapse and metastasis after remission remain major causes of mortality. Epstein-Barr virus (EBV) is believed to be one of causes of NPC development. We demonstrated previously that EBV reactivation is important for the carcinogenesis of NPC. We sought, therefore, to determine whether EBV reactivation can be a target for retardation of relapse of NPC. After screening, we found luteolin is able to inhibit EBV reactivation. It inhibited EBV lytic protein expression and repressed the promoter activities of two major immediate-early genes, Zta and Rta. Furthermore, luteolin was shown to reduce genomic instability induced by recurrent EBV reactivation in NPC cells. EBV reactivation-induced NPC cell proliferation and migration, as well as matrigel invasiveness, were also repressed by luteolin treatment. Tumorigenicity in mice, induced by EBV reactivation, was decreased profoundly following luteolin administration. Together, these results suggest that inhibition of EBV reactivation is a novel approach to prevent the relapse of NPC. PMID:26967558

  19. Cytotype Regulation Facilitates Repression of Hybrid Dysgenesis by Naturally Occurring KP Elements in Drosophila melanogaster

    PubMed Central

    Simmons, Michael J.; Grimes, Craig D.; Czora, Cody S.

    2016-01-01

    P elements inserted in the Telomere Associated Sequences (TAS) at the left end of the X chromosome are determiners of cytotype regulation of the entire P family of transposons. This regulation is mediated by Piwi-interacting (pi) RNAs derived from the telomeric P elements (TPs). Because these piRNAs are transmitted maternally, cytotype regulation is manifested as a maternal effect of the TPs. When a TP is combined with a transgenic P element inserted at another locus, this maternal effect is strengthened. However, when certain TPs are combined with transgenes that contain the small P element known as KP, stronger regulation arises from a zygotic effect of the KP element. This zygotic effect is observed with transgenic KP elements that are structurally intact, as well as with KP elements that are fused to an ancillary promoter from the hsp70 gene. Zygotic regulation by a KP element occurs only when a TP was present in the maternal germ line, and it is more pronounced when the TP was also present in the grand-maternal germ line. However, this regulation does not require zygotic expression of the TP. These observations can be explained if maternally transmitted piRNAs from TPs enable a polypeptide encoded by KP elements to repress P element transposition in zygotes that contain a KP element. In nature, repression by the KP polypeptide may therefore be facilitated by cytotype-mediating piRNAs. PMID:27172198

  20. Recovering a repressed memory, and representational shift in an adolescent.

    PubMed

    Szajnberg, N M

    1993-01-01

    This case report focuses on the disappearance of a fixed pictorial iconic representation and transformation to symbolic (word) representation following the recovery of a repressed memory in a twelve-and-a-half-year-old after the first eleven months of psychoanalysis. There is a substantial body of psychoanalytic literature on the importance of language, naming or articulation of experiences associated with transformation of psychic structure (Fenichel, 1941; Glover, 1955; Kris, 1956a, 1956b; Werner and Kaplan, 1963; Schafer, 1976, 1978a, 1978b, 1980; Shapiro, 1979; Spence, 1982; Stern, 1989) and a relatively autonomous literature on the communicative representational power of children's play or visual portrayals (Piaget, 1962; A. Freud, 1947; Klein, 1964; Axeline, 1947; Esman, 1983; Neubauer et al., 1987; Krall, 1989). To our knowledge, there is no report of the structural effect of the recovery of a repressed traumatic experience, in this case, with subsequent parental confirmation of the traumatic event. PMID:8354843

  1. Msx1 Homeodomain Protein Represses the αGSU and GnRH Receptor Genes During Gonadotrope Development

    PubMed Central

    Xie, Huimin; Cherrington, Brian D.; Meadows, Jason D.; Witham, Emily A.

    2013-01-01

    Multiple homeodomain transcription factors are crucial for pituitary organogenesis and cellular differentiation. A homeodomain repressor, Msx1, is expressed from the ventral aspect of the developing anterior pituitary and implicated in gonadotrope differentiation. Here, we find that Msx1 represses transcription of lineage-specific pituitary genes such as the common α-glycoprotein subunit (αGSU) and GnRH receptor (GnRHR) promoters in the mouse gonadotrope-derived cell lines, αT3-1 and LβT2. Repression of the mouse GnRHR promoter by Msx1 is mediated through a consensus-binding motif in the downstream activin regulatory element (DARE). Truncation and mutation analyses of the human αGSU promoter map Msx1 repression to a site at −114, located at the junctional regulatory element (JRE). Dlx activators are closely related to the Msx repressors, acting through the same elements, and Dlx3 and Dlx2 act as transcriptional activators for GnRHR and αGSU, respectively. Small interfering RNA knockdown of Msx1 in αT3-1 cells increases endogenous αGSU and GnRHR mRNA expression. Msx1 gene expression reaches its maximal expression at the rostral edge at e13.5. The subsequent decline in Msx1 expression specifically coincides with the onset of expression of both αGSU and GnRHR. The expression levels of both αGSU and GnRHR in Msx1-null mice at e18.5 are higher compared with wild type, further confirming a role for Msx1 in the repression of αGSU and GnRHR. In summary, Msx1 functions as a negative regulator early in pituitary development by repressing the gonadotrope-specific αGSU and GnRHR genes, but a temporal decline in Msx1 expression alleviates this repression allowing induction of GnRHR and αGSU, thus serving to time the onset of gonadotrope-specific gene program. PMID:23371388

  2. Glucocorticoid Repression of Inflammatory Gene Expression Shows Differential Responsiveness by Transactivation- and Transrepression-Dependent Mechanisms

    PubMed Central

    King, Elizabeth M.; Chivers, Joanna E.; Rider, Christopher F.; Minnich, Anne; Giembycz, Mark A.; Newton, Robert

    2013-01-01

    Binding of glucocorticoid to the glucocorticoid receptor (GR/NR3C1) may repress inflammatory gene transcription via direct, protein synthesis-independent processes (transrepression), or by activating transcription (transactivation) of multiple anti-inflammatory/repressive factors. Using human pulmonary A549 cells, we showed that 34 out of 39 IL-1β-inducible mRNAs were repressed to varying degrees by the synthetic glucocorticoid, dexamethasone. Whilst these repressive effects were GR-dependent, they did not correlate with either the magnitude of IL-1β-inducibility or the NF-κB-dependence of the inflammatory genes. This suggests that induction by IL-1β and repression by dexamethasone are independent events. Roles for transactivation were investigated using the protein synthesis inhibitor, cycloheximide. However, cycloheximide reduced the IL-1β-dependent expression of 13 mRNAs, which, along with the 5 not showing repression by dexamethasone, were not analysed further. Of the remaining 21 inflammatory mRNAs, cycloheximide significantly attenuated the dexamethasone-dependent repression of 11 mRNAs that also showed a marked time-dependence to their repression. Such effects are consistent with repression occurring via the de novo synthesis of a new product, or products, which subsequently cause repression (i.e., repression via a transactivation mechanism). Conversely, 10 mRNAs showed completely cycloheximide-independent, and time-independent, repression by dexamethasone. This is consistent with direct GR transrepression. Importantly, the inflammatory mRNAs showing attenuated repression by dexamethasone in the presence of cycloheximide also showed a significantly greater extent of repression and a higher potency to dexamethasone compared to those mRNAs showing cycloheximide-independent repression. This suggests that the repression of inflammatory mRNAs by GR transactivation-dependent mechanisms accounts for the greatest levels of repression and the most potent

  3. TBX2 represses PTEN in rhabdomyosarcoma and skeletal muscle

    PubMed Central

    Zhu, Bo; Zhang, Meiling; Williams, Elizabeth M.; Keller, Charles; Mansoor, Atiya; Davie, Judith K.

    2015-01-01

    Rhabdomyosarcoma (RMS) is the most frequent soft tissue sarcoma in children that shares many features of developing skeletal muscle. TBX2, a T-box family member, is highly up regulated in tumor cells of both major RMS subtypes where it functions as an oncogene. TBX2 is a repressor that is often over expressed in cancer cells and functions in bypassing cell growth control, including the repression of the cell cycle regulators p14 and p21. We have found that TBX2 directly represses the tumor suppressor PTEN in both RMS and normal muscle. Exogenous expression of TBX2 in normal muscle cells down regulates PTEN, and depletion or interference with TBX2 in RMS cells up regulates PTEN. Human RMS tumors show high levels of TBX2 and correspondingly low levels of PTEN. The expression of PTEN in clinical RMS samples is relatively uncharacterized and we establish that suppression of PTEN is a frequent event in both subtypes of RMS. TBX2 represses PTEN by directly binding to the promoter and recruiting the histone deacetylase, HDAC1. RMS cells have high levels of activated AKT due to the deregulation of PI3K signaling, and depletion or interference with TBX2, which up regulates PTEN, results in a reduction of phospho-AKT. We have also found that the highly related T-box family member TBX3 does not repress PTEN in the muscle lineage. This work suggests that TBX2 is a central component of the PTEN/PI3K/AKT signaling pathway deregulation in RMS cells and that targeting TBX2 in RMS tumors may offer a novel therapeutic approach for RMS. PMID:26686089

  4. TBX2 represses PTEN in rhabdomyosarcoma and skeletal muscle.

    PubMed

    Zhu, B; Zhang, M; Williams, E M; Keller, C; Mansoor, A; Davie, J K

    2016-08-11

    Rhabdomyosarcoma (RMS) is the most frequent soft tissue sarcoma in children that shares many features of developing skeletal muscle. TBX2, a T-box family member, is highly upregulated in tumor cells of both major RMS subtypes where it functions as an oncogene. TBX2 is a repressor that is often overexpressed in cancer cells and functions in bypassing cell growth control, including the repression of the cell cycle regulators p14 and p21. We have found that TBX2 directly represses the tumor-suppressor phosphatase and tensin homolog (PTEN) in both RMS and normal muscle. Exogenous expression of TBX2 in normal muscle cells downregulates PTEN, and depletion or interference with TBX2 in RMS cells upregulates PTEN. Human RMS tumors show high levels of TBX2 and correspondingly low levels of PTEN. The expression of PTEN in clinical RMS samples is relatively uncharacterized, and we establish that suppression of PTEN is a frequent event in both subtypes of RMS. TBX2 represses PTEN by directly binding to the promoter and recruiting the histone deacetylase, HDAC1. RMS cells have high levels of activated AKT owing to the deregulation of phosphoinositide-3 kinase (PI3K) signaling, and depletion or interference with TBX2, which upregulates PTEN, results in a reduction of phospho-AKT. We have also found that the highly related T-box family member TBX3 does not repress PTEN in the muscle lineage. This work suggests that TBX2 is a central component of the PTEN/PI3K/AKT signaling pathway deregulation in RMS cells and that targeting TBX2 in RMS tumors may offer a novel therapeutic approach for RMS.

  5. Repressive coping and alexithymia in idiopathic environmental intolerance

    PubMed Central

    Zachariae, Robert; Rasmussen, Alice; Johansen, Jeanne Duus; Elberling, Jesper

    2010-01-01

    Objective To examine if the non-expression of negative emotions (i.e., repressive coping) and differences in the ability to process and regulate emotions (i.e., alexithymia) is associated with idiopathic environmental intolerance (IEI). Methods The study included participants who had previously participated in a general population-based study and reported symptoms of environmental intolerance (n = 787) and patients with IEI (n = 237). The participants completed questionnaires assessing IEI, namely, a measure of repressive coping combining scores on the Marlowe–Crowne Social Desirability Scale (MCSDS) and the Taylor Manifest Anxiety Scale (TMAS), the Toronto Alexithymia Scale (TAS-20), and a negative affectivity scale (NAS). Multiple, hierarchical linear regression analyses were conducted using IEI variables as the dependent variables. Results The TMAS and MCSDS scores were independently associated with the IEI variables, but there was no evidence of a role of the repressive coping construct. While the total alexithymia score was unrelated to IEI, the TAS-20 subscale of difficulties identifying feelings (DIF) was independently associated with symptoms attributed to IEI. Negative affectivity was a strong independent predictor of the IEI variables and a mediator of the association between DIF and IEI. Conclusion Our results provide no evidence for a role of repressive coping in IEI, and our hypothesis of an association with alexithymia was only partly supported. In contrast, strong associations between IEI and negative emotional reactions, defensiveness and difficulties identifying feelings were found, suggesting a need for exploring the influence of these emotional reactions in IEI. PMID:21432559

  6. CRISPR transcriptional repression devices and layered circuits in mammalian cells

    PubMed Central

    Kiani, Samira; Beal, Jacob; Ebrahimkhani, Mohammad R; Huh, Jin; Hall, Richard N; Xie, Zhen; Li, Yinqing; Weiss, Ron

    2014-01-01

    A key obstacle to creating sophisticated genetic circuits has been the lack of scalable device libraries. Here we present a modular transcriptional repression architecture based on clustered regularly interspaced palindromic repeats (CRISPR) system and examine approaches for regulated expression of guide RNAs in human cells. Subsequently we demonstrate that CRISPR regulatory devices can be layered to create functional cascaded circuits, which provide a valuable toolbox for engineering purposes. PMID:24797424

  7. CRISPR transcriptional repression devices and layered circuits in mammalian cells.

    PubMed

    Kiani, Samira; Beal, Jacob; Ebrahimkhani, Mohammad R; Huh, Jin; Hall, Richard N; Xie, Zhen; Li, Yinqing; Weiss, Ron

    2014-07-01

    A key obstacle to creating sophisticated genetic circuits has been the lack of scalable device libraries. Here we present a modular transcriptional repression architecture based on clustered regularly interspaced palindromic repeats (CRISPR) system and examine approaches for regulated expression of guide RNAs in human cells. Subsequently we demonstrate that CRISPR regulatory devices can be layered to create functional cascaded circuits, which provide a valuable toolbox for engineering purposes. PMID:24797424

  8. Lysine methylation represses p53 activity in teratocarcinoma cancer cells.

    PubMed

    Zhu, Jiajun; Dou, Zhixun; Sammons, Morgan A; Levine, Arnold J; Berger, Shelley L

    2016-08-30

    TP53 (which encodes the p53 protein) is the most frequently mutated gene among all human cancers, whereas tumors that retain the wild-type TP53 gene often use alternative mechanisms to repress the p53 tumor-suppressive function. Testicular teratocarcinoma cells rarely contain mutations in TP53, yet the transcriptional activity of wild-type p53 is compromised, despite its high expression level. Here we report that in the teratocarcinoma cell line NTera2, p53 is subject to lysine methylation at its carboxyl terminus, which has been shown to repress p53's transcriptional activity. We show that reduction of the cognate methyltransferases reactivates p53 and promotes differentiation of the NTera2 cells. Furthermore, reconstitution of methylation-deficient p53 mutants into p53-depleted NTera2 cells results in elevated expression of p53 downstream targets and precocious loss of pluripotent gene expression compared with re-expression of wild-type p53. Our results provide evidence that lysine methylation of endogenous wild-type p53 represses its activity in cancer cells and suggest new therapeutic possibilities of targeting testicular teratocarcinoma. PMID:27535933

  9. Revisiting the Master-Signifier, or, Mandela and Repression.

    PubMed

    Hook, Derek; Vanheule, Stijn

    2015-01-01

    The concept of the master-signifier has been subject to a variety of applications in Lacanian forms of political discourse theory and ideology critique. While there is much to be commended in literature of this sort, it often neglects salient issues pertaining to the role of master signifiers in the clinical domain of (individual) psychical economy. The popularity of the concept of the master (or "empty") signifier in political discourse analysis has thus proved a double-edged sword. On the one hand it demonstrates how crucial psychical processes are performed via the operations of the signifier, extending thus the Lacanian thesis that identification is the outcome of linguistic and symbolic as opposed to merely psychological processes. On the other, the use of the master signifier concept within the political realm to track discursive formations tends to distance the term from the dynamics of the unconscious and operation of repression. Accordingly, this paper revisits the master signifier concept, and does so within the socio-political domain, yet while paying particular attention to the functioning of unconscious processes of fantasy and repression. More specifically, it investigates how Nelson Mandela operates as a master signifier in contemporary South Africa, as a vital means of knitting together diverse elements of post-apartheid society, enabling the fantasy of the post-apartheid nation, and holding at bay a whole series of repressed and negated undercurrents. PMID:26834664

  10. Carbon Catabolite Repression Regulates Glyoxylate Cycle Gene Expression in Cucumber.

    PubMed Central

    Graham, I. A.; Denby, K. J.; Leaver, C. J.

    1994-01-01

    We have previously proposed that metabolic status is important in the regulation of cucumber malate synthase (MS) and isocitrate lyase (ICL) gene expression during plant development. In this article, we used a cell culture system to demonstrate that intracellular metabolic status does influence expression of both of these genes. Starvation of cucumber cell cultures resulted in the coordinate induction of the expression of MS and ICL genes, and this effect was reversed when sucrose was returned to the culture media. The induction of gene expression was closely correlated with a drop in intracellular sucrose, glucose, and fructose below threshold concentrations, but it was not correlated with a decrease in respiration rate. Glucose, fructose, or raffinose in the culture media also resulted in repression of MS and ICL. Both 2-deoxyglucose and mannose, which are phosphorylated by hexokinase but not further metabolized, specifically repressed MS and ICL gene expression relative to a third glyoxylate cycle gene, malate dehydrogenase. However, the addition of 3-methylglucose, an analog of glucose that is not phosphorylated, did not result in repression of either MS or ICL. It is proposed that the signal giving rise to a change in gene expression originates from the intracellular concentration of hexose sugars or the flux of hexose sugars into glycolysis. PMID:12244257

  11. Revisiting the Master-Signifier, or, Mandela and Repression

    PubMed Central

    Hook, Derek; Vanheule, Stijn

    2016-01-01

    The concept of the master-signifier has been subject to a variety of applications in Lacanian forms of political discourse theory and ideology critique. While there is much to be commended in literature of this sort, it often neglects salient issues pertaining to the role of master signifiers in the clinical domain of (individual) psychical economy. The popularity of the concept of the master (or “empty”) signifier in political discourse analysis has thus proved a double-edged sword. On the one hand it demonstrates how crucial psychical processes are performed via the operations of the signifier, extending thus the Lacanian thesis that identification is the outcome of linguistic and symbolic as opposed to merely psychological processes. On the other, the use of the master signifier concept within the political realm to track discursive formations tends to distance the term from the dynamics of the unconscious and operation of repression. Accordingly, this paper revisits the master signifier concept, and does so within the socio-political domain, yet while paying particular attention to the functioning of unconscious processes of fantasy and repression. More specifically, it investigates how Nelson Mandela operates as a master signifier in contemporary South Africa, as a vital means of knitting together diverse elements of post-apartheid society, enabling the fantasy of the post-apartheid nation, and holding at bay a whole series of repressed and negated undercurrents. PMID:26834664

  12. Lysine methylation represses p53 activity in teratocarcinoma cancer cells.

    PubMed

    Zhu, Jiajun; Dou, Zhixun; Sammons, Morgan A; Levine, Arnold J; Berger, Shelley L

    2016-08-30

    TP53 (which encodes the p53 protein) is the most frequently mutated gene among all human cancers, whereas tumors that retain the wild-type TP53 gene often use alternative mechanisms to repress the p53 tumor-suppressive function. Testicular teratocarcinoma cells rarely contain mutations in TP53, yet the transcriptional activity of wild-type p53 is compromised, despite its high expression level. Here we report that in the teratocarcinoma cell line NTera2, p53 is subject to lysine methylation at its carboxyl terminus, which has been shown to repress p53's transcriptional activity. We show that reduction of the cognate methyltransferases reactivates p53 and promotes differentiation of the NTera2 cells. Furthermore, reconstitution of methylation-deficient p53 mutants into p53-depleted NTera2 cells results in elevated expression of p53 downstream targets and precocious loss of pluripotent gene expression compared with re-expression of wild-type p53. Our results provide evidence that lysine methylation of endogenous wild-type p53 represses its activity in cancer cells and suggest new therapeutic possibilities of targeting testicular teratocarcinoma.

  13. Repression and activation by multiprotein complexes that alter chromatin structure.

    PubMed

    Kingston, R E; Bunker, C A; Imbalzano, A N

    1996-04-15

    Recent studies have provided strong evidence that macromolecular complexes are used in the cell to remodel chromatin structure during activation and to create an inaccessible structure during repression, Although there is not yet any rigorous demonstration that modification of chromatin structure plays a direct, causal role in either activation or repression, there is sufficient smoke to indicate the presence of a blazing inferno nearby. It is clear that complexes that remodel chromatin are tractable in vitro; hopefully this will allow the establishment of systems that provide a direct analysis of the role that remodeling might play in activation. These studies indicate that establishment of functional systems to corroborate the elegant genetic studies on repression might also be tractable. As the mechanistic effects of these complexes are sorted out, it will become important to understand how the complexes are regulated. In many of the instances discussed above, the genes whose products make up these complexes were identified in genetic screens for effects on developmental processes. This implies a regulation of the activity of these complexes in response to developmental cues and further implies that the work to fully understand these complexes will occupy a generation of scientists.

  14. Nitric oxide participates in plant flowering repression by ascorbate

    PubMed Central

    Senthil Kumar, Rajendran; Shen, Chin-Hui; Wu, Pei-Yin; Suresh Kumar, Subbiah; Hua, Moda Sang; Yeh, Kai-Wun

    2016-01-01

    In Oncidium, redox homeostasis involved in flowering is mainly due to ascorbic acid (AsA). Here, we discovered that Oncidium floral repression is caused by an increase in AsA-mediated NO levels, which is directed by the enzymatic activities of nitrate reductase (NaR) and nitrite reducatase (NiR). Through Solexa transcriptomic analysis of two libraries, ‘pseudobulb with inflorescent bud’ (PIB) and ‘pseudobulb with axillary bud’ (PAB), we identified differentially expressed genes related to NO metabolism. Subsequently, we showed a significant reduction of NaR enzymatic activities and NO levels during bolting and blooming stage, suggesting that NO controlled the phase transition and flowering process. Applying AsA to Oncidium PLB (protocorm-like bodies) significantly elevated the NO content and enzyme activities. Application of sodium nitroprusside (-NO donor) on Arabidopsis vtc1 mutant caused late flowering and expression level of flowering-associated genes (CO, FT and LFY) were reduced, suggesting NO signaling is vital for flowering repression. Conversely, the flowering time of noa1, an Arabidopsis NO-deficient mutant, was not altered after treatment with L-galacturonate, a precursor of AsA, suggesting AsA is required for NO-biosynthesis involved in the NO-mediated flowering-repression pathway. Altogether, Oncidium bolting is tightly regulated by AsA-mediated NO level and downregulation of transcriptional levels of NO metabolism genes. PMID:27731387

  15. Quantitative contributions of CtBP-dependent and -independent repression activities of Knirps.

    PubMed

    Struffi, Paolo; Corado, Maria; Kulkarni, Meghana; Arnosti, David N

    2004-05-01

    The Drosophila Knirps protein is a short-range transcriptional repressor that locally inhibits activators by recruiting the CtBP co-repressor. Knirps also possesses CtBP-independent repression activity. The functional importance of multiple repression activities is not well understood, but the finding that Knirps does not repress some cis-regulatory elements in the absence of CtBP suggested that the co-factor may supply a unique function essential to repress certain types of activators. We assayed CtBP-dependent and -independent repression domains of Knirps in Drosophila embryos, and found that the CtBP-independent activity, when provided at higher than normal levels, can repress an eve regulatory element that normally requires CtBP. Dose response analysis revealed that the activity of Knirps containing both CtBP-dependent and -independent repression activities is higher than that of the CtBP-independent domain alone. The requirement for CtBP at certain enhancers appears to reflect the need for overall higher levels of repression, rather than a requirement for an activity unique to CtBP. Thus, CtBP contributes quantitatively, rather than qualitatively, to overall repression function. The finding that both repression activities are simultaneously deployed suggests that the multiple repression activities do not function as cryptic 'backup' systems, but that each contributes quantitatively to total repressor output.

  16. Cell-Context Dependent TCF/LEF Expression and Function: Alternative Tales of Repression, De-Repression and Activation Potentials

    PubMed Central

    Mao, Catherine D; Byers, Stephen W.

    2012-01-01

    Wnt signaling controls cell specification and fate during development and adult tissue homeostasis by converging on a small family of DNA binding factors, the T-cell factor/lymphoid enhancer factor (TCF/LEF) family. In response to Wnt signals, TCF/LEF members undergo a transcriptional switch from repression to activation mediated in part by nuclear β-catenin binding and recruitment of co-activator complexes. In mammals, the specificity and fine tuning of this transcriptional switch is also achieved by the cell-context-dependent expression of four members (TCF7, TCF7L1, TCF7L2, and LEF1) and numerous variants, which display differential DNA binding affinity and specificity, repression strength, activation potential, and regulators. TCF7/LEF1 variants are generated by alternative promoters, alternative exon cassettes, and alternative donor/acceptor splicing sites, allowing combinatorial insertion/exclusion of modular functional and regulatory domains. In this review we present mounting evidence for the interdependency of TCF7/LEF1 variant expression and functions with cell lineage and cell state. We also illustrate how the p53 and nuclear receptor family of transcription factors, known to control cell fate and to inhibit Wnt signaling, may participate in the fine tuning of TCF7/LEF1 repression/activation potentials. PMID:22111711

  17. Repression of death consciousness and the psychedelic trip.

    PubMed

    Dutta, Varsha

    2012-01-01

    Death is our most repressed consciousness, it inheres our condition as the primordial fear. Perhaps it was necessary that this angst be repressed in man or he would be hurled against the dark forces of nature. Modern ethos was built on this edifice, where the 'denial of death' while 'embracing one's symbolic immortality' would be worshipped, so this ideology simply overturned and repressed looking into the morass of the inevitable when it finally announced itself. Once this slowly pieced its way into all of life, 'death' would soon become a terminology in medicine too and assert its position, by giving a push to those directly dealing with the dying to shy away from its emotional and spiritual affliction. The need to put off death and prolong one's life would become ever more urgent. Research using psychedelics on the terminally ill which had begun in the 1950s and 1960s would coerce into another realm and alter the face of medicine; but the aggression with which it forced itself in the 1960s would soon be politically maimed, and what remained would be sporadic outpours that trickled its way from European labs and underground boot camps. Now, with the curtain rising, the question has etched itself again, about the use of psychedelic drugs in medicine, particularly psychedelic psychotherapy with the terminally ill. This study is an attempt to philosophically explore death anxiety from its existential context and how something that is innate in our condition cannot be therapeutically cured. Psychedelic use was immutably linked with ancient cultures and only recently has it seen its scientific revival, from which a scientific culture grew around psychedelic therapy. How much of what was threaded in the ritual and spiritual mores can be extricated and be interpreted in our own mechanized language of medicine is the question that nudges many.

  18. Blood-Brain Glucose Transfer: Repression in Chronic Hyperglycemia

    NASA Astrophysics Data System (ADS)

    Gjedde, Albert; Crone, Christian

    1981-10-01

    Diabetic patients with increased plasma glucose concentrations may develop cerebral symptoms of hypoglycemia when their plasma glucose is rapidly lowered to normal concentrations. The symptoms may indicate insufficient transport of glucose from blood to brain. In rats with chronic hyperglycemia the maximum glucose transport capacity of the blood-brain barrier decreased from 400 to 290 micromoles per 100 grams per minute. When plasma glucose was lowered to normal values, the glucose transport rate into brain was 20 percent below normal. This suggests that repressive changes of the glucose transport mechanism occur in brain endothelial cells in response to increased plasma glucose.

  19. ATF3 represses PPARγ expression and inhibits adipocyte differentiation

    SciTech Connect

    Jang, Min-Kyung; Jung, Myeong Ho

    2014-11-07

    Highlights: • ATF3 decrease the expression of PPARγ and its target gene in 3T3-L1 adipocytes. • ATF3 represses the promoter activity of PPARγ2 gene. • ATF/CRE (−1537/−1530) is critical for ATF3-mediated downregulation of PPARγ. • ATF3 binds to the promoter region containing the ATF/CRE. • ER stress inhibits adipocyte differentiation through downregulation of PPARγ by ATF3. - Abstract: Activating transcription factor 3 (ATF3) is a stress-adaptive transcription factor that mediates cellular stress response signaling. We previously reported that ATF3 represses CCAAT/enhancer binding protein α (C/EBPα) expression and inhibits 3T3-L1 adipocyte differentiation. In this study, we explored potential role of ATF3 in negatively regulating peroxisome proliferator activated receptor-γ (PPARγ). ATF3 decreased the expression of PPARγ and its target gene in 3T3-L1 adipocytes. ATF3 also repressed the activity of −2.6 Kb promoter of mouse PPARγ2. Overexpression of PPARγ significantly prevented the ATF3-mediated inhibition of 3T3-L1 differentiation. Transfection studies with 5′ deleted-reporters showed that ATF3 repressed the activity of −2037 bp promoter, whereas it did not affect the activity of −1458 bp promoter, suggesting that ATF3 responsive element is located between the −2037 and −1458. An electrophoretic mobility shift assay and chromatin immunoprecipitation assay demonstrated that ATF3 binds to ATF/CRE site (5′-TGACGTTT-3′) between −1537 and −1530. Mutation of the ATF/CRE site abrogated ATF3-mediated transrepression of the PPARγ2 promoter. Treatment with thapsigargin, endoplasmic reticulum (ER) stress inducer, increased ATF3 expression, whereas it decreased PPARγ expression. ATF3 knockdown significantly blocked the thapsigargin-mediated downregulation of PPARγ expression. Furthermore, overexpression of PPARγ prevented inhibition of 3T3-L1 differentiation by thapsigargin. Collectively, these results suggest that ATF3-mediated

  20. The Retinoblastoma Tumor Suppressor Transcriptionally Represses Pak1 in Osteoblasts

    PubMed Central

    Sosa-García, Bernadette; Vázquez-Rivera, Viviana; González-Flores, Jonathan N.; Engel, Brienne E.; Cress, W. Douglas; Santiago-Cardona, Pedro G.

    2015-01-01

    We previously characterized the retinoblastoma tumor suppressor protein (Rb) as a regulator of adherens junction assembly and cell-to-cell adhesion in osteoblasts. This is a novel function since Rb is predominantly known as a cell cycle repressor. Herein, we characterized the molecular mechanisms by which Rb performs this function, hypothesizing that Rb controls the activity of known regulators of adherens junction assembly. We found that Rb represses the expression of the p21-activated protein kinase (Pak1), an effector of the small Rho GTPase Rac1. Rac1 is a well-known regulator of adherens junction assembly whose increased activity in cancer is linked to perturbations of intercellular adhesion. Using nuclear run-on and luciferase reporter transcription assays, we found that Pak1 repression by Rb is transcriptional, without affecting Pak1 mRNA and protein stability. Pak1 promoter bioinformatics showed multiple E2F1 binding sites within 155 base pairs of the transcriptional start site, and a Pak1-promoter region containing these E2F sites is susceptible to transcriptional inhibition by Rb. Chromatin immunoprecipitations showed that an Rb-E2F complex binds to the region of the Pak1 promoter containing the E2F1 binding sites, suggesting that Pak1 is an E2F target and that the repressive effect of Rb on Pak1 involves blocking the trans-activating capacity of E2F. A bioinformatics analysis showed elevated Pak1 expression in several solid tumors relative to adjacent normal tissue, with both Pak1 and E2F increased relative to normal tissue in breast cancer, supporting a cancer etiology for Pak1 up-regulation. Therefore, we propose that by repressing Pak1 expression, Rb prevents Rac1 hyperactivity usually associated with cancer and related to cytoskeletal derangements that disrupt cell adhesion, consequently enhancing cancer cell migratory capacity. This de-regulation of cell adhesion due to Rb loss could be part of the molecular events associated with cancer progression

  1. Specific Gene Repression by CRISPRi System Transferred through Bacterial Conjugation

    PubMed Central

    2014-01-01

    In microbial communities, bacterial populations are commonly controlled using indiscriminate, broad range antibiotics. There are few ways to target specific strains effectively without disrupting the entire microbiome and local environment. Here, we use conjugation, a natural DNA horizontal transfer process among bacterial species, to deliver an engineered CRISPR interference (CRISPRi) system for targeting specific genes in recipient Escherichia coli cells. We show that delivery of the CRISPRi system is successful and can specifically repress a reporter gene in recipient cells, thereby establishing a new tool for gene regulation across bacterial cells and potentially for bacterial population control. PMID:25409531

  2. Hypomethylation of Intragenic LINE-1 Represses Transcription in Cancer Cells through AGO2

    PubMed Central

    Ittiwut, Chupong; Tongsima, Sissades; Mutirangura, Apiwat

    2011-01-01

    In human cancers, the methylation of long interspersed nuclear element -1 (LINE-1 or L1) retrotransposons is reduced. This occurs within the context of genome wide hypomethylation, and although it is common, its role is poorly understood. L1s are widely distributed both inside and outside of genes, intragenic and intergenic, respectively. Interestingly, the insertion of active full-length L1 sequences into host gene introns disrupts gene expression. Here, we evaluated if intragenic L1 hypomethylation influences their host gene expression in cancer. First, we extracted data from L1base (http://l1base.molgen.mpg.de), a database containing putatively active L1 insertions, and compared intragenic and intergenic L1 characters. We found that intragenic L1 sequences have been conserved across evolutionary time with respect to transcriptional activity and CpG dinucleotide sites for mammalian DNA methylation. Then, we compared regulated mRNA levels of cells from two different experiments available from Gene Expression Omnibus (GEO), a database repository of high throughput gene expression data, (http://www.ncbi.nlm.nih.gov/geo) by chi-square. The odds ratio of down-regulated genes between demethylated normal bronchial epithelium and lung cancer was high (p<1E−27; OR = 3.14; 95% CI = 2.54–3.88), suggesting cancer genome wide hypomethylation down-regulating gene expression. Comprehensive analysis between L1 locations and gene expression showed that expression of genes containing L1s had a significantly higher likelihood to be repressed in cancer and hypomethylated normal cells. In contrast, many mRNAs derived from genes containing L1s are elevated in Argonaute 2 (AGO2 or EIF2C2)-depleted cells. Hypomethylated L1s increase L1 mRNA levels. Finally, we found that AGO2 targets intronic L1 pre-mRNA complexes and represses cancer genes. These findings represent one of the mechanisms of cancer genome wide hypomethylation altering gene expression. Hypomethylated

  3. Musashi mediates translational repression of the Drosophila hypoxia inducible factor.

    PubMed

    Bertolin, Agustina P; Katz, Maximiliano J; Yano, Masato; Pozzi, Berta; Acevedo, Julieta M; Blanco-Obregón, Dalmiro; Gándara, Lautaro; Sorianello, Eleonora; Kanda, Hiroshi; Okano, Hideyuki; Srebrow, Anabella; Wappner, Pablo

    2016-09-19

    Adaptation to hypoxia depends on a conserved α/β heterodimeric transcription factor called Hypoxia Inducible Factor (HIF), whose α-subunit is regulated by oxygen through different concurrent mechanisms. In this study, we have identified the RNA binding protein dMusashi, as a negative regulator of the fly HIF homologue Sima. Genetic interaction assays suggested that dMusashi participates of the HIF pathway, and molecular studies carried out in Drosophila cell cultures showed that dMusashi recognizes a Musashi Binding Element in the 3' UTR of the HIFα transcript, thereby mediating its translational repression in normoxia. In hypoxic conditions dMusashi is downregulated, lifting HIFα repression and contributing to trigger HIF-dependent gene expression. Analysis performed in mouse brains revealed that murine Msi1 protein physically interacts with HIF-1α transcript, suggesting that the regulation of HIF by Msi might be conserved in mammalian systems. Thus, Musashi is a novel regulator of HIF that inhibits responses to hypoxia specifically when oxygen is available.

  4. Musashi mediates translational repression of the Drosophila hypoxia inducible factor

    PubMed Central

    Bertolin, Agustina P.; Katz, Maximiliano J.; Yano, Masato; Pozzi, Berta; Acevedo, Julieta M.; Blanco-Obregón, Dalmiro; Gándara, Lautaro; Sorianello, Eleonora; Kanda, Hiroshi; Okano, Hideyuki; Srebrow, Anabella; Wappner, Pablo

    2016-01-01

    Adaptation to hypoxia depends on a conserved α/β heterodimeric transcription factor called Hypoxia Inducible Factor (HIF), whose α-subunit is regulated by oxygen through different concurrent mechanisms. In this study, we have identified the RNA binding protein dMusashi, as a negative regulator of the fly HIF homologue Sima. Genetic interaction assays suggested that dMusashi participates of the HIF pathway, and molecular studies carried out in Drosophila cell cultures showed that dMusashi recognizes a Musashi Binding Element in the 3′ UTR of the HIFα transcript, thereby mediating its translational repression in normoxia. In hypoxic conditions dMusashi is downregulated, lifting HIFα repression and contributing to trigger HIF-dependent gene expression. Analysis performed in mouse brains revealed that murine Msi1 protein physically interacts with HIF-1α transcript, suggesting that the regulation of HIF by Msi might be conserved in mammalian systems. Thus, Musashi is a novel regulator of HIF that inhibits responses to hypoxia specifically when oxygen is available. PMID:27141964

  5. Ski represses BMP signaling in Xenopus and mammalian cells

    SciTech Connect

    kluo@lbl.gov

    2001-05-16

    The bone morphogenic proteins (BMPs) play important roles in vertebrate development. In Xenopus, BMPs act as epidermal inducers and also as negative regulators of neurogenesis. Antagonism of BMP signaling results in neuralization. BMPs signal through the cell-surface receptors and downstream Smad molecules. Upon stimulation with BMP, Smad1, Smad5, and Smad8 are phosphorylated by the activated BMP receptors, form a complex with Smad4, and translocate into the nucleus, where they regulate the expression of BMP target genes. Here, we show that the Ski oncoprotein can block BMP signaling and the expression of BMP-responsive genes in both Xenopus and mammalian cells by directly interacting with and repressing the activity of BMP-specific Smad complexes. This ability to antagonize BMP signaling results in neuralization by Ski in the Xenopus embryo and blocking of osteoblast differentiation of murine W-20-17 cells. Thus, Ski is able to repress the activity of all receptor-associated Smads and may regulate vertebrate development by modulating the signaling activity of transforming growth factor-{beta} family members.

  6. Quantitative dissection of the simple repression input–output function

    PubMed Central

    Garcia, Hernan G.; Phillips, Rob

    2011-01-01

    We present a quantitative case study of transcriptional regulation in which we carry out a systematic dialogue between theory and measurement for an important and ubiquitous regulatory motif in bacteria, namely, that of simple repression. This architecture is realized by a single repressor binding site overlapping the promoter. From the theory point of view, this motif is described by a single gene regulation function based upon only a few parameters that are convenient theoretically and accessible experimentally. The usual approach is turned on its side by using the mathematical description of these regulatory motifs as a predictive tool to determine the number of repressors in a collection of strains with a large variation in repressor copy number. The predictions and corresponding measurements are carried out over a large dynamic range in both expression fold change (spanning nearly four orders of magnitude) and repressor copy number (spanning about two orders of magnitude). The predictions are tested by measuring the resulting level of gene expression and are then validated by using quantitative immunoblots. The key outcomes of this study include a systematic quantitative analysis of the limits and validity of the input–output relation for simple repression, a precise determination of the in vivo binding energies for DNA–repressor interactions for several distinct repressor binding sites, and a repressor census for Lac repressor in Escherichia coli. PMID:21730194

  7. Ectomycorrhiza-mediated repression of the high-affinity ammonium importer gene AmAMT2 in Amanita muscaria.

    PubMed

    Willmann, Anita; Weiss, Michael; Nehls, Uwe

    2007-02-01

    A main function of ectomycorrhizas, a symbiosis between certain soil fungi and fine roots of woody plants, is the exchange of plant-derived carbohydrates for fungus-derived nutrients. As it is required in large amounts, nitrogen is of special interest. A gene (AmAMT2) coding for a putative fungal ammonium importer was identified in an EST project of functional Amanita muscaria/poplar ectomycorrhizas. Heterologous expression of the entire AmAMT2 coding region in yeast revealed the corresponding protein to be a high-affinity ammonium importer. In axenically grown Amanita hyphae AmAMT2 expression was strongly repressed by nitrogen, independent of whether the offered nitrogen source was transported by AmAMT2 or not. In functional ectomycorrhizas the AmAMT2 transcript level was further decreased in both hyphal networks (sheath and Hartig net), while extraradical hyphae revealed strong gene expression. Together our data suggest that (1) AmAMT2 expression is regulated by the endogenous nitrogen content of hyphae and (2) fungal hyphae in ectomycorrhizas are well supported with nitrogen even when the extraradical mycelium is nitrogen limited. As a consequence of AmAMT2 repression in mycorrhizas, ammonium can be suggested as a potential nitrogen source delivered by fungal hyphae in symbiosis.

  8. Synergistic repression of anaerobic genes by Mot3 and Rox1 in Saccharomyces cerevisiae

    PubMed Central

    Sertil, Odeniel; Kapoor, Rachna; Cohen, Brian D.; Abramova, Natalia; Lowry, Charles V.

    2003-01-01

    Two groups of anaerobic genes (genes induced in anaerobic cells and repressed in aerobic cells) are negatively regulated by heme, a metabolite present only in aerobic cells. Members of both groups, the hypoxic genes and the DAN/TIR/ERG genes, are jointly repressed under aerobic conditions by two factors. One is Rox1, an HMG protein, and the second, originally designated Rox7, is shown here to be Mot3, a global C2H2 zinc finger regulator. Repression of anaerobic genes results from co-induction of Mot3 and Rox1 in aerobic cells. Repressor synthesis is triggered by heme, which de-represses a mechanism controlling expression of both MOT3 and ROX1 in anaerobic cells; it includes Hap1, Tup1, Ssn6 and a fourth unidentified factor. The constitutive expression of various anaerobic genes in aerobic rox1Δ or mot3Δ cells directly implies that neither factor can repress by itself at endogenous levels and that stringent aerobic repression results from the concerted action of both. Mot3 and Rox1 are not essential components of a single complex, since each can repress independently in the absence of the other, when artificially induced at high levels. Moreover, the two repression mechanisms appear to be distinct: as shown here repression of ANB1 by Rox1 alone requires Tup1–Ssn6, whereas repression by Mot3 does not. Though artificially high levels of either factor can repress well, the absolute efficiency observed in normal cells when both are present—at much lower levels—demonstrates a novel inhibitory synergy. Evidently, expression levels for the two mutually dependent repressors are calibrated to permit a range of variation in basal aerobic expression at different promoters with differing operator site combinations. PMID:14530431

  9. Global transcriptional and translational repression in human embryonic stem cells-derived Rett Syndrome neurons

    PubMed Central

    Li, Yun; Wang, Haoyi; Muffat, Julien; Cheng, Albert W.; Orlando, David A.; Lovén, Jakob; Kwok, Show-ming; Feldman, Danielle A.; Bateup, Helen S.; Gao, Qing; Hockemeyer, Dirk; Mitalipova, Maisam; Lewis, Caroline A.; Vander Heiden, Matthew G.; Sur, Mriganka; Young, Richard A.; Jaenisch, Rudolf

    2014-01-01

    Summary Rett Syndrome (RTT) is caused by mutations of MECP2, a methyl CpG binding protein thought to act as a global transcriptional repressor. Here we show, using an isogenic human embryonic stem cell model of RTT, that MECP2 mutant neurons display key molecular and cellular features of this disorder. Unbiased global gene expression analyses demonstrate that MECP2 functions as global gene activator in neurons but not in neural precursors. Decreased transcription in neurons was coupled with a significant reduction in nascent protein synthesis and lack of MECP2 was manifested as a severe defect in the activity of the AKT/mTOR pathway. Lack of MECP2 also leads to impaired mitochondrial function in mutant neurons. Activation of AKT/mTOR signaling by exogenous growth factors or by depleting PTEN boosted protein synthesis and ameliorated disease phenotypes in mutant neurons. Our findings indicate a vital function for MECP2 in maintaining active gene transcription in human neuronal cells. PMID:24094325

  10. Resveratrol-Mediated Repression and Reversion of Prostatic Myofibroblast Phenoconversion

    PubMed Central

    Gharaee-Kermani, Mehrnaz; Moore, Bethany B.; Macoska, Jill A.

    2016-01-01

    Background Resveratrol, a phytoalexin found in berries, peanuts, grapes, and red wine, inhibits oxidation, inflammation, and cell proliferation and collagen synthesis in multiple cell types and or animal models. It represses collagen deposition in the vasculature, heart, lung, kidney, liver, and esophagus in animal models and may have some utility as an anti-fibrotic. Recent studies have shown that increased collagen deposition and tissue stiffness in the peri-urethral area of the prostate are associated with lower urinary tract dysfunction (LUTD) and urinary obstructive symptoms. The aim of this study was to determine whether Resveratrol might be useful to inhibit or revert TGFβ- and/or CXCL12-mediated myofibroblast phenoconversion of prostate fibroblasts in vitro, and therefore whether the use of anti-fibrotic therapeutics might be efficacious for the treatment of LUTD. Methods Primary prostate and lung tissues were explanted and fibroblast monolayers expanded in vitro. Primary and N1 immortalized prostate stromal fibroblasts, as well as primary fibroblasts cultured from a normal lung and one affected by idiopathic pulmonary fibrosis (IPF) for comparison, were grown in serum–free defined media supplemented with vehicle, TGFβ or CXCL12, pre- or post-treatment with Resveratrol, and were evaluated using immunofluorescence for alpha smooth muscle actin (αSMA) and collagen I (COL1) protein expression and assessed for cell proliferation, apoptosis, and COL1 and EGR1 transcript expression. Results This study showed that low concentrations of Resveratrol (≤50 μM) had no effect on N1 or primary prostate fibroblast cell proliferation, apoptosis, or COL1 or EGR1 gene transcription but repressed and reversed myofibroblast phenoconversion. As expected, these same effects were observed for IPF lung fibroblasts though higher levels of Resveratrol (≥100uM) were required. Taken together, these data suggest that, like lung fibroblasts, prostate fibroblast to

  11. Ethanol exposure represses osteogenesis in the developing chick embryo.

    PubMed

    Li, Zhong-Yang; Ma, Zheng-Lai; Lu, Wen-Hui; Cheng, Xin; Chen, Jian-Long; Song, Xiao-Yu; Chuai, Manli; Lee, Kenneth Ka Ho; Yang, Xuesong

    2016-07-01

    It is known that excess alcohol consumption during pregnancy can increase the risk of fetal alcohol spectrum disorder (FASD). However, the effect of ethanol exposure on bone morphogenesis in fetus is largely unknown. In this study, we demonstrated that ethanol treatment of gastrulating chick embryos could inhibit long bone (humerus, radius and ulna) development. Histological examination revealed that ethanol exposure reduced the width of the proliferation and hypertrophic zones. In addition, cell proliferation and alkaline phosphatase activities were repressed. We also investigated the effect on chondrogenesis and chondrogenesis was inhibited. Ethanol exposure also induced excess reactive oxygen species (ROS) production and altered the expression of osteogenesis-related genes. The inhibiting effect on flat bone (sclerotic ossicle) and the generation of cranial neural crest cells (progenitors of craniofacial bones) was also presented. In conclusion, ethanol exposure during the embryonic period retards bone development through excess ROS production and altered bone-associated gene expression. PMID:27112526

  12. Upstream operators enhance repression of the lac promoter.

    PubMed

    Mossing, M C; Record, M T

    1986-08-22

    To study regulation of transcription by distant elements, a wild-type lac operator was inserted upstream of a promoter-constitutive operator control region. The upstream operator is shown to aid in repression of transcription from the mutant control region. The effectiveness of the upstream operator as a function of its distance from the mutant control region parallels the length dependence observed for DNA cyclization. A quantitative model is proposed for action-at-a-distance of DNA control sites in which protein-protein and protein-DNA interactions are mediated by DNA looping. In this model, the effective concentrations of interacting proteins that are tethered by DNA are determined by the length of the intervening DNA and by its inherent bending and torsional stiffness. This model makes a number of predictions for both eukaryotic and prokaryotic control sequences located far from their sites of action. PMID:3090685

  13. How targets select activation or repression in response to Wnt.

    PubMed

    Murgan, Sabrina; Bertrand, Vincent

    2015-01-01

    In metazoans, the Wnt signaling pathway plays a key role in the regulation of binary decisions during development. During this process different sets of target genes are activated in cells where the Wnt pathway is active (classic target genes) versus cells where the pathway is inactive (opposite target genes). While the mechanism of transcriptional activation is well understood for classic target genes, how opposite target genes are activated in the absence of Wnt remains poorly characterized. Here we discuss how the key transcriptional mediator of the Wnt pathway, the TCF family member POP-1, regulates opposite target genes during C. elegans development. We examine recent findings suggesting that the direction of the transcriptional output (activation or repression) can be determined by the way TCF is recruited and physically interacts with its target gene. PMID:27123368

  14. Retrotransposon activation followed by rapid repression in introgressed rice plants.

    PubMed

    Liu, B; Wendel, J F

    2000-10-01

    Plant retrotransposons are largely inactive during normal development, but may be activated by stresses. Both copia-like and gypsy-like retrotransposons of rice were activated by introgression of DNA from the wild species Zizania latifolia Griseb. The copy number increase was associated with cytosine methylation changes of the elements. Activity of the elements was ephemeral, as evidenced by nearly identical genomic Southern hybridization patterns among randomly chosen individuals both within and between generations for a given line, and the absence of transcripts based on Northern analysis. DNA hypermethylation, internal sequence deletion, and possibly other mechanisms are likely responsible for the rapid element repression. Implications of the retroelement dynamics on plant genome evolution are discussed. PMID:11081978

  15. The role of COP1 in repression of photoperiodic flowering.

    PubMed

    Xu, Dongqing; Zhu, Danmeng; Deng, Xing Wang

    2016-01-01

    Plants use the circadian clock as a timekeeping mechanism to regulate photoperiodic flowering in response to the seasonal changes. CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1), initially identified as a central repressor of seedling photomorphogenesis, was recently shown to be involved in the regulation of light input to the circadian clock, modulating the circadian rhythm and flowering. COP1 encodes a RING-finger E3 ubiquitin ligase and works in concert with SUPPRESSOR of phyA-105 (SPA) proteins to repress photoperiodic flowering by regulating proteasome-mediated degradation of CONSTANS (CO), a central regulator of photoperiodic flowering. In addition, COP1 and EARLY FLOWERING 3 (ELF3) indirectly modulate CO expression via the degradation of GIGANTEA (GI). Here, we summarize the current understanding of the molecular mechanisms underlying COP1's role in controlling of photoperiodic flowering. PMID:26949521

  16. Repression and splitting: towards a method of conceptual comparison.

    PubMed

    Hinshelwood, R D

    2008-06-01

    An attempt is made to compare two psychoanalytic concepts which by 'belonging' to different psychoanalytic groups have come to be defined and used differently. The paper is also an inquiry into the possibility of a comparative psychoanalytic method. The two concepts are 'repression' and 'splitting of the ego' and an examination is made of the semantic similarities and differences. Some clinical material is offered that adds indicative clinical evidence to test the semantic comparison. The aim is to answer the question: Are the terms simply alternative ones for similar clinical phenomena? The paper offers one method which could provide an answer. It represents a general method for clarifying and maybe reconciling the differing points of view of competing psychoanalytic schools. PMID:18558953

  17. Novel TCF-binding sites specify transcriptional repression by Wnt signalling

    PubMed Central

    Blauwkamp, Timothy A; Chang, Mikyung V; Cadigan, Ken M

    2008-01-01

    Both transcriptional activation and repression have essential functions in maintaining proper spatial and temporal control of gene expression. Although Wnt signalling is often associated with gene activation, we have identified several directly repressed targets of Wnt signalling in Drosophila. Here, we explore how individual Wnt target genes are specified for signal-induced activation or repression. Similar to activation, repression required binding of Armadillo (Arm) to the N terminus of TCF. However, TCF/Arm mediated repression by binding to DNA motifs that are markedly different from typical TCF-binding sites. Conversion of the novel motifs to standard TCF-binding sites reversed the mode of regulation, resulting in Wnt-mediated activation instead of repression. A mutant form of Arm defective in activation was still functional for repression, indicating that distinct domains of the protein are required for each activity. This study suggests that the sequence of TCF-binding sites allosterically regulates the TCF/Arm complex to effect either transcriptional activation or repression. PMID:18418383

  18. Novel TCF-binding sites specify transcriptional repression by Wnt signalling.

    PubMed

    Blauwkamp, Timothy A; Chang, Mikyung V; Cadigan, Ken M

    2008-05-21

    Both transcriptional activation and repression have essential functions in maintaining proper spatial and temporal control of gene expression. Although Wnt signalling is often associated with gene activation, we have identified several directly repressed targets of Wnt signalling in Drosophila. Here, we explore how individual Wnt target genes are specified for signal-induced activation or repression. Similar to activation, repression required binding of Armadillo (Arm) to the N terminus of TCF. However, TCF/Arm mediated repression by binding to DNA motifs that are markedly different from typical TCF-binding sites. Conversion of the novel motifs to standard TCF-binding sites reversed the mode of regulation, resulting in Wnt-mediated activation instead of repression. A mutant form of Arm defective in activation was still functional for repression, indicating that distinct domains of the protein are required for each activity. This study suggests that the sequence of TCF-binding sites allosterically regulates the TCF/Arm complex to effect either transcriptional activation or repression. PMID:18418383

  19. Repressive Coping, Emotional Adjustment, and Cognition in People Who Have Lost Loved Ones to Suicide

    ERIC Educational Resources Information Center

    Parker, Holly A.; McNally, Richard J.

    2008-01-01

    Research indicates that a repressive coping style is psychologically protective against the stress of trauma, yet it is unclear whether this finding generalizes to suicide bereavement. Thus, we assessed cognitive ability and mental health among individuals who lost a loved one to suicide. The results indicate that repressive coping may be…

  20. Removal of DELLA repression promotes leaf senescence in Arabidopsis.

    PubMed

    Chen, Mingxun; Maodzeka, Antony; Zhou, Longhua; Ali, Essa; Wang, Zhong; Jiang, Lixi

    2014-04-01

    Leaf senescence is an integrated response of leaf cells to developmental age and various internal and environmental signals. However, the role of gibberellins (GA) in leaf senescence is not clear. In the current study, we investigated the effect of DELLA on leaf senescence. Compared with the wild type (WT), leaf senescence occurred earlier in the mutant ga1-3 gai-t6 rga-t2 rgl1-1 rgl2-1 (abbreviated as Q-DELLA/ga1-3) whose DELLA repression was removed, whereas leaf senescence was retarded in the mutant ga1-3 whose GA biosynthesis was blocked and whose DELLA proteins accumulated abnormally. During leaf senescence, SAG12 and SAG29 were upregulated in Q-DELLA/ga1-3 and downregulated in ga1-3 plants. The Q-DELLA/ga1-3 senescent leaves contained more sugar but less chlorophyll and fatty acids (FAs) than those of ga1-3 and WT. Both absolute and relative contents of C18:3 in Q-DELLA/ga1-3 senescent leaves were lower compared with those of the WT and ga1-3 leaves. The genes regulating FA β-oxidation in Q-DELLA/ga1-3, such as KAT2, LACS6, LACS7, ACX1, ACX2 and MAP2, were significantly upregulated. The removal of DELLA repression highly upregulated certain genes on various hormone pathways, suggesting that GA signaling acts upstream of the jasmonic acid, salicylic acid, and ethylene pathways in regulating leaf senescence. PMID:24576761

  1. Conserved intron elements repress splicing of a neuron-specific c-src exon in vitro.

    PubMed Central

    Chan, R C; Black, D L

    1995-01-01

    The neuron-specific N1 exon of the mouse c-src transcript is normally skipped in nonneuronal cells. In this study, we examined the sequence requirements for the exclusion of this exon in nonneuronal HeLa cell nuclear extracts. We found that the repression of the N1 exon is mediated by specific intron sequences that flank the N1 exon. Mutagenesis experiments identified conserved CUCUCU elements within these intron regions that are required for the repression of N1 splicing. The addition of an RNA competitor containing the upstream regulatory sequence to the HeLa extract induced splicing of the intron downstream of N1, indicating that the competitor sequence binds to splicing repressor proteins. The similarities between this mechanism for src splicing repression and the repression of other regulated exons point to a common role of exon-spanning interactions in splicing repression. PMID:7565790

  2. MYC-repressed long noncoding RNAs antagonize MYC-induced cell proliferation and cell cycle progression

    PubMed Central

    Jeon, Young-Jun; Fadda, Paolo; Alder, Hansjuerg; Croce, Carlo M.

    2015-01-01

    The transcription factor MYC is a proto-oncogene regulating cell proliferation, cell cycle, apoptosis and metabolism. The recent identification of MYC-regulated long noncoding RNAs (lncRNAs) expands our knowledge of the role of lncRNAs in MYC functions. Here, we identify MYC-repressed lncRNAs named MYCLo-4, -5 and -6 by comparing 3 categories of lncRNAs (downregulated in highly MYC-expressing colorectal cancer, up-regulated by MYC knockdown in HCT116, upregulated by MYC knockdown in RKO). The MYC-repressed MYCLos are implicated in MYC-modulated cell proliferation through cell cycle regulation. By screening cell cycle-related genes regulated by MYC and the MYC-repressed MYCLos, we identified the MYC-repressed gene GADD45A as a target gene of the MYC-repressed MYCLos such as MYCLo-4 and MYCLo-6. PMID:26003165

  3. MCRS2 represses the transactivation activities of Nrf1

    PubMed Central

    Wu, Jia-Long; Lin, Young-Sun; Yang, Chi-Chiang; Lin, Yu-Jen; Wu, Shan-Fu; Lin, Ying-Ting; Huang, Chien-Fu

    2009-01-01

    in the redistribution of Nrf1. This suggested the existence of Nrf1-MCRS2 complex in vivo. To further confirm the biological function, a reporter driven by CNC-bZIP protein binding sites was also shown to be repressed by MCRS2 in a transient transfection assay. An artificial reporter gene activated by LexA-Nrf1 was also specifically repressed by MCRS2. Conclusion From the results, we showed MCRS2, a new Nrf1-interacting protein, has a repression effect on Nrf1-mediated transcriptional activation. This was the first ever identified repressor protein related to Nrf1 transactivation. PMID:19187526

  4. Cloning of a DNA fragment encoding a heme-repressible hemoglobin-binding outer membrane protein from Haemophilus influenzae.

    PubMed Central

    Jin, H; Ren, Z; Pozsgay, J M; Elkins, C; Whitby, P W; Morton, D J; Stull, T L

    1996-01-01

    Haemophilus influenzae is able to use hemoglobin as a sole source of heme, and heme-repressible hemoglobin binding to the cell surface has been demonstrated. Using an affinity purification methodology, a hemoglobin-binding protein of approximately 120 kDa was isolated from H. influenzae type b strain HI689 grown in heme-restricted but not in heme-replete conditions. The isolated protein was subjected to N-terminal amino acid sequencing, and the derived amino acid sequence was used to design corresponding oligonucleotides. The oligonucleotides were used to probe a Southern blot of EcoRI-digested HI689 genomic DNA. A hybridizing band of approximately 4.2 kb was successfully cloned into pUC19. Using a 1.9-kb internal BglII fragment of the 4.2-kb clone as a probe, hybridization was seen in both typeable and nontypeable H. influenzae but not in other bacterial species tested. Following partial nucleotide sequencing of the 4.2-kb insert, a putative open reading frame was subcloned into an expression vector. The host Escherichia coli strain in which the cloned fragment was expressed bound biotinylated human hemoglobin, whereas binding of hemoglobin was not detected in E. coli with the vector alone. In conclusion, we hypothesize that the DNA fragment encoding an approximately 120-kDa heme-repressible hemoglobin-binding protein mediates one step in the acquisition of hemoglobin by H. influenzae in vivo. PMID:8757844

  5. Political Repression Against Soviet Astronomers in the 1930s

    NASA Astrophysics Data System (ADS)

    Eremmeva, A. I.

    1993-12-01

    The Soviet government's repression of the Russian intelligentsia in the late 1930s had a devastating effect on astronomy. This period was marked by the strengthening of a rigid ideology in society and a growing atmosphere of suspicion, fear, and spy mania. Under these conditions the international nature of astronomy--in particular the need for foreign contacts--became the excuse for accusations of "wrecking" against astronomers. The fate of individual astronomers and institutions depended greatly, however, on local circumstances. For example, the general political repression of the 1930s began in Leningrad at a time when Pulkovo Observatory director B. P. Gerasimovich was engaged in a sharp conflict with a small group of junior staff led by V. A. Ambartsumian. In addition, the very first arrest of a Leningrad astronomer--namely the arrest of B. V. Numerov--appears to have initiated a cascading series of arrests that spread like an avalanche through the close-knit com- munity of Leningrad astronomers. These two factors led to the devastating ruin of Pulkovo. Completely different circumstances saved GAISh. This was a com- paratively young institute whose junior staff had spent its formative years at GAISh rather than joining the staff from out- side (as had been the case at Pulkovo). Thus the GAISh staff had a greater degree of homogeneity and solidarity, and this, in turn, may explain why the ideological department at GAISh (the "partburo") conducted itself in a manner that differed sharply from that of the "partburo" at Pulkovo. Thanks to these circum- stances not even one arrest occurred at GAISh. The directors of Pulkovo and GAISh came from very similar back- grounds, but the different conditions at Pulkovo and GAISh led to dramatic differences in their fates: execution for B. P. Gerasimovich in 1937 and "only" the persecution of GAISh director V. G. Fesenkov. The persecution of V. G. Fesenkov included his dismissal from the post of chairman of the Astronomical

  6. Selective repression of transcriptional activators at a distance by the Drosophila Krüppel protein.

    PubMed Central

    Licht, J D; Ro, M; English, M A; Grossel, M; Hansen, U

    1993-01-01

    The Krüppel (Kr) protein, bound at kilobase distances from the start site of transcription, represses transcription by RNA polymerase II in mammalian cells. Repression is monotonically dependent on the dose of Kr protein and the presence of Kr binding site(s) on the DNA. These data suggest an inhibitory protein-protein interaction between the Kr protein and proximal transcription factors. Repression by Kr depends on the specific activator protein driving transcription. In particular, Kr protein selectively represses transcription mediated by the Sp1 glutamine-rich activation domain, tethered to the promoter by a GAL4 DNA-binding domain, but does not repress transcription stimulated by the acidic GAL4 activator. We believe this represents repression by a quenching interaction between DNA-bound Kr protein and the activation region of Sp1, rather than competition between Sp1 and Kr for a limiting transcriptional component. Selective, context-related repression affords an added layer of combinatorial control of gene expression by sequence-specific transcription factors. Images Fig. 1 Fig. 4 PMID:8248254

  7. The gap protein knirps mediates both quenching and direct repression in the Drosophila embryo.

    PubMed Central

    Arnosti, D N; Gray, S; Barolo, S; Zhou, J; Levine, M

    1996-01-01

    Transcriptional repression is essential for establishing localized patterns of gene expression during Drosophila embryogenesis. Several mechanisms of repression have been proposed, including competition, quenching and direct repression of the transcription complex. Previous studies suggest that the knirps orphan receptor (kni) may repress transcription via competition, and exclude the binding of the bicoid (bcd) activator to an overlapping site in a target promoter. Here we present evidence that kni can quench, or locally inhibit, upstream activators within a heterologous enhancer in transgenic embryos. The range of kni repression is approximately 50-100 bp, so that neighboring enhancers in a modular promoter are free to interact with the transcription complex (enhancer autonomy). However, kni can also repress the transcription complex when bound in promoter-proximal regions. In this position, kni functions as a dominant repressor and blocks multiple enhancers in a modular promoter. Our studies suggest that short-range repression represents a flexible form of gene regulation, exhibiting enhancer- or promoter-specific effects depending on the location of repressor binding sites. Images PMID:8670869

  8. Natural Memory Beyond the Storage Model: Repression, Trauma, and the Construction of a Personal Past

    PubMed Central

    Axmacher, Nikolai; Do Lam, Anne T. A.; Kessler, Henrik; Fell, Juergen

    2010-01-01

    Naturally occurring memory processes show features which are difficult to investigate by conventional cognitive neuroscience paradigms. Distortions of memory for problematic contents are described both by psychoanalysis (internal conflicts) and research on post-traumatic stress disorder (PTSD; external traumata). Typically, declarative memory for these contents is impaired – possibly due to repression in the case of internal conflicts or due to dissociation in the case of external traumata – but they continue to exert an unconscious pathological influence: neurotic symptoms or psychosomatic disorders after repression or flashbacks and intrusions in PTSD after dissociation. Several experimental paradigms aim at investigating repression in healthy control subjects. We argue that these paradigms do not adequately operationalize the clinical process of repression, because they rely on an intentional inhibition of random stimuli (suppression). Furthermore, these paradigms ignore that memory distortions due to repression or dissociation are most accurately characterized by a lack of self-referential processing, resulting in an impaired integration of these contents into the self. This aspect of repression and dissociation cannot be captured by the concept of memory as a storage device which is usually employed in the cognitive neurosciences. It can only be assessed within the framework of a constructivist memory concept, according to which successful memory involves a reconstruction of experiences such that they fit into a representation of the self. We suggest several experimental paradigms that allow for the investigation of the neural correlates of repressed memories and trauma-induced memory distortions based on a constructivist memory concept. PMID:21151366

  9. Synergistic release from glucose repression by mig1 and ssn mutations in Saccharomyces cerevisiae.

    PubMed

    Vallier, L G; Carlson, M

    1994-05-01

    In the yeast Saccharomyces cerevisiae, glucose repression of SUC2 transcription requires the SSN6-TUP1 repressor complex. It has been proposed that the DNA-binding protein MIG1 secures SSN6-TUP1 to the SUC2 promoter. Here we show that a mig1 deletion does not cause nearly as dramatic a loss of repression as ssn6: glucose-grown mig1 mutants display 20-fold lower SUC2 expression than ssn6 mutants. Thus, repression by SSN6-TUP1 is not mediated solely by MIG1, but also involves MIG1-independent mechanisms. We report that mig1 partially restores SUC2 expression in mutants lacking the SNF1 protein kinase and show that mig1 is allelic to ssn1, a mutation selected as a suppressor of snf1. Other SSN genes identified in this selection were therefore candidates for a role in repression of SUC2. We show that mig1 acts synergistically with ssn2 through ssn5, ssn7, and ssn8 to relieve glucose repression of SUC2 and to suppress the requirement for SNF1. These findings indicate that the SSN proteins contribute to repression of SUC2, and the pleiotropic phenotypes of the ssn mutants suggest global roles in repression. Finally, the regulated SUC2 expression observed in snf1 mig1 mutants indicates that signals regarding glucose availability can be transmitted independently of the SNF1 protein kinase.

  10. Repressive coping, stigmatization, psychological distress, and quality of life among behavioral weight management participants.

    PubMed

    Truong, Erin A K; Olson, KayLoni L; Emery, Charles F

    2016-08-01

    Repressive coping has been associated with elevated risk of disease and negative health outcomes in past studies. Although a prior study of healthy men found that repression was associated with lower body mass index (BMI), no study has examined repressive coping among obese individuals. This study examined the relationship of repressive coping with BMI and obesity-relevant psychosocial factors among 104 overweight and obese participants in a behavioral weight management program. Participants completed questionnaires assessing repressive coping, stigmatization, psychological distress, and quality of life. BMI was objectively measured. Repressors reported lower stigmatization, anxiety, and depression as well as higher emotional and weight-related quality of life. Repressors and non-repressors had equivalent BMI and reported similar impairment in physical quality of life, but stigmatization moderated the relationship between repressive coping and physical quality of life (b=0.31, p=0.039), reflecting better physical quality of life among non-repressors with lower stigmatization. Obese individuals who engage in repressive coping may tend to underreport psychological symptoms, social difficulties, and impairments in quality of life. Higher physical quality of life among non-repressors with lower stigmatization may reflect a combined influence of coping and social processes in physical quality of life among obese individuals. PMID:27304361

  11. Repressive coping, stigmatization, psychological distress, and quality of life among behavioral weight management participants.

    PubMed

    Truong, Erin A K; Olson, KayLoni L; Emery, Charles F

    2016-08-01

    Repressive coping has been associated with elevated risk of disease and negative health outcomes in past studies. Although a prior study of healthy men found that repression was associated with lower body mass index (BMI), no study has examined repressive coping among obese individuals. This study examined the relationship of repressive coping with BMI and obesity-relevant psychosocial factors among 104 overweight and obese participants in a behavioral weight management program. Participants completed questionnaires assessing repressive coping, stigmatization, psychological distress, and quality of life. BMI was objectively measured. Repressors reported lower stigmatization, anxiety, and depression as well as higher emotional and weight-related quality of life. Repressors and non-repressors had equivalent BMI and reported similar impairment in physical quality of life, but stigmatization moderated the relationship between repressive coping and physical quality of life (b=0.31, p=0.039), reflecting better physical quality of life among non-repressors with lower stigmatization. Obese individuals who engage in repressive coping may tend to underreport psychological symptoms, social difficulties, and impairments in quality of life. Higher physical quality of life among non-repressors with lower stigmatization may reflect a combined influence of coping and social processes in physical quality of life among obese individuals.

  12. Hepatocyte-Ductal Transdifferentiation Is Mediated by Reciprocal Repression of SOX9 and C/EBPα

    PubMed Central

    O'Neill, Kathy E.; Thowfeequ, Shifaan; Li, Wan-Chun; Eberhard, Daniel; Dutton, James R.; Slack, Jonathan M.W.

    2014-01-01

    Abstract Primary hepatocytes rapidly dedifferentiate when cultured in vitro. We have studied the mechanism of hepatocyte dedifferentiation by using two culture media: one that maintains hepatocytes in a differentiated state and another that allows dedifferentiation. We show that dedifferentiation involves partial transformation of hepatocytes into cells that resemble biliary epithelial cells. Lineage labeling and time-lapse filming confirm that the dedifferentiated cells are derived from hepatocytes and not from contaminating ductal or fibroblastic cells in the original culture. Furthermore, we establish that the conversion of hepatocytes to biliary-like cells is regulated by mutual antagonism of CCAAT/enhancer binding protein alpha (C/EBPα) and SOX9, which have opposing effects on the expression of hepatocyte and ductal genes. Thus, hepatocyte dedifferentiation induces the biliary gene expression program by alleviating C/EBPα-mediated repression of Sox9. We propose that reciprocal antagonism of C/EBPα and SOX9 also operates in the formation of hepatocytes and biliary ducts from hepatoblasts during normal embryonic development. These data demonstrate that reprogramming of differentiated cells can be used to model the acquisition and maintenance of cell fate in vivo. PMID:25153359

  13. A cellular chemical probe targeting the chromodomains of Polycomb Repressive Complex 1

    PubMed Central

    Stuckey, Jacob I; Dickson, Bradley M; Cheng, Nancy; Liu, Yanli; Norris, Jacqueline L; Cholensky, Stephanie H; Tempel, Wolfram; Qin, Su; Huber, Katherine G; Sagum, Cari; Black, Karynne; Li, Fengling; Huang, Xi-Ping; Roth, Bryan L; Baughman, Brandi M; Senisterra, Guillermo; Pattenden, Samantha G; Vedadi, Masoud; Brown, Peter J; Bedford, Mark T; Min, Jinrong; Arrowsmith, Cheryl H

    2015-01-01

    We report the design and characterization of UNC3866, a potent antagonist of the methyl-lysine (Kme) reading function of the Polycomb CBX and CDY families of chromodomains. Polycomb CBX proteins regulate gene expression by targeting Polycomb Repressive Complex 1 to sites of H3K27me3 via their chromodomains. UNC3866 binds the chromodomains of CBX4 and CBX7 most potently with a Kd of ∼100 nM for each, and is 6- to 18-fold selective versus seven other CBX and CDY chromodomains while being highly selective versus >250 other protein targets. X-ray crystallography revealed that UNC3866 closely mimics the interactions of the methylated H3 tail with these chromodomains. UNC4195, a biotinylated derivative of UNC3866, was used to demonstrate that UNC3866 engages intact PRC1 and that EED incorporation into PRC1 is isoform-dependent in PC3 prostate cancer cells. Finally, UNC3866 inhibits PC3 cell proliferation, a known CBX7 phenotype, while UNC4219, a methylated negative control compound, has negligible effects. PMID:26807715

  14. Two distinct repressive mechanisms for histone 3 lysine 4 methylation through promoting 3'-end antisense transcription.

    PubMed

    Margaritis, Thanasis; Oreal, Vincent; Brabers, Nathalie; Maestroni, Laetitia; Vitaliano-Prunier, Adeline; Benschop, Joris J; van Hooff, Sander; van Leenen, Dik; Dargemont, Catherine; Géli, Vincent; Holstege, Frank C P

    2012-09-01

    Histone H3 di- and trimethylation on lysine 4 are major chromatin marks that correlate with active transcription. The influence of these modifications on transcription itself is, however, poorly understood. We have investigated the roles of H3K4 methylation in Saccharomyces cerevisiae by determining genome-wide expression-profiles of mutants in the Set1 complex, COMPASS, that lays down these marks. Loss of H3K4 trimethylation has virtually no effect on steady-state or dynamically-changing mRNA levels. Combined loss of H3K4 tri- and dimethylation results in steady-state mRNA upregulation and delays in the repression kinetics of specific groups of genes. COMPASS-repressed genes have distinct H3K4 methylation patterns, with enrichment of H3K4me3 at the 3'-end, indicating that repression is coupled to 3'-end antisense transcription. Further analyses reveal that repression is mediated by H3K4me3-dependent 3'-end antisense transcription in two ways. For a small group of genes including PHO84, repression is mediated by a previously reported trans-effect that requires the antisense transcript itself. For the majority of COMPASS-repressed genes, however, it is the process of 3'-end antisense transcription itself that is the important factor for repression. Strand-specific qPCR analyses of various mutants indicate that this more prevalent mechanism of COMPASS-mediated repression requires H3K4me3-dependent 3'-end antisense transcription to lay down H3K4me2, which seems to serve as the actual repressive mark. Removal of the 3'-end antisense promoter also results in derepression of sense transcription and renders sense transcription insensitive to the additional loss of SET1. The derepression observed in COMPASS mutants is mimicked by reduction of global histone H3 and H4 levels, suggesting that the H3K4me2 repressive effect is linked to establishment of a repressive chromatin structure. These results indicate that in S. cerevisiae, the non-redundant role of H3K4 methylation by

  15. Role of sugar uptake and metabolic intermediates on catabolite repression in Bacillus subtilis.

    PubMed Central

    Lopez, J M; Thoms, B

    1977-01-01

    Many phosphorylated intermediates exert catabolite repression on the enzyme acetoin dehydrogenase in Bacillus subtilis. This was shown with strains that are blocked at different positions in central metabolism when they receive sugars that cannot be metabolized past enzymatic block(s). In the case of sorbitol, transport events were not involved in catabolite repression, for this sugar cannot repress acetoin dehydrogenase in a strain lacking sorbitol dehydrogenase but otherwise able to take up sorbitol. The presence of glucose did not markedly influence the uptake of acetoin. PMID:401492

  16. Autoregulation of fos: the dyad symmetry element as the major target of repression.

    PubMed Central

    König, H; Ponta, H; Rahmsdorf, U; Büscher, M; Schönthal, A; Rahmsdorf, H J; Herrlich, P

    1989-01-01

    Fos and Jun co-operatively repress the fos promoter. Removal of all putative Fos/Jun binding sites from the fos promoter neither obliterates the repression by Fos/Jun in transient cotransfection experiments in NIH3T3 cells nor the turn-off kinetics of serum-induced fos expression in stably transfected NIH3T3 cells. The dyad symmetry element (DSE) suffices to subject a promoter to this type of repression. However, one of the putative Fos/Jun binding sites (-292 to -299 and thus located immediately adjacent to the DSE), determines the very low level of basal expression. Images PMID:2511006

  17. MicroRNA-125b promotes neuronal differentiation in human cells by repressing multiple targets.

    PubMed

    Le, Minh T N; Xie, Huangming; Zhou, Beiyan; Chia, Poh Hui; Rizk, Pamela; Um, Moonkyoung; Udolph, Gerald; Yang, Henry; Lim, Bing; Lodish, Harvey F

    2009-10-01

    MicroRNAs (miRNAs) are a class of small noncoding RNAs that regulate gene expression at the posttranscriptional level. Research on miRNAs has highlighted their importance in neural development, but the specific functions of neurally enriched miRNAs remain poorly understood. We report here the expression profile of miRNAs during neuronal differentiation in the human neuroblastoma cell line SH-SY5Y. Six miRNAs were significantly upregulated during differentiation induced by all-trans-retinoic acid and brain-derived neurotrophic factor. We demonstrated that the ectopic expression of either miR-124a or miR-125b increases the percentage of differentiated SH-SY5Y cells with neurite outgrowth. Subsequently, we focused our functional analysis on miR-125b and demonstrated the important role of this miRNA in both the spontaneous and induced differentiations of SH-SH5Y cells. miR-125b is also upregulated during the differentiation of human neural progenitor ReNcell VM cells, and miR-125b ectopic expression significantly promotes the neurite outgrowth of these cells. To identify the targets of miR-125b regulation, we profiled the global changes in gene expression following miR-125b ectopic expression in SH-SY5Y cells. miR-125b represses 164 genes that contain the seed match sequence of the miRNA and/or that are predicted to be direct targets of miR-125b by conventional methods. Pathway analysis suggests that a subset of miR-125b-repressed targets antagonizes neuronal genes in several neurogenic pathways, thereby mediating the positive effect of miR-125b on neuronal differentiation. We have further validated the binding of miR-125b to the miRNA response elements of 10 selected mRNA targets. Together, we report here for the first time the important role of miR-125b in human neuronal differentiation.

  18. REST represses a subset of the pancreatic endocrine differentiation program.

    PubMed

    Martin, David; Kim, Yung-Hae; Sever, Dror; Mao, Chai-An; Haefliger, Jacques-Antoine; Grapin-Botton, Anne

    2015-09-15

    To contribute to devise successful beta-cell differentiation strategies for the cure of Type 1 diabetes we sought to uncover barriers that restrict endocrine fate acquisition by studying the role of the transcriptional repressor REST in the developing pancreas. Rest expression is prevented in neurons and in endocrine cells, which is necessary for their normal function. During development, REST represses a subset of genes in the neuronal differentiation program and Rest is down-regulated as neurons differentiate. Here, we investigate the role of REST in the differentiation of pancreatic endocrine cells, which are molecularly close to neurons. We show that Rest is widely expressed in pancreas progenitors and that it is down-regulated in differentiated endocrine cells. Sustained expression of REST in Pdx1(+) progenitors impairs the differentiation of endocrine-committed Neurog3(+) progenitors, decreases beta and alpha cell mass by E18.5, and triggers diabetes in adulthood. Conditional inactivation of Rest in Pdx1(+) progenitors is not sufficient to trigger endocrine differentiation but up-regulates a subset of differentiation genes. Our results show that the transcriptional repressor REST is active in pancreas progenitors where it gates the activation of part of the beta cell differentiation program. PMID:26156633

  19. REST represses a subset of the pancreatic endocrine differentiation program

    PubMed Central

    Martin, David; Kim, Yung-Hae; Sever, Dror; Mao, Chai-An; Haefiiger, Jacques-Antoine; Grapin-Botton, Anne

    2016-01-01

    To contribute to devise successful beta-cell differentiation strategies for the cure of Type 1 diabetes we sought to uncover barriers that restrict endocrine fate acquisition by studying the role of the transcriptional repressor REST in the developing pancreas. Rest expression is prevented in neurons and in endocrine cells, which is necessary for their normal function. During development, REST represses a subset of genes in the neuronal differentiation program and Rest is down-regulated as neurons differentiate. Here, we investigate the role of REST in the differentiation of pancreatic endocrine cells, which are molecularly close to neurons. We show that Rest is widely expressed in pancreas progenitors and that it is down-regulated in differentiated endocrine cells. Sustained expression of REST in Pdx1+ progenitors impairs the differentiation of endocrine-committed Neurog3+ progenitors, decreases beta and alpha cell mass by E18.5, and triggers diabetes in adulthood. Conditional inactivation of Rest in Pdx1+ progenitors is not sufficient to trigger endocrine differentiation but up-regulates a subset of differentiation genes. Our results show that the transcriptional repressor REST is active in pancreas progenitors where it gates the activation of part of the beta cell differentiation program. PMID:26156633

  20. Epigenetic dysregulation by nickel through repressive chromatin domain disruption.

    PubMed

    Jose, Cynthia C; Xu, Beisi; Jagannathan, Lakshmanan; Trac, Candi; Mallela, Ramya K; Hattori, Takamitsu; Lai, Darson; Koide, Shohei; Schones, Dustin E; Cuddapah, Suresh

    2014-10-01

    Investigations into the genomic landscape of histone modifications in heterochromatic regions have revealed histone H3 lysine 9 dimethylation (H3K9me2) to be important for differentiation and maintaining cell identity. H3K9me2 is associated with gene silencing and is organized into large repressive domains that exist in close proximity to active genes, indicating the importance of maintenance of proper domain structure. Here we show that nickel, a nonmutagenic environmental carcinogen, disrupted H3K9me2 domains, resulting in the spreading of H3K9me2 into active regions, which was associated with gene silencing. We found weak CCCTC-binding factor (CTCF)-binding sites and reduced CTCF binding at the Ni-disrupted H3K9me2 domain boundaries, suggesting a loss of CTCF-mediated insulation function as a potential reason for domain disruption and spreading. We furthermore show that euchromatin islands, local regions of active chromatin within large H3K9me2 domains, can protect genes from H3K9me2-spreading-associated gene silencing. These results have major implications in understanding H3K9me2 dynamics and the consequences of chromatin domain disruption during pathogenesis. PMID:25246589

  1. REST represses a subset of the pancreatic endocrine differentiation program.

    PubMed

    Martin, David; Kim, Yung-Hae; Sever, Dror; Mao, Chai-An; Haefliger, Jacques-Antoine; Grapin-Botton, Anne

    2015-09-15

    To contribute to devise successful beta-cell differentiation strategies for the cure of Type 1 diabetes we sought to uncover barriers that restrict endocrine fate acquisition by studying the role of the transcriptional repressor REST in the developing pancreas. Rest expression is prevented in neurons and in endocrine cells, which is necessary for their normal function. During development, REST represses a subset of genes in the neuronal differentiation program and Rest is down-regulated as neurons differentiate. Here, we investigate the role of REST in the differentiation of pancreatic endocrine cells, which are molecularly close to neurons. We show that Rest is widely expressed in pancreas progenitors and that it is down-regulated in differentiated endocrine cells. Sustained expression of REST in Pdx1(+) progenitors impairs the differentiation of endocrine-committed Neurog3(+) progenitors, decreases beta and alpha cell mass by E18.5, and triggers diabetes in adulthood. Conditional inactivation of Rest in Pdx1(+) progenitors is not sufficient to trigger endocrine differentiation but up-regulates a subset of differentiation genes. Our results show that the transcriptional repressor REST is active in pancreas progenitors where it gates the activation of part of the beta cell differentiation program.

  2. Promoter DNA Hypermethylation and Gene Repression in Undifferentiated Arabidopsis Cells

    PubMed Central

    Berdasco, María; Alcázar, Rubén; García-Ortiz, María Victoria; Ballestar, Esteban; Fernández, Agustín F.; Roldán-Arjona, Teresa; Tiburcio, Antonio F.; Altabella, Teresa; Buisine, Nicolas; Quesneville, Hadi; Baudry, Antoine; Lepiniec, Loïc; Alaminos, Miguel; Rodríguez, Roberto; Lloyd, Alan; Colot, Vincent; Bender, Judith; Canal, María Jesús; Esteller, Manel; Fraga, Mario F.

    2008-01-01

    Maintaining and acquiring the pluripotent cell state in plants is critical to tissue regeneration and vegetative multiplication. Histone-based epigenetic mechanisms are important for regulating this undifferentiated state. Here we report the use of genetic and pharmacological experimental approaches to show that Arabidopsis cell suspensions and calluses specifically repress some genes as a result of promoter DNA hypermethylation. We found that promoters of the MAPK12, GSTU10 and BXL1 genes become hypermethylated in callus cells and that hypermethylation also affects the TTG1, GSTF5, SUVH8, fimbrin and CCD7 genes in cell suspensions. Promoter hypermethylation in undifferentiated cells was associated with histone hypoacetylation and primarily occurred at CpG sites. Accordingly, we found that the process specifically depends on MET1 and DRM2 methyltransferases, as demonstrated with DNA methyltransferase mutants. Our results suggest that promoter DNA methylation may be another important epigenetic mechanism for the establishment and/or maintenance of the undifferentiated state in plant cells. PMID:18827894

  3. Repression of the albumin gene in Novikoff hepatoma cells

    SciTech Connect

    Capetanaki, Y.G.; Flytzanis, C.N.; Alonso, A.

    1982-03-01

    Novikoff hepatoma cells have lost their capacity to synthesize albumin. As a first approach to study the mechanisms underlying this event, in vitro translation in a reticulocyte system was performed using total polyadenylated mRNA from rat liver and Novikoff hepatoma cells. Immunoprecipitation of the in vitro translation products with albumin-specific antibody revealed a total lack of albumin synthesis in Novikoff hepatoma, suggesting the absence of functional albumin mRNA in these cells. Titration experiments using as probe albumin cDNA cloned in pBR322 plasmid demonstrated the absence of albumin-specific sequences in both polysomal and nuclear polyadenylated and total RNA from Novikoff cells. This albumin recombinant plasmid was obtained by screening a rat liver cDNA library with albumin (/sup 32/P)cDNA reverse transcribed from immuno-precipitated mRNA. The presence of an albumin-specific gene insert was documented with translation assays as well as by restriction mapping. Repression of the albumin gene at the transcriptional level was further demonstrated by RNA blotting experiments using the cloned albumin cDNA probe. Genomic DNA blots using the cloned albumin cDNA as probe did not reveal any large-scale deletions, insertions, or rearrangements in the albumin gene, suggesting that the processes involved in the suppression of albumin mRNA synthesis do not involve extensive genomic rearrangements.

  4. LATS2 Positively Regulates Polycomb Repressive Complex 2.

    PubMed

    Torigata, Kosuke; Daisuke, Okuzaki; Mukai, Satomi; Hatanaka, Akira; Ohka, Fumiharu; Motooka, Daisuke; Nakamura, Shota; Ohkawa, Yasuyuki; Yabuta, Norikazu; Kondo, Yutaka; Nojima, Hiroshi

    2016-01-01

    LATS2, a pivotal Ser/Thr kinase of the Hippo pathway, plays important roles in many biological processes. LATS2 also function in Hippo-independent pathway, including mitosis, DNA damage response and epithelial to mesenchymal transition. However, the physiological relevance and molecular basis of these LATS2 functions remain obscure. To understand novel functions of LATS2, we constructed a LATS2 knockout HeLa-S3 cell line using TAL-effector nuclease (TALEN). Integrated omics profiling of this cell line revealed that LATS2 knockout caused genome-wide downregulation of Polycomb repressive complex 2 (PRC2) and H3K27me3. Cell-cycle analysis revealed that downregulation of PRC2 was not due to cell cycle aberrations caused by LATS2 knockout. Not LATS1, a homolog of LATS2, but LATS2 bound PRC2 on chromatin and phosphorylated it. LATS2 positively regulates histone methyltransferase activity of PRC2 and their expression at both the mRNA and protein levels. Our findings reveal a novel signal upstream of PRC2, and provide insight into the crucial role of LATS2 in coordinating the epigenome through regulation of PRC2. PMID:27434182

  5. Andrei Sakharov Prize Talk: Supporting Repressed Scientists: Continuing Efforts

    NASA Astrophysics Data System (ADS)

    Birman, Joseph L.

    2010-02-01

    Some years ago, Max Perutz asked ``By What Right Do We Scientists Invoke Human Rights?" My presentation will start with mentioning actions of the international community which relate to this question. Such action as the creation in 1919 of the International Research Council, and continuing on to the present with the UN sanctioned International Council of Scientific Unions [ICSU], and other Committees such as those formed by APS, CCS, NYAS, AAAS which give support to repressed scientists around the world now. My own work has attempted to combine my individual initiatives with work as a member and officer of these groups. Together with like minded colleagues who are deeply affected when colleagues are discharged from their positions, exiled, imprisoned and subject to brutal treatment, often after mock ``trials", we react. On visits in 1968 to conferences in Budapest, and then in 1969 to Moscow, Tallin and Leningrad I became personally and deeply touched by the lives of colleagues who were seriously constrained by living under dictatorships. I could move freely into and out of their countries,speak openly about my work or any other matter. They could not, under penalty of possibly serious punishment. Yet, I felt these people were like my extended family. If my grandparents had not left Eastern Europe for the USA in the late 189Os our situations could have been reversed. A little later in the 197O's, ``refusenik" and ``dissident" scientists in the USSR needed support. Colleagues like Andrei Sakharov, Naum Meiman, Mark Azbel, Yakov Alpert, Yuri Orlov and others were being punished for exercising their rights under the UN sanctioned international protocals on ``Universality of Science and Free Circulation of Scientists". Their own governments [which signed these agreements] ignored the very protections they had supported. On frequent trips to the USSR during the 7Os,and 8Os I also seized the opportunity for ``individual initiative" to help these colleagues. I asked for

  6. ZBTB7A suppresses melanoma metastasis by transcriptionally repressing MCAM

    PubMed Central

    Liu, Xue-Song; Genet, Matthew D; Haines, Jenna E; Mehanna, Elie K; Wu, Shaowei; Chen, Hung-I Harry; Chen, Yidong; Qureshi, Abrar A; Han, Jiali; Chen, Xiang; Fisher, David E; Pandolfi, Pier Paolo; Yuan, Zhi-Min

    2015-01-01

    The excessive metastatic propensity of melanoma makes it the most deadly form of skin cancer, yet the underlying mechanism of metastasis remains elusive. Here, mining of cancer genome datasets discovered a frequent loss of chromosome 19p13.3 and associated down-regulation of the zinc finger transcription factor ZBTB7A in metastatic melanoma. Functional assessment of ZBTB7A-regulated genes identified MCAM, which encodes an adhesion protein key to melanoma metastasis. Using an integrated approach, it is demonstrated that ZBTB7A directly binds to the promoter and transcriptionally represses the expression of MCAM, establishing ZBTB7A as a bona fide transcriptional repressor of MCAM. Consistently, down-regulation of ZBTB7A results in marked upregulation of MCAM and enhanced melanoma cell invasion and metastasis. An inverse correlation of ZBTB7A and MCAM expression in association with melanoma metastasis is further validated with data from analysis of human melanoma specimens. Implications Together these results uncover a previously unrecognized role of ZBTB7A in negative regulation of melanoma metastasis and have important clinical implications. PMID:25995384

  7. Farnesoid X receptor represses hepatic lipase gene expression.

    PubMed

    Sirvent, Audrey; Verhoeven, Adrie J M; Jansen, Hans; Kosykh, Vladimir; Darteil, Raphaël J; Hum, Dean W; Fruchart, Jean-Charles; Staels, Bart

    2004-11-01

    The farnesoid X receptor (FXR) is a nuclear receptor that regulates gene expression in response to bile acids (BAs). FXR plays a central role in BA, cholesterol, and lipoprotein metabolism. Here, we identify HL, an enzyme involved in the metabolism of remnant and high density lipoproteins, as a novel FXR-regulated gene. The natural FXR ligand, chenodeoxycholic acid (CDCA), downregulates HL gene expression in a dose- and time-dependent manner in human hepatoma HepG2 cells. The nonsteroidal synthetic FXR agonist GW4064 also decreases HL mRNA levels in HepG2 cells and in primary human hepatocytes. Moreover, the decrease of HL mRNA levels after treatment with FXR agonists was associated with a significant decrease in secreted enzymatic activity. In addition, FXR-specific gene silencing using small interfering RNAs demonstrated that CDCA- and GW4064-mediated downregulation of HL transcript levels occurs via an FXR-dependent mechanism. Finally, using transient transfection experiments, it is shown that FXR represses transcriptional activity of a reporter driven by the -698/+13 bp human HL promoter. Taken together, these results identify HL as a new FXR-regulated gene in human liver cells. In view of the role of HL in plasma lipoprotein metabolism, our results further emphasize the central role of FXR in lipid homeostasis.

  8. Repression of TFII-I-dependent transcription by nuclear exclusion

    PubMed Central

    Tussié-Luna, María Isabel; Bayarsaihan, Dashzeveg; Ruddle, Frank H.; Roy, Ananda L.

    2001-01-01

    TFII-I is an unusual transcription factor possessing both basal and signal-induced transcriptional functions. Here we report the characterization of a TFII-I-related factor (MusTRD1/BEN) that regulates transcriptional functions of TFII-I by controlling its nuclear residency. MusTRD1/BEN has five or six direct repeats, each containing helix–loop–helix motifs, and, thus, belongs to the TFII-I family of transcription factors. TFII-I and MusTRD1/BEN, when expressed individually, show predominant nuclear localization. However, when the two proteins are coexpressed ectopically, MusTRD1/BEN locates almost exclusively to the nucleus, whereas TFII-I is largely excluded from the nucleus, resulting in a loss of TFII-I-dependent transcriptional activation of the c-fos promoter. Mutation of a consensus nuclear localization signal in MusTRD1/BEN results in a reversal of nuclear residency of the two proteins and a concomitant gain of c-fos promoter activity. These data suggest a means of transcriptional repression by competition at the level of nuclear occupancy. PMID:11438732

  9. The reconstruction of a repressed sexual molestation fifty years later.

    PubMed

    Viederman, M

    1995-01-01

    The current public concern about childhood molestation and abuse has fueled the debate in psychoanalysis about historical versus narrative truth, a subject that has implicitly and explicitly been an important theme since the origin of psychoanalysis. The evocation of false memories by suggestion has had significant social consequences. This raises important questions about the role of real trauma as contrasted with fantasy in the genesis of psychic conflict. This paper explores the conditions for the emergence of long repressed trauma. It is argued that such traumatic memories emerge only after significant structural change has occurred, in particular modifications in the representational world (self and object representations). This substantive change may be viewed as a macroscopic way station in the evolution of the analysis. This is demonstrated in the description of the analysis of a patient born with a congenital anomaly. The analysis of her unconscious fantasies about her deformity, her identifications with defective people, and of a negative paternal transference had to occur before the development of an erotic transference. It was then that fragments of the memory of the sexual trauma emerged. Details of the reconstruction are presented. The successful integration of this painful experience is described. Six years after termination of the analysis, the patient wrote a letter describing a confirmation of the event, now sixty years past, from the sole other survivor of the period who had knowledge of what had happened. PMID:8926329

  10. LATS2 Positively Regulates Polycomb Repressive Complex 2

    PubMed Central

    Torigata, Kosuke; Daisuke, Okuzaki; Mukai, Satomi; Hatanaka, Akira; Ohka, Fumiharu; Motooka, Daisuke; Nakamura, Shota; Ohkawa, Yasuyuki; Yabuta, Norikazu; Kondo, Yutaka; Nojima, Hiroshi

    2016-01-01

    LATS2, a pivotal Ser/Thr kinase of the Hippo pathway, plays important roles in many biological processes. LATS2 also function in Hippo-independent pathway, including mitosis, DNA damage response and epithelial to mesenchymal transition. However, the physiological relevance and molecular basis of these LATS2 functions remain obscure. To understand novel functions of LATS2, we constructed a LATS2 knockout HeLa-S3 cell line using TAL-effector nuclease (TALEN). Integrated omics profiling of this cell line revealed that LATS2 knockout caused genome-wide downregulation of Polycomb repressive complex 2 (PRC2) and H3K27me3. Cell-cycle analysis revealed that downregulation of PRC2 was not due to cell cycle aberrations caused by LATS2 knockout. Not LATS1, a homolog of LATS2, but LATS2 bound PRC2 on chromatin and phosphorylated it. LATS2 positively regulates histone methyltransferase activity of PRC2 and their expression at both the mRNA and protein levels. Our findings reveal a novel signal upstream of PRC2, and provide insight into the crucial role of LATS2 in coordinating the epigenome through regulation of PRC2. PMID:27434182

  11. Tristetraprolin Represses Estrogen Receptor α Transactivation in Breast Cancer Cells*

    PubMed Central

    Barrios-García, Tonatiuh; Tecalco-Cruz, Angeles; Gómez-Romero, Vania; Reyes-Carmona, Sandra; Meneses-Morales, Iván; León-Del-Río, Alfonso

    2014-01-01

    Estrogen receptor α (ERα) mediates the effects of 17β-estradiol (E2) in normal mammary gland, and it is a key participant in breast cancer tumor development. ERα transactivation activity is mediated by the synergistic interaction of two domains designated AF1 and AF2. The function of AF2 is to recruit coactivator and corepressor proteins that allow ERα to oscillate between the roles of transcriptional activator and repressor. In contrast, the mechanism responsible for AF-1 transcriptional activity is not completely understood. In this study, we identified tristetraproline (TTP) as a novel ERα-associated protein. TTP expression in MCF7 cells repressed ERα transactivation and reduced MCF7 cell proliferation and the ability of the cells to form tumors in a mouse model. We show that TTP transcriptional activity is mediated through its recruitment to the promoter region of ERα target genes and its interaction with histone deacetylases, in particular with HDAC1. TTP expression attenuates the coactivating activity of SRC-1, suggesting that exchange between TTP and other coactivators may play an important role in fine-tuning ERα transactivation. These results indicate that TTP acts as a bona fide ERα corepressor and suggest that this protein may be a contributing factor in the development of E2-dependent tumors in breast cancer. PMID:24737323

  12. Tristetraprolin represses estrogen receptor α transactivation in breast cancer cells.

    PubMed

    Barrios-García, Tonatiuh; Tecalco-Cruz, Angeles; Gómez-Romero, Vania; Reyes-Carmona, Sandra; Meneses-Morales, Iván; León-Del-Río, Alfonso

    2014-05-30

    Estrogen receptor α (ERα) mediates the effects of 17β-estradiol (E2) in normal mammary gland, and it is a key participant in breast cancer tumor development. ERα transactivation activity is mediated by the synergistic interaction of two domains designated AF1 and AF2. The function of AF2 is to recruit coactivator and corepressor proteins that allow ERα to oscillate between the roles of transcriptional activator and repressor. In contrast, the mechanism responsible for AF-1 transcriptional activity is not completely understood. In this study, we identified tristetraproline (TTP) as a novel ERα-associated protein. TTP expression in MCF7 cells repressed ERα transactivation and reduced MCF7 cell proliferation and the ability of the cells to form tumors in a mouse model. We show that TTP transcriptional activity is mediated through its recruitment to the promoter region of ERα target genes and its interaction with histone deacetylases, in particular with HDAC1. TTP expression attenuates the coactivating activity of SRC-1, suggesting that exchange between TTP and other coactivators may play an important role in fine-tuning ERα transactivation. These results indicate that TTP acts as a bona fide ERα corepressor and suggest that this protein may be a contributing factor in the development of E2-dependent tumors in breast cancer.

  13. Understanding carbon catabolite repression in Escherichia coli using quantitative models.

    PubMed

    Kremling, A; Geiselmann, J; Ropers, D; de Jong, H

    2015-02-01

    Carbon catabolite repression (CCR) controls the order in which different carbon sources are metabolized. Although this system is one of the paradigms of the regulation of gene expression in bacteria, the underlying mechanisms remain controversial. CCR involves the coordination of different subsystems of the cell that are responsible for the uptake of carbon sources, their breakdown for the production of energy and precursors, and the conversion of the latter to biomass. The complexity of this integrated system, with regulatory mechanisms cutting across metabolism, gene expression, and signaling, and that are subject to global physical and physiological constraints, has motivated important modeling efforts over the past four decades, especially in the enterobacterium Escherichia coli. Different hypotheses concerning the dynamic functioning of the system have been explored by a variety of modeling approaches. We review these studies and summarize their contributions to the quantitative understanding of CCR, focusing on diauxic growth in E. coli. Moreover, we propose a highly simplified representation of diauxic growth that makes it possible to bring out the salient features of the models proposed in the literature and confront and compare the explanations they provide.

  14. Tristetraprolin represses estrogen receptor α transactivation in breast cancer cells.

    PubMed

    Barrios-García, Tonatiuh; Tecalco-Cruz, Angeles; Gómez-Romero, Vania; Reyes-Carmona, Sandra; Meneses-Morales, Iván; León-Del-Río, Alfonso

    2014-05-30

    Estrogen receptor α (ERα) mediates the effects of 17β-estradiol (E2) in normal mammary gland, and it is a key participant in breast cancer tumor development. ERα transactivation activity is mediated by the synergistic interaction of two domains designated AF1 and AF2. The function of AF2 is to recruit coactivator and corepressor proteins that allow ERα to oscillate between the roles of transcriptional activator and repressor. In contrast, the mechanism responsible for AF-1 transcriptional activity is not completely understood. In this study, we identified tristetraproline (TTP) as a novel ERα-associated protein. TTP expression in MCF7 cells repressed ERα transactivation and reduced MCF7 cell proliferation and the ability of the cells to form tumors in a mouse model. We show that TTP transcriptional activity is mediated through its recruitment to the promoter region of ERα target genes and its interaction with histone deacetylases, in particular with HDAC1. TTP expression attenuates the coactivating activity of SRC-1, suggesting that exchange between TTP and other coactivators may play an important role in fine-tuning ERα transactivation. These results indicate that TTP acts as a bona fide ERα corepressor and suggest that this protein may be a contributing factor in the development of E2-dependent tumors in breast cancer. PMID:24737323

  15. Angiogenesis is repressed by ethanol exposure during chick embryonic development.

    PubMed

    Wang, Guang; Zhong, Shan; Zhang, Shi-yao; Ma, Zheng-lai; Chen, Jian-long; Lu, Wen-hui; Cheng, Xin; Chuai, Manli; Lee, Kenneth Ka Ho; Lu, Da-xiang; Yang, Xuesong

    2016-05-01

    It is now known that excess alcohol consumption during pregnancy can cause fetal alcohol syndrome to develop. However, it is not known whether excess ethanol exposure could directly affect angiogenesis in the embryo or angiogenesis being indirectly affected because of ethanol-induced fetal alcohol syndrome. Using the chick yolk sac membrane (YSM) model, we demonstrated that ethanol exposure dramatically inhibited angiogenesis in the YSM of 9-day-old chick embryos, in a dose-dependent manner. Likewise, the anti-angiogenesis effect of ethanol could be seen in the developing vessel plexus (at the same extra-embryonic regions) during earlier stages of embryo development. The anti-angiogenic effect of ethanol was found associated with excess reactive oxygen species (ROS) production; as glutathione peroxidase activity increased while superoxide dismutase 1 and 2 activities decreased in the YSMs. We further validated this observation by exposing chick embryos to 2,2'-azobis-amidinopropane dihydrochloride (a ROS inducer) and obtained a similar anti-angiogenesis effect as ethanol treatment. Semiquantitative reverse transcription-polymerase chain reaction analysis of the experimental YSMs revealed that expression of angiogenesis-related genes, vascular endothelial growth factor and its receptor, fibroblast growth factor 2 and hypoxia-inducible factor, were all repressed following ethanol and 2,2'-azobis-amidinopropane dihydrochloride treatment. In summary, our results suggest that excess ethanol exposure inhibits embryonic angiogenesis through promoting superfluous ROS production during embryo development. PMID:26177723

  16. Regulatory interactions between RNA and polycomb repressive complex 2.

    PubMed

    Cifuentes-Rojas, Catherine; Hernandez, Alfredo J; Sarma, Kavitha; Lee, Jeannie T

    2014-07-17

    Polycomb repressive complex 2 (PRC2) is a histone methyltransferase that is localized to thousands of mammalian genes. Though important to human disease and as a drug target, how PRC2 is recruited remains unclear. One model invokes cis-regulatory RNA. Herein, we biochemically and functionally probe PRC2's recognition of RNA using the X-inactivation model. We observe surprisingly high discriminatory capabilities. While SUZ12 and JARID2 subunits can bind RNA, EZH2 has highest affinity and is somewhat promiscuous. EED regulates the affinity of EZH2 for RNA, lending greater specificity to PRC2-RNA interactions. Intriguingly, while RNA is crucial for targeting, RNA inhibits EZH2's catalytic activity. JARID2 weakens PRC2's binding to RNA and relieves catalytic inhibition. We propose that RNA guides PRC2 to its target but inhibits its enzymatic activity until PRC2 associates with JARID2 on chromatin. Our study provides a molecular view of regulatory interactions between RNA and PRC2 at the chromatin interface.

  17. Repression of liver colorectal metastasis by the serpin Spn4A a naturally occurring inhibitor of the constitutive secretory proprotein convertases

    PubMed Central

    Sfaxi, Fatma; Scamuffa, Nathalie; Lalou, Claude; Ma, Jia; Metrakos, Peter; Siegfried, Géraldine; Ragg, Hermann; Bikfalvi, Andreas; Calvo, Fabien; Khatib, Abdel-Majid

    2014-01-01

    Liver is the most common site of metastasis from colorectal cancers, and liver of patients with liver colorectal metastasis have abnormal levels of the proprotein convertases (PCs). These proteases are involved in the activation and/or expression of various colon cancer-related mediators, making them promising targets in colorectal liver metastasis therapy. Here, we revealed that the serpin Spn4 from Drosophila melanogaster inhibits the activity of all the PCs found in the constitutive secretory pathway and represses the metastatic potential of the colon cancer cells HT-29 and CT-26. In these cells, Spn4A inhibited the processing of the PCs substrates IGF-1R and PDGF-A that associated their reduced anchorage-independent growth, invasiveness and survival in response to apoptotic agents. In vivo, Spn4A-expressing tumor cells showed repressed subcutaneous tumor development and liver metastases formation in response to their intrasplenic inoculation. In these cells Spn4A induced the expression of molecules with anti-metastatic functions and inhibited expression of pro-tumorigenic molecules. Taken together, our findings identify Spn4A as the only endogenous inhibitor of all the constitutive secretory pathway PCs, which is able to repress the metastatic potential of colon cancer cells. These results suggest the potential use of Spn4A and/or derivates as a useful adduct colorectal liver metastasis prevention. PMID:24961901

  18. AccR Is a Master Regulator Involved in Carbon Catabolite Repression of the Anaerobic Catabolism of Aromatic Compounds in Azoarcus sp. CIB*

    PubMed Central

    Valderrama, J. Andrés; Shingler, Victoria; Carmona, Manuel; Díaz, Eduardo

    2014-01-01

    Here we characterized the first known transcriptional regulator that accounts for carbon catabolite repression (CCR) control of the anaerobic catabolism of aromatic compounds in bacteria. The AccR response regulator of Azoarcus sp. CIB controls succinate-responsive CCR of the central pathways for the anaerobic catabolism of aromatics by this strain. Phosphorylation of AccR to AccR-P triggers a monomer-to-dimer transition as well as the ability to bind to the target promoter and causes repression both in vivo and in vitro. Substitution of the Asp60 phosphorylation target residue of the N-terminal receiver motif of AccR to a phosphomimic Glu residue generates a constitutively active derivative that behaves as a superrepressor of the target genes. AccR-P binds in vitro to a conserved inverted repeat (ATGCA-N6-TGCAT) present at two different locations within the PN promoter of the bzd genes for anaerobic benzoate degradation. Because the DNA binding-proficient C-terminal domain of AccR is monomeric, we propose an activation mechanism in which phosphorylation of Asp60 of AccR alleviates interdomain repression mediated by the N-terminal domain. The presence of AccR-like proteins encoded in the genomes of other β-proteobacteria of the Azoarcus/Thauera group further suggests that AccR constitutes a master regulator that controls anaerobic CCR in these bacteria. PMID:24302740

  19. AccR is a master regulator involved in carbon catabolite repression of the anaerobic catabolism of aromatic compounds in Azoarcus sp. CIB.

    PubMed

    Valderrama, J Andrés; Shingler, Victoria; Carmona, Manuel; Díaz, Eduardo

    2014-01-24

    Here we characterized the first known transcriptional regulator that accounts for carbon catabolite repression (CCR) control of the anaerobic catabolism of aromatic compounds in bacteria. The AccR response regulator of Azoarcus sp. CIB controls succinate-responsive CCR of the central pathways for the anaerobic catabolism of aromatics by this strain. Phosphorylation of AccR to AccR-P triggers a monomer-to-dimer transition as well as the ability to bind to the target promoter and causes repression both in vivo and in vitro. Substitution of the Asp(60) phosphorylation target residue of the N-terminal receiver motif of AccR to a phosphomimic Glu residue generates a constitutively active derivative that behaves as a superrepressor of the target genes. AccR-P binds in vitro to a conserved inverted repeat (ATGCA-N6-TGCAT) present at two different locations within the PN promoter of the bzd genes for anaerobic benzoate degradation. Because the DNA binding-proficient C-terminal domain of AccR is monomeric, we propose an activation mechanism in which phosphorylation of Asp(60) of AccR alleviates interdomain repression mediated by the N-terminal domain. The presence of AccR-like proteins encoded in the genomes of other β-proteobacteria of the Azoarcus/Thauera group further suggests that AccR constitutes a master regulator that controls anaerobic CCR in these bacteria. PMID:24302740

  20. De-repression of RaRF-mediated RAR repression by adenovirus E1A in the nucleolus.

    PubMed

    Um, Soo-Jong; Youn, Hye Sook; Kim, Eun-Joo

    2014-02-21

    Transcriptional activity of the retinoic acid receptor (RAR) is regulated by diverse binding partners, including classical corepressors and coactivators, in response to its ligand retinoic acid (RA). Recently, we identified a novel corepressor of RAR called the retinoic acid resistance factor (RaRF) (manuscript submitted). Here, we report how adenovirus E1A stimulates RAR activity by associating with RaRF. Based on immunoprecipitation (IP) assays, E1A interacts with RaRF through the conserved region 2 (CR2), which is also responsible for pRb binding. The first coiled-coil domain of RaRF was sufficient for this interaction. An in vitro glutathione-S-transferase (GST) pull-down assay was used to confirm the direct interaction between E1A and RaRF. Further fluorescence microscopy indicated that E1A and RaRF were located in the nucleoplasm and nucleolus, respectively. However, RaRF overexpression promoted nucleolar translocation of E1A from the nucleoplasm. Both the RA-dependent interaction of RAR with RaRF and RAR translocation to the nucleolus were disrupted by E1A. RaRF-mediated RAR repression was impaired by wild-type E1A, but not by the RaRF binding-defective E1A mutant. Taken together, our data suggest that E1A is sequestered to the nucleolus by RaRF through a specific interaction, thereby leaving RAR in the nucleoplasm for transcriptional activation.

  1. Indole-3-carbinol (I3C) increases apoptosis, represses growth of cancer cells, and enhances adenovirus-mediated oncolysis.

    PubMed

    Chen, Lan; Cheng, Pei-Hsin; Rao, Xiao-Mei; McMasters, Kelly M; Zhou, Heshan Sam

    2014-09-01

    Epidemiological studies suggest that high intake of cruciferous vegetables is associated with a lower risk of cancer. Experiments have shown that indole-3-carbinol (I3C), a naturally occurring compound derived from cruciferous vegetables, exhibits potent anticarcinogenic properties in a wide range of cancers. In this study, we showed that higher doses of I3C (≥400 μM) induced apoptotic cancer cell death and lower doses of I3C (≤200 μM) repressed cancer cell growth concurrently with suppressed expression of cyclin E and its partner CDK2. Notably, we found that pretreatment with low doses of I3C enhanced Ad-mediated oncolysis and cytotoxicity of human carcinoma cells by synergistic upregulation of apoptosis. Thus, the vegetable compound I3C as a dietary supplement may benefit cancer prevention and improve Ad oncolytic therapies.

  2. Comment on "Multiple repressive mechanisms in the hippocampus during memory formation".

    PubMed

    Mathew, Rebecca S; Mullan, Hillary; Blusztajn, Jan Krzysztof; Lehtinen, Maria K

    2016-07-29

    Cho et al. (Reports, 2 October 2015, p. 82) report that gene repression after contextual fear conditioning regulates hippocampal memory formation. We observe low levels of expression for many of the top candidate genes in the hippocampus and robust expression in the choroid plexus, as well as repression at 4 hours after contextual fear conditioning, suggesting the inclusion of choroid plexus messenger RNAs in Cho et al. hippocampal samples. PMID:27482552

  3. Long noncoding RNA EWSAT1-mediated gene repression facilitates Ewing sarcoma oncogenesis

    PubMed Central

    Marques Howarth, Michelle; Simpson, David; Ngok, Siu P.; Nieves, Bethsaida; Chen, Ron; Siprashvili, Zurab; Vaka, Dedeepya; Breese, Marcus R.; Crompton, Brian D.; Alexe, Gabriela; Hawkins, Doug S.; Jacobson, Damon; Brunner, Alayne L.; West, Robert; Mora, Jaume; Stegmaier, Kimberly; Khavari, Paul; Sweet-Cordero, E. Alejandro

    2014-01-01

    Chromosomal translocation that results in fusion of the genes encoding RNA-binding protein EWS and transcription factor FLI1 (EWS-FLI1) is pathognomonic for Ewing sarcoma. EWS-FLI1 alters gene expression through mechanisms that are not completely understood. We performed RNA sequencing (RNAseq) analysis on primary pediatric human mesenchymal progenitor cells (pMPCs) expressing EWS-FLI1 in order to identify gene targets of this oncoprotein. We determined that long noncoding RNA-277 (Ewing sarcoma–associated transcript 1 [EWSAT1]) is upregulated by EWS-FLI1 in pMPCs. Inhibition of EWSAT1 expression diminished the ability of Ewing sarcoma cell lines to proliferate and form colonies in soft agar, whereas EWSAT1 inhibition had no effect on other cell types tested. Expression of EWS-FLI1 and EWSAT1 repressed gene expression, and a substantial fraction of targets that were repressed by EWS-FLI1 were also repressed by EWSAT1. Analysis of RNAseq data from primary human Ewing sarcoma further supported a role for EWSAT1 in mediating gene repression. We identified heterogeneous nuclear ribonucleoprotein (HNRNPK) as an RNA-binding protein that interacts with EWSAT1 and found a marked overlap in HNRNPK-repressed genes and those repressed by EWS-FLI1 and EWSAT1, suggesting that HNRNPK participates in EWSAT1-mediated gene repression. Together, our data reveal that EWSAT1 is a downstream target of EWS-FLI1 that facilitates the development of Ewing sarcoma via the repression of target genes. PMID:25401475

  4. Viral Repression of Fungal Pheromone Precursor Gene Expression

    PubMed Central

    Zhang, Lei; Baasiri, Rudeina A.; Van Alfen, Neal K.

    1998-01-01

    Biological control of chestnut blight caused by the filamentous ascomycete Cryphonectria parasitica can be achieved with a virus that infects this fungus. This hypovirus causes a perturbation of fungal development that results in low virulence (hypovirulence), poor asexual sporulation, and female infertility without affecting fungal growth in culture. At the molecular level, the virus is known to affect the transcription of a number of fungal genes. Two of these genes, Vir1 and Vir2, produce abundant transcripts in noninfected strains of the fungus, but the transcripts are not detectable in virus-infected strains. We report here that these two genes encode the pheromone precursors of the Mat-2 mating type of the fungus; consequently, these genes have been renamed Mf2/1 and Mf2/2. To determine if the virus affects the mating systems of both mating types of this fungus, the pheromone precursor gene, Mf1/1, of a Mat-1 strain was cloned and likewise was found to be repressed in virus-infected strains. The suppression of transcription of the pheromone precursor genes of this fungus could be the cause of the mating defect of infected strains of the fungus. Although published reports suggest that a Gαi subunit may be involved in this regulation, our results do not support this hypothesis. The prepropheromone encoded by Mf1/1 is structurally similar to that of the prepro-p-factor of Schizosaccharomyces pombe. This is the first description of the complete set of pheromone precursor genes encoded by a filamentous ascomycete. PMID:9447992

  5. CcpA-Dependent Carbon Catabolite Repression in Bacteria

    PubMed Central

    Warner, Jessica B.; Lolkema, Juke S.

    2003-01-01

    Carbon catabolite repression (CCR) by transcriptional regulators follows different mechanisms in gram-positive and gram-negative bacteria. In gram-positive bacteria, CcpA-dependent CCR is mediated by phosphorylation of the phosphoenolpyruvate:sugar phosphotransferase system intermediate HPr at a serine residue at the expense of ATP. The reaction is catalyzed by HPr kinase, which is activated by glycolytic intermediates. In this review, the distribution of CcpA-dependent CCR among bacteria is investigated by searching the public databases for homologues of HPr kinase and HPr-like proteins throughout the bacterial kingdom and by analyzing their properties. Homologues of HPr kinase are commonly observed in the phylum Firmicutes but are also found in the phyla Proteobacteria, Fusobacteria, Spirochaetes, and Chlorobi, suggesting that CcpA-dependent CCR is not restricted to gram-positive bacteria. In the α and β subdivisions of the Proteobacteria, the presence of HPr kinase appears to be common, while in the γ subdivision it is more of an exception. The genes coding for the HPr kinase homologues of the Proteobacteria are in a gene cluster together with an HPr-like protein, termed XPr, suggesting a functional relationship. Moreover, the XPr proteins contain the serine phosphorylation sequence motif. Remarkably, the analysis suggests a possible relation between CcpA-dependent gene regulation and the nitrogen regulation system (Ntr) found in the γ subdivision of the Proteobacteria. The relation is suggested by the clustering of CCR and Ntr components on the genome of members of the Proteobacteria and by the close phylogenetic relationship between XPr and NPr, the HPr-like protein in the Ntr system. In bacteria in the phylum Proteobacteria that contain HPr kinase and XPr, the latter may be at the center of a complex regulatory network involving both CCR and the Ntr system. PMID:14665673

  6. Bacterial promoter repression by DNA looping without protein-protein binding competition.

    PubMed

    Becker, Nicole A; Greiner, Alexander M; Peters, Justin P; Maher, L James

    2014-05-01

    The Escherichia coli lactose operon provides a paradigm for understanding gene control by DNA looping where the lac repressor (LacI) protein competes with RNA polymerase for DNA binding. Not all promoter loops involve direct competition between repressor and RNA polymerase. This raises the possibility that positioning a promoter within a tightly constrained DNA loop is repressive per se, an idea that has previously only been considered in vitro. Here, we engineer living E. coli bacteria to measure repression due to promoter positioning within such a tightly constrained DNA loop in the absence of protein-protein binding competition. We show that promoters held within such DNA loops are repressed ∼100-fold, with up to an additional ∼10-fold repression (∼1000-fold total) dependent on topological positioning of the promoter on the inner or outer face of the DNA loop. Chromatin immunoprecipitation data suggest that repression involves inhibition of both RNA polymerase initiation and elongation. These in vivo results show that gene repression can result from tightly looping promoter DNA even in the absence of direct competition between repressor and RNA polymerase binding. PMID:24598256

  7. Structural insights into Transcriptional Repression by non-coding RNAs that bind to Human Pol II

    PubMed Central

    Kassube, Susanne A.; Fang, Jie; Grob, Patricia; Yakovchuk, Petro; Goodrich, James A.; Nogales, Eva

    2012-01-01

    Gene transcription is regulated in response to environmental changes as well as developmental cues. In mammalian cells subjected to stress conditions such as heat shock, transcription of most protein-coding genes decreases, while the transcription of heat shock protein genes increases. Repression involves direct binding to RNA polymerase II (Pol II) of certain non-coding RNAs (ncRNAs) that are upregulated upon heat shock. Another class of ncRNAs is also upregulated and binds to Pol II, but does not inhibit transcription. Incorporation of repressive ncRNAs into pre-initiation complexes prevents transcription initiation, while non-repressive ncRNAs are displaced from Pol II by TFIIF. Here, we present cryo-EM reconstructions of human Pol II in complex with six different ncRNAs from mouse and human. Our structures show that both repressive and non-repressive ncRNAs bind to a conserved binding site within the cleft of Pol II. The site, also shared with a previously characterized yeast aptamer, is close to the active center and thus in an ideal position to regulate transcription. Importantly, additional RNA elements extend flexibly beyond the docking site. We propose that the differences concerning the repressive activity of the ncRNA analyzed must be due to the distinct character of these more unstructured, flexible segments of the RNA that emanate from the cleft. PMID:22954660

  8. Mechanisms and consequences of ATMIN repression in hypoxic conditions: roles for p53 and HIF-1

    PubMed Central

    Leszczynska, Katarzyna B.; Göttgens, Eva-Leonne; Biasoli, Deborah; Olcina, Monica M.; Ient, Jonathan; Anbalagan, Selvakumar; Bernhardt, Stephan; Giaccia, Amato J.; Hammond, Ester M.

    2016-01-01

    Hypoxia-induced replication stress is one of the most physiologically relevant signals known to activate ATM in tumors. Recently, the ATM interactor (ATMIN) was identified as critical for replication stress-induced activation of ATM in response to aphidicolin and hydroxyurea. This suggests an essential role for ATMIN in ATM regulation during hypoxia, which induces replication stress. However, ATMIN also has a role in base excision repair, a process that has been demonstrated to be repressed and less efficient in hypoxic conditions. Here, we demonstrate that ATMIN is dispensable for ATM activation in hypoxia and in contrast to ATM, does not affect cell survival and radiosensitivity in hypoxia. Instead, we show that in hypoxic conditions ATMIN expression is repressed. Repression of ATMIN in hypoxia is mediated by both p53 and HIF-1α in an oxygen dependent manner. The biological consequence of ATMIN repression in hypoxia is decreased expression of the target gene, DYNLL1. An expression signature associated with p53 activity was negatively correlated with DYNLL1 expression in patient samples further supporting the p53 dependent repression of DYNLL1. Together, these data demonstrate multiple mechanisms of ATMIN repression in hypoxia with consequences including impaired BER and down regulation of the ATMIN transcriptional target, DYNLL1. PMID:26875667

  9. Selective repression of light harvesting complex 2 formation in Rhodobacter azotoformans by light under semiaerobic conditions.

    PubMed

    Yue, Huiying; Zhao, Chungui; Li, Kai; Yang, Suping

    2015-11-01

    Photosystem formation in anaerobic anoxygenic phototrophic bacteria (APB) is repressed by oxygen but is de-repressed when oxygen tension decreases. Under semiaerobic conditions, the synthesis of photopigments and pigment protein complexes in Rhodobacter (Rba.) sphaeroides are repressed by light. AppA, a blue-light receptor, mediates this regulation. In the present study, it was showed that the synthesis of bacteriochlorophyll, carotenoid, and pigment protein complexes in Rba. azotoformans 134K20 was significantly repressed by oxygen. Oxygen exposure also led to a conversion of spheroidene to spheroidenone. In semiaerobically growing cells, light irradiation resulted in a decrease in the formation of photosystem, and blue light was found to be the most effective light source. Blue light reduced the contents of bacteriochlorophyll and carotenoid slightly, but had negligible effects on light harvesting complex (LH) 1 content, whereas the content of LH2 was significantly decreased indicating that blue light selectively repressed the synthesis of LH2 in semiaerobically growing 134K20. It was concluded that, similar to Rba. sphaeroides, a blue light receptor presented in strain 134K20 played important roles in its light-dependent repression. A possible mechanism involved in controlling the differential inhibitory of blue light on the synthesis of photosystem was discussed. PMID:26193456

  10. Protein sequestration versus Hill-type repression in circadian clock models.

    PubMed

    Kim, Jae Kyoung

    2016-08-01

    Circadian (∼24 h) clocks are self-sustained endogenous oscillators with which organisms keep track of daily and seasonal time. Circadian clocks frequently rely on interlocked transcriptional-translational feedback loops to generate rhythms that are robust against intrinsic and extrinsic perturbations. To investigate the dynamics and mechanisms of the intracellular feedback loops in circadian clocks, a number of mathematical models have been developed. The majority of the models use Hill functions to describe transcriptional repression in a way that is similar to the Goodwin model. Recently, a new class of models with protein sequestration-based repression has been introduced. Here, the author discusses how this new class of models differs dramatically from those based on Hill-type repression in several fundamental aspects: conditions for rhythm generation, robust network designs and the periods of coupled oscillators. Consistently, these fundamental properties of circadian clocks also differ among Neurospora, Drosophila, and mammals depending on their key transcriptional repression mechanisms (Hill-type repression or protein sequestration). Based on both theoretical and experimental studies, this review highlights the importance of careful modelling of transcriptional repression mechanisms in molecular circadian clocks. PMID:27444022

  11. PTH and Vitamin D Repress DMP1 in Cementoblasts

    PubMed Central

    Wang, L.; Tran, A.B.; Nociti, F.H.; Thumbigere-Math, V.; Foster, B.L.; Krieger, C.C.; Kantovitz, K.R.; Novince, C.M.; Koh, A.J.; McCauley, L.K.; Somerman, M.J.

    2015-01-01

    A complex feedback mechanism between parathyroid hormone (PTH), 1,25(OH)2D3 (1,25D), and fibroblast growth factor 23 (FGF-23) maintains mineral homeostasis, in part by regulating calcium and phosphate absorption/reabsorption. Previously, we showed that 1,25D regulates mineral homeostasis by repressing dentin matrix protein 1 (DMP1) via the vitamin D receptor pathway. Similar to 1,25D, PTH may modulate DMP1, but the underlying mechanism remains unknown. Immortalized murine cementoblasts (OCCM.30), similar to osteoblasts and known to express DMP1, were treated with PTH (1–34). Real-time quantitative polymerase chain reaction (PCR) and Western blot revealed that PTH decreased DMP1 gene transcription (85%) and protein expression (30%), respectively. PTH mediated the downregulation of DMP1 via the cAMP/protein kinase A (PKA) pathway. Immunohistochemistry confirmed the decreased localization of DMP1 in vivo in cellular cementum and alveolar bone of mice treated with a single dose (50 µg/kg) of PTH (1–34). RNA-seq was employed to further identify patterns of gene expression shared by PTH and 1,25D in regulating DMP1, as well as other factors involved in mineral homeostasis. PTH and 1,25D mutually upregulated 36 genes and mutually downregulated 27 genes by ≥2-fold expression (P ≤ 0.05). Many identified genes were linked with the regulation of bone/tooth homeostasis, cell growth and differentiation, calcium signaling, and DMP1 transcription. Validation of RNA-seq results via PCR array confirmed a similar gene expression pattern in response to PTH and 1,25D treatment. Collectively, these results suggest that PTH and 1,25D share complementary effects in maintaining mineral homeostasis by mutual regulation of genes/proteins associated with calcium and phosphate metabolism while also exerting distinct roles on factors modulating mineral metabolism. Furthermore, PTH may modulate phosphate homeostasis by downregulating DMP1 expression via the cAMP/PKA pathway. Targeting

  12. Direct activation and anti-repression functions of GAL4-VP16 use distinct molecular mechanisms.

    PubMed Central

    Lyons, J G; Chambon, P

    1995-01-01

    In order to determine whether the molecular mechanisms used for direct activation by GAL4-VP16 are the same as those used for anti-repression, we have employed monoclonal antibodies specific for the VP16 activation domain. In the absence of added repressors, GAL4-VP16 was able to stimulate transcription from a template containing GAL4-binding sites, and the antibodies raised against the VP16 activation domain failed to inhibit this direct activation. GAL4-VP16 also was able to prevent histone H1-mediated repression by a mechanism that was strongly dependent on the presence of specific GAL4-binding elements in the promoter. However, in contrast to the assays conducted in the absence of repressors, the antibodies were strong inhibitors of GAL4-VP16-activated transcription in the presence of histone H1. Thus the binding of the antibodies distinguished between the direct activation and anti-repression functions of GAL4-VP16, indicating that these functions operate through distinct molecular mechanisms. The anti-repression-specific mechanism that is inhibitable by the antibodies acted at an early stage of preinitiation complex formation. Deletions of individual subdomains of the VP16 activation domain demonstrated that there was not a discrete subdomain responsible for the anti-repression function of GAL4-VP16. Thus, the inhibitory effect of the antibodies appeared to be due to the location of the epitope within the activator protein rather than to some inherent biochemical property of that region of the protein that is required specifically for anti-repression. The inhibitory effect of the antibodies also ruled out the possibility that steric exclusion of repressor proteins from the promoter was the sole means of anti-repression by the transcriptional activator. Images Figure 1 Figure 2 PMID:8554536

  13. EVI1 recruits the histone methyltransferase SUV39H1 for transcription repression.

    PubMed

    Cattaneo, Francesca; Nucifora, Giuseppina

    2008-10-01

    EVI1 is an oncoprotein inappropriately expressed in acute myeloid leukemia and myelodysplastic syndrome cells. In vitro studies indicate that diverse biological properties can be attributed to this protein. Its role in leukemogenesis is still unclear but it is thought that overall EVI1 can act mostly as a transcription repressor through its interaction with a subset of histone deacetylases. Studies with histone deacetylase inhibitors have however indicated that EVI1-mediated repression can be only partially rescued by deacetylase inhibitor drugs, suggesting that additional chromosomal modifications might occur to induce gene repression by EVI1. To investigate whether histone methylation contributes to the repressive potential of EVI1, we examined a potential association between EVI1, the histone methyltransferase (HMT) SUV39H1, and methyltransferase activity in vitro. We find that EVI1 directly interacts with SUV39H1 and that the proteins form an active complex with methyltransferase activity in vitro. Our data indicate that SUV39H1 enhances the transcription repressive potential of EVI1 in vivo. We suggest that EVI1 affects promoters' activity in two different pathways, by association with histone deacetylases and by recruiting chromatin-modifying enzymes to impose a heterochromatin-like structure establishing a lasting transcription repression.

  14. Transient repression of catabolite-sensitive enzyme synthesis elicited by 2,4-dinitrophenol.

    PubMed

    Oki, R

    1975-09-01

    Transient inhibition of catabolic enzyme synthesis in Escherichia coli occurred when a low concentration of 2,4-dinitrophenol (DNP) was simultaneously added with inducer. Using mutant strains defective for gamma-gene product or constitutive for lac enzymes, it was found that the inhibition is not due to the exclusion of inducer by uncoupling. The addition of cyclic adenosine 3',5'-monophosphate overcame repression. The components of the lac operon coordinately responded to DNP inhibition. From deoxyribonucleic acid-ribonucleic acid hybridization experiments, it was found that the inhibition of beta-galactosidase induction occurred at the level of messenger ribonucleic acid synthesis specific for the lac operon. It seems probable that DNP represses induction in a similar manner to that of transient repression observed upon the addition of glucose. Furthermore, it was found that transient repression disappeared if cells were preincubated with DNP before induction. This indicates that new contact of cells with DNP is obligatory for transient repression. From these results, it is suggested that the cell membrane may be responsible for regulation of catabolite-sensitive enzyme synthesis. PMID:169228

  15. [Catabolyte repression of Escherichia coli K12 mutants with defects in different systems of glucose transport].

    PubMed

    Gershanovich, V N; Iurovitskaia, N V; Komissarova, L V; Bol'shakova, T N; Erlagaeva, R S

    1976-01-01

    The phenomenon of glucose catabolite repression was studied in E. coli mutants inable to transport this carbohydrate. The pts 1, H mutant P34 was much less sensitive to the repressive effect of glucose on beta-galactosidase synthesis than the parent type. The 1103 mutant devoid of enzyme 1 of the phosphoenolpyruvate-dependent phosphotransferase system (PTS) behaves in the same way as P34 mutant after addition of glucose to casamino acid mineral medium. However, in minimal medium with succinate as the sole source of carbon, cells of the 1103 mutant show enhanced sensibility to transient glucose repression. The effect of hypersensibility disappears when the lac I mutation leading to constitutive the beta-galactosidase synthesis is introduced in 1103 mutant. It is shown that the enhanced sensibility of beta-galactosidase synthesis to glucose transient repression in 1103 mutant is an effect of the aburpt decrease in its growth rate in the presence of succinate and most probably this decrease leads to "inducer exclusion" of the lac operon. It is also shown that if one introduces the P34 mutation in strain JD3 devoid of one of the enzymes II for glucose (and due to this resistant to glucose catabolite respression) then the level of resistance in double mutant does not increase in spite of considerable supression of 14C glucose accumulation. In connection with this the role is discussed of separate components of the E. coli K 12 glucose transport system in realization of the phenomenon of catabolite repression. PMID:785237

  16. Histone methyltransferase Ash1L mediates activity-dependent repression of neurexin-1α.

    PubMed

    Zhu, Τao; Liang, Chen; Li, Dongdong; Tian, Miaomiao; Liu, Sanxiong; Gao, Guanjun; Guan, Ji-Song

    2016-05-27

    Activity-dependent transcription is critical for the regulation of long-term synaptic plasticity and plastic rewiring in the brain. Here, we report that the transcription of neurexin1α (nrxn1α), a presynaptic adhesion molecule for synaptic formation, is regulated by transient neuronal activation. We showed that 10 minutes of firing at 50 Hz in neurons repressed the expression of nrxn1α for 24 hours in a primary cortical neuron culture through a transcriptional repression mechanism. By performing a screening assay using a synthetic zinc finger protein (ZFP) to pull down the proteins enriched near the nrxn1α promoter region in vivo, we identified that Ash1L, a histone methyltransferase, is enriched in the nrxn1α promoter. Neuronal activity triggered binding of Ash1L to the promoter and enriched the histone marker H3K36me2 at the nrxn1α promoter region. Knockout of Ash1L in mice completely abolished the activity-dependent repression of nrxn1α. Taken together, our results reveal that a novel process of activity-dependent transcriptional repression exists in neurons and that Ash1L mediates the long-term repression of nrxn1α, thus implicating an important role for epigenetic modification in brain functioning.

  17. Histone methyltransferase Ash1L mediates activity-dependent repression of neurexin-1α

    PubMed Central

    Zhu, Τao; Liang, Chen; Li, Dongdong; Tian, Miaomiao; Liu, Sanxiong; Gao, Guanjun; Guan, Ji-Song

    2016-01-01

    Activity-dependent transcription is critical for the regulation of long-term synaptic plasticity and plastic rewiring in the brain. Here, we report that the transcription of neurexin1α (nrxn1α), a presynaptic adhesion molecule for synaptic formation, is regulated by transient neuronal activation. We showed that 10 minutes of firing at 50 Hz in neurons repressed the expression of nrxn1α for 24 hours in a primary cortical neuron culture through a transcriptional repression mechanism. By performing a screening assay using a synthetic zinc finger protein (ZFP) to pull down the proteins enriched near the nrxn1α promoter region in vivo, we identified that Ash1L, a histone methyltransferase, is enriched in the nrxn1α promoter. Neuronal activity triggered binding of Ash1L to the promoter and enriched the histone marker H3K36me2 at the nrxn1α promoter region. Knockout of Ash1L in mice completely abolished the activity-dependent repression of nrxn1α. Taken together, our results reveal that a novel process of activity-dependent transcriptional repression exists in neurons and that Ash1L mediates the long-term repression of nrxn1α, thus implicating an important role for epigenetic modification in brain functioning. PMID:27229316

  18. Androgen receptor repression of gonadotropin-releasing hormone gene transcription via enhancer 1.

    PubMed

    Brayman, Melissa J; Pepa, Patricia A; Mellon, Pamela L

    2012-11-01

    Gonadotropin-releasing hormone (GnRH) plays a major role in the hypothalamic-pituitary-gonadal (HPG) axis, and synthesis and secretion of GnRH are regulated by gonadal steroid hormones. Disruptions in androgen levels are involved in a number of reproductive defects, including hypogonadotropic hypogonadism and polycystic ovarian syndrome. Androgens down-regulate GnRH mRNA synthesis in vivo and in vitro via an androgen receptor (AR)-dependent mechanism. Methyltrienolone (R1881), a synthetic AR agonist, represses GnRH expression through multiple sites in the proximal promoter. In this study, we show AR also represses GnRH transcription via the major enhancer (GnRH-E1). A multimer of the -1800/-1766 region was repressed by R1881 treatment. Mutation of two bases, -1792 and -1791, resulted in decreased basal activity and a loss of AR-mediated repression. AR bound to the -1796/-1791 sequence in electrophoretic mobility shift assays, indicating a direct interaction with DNA or other transcription factors in this region. We conclude that AR repression of GnRH-E1 acts via multiple AR-responsive regions, including the site at -1792/-1791.

  19. A highly conserved molecular switch binds MSY-3 to regulate myogenin repression in postnatal muscle

    PubMed Central

    Berghella, Libera; De Angelis, Luciana; De Buysscher, Tristan; Mortazavi, Ali; Biressi, Stefano; Forcales, Sonia V.; Sirabella, Dario; Cossu, Giulio; Wold, Barbara J.

    2008-01-01

    Myogenin is the dominant transcriptional regulator of embryonic and fetal muscle differentiation and during maturation is profoundly down-regulated. We show that a highly conserved 17-bp DNA cis-acting sequence element located upstream of the myogenin promoter (myogHCE) is essential for postnatal repression of myogenin in transgenic animals. We present multiple lines of evidence supporting the idea that repression is mediated by the Y-box protein MSY-3. Electroporation in vivo shows that myogHCE and MSY-3 are required for postnatal repression. We further show that, in the C2C12 cell culture system, ectopic MSY-3 can repress differentiation, while reduced MSY-3 promotes premature differentiation. MSY-3 binds myogHCE simultaneously with the homeodomain protein Pbx in postnatal innervated muscle. We therefore propose a model in which the myogHCE motif operates as a switch by specifying opposing functions; one that was shown previously is regulated by MyoD and Pbx and it specifies a chromatin opening, gene-activating function at the time myoblasts begin to differentiate; the other includes MYS-3 and Pbx, and it specifies a repression function that operates during and after postnatal muscle maturation in vivo and in myoblasts before they begin to differentiate. PMID:18676817

  20. Wnt-mediated repression via bipartite DNA recognition by TCF in the Drosophila hematopoietic system.

    PubMed

    Zhang, Chen U; Blauwkamp, Timothy A; Burby, Peter E; Cadigan, Ken M

    2014-08-01

    The Wnt/β-catenin signaling pathway plays many important roles in animal development, tissue homeostasis and human disease. Transcription factors of the TCF family mediate many Wnt transcriptional responses, promoting signal-dependent activation or repression of target gene expression. The mechanism of this specificity is poorly understood. Previously, we demonstrated that for activated targets in Drosophila, TCF/Pangolin (the fly TCF) recognizes regulatory DNA through two DNA binding domains, with the High Mobility Group (HMG) domain binding HMG sites and the adjacent C-clamp domain binding Helper sites. Here, we report that TCF/Pangolin utilizes a similar bipartite mechanism to recognize and regulate several Wnt-repressed targets, but through HMG and Helper sites whose sequences are distinct from those found in activated targets. The type of HMG and Helper sites is sufficient to direct activation or repression of Wnt regulated cis-regulatory modules, and protease digestion studies suggest that TCF/Pangolin adopts distinct conformations when bound to either HMG-Helper site pair. This repressive mechanism occurs in the fly lymph gland, the larval hematopoietic organ, where Wnt/β-catenin signaling controls prohemocytic differentiation. Our study provides a paradigm for direct repression of target gene expression by Wnt/β-catenin signaling and allosteric regulation of a transcription factor by DNA. PMID:25144371

  1. Lactose-mediated carbon catabolite repression of putrescine production in dairy Lactococcus lactis is strain dependent.

    PubMed

    del Rio, Beatriz; Ladero, Victor; Redruello, Begoña; Linares, Daniel M; Fernández, Maria; Martín, Maria Cruz; Alvarez, Miguel A

    2015-06-01

    Lactococcus lactis is the lactic acid bacterial (LAB) species most widely used as a primary starter in the dairy industry. However, several strains of L. lactis produce the biogenic amine putrescine via the agmatine deiminase (AGDI) pathway. We previously reported the putrescine biosynthesis pathway in L. lactis subsp. cremoris GE2-14 to be regulated by carbon catabolic repression (CCR) via glucose but not lactose (Linares et al., 2013). The present study shows that both these sugars repress putrescine biosynthesis in L. lactis subsp. lactis T3/33, a strain isolated from a Spanish artisanal cheese. Furthermore, we demonstrated that both glucose and lactose repressed the transcriptional activity of the aguBDAC catabolic genes of the AGDI route. Finally, a screening performed in putrescine-producing dairy L. lactis strains determined that putrescine biosynthesis was repressed by lactose in all the L. lactis subsp. lactis strains tested, but in only one L. lactis subsp. cremoris strain. Given the obvious importance of the lactose-repression in cheese putrescine accumulation, it is advisable to consider the diversity of L. lactis in this sense and characterize consequently the starter cultures to select the safest strains.

  2. Repression by RB1 characterizes genes involved in the penultimate stage of erythroid development.

    PubMed

    Zhang, Ji; Loyd, Melanie R; Randall, Mindy S; Morris, John J; Shah, Jayesh G; Ney, Paul A

    2015-01-01

    Retinoblastoma-1 (RB1), and the RB1-related proteins p107 and p130, are key regulators of the cell cycle. Although RB1 is required for normal erythroid development in vitro, it is largely dispensable for erythropoiesis in vivo. The modest phenotype caused by RB1 deficiency in mice raises questions about redundancy within the RB1 family, and the role of RB1 in erythroid differentiation. Here we show that RB1 is the major pocket protein that regulates terminal erythroid differentiation. Erythroid cells lacking all pocket proteins exhibit the same cell cycle defects as those deficient for RB1 alone. RB1 has broad repressive effects on gene transcription in erythroid cells. As a group, RB1-repressed genes are generally well expressed but downregulated at the final stage of erythroid development. Repression correlates with E2F binding, implicating E2Fs in the recruitment of RB1 to repressed genes. Merging differential and time-dependent changes in expression, we define a group of approximately 800 RB1-repressed genes. Bioinformatics analysis shows that this list is enriched for terms related to the cell cycle, but also for terms related to terminal differentiation. Some of these have not been previously linked to RB1. These results expand the range of processes potentially regulated by RB1, and suggest that a principal role of RB1 in development is coordinating the events required for terminal differentiation. PMID:26397180

  3. Repressing distress in childhood: a defense against health-related stress.

    PubMed

    Gil, Armande

    2005-01-01

    This paper is a review of empirical investigations of the repressive adaptive style in youth. Studies were selected on the basis of their adherence to Weinberger et al.'s (J Abnorm Psychol 88: 369-380, 1979) paradigm, consisting of the interaction between a measure of distress and a measure of defensiveness to categorize repressors. The presence of a repressive style of adaptation was identified in adolescence, especially among pediatric populations. Adolescent repressors were found to exhibit characteristics similar to those identified among adult samples (i.e., self-deception, biased self-reports, and inhibition of signals of distress). Only one study focused on young repressors' autonomic reactivity, which is another main characteristic of a repressive adaptive style in adulthood. Methodological inconsistencies between child studies are highlighted and weaknesses in the psychometric properties of defensiveness measures in childhood are discussed. Future investigations should examine the impact of a repressive adaptive style on health outcomes and behaviors to see if adult health data associated with a repressive style of adaptation are replicable in childhood.

  4. Repression of SRF target genes is critical for Myc-dependent apoptosis of epithelial cells

    PubMed Central

    Wiese, Katrin E; Haikala, Heidi M; von Eyss, Björn; Wolf, Elmar; Esnault, Cyril; Rosenwald, Andreas; Treisman, Richard; Klefström, Juha; Eilers, Martin

    2015-01-01

    Oncogenic levels of Myc expression sensitize cells to multiple apoptotic stimuli, and this protects long-lived organisms from cancer development. How cells discriminate physiological from supraphysiological levels of Myc is largely unknown. Here, we show that induction of apoptosis by Myc in breast epithelial cells requires association of Myc with Miz1. Gene expression and ChIP-Sequencing experiments show that high levels of Myc invade target sites that lack consensus E-boxes in a complex with Miz1 and repress transcription. Myc/Miz1-repressed genes encode proteins involved in cell adhesion and migration and include several integrins. Promoters of repressed genes are enriched for binding sites of the serum-response factor (SRF). Restoring SRF activity antagonizes Myc repression of SRF target genes, attenuates Myc-induced apoptosis, and reverts a Myc-dependent decrease in Akt phosphorylation and activity, a well-characterized suppressor of Myc-induced apoptosis. We propose that high levels of Myc engage Miz1 in repressive DNA binding complexes and suppress an SRF-dependent transcriptional program that supports survival of epithelial cells. PMID:25896507

  5. FOXP3 interactions with histone acetyltransferase and class II histone deacetylases are required for repression.

    PubMed

    Li, Bin; Samanta, Arabinda; Song, Xiaomin; Iacono, Kathryn T; Bembas, Kathryn; Tao, Ran; Basu, Samik; Riley, James L; Hancock, Wayne W; Shen, Yuan; Saouaf, Sandra J; Greene, Mark I

    2007-03-13

    The forkhead family protein FOXP3 acts as a repressor of transcription and is both an essential and sufficient regulator of the development and function of regulatory T cells. The molecular mechanism by which FOXP3-mediated transcriptional repression occurs remains unclear. Here, we report that transcriptional repression by FOXP3 involves a histone acetyltransferase-deacetylase complex that includes histone acetyltransferase TIP60 (Tat-interactive protein, 60 kDa) and class II histone deacetylases HDAC7 and HDAC9. The N-terminal 106-190 aa of FOXP3 are required for TIP60-FOXP3, HDAC7-FOXP3 association, as well as for the transcriptional repression of FOXP3 via its forkhead domain. FOXP3 can be acetylated in primary human regulatory T cells, and TIP60 promotes FOXP3 acetylation in vivo. Overexpression of TIP60 but not its histone acetyltransferase-deficient mutant promotes, whereas knockdown of endogenous TIP60 relieved, FOXP3-mediated transcriptional repression. A minimum FOXP3 ensemble containing native TIP60 and HDAC7 is necessary for IL-2 production regulation in T cells. Moreover, FOXP3 association with HDAC9 is antagonized by T cell stimulation and can be restored by the protein deacetylation inhibitor trichostatin A, indicating a complex dynamic aspect of T suppressor cell regulation. These findings identify a previously uncharacterized complex-based mechanism by which FOXP3 actively mediates transcriptional repression. PMID:17360565

  6. FOXP3 interactions with histone acetyltransferase and class II histone deacetylases are required for repression

    PubMed Central

    Li, Bin; Samanta, Arabinda; Song, Xiaomin; Iacono, Kathryn T.; Bembas, Kathryn; Tao, Ran; Basu, Samik; Riley, James L.; Hancock, Wayne W.; Shen, Yuan; Saouaf, Sandra J.; Greene, Mark I.

    2007-01-01

    The forkhead family protein FOXP3 acts as a repressor of transcription and is both an essential and sufficient regulator of the development and function of regulatory T cells. The molecular mechanism by which FOXP3-mediated transcriptional repression occurs remains unclear. Here, we report that transcriptional repression by FOXP3 involves a histone acetyltransferase–deacetylase complex that includes histone acetyltransferase TIP60 (Tat-interactive protein, 60 kDa) and class II histone deacetylases HDAC7 and HDAC9. The N-terminal 106–190 aa of FOXP3 are required for TIP60–FOXP3, HDAC7–FOXP3 association, as well as for the transcriptional repression of FOXP3 via its forkhead domain. FOXP3 can be acetylated in primary human regulatory T cells, and TIP60 promotes FOXP3 acetylation in vivo. Overexpression of TIP60 but not its histone acetyltransferase-deficient mutant promotes, whereas knockdown of endogenous TIP60 relieved, FOXP3-mediated transcriptional repression. A minimum FOXP3 ensemble containing native TIP60 and HDAC7 is necessary for IL-2 production regulation in T cells. Moreover, FOXP3 association with HDAC9 is antagonized by T cell stimulation and can be restored by the protein deacetylation inhibitor trichostatin A, indicating a complex dynamic aspect of T suppressor cell regulation. These findings identify a previously uncharacterized complex-based mechanism by which FOXP3 actively mediates transcriptional repression. PMID:17360565

  7. Androgen receptor repression of gonadotropin-releasing hormone gene transcription via enhancer 1.

    PubMed

    Brayman, Melissa J; Pepa, Patricia A; Mellon, Pamela L

    2012-11-01

    Gonadotropin-releasing hormone (GnRH) plays a major role in the hypothalamic-pituitary-gonadal (HPG) axis, and synthesis and secretion of GnRH are regulated by gonadal steroid hormones. Disruptions in androgen levels are involved in a number of reproductive defects, including hypogonadotropic hypogonadism and polycystic ovarian syndrome. Androgens down-regulate GnRH mRNA synthesis in vivo and in vitro via an androgen receptor (AR)-dependent mechanism. Methyltrienolone (R1881), a synthetic AR agonist, represses GnRH expression through multiple sites in the proximal promoter. In this study, we show AR also represses GnRH transcription via the major enhancer (GnRH-E1). A multimer of the -1800/-1766 region was repressed by R1881 treatment. Mutation of two bases, -1792 and -1791, resulted in decreased basal activity and a loss of AR-mediated repression. AR bound to the -1796/-1791 sequence in electrophoretic mobility shift assays, indicating a direct interaction with DNA or other transcription factors in this region. We conclude that AR repression of GnRH-E1 acts via multiple AR-responsive regions, including the site at -1792/-1791. PMID:22877652

  8. Wnt-mediated repression via bipartite DNA recognition by TCF in the Drosophila hematopoietic system.

    PubMed

    Zhang, Chen U; Blauwkamp, Timothy A; Burby, Peter E; Cadigan, Ken M

    2014-08-01

    The Wnt/β-catenin signaling pathway plays many important roles in animal development, tissue homeostasis and human disease. Transcription factors of the TCF family mediate many Wnt transcriptional responses, promoting signal-dependent activation or repression of target gene expression. The mechanism of this specificity is poorly understood. Previously, we demonstrated that for activated targets in Drosophila, TCF/Pangolin (the fly TCF) recognizes regulatory DNA through two DNA binding domains, with the High Mobility Group (HMG) domain binding HMG sites and the adjacent C-clamp domain binding Helper sites. Here, we report that TCF/Pangolin utilizes a similar bipartite mechanism to recognize and regulate several Wnt-repressed targets, but through HMG and Helper sites whose sequences are distinct from those found in activated targets. The type of HMG and Helper sites is sufficient to direct activation or repression of Wnt regulated cis-regulatory modules, and protease digestion studies suggest that TCF/Pangolin adopts distinct conformations when bound to either HMG-Helper site pair. This repressive mechanism occurs in the fly lymph gland, the larval hematopoietic organ, where Wnt/β-catenin signaling controls prohemocytic differentiation. Our study provides a paradigm for direct repression of target gene expression by Wnt/β-catenin signaling and allosteric regulation of a transcription factor by DNA.

  9. Wnt-Mediated Repression via Bipartite DNA Recognition by TCF in the Drosophila Hematopoietic System

    PubMed Central

    Zhang, Chen U.; Blauwkamp, Timothy A.; Burby, Peter E.; Cadigan, Ken M.

    2014-01-01

    The Wnt/β-catenin signaling pathway plays many important roles in animal development, tissue homeostasis and human disease. Transcription factors of the TCF family mediate many Wnt transcriptional responses, promoting signal-dependent activation or repression of target gene expression. The mechanism of this specificity is poorly understood. Previously, we demonstrated that for activated targets in Drosophila, TCF/Pangolin (the fly TCF) recognizes regulatory DNA through two DNA binding domains, with the High Mobility Group (HMG) domain binding HMG sites and the adjacent C-clamp domain binding Helper sites. Here, we report that TCF/Pangolin utilizes a similar bipartite mechanism to recognize and regulate several Wnt-repressed targets, but through HMG and Helper sites whose sequences are distinct from those found in activated targets. The type of HMG and Helper sites is sufficient to direct activation or repression of Wnt regulated cis-regulatory modules, and protease digestion studies suggest that TCF/Pangolin adopts distinct conformations when bound to either HMG-Helper site pair. This repressive mechanism occurs in the fly lymph gland, the larval hematopoietic organ, where Wnt/β-catenin signaling controls prohemocytic differentiation. Our study provides a paradigm for direct repression of target gene expression by Wnt/β-catenin signaling and allosteric regulation of a transcription factor by DNA. PMID:25144371

  10. Molecular functions of the TLE tetramerization domain in Wnt target gene repression

    PubMed Central

    Chodaparambil, Jayanth V; Pate, Kira T; Hepler, Margretta R D; Tsai, Becky P; Muthurajan, Uma M; Luger, Karolin; Waterman, Marian L; Weis, William I

    2014-01-01

    Wnt signaling activates target genes by promoting association of the co-activator β-catenin with TCF/LEF transcription factors. In the absence of β-catenin, target genes are silenced by TCF-mediated recruitment of TLE/Groucho proteins, but the molecular basis for TLE/TCF-dependent repression is unclear. We describe the unusual three-dimensional structure of the N-terminal Q domain of TLE1 that mediates tetramerization and binds to TCFs. We find that differences in repression potential of TCF/LEFs correlates with their affinities for TLE-Q, rather than direct competition between β-catenin and TLE for TCFs as part of an activation–repression switch. Structure-based mutation of the TLE tetramer interface shows that dimers cannot mediate repression, even though they bind to TCFs with the same affinity as tetramers. Furthermore, the TLE Q tetramer, not the dimer, binds to chromatin, specifically to K20 methylated histone H4 tails, suggesting that the TCF/TLE tetramer complex promotes structural transitions of chromatin to mediate repression. PMID:24596249

  11. Helix-loop-helix transcription factors mediate activation and repression of the p75LNGFR gene.

    PubMed Central

    Chiaramello, A; Neuman, K; Palm, K; Metsis, M; Neuman, T

    1995-01-01

    Sequence analysis of rat and human low-affinity nerve growth factor receptor p75LNGFR gene promoter regions revealed a single E-box cis-acting element, located upstream of the major transcription start sites. Deletion analysis of the E-box sequence demonstrated that it significantly contributes to p75LNGFR promoter activity. This E box has a dual function; it mediates either activation or repression of the p75LNGFR promoter activity, depending on the interacting transcription factors. We showed that the two isoforms of the class A basic helix-loop-helix (bHLH) transcription factor ME1 (ME1a and ME1b), the murine homolog of the human HEB transcription factor, specifically repress p75LNGFR promoter activity. This repression can be released by coexpression of the HLH Id2 transcriptional regulator. In vitro analyses demonstrated that ME1a forms a stable complex with the p75LNGFR E box and likely competes with activating E-box-binding proteins. By using ME1a-overexpressing PC12 cells, we showed that the endogenous p75LNGFR gene is a target of ME1a repression. Together, these data demonstrate that the p75LNGFR E box and the interacting bHLH transcription factors are involved in the regulation of p75LNGFR gene expression. These results also show that class A bHLH transcription factors can repress and Id-like negative regulators can stimulate gene expression. PMID:7565756

  12. XIST repression in the absence of DNMT1 and DNMT3B.

    PubMed

    Vasques, Luciana R; Stabellini, Raquel; Xue, Fei; Tian, X Cindy; Soukoyan, Marina; Pereira, Lygia V

    2005-01-01

    X chromosome inactivation (XCI) in human and mice involves XIST/Xist gene expression from the inactive X (Xi) and repression from the active X (Xa). Repression of the XIST/Xist gene on the Xa has been associated with methylation of its 5' region. In mice, Dnmt1 has been shown to be involved in the methylation and transcriptional repression of Xist on Xa. We examined maintenance of XIST gene repression on Xa in HCT116 cell lines knockout for either DNMT1 or DNMT3B and for DNMT1 and DNMT3B simultaneously. Methylation of the XIST promoter and XIST transcriptional repression is sustained in DNMT1-, DNMT3B- and DNMT1/DNMT3B knockout cells. Despite global DNA demethylation, the double knockout cells present only partial demethylation of the XIST promoter, which is not sufficient for gene reactivation. In contrast, global DNA demethylation with 5-aza-2'-deoxycytidine leads to XIST expression. Therefore, in these human cells maintenance of XIST methylation is controlled differently than global genomic methylation and in the absence of both DNMT1 and DNMT3B.

  13. Plant NAC-type transcription factor proteins contain a NARD domain for repression of transcriptional activation.

    PubMed

    Hao, Yu-Jun; Song, Qing-Xin; Chen, Hao-Wei; Zou, Hong-Feng; Wei, Wei; Kang, Xu-Sheng; Ma, Biao; Zhang, Wan-Ke; Zhang, Jin-Song; Chen, Shou-Yi

    2010-10-01

    Plant-specific transcription factor NAC proteins play essential roles in many biological processes such as development, senescence, morphogenesis, and stress signal transduction pathways. In the NAC family, some members function as transcription activators while others act as repressors. In the present study we found that though the full-length GmNAC20 from soybean did not have transcriptional activation activity, the carboxy-terminal activation domain of GmNAC20 had high transcriptional activation activity in the yeast assay system. Deletion experiments revealed an active repression domain with 35 amino acids, named NARD (NAC Repression Domain), in the d subdomain of NAC DNA-binding domain. NARD can reduce the transcriptional activation ability of diverse transcription factors when fused to either the amino-terminal or the carboxy-terminal of the transcription factors. NARD-like sequences are also present in other NAC family members and they are functional repression domain when fused to VP16 in plant protoplast assay system. Mutation analysis of conserved amino acid residues in NARD showed that the hydrophobic LVFY motif may partially contribute to the repression function. It is hypothesized that the interactions between the repression domain NARD and the carboxy-terminal activation domain may finally determine the ability of NAC family proteins to regulate downstream gene expressions.

  14. The histone methyltransferase SETDB1 represses endogenous and exogenous retroviruses in B lymphocytes

    PubMed Central

    Collins, Patrick L.; Kyle, Katherine E.; Egawa, Takeshi; Shinkai, Yoichi; Oltz, Eugene M.

    2015-01-01

    Genome stability relies on epigenetic mechanisms that enforce repression of endogenous retroviruses (ERVs). Current evidence suggests that distinct chromatin-based mechanisms repress ERVs in cells of embryonic origin (histone methylation dominant) vs. more differentiated cells (DNA methylation dominant). However, the latter aspect of this model has not been tested. Remarkably, and in contrast to the prevailing model, we find that repressive histone methylation catalyzed by the enzyme SETDB1 is critical for suppression of specific ERV families and exogenous retroviruses in committed B-lineage cells from adult mice. The profile of ERV activation in SETDB1-deficient B cells is distinct from that observed in corresponding embryonic tissues, despite the loss of repressive chromatin modifications at all ERVs. We provide evidence that, on loss of SETDB1, ERVs are activated in a lineage-specific manner depending on the set of transcription factors available to target proviral regulatory elements. These findings have important implications for genome stability in somatic cells, as well as the interface between epigenetic repression and viral latency. PMID:26100872

  15. The MOX promoter in Hansenula polymorpha is ultrasensitive to glucose-mediated carbon catabolite repression.

    PubMed

    Dusny, Christian; Schmid, Andreas

    2016-09-01

    Redesigning biology towards specific purposes requires a functional understanding of genetic circuits. We present a quantitative in-depth study on the regulation of the methanol-specific MOX promoter system (PMOX) at the single-cell level. We investigated PMOX regulation in the methylotrophic yeast Hansenula (Ogataea) polymorpha with respect to glucose-mediated carbon catabolite repression. This promoter system is particularly delicate as the glucose as carbon and energy source in turn represses MOX promoter activity. Decoupling single cells from population activity revealed a hitherto underrated ultrasensitivity of the MOX promoter to glucose repression. Environmental control with single-cell technologies enabled quantitative insights into the balance between activation and repression of PMOX with respect to extracellular glucose concentrations. While population-based studies suggested full MOX promoter derepression at extracellular glucose concentrations of ∼1 g L(-1), we showed that glucose-mediated catabolite repression already occurs at concentrations as low as 5 × 10(-4) g L(-1) These findings demonstrate the importance of uncoupling single cells from populations for understanding the mechanisms of promoter regulation in a quantitative manner. PMID:27527102

  16. SIP1/ZEB2 induces EMT by repressing genes of different epithelial cell–cell junctions

    PubMed Central

    Vandewalle, Cindy; Comijn, Joke; De Craene, Bram; Vermassen, Petra; Bruyneel, Erik; Andersen, Henriette; Tulchinsky, Eugene; Van Roy, Frans; Berx, Geert

    2005-01-01

    SIP1/ZEB2 is a member of the δEF-1 family of two-handed zinc finger nuclear factors. The expression of these transcription factors is associated with epithelial mesenchymal transitions (EMT) during development. SIP1 is also expressed in some breast cancer cell lines and was detected in intestinal gastric carcinomas, where its expression is inversely correlated with that of E-cadherin. Here, we show that expression of SIP1 in human epithelial cells results in a clear morphological change from an epithelial to a mesenchymal phenotype. Induction of this epithelial dedifferentiation was accompanied by repression of several cell junctional proteins, with concomitant repression of their mRNA levels. Besides E-cadherin, other genes coding for crucial proteins of tight junctions, desmosomes and gap junctions were found to be transcriptionally regulated by the transcriptional repressor SIP1. Moreover, study of the promoter regions of selected genes by luciferase reporter assays and chromatin immunoprecipitation shows that repression is directly mediated by SIP1. These data indicate that, during epithelial dedifferentiation, SIP1 represses in a coordinated manner the transcription of genes coding for junctional proteins contributing to the dedifferentiated state; this repression occurs by a general mechanism mediated by Smad Interacting Protein 1 (SIP1)-binding sites. PMID:16314317

  17. The Sin3p PAH Domains Provide Separate Functions Repressing Meiotic Gene Transcription in Saccharomyces cerevisiae ▿

    PubMed Central

    Mallory, Michael J.; Law, Michael J.; Buckingham, Lela E.; Strich, Randy

    2010-01-01

    Meiotic genes in budding yeast are repressed during vegetative growth but are transiently induced during specific stages of meiosis. Sin3p represses the early meiotic gene (EMG) by bridging the DNA binding protein Ume6p to the histone deacetylase Rpd3p. Sin3p contains four paired amphipathic helix (PAH) domains, one of which (PAH3) is required for repressing several genes expressed during mitotic cell division. This report examines the roles of the PAH domains in mediating EMG repression during mitotic cell division and following meiotic induction. PAH2 and PAH3 are required for mitotic EMG repression, while electrophoretic mobility shift assays indicate that only PAH2 is required for stable Ume6p-promoter interaction. Unlike mitotic repression, reestablishing EMG repression following transient meiotic induction requires PAH3 and PAH4. In addition, the role of Sin3p in reestablishing repression is expanded to include additional loci that it does not control during vegetative growth. These findings indicate that mitotic and postinduction EMG repressions are mediated by two separate systems that utilize different Sin3p domains. PMID:20971827

  18. Prostate tumorigenesis induced by PTEN deletion involves estrogen receptor β repression.

    PubMed

    Mak, Paul; Li, Jiarong; Samanta, Sanjoy; Chang, Cheng; Jerry, D Joseph; Davis, Roger J; Leav, Irwin; Mercurio, Arthur M

    2015-03-31

    The role of ERβ in prostate cancer is unclear, although loss of ERβ is associated with aggressive disease. Given that mice deficient in ERβ do not develop prostate cancer, we hypothesized that ERβ loss occurs as a consequence of tumorigenesis caused by other oncogenic mechanisms and that its loss is necessary for tumorigenesis. In support of this hypothesis, we found that ERβ is targeted for repression in prostate cancer caused by PTEN deletion and that loss of ERβ is important for tumor formation. ERβ transcription is repressed by BMI-1, which is induced by PTEN deletion and important for prostate tumorigenesis. This finding provides a mechanism for how ERβ expression is regulated in prostate cancer. Repression of ERβ contributes to tumorigenesis because it enables HIF-1/VEGF signaling that sustains BMI-1 expression. These data reveal a positive feedback loop that is activated in response to PTEN loss and sustains BMI-1.

  19. An Introduction to CRISPR Technology for Genome Activation and Repression in Mammalian Cells.

    PubMed

    Du, Dan; Qi, Lei S

    2016-01-04

    CRISPR interference/activation (CRISPRi/a) technology provides a simple and efficient approach for targeted repression or activation of gene expression in the mammalian genome. It is highly flexible and programmable, using an RNA-guided nuclease-deficient Cas9 (dCas9) protein fused with transcriptional regulators for targeting specific genes to effect their regulation. Multiple studies have shown how this method is an effective way to achieve efficient and specific transcriptional repression or activation of single or multiple genes. Sustained transcriptional modulation can be obtained by stable expression of CRISPR components, which enables directed reprogramming of cell fate. Here, we introduce the basics of CRISPRi/a technology for genome repression or activation.

  20. A transient reversal of miRNA-mediated repression controls macrophage activation.

    PubMed

    Mazumder, Anup; Bose, Mainak; Chakraborty, Abhijit; Chakrabarti, Saikat; Bhattacharyya, Suvendra N

    2013-11-01

    In mammalian macrophages, the expression of a number of cytokines is regulated by miRNAs. Upon macrophage activation, proinflammatory cytokine mRNAs are translated, although the expression of miRNAs targeting these mRNAs remains largely unaltered. We show that there is a transient reversal of miRNA-mediated repression during the early phase of the inflammatory response in macrophages, which leads to the protection of cytokine mRNAs from miRNA-mediated repression. This derepression occurs through Ago2 phosphorylation, which results in its impaired binding to miRNAs and to the corresponding target mRNAs. Macrophages expressing a mutant, non-phosphorylatable AGO2--which remains bound to miRNAs during macrophage activation--have a weakened inflammatory response and fail to prevent parasite invasion. These findings highlight the relevance of the transient relief of miRNA repression for macrophage function.

  1. Hairy and Groucho mediate the action of juvenile hormone receptor Methoprene-tolerant in gene repression.

    PubMed

    Saha, Tusar T; Shin, Sang Woon; Dou, Wei; Roy, Sourav; Zhao, Bo; Hou, Yuan; Wang, Xue-Li; Zou, Zhen; Girke, Thomas; Raikhel, Alexander S

    2016-02-01

    The arthropod-specific juvenile hormone (JH) controls numerous essential functions. Its involvement in gene activation is known to be mediated by the transcription factor Methoprene-tolerant (Met), which turns on JH-controlled genes by directly binding to E-box-like motifs in their regulatory regions. However, it remains unclear how JH represses genes. We used the Aedes aegypti female mosquito, in which JH is necessary for reproductive maturation, to show that a repressor, Hairy, is required for the gene-repressive action of JH and Met. The RNA interference (RNAi) screen for Met and Hairy in the Aedes female fat body revealed a large cohort of Met- and Hairy-corepressed genes. Analysis of selected genes from this cohort demonstrated that they are repressed by JH, but RNAi of either Met or Hairy renders JH ineffective in repressing these genes in an in vitro fat-body culture assay. Moreover, this JH action was prevented by the addition of the translational inhibitor cycloheximide (CHX) to the culture, indicating the existence of an indirect regulatory hierarchy. The lack of Hairy protein in the CHX-treated tissue was verified using immunoblot analysis, and the upstream regions of Met/Hairy-corepressed genes were shown to contain common binding motifs that interact with Hairy. Groucho (gro) RNAi silencing phenocopied the effect of Hairy RNAi knockdown, indicating that it is involved in the JH/Met/Hairy hierarchy. Finally, the requirement of Hairy and Gro for gene repression was confirmed in a cell transfection assay. Thus, our study has established that Hairy and its cofactor Gro mediate the repressive function of JH and Met. PMID:26744312

  2. Hairy and Groucho mediate the action of juvenile hormone receptor Methoprene-tolerant in gene repression

    PubMed Central

    Saha, Tusar T.; Shin, Sang Woon; Dou, Wei; Roy, Sourav; Zhao, Bo; Hou, Yuan; Wang, Xue-Li; Zou, Zhen; Girke, Thomas; Raikhel, Alexander S.

    2016-01-01

    The arthropod-specific juvenile hormone (JH) controls numerous essential functions. Its involvement in gene activation is known to be mediated by the transcription factor Methoprene-tolerant (Met), which turns on JH-controlled genes by directly binding to E-box–like motifs in their regulatory regions. However, it remains unclear how JH represses genes. We used the Aedes aegypti female mosquito, in which JH is necessary for reproductive maturation, to show that a repressor, Hairy, is required for the gene-repressive action of JH and Met. The RNA interference (RNAi) screen for Met and Hairy in the Aedes female fat body revealed a large cohort of Met- and Hairy-corepressed genes. Analysis of selected genes from this cohort demonstrated that they are repressed by JH, but RNAi of either Met or Hairy renders JH ineffective in repressing these genes in an in vitro fat-body culture assay. Moreover, this JH action was prevented by the addition of the translational inhibitor cycloheximide (CHX) to the culture, indicating the existence of an indirect regulatory hierarchy. The lack of Hairy protein in the CHX-treated tissue was verified using immunoblot analysis, and the upstream regions of Met/Hairy-corepressed genes were shown to contain common binding motifs that interact with Hairy. Groucho (gro) RNAi silencing phenocopied the effect of Hairy RNAi knockdown, indicating that it is involved in the JH/Met/Hairy hierarchy. Finally, the requirement of Hairy and Gro for gene repression was confirmed in a cell transfection assay. Thus, our study has established that Hairy and its cofactor Gro mediate the repressive function of JH and Met. PMID:26744312

  3. Repressive BMP2 gene regulatory elements near the BMP2 promoter

    SciTech Connect

    Jiang, Shan; Chandler, Ronald L.; Fritz, David T.; Mortlock, Douglas P.; Rogers, Melissa B.

    2010-02-05

    The level of bone morphogenetic protein 2 (BMP2) profoundly influences essential cell behaviors such as proliferation, differentiation, apoptosis, and migration. The spatial and temporal pattern of BMP2 synthesis, particular in diverse embryonic cells, is highly varied and dynamic. We have identified GC-rich sequences within the BMP2 promoter region that strongly repress gene expression. These elements block the activity of a highly conserved, osteoblast enhancer in response to FGF2 treatment. Both positive and negative gene regulatory elements control BMP2 synthesis. Detecting and mapping the repressive motifs is essential because they impede the identification of developmentally regulated enhancers necessary for normal BMP2 patterns and concentration.

  4. Repression of CIITA by the Epstein-Barr virus transcription factor Zta is independent of its dimerization and DNA binding.

    PubMed

    Balan, Nicolae; Osborn, Kay; Sinclair, Alison J

    2016-03-01

    Repression of the cellular CIITA gene is part of the immune evasion strategy of the γherpes virus Epstein-Barr virus (EBV) during its lytic replication cycle in B-cells. In part, this is mediated through downregulation of MHC class II gene expression via the targeted repression of CIITA, the cellular master regulator of MHC class II gene expression. This repression is achieved through a reduction in CIITA promoter activity, initiated by the EBV transcription and replication factor, Zta (BZLF1, EB1, ZEBRA). Zta is the earliest gene expressed during the lytic replication cycle. Zta interacts with sequence-specific elements in promoters, enhancers and the replication origin (ZREs), and also modulates gene expression through interaction with cellular transcription factors and co-activators. Here, we explore the requirements for Zta-mediated repression of the CIITA promoter. We find that repression by Zta is specific for the CIITA promoter and can be achieved in the absence of other EBV genes. Surprisingly, we find that the dimerization region of Zta is not required to mediate repression. This contrasts with an obligate requirement of this region to correctly orientate the DNA contact regions of Zta to mediate activation of gene expression through ZREs. Additional support for the model that Zta represses the CIITA promoter without direct DNA binding comes from promoter mapping that shows that repression does not require the presence of a ZRE in the CIITA promoter. PMID:26653871

  5. Neuron type-specific miRNA represses two broadly expressed genes to modulate an avoidance behavior in C. elegans

    PubMed Central

    Drexel, Tanja; Mahofsky, Katharina; Latham, Richard; Zimmer, Manuel

    2016-01-01

    Two broad gene classes are distinguished within multicellular organisms: cell type-specific genes, which confer particular cellular properties, and ubiquitous genes that support general cellular functions. However, certain so-called ubiquitous genes show functionally relevant cell type-specific repression. How such repression is achieved is poorly understood. MicroRNAs (miRNAs) are repressors, many of which are expressed with high cell type specificity. Here we show that mir-791, expressed exclusively in the CO2-sensing neurons in Caenorhabditis elegans, represses two otherwise broadly expressed genes. This repression is necessary for normal neuronal function and behavior of the animals toward CO2. miRNA-mediated repression of broadly transcribed genes is a previously unappreciated strategy for cellular specialization. PMID:27688400

  6. Decitabine represses osteoclastogenesis through inhibition of RANK and NF-κB.

    PubMed

    Guan, Hanfeng; Mi, Baoguo; Li, Yong; Wu, Wei; Tan, Peng; Fang, Zhong; Li, Jing; Zhang, Yong; Li, Feng

    2015-05-01

    DNA methylation is essential for maintenance of stable repression of gene transcription during differentiation and tumorigenesis. Demethylating reagents including decitabine could release the repression, leading to perturbed transcription program. Recently others and we showed that, in B cell lymphomas, decitabine repressed B cell specific gene transcription and activated NF-κB signaling, causing decreased expression of translocated oncogenes including MYC and attenuated tumor cell proliferation. During osteoclastogenesis, changes in DNA methylation occurred in numerous genes, implicating important roles for DNA methylation in osteoclastogenesis. In the present study, we found that decitabine inhibited osteoclastogenesis. The inhibitory effect could be at least partially attributed to reduced expression of multiple osteoclast specific genes including RANK by decitabine. Moreover, decitabine inhibited activity of NF-κB, AP-1 and extracellular signal-regulated kinase (ERK), but not PI3K/Akt pathway. In vivo, using ovariectomized mouse as a model, we observed that decitabine reduced the osteoclast activity and bone loss. In conclusion, our findings demonstrated that decitabine was an inhibitor of osteoclastogenesis by repression of osteoclast specific transcription program including the RANK, NF-κB and AP-1 pathways. DNA methylation might be indispensable for osteoclastogenesis. The use of decitabine could represent a novel strategy in treatment of diseases associated with increased osteoclast activity.

  7. Clinical Characteristics of Adults Reporting Repressed, Recovered, or Continuous Memories of Childhood Sexual Abuse

    ERIC Educational Resources Information Center

    McNally, Richard J.; Perlman, Carol A.; Ristuccia, Carel S.; Clancy, Susan A.

    2006-01-01

    The authors assessed women and men who either reported continuous memories of their childhood sexual abuse (CSA, n = 92), reported recovering memories of CSA (n = 38), reported believing they harbored repressed memories of CSA (n = 42), or reported never having been sexually abused (n = 36). Men and women were indistinguishable on all clinical and…

  8. SOD1 integrates signals from oxygen and glucose to repress respiration.

    PubMed

    Reddi, Amit R; Culotta, Valeria C

    2013-01-17

    Cu/Zn superoxide dismutase (SOD1) is an abundant enzyme that has been best studied as a regulator of antioxidant defense. Using the yeast Saccharomyces cerevisiae, we report that SOD1 transmits signals from oxygen and glucose to repress respiration. The mechanism involves SOD1-mediated stabilization of two casein kinase 1-gamma (CK1γ) homologs, Yck1p and Yck2p, required for respiratory repression. SOD1 binds a C-terminal degron we identified in Yck1p/Yck2p and promotes kinase stability by catalyzing superoxide conversion to peroxide. The effects of SOD1 on CK1γ stability are also observed with mammalian SOD1 and CK1γ and in a human cell line. Therefore, in a single circuit, oxygen, glucose, and reactive oxygen can repress respiration through SOD1/CK1γ signaling. Our data therefore may provide mechanistic insight into how rapidly proliferating cells and many cancers accomplish glucose-mediated repression of respiration in favor of aerobic glycolysis.

  9. The neuronal repellent SLIT2 is a target for repression by EZH2 in prostate cancer.

    PubMed

    Yu, J; Cao, Q; Yu, J; Wu, L; Dallol, A; Li, J; Chen, G; Grasso, C; Cao, X; Lonigro, R J; Varambally, S; Mehra, R; Palanisamy, N; Wu, J Y; Latif, F; Chinnaiyan, A M

    2010-09-30

    The neuronal repellent SLIT2 is repressed in a number of cancer types primarily through promoter hypermethylation. SLIT2, however, has not been studied in prostate cancer. Through genome-wide location analysis we identified SLIT2 as a target of polycomb group (PcG) protein EZH2. The EZH2-containing polycomb repressive complexes bound to the SLIT2 promoter inhibiting its expression. SLIT2 was downregulated in a majority of metastatic prostate tumors, showing a negative correlation with EZH2. This repressed expression could be restored by methylation inhibitors or EZH2-suppressing compounds. In addition, a low level of SLIT2 expression was associated with aggressive prostate, breast and lung cancers. Functional assays showed that SLIT2 inhibited prostate cancer cell proliferation and invasion. Thus, this study showed for the first time the epigenetic silencing of SLIT2 in prostate tumors, and supported SLIT2 as a potential biomarker for aggressive solid tumors. Importantly, PcG-mediated repression may serve as a precursor for the silencing of SLIT2 by DNA methylation in cancer.

  10. Hypoxia induces a novel signature of chromatin modifications and global repression of transcription.

    PubMed

    Johnson, Amber Buescher; Denko, Nicholas; Barton, Michelle Craig

    2008-04-01

    Tumor cells respond to the harsh hypoxic microenvironment, in part, by transcriptional regulation of specific target genes. We found that hypoxia-mediated activation of selected genes occurs amidst widespread repression of transcription that is neither cell type-specific nor HIF-1-dependent. Despite overall repression, hypoxia induces a pool of histone modifications typically associated with transcriptional activation or repression. Chromatin immunoprecipitation analyses showed that this global mixture of hypoxia-modified histones is sorted in a gene-specific manner to correlate with transcriptional response to hypoxia. Exceptions to this were unexpected increases in H3K4me3 levels, typically associated with transcriptional activation, and decreased H3K27me3 levels, generally a marker of transcriptional silencing, at core promoters of both hypoxia-activated and -repressed genes. These data suggest that a novel signature of chromatin modifications is induced under hypoxic stress, which may play a role in gene regulatory switches active in proliferating tumor cells undergoing cycles of hypoxia and reoxygenation.

  11. Hypoxia induces a novel signature of chromatin modifications and global repression of transcription

    PubMed Central

    Johnson, Amber Buescher; Denko, Nicholas; Barton, Michelle Craig

    2008-01-01

    Tumor cells respond to the harsh hypoxic microenvironment, in part, by transcriptional regulation of specific target genes. We found that hypoxia-mediated activation of selected genes occurs amidst widespread repression of transcription that is neither cell type-specific nor HIF-1-dependent. Despite overall repression, hypoxia induces a pool of histone modifications typically associated with transcriptional activation or repression. Chromatin immunoprecipitation analyses showed that this global mixture of hypoxia-modified histones is sorted in a gene-specific manner to correlate with transcriptional response to hypoxia. Exceptions to this were unexpected increases in H3K4me3 levels, typically associated with transcriptional activation, and decreased H3K27me3 levels, generally a marker of transcriptional silencing, at core promoters of both hypoxia-activated and -repressed genes. These data suggest that a novel signature of chromatin modifications is induced under hypoxic stress, which may play a role in gene regulatory switches active in proliferating tumor cells undergoing cycles of hypoxia and reoxygenation. PMID:18294659

  12. Review of the Literature Regarding the Repression of Memories of Childhood Sexual Abuse.

    ERIC Educational Resources Information Center

    Barber, Betsy A.

    Published empirical research on the repression of memories of childhood sexual abuse is limited at the present time, and the quality and usefulness of the research varies with the methodology, research design, statistical analyses, and researcher bias. This literature review discusses at length a 1987 study by J. H. Herman and E. Schatzow and 1994…

  13. Effect of anthranilic acid on the catabolite repression of a Drosophila amylase gene in E. coli

    SciTech Connect

    Stevens, S.M.; Moehring, J.M.; Chernin, M.I.

    1987-05-01

    A Drosophila pseudoobscura amylase pseudogene cloned in Escherichia coli is expressed at high levels. The expression of this pseudogene is repressed when glucose (0.5% final conc) is added to a starch minimal medium culture of E. coli cells that contain the amylase plasmid pAMY17F. Addition of anthranilic acid (7 mM final conc.) to catabolite repressed cells acts like adenosine 3',5' cyclic monophosphate (cAMP) by derepressing the amylase pseudogene at the promoter. This is consistent with the Metabolite Gene Regulation (MGR) model proposed by Kline et al. which suggests that small molecules can circumvent the necessity for cAMP. Catabolite repression of the amylase structural gene of D. pseudoobscura has been previously shown. This would suggest that the amylase pseudogene expression in E. coli is either from a Drosophila structural gene promoter co-cloned with the pseudogene or a catabolite repressible E. coli promoter placed in the proper orientation and reading frame during the rearrangement of pAMY17F.

  14. The natural product peiminine represses colorectal carcinoma tumor growth by inducing autophagic cell death

    SciTech Connect

    Lyu, Qing; Tou, Fangfang; Su, Hong; Wu, Xiaoyong; Chen, Xinyi; Zheng, Zhi

    2015-06-19

    Autophagy is evolutionarily conservative in eukaryotic cells that engulf cellular long-lived proteins and organelles, and it degrades the contents through fusion with lysosomes, via which the cell acquires recycled building blocks for the synthesis of new molecules. In this study, we revealed that peiminine induces cell death and enhances autophagic flux in colorectal carcinoma HCT-116 cells. We determined that peiminine enhances the autophagic flux by repressing the phosphorylation of mTOR through inhibiting upstream signals. Knocking down ATG5 greatly reduced the peiminine-induced cell death in wild-type HCT-116 cells, while treating Bax/Bak-deficient cells with peiminine resulted in significant cell death. In summary, our discoveries demonstrated that peiminine represses colorectal carcinoma cell proliferation and cell growth by inducing autophagic cell death. - Highlights: • Peiminine induces autophagy and upregulates autophagic flux. • Peiminine represses colorectal carcinoma tumor growth. • Peiminine induces autophagic cell death. • Peiminine represses mTOR phosphorylation by influencing PI3K/Akt and AMPK pathway.

  15. Tumor FOXP3 represses the expression of long noncoding RNA 7SL.

    PubMed

    Yang, Yanhui; Cheng, Jingli; Ren, Huizhu; Zhao, Hui; Gong, Wei; Shan, Chunyan

    2016-04-01

    The long noncoding RNA 7SL was over-expressed in tumor cells to promote cell growth through repressing translation of P53. However, the regulatory mechanism of 7SL remains to be defined. FOXP3 was identified as a suppressor in several tumors in addition to be a marker of regulatory T cells. In this study, we detected that over-expression of FOXP3 repressed the transcription of 7SL RNA and contributed to inhibiting tumor growth. Knock down of FOXP3 in MCF-10A normal mammary breast cells up-regulated the transcription of 7SL RNA. Chromatin Immuno-precipitation (ChIP) analysis showed that FOXP3 directly bound to the Forkhead/HNF-3 domain DNA binding sites (-789 to -795) relative to the transcription start site. Meanwhile, Luciferase analysis showed that FOXP3 repressed the full-length 7SL promoter activity, but this suppressive effect was reversed after mutation of the FOXP3 binding site. Further studies showed that FOXP3 promoted the expression of P53 at translational levels through repressing 7SL RNA. In conclusion, this study suggests that 7SL RNA is a direct target of FOXP3 and may be involved in the formation of FOXP3/P53 feedback loop. PMID:26718402

  16. Daxx represses RelB target promoters via DNA methyltransferase recruitment and DNA hypermethylation

    PubMed Central

    Puto, Lorena A.; Reed, John C.

    2008-01-01

    The apoptosis-modulating protein Daxx functions as a transcriptional repressor that binds to and suppresses the activity of nuclear factor-κB member RelB, among other transcription factors. The mechanism by which Daxx represses RelB target genes remains elusive. In this report, we demonstrate that Daxx controls epigenetic silencing of RelB target genes by DNA methylation. Daxx potently represses the RelB target genes dapk1, dapk3, c-flip, and birc3 (ciap2) at both the mRNA and protein levels. Recruitment of Daxx to target gene promoters, and its ability to repress them, is RelB-dependent, as shown by experiments using relB−/− cells. Importantly, methylation of target promoters is decreased in daxx−/− cells compared with daxx+/+ cells, and stable transfection of daxx−/− cells with Daxx restores DNA methylation. Furthermore, Daxx recruits DNA methyl transferase 1 (Dnmt1) to target promoters, resulting in synergistic repression. The observation that Daxx functions to target DNA methyltransferases onto RelB target sites in the genome provides a rare example of a gene-specific mechanism for epigenetic silencing. Given the documented role of several of the RelB-regulated genes in diseases, particularly cancer, the findings have implications for developing therapeutic strategies based on epigenetic-modifying drugs. PMID:18413714

  17. Pluripotency factors and Polycomb Group proteins repress aryl hydrocarbon receptor expression in murine embryonic stem cells.

    PubMed

    Ko, Chia-I; Wang, Qin; Fan, Yunxia; Xia, Ying; Puga, Alvaro

    2014-01-01

    The aryl hydrocarbon receptor (AHR) is a transcription factor and environmental sensor that regulates expression of genes involved in drug-metabolism and cell cycle regulation. Chromatin immunoprecipitation analyses, Ahr ablation in mice and studies with orthologous genes in invertebrates suggest that AHR may also play a significant role in embryonic development. To address this hypothesis, we studied the regulation of Ahr expression in mouse embryonic stem cells and their differentiated progeny. In ES cells, interactions between OCT3/4, NANOG, SOX2 and Polycomb Group proteins at the Ahr promoter repress AHR expression, which can also be repressed by ectopic expression of reprogramming factors in hepatoma cells. In ES cells, unproductive RNA polymerase II binds at the Ahr transcription start site and drives the synthesis of short abortive transcripts. Activation of Ahr expression during differentiation follows from reversal of repressive marks in Ahr promoter chromatin, release of pluripotency factors and PcG proteins, binding of Sp factors, establishment of histone marks of open chromatin, and engagement of active RNAPII to drive full-length RNA transcript elongation. Our results suggest that reversible Ahr repression in ES cells holds the gene poised for expression and allows for a quick switch to activation during embryonic development.

  18. OprD Repression upon Metal Treatment Requires the RNA Chaperone Hfq in Pseudomonas aeruginosa

    PubMed Central

    Ducret, Verena; Gonzalez, Manuel R.; Scrignari, Tiziana; Perron, Karl

    2016-01-01

    The metal-specific CzcRS two-component system in Pseudomonas aeruginosa is involved in the repression of the OprD porin, causing in turn carbapenem antibiotic resistance in the presence of high zinc concentration. It has also been shown that CzcR is able to directly regulate the expression of multiple genes including virulence factors. CzcR is therefore an important regulator connecting (i) metal response, (ii) pathogenicity and (iii) antibiotic resistance in P. aeruginosa. Recent data have suggested that other regulators could negatively control oprD expression in the presence of zinc. Here we show that the RNA chaperone Hfq is a key factor acting independently of CzcR for the repression of oprD upon Zn treatment. Additionally, we found that an Hfq-dependent mechanism is necessary for the localization of CzcR to the oprD promoter, mediating oprD transcriptional repression. Furthermore, in the presence of Cu, CopR, the transcriptional regulator of the CopRS two-component system also requires Hfq for oprD repression. Altogether, these results suggest important roles for this RNA chaperone in the context of environment-sensing and antibiotic resistance in P. aeruginosa. PMID:27706108

  19. Repressive Adaptive Style and Self-Reported Psychological Functioning in Adolescent Cancer Survivors

    ERIC Educational Resources Information Center

    Erickson, Sarah J.; Gerstle, Melissa; Montague, Erica Q.

    2008-01-01

    Low levels of posttraumatic stress disorder (PTSD), posttraumatic stress symptoms (PTSS), and psychosocial distress have been reported in pediatric cancer survivors. One explanation is the relatively high prevalence of the repressive adaptive style (low distress, high restraint) in this population. We investigated the relationship between this…

  20. Universities in the Business of Repression: The Academic-Military-Industrial Complex and Central America.

    ERIC Educational Resources Information Center

    Feldman, Jonathan

    This book presents the thesis that U.S. universities have become part of an academic-military-industrial complex that support repression and murder in Central America. Part 1 explains how U.S. policies have been based on murder in Central America and examines the responsibility of transnational corporations and U.S. war planners in this…

  1. Direct Repression of Evening Genes by CIRCADIAN CLOCK-ASSOCIATED1 in the Arabidopsis Circadian Clock.

    PubMed

    Kamioka, Mari; Takao, Saori; Suzuki, Takamasa; Taki, Kyomi; Higashiyama, Tetsuya; Kinoshita, Toshinori; Nakamichi, Norihito

    2016-03-01

    The circadian clock is a biological timekeeping system that provides organisms with the ability to adapt to day-night cycles. Timing of the expression of four members of the Arabidopsis thaliana PSEUDO-RESPONSE REGULATOR(PRR) family is crucial for proper clock function, and transcriptional control of PRRs remains incompletely defined. Here, we demonstrate that direct regulation of PRR5 by CIRCADIAN CLOCK-ASSOCIATED1 (CCA1) determines the repression state of PRR5 in the morning. Chromatin immunoprecipitation followed by deep sequencing (ChIP-seq) analyses indicated that CCA1 associates with three separate regions upstream of PRR5 CCA1 and its homolog LATE ELONGATED HYPOCOTYL (LHY) suppressed PRR5 promoter activity in a transient assay. The regions bound by CCA1 in the PRR5 promoter gave rhythmic patterns with troughs in the morning, when CCA1 and LHY are at high levels. Furthermore,ChIP-seq revealed that CCA1 associates with at least 449 loci with 863 adjacent genes. Importantly, this gene set contains genes that are repressed but upregulated incca1 lhy double mutants in the morning. This study shows that direct binding by CCA1 in the morning provides strong repression of PRR5, and repression by CCA1 also temporally regulates an evening-expressed gene set that includes PRR5. PMID:26941090

  2. Conservation of uORF repressiveness and sequence features in mouse, human and zebrafish

    PubMed Central

    Chew, Guo-Liang; Pauli, Andrea; Schier, Alexander F.

    2016-01-01

    Upstream open reading frames (uORFs) are ubiquitous repressive genetic elements in vertebrate mRNAs. While much is known about the regulation of individual genes by their uORFs, the range of uORF-mediated translational repression in vertebrate genomes is largely unexplored. Moreover, it is unclear whether the repressive effects of uORFs are conserved across species. To address these questions, we analyse transcript sequences and ribosome profiling data from human, mouse and zebrafish. We find that uORFs are depleted near coding sequences (CDSes) and have initiation contexts that diminish their translation. Linear modelling reveals that sequence features at both uORFs and CDSes modulate the translation of CDSes. Moreover, the ratio of translation over 5′ leaders and CDSes is conserved between human and mouse, and correlates with the number of uORFs. These observations suggest that the prevalence of vertebrate uORFs may be explained by their conserved role in repressing CDS translation. PMID:27216465

  3. A Symptom-Focused Hypnotic Approach to Accessing and Processing Previously Repressed/Dissociated Memories.

    ERIC Educational Resources Information Center

    Ratican, Kathleen L.

    1996-01-01

    The kinesthetic track back technique accesses the origins of current symptoms and may uncover previously repressed/dissociated material, if such material exists in the client's unconscious mind, is relevant to the symptoms, and is ready to be processed consciously. Case examples are given to illustrate proper use of this technique. (LSR)

  4. Repression of mesodermal fate by foxa, a key endoderm regulator of the sea urchin embryo.

    PubMed

    Oliveri, Paola; Walton, Katherine D; Davidson, Eric H; McClay, David R

    2006-11-01

    The foxa gene is an integral component of the endoderm specification subcircuit of the endomesoderm gene regulatory network in the Strongylocentrotus purpuratus embryo. Its transcripts become confined to veg2, then veg1 endodermal territories, and, following gastrulation, throughout the gut. It is also expressed in the stomodeal ectoderm. gatae and otx genes provide input into the pregastrular regulatory system of foxa, and Foxa represses its own transcription, resulting in an oscillatory temporal expression profile. Here, we report three separate essential functions of the foxa gene: it represses mesodermal fate in the veg2 endomesoderm; it is required in postgastrular development for the expression of gut-specific genes; and it is necessary for stomodaeum formation. If its expression is reduced by a morpholino, more endomesoderm cells become pigment and other mesenchymal cell types, less gut is specified, and the larva has no mouth. Experiments in which blastomere transplantation is combined with foxa MASO treatment demonstrate that, in the normal endoderm, a crucial role of Foxa is to repress gcm expression in response to a Notch signal, and hence to repress mesodermal fate. Chimeric recombination experiments in which veg2, veg1 or ectoderm cells contained foxa MASO show which region of foxa expression controls each of the three functions. These experiments show that the foxa gene is a component of three distinct embryonic gene regulatory networks.

  5. Personality and Psychopathology in African Unaccompanied Refugee Minors: Repression, Resilience and Vulnerability

    ERIC Educational Resources Information Center

    Huemer, Julia; Volkl-Kernstock, Sabine; Karnik, Niranjan; Denny, Katherine G.; Granditsch, Elisabeth; Mitterer, Michaela; Humphreys, Keith; Plattner, Belinda; Friedrich, Max; Shaw, Richard J.; Steiner, Hans

    2013-01-01

    Examining personality and psychopathological symptoms among unaccompanied refugee minors (URMs), we measured intra-individual dimensions (repression and correlates thereof) usually associated with resilience. Forty-one URMs completed the Weinberger Adjustment Inventory (WAI), assessing personality, and the Youth Self-Report (YSR), describing…

  6. Insights into GATA-1 Mediated Gene Activation versus Repression via Genome-wide Chromatin Occupancy Analysis

    PubMed Central

    Yu, Ming; Riva, Laura; Xie, Huafeng; Schindler, Yocheved; Moran, Tyler B.; Cheng, Yong; Yu, Duonan; Hardison, Ross; Weiss, Mitchell J; Orkin, Stuart H.; Bernstein, Bradley E.; Fraenkel, Ernest; Cantor, Alan B.

    2009-01-01

    Summary The transcription factor GATA-1 is required for terminal erythroid maturation and functions as an activator or repressor depending on gene context. Yet its in vivo site selectivity and ability to distinguish between activated versus repressed genes remain incompletely understood. In this study, we performed GATA-1 ChIP-seq in erythroid cells and compared it to GATA-1 induced gene expression changes. Bound and differentially expressed genes contain a greater number of GATA binding motifs, a higher frequency of palindromic GATA sites, and closer occupancy to the transcriptional start site versus non-differentially expressed genes. Moreover, we show that the transcription factor Zbtb7a occupies GATA-1 bound regions of some direct GATA-1 target genes, that the presence of SCL/TAL1 helps distinguish transcriptional activation versus repression, and that Polycomb Repressive Complex 2 (PRC2) is involved in epigenetic silencing of a subset of GATA-1 repressed genes. These data provide insights into GATA-1 mediated gene regulation in vivo. PMID:19941827

  7. Opposing LSD1 complexes function in developmental gene activation and repression programmes.

    PubMed

    Wang, Jianxun; Scully, Kathleen; Zhu, Xiaoyan; Cai, Ling; Zhang, Jie; Prefontaine, Gratien G; Krones, Anna; Ohgi, Kenneth A; Zhu, Ping; Garcia-Bassets, Ivan; Liu, Forrest; Taylor, Havilah; Lozach, Jean; Jayes, Friederike L; Korach, Kenneth S; Glass, Christopher K; Fu, Xiang-Dong; Rosenfeld, Michael G

    2007-04-19

    Precise control of transcriptional programmes underlying metazoan development is modulated by enzymatically active co-regulatory complexes, coupled with epigenetic strategies. One thing that remains unclear is how specific members of histone modification enzyme families, such as histone methyltransferases and demethylases, are used in vivo to simultaneously orchestrate distinct developmental gene activation and repression programmes. Here, we report that the histone lysine demethylase, LSD1--a component of the CoREST-CtBP co-repressor complex--is required for late cell-lineage determination and differentiation during pituitary organogenesis. LSD1 seems to act primarily on target gene activation programmes, as well as in gene repression programmes, on the basis of recruitment of distinct LSD1-containing co-activator or co-repressor complexes. LSD1-dependent gene repression programmes can be extended late in development with the induced expression of ZEB1, a Krüppel-like repressor that can act as a molecular beacon for recruitment of the LSD1-containing CoREST-CtBP co-repressor complex, causing repression of an additional cohort of genes, such as Gh, which previously required LSD1 for activation. These findings suggest that temporal patterns of expression of specific components of LSD1 complexes modulate gene regulatory programmes in many mammalian organs.

  8. Lifting DELLA repression of Arabidopsis seed germination by nonproteolytic gibberellin signaling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    DELLA repression of Arabidopsis seed germination can be lifted through the ubiquitin-proteasome pathway and proteolysis-independent GA signaling. GA-binding to the GID1 (GIBBERELLIN-INSENSITIVE DWARF1) GA receptors stimulates GID1-GA-DELLA complex formation which in turn triggers DELLA protein ubiq...

  9. Feedback circuitry between miR-218 repression and RTK activation in Glioblastoma

    PubMed Central

    Mathew, Lijoy K; Huangyang, Peiwei; Mucaj, Vera; Lee, Samuel S.; Skuli, Nicolas; Eisinger-Mathason, T.S. Karin; Biju, Kevin; Li, Bo; Venneti, Sriram; Lal, Priti; Lathia, Justin D; Rich, Jeremy N; Keith, Brian; Simon, M Celeste

    2015-01-01

    Receptor tyrosine kinase (RTK) pathway signaling plays a central role in the growth and progression of Glioblastoma (GBM), a highly aggressive group of brain tumors. We recently reported that miR-218 repression, an essentially uniform feature of human GBM, directly promotes RTK hyperactivation by increasing the expression of key positive signaling effectors, including EGFR, PLCγ1, PIK3CA and ARAF (1). However, enhanced RTK signaling is known to activate compensatory inhibitory feedback mechanisms in both normal and cancer cells. We demonstrate here that miR-218 repression in GBM cells also increases the abundance of additional upstream and downstream signaling mediators, including PDGFRα, RSK2, and S6K1, which collectively function to alleviate inhibitory RTK feedback regulation. In turn, RTK signaling suppresses miR-218 expression via STAT3, which binds directly to the miR-218 locus, along with BCLAF1, to repress its expression. These data identify novel interacting feedback loops by which miR-218 repression promotes increased RTK signaling in high-grade gliomas. PMID:25943352

  10. Developmental control of gene copy number by repression of replication initiation and fork progression.

    PubMed

    Sher, Noa; Bell, George W; Li, Sharon; Nordman, Jared; Eng, Thomas; Eaton, Matthew L; Macalpine, David M; Orr-Weaver, Terry L

    2012-01-01

    Precise DNA replication is crucial for genome maintenance, yet this process has been inherently difficult to study on a genome-wide level in untransformed differentiated metazoan cells. To determine how metazoan DNA replication can be repressed, we examined regions selectively under-replicated in Drosophila polytene salivary glands, and found they are transcriptionally silent and enriched for the repressive H3K27me3 mark. In the first genome-wide analysis of binding of the origin recognition complex (ORC) in a differentiated metazoan tissue, we find that ORC binding is dramatically reduced within these large domains, suggesting reduced initiation as one mechanism leading to under-replication. Inhibition of replication fork progression by the chromatin protein SUUR is an additional repression mechanism to reduce copy number. Although repressive histone marks are removed when SUUR is mutated and copy number restored, neither transcription nor ORC binding is reinstated. Tethering of the SUUR protein to a specific site is insufficient to block replication, however. These results establish that developmental control of DNA replication, at both the initiation and elongation stages, is a mechanism to change gene copy number during differentiation.

  11. The use of subliminal psychodynamic activation in the study of repression.

    PubMed

    Geisler, C

    1986-10-01

    Female undergraduates (N = 33) selected for the presence of high sexual guilt were divided into two groups. One group evidenced a high degree of personality development from which it was inferred that they were prone toward (a) the use of repression rather than more primitive defenses and (b) oedipal rather than preoedipal conflict. The second group evidenced a lesser degree of personality development, and hence the above inferences did not apply. The subliminal psychodynamic activation method was used with both groups to investigate the effects on repression of intensifying and diminishing unconscious conflict over sexual wishes. Subjects were exposed to the verbal stimuli "LOVING DADDY IS WRONG" (conflict intensifying), "LOVING DADDY IS OK" (conflict reducing), and "PEOPLE ARE WALKING" (neutral control), each accompanied by a congruent picture both before (in one condition) and after (in another) a recall test of both neutral and sexual material. The conflict-reduction condition did not affect memory of the passages, but the conflict-intensification condition did for the group with the greater degree of personality development, when this condition was presented before the material to be remembered, and for the recall of neutral passages. The special conditions necessary for demonstration of repression are viewed as shedding light on why it has previously been difficult to show evidence of repression in laboratory experiments. PMID:3783428

  12. BZLF1 governs CpG-methylated chromatin of Epstein-Barr Virus reversing epigenetic repression.

    PubMed

    Woellmer, Anne; Arteaga-Salas, Jose M; Hammerschmidt, Wolfgang

    2012-09-01

    Epigenetic mechanisms are essential for the regulation of all genes in mammalian cells but transcriptional repression including DNA methylation are also major epigenetic mechanisms of defense inactivating potentially harmful pathogens. Epstein-Barr Virus (EBV), however, has evolved to take advantage of CpG methylated DNA to regulate its own biphasic life cycle. We show here that latent EBV DNA has an extreme composition of methylated CpG dinucleotides with a bimodal distribution of unmethylated or fully methylated DNA at active latent genes or completely repressed lytic promoters, respectively. We find this scenario confirmed in primary EBV-infected memory B cells in vivo. Extensive CpG methylation of EBV's DNA argues for a very restricted gene expression during latency. Above-average nucleosomal occupancy, repressive histone marks, and Polycomb-mediated epigenetic silencing further shield early lytic promoters from activation during latency. The very tight repression of viral lytic genes must be overcome when latent EBV enters its lytic phase and supports de novo virus synthesis in infected cells. The EBV-encoded and AP-1 related transcription factor BZLF1 overturns latency and initiates virus synthesis in latently infected cells. Paradoxically, BZLF1 preferentially binds to CpG-methylated motifs in key viral promoters for their activation. Upon BZLF1 binding, we find nucleosomes removed, Polycomb repression lost, and RNA polymerase II recruited to the activated early promoters promoting efficient lytic viral gene expression. Surprisingly, DNA methylation is maintained throughout this phase of viral reactivation and is no hindrance to active transcription of extensively CpG methylated viral genes as thought previously. Thus, we identify BZLF1 as a pioneer factor that reverses epigenetic silencing of viral DNA to allow escape from latency and report on a new paradigm of gene regulation. PMID:22969425

  13. SUMOylation of the polycomb group protein L3MBTL2 facilitates repression of its target genes

    PubMed Central

    Stielow, Christina; Stielow, Bastian; Finkernagel, Florian; Scharfe, Maren; Jarek, Michael; Suske, Guntram

    2014-01-01

    Lethal(3) malignant brain tumour like 2 (L3MBTL2) is an integral component of the polycomb repressive complex 1.6 (PRC1.6) and has been implicated in transcriptional repression and chromatin compaction. Here, we show that L3MBTL2 is modified by SUMO2/3 at lysine residues 675 and 700 close to the C-terminus. SUMOylation of L3MBTL2 neither affected its repressive activity in reporter gene assays nor it’s binding to histone tails in vitro. In order to analyse whether SUMOylation affects binding of L3MBTL2 to chromatin, we performed ChIP-Seq analysis with chromatin of wild-type HEK293 cells and with chromatin of HEK293 cells stably expressing either FLAG-tagged SUMOylation-competent or SUMOylation-defective L3MBTL2. Wild-type FLAG-L3MBTL2 and the SUMOylation-defective FLAG-L3MBTL2 K675/700R mutant essentially occupied the same sites as endogenous L3MBTL2 suggesting that SUMOylation of L3MBTL2 does not affect chromatin binding. However, a subset of L3MBTL2-target genes, particularly those with low L3MBTL2 occupancy including pro-inflammatory genes, was de-repressed in cells expressing the FLAG-L3MBTL2 K675/700R mutant. Finally, we provide evidence that SUMOylation of L3MBTL2 facilitates repression of these PRC1.6-target genes by balancing the local H2Aub1 levels established by the ubiquitinating enzyme RING2 and the de-ubiquitinating PR–DUB complex. PMID:24369422

  14. Targeted repression of AXIN2 and MYC gene expression using designer TALEs

    SciTech Connect

    Rennoll, Sherri A.; Scott, Samantha A.; Yochum, Gregory S.

    2014-04-18

    Highlights: • We designed TALE–SID fusion proteins to target AXIN2 and MYC. • TALE–SIDs bound the chromosomal AXIN2 and MYC genes and repressed their expression. • TALE–SIDs repress β-catenin{sup S45F}-dependent AXIN2 and MYC transcription. - Abstract: Designer TALEs (dTALEs) are chimeric transcription factors that can be engineered to regulate gene expression in mammalian cells. Whether dTALEs can block gene transcription downstream of signal transduction cascades, however, has yet to be fully explored. Here we tested whether dTALEs can be used to target genes whose expression is controlled by Wnt/β-catenin signaling. TALE DNA binding domains were engineered to recognize sequences adjacent to Wnt responsive enhancer elements (WREs) that control expression of axis inhibition protein 2 (AXIN2) and c-MYC (MYC). These custom DNA binding domains were linked to the mSin3A interaction domain (SID) to generate TALE–SID chimeric repressors. The TALE–SIDs repressed luciferase reporter activity, bound their genomic target sites, and repressed AXIN2 and MYC expression in HEK293 cells. We generated a novel HEK293 cell line to determine whether the TALE–SIDs could function downstream of oncogenic Wnt/β-catenin signaling. Treating these cells with doxycycline and tamoxifen stimulates nuclear accumulation of a stabilized form of β-catenin found in a subset of colorectal cancers. The TALE–SIDs repressed AXIN2 and MYC expression in these cells, which suggests that dTALEs could offer an effective therapeutic strategy for the treatment of colorectal cancer.

  15. The transcription factor Mlc promotes Vibrio cholerae biofilm formation through repression of phosphotransferase system components.

    PubMed

    Pickering, Bradley S; Lopilato, Jane E; Smith, Daniel R; Watnick, Paula I

    2014-07-01

    The phosphoenol phosphotransferase system (PTS) is a multicomponent signal transduction cascade that regulates diverse aspects of bacterial cellular physiology in response to the availability of high-energy sugars in the environment. Many PTS components are repressed at the transcriptional level when the substrates they transport are not available. In Escherichia coli, the transcription factor Mlc (for makes large colonies) represses transcription of the genes encoding enzyme I (EI), histidine protein (HPr), and the glucose-specific enzyme IIBC (EIIBC(Glc)) in defined media that lack PTS substrates. When glucose is present, the unphosphorylated form of EIIBC(Glc) sequesters Mlc to the cell membrane, preventing its interaction with DNA. Very little is known about Vibrio cholerae Mlc. We found that V. cholerae Mlc activates biofilm formation in LB broth but not in defined medium supplemented with either pyruvate or glucose. Therefore, we questioned whether V. cholerae Mlc functions differently than E. coli Mlc. Here we have shown that, like E. coli Mlc, V. cholerae Mlc represses transcription of PTS components in both defined medium and LB broth and that E. coli Mlc is able to rescue the biofilm defect of a V. cholerae Δmlc mutant. Furthermore, we provide evidence that Mlc indirectly activates transcription of the vps genes by repressing expression of EI. Because activation of the vps genes by Mlc occurs under only a subset of the conditions in which repression of PTS components is observed, we conclude that additional inputs present in LB broth are required for activation of vps gene transcription by Mlc.

  16. Regulation of lac Operon Expression: Reappraisal of the Theory of Catabolite Repression

    PubMed Central

    Wanner, Barry L.; Kodaira, Ryoji; Neidhardt, Frederick C.

    1978-01-01

    The physiological state of Escherichia coli with respect to (permanent) catabolite repression was assessed by measuring the steady-state level of β-galactosidase in induced or in constitutive cells under a variety of growth conditions. Four results were obtained. (i) Catabolite repression had a major effect on fully induced or constitutive expression of the lac gene, and the magnitude of this effect was found to be dependent on the promoter structure; cells with a wild-type lac promoter showed an 18-fold variation in lac expression, and cells with the lacP37 (formerly lac-L37) promoter exhibited several hundred-fold variation. (ii) Exogenous adenosine cyclic 3′,5′-monophosphoric acid (cAMP) could not abolish catabolite repression, even though several controls demonstrated that cAMP was entering the cells in significant amounts. (Rapid intracellular degradation of cAMP could not be ruled out.) (iii) Neither the growth rate nor the presence of biosynthetic products altered the degree of catabolite repression; all variation could be related to the catabolites present in the growth medium. (iv) Slowing by imposing an amino acid restriction decreased the differential rate of β-galactosidase synthesis from the wild-type lac promoter when bacteria were cultured in either the absence or presence of cAMP; this decreased lac expression also occurred when the bacteria harbored the catabolite-insensitive lacP5 (formerly lacUV5) promoter mutation. These findings support the idea that (permanent) catabolite repression is set by the catabolites in the growth medium and may not be related to an imbalance between catabolism and anabolism. PMID:214424

  17. Repressive function of the micronucleus during asexual reproduction in Paramecium tetraurelia: Experimental analysis with defective-micronucleates generated by laser microbeam irradiation.

    PubMed

    Au, K Y; Ho, W S; Ng, S F

    1990-10-19

    The present paper reports on the experimental analysis of a novel regulatory function of the micronucleus of Paramecium tetraurelia. Previous studies have made clear that amicronucleate cell lines shortly after their generation generally suffer depression, in exhibiting low viability, slow growth and abnormal oral development in binary fission, but they eventually recover to near-normal. A compensatory mechanism is thus activated in the absence of the micronucleus, to allow recovery of the amicronucleate cell line. Implicit in this conclusion is the role of the micronucleus in repression of the compensatory mechanism. The present study tested this notion by perturbing the micronucleus with laser microbeam irradiation. This operation generated cell lines possessing defective micronuclei; during their asexual propagation, some cells lost the micronucleus and gave rise to amicronucleates. The viability of amicronucleate cell lines derived in this manner was found to be higher, compared to others generated by a different operation involving instantaneous removal of normal micronuclei from the cell with a microinjection needle. Some evidence also suggested that their oral development was less abnormal during the initial depression period. Hence, damage of the micronucleus has apparently facilitated the activation of the compensatory function, and the latter might have occurred even before the loss of the defective micronucleus. The present findings provide support for a regulatory role of the micronucleus during asexual propagation. Previous studies have indicated that the physical basis of the compensatory mechanism resides with the macronucleus. The micronuclear repressive function may be directed against this compensatory mechanism of the macronucleus.

  18. From classical psychodynamics to evidence synthesis: the motif of repression and a contemporary understanding of a key mediatory mechanism in psychosis.

    PubMed

    Fleming, Mick P; Martin, Colin R

    2012-06-01

    The stress vulnerability model has proven to be a politically important model for two reasons. It has provided the framework that defines a temporal and dynamic process whereby a person's uniquely determined biopsychosocial vulnerability to schizophrenia symptoms interacts with his or her capacity to manage stress and the amount and type of stress experienced in such a way that the person experiences schizophrenia symptoms. Second, the development of this framework promoted the notion of inherited and acquired vulnerability. Implicit was that vulnerability was individually determined and that there was a role for psychosocial factors in the development/maintenance of schizophrenia symptoms. This proved to be a catalyst for the development of studies implicating psychosocial factors in the etiology of schizophrenia symptoms. Studies derived from cognitive-behavioral theories have proven the most successful in identifying thinking patterns, emotional disturbances, and neurocognitive and defensive vulnerability factors inherent in the development of schizophrenia symptoms. Historically, within the psychoanalytic school there has been debate regarding the role of repressive coping mechanisms in schizophrenia development. Psychoanalytic theories have always appeared incapable of providing etiologic explanations of schizophrenia symptoms, with the possible exception of Melanie Klein, than other more salient psychosocial schools. Mechanisms within the process of repressive coping are consistent with evidence and mechanisms supporting the stress vulnerability models and existing cognitive-behavioral theories regarding development of paranoid delusions. These mechanisms are less consistent with social cognitive explanations of schizophrenia symptoms.

  19. Repressive function of the micronucleus during asexual reproduction in Paramecium tetraurelia: Experimental analysis with defective-micronucleates generated by laser microbeam irradiation.

    PubMed

    Au, K Y; Ho, W S; Ng, S F

    1990-10-19

    The present paper reports on the experimental analysis of a novel regulatory function of the micronucleus of Paramecium tetraurelia. Previous studies have made clear that amicronucleate cell lines shortly after their generation generally suffer depression, in exhibiting low viability, slow growth and abnormal oral development in binary fission, but they eventually recover to near-normal. A compensatory mechanism is thus activated in the absence of the micronucleus, to allow recovery of the amicronucleate cell line. Implicit in this conclusion is the role of the micronucleus in repression of the compensatory mechanism. The present study tested this notion by perturbing the micronucleus with laser microbeam irradiation. This operation generated cell lines possessing defective micronuclei; during their asexual propagation, some cells lost the micronucleus and gave rise to amicronucleates. The viability of amicronucleate cell lines derived in this manner was found to be higher, compared to others generated by a different operation involving instantaneous removal of normal micronuclei from the cell with a microinjection needle. Some evidence also suggested that their oral development was less abnormal during the initial depression period. Hence, damage of the micronucleus has apparently facilitated the activation of the compensatory function, and the latter might have occurred even before the loss of the defective micronucleus. The present findings provide support for a regulatory role of the micronucleus during asexual propagation. Previous studies have indicated that the physical basis of the compensatory mechanism resides with the macronucleus. The micronuclear repressive function may be directed against this compensatory mechanism of the macronucleus. PMID:23196191

  20. From classical psychodynamics to evidence synthesis: the motif of repression and a contemporary understanding of a key mediatory mechanism in psychosis.

    PubMed

    Fleming, Mick P; Martin, Colin R

    2012-06-01

    The stress vulnerability model has proven to be a politically important model for two reasons. It has provided the framework that defines a temporal and dynamic process whereby a person's uniquely determined biopsychosocial vulnerability to schizophrenia symptoms interacts with his or her capacity to manage stress and the amount and type of stress experienced in such a way that the person experiences schizophrenia symptoms. Second, the development of this framework promoted the notion of inherited and acquired vulnerability. Implicit was that vulnerability was individually determined and that there was a role for psychosocial factors in the development/maintenance of schizophrenia symptoms. This proved to be a catalyst for the development of studies implicating psychosocial factors in the etiology of schizophrenia symptoms. Studies derived from cognitive-behavioral theories have proven the most successful in identifying thinking patterns, emotional disturbances, and neurocognitive and defensive vulnerability factors inherent in the development of schizophrenia symptoms. Historically, within the psychoanalytic school there has been debate regarding the role of repressive coping mechanisms in schizophrenia development. Psychoanalytic theories have always appeared incapable of providing etiologic explanations of schizophrenia symptoms, with the possible exception of Melanie Klein, than other more salient psychosocial schools. Mechanisms within the process of repressive coping are consistent with evidence and mechanisms supporting the stress vulnerability models and existing cognitive-behavioral theories regarding development of paranoid delusions. These mechanisms are less consistent with social cognitive explanations of schizophrenia symptoms. PMID:22359200

  1. Redistribution of H3K27me3 upon DNA hypomethylation results in de-repression of Polycomb target genes

    PubMed Central

    2013-01-01

    Background DNA methylation and the Polycomb repression system are epigenetic mechanisms that play important roles in maintaining transcriptional repression. Recent evidence suggests that DNA methylation can attenuate the binding of Polycomb protein components to chromatin and thus plays a role in determining their genomic targeting. However, whether this role of DNA methylation is important in the context of transcriptional regulation is unclear. Results By genome-wide mapping of the Polycomb Repressive Complex 2-signature histone mark, H3K27me3, in severely DNA hypomethylated mouse somatic cells, we show that hypomethylation leads to widespread H3K27me3 redistribution, in a manner that reflects the local DNA methylation status in wild-type cells. Unexpectedly, we observe striking loss of H3K27me3 and Polycomb Repressive Complex 2 from Polycomb target gene promoters in DNA hypomethylated cells, including Hox gene clusters. Importantly, we show that many of these genes become ectopically expressed in DNA hypomethylated cells, consistent with loss of Polycomb-mediated repression. Conclusions An intact DNA methylome is required for appropriate Polycomb-mediated gene repression by constraining Polycomb Repressive Complex 2 targeting. These observations identify a previously unappreciated role for DNA methylation in gene regulation and therefore influence our understanding of how this epigenetic mechanism contributes to normal development and disease. PMID:23531360

  2. The FBXL10/KDM2B Scaffolding Protein Associates with Novel Polycomb Repressive Complex-1 to Regulate Adipogenesis*

    PubMed Central

    Inagaki, Takeshi; Iwasaki, Satoshi; Matsumura, Yoshihiro; Kawamura, Takeshi; Tanaka, Toshiya; Abe, Yohei; Yamasaki, Ayumu; Tsurutani, Yuya; Yoshida, Ayano; Chikaoka, Yoko; Nakamura, Kanako; Magoori, Kenta; Nakaki, Ryo; Osborne, Timothy F.; Fukami, Kiyoko; Aburatani, Hiroyuki; Kodama, Tatsuhiko; Sakai, Juro

    2015-01-01

    Polycomb repressive complex 1 (PRC1) plays an essential role in the epigenetic repression of gene expression during development and cellular differentiation via multiple effector mechanisms, including ubiquitination of H2A and chromatin compaction. However, whether it regulates the stepwise progression of adipogenesis is unknown. Here, we show that FBXL10/KDM2B is an anti-adipogenic factor that is up-regulated during the early phase of 3T3-L1 preadipocyte differentiation and in adipose tissue in a diet-induced model of obesity. Interestingly, inhibition of adipogenesis does not require the JmjC demethylase domain of FBXL10, but it does require the F-box and leucine-rich repeat domains, which we show recruit a noncanonical polycomb repressive complex 1 (PRC1) containing RING1B, SKP1, PCGF1, and BCOR. Knockdown of either RING1B or SKP1 prevented FBXL10-mediated repression of 3T3-L1 preadipocyte differentiation indicating that PRC1 formation mediates the inhibitory effect of FBXL10 on adipogenesis. Using ChIP-seq, we show that FBXL10 recruits RING1B to key specific genomic loci surrounding the key cell cycle and the adipogenic genes Cdk1, Uhrf1, Pparg1, and Pparg2 to repress adipogenesis. These results suggest that FBXL10 represses adipogenesis by targeting a noncanonical PRC1 complex to repress key genes (e.g. Pparg) that control conversion of pluripotent cells into the adipogenic lineage. PMID:25533466

  3. The polyphenol fisetin protects bone by repressing NF-κB and MKP-1-dependent signaling pathways in osteoclasts.

    PubMed

    Léotoing, Laurent; Wauquier, Fabien; Guicheux, Jérôme; Miot-Noirault, Elisabeth; Wittrant, Yohann; Coxam, Véronique

    2013-01-01

    Osteoporosis is a bone pathology leading to increase fractures risk and challenging quality of life. Since current treatments could exhibit deleterious side effects, the use of food compounds derived from plants represents a promising innovative alternative due to their potential therapeutic and preventive activities against human diseases. In this study, we investigated the ability of the polyphenol fisetin to counter osteoporosis and analyzed the cellular and molecular mechanisms involved. In vivo, fisetin consumption significantly prevented bone loss in estrogen deficiency and inflammation mice osteoporosis models. Indeed, bone mineral density, micro-architecture parameters and bone markers were positively modulated by fisetin. Consistent with in vivo results, we showed that fisetin represses RANKL-induced osteoclast differentiation and activity as demonstrated by an inhibition of multinucleated cells formation, TRAP activity and differentiation genes expression. The signaling pathways NF-κB, p38 MAPK, JNK and the key transcription factors c-Fos and NFATc1 expressions induced by RANKL, were negatively regulated by fisetin. We further showed that fisetin inhibits the constitutive proteasomal degradation of MKP-1, the phosphatase that deactivates p38 and JNK. Consistently, using shRNA stable cell lines, we demonstrated that impairment of MKP-1 decreases fisetin potency. Taken together, these results strongly support that fisetin should be further considered as a bone protective agent.

  4. Fed-batch fermentation for enhanced lactic acid production from glucose/xylose mixture without carbon catabolite repression.

    PubMed

    Abdel-Rahman, Mohamed Ali; Xiao, Yaotian; Tashiro, Yukihiro; Wang, Ying; Zendo, Takeshi; Sakai, Kenji; Sonomoto, Kenji

    2015-02-01

    There has been tremendous growth in the production of optically pure l-lactic acid from lignocellulose-derived sugars. In this study, Enterococcus mundtii QU 25 was used to ferment a glucose/xylose mixture to l-lactic acid. Maintenance of the xylose concentration at greater than 10 g/L achieved homo-lactic acid fermentation and reduced the formation of byproducts. Furthermore, carbon catabolite repression (CCR) was avoided by maintaining the glucose concentration below 25 g/L; therefore, initial concentrations of 25 g/L glucose and 50 g/L xylose were selected. Supplementation with 5 g/L yeast extract enhanced the maximum xylose consumption rate and consequently increased lactic acid production and productivity. Finally, a 129 g/L lactic acid without byproducts was obtained with a maximum lactic acid productivity of 5.60 g/(L·h) in fed-batch fermentation with feeding a glucose/xylose mixture using ammonium hydroxide as the neutralizing agent. These results indicate a potential for lactic acid production from glucose and xylose as the main components of lignocellulosic biomasses.

  5. DeoR repression at-a-distance only weakly responds to changes in interoperator separation and DNA topology.

    PubMed Central

    Dandanell, G

    1992-01-01

    The interoperator distance between a synthetic operator Os and the deoP2O2-galK fusion was varied between 46 and 176 bp. The repression of the deoP2 directed galK expression as a function of the interoperator distance (center-to-center) was measured in vivo in a single-copy system. The results show that the DeoR repressor efficiently can repress transcription at all the interoperator distances tested. The degree of repression depends very little on the spacing between the operators, however, a weak periodic dependency of 8-11 bp may exist. PMID:1437558

  6. Purine and pyrimidine-specific repression of the Escherichia coli carAB operon are functionally and structurally coupled.

    PubMed

    Devroede, Neel; Thia-Toong, Thia-Lin; Gigot, Daniel; Maes, Dominique; Charlier, Daniel

    2004-02-01

    Transcription of the carAB operon encoding the sole carbamoylphosphate synthetase of Escherichia coli proceeds from a tandem pair of promoters. P2, downstream, is repressed by arginine and the ArgR protein, whereas P1 is submitted to pyrimidine-specific regulation and as shown here to purine-specific control exerted by binding of the PurR protein to a PUR box sequence centered around nucleotide -128.5 with respect to the start of P1 transcription. In vivo analyses of the effects of trans and cis-acting mutations on the regulatory responses and single round in vitro transcription assays indicated that ligand-bound PurR is by itself unable to inhibit P1 promoter activity. To exert its effect PurR relies on the elaborated nucleoprotein complex that governs P1 activity in a pyrimidine-specific manner. Thus we reveal the existence of an unprecedented functional and structural coupling between the modulation of P1 activity by purine and pyrimidine residues that appears to result from the unique position of the PUR box in the carAB control region, far upstream of the promoter. Missing contact and premethylation binding interference studies revealed the importance of base-specific groups and of structural aspects of the PUR box sequence in complex formation. Permutation assays indicated that the overall PurR-induced bending of the carAB control region is slightly less pronounced than that of the purF operator. The PUR boxes of the carAB operon of E.coli and Salmonella typhimurium are unique in that they have a guanine residue at position eight. Interestingly, guanine at this position has been proposed to be extremely unfavorable on the basis of modeling and binding studies, as its exocyclic amino group would enter into a steric clash with the side-chain of lysine 55. To analyze the effect of guanine at position eight in the upstream half-site of the carAB operator we constructed the adenine derivative and assayed in vivo repressibility of P1 promoter activity and in vitro

  7. Functional repression of PtSND2 represses growth and development by disturbing auxin biosynthesis, transport and signaling in transgenic poplar.

    PubMed

    Wang, Haihai; Tang, Renjie; Wang, Cuiting; Qi, Qi; Gai, Ying; Jiang, Xiangning; Zhang, Hongxia

    2015-01-01

    Using chimeric repressor silencing technology, we previously reported that functional repression of PtSND2 severely arrested wood formation in transgenic poplar (Populus). Here, we provide further evidence that auxin biosynthesis, transport and signaling were disturbed in these transgenic plants, leading to pleiotropic defects in their growth patterns, including inhibited leaf enlargement and vascular tissue development in the leaf central vein, suppressed cambial growth and fiber elongation in the stem, and arrested growth in the root system. Two transgenic lines, which displayed the most remarkable phenotypic deviation from the wild-type, were selected for detailed studies. In both transgenic lines, expression of genes for auxin biosynthesis, transport and signaling was down-regulated, and indole-3-acetic acid distribution was severely disturbed in the apical buds, leaves, stems and roots of field-grown transgenic plants. Transient transcription dual-luciferase assays of ProPtTYDC2::LUC, ProPttLAX2::LUC and ProPoptrIAA20.2::LUC in poplar protoplasts revealed that expression of auxin-related genes might be regulated by PtSND2 at the transcriptional level. All these results indicate that functional repression of PtSND2 altered auxin biosynthesis, transport and signaling, and thereby disturbed the normal growth and development of transgenic plants.

  8. Functional repression of PtSND2 represses growth and development by disturbing auxin biosynthesis, transport and signaling in transgenic poplar.

    PubMed

    Wang, Haihai; Tang, Renjie; Wang, Cuiting; Qi, Qi; Gai, Ying; Jiang, Xiangning; Zhang, Hongxia

    2015-01-01

    Using chimeric repressor silencing technology, we previously reported that functional repression of PtSND2 severely arrested wood formation in transgenic poplar (Populus). Here, we provide further evidence that auxin biosynthesis, transport and signaling were disturbed in these transgenic plants, leading to pleiotropic defects in their growth patterns, including inhibited leaf enlargement and vascular tissue development in the leaf central vein, suppressed cambial growth and fiber elongation in the stem, and arrested growth in the root system. Two transgenic lines, which displayed the most remarkable phenotypic deviation from the wild-type, were selected for detailed studies. In both transgenic lines, expression of genes for auxin biosynthesis, transport and signaling was down-regulated, and indole-3-acetic acid distribution was severely disturbed in the apical buds, leaves, stems and roots of field-grown transgenic plants. Transient transcription dual-luciferase assays of ProPtTYDC2::LUC, ProPttLAX2::LUC and ProPoptrIAA20.2::LUC in poplar protoplasts revealed that expression of auxin-related genes might be regulated by PtSND2 at the transcriptional level. All these results indicate that functional repression of PtSND2 altered auxin biosynthesis, transport and signaling, and thereby disturbed the normal growth and development of transgenic plants. PMID:25516528

  9. Role of the proto-oncogene Pokemon in cellular transformation and ARF repression.

    PubMed

    Maeda, Takahiro; Hobbs, Robin M; Merghoub, Taha; Guernah, Ilhem; Zelent, Arthur; Cordon-Cardo, Carlos; Teruya-Feldstein, Julie; Pandolfi, Pier Paolo

    2005-01-20

    Aberrant transcriptional repression through chromatin remodelling and histone deacetylation has been postulated to represent a driving force underlying tumorigenesis because histone deacetylase inhibitors have been found to be effective in cancer treatment. However, the molecular mechanisms by which transcriptional derepression would be linked to tumour suppression are poorly understood. Here we identify the transcriptional repressor Pokemon (encoded by the Zbtb7 gene) as a critical factor in oncogenesis. Mouse embryonic fibroblasts lacking Zbtb7 are completely refractory to oncogene-mediated cellular transformation. Conversely, Pokemon overexpression leads to overt oncogenic transformation both in vitro and in vivo in transgenic mice. Pokemon can specifically repress the transcription of the tumour suppressor gene ARF through direct binding. We find that Pokemon is aberrantly overexpressed in human cancers and that its expression levels predict biological behaviour and clinical outcome. Pokemon's critical role in cellular transformation makes it an attractive target for therapeutic intervention. PMID:15662416

  10. Transcription factors LRF and BCL11A independently repress expression of fetal hemoglobin

    PubMed Central

    Masuda, Takeshi; Wang, Xin; Maeda, Manami; Canver, Matthew C.; Sher, Falak; Funnell, Alister P. W.; Fisher, Chris; Suciu, Maria; Martyn, Gabriella E.; Norton, Laura J.; Zhu, Catherine; Kurita, Ryo; Nakamura, Yukio; Xu, Jian; Higgs, Douglas R.; Crossley, Merlin; Bauer, Daniel E.; Orkin, Stuart H.; Kharchenko, Peter V.; Maeda, Takahiro

    2016-01-01

    Genes encoding human β-type globin undergo a developmental switch from embryonic to fetal to adult-type expression. Mutations in the adult form cause inherited hemoglobinopathies or globin disorders, including sickle cell disease and thalassemia. Some experimental results have suggested that these diseases could be treated by induction of fetal-type hemoglobin (HbF). However, the mechanisms that repress HbF in adults remain unclear. We found that the LRF/ZBTB7A transcription factor occupies fetal γ-globin genes and maintains the nucleosome density necessary for γ-globin gene silencing in adults, and that LRF confers its repressive activity through a NuRD repressor complex independent of the fetal globin repressor BCL11A. Our study may provide additional opportunities for therapeutic targeting in the treatment of hemoglobinopathies. PMID:26816381

  11. Phosphoribulokinase mediates nitrogenase-induced carbon dioxide fixation gene repression in Rhodobacter sphaeroides

    PubMed Central

    Farmer, Ryan M.

    2015-01-01

    In many organisms there is a balance between carbon and nitrogen metabolism. These observations extend to the nitrogen-fixing, nonsulfur purple bacteria, which have the classic family of P(II) regulators that coordinate signals of carbon and nitrogen status to regulate nitrogen metabolism. Curiously, these organisms also possess a reverse mechanism to regulate carbon metabolism based on cellular nitrogen status. In this work, studies in Rhodobacter sphaeroides firmly established that the activity of the enzyme that catalyses nitrogen fixation, nitrogenase, induces a signal that leads to repression of genes encoding enzymes of the Calvin–Benson–Bassham (CBB) CO2 fixation pathway. Additionally, genetic and metabolomic experiments revealed that NADH-activated phosphoribulokinase is an intermediate in the signalling pathway. Thus, nitrogenase activity appears to be linked to cbb gene repression through phosphoribulokinase. PMID:26306848

  12. Repression and solidary cultures of resistance: Irish political prisoners on protest.

    PubMed

    O'Hearn, Denis

    2009-09-01

    Social activists and especially insurgents have created solidary cultures of resistance in conditions of high risk and repression. One such instance is an episode of contention by Irish political prisoners in the late 1970s. The "blanketmen" appropriated and then built a solidary culture within spaces that had been under official control. Their ability to maintain such a collective response was enhanced by an intensifying cycle of protest and violent reprisal, including extreme stripping of their material environment, in which the prisoners gained considerable initiative. This study uses interviews and contemporary writings by prisoners, prison authorities, visitors, and movement activists to examine how the dynamic of protest and repression transformed insurgent prison culture--through material, emotional, and perceptive changes--and the importance of leadership in the transformation. Special attention is given to prisoner activities in appropriated spaces that reinforced the culture of resistance: promoting the Irish language, cultural production, and the production of propaganda. PMID:20614763

  13. c-Fos Repression by Piwi Regulates Drosophila Ovarian Germline Formation and Tissue Morphogenesis

    PubMed Central

    Klein, Jonathon D.; Qu, Chunxu; Yang, Xiaoyang; Fan, Yiping; Tang, Chunlao; Peng, Jamy C.

    2016-01-01

    Drosophila melanogaster Piwi functions within the germline stem cells (GSCs) and the somatic niche to regulate GSC self-renewal and differentiation. How Piwi influences GSCs is largely unknown. We uncovered a genetic interaction between Piwi and c-Fos in the somatic niche that influences GSCs. c-Fos is a proto-oncogene that influences many cell and developmental processes. In wild-type ovarian cells, c-Fos is post-transcriptionally repressed by Piwi, which destabilized the c-Fos mRNA by promoting the processing of its 3′ untranslated region (UTR) into Piwi-interacting RNAs (piRNAs). The c-Fos 3′ UTR was sufficient to trigger Piwi-dependent destabilization of a GFP reporter. Piwi represses c-Fos in the somatic niche to regulate GSC maintenance and differentiation and in the somatic follicle cells to affect somatic cell disorganization, tissue dysmorphogenesis, oocyte maturation arrest, and infertility. PMID:27622269

  14. Transcription factors that convert adult cell identity are differentially polycomb repressed.

    PubMed

    Davis, Fred P; Eddy, Sean R

    2013-01-01

    Transcription factors that can convert adult cells of one type to another are usually discovered empirically by testing factors with a known developmental role in the target cell. Here we show that standard genomic methods (RNA-seq and ChIP-seq) can help identify these factors, as most are more strongly Polycomb repressed in the source cell and more highly expressed in the target cell. This criterion is an effective genome-wide screen that significantly enriches for factors that can transdifferentiate several mammalian cell types including neural stem cells, neurons, pancreatic islets, and hepatocytes. These results suggest that barriers between adult cell types, as depicted in Waddington's "epigenetic landscape", consist in part of differentially Polycomb-repressed transcription factors. This genomic model of cell identity helps rationalize a growing number of transdifferentiation protocols and may help facilitate the engineering of cell identity for regenerative medicine.

  15. [Does repression explain the forgetting of dreams? An experimental approach to Freud's theory of dreams].

    PubMed

    Köhler, Thomas; Peretzki, Jörg

    2009-05-01

    An experiment was carried out to test whether forgetting of dream material is due to repression. Under this assumption one would expect that free associations starting from forgotten elements encounter successively growing resistance. Subjects brought along notes of dreams and were later tested for recognition of short sequences of their dreams. In addition, they produced free associations to 5 elements they had remembered and to 5 elements not identified in the recognition test. Skin conductance responses (SCR) and perceived unpleasantness were recorded. The main results were: In comparison to recognized dream material, unrecognized elements elicited associations accompanied by greater psychophysiologic activation. During associations to the latter stimuli, increase of SCR was more frequent. Our findings are in line with Freud's assumption that forgetting of dreams is an effect of repression.

  16. Transcription factors LRF and BCL11A independently repress expression of fetal hemoglobin.

    PubMed

    Masuda, Takeshi; Wang, Xin; Maeda, Manami; Canver, Matthew C; Sher, Falak; Funnell, Alister P W; Fisher, Chris; Suciu, Maria; Martyn, Gabriella E; Norton, Laura J; Zhu, Catherine; Kurita, Ryo; Nakamura, Yukio; Xu, Jian; Higgs, Douglas R; Crossley, Merlin; Bauer, Daniel E; Orkin, Stuart H; Kharchenko, Peter V; Maeda, Takahiro

    2016-01-15

    Genes encoding human β-type globin undergo a developmental switch from embryonic to fetal to adult-type expression. Mutations in the adult form cause inherited hemoglobinopathies or globin disorders, including sickle cell disease and thalassemia. Some experimental results have suggested that these diseases could be treated by induction of fetal-type hemoglobin (HbF). However, the mechanisms that repress HbF in adults remain unclear. We found that the LRF/ZBTB7A transcription factor occupies fetal γ-globin genes and maintains the nucleosome density necessary for γ-globin gene silencing in adults, and that LRF confers its repressive activity through a NuRD repressor complex independent of the fetal globin repressor BCL11A. Our study may provide additional opportunities for therapeutic targeting in the treatment of hemoglobinopathies. PMID:26816381

  17. MYC Association with Cancer Risk and a New Model of MYC-Mediated Repression

    PubMed Central

    Cole, Michael D.

    2014-01-01

    MYC is one of the most frequently mutated and overexpressed genes in human cancer but the regulation of MYC expression and the ability of MYC protein to repress cellular genes (including itself) have remained mysterious. Recent genome-wide association studies show that many genetic polymorphisms associated with disease risk map to distal regulatory elements that regulate the MYC promoter through large chromatin loops. Cancer risk-associated single-nucleotide polymorphisms (SNPs) contain more potent enhancer activity, promoting higher MYC levels and a greater risk of disease. The MYC promoter is also subject to complex regulatory circuits and limits its own expression by a feedback loop. A model for MYC autoregulation is discussed which involves a signaling pathway between the PTEN (phosphatase and tensin homolog) tumor suppressor and repressive histone modifications laid down by the EZH2 methyltransferase. PMID:24985129

  18. Role of the proto-oncogene Pokemon in cellular transformation and ARF repression.

    PubMed

    Maeda, Takahiro; Hobbs, Robin M; Merghoub, Taha; Guernah, Ilhem; Zelent, Arthur; Cordon-Cardo, Carlos; Teruya-Feldstein, Julie; Pandolfi, Pier Paolo

    2005-01-20

    Aberrant transcriptional repression through chromatin remodelling and histone deacetylation has been postulated to represent a driving force underlying tumorigenesis because histone deacetylase inhibitors have been found to be effective in cancer treatment. However, the molecular mechanisms by which transcriptional derepression would be linked to tumour suppression are poorly understood. Here we identify the transcriptional repressor Pokemon (encoded by the Zbtb7 gene) as a critical factor in oncogenesis. Mouse embryonic fibroblasts lacking Zbtb7 are completely refractory to oncogene-mediated cellular transformation. Conversely, Pokemon overexpression leads to overt oncogenic transformation both in vitro and in vivo in transgenic mice. Pokemon can specifically repress the transcription of the tumour suppressor gene ARF through direct binding. We find that Pokemon is aberrantly overexpressed in human cancers and that its expression levels predict biological behaviour and clinical outcome. Pokemon's critical role in cellular transformation makes it an attractive target for therapeutic intervention.

  19. Directed forgetting of trauma cues in adults reporting repressed or recovered memories of childhood sexual abuse.

    PubMed

    McNally, R J; Clancy, S A; Schacter, D L

    2001-02-01

    An item-cuing directed forgetting task was used to investigate whether women reporting repressed (n = 13) or recovered (n = 13) memories of childhood sexual abuse (CSA) exhibit an avoidant encoding style (and resultant impaired memory) for trauma cues relative to women reporting no CSA experience (n = 15). All participants viewed intermixed trauma (e.g., molested), positive (e.g., confident), and categorized neutral (e.g., mailbox) words on a computer screen and were instructed either to remember or to forget each word. The results provided no support for the hypothesis that people reporting either repressed or recovered memories of CSA are especially adept at forgetting words related to trauma. These groups recalled words they were instructed to remember more often than words they were instructed to forget regardless of whether they were trauma related.

  20. Suppression of BRD4 inhibits human hepatocellular carcinoma by repressing MYC and enhancing BIM expression.

    PubMed

    Li, Gong-Quan; Guo, Wen-Zhi; Zhang, Yi; Seng, Jing-Jing; Zhang, Hua-Peng; Ma, Xiu-Xian; Zhang, Gong; Li, Jie; Yan, Bing; Tang, Hong-Wei; Li, Shan-Shan; Wang, Li-Dong; Zhang, Shui-Jun

    2016-01-19

    Bromodomain 4 (BRD4) is an epigenetic regulator that, when inhibited, has anti-cancer effects. In this study, we investigated whether BRD4 could be a target for treatment of human hepatocellular carcinoma (HCC). We show that BRD4 is over-expressed in HCC tissues. Suppression of BRD4, either by siRNA or using JQ1, a pharmaceutical BRD4 inhibitor, reduced cell growth and induced apoptosis in HCC cell lines while also slowing HCC xenograft tumor growth in mice. JQ1 treatment induced G1 cell cycle arrest by repressing MYC expression, which led to the up-regulation of CDKN1B (P27). JQ1 also de-repressed expression of the pro-apoptotic BCL2L11 (BIM). Moreover, siRNA knockdown of BIM attenuated JQ1-triggered apoptosis in HCC cells, suggesting an essential role for BIM in mediating JQ1 anti-HCC activity. PMID:26575167

  1. Genetic interactions among scribbler, Atrophin and groucho in Drosophila uncover links in transcriptional repression.

    PubMed

    Wehn, Amy; Campbell, Gerard

    2006-06-01

    In eukaryotes, the ability of DNA-binding proteins to act as transcriptional repressors often requires that they recruit accessory proteins, known as corepressors, which provide the activity responsible for silencing transcription. Several of these factors have been identified, including the Groucho (Gro) and Atrophin (Atro) proteins in Drosophila. Here we demonstrate strong genetic interactions between gro and Atro and also with mutations in a third gene, scribbler (sbb), which encodes a nuclear protein of unknown function. We show that mutations in Atro and Sbb have similar phenotypes, including upregulation of the same genes in imaginal discs, which suggests that Sbb cooperates with Atro to provide repressive activity. Comparison of gro and Atro/sbb mutant phenotypes suggests that they do not function together, but instead that they may interact with the same transcription factors, including Engrailed and C15, to provide these proteins with maximal repressive activity.

  2. NFIB-Mediated Repression of the Epigenetic Factor Ezh2 Regulates Cortical Development

    PubMed Central

    Barry, Guy; Harvey, Tracey J.; McLeay, Robert; Smith, Aaron G.; Harris, Lachlan; Mason, Sharon; Stringer, Brett W.; Day, Bryan W.; Wray, Naomi R.; Gronostajski, Richard M.; Bailey, Timothy L.; Boyd, Andrew W.

    2014-01-01

    Epigenetic mechanisms are essential in regulating neural progenitor cell self-renewal, with the chromatin-modifying protein Enhancer of zeste homolog 2 (EZH2) emerging as a central player in promoting progenitor cell self-renewal during cortical development. Despite this, how Ezh2 is itself regulated remains unclear. Here, we demonstrate that the transcription factor nuclear factor IB (NFIB) plays a key role in this process. Nfib−/− mice exhibit an increased number of proliferative ventricular zone cells that express progenitor cell markers and upregulation of EZH2 expression within the neocortex and hippocampus. NFIB binds to the Ezh2 promoter and overexpression of NFIB represses Ezh2 transcription. Finally, key downstream targets of EZH2-mediated epigenetic repression are misregulated in Nfib−/− mice. Collectively, these results suggest that the downregulation of Ezh2 transcription by NFIB is an important component of the process of neural progenitor cell differentiation during cortical development. PMID:24553933

  3. c-Fos Repression by Piwi Regulates Drosophila Ovarian Germline Formation and Tissue Morphogenesis.

    PubMed

    Klein, Jonathon D; Qu, Chunxu; Yang, Xiaoyang; Fan, Yiping; Tang, Chunlao; Peng, Jamy C

    2016-09-01

    Drosophila melanogaster Piwi functions within the germline stem cells (GSCs) and the somatic niche to regulate GSC self-renewal and differentiation. How Piwi influences GSCs is largely unknown. We uncovered a genetic interaction between Piwi and c-Fos in the somatic niche that influences GSCs. c-Fos is a proto-oncogene that influences many cell and developmental processes. In wild-type ovarian cells, c-Fos is post-transcriptionally repressed by Piwi, which destabilized the c-Fos mRNA by promoting the processing of its 3' untranslated region (UTR) into Piwi-interacting RNAs (piRNAs). The c-Fos 3' UTR was sufficient to trigger Piwi-dependent destabilization of a GFP reporter. Piwi represses c-Fos in the somatic niche to regulate GSC maintenance and differentiation and in the somatic follicle cells to affect somatic cell disorganization, tissue dysmorphogenesis, oocyte maturation arrest, and infertility. PMID:27622269

  4. Mutations in GAL2 or GAL4 alleviate catabolite repression produced by galactose in Saccharomyces cerevisiae.

    PubMed

    Rodríguez; Flores

    2000-06-01

    Galactose does not allow growth of pyruvate carboxylase mutants in media with ammonium as a nitrogen source, and inhibits growth of strains defective in phosphoglyceromutase in ethanol-glycerol mixtures. Starting with pyc1, pyc2, and gpm1 strains, we isolated mutants that eliminated those galactose effects. The mutations were recessive and were named dgr1-1 and dgr2-1. Strains bearing those mutations in an otherwise wild-type background grew slower than the wild type in rich galactose media, and their growth was dependent on respiration. Galactose repression of several enzymes was relieved in the mutants. Biochemical and genetic evidence showed that dgr1-1 was allelic with GAL2 and dgr2-1 with GAL4. The results indicate that the rate of galactose consumption is critical to cause catabolite repression.

  5. Phosphoribulokinase mediates nitrogenase-induced carbon dioxide fixation gene repression in Rhodobacter sphaeroides.

    PubMed

    Farmer, Ryan M; Tabita, F Robert

    2015-11-01

    In many organisms there is a balance between carbon and nitrogen metabolism. These observations extend to the nitrogen-fixing, nonsulfur purple bacteria, which have the classic family of P(II) regulators that coordinate signals of carbon and nitrogen status to regulate nitrogen metabolism. Curiously, these organisms also possess a reverse mechanism to regulate carbon metabolism based on cellular nitrogen status. In this work, studies in Rhodobacter sphaeroides firmly established that the activity of the enzyme that catalyses nitrogen fixation, nitrogenase, induces a signal that leads to repression of genes encoding enzymes of the Calvin-Benson-Bassham (CBB) CO2 fixation pathway. Additionally, genetic and metabolomic experiments revealed that NADH-activated phosphoribulokinase is an intermediate in the signalling pathway. Thus, nitrogenase activity appears to be linked to cbb gene repression through phosphoribulokinase.

  6. The natural product peiminine represses colorectal carcinoma tumor growth by inducing autophagic cell death.

    PubMed

    Lyu, Qing; Tou, Fangfang; Su, Hong; Wu, Xiaoyong; Chen, Xinyi; Zheng, Zhi

    2015-06-19

    Autophagy is evolutionarily conservative in eukaryotic cells that engulf cellular long-lived proteins and organelles, and it degrades the contents through fusion with lysosomes, via which the cell acquires recycled building blocks for the synthesis of new molecules. In this study, we revealed that peiminine induces cell death and enhances autophagic flux in colorectal carcinoma HCT-116 cells. We determined that peiminine enhances the autophagic flux by repressing the phosphorylation of mTOR through inhibiting upstream signals. Knocking down ATG5 greatly reduced the peiminine-induced cell death in wild-type HCT-116 cells, while treating Bax/Bak-deficient cells with peiminine resulted in significant cell death. In summary, our discoveries demonstrated that peiminine represses colorectal carcinoma cell proliferation and cell growth by inducing autophagic cell death.

  7. Suppression of BRD4 inhibits human hepatocellular carcinoma by repressing MYC and enhancing BIM expression

    PubMed Central

    Zhang, Yi; Seng, Jing-Jing; Zhang, Hua-Peng; Ma, Xiu-Xian; Zhang, Gong; Li, Jie; Yan, Bing; Tang, Hong-Wei; Li, Shan-Shan; Wang, Li-Dong; Zhang, Shui-Jun

    2016-01-01

    Bromodomain 4 (BRD4) is an epigenetic regulator that, when inhibited, has anti-cancer effects. In this study, we investigated whether BRD4 could be a target for treatment of human hepatocellular carcinoma (HCC). We show that BRD4 is over-expressed in HCC tissues. Suppression of BRD4, either by siRNA or using JQ1, a pharmaceutical BRD4 inhibitor, reduced cell growth and induced apoptosis in HCC cell lines while also slowing HCC xenograft tumor growth in mice. JQ1 treatment induced G1 cell cycle arrest by repressing MYC expression, which led to the up-regulation of CDKN1B (P27). JQ1 also de-repressed expression of the pro-apoptotic BCL2L11 (BIM). Moreover, siRNA knockdown of BIM attenuated JQ1-triggered apoptosis in HCC cells, suggesting an essential role for BIM in mediating JQ1 anti-HCC activity. PMID:26575167

  8. Military westernization and state repression in the post-Cold War era.

    PubMed

    Swed, Ori; Weinreb, Alexander

    2015-09-01

    The waves of unrest that have shaken the Arab world since December 2010 have highlighted significant differences in the readiness of the military to intervene in political unrest by forcefully suppressing dissent. We suggest that in the post-Cold War period, this readiness is inversely associated with the level of military westernization, which is a product of the acquisition of arms from western countries. We identify two mechanisms linking the acquisition of arms from western countries to less repressive responses: dependence and conditionality; and a longer-term diffusion of ideologies regarding the proper form of civil-military relations. Empirical support for our hypothesis is found in an analysis of 2523 cases of government response to political unrest in 138 countries in the 1996-2005 period. We find that military westernization mitigates state repression in general, with more pronounced effects in the poorest countries. However, we also identify substantial differences between the pre- and post-9/11 periods.

  9. Neural Progenitors Adopt Specific Identities by Directly Repressing All Alternative Progenitor Transcriptional Programs.

    PubMed

    Kutejova, Eva; Sasai, Noriaki; Shah, Ankita; Gouti, Mina; Briscoe, James

    2016-03-21

    In the vertebrate neural tube, a morphogen-induced transcriptional network produces multiple molecularly distinct progenitor domains, each generating different neuronal subtypes. Using an in vitro differentiation system, we defined gene expression signatures of distinct progenitor populations and identified direct gene-regulatory inputs corresponding to locations of specific transcription factor binding. Combined with targeted perturbations of the network, this revealed a mechanism in which a progenitor identity is installed by active repression of the entire transcriptional programs of other neural progenitor fates. In the ventral neural tube, sonic hedgehog (Shh) signaling, together with broadly expressed transcriptional activators, concurrently activates the gene expression programs of several domains. The specific outcome is selected by repressive input provided by Shh-induced transcription factors that act as the key nodes in the network, enabling progenitors to adopt a single definitive identity from several initially permitted options. Together, the data suggest design principles relevant to many developing tissues. PMID:26972603

  10. The role of the concentration camps in the Nazi repression of prostitutes, 1933-9.

    PubMed

    Harris, Victoria

    2010-01-01

    This article uses prostitutes as a case study in order to investigate the role of the early concentration camps as centres of detention for social deviants. In contrasting the intensification of repressive policies towards prostitutes against narratives which demonstrate the unexpectedly lax treatment of these women, it explores what the reasons behind these contradictions might have been, and what this demonstrates about the development of these institutions. It asks the following questions. How and why were prostitutes interned? Which bureaucrats were responsible for incarcerating these women and what did they view the role of the camp to be? Were such policies centrally directed or the product of local decision-making? Through asking these questions, the article explores to what extent these camps were unique as mechanisms for the repression and marginalization of prostitutes.

  11. Structural basis of JAZ repression of MYC transcription factors in jasmonate signaling

    PubMed Central

    Zhang, Feng; Yao, Jian; Ke, Jiyuan; Zhang, Li; Lam, Vinh Q.; Xin, Xiu-Fang; Zhou, X. Edward; Chen, Jian; Brunzelle, Joseph; Griffin, Patrick R.; Zhou, Mingguo; Xu, H. Eric; Melcher, Karsten; He, Sheng Yang

    2015-01-01

    The plant hormone jasmonate (JA) plays crucial roles in regulating plant responses to herbivorous insects and microbial pathogens and is an important regulator of plant growth and development1–7. Key mediators of JA signaling include MYC transcription factors, which are repressed by JAZ transcriptional repressors at the resting state. In the presence of active JA, JAZ proteins function as JA co-receptors by forming a hormone-dependent complex with COI1, the F-box subunit of an SCF-type ubiquitin E3 ligase8–11. The hormone-dependent formation of the COI1–JAZ co-receptor complex leads to ubiquitination and proteasome-dependent degradation of JAZ repressors and release of MYC proteins from transcriptional repression3,10,12. The mechanism by which JAZ proteins repress MYC transcription factors and how JAZ proteins switch between the repressor function in the absence of hormone and the co-receptor function in the presence of hormone remain enigmatic. Here we show that Arabidopsis MYC3 undergoes pronounced conformational changes when bound to the conserved Jas motif of the JAZ9 repressor. The Jas motif, previously shown to bind to hormone as a partially unwound helix, forms a complete α-helix that displaces the N-terminal helix of MYC3 and becomes an integral part of the MYC N-terminal fold. In this position, the Jas helix competitively inhibits MYC3 interaction with the MED25 subunit of the transcriptional Mediator complex. Our study elucidates a novel molecular switch mechanism that governs the repression and activation of a major plant hormone pathway. PMID:26258305

  12. From Sensorimotor Inhibition to Freudian Repression: Insights from Psychosis Applied to Neurosis

    PubMed Central

    Bazan, Ariane

    2012-01-01

    First, three case studies are presented of psychotic patients having in common an inability to hold something down or out. In line with other theories on psychosis, we propose that a key change is at the efference copy system. Going back to Freud’s mental apparatus, we propose that the messages of discharge of the motor neurons, mobilized to direct perception, also called “indications of reality,” are equivalent to the modern efference copies. With this key, the reading of the cases is coherent with the psychodynamic understanding of psychosis, being a downplay of secondary processes, and consequently, a dominance of primary processes. Moreover, putting together the sensorimotor idea of a failure of efference copy-mediated inhibition with the psychoanalytic idea of a failing repression in psychosis, the hypothesis emerges that the attenuation enabled by the efference copy dynamics is, in some instances, the physiological instantiation of repression. Second, we applied this idea to the mental organization in neurosis. Indeed, the efference copy-mediated attenuation is thought to be the mechanism through which sustained activation of an intention, without reaching it – i.e., inhibition of an action – gives rise to mental imagery. Therefore, as inhibition is needed for any targeted action or for normal language understanding, acting in the world, or processing language, structurally induces mental imagery, constituting a subjective unconscious mental reality. Repression is a special instance of inhibition for emotionally threatening stimuli. These stimuli require stronger inhibition, leaving (the attenuation of) the motor intentions totally unanswered, in order to radically prevent execution which would lead to development of excess affect. This inhibition, then, yields a specific type of motor imagery, called “phantoms,” which induce mental preoccupation, as well as symptoms which, especially through their form, refer to the repressed motor fragments

  13. Small RNA as global regulator of carbon catabolite repression in Pseudomonas aeruginosa

    PubMed Central

    Sonnleitner, Elisabeth; Abdou, Laetitia; Haas, Dieter

    2009-01-01

    In the metabolically versatile bacterium Pseudomonas aeruginosa, the RNA-binding protein Crc is involved in catabolite repression of a range of degradative genes, such as amiE (encoding aliphatic amidase). We found that a CA-rich sequence (termed CA motif) in the amiE translation initiation region was important for Crc binding. The small RNA CrcZ (407 nt) containing 5 CA motifs was able to bind the Crc protein with high affinity and to remove it from amiE mRNA in vitro. Overexpression of crcZ relieved catabolite repression in vivo, whereas a crcZ mutation pleiotropically prevented the utilization of several carbon sources. The sigma factor RpoN and the CbrA/CbrB two-component system, which is known to maintain a healthy carbon–nitrogen balance, were necessary for crcZ expression. During growth on succinate, a preferred carbon source, CrcZ expression was low, resulting in catabolite repression of amiE and other genes under Crc control. By contrast, during growth on mannitol, a poor carbon source, elevated CrcZ levels correlated with relief of catabolite repression. During growth on glucose, an intermediate carbon source, CrcZ levels and amiE expression were intermediate between those observed in succinate and mannitol media. Thus, the CbrA–CbrB–CrcZ–Crc system allows the bacterium to adapt differentially to various carbon sources. This cascade also regulated the expression of the xylS (benR) gene, which encodes a transcriptional regulator involved in benzoate degradation, in an analogous way, confirming this cascade's global role. PMID:20080802

  14. Cytokinin Response Factor 6 Represses Cytokinin-Associated Genes during Oxidative Stress1[OPEN

    PubMed Central

    Howton, Timothy C.; Hallmark, H. Tucker; Keshishian, Erika A.; Parish, Alyssa M.; Benkova, Eva; Mukhtar, M. Shahid

    2016-01-01

    Cytokinin is a phytohormone that is well known for its roles in numerous plant growth and developmental processes, yet it has also been linked to abiotic stress response in a less defined manner. Arabidopsis (Arabidopsis thaliana) Cytokinin Response Factor 6 (CRF6) is a cytokinin-responsive AP2/ERF-family transcription factor that, through the cytokinin signaling pathway, plays a key role in the inhibition of dark-induced senescence. CRF6 expression is also induced by oxidative stress, and here we show a novel function for CRF6 in relation to oxidative stress and identify downstream transcriptional targets of CRF6 that are repressed in response to oxidative stress. Analysis of transcriptomic changes in wild-type and crf6 mutant plants treated with H2O2 identified CRF6-dependent differentially expressed transcripts, many of which were repressed rather than induced. Moreover, many repressed genes also show decreased expression in 35S:CRF6 overexpressing plants. Together, these findings suggest that CRF6 functions largely as a transcriptional repressor. Interestingly, among the H2O2 repressed CRF6-dependent transcripts was a set of five genes associated with cytokinin processes: (signaling) ARR6, ARR9, ARR11, (biosynthesis) LOG7, and (transport) ABCG14. We have examined mutants of these cytokinin-associated target genes to reveal novel connections to oxidative stress. Further examination of CRF6-DNA interactions indicated that CRF6 may regulate its targets both directly and indirectly. Together, this shows that CRF6 functions during oxidative stress as a negative regulator to control this cytokinin-associated module of CRF6-dependent genes and establishes a novel connection between cytokinin and oxidative stress response. PMID:27550996

  15. Kinetic profiling of the c-Myc transcriptome and bioinformatic analysis of repressed gene promoters.

    PubMed

    Yap, Chui-Sun; Peterson, Abigail L; Castellani, Gastone; Sedivy, John M; Neretti, Nicola

    2011-07-01

    Mammalian c-Myc is a member of a small family of three related proto-oncogenic transcription factors. c-Myc has an unusually broad array of regulatory functions, which include roles in cell cycle and apoptosis, a variety of metabolic functions, cell differentiation, senescence, and stem cell maintenance. c-Myc modulates the expression of a very large number of genes, but the magnitude of the majority of the regulatory effects is only 2-fold or less. c-Myc can both activate and repress the promoters of its target genes. Identification of genes directly regulated by c-Myc has been an enduring question in the field. We report here microarray expression profiling of a high resolution time course of c-Myc induction, using fibroblast cells in which c-Myc activity can be modulated from null to physiological. The c-Myc transcriptome dataset presented is the largest reported to date with 4,186 differentially regulated genes (1,826 upregulated, 2,360 downregulated, 1% FDR). The gene expression patterns fit well with the known biological functions of c-Myc. We describe several novel findings and present tools for further data mining. Although the mechanisms of transcriptional activation by c-Myc are well understood, how c-Myc represses an even greater number of genes remains incompletely described. One mechanism involves the binding of c-Myc to other, positively acting transcription factors, and interfering with their activities. We identified rapid-response genes likely to be direct c-Myc targets, and analyzed the promoters of the repressed genes to identify transcription factors that could be targets of c-Myc repression.

  16. The Evolutionary Panorama of Organ-Specifically Expressed or Repressed Orthologous Genes in Nine Vertebrate Species

    PubMed Central

    Shen, Libing; Liu, Gangbiao; Zou, Yangyun; Zhou, Zhan; Su, Zhixi; Gu, Xun

    2015-01-01

    RNA sequencing (RNA-Seq) technology provides the detailed transcriptomic information for a biological sample. Using the RNA-Seq data of six organs from nine vertebrate species, we identified a number of organ-specifically expressed or repressed orthologous genes whose expression patterns are mostly conserved across nine species. Our analyses show the following results: (i) About 80% of these genes have a chordate or more ancient origin and more than half of them are the legacy of one or multiple rounds of large-scale gene duplication events. (ii) Their evolutionary rates are shaped by the organ in which they are expressed or repressed, e.g. the genes specially expressed in testis and liver generally evolve more than twice as fast as the ones specially expressed in brain and cerebellum. The organ-specific transcription factors were discriminated from these genes. The ChIP-seq data from the ENCODE project also revealed the transcription-related factors that might be involved in regulating human organ-specifically expressed or repressed genes. Some of them are shared by all six human organs. The comparison of ENCODE data with mouse/chicken ChIP-seq data proposes that organ-specifically expressed or repressed orthologous genes are regulated in various combinatorial fashions in different species, although their expression features are conserved among these species. We found that the duplication events in some gene families might help explain the quick organ/tissue divergence in vertebrate lineage. The phylogenetic analysis of testis-specifically expressed genes suggests that some of them are prone to develop new functions for other organs/tissues. PMID:25679776

  17. Multi-Faceted Characterization of a Novel LuxR-Repressible Promoter Library for Escherichia coli

    PubMed Central

    Zucca, Susanna; Pasotti, Lorenzo; Politi, Nicolò; Casanova, Michela; Mazzini, Giuliano; Cusella De Angelis, Maria Gabriella; Magni, Paolo

    2015-01-01

    The genetic elements regulating the natural quorum sensing (QS) networks of several microorganisms are widely used in synthetic biology to control the behaviour of single cells and engineered bacterial populations via ad-hoc constructed synthetic circuits. A number of novel engineering-inspired biological functions have been implemented and model systems have also been constructed to improve the knowledge on natural QS systems. Synthetic QS-based parts, such as promoters, have been reported in literature, to provide biological components with functions that are not present in nature, like modified induction logic or activation/repression by additional molecules. In this work, a library of promoters that can be repressed by the LuxR protein in presence of the QS autoinducer N-3-oxohexanoyl-L-homoserine lactone (AHL) was reported for Escherichia coli, to expand the toolkit of genetic parts that can be used to engineer novel synthetic QS-based systems. The library was constructed via polymerase chain reaction with highly constrained degenerate oligonucleotides, designed according to the consensus -35 and -10 sequences of a previously reported constitutive promoter library of graded strength, to maximize the probability of obtaining functional clones. All the promoters have a lux box between the -35 and -10 regions, to implement a LuxR-repressible behaviour. Twelve unique library members of graded strength (about 100-fold activity range) were selected to form the final library and they were characterized in several genetic contexts, such as in different plasmids, via different reporter genes, in presence of a LuxR expression cassette in different positions and in response to different AHL concentrations. The new obtained regulatory parts and corresponding data can be exploited by synthetic biologists to implement an artificial AHL-dependent repression of transcription in genetic circuits. The target transcriptional activity can be selected among the available library

  18. Multi-Faceted Characterization of a Novel LuxR-Repressible Promoter Library for Escherichia coli.

    PubMed

    Zucca, Susanna; Pasotti, Lorenzo; Politi, Nicolò; Casanova, Michela; Mazzini, Giuliano; Cusella De Angelis, Maria Gabriella; Magni, Paolo

    2015-01-01

    The genetic elements regulating the natural quorum sensing (QS) networks of several microorganisms are widely used in synthetic biology to control the behaviour of single cells and engineered bacterial populations via ad-hoc constructed synthetic circuits. A number of novel engineering-inspired biological functions have been implemented and model systems have also been constructed to improve the knowledge on natural QS systems. Synthetic QS-based parts, such as promoters, have been reported in literature, to provide biological components with functions that are not present in nature, like modified induction logic or activation/repression by additional molecules. In this work, a library of promoters that can be repressed by the LuxR protein in presence of the QS autoinducer N-3-oxohexanoyl-L-homoserine lactone (AHL) was reported for Escherichia coli, to expand the toolkit of genetic parts that can be used to engineer novel synthetic QS-based systems. The library was constructed via polymerase chain reaction with highly constrained degenerate oligonucleotides, designed according to the consensus -35 and -10 sequences of a previously reported constitutive promoter library of graded strength, to maximize the probability of obtaining functional clones. All the promoters have a lux box between the -35 and -10 regions, to implement a LuxR-repressible behaviour. Twelve unique library members of graded strength (about 100-fold activity range) were selected to form the final library and they were characterized in several genetic contexts, such as in different plasmids, via different reporter genes, in presence of a LuxR expression cassette in different positions and in response to different AHL concentrations. The new obtained regulatory parts and corresponding data can be exploited by synthetic biologists to implement an artificial AHL-dependent repression of transcription in genetic circuits. The target transcriptional activity can be selected among the available library

  19. Tet2 is required to resolve inflammation by recruiting Hdac2 to specifically repress IL-6

    PubMed Central

    Gu, Yan; Li, Xia; Zhao, Dezhi; Liu, Yiqi; Wang, Chunmei; Zhang, Xiang; Su, Xiaoping; Liu, Juan; Ge, Wei; Levine, Ross L.; Li, Nan; Cao, Xuetao

    2015-01-01

    Epigenetic modifiers have fundamental roles in defining unique cellular identity through the establishment and maintenance of lineage-specific chromatin and methylation status1. Several DNA modifications such as 5-hydroxymethylcytosine (5hmC) are catalysed by the ten eleven translocation (Tet) methylcytosine dioxygenase family members2, and the roles of Tet proteins in regulating chromatin architecture and gene transcription independently of DNA methylation have been gradually uncovered3. However, the regulation of immunity and inflammation by Tet proteins independent of their role in modulating DNA methylation remains largely unknown. Here we show that Tet2 selectively mediates active repression of interleukin-6 (IL-6) transcription during inflammation resolution in innate myeloid cells, including dendritic cells and macrophages. Loss of Tet2 resulted in the upregulation of several inflammatory mediators, including IL-6, at late phase during the response to lipopolysaccharide challenge. Tet2-deficient mice were more susceptible to endotoxin shock and dextran-sulfate-sodium-induced colitis, displaying a more severe inflammatory phenotype and increased IL-6 production compared to wild-type mice. IκBζ, an IL-6-specific transcription factor, mediated specific targeting of Tet2 to the Il6 promoter, further indicating opposite regulatory roles of IκBζ at initial and resolution phases of inflammation. For the repression mechanism, independent of DNA methylation and hydroxymethylation, Tet2 recruited Hdac2 and repressed transcription of Il6 via histone deacetylation. We provide mechanistic evidence for the gene-specific transcription repression activity of Tet2 via histone deacetylation and for the prevention of constant transcription activation at the chromatin level for resolving inflammation. PMID:26287468

  20. Norepinephrine represses the expression of toxA and the siderophore genes in Pseudomonas aeruginosa.

    PubMed

    Li, Wang; Lyte, Mark; Freestone, Primrose P; Ajmal, Aziba; Colmer-Hamood, Jane A; Hamood, Abdul N

    2009-10-01

    Among the different extracellular virulence factors produced by Pseudomonas aeruginosa are exotoxin A (ETA) and the pyoverdine and pyochelin siderophores. Production of ETA and the siderophores requires the function of the iron-starvation sigma factor PvdS, the transcriptional activator RegA, and the AraC-activator PchR. Iron represses the production of ETA and the siderophores by repressing the expression of pvdS, regA, and pchR. PvdS regulates the expression of the ETA gene, toxA, regA, and the pyoverdine synthesis genes. The catecholamine norepinephrine enhances the growth of pathogenic bacteria by transferring iron from host-binding proteins. In this study, we elucidated the mechanism by which norepinephrine and other catecholamines induce P. aeruginosa growth. We also investigated whether norepinephrine regulates the expression of toxA and the siderophore genes, and the mechanism of this regulation. Norepinephrine enhanced the growth of P. aeruginosa by supplying iron from transferrin. This provision of iron repressed the expression of toxA, the pyoverdine genes pvdD and pvdE, and their regulators, pvdS, regA, and pchR, suggesting that norepinephrine accomplishes this repression through PvdS and PchR. Additionally, norepinephrine bypassed PvdS and supported the growth of a pvdS deletion mutant, indicating that norepinephrine transfers iron to P. aeruginosa independent of pyoverdine. Thus, norepinephrine apparently influences the pathogenesis of P. aeruginosa by affecting its pattern of growth and the production of virulence factors. PMID:19686346

  1. Active repression by RARγ signaling is required for vertebrate axial elongation.

    PubMed

    Janesick, Amanda; Nguyen, Tuyen T L; Aisaki, Ken-ichi; Igarashi, Katsuhide; Kitajima, Satoshi; Chandraratna, Roshantha A S; Kanno, Jun; Blumberg, Bruce

    2014-06-01

    Retinoic acid receptor gamma 2 (RARγ2) is the major RAR isoform expressed throughout the caudal axial progenitor domain in vertebrates. During a microarray screen to identify RAR targets, we identified a subset of genes that pattern caudal structures or promote axial elongation and are upregulated by increased RAR-mediated repression. Previous studies have suggested that RAR is present in the caudal domain, but is quiescent until its activation in late stage embryos terminates axial elongation. By contrast, we show here that RARγ2 is engaged in all stages of axial elongation, not solely as a terminator of axial growth. In the absence of RA, RARγ2 represses transcriptional activity in vivo and maintains the pool of caudal progenitor cells and presomitic mesoderm. In the presence of RA, RARγ2 serves as an activator, facilitating somite differentiation. Treatment with an RARγ-selective inverse agonist (NRX205099) or overexpression of dominant-negative RARγ increases the expression of posterior Hox genes and that of marker genes for presomitic mesoderm and the chordoneural hinge. Conversely, when RAR-mediated repression is reduced by overexpressing a dominant-negative co-repressor (c-SMRT), a constitutively active RAR (VP16-RARγ2), or by treatment with an RARγ-selective agonist (NRX204647), expression of caudal genes is diminished and extension of the body axis is prematurely terminated. Hence, gene repression mediated by the unliganded RARγ2-co-repressor complex constitutes a novel mechanism to regulate and facilitate the correct expression levels and spatial restriction of key genes that maintain the caudal progenitor pool during axial elongation in Xenopus embryos.

  2. Endothelial miR-17∼92 cluster negatively regulates arteriogenesis via miRNA-19 repression of WNT signaling

    PubMed Central

    Landskroner-Eiger, Shira; Qiu, Cong; Perrotta, Paola; Siragusa, Mauro; Lee, Monica Y.; Ulrich, Victoria; Luciano, Amelia K.; Zhuang, Zhen W.; Corti, Federico; Simons, Michael; Montgomery, Rusty L.; Wu, Dianqing; Yu, Jun; Sessa, William C.

    2015-01-01

    The contribution of endothelial-derived miR-17∼92 to ischemia-induced arteriogenesis has not been investigated in an in vivo model. In the present study, we demonstrate a critical role for the endothelial-derived miR-17∼92 cluster in shaping physiological and ischemia-triggered arteriogenesis. Endothelial-specific deletion of miR-17∼92 results in an increase in collateral density limbs and hearts and in ischemic limbs compared with control mice, and consequently improves blood flow recovery. Individual cluster components positively or negatively regulate endothelial cell (EC) functions in vitro, and, remarkably, ECs lacking the cluster spontaneously form cords in a manner rescued by miR-17a, -18a, and -19a. Using both in vitro and in vivo analyses, we identified FZD4 and LRP6 as targets of miR-19a/b. Both of these targets were up-regulated in 17∼92 KO ECs compared with control ECs, and both were shown to be targeted by miR-19 using luciferase assays. We demonstrate that miR-19a negatively regulates FZD4, its coreceptor LRP6, and WNT signaling, and that antagonism of miR-19a/b in aged mice improves blood flow recovery after ischemia and reduces repression of these targets. Collectively, these data provide insights into miRNA regulation of arterialization and highlight the importance of vascular WNT signaling in maintaining arterial blood flow. PMID:26417068

  3. The transcription factor NRSF contributes to epileptogenesis by selective repression of a subset of target genes.

    PubMed

    McClelland, Shawn; Brennan, Gary P; Dubé, Celine; Rajpara, Seeta; Iyer, Shruti; Richichi, Cristina; Bernard, Christophe; Baram, Tallie Z

    2014-01-01

    The mechanisms generating epileptic neuronal networks following insults such as severe seizures are unknown. We have previously shown that interfering with the function of the neuron-restrictive silencer factor (NRSF/REST), an important transcription factor that influences neuronal phenotype, attenuated development of this disorder. In this study, we found that epilepsy-provoking seizures increased the low NRSF levels in mature hippocampus several fold yet surprisingly, provoked repression of only a subset (∼10%) of potential NRSF target genes. Accordingly, the repressed gene-set was rescued when NRSF binding to chromatin was blocked. Unexpectedly, genes selectively repressed by NRSF had mid-range binding frequencies to the repressor, a property that rendered them sensitive to moderate fluctuations of NRSF levels. Genes selectively regulated by NRSF during epileptogenesis coded for ion channels, receptors, and other crucial contributors to neuronal function. Thus, dynamic, selective regulation of NRSF target genes may play a role in influencing neuronal properties in pathological and physiological contexts. PMID:25117540

  4. Snail Recruits Ring1B to Mediate Transcriptional Repression and Cell Migration in Pancreatic Cancer Cells

    PubMed Central

    Chen, Jiangzhi; Xu, Hong; Zou, Xiuqun; Wang, Jiamin; Zhu, Yi; Chen, Hao; Shen, Baiyong; Deng, Xiaxing; Zhou, Aiwu; Chin, Y. Eugene; Rauscher, Frank J.; Peng, Chenghong; Hou, Zhaoyuan

    2014-01-01

    Transcriptional repressor Snail is a master regulator of epithelial–mesenchymal transition (EMT), yet the epigenetic mechanism governing Snail to induce EMT is not well understood. Here, we report that in pancreatic ductal adenocarcinoma (PDAC), elevated levels of the ubiquitin E3 ligase Ring1B and Snail, along with elevated monoubiquitination of H2A at K119 (H2AK119Ub1), are highly correlated with poor survival. Mechanistic investigations identified Ring1B as a Snail-interacting protein and showed that the carboxyl zinc fingers of Snail recruit Ring1B and its paralog Ring1A to repress its target promoters. Simultaneous depletion of Ring1A and Ring1B in pancreatic cancer cells decreased Snail binding to the target chromatin, abolished H2AK119Ub1 modification, and thereby compromised Snail-mediated transcriptional repression and cell migration. We found that Ring1B and the SNAG-associated chromatin modifier EZH2 formed distinct protein complexes with Snail and that EZH2 was required for Snail-Ring1A/B recruitment to the target promoter. Collectively, our results unravel an epigenetic mechanism underlying transcriptional repression by Snail, suggest Ring1A/B as a candidate therapeutic target, and identify H2AK119Ub1 as a potential biomarker for PDAC diagnosis and prognosis. Cancer Res; 74(16); 4353-63. ©2014 AACR PMID:24903147

  5. The nuclear periphery of embryonic stem cells is a transcriptionally permissive and repressive compartment

    PubMed Central

    Luo, Li; Gassman, Katherine L.; Petell, Lydia M.; Wilson, Christian L.; Bewersdorf, Joerg; Shopland, Lindsay S.

    2009-01-01

    Summary Chromatin adapts a distinct structure and epigenetic state in embryonic stem cells (ESCs), but how chromatin is three-dimensionally organized within the ESC nucleus is poorly understood. Because nuclear location can influence gene expression, we examined the nuclear distributions of chromatin with key epigenetic marks in ESC nuclei. We focused on chromatin at the nuclear periphery, a compartment that represses some but not all associated genes and accumulates facultative heterochromatin in differentiated cells. Using a quantitative, cytological approach, we measured the nuclear distributions of genes in undifferentiated mouse ESCs according to epigenetic state and transcriptional activity. We found that trimethyl histone H3 lysine 27 (H3K27-Me3), which marks repressed gene promoters, is enriched at the ESC nuclear periphery. In addition, this compartment contains 10-15% of chromatin with active epigenetic marks and hundreds of transcription sites. Surprisingly, comparisons with differentiated cell types revealed similar nuclear distributions of active chromatin. By contrast, H3K27-Me3 was less concentrated at the nuclear peripheries of differentiated cells. These findings demonstrate that the nuclear periphery is an epigenetically dynamic compartment that might be distinctly marked in pluripotent ESCs. In addition, our data indicate that the nuclear peripheries of multiple cell types can contain a significant fraction of both active and repressed genes. PMID:19773359

  6. Neutrophil elastase, an innate immunity effector molecule, represses flagellin transcription in Pseudomonas aeruginosa.

    PubMed

    Sonawane, Avinash; Jyot, Jeevan; During, Russell; Ramphal, Reuben

    2006-12-01

    Recognition of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors triggers an innate immune response to colonizing or invading bacteria. Conversely, many bacteria have evolved mechanisms to dampen this response by downregulating the synthesis of such PAMPs. We have previously demonstrated that Pseudomonas aeruginosa growing in mucopurulent human respiratory mucus from cystic fibrosis patients represses the expression of its flagellin, a potent stimulant of the innate immune response. Here we demonstrate that this phenomenon occurs in response to the presence of neutrophil elastase in such mucus. Nonpurulent mucus from animals had no such repressive effect. Furthermore, lysed neutrophils from human blood reproduced the flagellin-repressive effect ex mucus and, significantly, had no effect on the viability of this organism. Neutrophil elastase, a component of the innate host defense system, has been described to be bactericidal for gram-negative bacteria and to degrade bacterial virulence factors. Thus, the resistance of P. aeruginosa to the bactericidal effect of neutrophil elastase, as well as this organism's ability to sense this enzyme's presence and downregulate the synthesis of a PAMP, may be the key factors in allowing P. aeruginosa to colonize the lungs. These findings demonstrate the dynamic nature of this bacterium's response to host defenses that ensures its success as a colonizer and also highlights the dual nature of defense molecules that confer advantages and disadvantages to both hosts and pathogens. PMID:16982831

  7. Polycomb Repressive Complex 2 Regulates Lineage Fidelity during Embryonic Stem Cell Differentiation

    PubMed Central

    Thornton, Seraphim R.; Butty, Vincent L.; Levine, Stuart S.; Boyer, Laurie A.

    2014-01-01

    Polycomb Repressive Complex 2 (PRC2) catalyzes histone H3 lysine 27 tri-methylation (H3K27me3), an epigenetic modification associated with gene repression. H3K27me3 is enriched at the promoters of a large cohort of developmental genes in embryonic stem cells (ESCs). Loss of H3K27me3 leads to a failure of ESCs to properly differentiate, making it difficult to determine the precise roles of PRC2 during lineage commitment. Moreover, while studies suggest that PRC2 prevents DNA methylation, how these two epigenetic regulators coordinate to regulate lineage programs is poorly understood. Using several PRC2 mutant ESC lines that maintain varying levels of H3K27me3, we found that partial maintenance of H3K27me3 allowed for proper temporal activation of lineage genes during directed differentiation of ESCs to spinal motor neurons (SMNs). In contrast, genes that function to specify other lineages failed to be repressed in these cells, suggesting that PRC2 is also necessary for lineage fidelity. We also found that loss of H3K27me3 leads to a modest gain in DNA methylation at PRC2 target regions in both ESCs and in SMNs. Our study demonstrates a critical role for PRC2 in safeguarding lineage decisions and in protecting genes against inappropriate DNA methylation. PMID:25333635

  8. Repression of early lateral root initiation events by transient water deficit in barley and maize

    PubMed Central

    Babé, Aurélie; Lavigne, Tristan; Séverin, Jean-Philippe; Nagel, Kerstin A.; Walter, Achim; Chaumont, François; Batoko, Henri; Beeckman, Tom; Draye, Xavier

    2012-01-01

    The formation of lateral roots (LRs) is a key driver of root system architecture and developmental plasticity. The first stage of LR formation, which leads to the acquisition of founder cell identity in the pericycle, is the primary determinant of root branching patterns. The fact that initiation events occur asynchronously in a very small number of cells inside the parent root has been a major difficulty in the study of the molecular regulation of branching patterns. Inducible systems that trigger synchronous lateral formation at predictable sites have proven extremely valuable in Arabidopsis to decipher the first steps of LR formation. Here, we present a LR repression system for cereals that relies on a transient water-deficit treatment, which blocks LR initiation before the first formative divisions. Using a time-lapse approach, we analysed the dynamics of this repression along growing roots and were able to show that it targets a very narrow developmental window of the initiation process. Interestingly, the repression can be exploited to obtain negative control root samples where LR initiation is absent. This system could be instrumental in the analysis of the molecular basis of drought-responsive as well as intrinsic pathways of LR formation in cereals. PMID:22527396

  9. A BEN-domain-containing protein associates with heterochromatin and represses transcription.

    PubMed

    Sathyan, Kizhakke M; Shen, Zhen; Tripathi, Vidisha; Prasanth, Kannanganattu V; Prasanth, Supriya G

    2011-09-15

    In eukaryotes, higher order chromatin structure governs crucial cellular processes including DNA replication, transcription and post-transcriptional gene regulation. Specific chromatin-interacting proteins play vital roles in the maintenance of chromatin structure. We have identified BEND3, a quadruple BEN domain-containing protein that is highly conserved amongst vertebrates. BEND3 colocalizes with HP1 and H3 trimethylated at K9 at heterochromatic regions in mammalian cells. Using an in vivo gene locus, we have been able to demonstrate that BEND3 associates with the locus only when it is heterochromatic and dissociates upon activation of transcription. Furthermore, tethering BEND3 inhibits transcription from the locus, indicating that BEND3 is involved in transcriptional repression through its interaction with histone deacetylases and Sall4, a transcription repressor. We further demonstrate that BEND3 is SUMOylated and that such modifications are essential for its role in transcriptional repression. Finally, overexpression of BEND3 causes premature chromatin condensation and extensive heterochromatinization, resulting in cell cycle arrest. Taken together, our data demonstrate the role of a novel heterochromatin-associated protein in transcriptional repression.

  10. A response regulator promotes Francisella tularensis intramacrophage growth by repressing an anti-virulence factor.

    PubMed

    Ramsey, Kathryn M; Dove, Simon L

    2016-08-01

    The orphan response regulator PmrA is essential for the intramacrophage growth and survival of Francisella tularensis. PmrA was thought to promote intramacrophage growth by binding directly to promoters on the Francisella Pathogenicity Island (FPI) and positively regulating the expression of FPI genes, which encode a Type VI secretion system required for intramacrophage growth. Using both ChIP-Seq and RNA-Seq we identify those regions of the F. tularensis chromosome occupied by PmrA and those genes that are regulated by PmrA. We find that PmrA associates with 252 distinct regions of the F. tularensis chromosome, but exerts regulatory effects at only a few of these locations. Rather than by functioning directly as an activator of FPI gene expression we present evidence that PmrA promotes intramacrophage growth by repressing the expression of a single target gene we refer to as priM (PmrA-repressed inhibitor of intramacrophage growth). Our findings thus indicate that the role of PmrA in facilitating intracellular growth is to repress a previously unknown anti-virulence factor. PriM is the first bacterially encoded factor to be described that can interfere with the intramacrophage growth and survival of F. tularensis. PMID:27169554

  11. Separate necdin domains bind ARNT2 and HIF1{alpha} and repress transcription

    SciTech Connect

    Friedman, Eitan R.; Fan Chenming

    2007-11-09

    PWS is caused by the loss of expression of a set of maternally imprinted genes including NECDIN (NDN). NDN is expressed in post-mitotic neurons and plays an essential role in PWS as mouse models lacking only the Ndn gene mimic aspects of this disease. Patients haploid for SIM1 develop a PW-like syndrome. Here, we report that NDN directly interacts with ARNT2, a bHLH-PAS protein and dimer partner for SIM1. We also found that NDN can interact with HIF1{alpha}. We showed that NDN can repress transcriptional activation mediated by ARNT2:SIM1 as well as ARNT2:HIF1{alpha}. The N-terminal 115 residues of NDN are sufficient for interaction with the bHLH domains of ARNT2 or HIF1{alpha} but not for transcriptional repression. Using GAL4-NDN fusion proteins, we determined that NDN possesses multiple repression domains. We thus propose that NDN regulates neuronal function and hypoxic response by regulating the activities of the ARNT2:SIM1 and ARNT2:HIF1{alpha} dimers, respectively.

  12. RNAi mediates post-transcriptional repression of gene expression in fission yeast Schizosaccharomyces pombe

    SciTech Connect

    Smialowska, Agata; Djupedal, Ingela; Wang, Jingwen; Kylsten, Per; Swoboda, Peter; Ekwall, Karl

    2014-02-07

    Highlights: • Protein coding genes accumulate anti-sense sRNAs in fission yeast S. pombe. • RNAi represses protein-coding genes in S. pombe. • RNAi-mediated gene repression is post-transcriptional. - Abstract: RNA interference (RNAi) is a gene silencing mechanism conserved from fungi to mammals. Small interfering RNAs are products and mediators of the RNAi pathway and act as specificity factors in recruiting effector complexes. The Schizosaccharomyces pombe genome encodes one of each of the core RNAi proteins, Dicer, Argonaute and RNA-dependent RNA polymerase (dcr1, ago1, rdp1). Even though the function of RNAi in heterochromatin assembly in S. pombe is established, its role in controlling gene expression is elusive. Here, we report the identification of small RNAs mapped anti-sense to protein coding genes in fission yeast. We demonstrate that these genes are up-regulated at the protein level in RNAi mutants, while their mRNA levels are not significantly changed. We show that the repression by RNAi is not a result of heterochromatin formation. Thus, we conclude that RNAi is involved in post-transcriptional gene silencing in S. pombe.

  13. Generation of a glucose de-repressed mutant of Trichoderma reesei using disparity mutagenesis.

    PubMed

    Iwakuma, Hidekazu; Koyama, Yoshiyuki; Miyachi, Ayako; Nasukawa, Masashi; Matsumoto, Hitoshi; Yano, Shuntaro; Ogihara, Jun; Kasumi, Takafumi

    2016-01-01

    We obtained a novel glucose de-repressed mutant of Trichoderma reesei using disparity mutagenesis. A plasmid containing DNA polymerase δ lacking proofreading activity, and AMAI, an autonomously replicating sequence was introduced into T. reesei ATCC66589. The rate of mutation evaluated with 5-fluoroorotic acid resistance was approximately 30-fold higher than that obtained by UV irradiation. The transformants harboring incompetent DNA polymerase δ were then selected on 2-deoxyglucose agar plates with hygromycin B. The pNP-lactoside hydrolyzing activities of mutants were 2 to 5-fold higher than the parent in liquid medium containing glucose. Notably, the amino acid sequence of cre1, a key gene involved in glucose repression, was identical in the mutant and parent strains, and further, the cre1 expression levels was not abolished in the mutant. Taken together, these results demonstrate that the strains of T. reesei generated by disparity mutagenesis are glucose de-repressed variants that contain mutations in yet-unidentified factors other than cre1.

  14. p27(Kip1) directly represses Sox2 during embryonic stem cell differentiation.

    PubMed

    Li, Han; Collado, Manuel; Villasante, Aranzazu; Matheu, Ander; Lynch, Cian J; Cañamero, Marta; Rizzoti, Karine; Carneiro, Carmen; Martínez, Gloria; Vidal, Anxo; Lovell-Badge, Robin; Serrano, Manuel

    2012-12-01

    The mechanisms responsible for the transcriptional silencing of pluripotency genes in differentiated cells are poorly understood. We have observed that cells lacking the tumor suppressor p27 can be reprogrammed into induced pluripotent stem cells (iPSCs) in the absence of ectopic Sox2. Interestingly, cells and tissues from p27 null mice, including brain, lung, and retina, present an elevated basal expression of Sox2, suggesting that p27 contributes to the repression of Sox2. Furthermore, p27 null iPSCs fail to fully repress Sox2 upon differentiation. Mechanistically, we have found that upon differentiation p27 associates to the SRR2 enhancer of the Sox2 gene together with a p130-E2F4-SIN3A repressive complex. Finally, Sox2 haploinsufficiency genetically rescues some of the phenotypes characteristic of p27 null mice, including gigantism, pituitary hyperplasia, pituitary tumors, and retinal defects. Collectively, these results demonstrate an unprecedented connection between p27 and Sox2 relevant for reprogramming and cancer and for understanding human pathologies associated with p27 germline mutations. PMID:23217425

  15. Light represses transcription of asparagine synthetase genes in photosynthetic and nonphotosynthetic organs of plants

    SciTech Connect

    Tsai, Fongying; Coruzzi, G. )

    1991-10-01

    Asparagine synthetase (AS) mRNA in Pisum sativum accumulates preferentially in plants grown in the dark. Nuclear run-on experiments demonstrate that expression of both the AS1 and AS2 genes is negatively regulated by light at the level of transcription. A decrease in the transcriptional rate of the AS1 gene can be detected as early as 20 min after exposure to light. Time course experiments reveal that the levels of AS mRNA fluctuate dramatically during a normal light/dark cycle. This is due to a direct effect of light and not to changes associated with circadian rhythm. A novel finding is that the light-repressed expression of the AS1 gene is as dramatic nonphotosynthetic organs such as roots as it is in leaves. Experiments demonstrate that the small amount of light which passes through the soil is sufficient to repress AS1 expression in roots, indicating that light has a direct effect on AS1 gene expression in roots. The negative regulation of AS gene expression by light was shown to be a general phenomenon in plants which also occurs in nonlegumes such as Nicotiana plumbaginifolia and Nicotiana tabacum. Thus, the AS genes can serve as a model with which to dissect the molecular basis for light-regulated transcriptional repression in plants.

  16. A BEN-domain-containing protein associates with heterochromatin and represses transcription.

    PubMed

    Sathyan, Kizhakke M; Shen, Zhen; Tripathi, Vidisha; Prasanth, Kannanganattu V; Prasanth, Supriya G

    2011-09-15

    In eukaryotes, higher order chromatin structure governs crucial cellular processes including DNA replication, transcription and post-transcriptional gene regulation. Specific chromatin-interacting proteins play vital roles in the maintenance of chromatin structure. We have identified BEND3, a quadruple BEN domain-containing protein that is highly conserved amongst vertebrates. BEND3 colocalizes with HP1 and H3 trimethylated at K9 at heterochromatic regions in mammalian cells. Using an in vivo gene locus, we have been able to demonstrate that BEND3 associates with the locus only when it is heterochromatic and dissociates upon activation of transcription. Furthermore, tethering BEND3 inhibits transcription from the locus, indicating that BEND3 is involved in transcriptional repression through its interaction with histone deacetylases and Sall4, a transcription repressor. We further demonstrate that BEND3 is SUMOylated and that such modifications are essential for its role in transcriptional repression. Finally, overexpression of BEND3 causes premature chromatin condensation and extensive heterochromatinization, resulting in cell cycle arrest. Taken together, our data demonstrate the role of a novel heterochromatin-associated protein in transcriptional repression. PMID:21914818

  17. Drosophila PTB promotes formation of high-order RNP particles and represses oskar translation

    PubMed Central

    Besse, Florence; López de Quinto, Sonia; Marchand, Virginie; Trucco, Alvar; Ephrussi, Anne

    2009-01-01

    Local translation of asymmetrically enriched mRNAs is a powerful mechanism for functional polarization of the cell. In Drosophila, exclusive accumulation of Oskar protein at the posterior pole of the oocyte is essential for development of the future embryo. This is achieved by the formation of a dynamic oskar ribonucleoprotein (RNP) complex regulating the transport of oskar mRNA, its translational repression while unlocalized, and its translational activation upon arrival at the posterior pole. We identified the nucleo–cytoplasmic shuttling protein PTB (polypyrimidine tract-binding protein)/hnRNP I as a new factor associating with the oskar RNP in vivo. While PTB function is largely dispensable for oskar mRNA transport, it is necessary for translational repression of the localizing mRNA. Unexpectedly, a cytoplasmic form of PTB can associate with oskar mRNA and repress its translation, suggesting that nuclear recruitment of PTB to oskar complexes is not required for its regulatory function. Furthermore, PTB binds directly to multiple sites along the oskar 3′ untranslated region and mediates assembly of high-order complexes containing multiple oskar RNA molecules in vivo. Thus, PTB is a key structural component of oskar RNP complexes that dually controls formation of high-order RNP particles and translational silencing. PMID:19131435

  18. Liganded RAR{alpha} and RAR{gamma} interact with but are repressed by TNIP1

    SciTech Connect

    Gurevich, Igor; Aneskievich, Brian J.

    2009-11-20

    Nuclear receptor (NR) transcriptional activity is controlled by agonist binding and concomitant exchange of receptor-associating corepressor proteins for NR box-containing, receptor AF-2-targeting coactivator proteins. We report here that TNIP1 is an atypical NR coregulator. Requirements for TNIP1-RAR interaction-its NR boxes, ligand, and the receptor's AF-2 domain-are characteristic of coactivators. However, TNIP1 reduces RAR activity. Repression is partially relieved by SRC1, suggesting interference with coactivator recruitment as a mechanism of TNIP1 repression. TNIP1 does not bind RXR{alpha} and RAR{alpha} AF-2 domain, necessary for that receptor's association with TNIP1, is insufficient to confer upon RXR{alpha} interaction with TNIP1. Preferential interaction of RAR{alpha} over RAR{gamma} with TNIP1 can be mapped to RAR{alpha} ligand binding domain helices 5-9 and suggests regions outside the receptor helix 12 modulate interaction of NRs and NR box-containing corepressors. TNIP1 repression of RARs in the presence of RA places it in a small category of corepressors of agonist-bound NRs.

  19. Protein kinase A represses skeletal myogenesis by targeting myocyte enhancer factor 2D.

    PubMed

    Du, Min; Perry, Robert L S; Nowacki, Nathaniel B; Gordon, Joseph W; Salma, Jahan; Zhao, Jianzhong; Aziz, Arif; Chan, Joseph; Siu, K W Michael; McDermott, John C

    2008-05-01

    Activation of protein kinase A (PKA) by elevation of the intracellular cyclic AMP (cAMP) level inhibits skeletal myogenesis. Previously, an indirect modulation of the myogenic regulatory factors (MRFs) was implicated as the mechanism. Because myocyte enhancer factor 2 (MEF2) proteins are key regulators of myogenesis and obligatory partners for the MRFs, here we assessed whether these proteins could be involved in PKA-mediated myogenic repression. Initially, in silico analysis revealed several consensus PKA phosphoacceptor sites on MEF2, and subsequent analysis by in vitro kinase assays indicated that PKA directly and efficiently phosphorylates MEF2D. Using mass spectrometric determination of phosphorylated residues, we document that MEF2D serine 121 and serine 190 are targeted by PKA. Transcriptional reporter gene assays to assess MEF2D function revealed that PKA potently represses the transactivation properties of MEF2D. Furthermore, engineered mutation of MEF2D PKA phosphoacceptor sites (serines 121 and 190 to alanine) rendered a PKA-resistant MEF2D protein, which efficiently rescues myogenesis from PKA-mediated repression. Concomitantly, increased intracellular cAMP-mediated PKA activation also resulted in an enhanced nuclear accumulation of histone deacetylase 4 (HDAC4) and a subsequent increase in the MEF2D-HDAC4 repressor complex. Collectively, these data identify MEF2D as a primary target of PKA signaling in myoblasts that leads to inhibition of the skeletal muscle differentiation program.

  20. Blue light-mediated transcriptional activation and repression of gene expression in bacteria.

    PubMed

    Jayaraman, Premkumar; Devarajan, Kavya; Chua, Tze Kwang; Zhang, Hanzhong; Gunawan, Erry; Poh, Chueh Loo

    2016-08-19

    Light-regulated modules offer unprecedented new ways to control cellular behavior in precise spatial and temporal resolution. The availability of such tools may dramatically accelerate the progression of synthetic biology applications. Nonetheless, current optogenetic toolbox of prokaryotes has potential issues such as lack of rapid and switchable control, less portable, low dynamic expression and limited parts. To address these shortcomings, we have engineered a novel bidirectional promoter system for Escherichia coli that can be induced or repressed rapidly and reversibly using the blue light dependent DNA-binding protein EL222. We demonstrated that by modulating the dosage of light pulses or intensity we could control the level of gene expression precisely. We show that both light-inducible and repressible system can function in parallel with high spatial precision in a single cell and can be switched stably between ON- and OFF-states by repetitive pulses of blue light. In addition, the light-inducible and repressible expression kinetics were quantitatively analysed using a mathematical model. We further apply the system, for the first time, to optogenetically synchronize two receiver cells performing different logic behaviors over time using blue light as a molecular clock signal. Overall, our modular approach layers a transformative platform for next-generation light-controllable synthetic biology systems in prokaryotes. PMID:27353329

  1. Structural insights into gene repression by the orphan nuclear receptor SHP.

    PubMed

    Zhi, Xiaoyong; Zhou, X Edward; He, Yuanzheng; Zechner, Christoph; Suino-Powell, Kelly M; Kliewer, Steven A; Melcher, Karsten; Mangelsdorf, David J; Xu, H Eric

    2014-01-14

    Small heterodimer partner (SHP) is an orphan nuclear receptor that functions as a transcriptional repressor to regulate bile acid and cholesterol homeostasis. Although the precise mechanism whereby SHP represses transcription is not known, E1A-like inhibitor of differentiation (EID1) was isolated as a SHP-interacting protein and implicated in SHP repression. Here we present the crystal structure of SHP in complex with EID1, which reveals an unexpected EID1-binding site on SHP. Unlike the classical cofactor-binding site near the C-terminal helix H12, the EID1-binding site is located at the N terminus of the receptor, where EID1 mimics helix H1 of the nuclear receptor ligand-binding domain. The residues composing the SHP-EID1 interface are highly conserved. Their mutation diminishes SHP-EID1 interactions and affects SHP repressor activity. Together, these results provide important structural insights into SHP cofactor recruitment and repressor function and reveal a conserved protein interface that is likely to have broad implications for transcriptional repression by orphan nuclear receptors.

  2. To suppress, or not to suppress? That is repression: controlling intrusive thoughts in addictive behaviour.

    PubMed

    Moss, Antony C; Erskine, James A K; Albery, Ian P; Allen, James Richard; Georgiou, George J

    2015-05-01

    Research to understand how individuals cope with intrusive negative or threatening thoughts suggests a variety of different cognitive strategies aimed at thought control. In this review, two of these strategies--thought suppression and repressive coping--are discussed in the context of addictive behaviour. Thought suppression involves conscious, volitional attempts to expel a thought from awareness, whereas repressive coping, which involves the avoidance of thoughts without the corresponding conscious intention, appears to be a far more automated process. Whilst there has been an emerging body of research exploring the role of thought suppression in addictive behaviour, there remains a dearth of research which has considered the role of repressive coping in the development of, and recovery from, addiction. Based on a review of the literature, and a discussion of the supposed mechanisms which underpin these strategies for exercising mental control, a conceptual model is proposed which posits a potential common mechanism. This model makes a number of predictions which require exploration in future research to fully understand the cognitive strategies utilised by individuals to control intrusive thoughts related to their addictive behaviour.

  3. Different cell cycle modifications repress apoptosis at different steps independent of developmental signaling in Drosophila

    PubMed Central

    Qi, Suozhi; Calvi, Brian R.

    2016-01-01

    Apoptotic cell death is important for the normal development of a variety of organisms. Apoptosis is also a response to DNA damage and an important barrier to oncogenesis. The apoptotic response to DNA damage is dampened in specific cell types during development. Developmental signaling pathways can repress apoptosis, and reduced cell proliferation also correlates with a lower apoptotic response. However, because developmental signaling regulates both cell proliferation and apoptosis, the relative contribution of cell division to the apoptotic response has been hard to discern in vivo. Here we use Drosophila oogenesis as an in vivo model system to determine the extent to which cell proliferation influences the apoptotic response to DNA damage. We find that different types of cell cycle modifications are sufficient to repress the apoptotic response to ionizing radiation independent of developmental signaling. The step(s) at which the apoptosis pathway was repressed depended on the type of cell cycle modification—either upstream or downstream of expression of the p53-regulated proapoptotic genes. Our findings have important implications for understanding the coordination of cell proliferation with the apoptotic response in development and disease, including cancer and the tissue-specific responses to radiation therapy. PMID:27075174

  4. RYBP stimulates PRC1 to shape chromatin-based communication between Polycomb repressive complexes

    PubMed Central

    Rose, Nathan R; King, Hamish W; Blackledge, Neil P; Fursova, Nadezda A; Ember, Katherine JI; Fischer, Roman; Kessler, Benedikt M; Klose, Robert J

    2016-01-01

    Polycomb group (PcG) proteins function as chromatin-based transcriptional repressors that are essential for normal gene regulation during development. However, how these systems function to achieve transcriptional regulation remains very poorly understood. Here, we discover that the histone H2AK119 E3 ubiquitin ligase activity of Polycomb repressive complex 1 (PRC1) is defined by the composition of its catalytic subunits and is highly regulated by RYBP/YAF2-dependent stimulation. In mouse embryonic stem cells, RYBP plays a central role in shaping H2AK119 mono-ubiquitylation at PcG targets and underpins an activity-based communication between PRC1 and Polycomb repressive complex 2 (PRC2) which is required for normal histone H3 lysine 27 trimethylation (H3K27me3). Without normal histone modification-dependent communication between PRC1 and PRC2, repressive Polycomb chromatin domains can erode, rendering target genes susceptible to inappropriate gene expression signals. This suggests that activity-based communication and histone modification-dependent thresholds create a localized form of epigenetic memory required for normal PcG chromatin domain function in gene regulation. DOI: http://dx.doi.org/10.7554/eLife.18591.001 PMID:27705745

  5. The transcription factor NRSF contributes to epileptogenesis by selective repression of a subset of target genes

    PubMed Central

    McClelland, Shawn; Brennan, Gary P; Dubé, Celine; Rajpara, Seeta; Iyer, Shruti; Richichi, Cristina; Bernard, Christophe; Baram, Tallie Z

    2014-01-01

    The mechanisms generating epileptic neuronal networks following insults such as severe seizures are unknown. We have previously shown that interfering with the function of the neuron-restrictive silencer factor (NRSF/REST), an important transcription factor that influences neuronal phenotype, attenuated development of this disorder. In this study, we found that epilepsy-provoking seizures increased the low NRSF levels in mature hippocampus several fold yet surprisingly, provoked repression of only a subset (∼10%) of potential NRSF target genes. Accordingly, the repressed gene-set was rescued when NRSF binding to chromatin was blocked. Unexpectedly, genes selectively repressed by NRSF had mid-range binding frequencies to the repressor, a property that rendered them sensitive to moderate fluctuations of NRSF levels. Genes selectively regulated by NRSF during epileptogenesis coded for ion channels, receptors, and other crucial contributors to neuronal function. Thus, dynamic, selective regulation of NRSF target genes may play a role in influencing neuronal properties in pathological and physiological contexts. DOI: http://dx.doi.org/10.7554/eLife.01267.001 PMID:25117540

  6. The human cut homeodomain protein represses transcription from the c-myc promoter.

    PubMed Central

    Dufort, D; Nepveu, A

    1994-01-01

    Studies of the c-myc promoter have shown that efficient transcription initiation at the P2 start site as well as the block to elongation of transcription require the presence of the ME1a1 protein binding site upstream of the P2 TATA box. Following fractionation by size exclusion chromatography, three protein-ME1a1 DNA complexes, a, b, and c, were detected by electrophoretic mobility shift assay. A cDNA encoding a protein present in complex c was isolated by screening of an expression library with an ME1a1 DNA probe. This cDNA was found to encode the human homolog of the Drosophila Cut homeodomain protein. The bacterially expressed human Cut (hu-Cut) protein bound to the ME1a1 site, and antibodies against hu-Cut inhibited the ME1a1 binding activity c in nuclear extracts. In cotransfection experiments, the hu-Cut protein repressed transcription from the c-myc promoter, and this repression was shown to be dependent on the presence of the ME1a1 site. Using a reporter construct with a heterologous promoter, we found that c-myc exon 1 sequences were also necessary, in addition to the ME1a1 site, for repression by Cut. Taken together, these results suggest that the human homolog of the Drosophila Cut homeodomain protein is involved in regulation of the c-myc gene. Images PMID:8196661

  7. Smad4 suppresses the tumorigenesis and aggressiveness of neuroblastoma through repressing the expression of heparanase

    PubMed Central

    Qu, Hongxia; Zheng, Liduan; Jiao, Wanju; Mei, Hong; Li, Dan; Song, Huajie; Fang, Erhu; Wang, Xiaojing; Li, Shiwang; Huang, Kai; Tong, Qiangsong

    2016-01-01

    Heparanase (HPSE) is the only endo-β-D-glucuronidase that is correlated with the progression of neuroblastoma (NB), the most common extracranial malignancy in childhood. However, the mechanisms underlying HPSE expression in NB still remain largely unknown. Herein, through analyzing cis-regulatory elements and mining public microarray datasets, we identified SMAD family member 4 (Smad4) as a crucial transcription regulator of HPSE in NB. We demonstrated that Smad4 repressed the HPSE expression at the transcriptional levels in NB cells. Mechanistically, Smad4 suppressed the HPSE expression through directly binding to its promoter and repressing the lymphoid enhancer binding factor 1 (LEF1)-facilitated transcription of HPSE via physical interaction. Gain- and loss-of-function studies demonstrated that Smad4 inhibited the growth, invasion, metastasis, and angiogenesis of NB cells in vitro and in vivo. Restoration of HPSE expression prevented the NB cells from changes in these biological features induced by Smad4. In clinical NB specimens, Smad4 was under-expressed and inversely correlated with HPSE levels, while LEF1 was highly expressed and positively correlated with HPSE expression. Patients with high Smad4 expression, low LEF1 or HPSE levels had greater survival probability. These results demonstrate that Smad4 suppresses the tumorigenesis and aggressiveness of NB through repressing the HPSE expression. PMID:27595937

  8. p27Kip1 Directly Represses Sox2 during Embryonic Stem Cell Differentiation

    PubMed Central

    Li, Han; Collado, Manuel; Villasante, Aranzazu; Matheu, Ander; Lynch, Cian J.; Cañamero, Marta; Rizzoti, Karine; Carneiro, Carmen; Martínez, Gloria; Vidal, Anxo; Lovell-Badge, Robin; Serrano, Manuel

    2012-01-01

    Summary The mechanisms responsible for the transcriptional silencing of pluripotency genes in differentiated cells are poorly understood. We have observed that cells lacking the tumor suppressor p27 can be reprogrammed into induced pluripotent stem cells (iPSCs) in the absence of ectopic Sox2. Interestingly, cells and tissues from p27 null mice, including brain, lung, and retina, present an elevated basal expression of Sox2, suggesting that p27 contributes to the repression of Sox2. Furthermore, p27 null iPSCs fail to fully repress Sox2 upon differentiation. Mechanistically, we have found that upon differentiation p27 associates to the SRR2 enhancer of the Sox2 gene together with a p130-E2F4-SIN3A repressive complex. Finally, Sox2 haploinsufficiency genetically rescues some of the phenotypes characteristic of p27 null mice, including gigantism, pituitary hyperplasia, pituitary tumors, and retinal defects. Collectively, these results demonstrate an unprecedented connection between p27 and Sox2 relevant for reprogramming and cancer and for understanding human pathologies associated with p27 germline mutations. PMID:23217425

  9. Repression of hla by rot is dependent on sae in Staphylococcus aureus.

    PubMed

    Li, Dongmei; Cheung, Ambrose

    2008-03-01

    The regulatory locus sae is a two-component system in Staphylococcus aureus that regulates many important virulence factors, including alpha-toxin (encoded by hla) at the transcriptional level. The SarA homologs Rot and SarT were previously shown to be repressors of hla in selected S. aureus backgrounds. To delineate the interaction of rot and sae and the contribution of sarT to hla expression, an assortment of rot and sae isogenic single mutants, a rot sae double mutant, and a rot sae sarT markerless triple mutant were constructed from wild-type strain COL. Using Northern blot analysis and transcriptional reporter gene green fluorescent protein, fusion, and phenotypic assays, we found that the repression of hla by rot is dependent on sae. A rot sae sarT triple mutant was not able to rescue the hla defect of the rot sae double mutant. Among the three sae promoters, the distal sae P3 promoter is the strongest in vitro. Interestingly, the sae P3 promoter activities correlate with hla expression in rot, rot sae, and rot sae sarT mutants of COL. Transcriptional study has also shown that rot repressed sae, especially at the sae P3 promoter. Collectively, our data implicated the importance of sae in the rot-mediated repression of hla in S. aureus.

  10. Smad4 suppresses the tumorigenesis and aggressiveness of neuroblastoma through repressing the expression of heparanase.

    PubMed

    Qu, Hongxia; Zheng, Liduan; Jiao, Wanju; Mei, Hong; Li, Dan; Song, Huajie; Fang, Erhu; Wang, Xiaojing; Li, Shiwang; Huang, Kai; Tong, Qiangsong

    2016-01-01

    Heparanase (HPSE) is the only endo-β-D-glucuronidase that is correlated with the progression of neuroblastoma (NB), the most common extracranial malignancy in childhood. However, the mechanisms underlying HPSE expression in NB still remain largely unknown. Herein, through analyzing cis-regulatory elements and mining public microarray datasets, we identified SMAD family member 4 (Smad4) as a crucial transcription regulator of HPSE in NB. We demonstrated that Smad4 repressed the HPSE expression at the transcriptional levels in NB cells. Mechanistically, Smad4 suppressed the HPSE expression through directly binding to its promoter and repressing the lymphoid enhancer binding factor 1 (LEF1)-facilitated transcription of HPSE via physical interaction. Gain- and loss-of-function studies demonstrated that Smad4 inhibited the growth, invasion, metastasis, and angiogenesis of NB cells in vitro and in vivo. Restoration of HPSE expression prevented the NB cells from changes in these biological features induced by Smad4. In clinical NB specimens, Smad4 was under-expressed and inversely correlated with HPSE levels, while LEF1 was highly expressed and positively correlated with HPSE expression. Patients with high Smad4 expression, low LEF1 or HPSE levels had greater survival probability. These results demonstrate that Smad4 suppresses the tumorigenesis and aggressiveness of NB through repressing the HPSE expression. PMID:27595937

  11. Identification of a phorbol ester-repressible v-src-inducible gene

    SciTech Connect

    Simmons, D.L.; Levy, D.B.; Yannoni, Y.; Erikson, R.L. )

    1989-02-01

    Chicken embryo fibroblasts (CEF) infected with a temperature-sensitive Rous sarcoma virus (RSV) mutant, tsNY72-4, express a set of pp60{sup v-src}-induced RNAs soon after shift to the permissive temperature. By subtractive and differential screening, the authors have cloned 12 of these sequences, 2 of which were c-fos and krox-24. Serum induced all the v-src-inducible genes tested, suggesting that these genes serve roles in normal cell division and are not specific to transformation per se. Significantly, however, v-src produced prolonged, and in some cases kinetically complex, patterns of induction compared to serum. For most of the clones, phorbol 12-tetradecanoate 13-acetate (TPA) induced mRNAs with kinetics similar to that of serum. However, one clone (CEF-4) was expressed in a biphasic manner. Another (CEF-10) was repressed by TPA at 1 hr, after which this mRNA was permanently induced. The pattern of repression-induction of CEF-10 mRNA is the inverse of protein kinase C (PKC) activity in the cell, suggesting that PKC actively represses this gene. In vivo expression of CEF-10 mRNA is restricted predominantly to the lung. A full-length CEF-10 cDNA encodes a 41-kDa protein that has an amino-terminal signal peptide for secretion, contains a markedly high number of cysteine residues, and shows no sequence similarity to known proteins.

  12. Repression of Igf1 expression by Ezh2 prevents basal cell differentiation in the developing lung

    PubMed Central

    Galvis, Laura A.; Holik, Aliaksei Z.; Short, Kieran M.; Pasquet, Julie; Lun, Aaron T. L.; Blewitt, Marnie E.; Smyth, Ian M.; Ritchie, Matthew E.; Asselin-Labat, Marie-Liesse

    2015-01-01

    Epigenetic mechanisms involved in the establishment of lung epithelial cell lineage identities during development are largely unknown. Here, we explored the role of the histone methyltransferase Ezh2 during lung lineage determination. Loss of Ezh2 in the lung epithelium leads to defective lung formation and perinatal mortality. We show that Ezh2 is crucial for airway lineage specification and alveolarization. Using optical projection tomography imaging, we found that branching morphogenesis is affected in Ezh2 conditional knockout mice and the remaining bronchioles are abnormal, lacking terminally differentiated secretory club cells. Remarkably, RNA-seq analysis revealed the upregulation of basal genes in Ezh2-deficient epithelium. Three-dimensional imaging for keratin 5 further showed the unexpected presence of a layer of basal cells from the proximal airways to the distal bronchioles in E16.5 embryos. ChIP-seq analysis indicated the presence of Ezh2-mediated repressive marks on the genomic loci of some but not all basal genes, suggesting an indirect mechanism of action of Ezh2. We found that loss of Ezh2 de-represses insulin-like growth factor 1 (Igf1) expression and that modulation of IGF1 signaling ex vivo in wild-type lungs could induce basal cell differentiation. Altogether, our work reveals an unexpected role for Ezh2 in controlling basal cell fate determination in the embryonic lung endoderm, mediated in part by repression of Igf1 expression. PMID:25790853

  13. Friend of GATA-1 Represses GATA-3–dependent Activity in CD4+ T Cells

    PubMed Central

    Zhou, Meixia; Ouyang, Wenjun; Gong, Qian; Katz, Samuel G.; White, J. Michael; Orkin, Stuart H.; Murphy, Kenneth M.

    2001-01-01

    The development of naive CD4+ T cells into a T helper (Th) 2 subset capable of producing interleukin (IL)-4, IL-5, and IL-13 involves a signal transducer and activator of transcription (Stat)6-dependent induction of GATA-3 expression, followed by Stat6-independent GATA-3 autoactivation. The friend of GATA (FOG)-1 protein regulates GATA transcription factor activity in several stages of hematopoietic development including erythrocyte and megakaryocyte differentiation, but whether FOG-1 regulates GATA-3 in T cells is uncertain. We show that FOG-1 can repress GATA-3–dependent activation of the IL-5 promoter in T cells. Also, FOG-1 overexpression during primary activation of naive T cells inhibited Th2 development in CD4+ T cells. FOG-1 fully repressed GATA-3–dependent Th2 development and GATA-3 autoactivation, but not Stat6-dependent induction of GATA-3. FOG-1 overexpression repressed development of Th2 cells from naive T cells, but did not reverse the phenotype of fully committed Th2 cells. Thus, FOG-1 may be one factor capable of regulating the Th2 development. PMID:11714753

  14. Quorum regulatory small RNAs repress type VI secretion in Vibrio cholerae.

    PubMed

    Shao, Yi; Bassler, Bonnie L

    2014-06-01

    Type VI secretion is critical for Vibrio cholerae to successfully combat phagocytic eukaryotes and to survive in the presence of competing bacterial species. V. cholerae type VI secretion system genes are encoded in one large and two small clusters. In V. cholerae, type VI secretion is controlled by quorum sensing, the cell-cell communication process that enables bacteria to orchestrate group behaviours. The quorum-sensing response regulator LuxO represses type VI secretion genes at low cell density and the quorum-sensing regulator HapR activates type VI secretion genes at high cell density. We demonstrate that the quorum regulatory small RNAs (Qrr sRNAs) that function between LuxO and HapR in the quorum-sensing cascade are required for these regulatory effects. The Qrr sRNAs control type VI secretion via two mechanisms: they repress expression of the large type VI secretion system cluster through base pairing and they repress HapR, the activator of the two small type VI secretion clusters. This regulatory arrangement ensures that the large cluster encoding many components of the secretory machine is expressed prior to the two small clusters that encode the secreted effectors. Qrr sRNA-dependent regulation of the type VI secretion system is conserved in pandemic and non-pandemic V. cholerae strains.

  15. Epigenetic regulation of puberty via Zinc finger protein-mediated transcriptional repression

    PubMed Central

    Lomniczi, Alejandro; Wright, Hollis; Castellano, Juan Manuel; Matagne, Valerie; Toro, Carlos A.; Ramaswamy, Suresh; Plant, Tony M.; Ojeda, Sergio R.

    2015-01-01

    In primates, puberty is unleashed by increased GnRH release from the hypothalamus following an interval of juvenile quiescence. GWAS implicates Zinc finger (ZNF) genes in timing human puberty. Here we show that hypothalamic expression of several ZNFs decreased in agonadal male monkeys in association with the pubertal reactivation of gonadotropin secretion. Expression of two of these ZNFs, GATAD1 and ZNF573, also decreases in peripubertal female monkeys. However, only GATAD1 abundance increases when gonadotropin secretion is suppressed during late infancy. Targeted delivery of GATAD1 or ZNF573 to the rat hypothalamus delays puberty by impairing the transition of a transcriptional network from an immature repressive epigenetic configuration to one of activation. GATAD1 represses transcription of two key puberty-related genes, KISS1 and TAC3, directly, and reduces the activating histone mark H3K4me2 at each promoter via recruitment of histone demethylase KDM1A. We conclude that GATAD1 epitomizes a subset of ZNFs involved in epigenetic repression of primate puberty. PMID:26671628

  16. Global control of motor neuron topography mediated by the repressive actions of a single hox gene.

    PubMed

    Jung, Heekyung; Lacombe, Julie; Mazzoni, Esteban O; Liem, Karel F; Grinstein, Jonathan; Mahony, Shaun; Mukhopadhyay, Debnath; Gifford, David K; Young, Richard A; Anderson, Kathryn V; Wichterle, Hynek; Dasen, Jeremy S

    2010-09-01

    In the developing spinal cord, regional and combinatorial activities of Hox transcription factors are critical in controlling motor neuron fates along the rostrocaudal axis, exemplified by the precise pattern of limb innervation by more than fifty Hox-dependent motor pools. The mechanisms by which motor neuron diversity is constrained to limb levels are, however, not well understood. We show that a single Hox gene, Hoxc9, has an essential role in organizing the motor system through global repressive activities. Hoxc9 is required for the generation of thoracic motor columns, and in its absence, neurons acquire the fates of limb-innervating populations. Unexpectedly, multiple Hox genes are derepressed in Hoxc9 mutants, leading to motor pool disorganization and alterations in the connections by thoracic and forelimb-level subtypes. Genome-wide analysis of Hoxc9 binding suggests that this mode of repression is mediated by direct interactions with Hox regulatory elements, independent of chromatin marks typically associated with repressed Hox genes.

  17. Acute myeloid leukemia requires Hhex to enable PRC2-mediated epigenetic repression of Cdkn2a

    PubMed Central

    Shields, Benjamin J.; Jackson, Jacob T.; Metcalf, Donald; Shi, Wei; Huang, Qiutong; Garnham, Alexandra L.; Glaser, Stefan P.; Beck, Dominik; Pimanda, John E.; Bogue, Clifford W.; Smyth, Gordon K.; Alexander, Warren S.; McCormack, Matthew P.

    2016-01-01

    Unlike clustered HOX genes, the role of nonclustered homeobox gene family members in hematopoiesis and leukemogenesis has not been extensively studied. Here we found that the hematopoietically expressed homeobox gene Hhex is overexpressed in acute myeloid leukemia (AML) and is essential for the initiation and propagation of MLL-ENL-induced AML but dispensable for normal myelopoiesis, indicating a specific requirement for Hhex for leukemic growth. Loss of Hhex leads to expression of the Cdkn2a-encoded tumor suppressors p16INK4a and p19ARF, which are required for growth arrest and myeloid differentiation following Hhex deletion. Mechanistically, we show that Hhex binds to the Cdkn2a locus and directly interacts with the Polycomb-repressive complex 2 (PRC2) to enable H3K27me3-mediated epigenetic repression. Thus, Hhex is a potential therapeutic target that is specifically required for AML stem cells to repress tumor suppressor pathways and enable continued self-renewal. PMID:26728554

  18. Blue light-mediated transcriptional activation and repression of gene expression in bacteria.

    PubMed

    Jayaraman, Premkumar; Devarajan, Kavya; Chua, Tze Kwang; Zhang, Hanzhong; Gunawan, Erry; Poh, Chueh Loo

    2016-08-19

    Light-regulated modules offer unprecedented new ways to control cellular behavior in precise spatial and temporal resolution. The availability of such tools may dramatically accelerate the progression of synthetic biology applications. Nonetheless, current optogenetic toolbox of prokaryotes has potential issues such as lack of rapid and switchable control, less portable, low dynamic expression and limited parts. To address these shortcomings, we have engineered a novel bidirectional promoter system for Escherichia coli that can be induced or repressed rapidly and reversibly using the blue light dependent DNA-binding protein EL222. We demonstrated that by modulating the dosage of light pulses or intensity we could control the level of gene expression precisely. We show that both light-inducible and repressible system can function in parallel with high spatial precision in a single cell and can be switched stably between ON- and OFF-states by repetitive pulses of blue light. In addition, the light-inducible and repressible expression kinetics were quantitatively analysed using a mathematical model. We further apply the system, for the first time, to optogenetically synchronize two receiver cells performing different logic behaviors over time using blue light as a molecular clock signal. Overall, our modular approach layers a transformative platform for next-generation light-controllable synthetic biology systems in prokaryotes.

  19. A Conserved Upstream Open Reading Frame Mediates Sucrose-Induced Repression of TranslationW⃞

    PubMed Central

    Wiese, Anika; Elzinga, Nico; Wobbes, Barry; Smeekens, Sjef

    2004-01-01

    Sugars have been shown to regulate transcription of numerous genes in plants. Sucrose controls translation of the group S basic region leucine zipper (bZIP)-type transcription factor ATB2/AtbZIP11 (Rook et al., 1998a). This control requires the unusually long 5′ untranslated region (UTR) of the gene. Point mutations and deletions of the 5′UTR have uncovered the sequences involved. A highly conserved upstream open reading frame (uORF) coding for 42 amino acids is essential for the repression mechanism. It is conserved in 5′UTRs of bZIP transcription factors from other Arabidopsis thaliana genes and many other plants. ATB2/AtbZIP11 is normally expressed in association with vascular tissues. Ectopic expression of a 5′UTR construct shows that the sucrose repression system is functional in all tissues. AtbZIP2 is another Arabidopsis bZIP transcription factor gene harboring the conserved uORF, which is regulated similarly via sucrose-induced repression of translation. This suggests a general function of the conserved uORF in sucrose-controlled regulation of expression. Our findings imply the operation of a sucrose-sensing pathway that controls translation of several plant bZIP transcription factor genes harboring the conserved uORF in their 5′UTRs. Target genes of such transcription factors will then be regulated in sucrose-dependent way. PMID:15208401

  20. The transcription factor optomotor-blind antagonizes Drosophila haltere growth by repressing decapentaplegic and hedgehog targets.

    PubMed

    Simon, Eléanor; Guerrero, Isabel

    2015-01-01

    In Drosophila, decapentaplegic, which codes for a secreted signaling molecule, is activated by the Hedgehog signaling pathway at the anteroposterior compartment border of the two dorsal primordia; the wing and the haltere imaginal discs. In the wing disc, Decapentaplegic and Hedgehog signaling targets are implicated in cell proliferation and cell survival. However, most of their known targets in the wing disc are not expressed in the haltere disc due to their repression by the Hox gene Ultrabithorax. The T-box gene optomotor-blind escapes this repression in the haltere disc, and therefore is expressed in both the haltere and wing discs. Optomotor-blind is a major player during wing development and its function has been intensely investigated in this tissue, however, its role in haltere development has not been reported so far. Here we show that Optomotor-blind function in the haltere disc differs from that in the wing disc. Unlike its role in the wing, Optomotor-blind does not prevent apoptosis in the haltere but rather limits growth by repressing several Decapentaplegic and Hedgehog targets involved both in wing proliferation and in modulating the spread of morphogens similar to Ultrabithorax function but without disturbing Ultrabithorax expression.

  1. Derepression and repression of the histidine operon: role of the feedback site of the first enzyme.

    PubMed Central

    Fernández, V M; Martíndelrío, R; Tébar, A R; Guisán, J M; Ballesteros, A O

    1975-01-01

    Thiazolealanine, a false feedback inhibitor, causes transient repression of the his operon previously derepressed by a severe histidine limitation in strains with a wild-type or feedback-hypersensitive first enzyme but not in feedback-resistant mutants. Since experiments reported here clearly demonstrate that thiazolealanine is not transferred to tRNAHis, it is proposed that this "transient repression" is effected through the interaction of thiazolealanine with the feedback site of the enzyme. Experiments in the presence of rifampin indicate that this thiazolealanine-mediated effect is exerted at the level of translation. We conclude that histidine (free), in addition to forming co-repressor, also represses the operon at the level of translation through feedback interaction with the first enzyme of the pathway (adenosine 5'-triphosphate phosphoribosyltransferase). Rates of derepression in feedback-resistant strains are roughly half of those observed in controls, suggesting a positive role played by a first enzyme with a normal but unoccupied feedback site. Some feedback-resistant mutants, in contrast to the wild type, were unable to exhibit derepression under histidine limitation caused by aminotriazole. PMID:1104584

  2. Distinct repressive properties of the mammalian and fish orphan nuclear receptors SHP and DAX-1.

    PubMed

    Park, Yun-Yong; Teyssier, Catherine; Vanacker, Jean-Marc; Choi, Hueng-Sik

    2007-06-30

    It has been suggested that the structure and function of nuclear receptors are evolutionally conserved. Here, we compare the molecular functions of the nile tilapia (Oreochromis niloticus) small heterodimer partner (nSHP/NR0B2) and the Dosage-sensitive sex reversal AHC critical region on X chromosome gene 1 (nDAX-1/NR0B1) with those of human SHP and DAX-1 (hSHP and hDAX-1, respectively). We found that, upon transient cotransfection of human cells, nDAX-1 repressed the activity of tilapia SF-1 (nSF-1) but not that of human SF-1, although the physical interaction with human SF-1 was retained. Similarly, nSHP repressed the activity of nSF-1, whereas hSHP did not, pointing to divergent evolution of SHP/SF-1 in fish and human. We thus propose that the repressive functions of SHP and DAX-1 have been conserved in fish and mammals although with different transcriptional targets and mechanisms. These differences provide new insights into the physiological diversification of atypical orphan nuclear receptors during vertebrate evolution. PMID:17646707

  3. Not4-dependent translational repression is important for cellular protein homeostasis in yeast

    PubMed Central

    Preissler, Steffen; Reuther, Julia; Koch, Miriam; Scior, Annika; Bruderek, Michael; Frickey, Tancred; Deuerling, Elke

    2015-01-01

    Translation of aberrant or problematic mRNAs can cause ribosome stalling which leads to the production of truncated or defective proteins. Therefore, cells evolved cotranslational quality control mechanisms that eliminate these transcripts and target arrested nascent polypeptides for proteasomal degradation. Here we show that Not4, which is part of the multifunctional Ccr4–Not complex in yeast, associates with polysomes and contributes to the negative regulation of protein synthesis. Not4 is involved in translational repression of transcripts that cause transient ribosome stalling. The absence of Not4 affected global translational repression upon nutrient withdrawal, enhanced the expression of arrested nascent polypeptides and caused constitutive protein folding stress and aggregation. Similar defects were observed in cells with impaired mRNA decapping protein function and in cells lacking the mRNA decapping activator and translational repressor Dhh1. The results suggest a role for Not4 together with components of the decapping machinery in the regulation of protein expression on the mRNA level and emphasize the importance of translational repression for the maintenance of proteome integrity. PMID:25971775

  4. Structural insights into gene repression by the orphan nuclear receptor SHP

    PubMed Central

    Zhi, Xiaoyong; Zhou, X. Edward; He, Yuanzheng; Zechner, Christoph; Suino-Powell, Kelly M.; Kliewer, Steven A.; Melcher, Karsten; Mangelsdorf, David J.; Xu, H. Eric

    2014-01-01

    Small heterodimer partner (SHP) is an orphan nuclear receptor that functions as a transcriptional repressor to regulate bile acid and cholesterol homeostasis. Although the precise mechanism whereby SHP represses transcription is not known, E1A-like inhibitor of differentiation (EID1) was isolated as a SHP-interacting protein and implicated in SHP repression. Here we present the crystal structure of SHP in complex with EID1, which reveals an unexpected EID1-binding site on SHP. Unlike the classical cofactor-binding site near the C-terminal helix H12, the EID1-binding site is located at the N terminus of the receptor, where EID1 mimics helix H1 of the nuclear receptor ligand-binding domain. The residues composing the SHP–EID1 interface are highly conserved. Their mutation diminishes SHP–EID1 interactions and affects SHP repressor activity. Together, these results provide important structural insights into SHP cofactor recruitment and repressor function and reveal a conserved protein interface that is likely to have broad implications for transcriptional repression by orphan nuclear receptors. PMID:24379397

  5. Wingless blocks bristle formation and morphogenetic furrow progression in the eye through repression of Daughterless.

    PubMed

    Cadigan, Kenneth M; Jou, Austin D; Nusse, Roel

    2002-07-01

    In the developing eye, wingless activity represses proneural gene expression (and thus interommatidial bristle formation) and positions the morphogenetic furrow by blocking its initiation in the dorsal and ventral regions of the presumptive eye. We provide evidence that wingless mediates both effects, at least in part, through repression of the basic helix-loop-helix protein Daughterless. daughterless is required for high proneural gene expression and furrow progression. Ectopic expression of wingless blocks Daughterless expression in the proneural clusters. This repression, and that of furrow progression, can be mimicked by an activated form of armadillo and blocked by a dominant negative form of pangolin/TCF. Placing daughterless under the control of a heterologous promoter blocks the ability of ectopic wingless to inhibit bristle formation and furrow progression. hedgehog and decapentapleigic could not rescue the wingless furrow progression block, indicating that wingless acts downstream of these genes. In contrast, Atonal and Scute, which are thought to heterodimerize with Daughterless to promote furrow progression and bristle formation, respectively, can block ectopic wingless action. These results are summarized in a model where daughterless is a major, but probably not the only, target of wingless action in the eye. PMID:12091309

  6. Inhibition of tumor cell growth by Sigma1 ligand mediated translational repression

    SciTech Connect

    Kim, Felix J.; Schrock, Joel M.; Spino, Christina M.; Marino, Jacqueline C.; Pasternak, Gavril W.

    2012-09-21

    Highlights: Black-Right-Pointing-Pointer Sigma1 ligand treatment mediates decrease in tumor cell mass. Black-Right-Pointing-Pointer Identification of a Sigma1 ligand with reversible translational repressor actions. Black-Right-Pointing-Pointer Demonstration of a role for Sigma1 in cellular protein synthesis. -- Abstract: Treatment with sigma1 receptor (Sigma1) ligands can inhibit cell proliferation in vitro and tumor growth in vivo. However, the cellular pathways engaged in response to Sigma1 ligand treatment that contribute to these outcomes remain largely undefined. Here, we show that treatment with putative antagonists of Sigma1 decreases cell mass. This effect corresponds with repressed cap-dependent translation initiation in multiple breast and prostate cancer cell lines. Sigma1 antagonist treatment suppresses phosphorylation of translational regulator proteins p70S6K, S6, and 4E-BP1. RNAi-mediated knockdown of Sigma1 also results in translational repression, consistent with the effects of antagonist treatment. Sigma1 antagonist mediated translational repression and decreased cell size are both reversible. Together, these data reveal a role for Sigma1 in tumor cell protein synthesis, and demonstrate that small molecule Sigma1 ligands can be used as modulators of protein translation.

  7. Progranulin (granulin/epithelin precursor) and its constituent granulin repeats repress transcription from cellular promoters

    PubMed Central

    Hoque, Mainul; Mathews, Michael B.; Pe’ery, Tsafi

    2010-01-01

    Progranulin (also known as granulin/epithelin precursor, GEP) is composed of seven granulin/epithelin repeats (granulins) and functions both as a full-length protein and as individual granulins. It is a secretory protein but a substantial amount of GEP is found inside cells, some in complexes with positive transcription elongation factor b (P-TEFb). GEP and certain granulins interact with the cyclin T1 subunit of P-TEFb, and with its HIV-1 Tat co-factor, leading to repression of transcription from the HIV promoter. We show that GEP lacking the signal peptide (GEPspm) remains inside cells and, like wild-type GEP, interacts with cyclin T1 and Tat. GEPspm represses transcription from the HIV-1 promoter at the RNA level. Granulins that bind cyclin T1 are phosphorylated by P-TEFb in vivo and in vitro on serine residues. GEPspm and those granulins that interact with cyclin T1 also inhibit transcription from cellular cad and c-myc promoters, which are highly dependent on P-TEFb, but not from the PCNA promoter. In addition, GEPspm and granulins repress transcriptional activation by VP16 or c-Myc, proteins that bind and recruit P-TEFb to responsive promoters. These data suggest that intracellular GEP is a promoter-specific transcriptional repressor that modulates the function of cellular and viral transcription factors. PMID:20054825

  8. MAZR and Runx Factors Synergistically Repress ThPOK during CD8+ T Cell Lineage Development.

    PubMed

    Sakaguchi, Shinya; Hainberger, Daniela; Tizian, Caroline; Tanaka, Hirokazu; Okuda, Tsukasa; Taniuchi, Ichiro; Ellmeier, Wilfried

    2015-09-15

    Th-inducing Pox virus and zinc finger/Krüppel-like factor (ThPOK) is a key commitment factor for CD4(+) lineage T cells and is essential for the maintenance of CD4 lineage integrity; thus, the expression of ThPOK has to be tightly controlled. In this article, we demonstrate that Myc-associated zinc finger-related factor (MAZR) and Runt-related transcription factor 1 (Runx1) together repressed ThPOK in preselection double-positive thymocytes, whereas MAZR acted in synergy with Runx3 in the repression of ThPOK in CD8(+) T cells. Furthermore, MAZR-Runx1 and MAZR-Runx3 double-mutant mice showed enhanced derepression of Cd4 in double-negative thymocytes and in CD8(+) T cells in comparison with Runx1 or Runx3 single-deficient mice, respectively, indicating that MAZR modulates Cd4 silencing. Thus, our data demonstrate developmental stage-specific synergistic activities between MAZR and Runx/core-binding factor β (CBFβ) complexes. Finally, retroviral Cre-mediated conditional deletion of MAZR in peripheral CD8(+) T cells led to the derepression of ThPOK, thus showing that MAZR is also part of the molecular machinery that maintains a repressed state of ThPOK in CD8(+) T cells. PMID:26254341

  9. The Q System: A Repressible Binary System for Transgene Expression, Lineage Tracing and Mosaic Analysis

    PubMed Central

    Potter, Christopher J.; Tasic, Bosiljka; Russler, Emilie V.; Liang, Liang; Luo, Liqun

    2010-01-01

    Summary We describe a new repressible binary expression system based on the regulatory genes from the Neurospora qa gene cluster. This ‘Q system’ offers attractive features for transgene expression in Drosophila and mammalian cells: low basal expression in the absence of the transcriptional activator QF, high QF-induced expression, and QF repression by its repressor QS. Additionally, feeding flies quinic acid can relieve QS repression. The Q system offers many applications including: 1) intersectional ‘logic gates’ with the GAL4 system for manipulating transgene expression patterns, 2) GAL4-independent MARCM analysis, 3) coupled MARCM analysis to independently visualize and genetically manipulate siblings from any cell division. We demonstrate the utility of the Q system in determining cell division patterns of a neuronal lineage and gene function in cell growth and proliferation, and in dissecting neurons responsible for olfactory attraction. The Q system can be expanded to other uses in Drosophila, and to any organism conducive to transgenesis. PMID:20434990

  10. Repression of early lateral root initiation events by transient water deficit in barley and maize.

    PubMed

    Babé, Aurélie; Lavigne, Tristan; Séverin, Jean-Philippe; Nagel, Kerstin A; Walter, Achim; Chaumont, François; Batoko, Henri; Beeckman, Tom; Draye, Xavier

    2012-06-01

    The formation of lateral roots (LRs) is a key driver of root system architecture and developmental plasticity. The first stage of LR formation, which leads to the acquisition of founder cell identity in the pericycle, is the primary determinant of root branching patterns. The fact that initiation events occur asynchronously in a very small number of cells inside the parent root has been a major difficulty in the study of the molecular regulation of branching patterns. Inducible systems that trigger synchronous lateral formation at predictable sites have proven extremely valuable in Arabidopsis to decipher the first steps of LR formation. Here, we present a LR repression system for cereals that relies on a transient water-deficit treatment, which blocks LR initiation before the first formative divisions. Using a time-lapse approach, we analysed the dynamics of this repression along growing roots and were able to show that it targets a very narrow developmental window of the initiation process. Interestingly, the repression can be exploited to obtain negative control root samples where LR initiation is absent. This system could be instrumental in the analysis of the molecular basis of drought-responsive as well as intrinsic pathways of LR formation in cereals. PMID:22527396

  11. Inhibition of interleukin-1β-mediated interleukin-1 receptor-associated kinase 4 phosphorylation by zinc leads to repression of memory T helper type 17 response in humans.

    PubMed

    Lee, Hyunju; Kim, Bonah; Choi, Yeon Ho; Hwang, Yuri; Kim, Dong Hyun; Cho, Sunjung; Hong, Sung Jun; Lee, Won-Woo

    2015-12-01

    Zinc is an essential trace element that plays pivotal roles in multiple facets of the immune system. Besides its catalytic and structural roles, zinc also functions as an intracellular signalling molecule, and changes in zinc levels can cause both direct and indirect modulation of immune responses. Further, cytoplasmic levels of bioavailable zinc in immune cells are largely influenced by many extracellular stimuli. Here we provide evidence that zinc represses memory T helper type 17 responses in humans by inhibiting interleukin-1β (IL-1β)-mediated signal. In vitro zinc treatment of CD4(+) T cells in the presence of activated monocytes inhibited interferon-γ-producing cells and IL-17-producing cells, but not IL-4-producing cells. Of note, production of IL-17(+) cells from memory CD4(+) T cells, which is significantly up-regulated by lipopolysaccharide-stimulated monocytes, was preferentially repressed by zinc. Increased cytoplasmic zinc in T cells suppressed IL-1β signalling through repression of phosphorylation of IL-1 receptor-associated kinase 4 (IRAK4), so leading to an inhibitory effect on T helper type 17 responses facilitated by monocyte-derived IL-1β in humans. These findings suggest that extracellular zinc bioavailability may affect memory CD4(+) T-cell responses by modulating the zinc-mediated signalling pathway.

  12. Sp1 mediates repression of the resistin gene by PPAR{gamma} agonists in 3T3-L1 adipocytes

    SciTech Connect

    Chung, S.S.; Choi, H.H.; Cho, Y.M.; Lee, H.K.; Park, K.S. . E-mail: kspark@snu.ac.kr

    2006-09-15

    Resistin is an adipokine related to obesity and insulin resistance. Expression of the resistin gene is repressed by the treatment of peroxisome proliferator-activated receptor {gamma} (PPAR{gamma}) agonists, thiazolidinediones (TZDs). In this study, we investigated the mechanism by which TZDs inhibit the resistin gene expression. Resistin gene expression was decreased by TZD in fully differentiated 3T3-L1 adipocytes, which was abolished after treatment of cycloheximide (a protein synthesis inhibitor). TZD could not repress the expression of the resistin gene in the presence of mithramycin A (an Sp1 binding inhibitor). Sp1 binding site of the resistin promoter (-122/-114 bp) was necessary for the repression. Further investigation of the effect of TZDs on the modification of Sp1 showed that the level of O-glycosylation of Sp1 was decreased in this process. These results suggest that PPAR{gamma} activation represses the expression of the resistin gene by modulating Sp1 activity.

  13. Antileishmanial lead structures from nature: analysis of structure-activity relationships of a compound library derived from caffeic Acid bornyl ester.

    PubMed

    Glaser, Jan; Schultheis, Martina; Hazra, Sudipta; Hazra, Banasri; Moll, Heidrun; Schurigt, Uta; Holzgrabe, Ulrike

    2014-01-01

    Bioassay-guided fractionation of a chloroform extract of Valeriana wallichii (V. wallichii) rhizomes lead to the isolation and identification of caffeic acid bornyl ester (1) as the active component against Leishmania major (L. major) promastigotes (IC50 = 48.8 µM). To investigate the structure-activity relationship (SAR), a library of compounds based on 1 was synthesized and tested in vitro against L. major and L. donovani promastigotes, and L. major amastigotes. Cytotoxicity was determined using a murine J774.1 cell line and bone marrow derived macrophages (BMDM). Some compounds showed antileishmanial activity in the concentration range of pentamidine and miltefosine which are the standard drugs in use. In the L. major amastigote assay compounds 15, 19 and 20 showed good activity with relatively low cytotoxicity against BMDM, resulting in acceptable selectivity indices. Molecules with adjacent phenolic hydroxyl groups exhibited elevated cytotoxicity against murine cell lines J774.1 and BMDM. The Michael system seems not to be essential for antileishmanial activity. Based on the results compound 27 can be regarded as new lead structure for further structure optimization. PMID:24473204

  14. The use of phenylmethylsulfonyl fluoride in the study of catabolite inactivation and repression in intact cells of Saccharomyces cervisiae.

    PubMed

    Grossmann, M K

    1980-02-01

    Catabolite inactivation of fructose-1,6-bisphosphatase, isocitrate lyase, phosphoenolpruvate carboxykinase and malate dehydrogenase in intact cells could be prevented by phenylmethylsulfonyl fluoride added 40 min prior to the addition of glucose. Protein synthesis, fermentative and respiratory activity and catabolite repression were not affected. Elimination of catabolite inactivation by the addition of PMSF revealed that catabolite repression started at different times for different enzyme. PMID:6245626

  15. Mir-29 repression in bladder outlet obstruction contributes to matrix remodeling and altered stiffness.

    PubMed

    Ekman, Mari; Bhattachariya, Anirban; Dahan, Diana; Uvelius, Bengt; Albinsson, Sebastian; Swärd, Karl

    2013-01-01

    Recent work has uncovered a role of the microRNA (miRNA) miR-29 in remodeling of the extracellular matrix. Partial bladder outlet obstruction is a prevalent condition in older men with prostate enlargement that leads to matrix synthesis in the lower urinary tract and increases bladder stiffness. Here we tested the hypothesis that miR-29 is repressed in the bladder in outlet obstruction and that this has an impact on protein synthesis and matrix remodeling leading to increased bladder stiffness. c-Myc, NF-κB and SMAD3, all of which repress miR-29, were activated in the rat detrusor following partial bladder outlet obstruction but at different times. c-Myc and NF-κB activation occurred early after obstruction, and SMAD3 phosphorylation increased later, with a significant elevation at 6 weeks. c-Myc, NF-κB and SMAD3 activation, respectively, correlated with repression of miR-29b and miR-29c at 10 days of obstruction and with repression of miR-29c at 6 weeks. An mRNA microarray analysis showed that the reduction of miR-29 following outlet obstruction was associated with increased levels of miR-29 target mRNAs, including mRNAs for tropoelastin, the matricellular protein Sparc and collagen IV. Outlet obstruction increased protein levels of eight out of eight examined miR-29 targets, including tropoelastin and Sparc. Transfection of human bladder smooth muscle cells with antimiR-29c and miR-29c mimic caused reciprocal changes in target protein levels in vitro. Tamoxifen inducible and smooth muscle-specific deletion of Dicer in mice reduced miR-29 expression and increased tropoelastin and the thickness of the basal lamina surrounding smooth muscle cells in the bladder. It also increased detrusor stiffness independent of outlet obstruction. Taken together, our study supports a model where the combined repressive influences of c-Myc, NF-κB and SMAD3 reduce miR-29 in bladder outlet obstruction, and where the resulting drop in miR-29 contributes to matrix remodeling and

  16. Mir-29 Repression in Bladder Outlet Obstruction Contributes to Matrix Remodeling and Altered Stiffness

    PubMed Central

    Ekman, Mari; Bhattachariya, Anirban; Dahan, Diana; Uvelius, Bengt; Albinsson, Sebastian; Swärd, Karl

    2013-01-01

    Recent work has uncovered a role of the microRNA (miRNA) miR-29 in remodeling of the extracellular matrix. Partial bladder outlet obstruction is a prevalent condition in older men with prostate enlargement that leads to matrix synthesis in the lower urinary tract and increases bladder stiffness. Here we tested the hypothesis that miR-29 is repressed in the bladder in outlet obstruction and that this has an impact on protein synthesis and matrix remodeling leading to increased bladder stiffness. c-Myc, NF-κB and SMAD3, all of which repress miR-29, were activated in the rat detrusor following partial bladder outlet obstruction but at different times. c-Myc and NF-κB activation occurred early after obstruction, and SMAD3 phosphorylation increased later, with a significant elevation at 6 weeks. c-Myc, NF-κB and SMAD3 activation, respectively, correlated with repression of miR-29b and miR-29c at 10 days of obstruction and with repression of miR-29c at 6 weeks. An mRNA microarray analysis showed that the reduction of miR-29 following outlet obstruction was associated with increased levels of miR-29 target mRNAs, including mRNAs for tropoelastin, the matricellular protein Sparc and collagen IV. Outlet obstruction increased protein levels of eight out of eight examined miR-29 targets, including tropoelastin and Sparc. Transfection of human bladder smooth muscle cells with antimiR-29c and miR-29c mimic caused reciprocal changes in target protein levels in vitro. Tamoxifen inducible and smooth muscle-specific deletion of Dicer in mice reduced miR-29 expression and increased tropoelastin and the thickness of the basal lamina surrounding smooth muscle cells in the bladder. It also increased detrusor stiffness independent of outlet obstruction. Taken together, our study supports a model where the combined repressive influences of c-Myc, NF-κB and SMAD3 reduce miR-29 in bladder outlet obstruction, and where the resulting drop in miR-29 contributes to matrix remodeling and

  17. Activation and repression functions of an SR splicing regulator depend on exonic versus intronic-binding position.

    PubMed

    Shen, Manli; Mattox, William

    2012-01-01

    SR proteins and related factors play widespread roles in alternative pre-mRNA splicing and are known to promote splice site recognition through their Arg-Ser-rich effector domains. However, binding of SR regulators to some targets results in repression of splice sites through a distinct mechanism. Here, we investigate how activated and repressed targets of the Drosophila SR regulator Transformer2 elicit its differing effects on splicing. We find that, like activation, repression affects early steps in the recognition of splice sites and spliceosome assembly. Repositioning of regulatory elements reveals that Tra2 complexes that normally repress splicing from intronic positions activate splicing when located in an exon. Protein tethering experiments demonstrate that this position dependence is an intrinsic property of Tra2 and further show that repression and activation are mediated by separate effector domains of this protein. When other Drosophila SR factors (SF2 and Rbp1) that activate splicing from exonic positions were tethered intronically they failed to either activate or repress splicing. Interestingly, both activities of Tra2 favor the exonic identity of the RNA sequences that encompass its binding sites. This suggests a model in which these two opposite functions act in concert to define both the position and extent of alternatively spliced exons.

  18. Gene Repression in Haloarchaea Using the CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)-Cas I-B System*

    PubMed Central

    Stachler, Aris-Edda; Marchfelder, Anita

    2016-01-01

    The clustered regularly interspaced short palindromic repeats (CRISPR)-Cas system is used by bacteria and archaea to fend off foreign genetic elements. Since its discovery it has been developed into numerous applications like genome editing and regulation of transcription in eukaryotes and bacteria. For archaea currently no tools for transcriptional repression exist. Because molecular biology analyses in archaea become more and more widespread such a tool is vital for investigating the biological function of essential genes in archaea. Here we use the model archaeon Haloferax volcanii to demonstrate that its endogenous CRISPR-Cas system I-B can be harnessed to repress gene expression in archaea. Deletion of cas3 and cas6b genes results in efficient repression of transcription. crRNAs targeting the promoter region reduced transcript levels down to 8%. crRNAs targeting the reading frame have only slight impact on transcription. crRNAs that target the coding strand repress expression only down to 88%, whereas crRNAs targeting the template strand repress expression down to 8%. Repression of an essential gene results in reduction of transcription levels down to 22%. Targeting efficiencies can be enhanced by expressing a catalytically inactive Cas3 mutant. Genes can be targeted on plasmids or on the chromosome, they can be monocistronic or part of a polycistronic operon. PMID:27226589

  19. Gene Repression in Haloarchaea Using the CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)-Cas I-B System.

    PubMed

    Stachler, Aris-Edda; Marchfelder, Anita

    2016-07-15

    The clustered regularly interspaced short palindromic repeats (CRISPR)-Cas system is used by bacteria and archaea to fend off foreign genetic elements. Since its discovery it has been developed into numerous applications like genome editing and regulation of transcription in eukaryotes and bacteria. For archaea currently no tools for transcriptional repression exist. Because molecular biology analyses in archaea become more and more widespread such a tool is vital for investigating the biological function of essential genes in archaea. Here we use the model archaeon Haloferax volcanii to demonstrate that its endogenous CRISPR-Cas system I-B can be harnessed to repress gene expression in archaea. Deletion of cas3 and cas6b genes results in efficient repression of transcription. crRNAs targeting the promoter region reduced transcript levels down to 8%. crRNAs targeting the reading frame have only slight impact on transcription. crRNAs that target the coding strand repress expression only down to 88%, whereas crRNAs targeting the template strand repress expression down to 8%. Repression of an essential gene results in reduction of transcription levels down to 22%. Targeting efficiencies can be enhanced by expressing a catalytically inactive Cas3 mutant. Genes can be targeted on plasmids or on the chromosome, they can be monocistronic or part of a polycistronic operon.

  20. Derivative chameleons

    NASA Astrophysics Data System (ADS)

    Noller, Johannes

    2012-07-01

    We consider generalized chameleon models where the conformal coupling between matter and gravitational geometries is not only a function of the chameleon field phi, but also of its derivatives via higher order co-ordinate invariants (such as ∂μphi∂μphi,squphi,...). Specifically we consider the first such non-trivial conformal factor A(phi,∂μphi∂μphi). The associated phenomenology is investigated and we show that such theories have a new generic mass-altering mechanism, potentially assisting the generation of a sufficiently large chameleon mass in dense environments. The most general effective potential is derived for such derivative chameleon setups and explicit examples are given. Interestingly this points us to the existence of a purely derivative chameleon protected by a shift symmetry for phi → phi+c. We also discuss potential ghost-like instabilities associated with mass-lifting mechanisms and find another, mass-lowering and instability-free, branch of solutions. This suggests that, barring fine-tuning, stable derivative models are in fact typically anti-chameleons that suppress the field's mass in dense environments. Furthermore we investigate modifications to the thin-shell regime and prove a no-go theorem for chameleon effects in non-conformal geometries of the disformal type.

  1. Derivative chameleons

    SciTech Connect

    Noller, Johannes

    2012-07-01

    We consider generalized chameleon models where the conformal coupling between matter and gravitational geometries is not only a function of the chameleon field φ, but also of its derivatives via higher order co-ordinate invariants (such as ∂{sub μ}φ∂{sup μ}φ,□φ,...). Specifically we consider the first such non-trivial conformal factor A(φ,∂{sub μ}φ∂{sup μ}φ). The associated phenomenology is investigated and we show that such theories have a new generic mass-altering mechanism, potentially assisting the generation of a sufficiently large chameleon mass in dense environments. The most general effective potential is derived for such derivative chameleon setups and explicit examples are given. Interestingly this points us to the existence of a purely derivative chameleon protected by a shift symmetry for φ → φ+c. We also discuss potential ghost-like instabilities associated with mass-lifting mechanisms and find another, mass-lowering and instability-free, branch of solutions. This suggests that, barring fine-tuning, stable derivative models are in fact typically anti-chameleons that suppress the field's mass in dense environments. Furthermore we investigate modifications to the thin-shell regime and prove a no-go theorem for chameleon effects in non-conformal geometries of the disformal type.

  2. Repression of both isoforms of disproportionating enzyme leads to higher malto-oligosaccharide content and reduced growth in potato.

    PubMed

    Lütken, Henrik; Lloyd, James R; Glaring, Mikkel A; Baunsgaard, Lone; Laursen, Kristian Holst; Haldrup, Anna; Kossmann, Jens; Blennow, Andreas

    2010-10-01

    Two glucanotransferases, disproportionating enzyme 1 (StDPE1) and disproportionating enzyme 2 (StDPE2), were repressed using RNA interference technology in potato, leading to plants repressed in either isoform individually, or both simultaneously. This is the first detailed report of their combined repression. Plants lacking StDPE1 accumulated slightly more starch in their leaves than control plants and high levels of maltotriose, while those lacking StDPE2 contained maltose and large amounts of starch. Plants repressed in both isoforms accumulated similar amounts of starch to those lacking StDPE2. In addition, they contained a range of malto-oligosaccharides from maltose to maltoheptaose. Plants repressed in both isoforms had chlorotic leaves and did not grow as well as either the controls or lines where only one of the isoforms was repressed. Examination of photosynthetic parameters suggested that this was most likely due to a decrease in carbon assimilation. The subcellular localisation of StDPE2 was re-addressed in parallel with DPE2 from Arabidopsis thaliana by transient expression of yellow fluorescent protein fusions in tobacco. No translocation to the chloroplasts was observed for any of the fusion proteins, supporting a cytosolic role of the StDPE2 enzyme in leaf starch metabolism, as has been observed for Arabidopsis DPE2. It is concluded that StDPE1 and StDPE2 have individual essential roles in starch metabolism in potato and consequently repression of these disables regulation of leaf malto-oligosaccharides, starch content and photosynthetic activity and thereby plant growth possibly by a negative feedback mechanism.

  3. P Element Regulatory Products Enhance Zeste(1) Repression of a P[white(duplicated)] Transgene in Drosophila Melanogaster

    PubMed Central

    Coen, D.

    1990-01-01

    Drosophila P element mobilization is subject to a complex array of regulatory mechanisms. A fruitful approach to study them is the use of insertion mutations whose expression is influenced by P regulation. In the present report, it is shown that P element somatic products may influence the expression of an unrelated gene inserted in a P transposon. The P[w(d1)9.3]19DE transgene carries an in vitro modified white gene harboring a duplication of the 5' regulatory sequences. Expression of this transgene is repressed in a P background. No maternal effect is detected and repression can be relieved as soon as P chromosomes are replaced by M ones. The amplitude of repression is correlated to the P transposase activity of the individuals examined. Repression appears to be exerted by somatic products of complete autonomous P elements or of in vitro modified P elements lacking the capacity to express the fourth P exon. The P repression of P[w(d1)9.3]19DE is strongly dependent on the insertion site of this transgene. This P repression effect occurs only in the presence of the zeste(1) allele and is suppressed by Su(z)2 mutations. No qualitative differences of transcription pattern are observed between white(+) and P[w(d1)9.3]19DE in any backgrounds. P repression acts to reduce the amount of the major white transcript. This suggests that P regulatory products may act through cis-interactions at a distance of over 3 kb. PMID:1963871

  4. The Drosophila eve insulator Homie promotes eve expression and protects the adjacent gene from repression by polycomb spreading.

    PubMed

    Fujioka, Miki; Sun, Guizhi; Jaynes, James B

    2013-10-01

    Insulators can block the action of enhancers on promoters and the spreading of repressive chromatin, as well as facilitating specific enhancer-promoter interactions. However, recent studies have called into question whether the activities ascribed to insulators in model transgene assays actually reflect their functions in the genome. The Drosophila even skipped (eve) gene is a Polycomb (Pc) domain with a Pc-group response element (PRE) at one end, flanked by an insulator, an arrangement also seen in other genes. Here, we show that this insulator has three major functions. It blocks the spreading of the eve Pc domain, preventing repression of the adjacent gene, TER94. It prevents activation of TER94 by eve regulatory DNA. It also facilitates normal eve expression. When Homie is deleted in the context of a large transgene that mimics both eve and TER94 regulation, TER94 is repressed. This repression depends on the eve PRE. Ubiquitous TER94 expression is "replaced" by expression in an eve pattern when Homie is deleted, and this effect is reversed when the PRE is also removed. Repression of TER94 is attributable to spreading of the eve Pc domain into the TER94 locus, accompanied by an increase in histone H3 trimethylation at lysine 27. Other PREs can functionally replace the eve PRE, and other insulators can block PRE-dependent repression in this context. The full activity of the eve promoter is also dependent on Homie, and other insulators can promote normal eve enhancer-promoter communication. Our data suggest that this is not due to preventing promoter competition, but is likely the result of the insulator organizing a chromosomal conformation favorable to normal enhancer-promoter interactions. Thus, insulator activities in a native context include enhancer blocking and enhancer-promoter facilitation, as well as preventing the spread of repressive chromatin.

  5. Bile Acids Function Synergistically To Repress Invasion Gene Expression in Salmonella by Destabilizing the Invasion Regulator HilD.

    PubMed

    Eade, Colleen R; Hung, Chien-Che; Bullard, Brian; Gonzalez-Escobedo, Geoffrey; Gunn, John S; Altier, Craig

    2016-08-01

    Salmonella spp. are carried by and can acutely infect agricultural animals and humans. After ingestion, salmonellae traverse the upper digestive tract and initiate tissue invasion of the distal ileum, a virulence process carried out by the type III secretion system encoded within Salmonella pathogenicity island 1 (SPI-1). Salmonellae coordinate SPI-1 expression with anatomical location via environmental cues, one of which is bile, a complex digestive fluid that causes potent repression of SPI-1 genes. The individual components of bile responsible for SPI-1 repression have not been previously characterized, nor have the bacterial signaling processes that modulate their effects been determined. Here, we characterize the mechanism by which bile represses SPI-1 expression. Individual bile acids exhibit repressive activity on SPI-1-regulated genes that requires neither passive diffusion nor OmpF-mediated entry. By using genetic methods, the effects of bile and bile acids were shown to require the invasion gene transcriptional activator hilD and to function independently of known upstream signaling pathways. Protein analysis techniques showed that SPI-1 repression by bile acids is mediated by posttranslational destabilization of HilD. Finally, we found that bile acids function synergistically to achieve the overall repressive activity of bile. These studies demonstrate a common mechanism by which diverse environmental cues (e.g., certain short-chain fatty acids and bile acids) inhibit SPI-1 expression. These data provide information relevant to Salmonella pathogenesis during acute infection in the intestine and during chronic infection of the gallbladder and inform the basis for development of therapeutics to inhibit invasion as a means of repressing Salmonella pathogenicity.

  6. Complex derivatives

    NASA Astrophysics Data System (ADS)

    Battiston, Stefano; Caldarelli, Guido; Georg, Co-Pierre; May, Robert; Stiglitz, Joseph

    2013-03-01

    The intrinsic complexity of the financial derivatives market has emerged as both an incentive to engage in it, and a key source of its inherent instability. Regulators now faced with the challenge of taming this beast may find inspiration in the budding science of complex systems.

  7. Cyclic AMP levels during induction and repression of cellulase biosynthesis in Thermomonospora curvata

    SciTech Connect

    Wood, W.E.; Neubauer, D.G.; Stutzenberger, F.J.

    1984-12-01

    Specific cellulase production rates (SCPR) were compared with intracellular cyclic AMP (cAMP) levels in the thermophilic actinomycete, Thermomonospora curvata, during growth on several carbon sources in a chemically defined medium. SCPR and cAMP levels were 0.03 U (endoglucanase (EG) units) and 2 pmol per mg of dry cells, respectively, during exponential growth on glucose. These values increased to about 6 and 25, respectively, during growth on cellulose. Detectable EG production ceased when cAMP levels dropped below 10. Cellobiose (usually considered to be a cellulase inducer) caused a sharp decrease in cAMP levels and repressed EG production when added to cellulose-grown cultures. 2-deoxy-D-glucose, although nometabolizable in T. curvata, depressed cAMP to levels observed with glucose, but unlike glucose, the 2DG effect persisted until cells were washed and transferred to fresh medium. SCPR values and cAMP levels in cells grown in continuous culture under conditions of cellobiose limitation were markedly influenced by dilution rate (D). The maxima for both occurred at D = 0.085 (culture generation time of 11.8 h). When D was held constant and cellobiose concentration was increased over a 14-fold range to support higher steady state population levels, SCPR values decreased about fivefold, indicating that extracellular catabolite accumulation may be a factor in EG repression. The role of cAMP in the mechanism of this repression appears to be neither simple nor direct, since large changes (up to 200-fold) in SCPR accompany relatively small changes (10-fold) in cellular cAMP levels.

  8. Characterization of Escherichia coli Flagellar Mutants That are Insensitive to Catabolite Repression

    PubMed Central

    Silverman, Michael; Simon, Melvin

    1974-01-01

    In Escherichia coli, the synthesis of the flagellar organelle is sensitive to catabolite repression. Synthesis requires the presence of the cyclic adenosine monophosphate receptor protein (Crp) and 3′,5′-cyclic adenosine monophosphate (cAMP); i.e., mutants that lack Crp or adenylcyclase (Cya) synthesize no flagella. We isolated and characterized a series of mutants (cfs) that restored flagella-forming ability in a Crp strain of E. coli. The mutations in these strains were transferred onto episomes and they were then introduced into a variety of other strains. The presence of the mutation resulted in flagella synthesis in Cya and Crp strains as well as in the wild type grown under conditions of catabolite repression. Deletion analysis and other genetic studies indicated that: (i) the cfs mutations had a dominant effect when they were in the transconfiguration in merodiploids: (ii) they occurred in or very close to the flaI gene: and (iii) their expression required the presence of an intact flaI gene adjacent to the cfs mutation. Biochemical studies showed that the synthesis of at least two flagellar polypeptides, the hook subunit and an amber fragment of flagellin, were absent in strains that carried a cya mutation. Their synthesis was depressed in strains grown under conditions of catabolite repression. The presence of the cfs mutation restored the specific synthesis of these two polypeptides. We suggest that the formation of the flaI gene product is the step in flagellar synthesis that is catabolite sensitive and requires cAMP. We propose a regulatory function for the product of the flaI gene. Images PMID:4373438

  9. Role of ND10 nuclear bodies in the chromatin repression of HSV-1.

    PubMed

    Gu, Haidong; Zheng, Yi

    2016-01-01

    Herpes simplex virus (HSV) is a neurotropic virus that establishes lifelong latent infection in human ganglion sensory neurons. This unique life cycle necessitates an intimate relation between the host defenses and virus counteractions over the long course of infection. Two important aspects of host anti-viral defense, nuclear substructure restriction and epigenetic chromatin regulation, have been intensively studied in the recent years. Upon viral DNA entering the nucleus, components of discrete nuclear bodies termed nuclear domain 10 (ND10), converge at viral DNA and place restrictions on viral gene expression. Meanwhile the infected cell mobilizes its histones and histone-associated repressors to force the viral DNA into nucleosome-like structures and also represses viral transcription. Both anti-viral strategies are negated by various HSV countermeasures. One HSV gene transactivator, infected cell protein 0 (ICP0), is a key player in antagonizing both the ND10 restriction and chromatin repression. On one hand, ICP0 uses its E3 ubiquitin ligase activity to target major ND10 components for proteasome-dependent degradation and thereafter disrupts the ND10 nuclear bodies. On the other hand, ICP0 participates in de-repressing the HSV chromatin by changing histone composition or modification and therefore activates viral transcription. Involvement of a single viral protein in two seemingly different pathways suggests that there is coordination in host anti-viral defense mechanisms and also cooperation in viral counteraction strategies. In this review, we summarize recent advances in understanding the role of chromatin regulation and ND10 dynamics in both lytic and latent HSV infection. We focus on the new observations showing that ND10 nuclear bodies play a critical role in cellular chromatin regulation. We intend to find the connections between the two major anti-viral defense pathways, chromatin remodeling and ND10 structure, in order to achieve a better

  10. The Pseudomonas aeruginosa Catabolite Repression Control Protein Crc Is Devoid of RNA Binding Activity

    PubMed Central

    Djinovic-Carugo, Kristina; Bläsi, Udo

    2013-01-01

    The Crc protein has been shown to mediate catabolite repression control in Pseudomonas, leading to a preferential assimilation of carbon sources. It has been suggested that Crc acts as a translational repressor of mRNAs, encoding functions involved in uptake and breakdown of different carbon sources. Moreover, the regulatory RNA CrcZ, the level of which is increased in the presence of less preferred carbon sources, was suggested to bind to and sequester Crc, resulting in a relief of catabolite repression. Here, we determined the crystal structure of Pseudomonas aeruginosa Crc, a member of apurinic/apyrimidinic (AP) endonuclease family, at 1.8 Å. Although Crc displays high sequence similarity with its orthologs, there are amino acid alterations in the area corresponding to the active site in AP proteins. Unlike typical AP endonuclease family proteins, Crc has a reduced overall positive charge and the conserved positively charged amino-acid residues of the DNA-binding surface of AP proteins are partially substituted by negatively charged, polar and hydrophobic residues. Crc protein purified to homogeneity from P. aeruginosa did neither display DNase activity, nor did it bind to previously identified RNA substrates. Rather, the RNA chaperone Hfq was identified as a contaminant in His-tagged Crc preparations purified by one step Ni-affinity chromatography from Escherichia coli, and was shown to account for the RNA binding activity observed with the His-Crc preparations. Taken together, these data challenge a role of Crc as a direct translational repressor in carbon catabolite repression in P. aeruginosa. PMID:23717639

  11. Nuclear factor 1 family members mediate repression of the BK virus late promoter.

    PubMed

    Kraus, R J; Shadley, L; Mertz, J E

    2001-08-15

    BK virus (BKV) is a member of the polyoma virus family that is ubiquitous in humans. Its 5-kb DNA genome consists of a bidirectional promoter region situated between two temporally regulated coding regions. We mapped the transcription initiation site of the major late promoter (MLP) of the archetype strain BKV(WW) to nt 185. We found that it lies within the sequence TGGN6GCCA, a binding site for members of the nuclear factor 1 (NF1) family of transcription factors. Competition electrophoretic mobility shift and immunoshift assays confirmed that NF1 factors present in nuclear extracts of HeLa and CV-1 cells bind to the BKV-MLP. Because BKV(WW) grew poorly in tissue culture and failed to express detectable levels of RNA in vitro, SV40-BKV chimeric viruses were constructed to investigate the transcriptional function of this NF-1 binding site. These sequence-specific factors repressed transcription in a cell-free system when template copy number was low. This repression could be relieved by the addition in trans of oligonucleotides containing wild-type, but not mutated, NF1-binding site sequences. SV40-BKV chimeric viruses defective in this NF1-binding site overproduced late RNA at early, but not late, times after transfection of CV-1 cells. Finally, transient expression in 293 cells of cDNAs encoding the family members NF1-A4, NF1-C2, and NF1-X2 specifically repressed transcription from the BKV late promoter approximately 3-, 10-, and 10-fold, respectively, in a DNA binding-dependent manner. We conclude that some members of the NF1 family of transcription factors can act as sequence-specific cellular repressors of the BKV-MLP. We propose that titration of these and other cellular repressors by viral genome amplification may be responsible in part for the replication-dependent component of the early-to-late switch in BKV gene expression.

  12. Different Levels of Catabolite Repression Optimize Growth in Stable and Variable Environments

    PubMed Central

    New, Aaron M.; Cerulus, Bram; Govers, Sander K.; Perez-Samper, Gemma; Zhu, Bo; Boogmans, Sarah; Xavier, Joao B.; Verstrepen, Kevin J.

    2014-01-01

    Organisms respond to environmental changes by adapting the expression of key genes. However, such transcriptional reprogramming requires time and energy, and may also leave the organism ill-adapted when the original environment returns. Here, we study the dynamics of transcriptional reprogramming and fitness in the model eukaryote Saccharomyces cerevisiae in response to changing carbon environments. Population and single-cell analyses reveal that some wild yeast strains rapidly and uniformly adapt gene expression and growth to changing carbon sources, whereas other strains respond more slowly, resulting in long periods of slow growth (the so-called “lag phase”) and large differences between individual cells within the population. We exploit this natural heterogeneity to evolve a set of mutants that demonstrate how the frequency and duration of changes in carbon source can favor different carbon catabolite repression strategies. At one end of this spectrum are “specialist” strategies that display high rates of growth in stable environments, with more stringent catabolite repression and slower transcriptional reprogramming. The other mutants display less stringent catabolite repression, resulting in leaky expression of genes that are not required for growth in glucose. This “generalist” strategy reduces fitness in glucose, but allows faster transcriptional reprogramming and shorter lag phases when the cells need to shift to alternative carbon sources. Whole-genome sequencing of these mutants reveals that mutations in key regulatory genes such as HXK2 and STD1 adjust the regulation and transcriptional noise of metabolic genes, with some mutations leading to alternative gene regulatory strategies that allow “stochastic sensing” of the environment. Together, our study unmasks how variable and stable environments favor distinct strategies of transcriptional reprogramming and growth. PMID:24453942

  13. Unliganded Thyroid Hormone Receptor α Regulates Developmental Timing via Gene Repression in Xenopus tropicalis

    PubMed Central

    Choi, Jinyoung; Suzuki, Ken-ichi T.; Sakuma, Tetsushi; Shewade, Leena; Yamamoto, Takashi

    2015-01-01

    Thyroid hormone (TH) receptor (TR) expression begins early in development in all vertebrates when circulating TH levels are absent or minimal, yet few developmental roles for unliganded TRs have been established. Unliganded TRs are expected to repress TH-response genes, increase tissue responsivity to TH, and regulate the timing of developmental events. Here we examined the role of unliganded TRα in gene repression and development in Xenopus tropicalis. We used transcription activator-like effector nuclease gene disruption technology to generate founder animals with mutations in the TRα gene and bred them to produce F1 offspring with a normal phenotype and a mutant phenotype, characterized by precocious hind limb development. Offspring with a normal phenotype had zero or one disrupted TRα alleles, and tadpoles with the mutant hind limb phenotype had two truncated TRα alleles with frame shift mutations between the two zinc fingers followed by 40–50 mutant amino acids and then an out-of-frame stop codon. We examined TH-response gene expression and early larval development with and without exogenous TH in F1 offspring. As hypothesized, mutant phenotype tadpoles had increased expression of TH-response genes in the absence of TH and impaired induction of these same genes after exogenous TH treatment, compared with normal phenotype animals. Also, mutant hind limb phenotype animals had reduced hind limb and gill responsivity to exogenous TH. Similar results in methimazole-treated tadpoles showed that increased TH-response gene expression and precocious development were not due to early production of TH. These results indicate that unliganded TRα delays developmental progression by repressing TH-response genes. PMID:25456067

  14. Different levels of catabolite repression optimize growth in stable and variable environments.

    PubMed

    New, Aaron M; Cerulus, Bram; Govers, Sander K; Perez-Samper, Gemma; Zhu, Bo; Boogmans, Sarah; Xavier, Joao B; Verstrepen, Kevin J

    2014-01-01

    Organisms respond to environmental changes by adapting the expression of key genes. However, such transcriptional reprogramming requires time and energy, and may also leave the organism ill-adapted when the original environment returns. Here, we study the dynamics of transcriptional reprogramming and fitness in the model eukaryote Saccharomyces cerevisiae in response to changing carbon environments. Population and single-cell analyses reveal that some wild yeast strains rapidly and uniformly adapt gene expression and growth to changing carbon sources, whereas other strains respond more slowly, resulting in long periods of slow growth (the so-called "lag phase") and large differences between individual cells within the population. We exploit this natural heterogeneity to evolve a set of mutants that demonstrate how the frequency and duration of changes in carbon source can favor different carbon catabolite repression strategies. At one end of this spectrum are "specialist" strategies that display high rates of growth in stable environments, with more stringent catabolite repression and slower transcriptional reprogramming. The other mutants display less stringent catabolite repression, resulting in leaky expression of genes that are not required for growth in glucose. This "generalist" strategy reduces fitness in glucose, but allows faster transcriptional reprogramming and shorter lag phases when the cells need to shift to alternative carbon sources. Whole-genome sequencing of these mutants reveals that mutations in key regulatory genes such as HXK2 and STD1 adjust the regulation and transcriptional noise of metabolic genes, with some mutations leading to alternative gene regulatory strategies that allow "stochastic sensing" of the environment. Together, our study unmasks how variable and stable environments favor distinct strategies of transcriptional reprogramming and growth. PMID:24453942

  15. ZBTB2 increases PDK4 expression by transcriptional repression of RelA/p65

    PubMed Central

    Kim, Min-Young; Koh, Dong-In; Choi, Won-Il; Jeon, Bu-Nam; Jeong, Deok-yoon; Kim, Kyung-Sup; Kim, Kunhong; Kim, Se-Hoon; Hur, Man-Wook

    2015-01-01

    The NF-κB is found in almost all animal cell types and is involved in a myriad of cellular responses. Aberrant expression of NF-κB has been linked to cancer, inflammatory diseases and improper development. Little is known about transcriptional regulation of the NF-κB family member gene RelA/p65. Sp1 plays a key role in the expression of the RelA/p65 gene. ZBTB2 represses transcription of the gene by inhibiting Sp1 binding to a Sp1-binding GC-box in the RelA/p65 proximal promoter (bp, −31 to −21). Moreover, recent studies revealed that RelA/p65 directly binds to the peroxisome proliferator-activated receptor-γ coactivator1α (PGC1α) to decrease transcriptional activation of the PGC1α target gene PDK4, whose gene product inhibits pyruvate dehydrogenase (PDH), a key regulator of TCA cycle flux. Accordingly, we observed that RelA/p65 repression by ZBTB2 indirectly results in increased PDK4 expression, which inhibits PDH. Consequently, in cells with ectopic ZBTB2, the concentrations of pyruvate and lactate were higher than those in normal cells, indicating changes in glucose metabolism flux favoring glycolysis over the TCA cycle. Knockdown of ZBTB2 in mouse xenografts decreased tumor growth. ZBTB2 may increase cell proliferation by reprogramming glucose metabolic pathways to favor glycolysis by upregulating PDK4 expression via repression of RelA/p65 expression. PMID:25609694

  16. Intrinsic plasmids influence MicF-mediated translational repression of ompF in Yersinia pestis

    PubMed Central

    Liu, Zizhong; Wang, Haili; Wang, Hongduo; Wang, Jing; Bi, Yujing; Wang, Xiaoyi; Yang, Ruifu; Han, Yanping

    2015-01-01

    Yersinia pestis, which is the causative agent of plague, has acquired exceptional pathogenicity potential during its evolution from Y. pseudotuberculosis. Two laterally acquired plasmids, namely, pMT1 and pPCP1, are specific to Y. pestis and are critical for pathogenesis and flea transmission. Small regulatory RNAs (sRNAs) commonly function as regulators of gene expression in bacteria. MicF, is a paradigmatic sRNA that acts as a post-transcriptional repressor through imperfect base pairing with the 5′-UTR of its target mRNA, ompF, in Escherichia coli. The high sequence conservation and minor variation in the RNA duplex of MicF-ompF has been reported in Yersinia. In this study, we utilized super-folder GFP reporter gene fusion to validate the post-transcriptional MicF-mediated regulation of target mRNA ompF in Y. pestis. Unexpectedly, upon MicF overexpression, the slightly upregulated expression of OmpF were found in the wild-type strain, which contradicted the previously established model. Interestingly, the translational repression of ompF target fusions was restored in the intrinsic plasmids-cured Y. pestis strain, suggesting intrinsic plasmids influence the MicF-mediated translational repression of ompF in Y. pestis. Further examination showed that plasmid pPCP1 is likely the main contributor to the abolishment of MicF-mediated translational repression of endogenous or plasmid-borne ompF. It represents that the possible roles of intrinsic plasmids should be considered upon investigating sRNA-mediated gene regulation, at least in Y. pestis, even if the exact mechanism is not fully understood. PMID:26347736

  17. Endocytosis of a maltose permease is induced when amylolytic enzyme production is repressed in Aspergillus oryzae.

    PubMed

    Hiramoto, Tetsuya; Tanaka, Mizuki; Ichikawa, Takanori; Matsuura, Yuka; Hasegawa-Shiro, Sachiko; Shintani, Takahiro; Gomi, Katsuya

    2015-09-01

    In the filamentous fungus Aspergillus oryzae, amylolytic enzyme production is induced by the presence of maltose. Previously, we identified a putative maltose permease (MalP) gene in the maltose-utilizing cluster of A. oryzae. malP disruption causes a significant decrease in α-amylase activity and maltose consumption, indicating that MalP is a maltose transporter required for amylolytic enzyme production in A. oryzae. Although the expression of amylase genes and malP is repressed by the presence of glucose, the effect of glucose on the abundance of functional MalP is unknown. In this study, we examined the effect of glucose and other carbon sources on the subcellular localization of green fluorescence protein (GFP)-tagged MalP. After glucose addition, GFP-MalP at the plasma membrane was internalized and delivered to the vacuole. This glucose-induced internalization of GFP-MalP was inhibited by treatment with latrunculin B, an inhibitor of actin polymerization. Furthermore, GFP-MalP internalization was inhibited by repressing the HECT ubiquitin ligase HulA (ortholog of yeast Rsp5). These results suggest that MalP is transported to the vacuole by endocytosis in the presence of glucose. Besides glucose, mannose and 2-deoxyglucose also induced the endocytosis of GFP-MalP and amylolytic enzyme production was inhibited by the addition of these sugars. However, neither the subcellular localization of GFP-MalP nor amylolytic enzyme production was influenced by the addition of xylose or 3-O-methylglucose. These results imply that MalP endocytosis is induced when amylolytic enzyme production is repressed.

  18. Two cis elements collaborate to spatially repress transcription from a sea urchin promoter

    NASA Technical Reports Server (NTRS)

    Frudakis, T. N.; Wilt, F.

    1995-01-01

    The expression pattern of many territory-specific genes in metazoan embryos is maintained by an active process of negative spatial regulation. However, the mechanism of this strategy of gene regulation is not well understood in any system. Here we show that reporter constructs containing regulatory sequence for the SM30-alpha gene of Stronglyocentrotus purpuratus are expressed in a pattern congruent with that of the endogenous SM30 gene(s), largely as a result of active transcriptional repression in cell lineages in which the gene is not normally expressed. Chloramphenicol acetyl transferase assays of deletion constructs from the 2600-bp upstream region showed that repressive elements were present in the region from -1628 to -300. In situ hybridization analysis showed that the spatial fidelity of expression was severely compromised when the region from -1628 to -300 was deleted. Two highly repetitive sequence motifs, (G/A/C)CCCCT and (T/C)(T/A/C)CTTTT(T/A/C), are present in the -1628 to -300 region. Representatives of these elements were analyzed by gel mobility shift experiments and were found to interact specifically with protein in crude nuclear extracts. When oligonucleotides containing either sequence element were co-injected with a correctly regulated reporter as potential competitors, the reporter was expressed in inappropriate cells. When composite oligonucleotides, containing both sequence elements, were fused to a misregulated reporter, the expression of the reporter in inappropriate cells was suppressed. Comparison of composite oligonucleotides with oligonucleotides containing single constituent elements show that both sequence elements are required for effective spatial regulation. Thus, both individual elements are required, but only a composite element containing both elements is sufficient to function as a tissue-specific repressive element.

  19. Structure-Guided Discovery of Selective Antagonists for the Chromodomain of Polycomb Repressive Protein CBX7.

    PubMed

    Ren, Chunyan; Smith, Steven G; Yap, Kyoko; Li, SiDe; Li, Jiaojie; Mezei, Mihaly; Rodriguez, Yoel; Vincek, Adam; Aguilo, Francesca; Walsh, Martin J; Zhou, Ming-Ming

    2016-06-01

    The chromobox 7 (CBX7) protein of the polycomb repressive complex 1 (PRC1) functions to repress transcription of tumor suppressor p16 (INK4a) through long noncoding RNA, ANRIL (antisense noncoding RNA in the INK4 locus) directed chromodomain (ChD) binding to trimethylated lysine 27 of histone H3 (H3K27me3), resulting in chromatin compaction at the INK4a/ARF locus. In this study, we report structure-guided discovery of two distinct classes of small-molecule antagonists for the CBX7ChD. Our Class A compounds, a series including analogues of the previously reported MS452, inhibit CBX7ChD/methyl-lysine binding by occupying the H3K27me3 peptide binding site, whereas our Class B compound, the newly discovered MS351, appears to inhibit H3K27me3 binding when CBX7ChD is bound to RNA. Our crystal structure of the CBX7ChD/MS351 complex reveals the molecular details of ligand recognition by the aromatic cage residues that typically engage in methyl-lysine binding. We further demonstrate that MS351 effectively induces transcriptional derepression of CBX7 target genes, including p16 (INK4a) in mouse embryonic stem cells and human prostate cancer PC3 cells. Thus, MS351 represents a new class of ChD antagonists that selectively targets the biologically active form of CBX7 of the PRC1 in long noncoding RNA- and H3K27me3-directed gene transcriptional repression. PMID:27326334

  20. MicroRNA-22 promotes cell survival upon UV radiation by repressing PTEN

    SciTech Connect

    Tan, Guangyun; Shi, Yuling; Wu, Zhao-Hui

    2012-01-06

    Highlights: Black-Right-Pointing-Pointer miR-22 is induced in cells treated with UV radiation. Black-Right-Pointing-Pointer ATM is required for miR-22 induction in response to UV. Black-Right-Pointing-Pointer miR-22 targets 3 Prime -UTR of PTEN to repress its expression in UV-treated cells. Black-Right-Pointing-Pointer Upregulated miR-22 inhibits apoptosis in cells exposed to UV. -- Abstract: DNA damage response upon UV radiation involves a complex network of cellular events required for maintaining the homeostasis and restoring genomic stability of the cells. As a new class of players involved in DNA damage response, the regulation and function of microRNAs in response to UV remain poorly understood. Here we show that UV radiation induces a significant increase of miR-22 expression, which appears to be dependent on the activation of DNA damage responding kinase ATM (ataxia telangiectasia mutated). Increased miR-22 expression may result from enhanced miR-22 maturation in cells exposed to UV. We further found that tumor suppressor gene phosphatase and tensin homolog (PTEN) expression was inversely correlated with miR-22 induction and UV-induced PTEN repression was attenuated by overexpression of a miR-22 inhibitor. Moreover, increased miR-22 expression significantly inhibited the activation of caspase signaling cascade, leading to enhanced cell survival upon UV radiation. Collectively, these results indicate that miR-22 is an important player in the cellular stress response upon UV radiation, which may promote cell survival via the repression of PTEN expression.

  1. ATF3 represses PDX-1 expression in pancreatic β-cells.

    PubMed

    Jang, Min Kyung; Park, Hyun Jin; Jung, Myeong Ho

    2011-08-26

    The downregulation of PDX-1 expression plays an important role in development of type 2 diabetes. However, the negative regulator of PDX-1 expression is not well known. In this study, we analyzed the mouse PDX-1 promoter to characterize the effects of ATF3 on PDX-1 expression in pancreatic β-cells. Both thapsigargin treatment, an inducer of ER stress, and ATF3 expression decreased PDX-1 expression in pancreatic β-cells, MIN6N8. Furthermore, they also repressed the activity of -4.5 Kb promoter of mouse PDX-1 gene. Transfection studies with 5' deleted-reporters showed that ATF3 repressed the activity of 0.9Kb PDX-1 promoter, whereas it did not affect the activity of 0.7 Kb PDX-1 promoter, suggesting that ATF3 responsive element is located between the -903 and -702. An electrophoretic mobility shift assay and chromatin immunoprecipitation assay demonstrated that ATF3 binds directly to the promoter region spanning from -759 to -738. Moreover, mutation of the putative ATF/CRE site between -752 and -745 abrogated ATF3-mediated transrepression of the PDX-1 promoter. PDX-1 was decreased in MIN6N8 cells treated with high glucose or high palmitate, whereas ATF3 was increased, indicating that ATF3 plays a role in hyperglycemia or hyperlipidemia-mediated downregulation of PDX-1 expression. Collectively, these results demonstrate that ATF3 represses PDX-1 expression via binding to an ATF3-responsive element in its promoter, which plays an important role in suppression of pancreatic β-cells function.

  2. Three independent signalling pathways repress motility in Pseudomonas fluorescens F113.

    PubMed

    Navazo, Ana; Barahona, Emma; Redondo-Nieto, Miguel; Martínez-Granero, Francisco; Rivilla, Rafael; Martín, Marta

    2009-07-01

    Motility is one of the most important traits for rhizosphere colonization by pseudomonads. Despite this importance, motility is severely repressed in the rhizosphere-colonizing strain Pseudomonas fluorescens F113. This bacterium is unable to swarm under laboratory conditions and produce relatively small swimming haloes. However, phenotypic variants with the ability to swarm and producing swimming haloes up to 300% larger than the wild-type strain, arise during rhizosphere colonization. These variants harbour mutations in the genes encoding the GacA/GacS two-component system and in other genes. In order to identify genes and pathways implicated in motility repression, we have used generalized mutagenesis with transposons. Analysis of the mutants has shown that besides the Gac system, the Wsp system and the sadB gene, which have been previously implicated in cyclic di-GMP turnover, are implicated in motility repression: mutants in the gacS, sadB or wspR genes can swarm and produce swimming haloes larger than the wild-type strain. Epistasis analysis has shown that the pathways defined by each of these genes are independent, because double and triple mutants show an additive phenotype. Furthermore, GacS, SadB and WspR act at different levels. Expression of the fleQ gene, encoding the master regulator of flagella synthesis is higher in the gacS(-) and sadB(-) backgrounds than in the wild-type strain and this differential expression is reflected by a higher secretion of the flagellin protein FliC. Conversely, no differences in fleQ expression or FliC secretion were observed between the wild-type strain and the wspR(-) mutant.

  3. Cyclin D1 represses gluconeogenesis via inhibition of the transcriptional coactivator PGC1α.

    PubMed

    Bhalla, Kavita; Liu, Wan-Ju; Thompson, Keyata; Anders, Lars; Devarakonda, Srikripa; Dewi, Ruby; Buckley, Stephanie; Hwang, Bor-Jang; Polster, Brian; Dorsey, Susan G; Sun, Yezhou; Sicinski, Piotr; Girnun, Geoffrey D

    2014-10-01

    Hepatic gluconeogenesis is crucial to maintain normal blood glucose during periods of nutrient deprivation. Gluconeogenesis is controlled at multiple levels by a variety of signal transduction and transcriptional pathways. However, dysregulation of these pathways leads to hyperglycemia and type 2 diabetes. While the effects of various signaling pathways on gluconeogenesis are well established, the downstream signaling events repressing gluconeogenic gene expression are not as well understood. The cell-cycle regulator cyclin D1 is expressed in the liver, despite the liver being a quiescent tissue. The most well-studied function of cyclin D1 is activation of cyclin-dependent kinase 4 (CDK4), promoting progression of the cell cycle. We show here a novel role for cyclin D1 as a regulator of gluconeogenic and oxidative phosphorylation (OxPhos) gene expression. In mice, fasting decreases liver cyclin D1 expression, while refeeding induces cyclin D1 expression. Inhibition of CDK4 enhances the gluconeogenic gene expression, whereas cyclin D1-mediated activation of CDK4 represses the gluconeogenic gene-expression program in vitro and in vivo. Importantly, we show that cyclin D1 represses gluconeogenesis and OxPhos in part via inhibition of peroxisome proliferator-activated receptor γ coactivator-1α (PGC1α) activity in a CDK4-dependent manner. Indeed, we demonstrate that PGC1α is novel cyclin D1/CDK4 substrate. These studies reveal a novel role for cyclin D1 on metabolism via PGC1α and reveal a potential link between cell-cycle regulation and metabolic control of glucose homeostasis.

  4. A transcriptional repressive role for epithelial-specific ETS factor ELF3 on oestrogen receptor alpha in breast cancer cells.

    PubMed

    Gajulapalli, Vijaya Narasihma Reddy; Samanthapudi, Venkata Subramanyam Kumar; Pulaganti, Madhusudana; Khumukcham, Saratchandra Singh; Malisetty, Vijaya Lakhsmi; Guruprasad, Lalitha; Chitta, Suresh Kumar; Manavathi, Bramanandam

    2016-04-15

    Oestrogen receptor-α (ERα) is a ligand-dependent transcription factor that primarily mediates oestrogen (E2)-dependent gene transcription required for mammary gland development. Coregulators critically regulate ERα transcription functions by directly interacting with it. In the present study, we report that ELF3, an epithelial-specific ETS transcription factor, acts as a transcriptional repressor of ERα. Co-immunoprecipitation (Co-IP) analysis demonstrated that ELF3 strongly binds to ERα in the absence of E2, but ELF3 dissociation occurs upon E2 treatment in a dose- and time-dependent manner suggesting that E2 negatively influences such interaction. Domain mapping studies further revealed that the ETS (E-twenty six) domain of ELF3 interacts with the DNA binding domain of ERα. Accordingly, ELF3 inhibited ERα's DNA binding activity by preventing receptor dimerization, partly explaining the mechanism by which ELF3 represses ERα transcriptional activity. Ectopic expression of ELF3 decreases ERα transcriptional activity as demonstrated by oestrogen response elements (ERE)-luciferase reporter assay or by endogenous ERα target genes. Conversely ELF3 knockdown increases ERα transcriptional activity. Consistent with these results, ELF3 ectopic expression decreases E2-dependent MCF7 cell proliferation whereas ELF3 knockdown increases it. We also found that E2 induces ELF3 expression in MCF7 cells suggesting a negative feedback regulation of ERα signalling in breast cancer cells. A small peptide sequence of ELF3 derived through functional interaction between ERα and ELF3 could inhibit DNA binding activity of ERα and breast cancer cell growth. These findings demonstrate that ELF3 is a novel transcriptional repressor of ERα in breast cancer cells. Peptide interaction studies further represent a novel therapeutic option in breast cancer therapy.

  5. Wild-Type p53 Binds to the TATA-Binding Protein and Represses Transcription

    NASA Astrophysics Data System (ADS)

    Seto, Edward; Usheva, Anny; Zambetti, Gerard P.; Momand, Jamil; Horikoshi, Nobuo; Weinmann, Roberto; Levine, Arnold J.; Shenk, Thomas

    1992-12-01

    p53 activates transcription of genes with a p53 response element, and it can repress genes lacking the element. Here we demonstrate that wild-type but not mutant p53 inhibits transcription in a HeLa nuclear extract from minimal promoters. Wild-type but not mutant p53 binds to human TATA-binding protein (TBP). p53 does not bind to yeast TBP, and it cannot inhibit transcription in a HeLa extract where yeast TBP substitutes for human TBP. These results suggest a model in which p53 binds to TBP and interferes with transcriptional initiation.

  6. YjjQ Represses Transcription of flhDC and Additional Loci in Escherichia coli

    PubMed Central

    Wiebe, Helene; Gürlebeck, Doreen; Groß, Jana; Dreck, Katrin; Pannen, Derk; Ewers, Christa; Wieler, Lothar H.

    2015-01-01

    ABSTRACT The presumptive transcriptional regulator YjjQ has been identified as being virulence associated in avian pathogenic Escherichia coli (APEC). In this work, we characterize YjjQ as transcriptional repressor of the flhDC operon, encoding the master regulator of flagellar synthesis, and of additional loci. The latter include gfc (capsule 4 synthesis), ompC (outer membrane porin C), yfiRNB (regulated c-di-GMP synthesis), and loci of poorly defined function (ybhL and ymiA-yciX). We identify the YjjQ DNA-binding sites at the flhDC and gfc promoters and characterize a DNA-binding sequence motif present at all promoters found to be repressed by YjjQ. At the flhDC promoter, the YjjQ DNA-binding site overlaps the RcsA-RcsB DNA-binding site. RcsA-RcsB likewise represses the flhDC promoter, but the repression by YjjQ and that by RcsA-RcsB are independent of each other. These data suggest that YjjQ is an additional regulator involved in the complex control of flhDC at the level of transcription initiation. Furthermore, we show that YjjQ represses motility of the E. coli K-12 laboratory strain and of uropathogenic E. coli (UPEC) strains CFT073 and 536. Regulation of flhDC, yfiRNB, and additional loci by YjjQ may be features relevant for pathogenicity. IMPORTANCE Escherichia coli is a commensal and pathogenic bacterium causing intra- and extraintestinal infections in humans and farm animals. The pathogenicity of E. coli strains is determined by their particular genome content, which includes essential and associated virulence factors that control the cellular physiology in the host environment. However, the gene pools of commensal and pathogenic E. coli are not clearly differentiated, and the function of virulence-associated loci needs to be characterized. In this study, we characterize the function of yjjQ, encoding a transcription regulator that was identified as being virulence associated in avian pathogenic E. coli (APEC). We characterize YjjQ as transcriptional

  7. Histone H2A monoubiquitination promotes histone H3 methylation in Polycomb repression.

    PubMed

    Kalb, Reinhard; Latwiel, Sebastian; Baymaz, H Irem; Jansen, Pascal W T C; Müller, Christoph W; Vermeulen, Michiel; Müller, Jürg

    2014-06-01

    A key step in gene repression by Polycomb is trimethylation of histone H3 K27 by PCR2 to form H3K27me3. H3K27me3 provides a binding surface for PRC1. We show that monoubiquitination of histone H2A by PRC1-type complexes to form H2Aub creates a binding site for Jarid2-Aebp2-containing PRC2 and promotes H3K27 trimethylation on H2Aub nucleosomes. Jarid2, Aebp2 and H2Aub thus constitute components of a positive feedback loop establishing H3K27me3 chromatin domains.

  8. [Some problems about incapability to work in direct connection to repression of people applied for relevant pension in accordance to the act from 24.01.1991].

    PubMed

    Gronowska, Zofia; Wilmowska-Pietruszyńska, Anna

    2005-01-01

    In accordance to the act dated 24.01.1991 refeRring to combatants, victims of repression repressed in the years 1940-1956 apply for relevant pensions. There have been 6510 petitions for relevant pensions related to repression registered between 01.09.1997 to 31.12.2003 in the Social Insurance Department in Szczecin. It is very difficult to form an opinion of long lasting incapability to work related to repression ceasing over 50 years ago. During the medical examination most patents were 60 and over years old and have since retired. The actual system of relevant pensions in connection with repression made by Social Insurance Department is considered compensatory. It seems feasible to consider a new equal compensation system for all cases of repression.

  9. Human T-cell leukemia virus type 1 Tax oncoprotein represses the expression of the BCL11B tumor suppressor in T-cells.

    PubMed

    Takachi, Takayuki; Takahashi, Masahiko; Takahashi-Yoshita, Manami; Higuchi, Masaya; Obata, Miki; Mishima, Yukio; Okuda, Shujiro; Tanaka, Yuetsu; Matsuoka, Masao; Saitoh, Akihiko; Green, Patrick L; Fujii, Masahiro

    2015-04-01

    Human T-cell leukemia virus type 1 (HTLV-1) is the etiological agent of adult T cell leukemia (ATL), which is an aggressive form of T-cell malignancy. HTLV-1 oncoproteins, Tax and HBZ, play crucial roles in the immortalization of T-cells and/or leukemogenesis by dysregulating the cellular functions in the host. Recent studies show that HTLV-1-infected T-cells have reduced expression of the BCL11B tumor suppressor protein. In the present study, we explored whether Tax and/or HBZ play a role in downregulating BCL11B in HTLV-1-infected T-cells. Lentiviral transduction of Tax in a human T-cell line repressed the expression of BCL11B at both the protein and mRNA levels, whereas the transduction of HBZ had little effect on the expression. Tax mutants with a decreased activity for the NF-κB, CREB or PDZ protein pathways still showed a reduced expression of the BCL11B protein, thereby implicating a different function of Tax in BCL11B downregulation. In addition, the HTLV-2 Tax2 protein reduced the BCL11B protein expression in T-cells. Seven HTLV-1-infected T-cell lines, including three ATL-derived cell lines, showed reduced BCL11B mRNA and protein expression relative to an uninfected T-cell line, and the greatest reductions were in the cells expressing Tax. Collectively, these results indicate that Tax is responsible for suppressing BCL11B protein expression in HTLV-1-infected T-cells; Tax-mediated repression of BCL11B is another mechanism that Tax uses to promote oncogenesis of HTLV-1-infected T-cells.

  10. Synergy between the RE-1 silencer of transcription and NFkappaB in the repression of the neurotransmitter gene TAC1 in human mesenchymal stem cells.

    PubMed

    Greco, Steven J; Smirnov, Sergey V; Murthy, Raghav G; Rameshwar, Pranela

    2007-10-12

    The RE-1 silencer of transcription (REST) is a transcriptional regulator that represses neuron-specific genes in non-neuronal tissues by remodeling chromatin structure. We have utilized human mesenchymal stem cells (MSCs) as a research tool to understand the molecular mechanisms that regulate a neurogenic program of differentiation in non-neuronal tissue. MSCs are mesoderm-derived cells that generate specialized cells such as stroma, fat, bone, and cartilage. We have reported previously the transdifferentiation of MSCs into functional neuronal cells (Cho, K. J., Trzaska, K. A., Greco, S. J., McArdle, J., Wang, F. S., Ye, J.-H., and Rameshwar, P. (2005) Stem Cells 23, 383-391). Expression of the neurotransmitter gene TAC1 was detected only in neuronal cells and thus served as a model to study transcriptional regulation of neuron-specific genes in undifferentiated MSCs. Bone marrow stromal cells are known to transiently express TAC1 following stimulation with the microenvironmental factor interleukin-1alpha. We thus compared the effects of interleukin-1alpha stimulation and neuronal induction of MSCs on TAC1 regulation. Transcription factor mapping of the 5'-flanking region of the TAC1 promoter predicted two REST-binding sites adjacent to one NFkappaB site within exon 1. Chromatin immunoprecipitation, mutagenesis, and loss-of-function studies showed that both transcription factors synergistically mediated repression of TAC1 in the neurogenic and microenvironmental models. Together, the results support the novel finding of synergism between REST and NFkappaB in the suppression of TAC1 in non-neuronal cells.

  11. Role for Free Isoleucine or Glycyl-Leucine in the Repression of Threonine Deaminase in Escherichia coli

    PubMed Central

    Wasmuth, John J.; Umbarger, H. E.

    1974-01-01

    In Escherichia coli, the three branched-chain amino acid activating enzymes appear to be essential for multivalent repression of the isoleucine- and valine-forming enzymes. The results of experiments with a mutant, strain CU18, having an altered threonine deaminase, indicate that free isoleucine and some form of threonine deaminase (the product of the ilvA gene) are also involved in multivalent repression. This strain exhibits abnormally high derepressibility but normal repressibility of its ilv gene products, and its threonine deaminase is inhibited only by high concentrations of isoleucine. In strain CU18, the isoleucine analogue, thiaisoleucine, is incapable of replacing isoleucine in the multivalent repression of the ilv genes, whereas the analogue can fully replace the natural amino acid in repression in other strains examined. The dipeptide, glycyl-leucine, which, like isoleucine, is a heterotropic negative effector of threonine deaminase but is not a substrate for isoleucyl-transfer ribonucleic acid synthetase, can completely prevent the accumulation of threonine deaminase-forming potential during isoleucine starvation in strains with normal threonine deaminases. It can not, however, prevent such accumulation in strain CU18 or in other strains in which threonine deaminase is insensitive to any concentration of isoleucine. PMID:4587610

  12. Polycomb Repressive Complex 2 Regulates MiR-200b in Retinal Endothelial Cells: Potential Relevance in Diabetic Retinopathy

    PubMed Central

    Ruiz, Michael Anthony; Feng, Biao; Chakrabarti, Subrata

    2015-01-01

    Glucose-induced augmented vascular endothelial growth factor (VEGF) production is a key event in diabetic retinopathy. We have previously demonstrated that downregulation of miR-200b increases VEGF, mediating structural and functional changes in the retina in diabetes. However, mechanisms regulating miR-200b in diabetes are not known. Histone methyltransferase complex, Polycomb Repressive Complex 2 (PRC2), has been shown to repress miRNAs in neoplastic process. We hypothesized that, in diabetes, PRC2 represses miR-200b through its histone H3 lysine-27 trimethylation mark. We show that human retinal microvascular endothelial cells exposed to high levels of glucose regulate miR-200b repression through histone methylation and that inhibition of PRC2 increases miR-200b while reducing VEGF. Furthermore, retinal tissue from animal models of diabetes showed increased expression of major PRC2 components, demonstrating in vivo relevance. This research established a repressive relationship between PRC2 and miR-200b, providing evidence of a novel mechanism of miRNA regulation through histone methylation. PMID:25884496

  13. Extragenic suppressors of yeast glucose derepression mutants leading to constitutive synthesis of several glucose-repressible enzymes.

    PubMed

    Schüller, H J; Entian, K D

    1991-03-01

    Saccharomyces cerevisiae regulatory genes CAT1 and CAT3 constitute a positive control circuit necessary for derepression of gluconeogenic and disaccharide-utilizing enzymes. Mutations within these genes are epistatic to hxk2 and hex2, which cause defects in glucose repression. cat1 and cat3 mutants are unable to grow in the presence of nonfermentable carbon sources or maltose. Stable gene disruptions were constructed inside these genes, and the resulting growth deficiencies were used for selecting epistatic mutations. The revertants obtained were tested for glucose repression, and those showing altered regulatory properties were further investigated. Most revertants belonged to a single complementation group called cat4. This recessive mutation caused a defect in glucose repression of invertase, maltase, and iso-1-cytochrome c. Additionally, hexokinase activity was increased. Gluconeogenic enzymes are still normally repressible in cat4 mutants. The occurrence of recombination of cat1::HIS3 and cat3::LEU2 with some cat4 alleles allowed significant growth in the presence of ethanol, which could be attributed to a partial derepression of gluconeogenic enzymes. The cat4 complementation group was tested for allelism with hxk2, hex2, cat80, cid1, cyc8, and tup1 mutations, which were previously described as affecting glucose repression. Allelism tests and tetrad analysis clearly proved that the cat4 complementation group is a new class of mutant alleles affecting carbon source-dependent gene expression.

  14. Repressing the Keratinocyte Genome: How the Polycomb Complex Subunits Operate in Concert to Control Skin and Hair Follicle Development.

    PubMed

    Botchkarev, Vladimir A; Mardaryev, Andrei N

    2016-08-01

    The Polycomb group proteins are transcriptional repressors that are critically important in the control of stem cell activity and maintenance of the identity of differentiated cells. Polycomb proteins interact with each other to form chromatin-associated repressive complexes (Polycomb repressive complexes 1 and 2) leading to chromatin compaction and gene silencing. However, the roles of the distinct components of the Polycomb repressive complex 2 in the control of skin development and keratinocyte differentiation remain obscure. Dauber et al. demonstrate the conditional ablations of three essential Polycomb repressive complex 2 subunits (EED, Suz12, or Ezh1/2) in the epidermal progenitors result in quite similar skin phenotypes including premature acquisition of a functional epidermal barrier, formation of ectopic Merkel cells, and defective postnatal hair follicle development. The reported data demonstrate that in skin epithelia, EED, Suz12, and Ezh1/2 function largely as subunits of the Polycomb repressive complex 2, which is important in the context of data demonstrating their independent activities in other cell types. The report provides an important platform for further analyses of the role of distinct Polycomb components in the control of gene expression programs in the disorders of epidermal differentiation, such as psoriasis and epidermal cancer. PMID:27450498

  15. NuRD mediates activating and repressive functions of GATA-1 and FOG-1 during blood development.

    PubMed

    Miccio, Annarita; Wang, Yuhuan; Hong, Wei; Gregory, Gregory D; Wang, Hongxin; Yu, Xiang; Choi, John K; Shelat, Suresh; Tong, Wei; Poncz, Mortimer; Blobel, Gerd A

    2010-01-20

    GATA transcription factors interact with FOG proteins to regulate tissue development by activating and repressing transcription. FOG-1 (ZFPM1), a co-factor for the haematopoietic factor GATA-1, binds to the NuRD co-repressor complex through a conserved N-terminal motif. Surprisingly, we detected NuRD components at both repressed and active GATA-1/FOG-1 target genes in vivo. In addition, while NuRD is required for transcriptional repression in certain contexts, we show a direct requirement of NuRD also for FOG-1-dependent transcriptional activation. Mice in which the FOG-1/NuRD interaction is disrupted display defects similar to germline mutations in the Gata1 and Fog1 genes, including anaemia and macrothrombocytopaenia. Gene expression analysis in primary mutant erythroid cells and megakaryocytes (MKs) revealed an essential function for NuRD during both the repression and activation of select GATA-1/FOG-1 target genes. These results show that NuRD is a critical co-factor for FOG-1 and underscore the versatile use of NuRD by lineage-specific transcription factors to activate and repress gene transcription in the appropriate cellular and genetic context.

  16. The Transcriptional Repressive Activity of KRAB Zinc Finger Proteins Does Not Correlate with Their Ability to Recruit TRIM28

    PubMed Central

    Murphy, Kristin E.; Shylo, Natalia A.; Alexander, Katherine A.; Churchill, Angela J.; Copperman, Cecilia; García-García, María J.

    2016-01-01

    KRAB domain Zinc finger proteins are one of the most abundant families of transcriptional regulators in higher vertebrates. The prevailing view is that KRAB domain proteins function as potent transcriptional repressors by recruiting TRIM28 and promoting heterochromatin spreading. However, the extent to which all KRAB domain proteins are TRIM28-dependent transcriptional repressors is currently unclear. Our studies on mouse ZFP568 revealed that TRIM28 recruitment by KRAB domain proteins is not sufficient to warrant transcriptional repressive activity. By using luciferase reporter assays and yeast two-hybrid experiments, we tested the ability of ZFP568 and other mouse KRAB domain proteins to repress transcription and bind TRIM28. We found that some mouse KRAB domain proteins are poor transcriptional repressors despite their ability to recruit TRIM28, while others showed strong KRAB-dependent transcriptional repression, but no TRIM28 binding. Together, our results show that the transcriptional repressive activity of KRAB-ZNF proteins does not correlate with their ability to recruit TRIM28, and provide evidence that KRAB domains can regulate transcription in a TRIM28-independent fashion. Our findings challenge the current understanding of the molecular mechanisms used by KRAB domain proteins to control gene expression and highlight that a high percentage of KRAB domain proteins in the mouse genome differ from the consensus KRAB sequence at amino acid residues that are critical for TRIM28 binding and/or repressive activity. PMID:27658112

  17. The oct3 gene, a gene for an embryonic transcription factor, is controlled by a retinoic acid repressible enhancer.

    PubMed Central

    Okazawa, H; Okamoto, K; Ishino, F; Ishino-Kaneko, T; Takeda, S; Toyoda, Y; Muramatsu, M; Hamada, H

    1991-01-01

    Oct3 is an embryonic octamer-binding transcription factor, whose expression is rapidly repressed by retinoic acid (RA). In this report, we have determined the transcriptional control region of the oct3 gene and studied the mechanism of the RA-mediated repression. The chromosomal oct3 gene consists of five exons. Three subdomains of the POU region and transactivating domain are located in separate exons. Transcription initiates at multiple sites in the GC-rich region lacking a typical TATA box. The upstream 2 kb region can confer the cell type-specific expression and RA-mediated repression. Analysis of the upstream region by deletion mutagenesis locates a cis element (RARE1) which functions as a stem cell-specific, yet RA-repressible, enhancer. Footprint and gel-retardation assays show that RARE1 is composed of two domains, each of which is recognized by distinct factors. Microinjection of oct3-lacZ constructs into fertilized eggs indicates that RARE1 can function in early embryos. We suggest that RARE1 is a critical cis element for oct3 gene expression in embryonic stem cells and for the RA-mediated repression. Images PMID:1915274

  18. Variable requirements for DNA-binding proteins at polycomb-dependent repressive regions in human HOX clusters.

    PubMed

    Woo, Caroline J; Kharchenko, Peter V; Daheron, Laurence; Park, Peter J; Kingston, Robert E

    2013-08-01

    Polycomb group (PcG)-mediated repression is an evolutionarily conserved process critical for cell fate determination and maintenance of gene expression during embryonic development. However, the mechanisms underlying PcG recruitment in mammals remain unclear since few regulatory sites have been identified. We report two novel prospective PcG-dependent regulatory elements within the human HOXB and HOXC clusters and compare their repressive activities to a previously identified element in the HOXD cluster. These regions recruited the PcG proteins BMI1 and SUZ12 to a reporter construct in mesenchymal stem cells and conferred repression that was dependent upon PcG expression. Furthermore, we examined the potential of two DNA-binding proteins, JARID2 and YY1, to regulate PcG activity at these three elements. JARID2 has differential requirements, whereas YY1 appears to be required for repressive activity at all 3 sites. We conclude that distinct elements of the mammalian HOX clusters can recruit components of the PcG complexes and confer repression, similar to what has been seen in Drosophila. These elements, however, have diverse requirements for binding factors, which, combined with previous data on other loci, speaks to the complexity of PcG targeting in mammals.

  19. Cell type-specific translational repression of Cyclin B during meiosis in males.

    PubMed

    Baker, Catherine Craig; Gim, Byung Soo; Fuller, Margaret T

    2015-10-01

    The unique cell cycle dynamics of meiosis are controlled by layers of regulation imposed on core mitotic cell cycle machinery components by the program of germ cell development. Although the mechanisms that regulate Cdk1/Cyclin B activity in meiosis in oocytes have been well studied, little is known about the trans-acting factors responsible for developmental control of these factors in male gametogenesis. During meiotic prophase in Drosophila males, transcript for the core cell cycle protein Cyclin B1 (CycB) is expressed in spermatocytes, but the protein does not accumulate in spermatocytes until just before the meiotic divisions. Here, we show that two interacting proteins, Rbp4 and Fest, expressed at the onset of spermatocyte differentiation under control of the developmental program of male gametogenesis, function to direct cell type- and stage-specific repression of translation of the core G2/M cell cycle component cycB during the specialized cell cycle of male meiosis. Binding of Fest to Rbp4 requires a 31-amino acid region within Rbp4. Rbp4 and Fest are required for translational repression of cycB in immature spermatocytes, with Rbp4 binding sequences in a cell type-specific shortened form of the cycB 3' UTR. Finally, we show that Fest is required for proper execution of meiosis I. PMID:26443637

  20. SH003 represses tumor angiogenesis by blocking VEGF binding to VEGFR2

    PubMed Central

    Choi, Hyeong Sim; Kim, Min Kyoung; Lee, Kangwook; Lee, Kang Min; Choi, Youn Kyung; Shin, Yong Cheol; Cho, Sung-Gook; Ko, Seong-Gyu

    2016-01-01

    Tumor angiogenesis is a key feature of cancer progression, because a tumor requires abundant oxygen and nutrition to grow. Here, we demonstrate that SH003, a mixed herbal extract containing Astragalus membranaceus (Am), Angelica gigas (Ag) and Trichosanthes Kirilowii Maximowicz (Tk), represses VEGF-induced tumor angiogenesis both in vitro and in vivo. SH003 inhibited VEGF-induced migration, invasion and tube formation in human umbilical vein endothelial cells (HUVEC) with no effect on the proliferation. SH003 reduced CD31-positive vessel numbers in tumor tissues and retarded tumor growth in our xenograft mouse tumor model, while SH003 did not affect pancreatic tumor cell viability. Consistently, SH003 inhibited VEGF-stimulated vascular permeability in ears and back skins. Moreover, SH003 inhibited VEGF-induced VEGFR2-dependent signaling by blocking VEGF binding to VEGFR2. Therefore, our data conclude that SH003 represses tumor angiogenesis by inhibiting VEGF-induced VEGFR2 activation, and suggest that SH003 may be useful for treating cancer. PMID:27105528

  1. The Pax gene eyegone facilitates repression of eye development in Tribolium

    PubMed Central

    2011-01-01

    Background The Pax transcription factor gene eyegone (eyg) participates in many developmental processes in Drosophila, including the Notch signaling activated postembryonic growth of the eye primordium, global development of the adult head and the development of the antenna. In contrast to other Pax genes, the functional conservation of eyg in species other than Drosophila has not yet been explored. Results We investigated the role of eyg during the postembryonic development of the red flour beetle Tribolium castaneum. Our results indicate conserved roles in antennal but not in eye development. Besides segmentation defects in the antenna, Tribolium eyg knockdown animals were characterized by eye enlargement due to the formation of surplus ommatidia at the central anterior edge of the compound eye. This effect resulted from the failure of the developing gena to locally repress retinal differentiation, which underlies the formation of the characteristic anterior notch in the Tribolium eye. Neither varying the induction time point of eyg knockdown nor knocking down components of the Janus kinase/Signal Transducer and Activators of Transcription signaling pathway in combination with eyg reduced eye size like in Drosophila. Conclusions Taken together, expression and knockdown data suggest that Tribolium eyg serves as a competence factor that facilitates the repression of retinal differentiation in response to an unknown signal produced in the developing gena. At the comparative level, our findings reveal diverged roles of eyg associated with the evolution of different modes of postembryonic head development in endopterygote insects as well as diversified head morphologies in darkling beetles. PMID:21463500

  2. Glucose-induced production of recombinant proteins in Hansenula polymorpha mutants deficient in catabolite repression.

    PubMed

    Krasovska, Olena S; Stasyk, Olena G; Nahorny, Viktor O; Stasyk, Oleh V; Granovski, Nikolai; Kordium, Vitaliy A; Vozianov, Oleksandr F; Sibirny, Andriy A

    2007-07-01

    The most commonly used expression platform for production of recombinant proteins in the methylotrophic yeast Hansenula polymorpha relies on the strong and strictly regulated promoter from the gene encoding peroxisomal enzyme alcohol (or methanol) oxidase (P(MOX)). Expression from P(MOX) is induced by methanol and is partially derepressed in glycerol or xylose medium, whereas in the presence of hexoses, disaccharides or ethanol, it is repressed. The need for methanol for maximal induction of gene expression in large-scale fermentation is a significant drawback, as this compound is toxic, flammable, supports a slow growth rate and requires extensive aeration. We isolated H. polymorpha mutants deficient in glucose repression of P(MOX) due to an impaired HpGCR1 gene, and other yet unidentified secondary mutations. The mutants exhibited pronounced defects in P(MOX) regulation only by hexoses and xylose, but not by disaccharides or ethanol. With one of these mutant strains as hosts, we developed a modified two-carbon source mode expression platform that utilizes convenient sugar substrates for growth (sucrose) and induction of recombinant protein expression (glucose or xylose). We demonstrate efficient regulatable by sugar carbon sources expression of three recombinant proteins: a secreted glucose oxidase from the fungus Aspergillus niger, a secreted mini pro-insulin, and an intracellular hepatitis B virus surface antigen in these mutant hosts. The modified expression platform preserves the favorable regulatable nature of P(MOX) without methanol, making a convenient alternative to the traditional system. PMID:17163508

  3. Adaptive selection and coevolution at the proteins of the Polycomb repressive complexes in Drosophila.

    PubMed

    Calvo-Martín, J M; Librado, P; Aguadé, M; Papaceit, M; Segarra, C

    2016-02-01

    Polycomb group (PcG) proteins are important epigenetic regulatory proteins that modulate the chromatin state through posttranslational histone modifications. These interacting proteins form multimeric complexes that repress gene expression. Thus, PcG proteins are expected to evolve coordinately, which might be reflected in their phylogenetic trees by concordant episodes of positive selection and by a correlation in evolutionary rates. In order to detect these signals of coevolution, the molecular evolution of 17 genes encoding the subunits of five Polycomb repressive complexes has been analyzed in the Drosophila genus. The observed distribution of divergence differs substantially among and along proteins. Indeed, CAF1 is uniformly conserved, whereas only the established protein domains are conserved in other proteins, such as PHO, PHOL, PSC, PH-P and ASX. Moreover, regions with a low divergence not yet described as protein domains are present, for instance, in SFMBT and SU(Z)12. Maximum likelihood methods indicate an acceleration in the nonsynonymous substitution rate at the lineage ancestral to the obscura group species in most genes encoding subunits of the Pcl-PRC2 complex and in genes Sfmbt, Psc and Kdm2. These methods also allow inferring the action of positive selection in this lineage at genes E(z) and Sfmbt. Finally, the protein interaction network predicted from the complete proteomes of 12 Drosophila species using a coevolutionary approach shows two tight PcG clusters. These clusters include well-established binary interactions among PcG proteins as well as new putative interactions.

  4. Cell type-specific translational repression of Cyclin B during meiosis in males

    PubMed Central

    Baker, Catherine Craig; Gim, Byung Soo; Fuller, Margaret T.

    2015-01-01

    The unique cell cycle dynamics of meiosis are controlled by layers of regulation imposed on core mitotic cell cycle machinery components by the program of germ cell development. Although the mechanisms that regulate Cdk1/Cyclin B activity in meiosis in oocytes have been well studied, little is known about the trans-acting factors responsible for developmental control of these factors in male gametogenesis. During meiotic prophase in Drosophila males, transcript for the core cell cycle protein Cyclin B1 (CycB) is expressed in spermatocytes, but the protein does not accumulate in spermatocytes until just before the meiotic divisions. Here, we show that two interacting proteins, Rbp4 and Fest, expressed at the onset of spermatocyte differentiation under control of the developmental program of male gametogenesis, function to direct cell type- and stage-specific repression of translation of the core G2/M cell cycle component cycB during the specialized cell cycle of male meiosis. Binding of Fest to Rbp4 requires a 31-amino acid region within Rbp4. Rbp4 and Fest are required for translational repression of cycB in immature spermatocytes, with Rbp4 binding sequences in a cell type-specific shortened form of the cycB 3′ UTR. Finally, we show that Fest is required for proper execution of meiosis I. PMID:26443637

  5. MOF-associated complexes ensure stem cell identity and Xist repression.

    PubMed

    Chelmicki, Tomasz; Dündar, Friederike; Turley, Matthew James; Khanam, Tasneem; Aktas, Tugce; Ramírez, Fidel; Gendrel, Anne-Valerie; Wright, Patrick Rudolf; Videm, Pavankumar; Backofen, Rolf; Heard, Edith; Manke, Thomas; Akhtar, Asifa

    2014-05-19

    Histone acetyl transferases (HATs) play distinct roles in many cellular processes and are frequently misregulated in cancers. Here, we study the regulatory potential of MYST1-(MOF)-containing MSL and NSL complexes in mouse embryonic stem cells (ESCs) and neuronal progenitors. We find that both complexes influence transcription by targeting promoters and TSS-distal enhancers. In contrast to flies, the MSL complex is not exclusively enriched on the X chromosome, yet it is crucial for mammalian X chromosome regulation as it specifically regulates Tsix, the major repressor of Xist lncRNA. MSL depletion leads to decreased Tsix expression, reduced REX1 recruitment, and consequently, enhanced accumulation of Xist and variable numbers of inactivated X chromosomes during early differentiation. The NSL complex provides additional, Tsix-independent repression of Xist by maintaining pluripotency. MSL and NSL complexes therefore act synergistically by using distinct pathways to ensure a fail-safe mechanism for the repression of X inactivation in ESCs.DOI: http://dx.doi.org/10.7554/eLife.02024.001.

  6. Age at earliest reported memory: associations with personality traits, behavioral health, and repression.

    PubMed

    Spirrison, C L; McCarley, N G

    2001-09-01

    The present study examined relationships between the age at earliest memory and the personality traits and behavioral health of 107 undergraduates. Participants answered questions on their earliest memory and completed the Myers-Briggs Type Indicator (MBTI) and a medical history form. Analyses indicated that continuous scores on two MBTI scales (Sensing-Intuition and Judging-Perceiving) were inversely related to age at earliest memory as were participant's self-reported drug and alcohol problems, emotional and psychological symptoms, accident rates, physical symptoms, and satisfaction with health. Respondents who reported first memories at or after 7 years of age (i.e., approximately 1 SD above the mean age at recalled memory) were classified as repressors. Repressors scored in the Sensing and Judging directions on the MBTI and reported significantly fewer emotional symptoms, accidents, psychological symptoms, and less health satisfaction than nonrepressors. Results are consistent with the age at earliest memory and repression literature and support the use of earliest memory age as an index of repression. PMID:11575624

  7. Translational repression determines a neuronal potential in Drosophila asymmetric cell division.

    PubMed

    Okabe, M; Imai, T; Kurusu, M; Hiromi, Y; Okano, H

    2001-05-01

    Asymmetric cell division is a fundamental strategy for generating cellular diversity during animal development. Daughter cells manifest asymmetry in their differential gene expression. Transcriptional regulation of this process has been the focus of many studies, whereas cell-type-specific 'translational' regulation has been considered to have a more minor role. During sensory organ development in Drosophila, Notch signalling directs the asymmetry between neuronal and non-neuronal lineages, and a zinc-finger transcriptional repressor Tramtrack69 (TTK69) acts downstream of Notch as a determinant of non-neuronal identity. Here we show that repression of TTK69 protein expression in the neuronal lineage occurs translationally rather than transcriptionally. This translational repression is achieved by a direct interaction between cis-acting sequences in the 3' untranslated region of ttk69 messenger RNA and its trans-acting repressor, the RNA-binding protein Musashi (MSI). Although msi can act downstream of Notch, Notch signalling does not affect MSI expression. Thus, Notch signalling is likely to regulate MSI activity rather than its expression. Our results define cell-type-specific translational control of ttk69 by MSI as a downstream event of Notch signalling in asymmetric cell division.

  8. GSF2 deletion increases lactic acid production by alleviating glucose repression in Saccharomyces cerevisiae

    PubMed Central

    Baek, Seung-Ho; Kwon, Eunice Y.; Kim, Seon-Young; Hahn, Ji-Sook

    2016-01-01

    Improving lactic acid (LA) tolerance is important for cost-effective microbial production of LA under acidic fermentation conditions. Previously, we generated LA-tolerant D-LA-producing S. cerevisiae strain JHY5310 by laboratory adaptive evolution of JHY5210. In this study, we performed whole genome sequencing of JHY5310, identifying four loss-of-function mutations in GSF2, SYN8, STM1, and SIF2 genes, which are responsible for the LA tolerance of JHY5310. Among the mutations, a nonsense mutation in GSF2 was identified as the major contributor to the improved LA tolerance and LA production in JHY5310. Deletion of GSF2 in the parental strain JHY5210 significantly improved glucose uptake and D-LA production levels, while derepressing glucose-repressed genes including genes involved in the respiratory pathway. Therefore, more efficient generation of ATP and NAD+ via respiration might rescue the growth defects of the LA-producing strain, where ATP depletion through extensive export of lactate and proton is one of major reasons for the impaired growth. Accordingly, alleviation of glucose repression by deleting MIG1 or HXK2 in JHY5210 also improved D-LA production. GSF2 deletion could be applied to various bioprocesses where increasing biomass yield or respiratory flux is desirable. PMID:27708428

  9. Spi-B inhibits human plasma cell differentiation by repressing BLIMP1 and XBP-1 expression.

    PubMed

    Schmidlin, Heike; Diehl, Sean A; Nagasawa, Maho; Scheeren, Ferenc A; Schotte, Remko; Uittenbogaart, Christel H; Spits, Hergen; Blom, Bianca

    2008-09-01

    The terminal differentiation of B cells into antibody-secreting plasma cells is tightly regulated by a complex network of transcription factors. Here we evaluated the role of the Ets factor Spi-B during terminal differentiation of human B cells. All mature tonsil and peripheral blood B-cell subsets expressed Spi-B, with the exception of plasma cells. Overexpression of Spi-B in CD19(+) B cells inhibited, similar to the known inhibitor BCL-6, the expression of plasma cell-associated surface markers and transcription factors as well as immunoglobulin production, ie, in vitro plasma cell differentiation. The arrest in B-cell differentiation enforced by Spi-B was independent of the transactivation domain, but dependent on the Ets-domain. By chromatin immunoprecipitation and assays using an inducible Spi-B construct BLIMP1 and XBP-1 were identified as direct target genes of Spi-B mediated repression. We propose a novel role for Spi-B in maintenance of germinal center and memory B cells by direct repression of major plasma cell factors and thereby plasma cell differentiation.

  10. Identification of two bvg-repressed surface proteins of Bordetella pertussis.

    PubMed Central

    Stenson, T H; Peppler, M S

    1995-01-01

    Bordetella pertussis, the etiological agent of whooping cough, has the ability to modulate its phenotype in response to environmental conditions by using the BvgAS sensory transduction system which is encoded by the vir locus (now known as bvg). The BvgAS system is part of a large family of two-component sensory transduction systems which are common to a number of pathogenic bacteria. Although much is known about the proteins which exist in the B. pertussis virulent (X-mode or phase I) phenotype, relatively little is known about the proteins produced in the avirulent (C-mode or phase III) phenotype. We used sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing techniques to demonstrate the existence of at least 22 vir-repressed molecules which are increased in the avirulent phenotype. In addition, a series of monoclonal antibodies which are specific for the surface of avirulent B. pertussis were developed. Using immunological and protein techniques, we characterized two of these antigens as surface-exposed proteins. One of these antigens is expressed only in B. pertussis but not in the related species B. parapertussis and B. bronchiseptica. The other antigen is also present in B. parapertussis and B. bronchiseptica but is expressed at lower levels which are not regulated by bvg. The identification and characterization of vir-repressed proteins (and the genes which encode and regulate them) may help elucidate a physiological role for modulation of this obligate human pathogen. PMID:7558280

  11. Repression of protein translation and mTOR signaling by proteasome inhibitor in colon cancer cells

    SciTech Connect

    Wu, William Ka Kei; Volta, Viviana; Cho, Chi Hin; Wu, Ya Chun; Li, Hai Tao; Yu, Le; Li, Zhi Jie; Sung, Joseph Jao Yiu

    2009-09-04

    Protein homeostasis relies on a balance between protein synthesis and protein degradation. The ubiquitin-proteasome system is a major catabolic pathway for protein degradation. In this respect, proteasome inhibition has been used therapeutically for the treatment of cancer. Whether inhibition of protein degradation by proteasome inhibitor can repress protein translation via a negative feedback mechanism, however, is unknown. In this study, proteasome inhibitor MG-132 lowered the proliferation of colon cancer cells HT-29 and SW1116. In this connection, MG-132 reduced the phosphorylation of mammalian target of rapamycin (mTOR) at Ser2448 and Ser2481 and the phosphorylation of its downstream targets 4E-BP1 and p70/p85 S6 kinases. Further analysis revealed that MG-132 inhibited protein translation as evidenced by the reductions of {sup 35}S-methionine incorporation and polysomes/80S ratio. Knockdown of raptor, a structural component of mTOR complex 1, mimicked the anti-proliferative effect of MG-132. To conclude, we demonstrate that the inhibition of protein degradation by proteasome inhibitor represses mTOR signaling and protein translation in colon cancer cells.

  12. Melanie Klein and Repression: an examination of some unpublished Notes of 1934.

    PubMed

    Hinshelwood, R D

    2006-01-01

    Fifteen pages of unpublished Notes were found in the Melanie Klein Archives dating from early 1934, a crucial moment in Klein's development. She was at this time, 1934, moving away from child analysis, whilst also rethinking and revising her allegiance to Karl Abraham's theory of the phases of libidinal development. These Notes, entitled "Early Repression Mechanism," show Klein struggling to develop what became her characteristic theories of the depressive position and the paranoid-schizoid position. Although these Notes are precursors of the paper Klein gave later to the IPA Congress in 1934, they also show the origins of the emphasis she and her followers eventually gave to "splitting" rather than repression. The Notes give us an insight into the way that she worked clinically at the time. We see Klein's confidence develop as she diverged from the classical theories and technique. Her ideas were based on close attention to the detail of her clinical material, rather than attacking theoretical problems directly. The Notes show her method of struggling to her own conclusions, and they offer us a chance to grasp the roots of the subsequent controversy over Kleinian thought.

  13. Anchoring of Heterochromatin to the Nuclear Lamina Reinforces Dosage Compensation-Mediated Gene Repression

    PubMed Central

    Brouhard, Elizabeth A.; Jiang, Jianhao; Sifuentes, Margarita H.

    2016-01-01

    Higher order chromosome structure and nuclear architecture can have profound effects on gene regulation. We analyzed how compartmentalizing the genome by tethering heterochromatic regions to the nuclear lamina affects dosage compensation in the nematode C. elegans. In this organism, the dosage compensation complex (DCC) binds both X chromosomes of hermaphrodites to repress transcription two-fold, thus balancing gene expression between XX hermaphrodites and XO males. X chromosome structure is disrupted by mutations in DCC subunits. Using X chromosome paint fluorescence microscopy, we found that X chromosome structure and subnuclear localization are also disrupted when the mechanisms that anchor heterochromatin to the nuclear lamina are defective. Strikingly, the heterochromatic left end of the X chromosome is less affected than the gene-rich middle region, which lacks heterochromatic anchors. These changes in X chromosome structure and subnuclear localization are accompanied by small, but significant levels of derepression of X-linked genes as measured by RNA-seq, without any observable defects in DCC localization and DCC-mediated changes in histone modifications. We propose a model in which heterochromatic tethers on the left arm of the X cooperate with the DCC to compact and peripherally relocate the X chromosomes, contributing to gene repression. PMID:27690361

  14. Repression of Cardiac Hypertrophy by KLF15: Underlying Mechanisms and Therapeutic Implications

    PubMed Central

    Leenders, Joost J.; Wijnen, Wino J.; van der Made, Ingeborg; Hiller, Monika; Swinnen, Melissa; Vandendriessche, Thierry; Chuah, Marinee; Pinto, Yigal M.; Creemers, Esther E.

    2012-01-01

    The Kruppel-like factor (KLF) family of transcription factors regulates diverse cell biological processes including proliferation, differentiation, survival and growth. Previous studies have shown that KLF15 inhibits cardiac hypertrophy by repressing the activity of pivotal cardiac transcription factors such as GATA4, MEF2 and myocardin. We set out this study to characterize the interaction of KLF15 with putative other transcription factors. We first show that KLF15 interacts with myocardin-related transcription factors (MRTFs) and strongly represses the transcriptional activity of MRTF-A and MRTF-B. Second, we identified a region within the C-terminal zinc fingers of KLF15 that contains the nuclear localization signal. Third, we investigated whether overexpression of KLF15 in the heart would have therapeutic potential. Using recombinant adeno-associated viruses (rAAV) we have overexpressed KLF15 specifically in the mouse heart and provide the first evidence that elevation of cardiac KLF15 levels prevents the development of cardiac hypertrophy in a model of Angiotensin II induced hypertrophy. PMID:22586493

  15. Interactions between Escherichia coli RNA polymerase and lambda repressor. Mutations in PRM affect repression of PR.

    PubMed

    Hwang, J J; Gussin, G N

    1988-04-20

    The rightward operator, OR, of bacteriophage lambda is part of a complex regulatory region that includes PRM, the promoter for repressor synthesis by a prophage, the rightward early promoter PR, and three repressor-binding sites, OR1, OR2 and OR3. By binding to OR2, repressor blocks transcription from PR and simultaneously stimulates the formation of open complexes between RNA polymerase and PRM. In this letter, we describe a test of the hypothesis that the interaction between RNA polymerase bound at PRM and repressor bound at OR2 increases the apparent affinity of repressor for OR. One implication of this hypothesis is that the amount of repressor required for repression of PR should be inversely correlated with PRM promoter strength. This is indeed the case. The amount of repressor required for 50% repression of PR is decreased by prmup-1, an "up" mutation of PRM, and is increased by prm- mutations. An unexpected finding is that in addition to their effect on the apparent affinity of repressor for OR, mutations in the -35 region of PRM alter the shape of repressor-titration curves. We propose that these mutations alter the interaction between RNA polymerase bound at PRM and repressor bound at OR2 in such a way that cooperativity in the binding of repressor to OR1 and OR2 is also disrupted.

  16. An epigenetic switch ensures transposon repression upon dynamic loss of DNA methylation in embryonic stem cells

    PubMed Central

    Walter, Marius; Teissandier, Aurélie; Pérez-Palacios, Raquel; Bourc'his, Déborah

    2016-01-01

    DNA methylation is extensively remodeled during mammalian gametogenesis and embryogenesis. Most transposons become hypomethylated, raising the question of their regulation in the absence of DNA methylation. To reproduce a rapid and extensive demethylation, we subjected mouse ES cells to chemically defined hypomethylating culture conditions. Surprisingly, we observed two phases of transposon regulation. After an initial burst of de-repression, various transposon families were efficiently re-silenced. This was accompanied by a reconfiguration of the repressive chromatin landscape: while H3K9me3 was stable, H3K9me2 globally disappeared and H3K27me3 accumulated at transposons. Interestingly, we observed that H3K9me3 and H3K27me3 occupy different transposon families or different territories within the same family, defining three functional categories of adaptive chromatin responses to DNA methylation loss. Our work highlights that H3K9me3 and, most importantly, polycomb-mediated H3K27me3 chromatin pathways can secure the control of a large spectrum of transposons in periods of intense DNA methylation change, ensuring longstanding genome stability. DOI: http://dx.doi.org/10.7554/eLife.11418.001 PMID:26814573

  17. Sox9 Transcriptionally Represses Spp1 to Prevent Matrix Mineralization in Maturing Heart Valves and Chondrocytes

    PubMed Central

    Ediriweera, Hasini N.; Lincoln, Joy

    2011-01-01

    Sox9 is an SRY-related transcription factor required for expression of cartilaginous genes in the developing skeletal system and heart valve structures. In contrast to positively regulating cartilaginous matrix, Sox9 also negatively regulates matrix mineralization associated with bone formation. While the transcriptional activation of Sox9 target genes during chondrogenesis has been characterized, the mechanisms by which Sox9 represses osteogenic processes are not so clear. Using ChIP-on-chip and luciferase assays we show that Sox9 binds and represses transactivation of the osteogenic glycoprotein Spp1. In addition, Sox9 knockdown in post natal mouse heart valve explants and rib chondrocyte cultures promotes Spp1 expression and matrix mineralization, while attenuating expression of cartilage genes Type II Collagen and Cartilage Link Protein. Further, we show that Spp1 is required for matrix mineralization induced by Sox9 knockdown. These studies provide insights into the molecular mechanisms by which Sox9 prevents pathologic matrix mineralization in tissues that must remain cartilaginous. PMID:22046352

  18. SUMOylation of MeCP2 is essential for transcriptional repression and hippocampal synapse development.

    PubMed

    Cheng, Ju; Huang, Min; Zhu, Ying; Xin, Yong-Juan; Zhao, Yun-Ke; Huang, Jian; Yu, Jian-Xiu; Zhou, Wen-Hao; Qiu, Zilong

    2014-03-01

    Methyl CpG binding protein 2 (MeCP2) binds to methylated DNA and acts as a transcriptional repressor. Mutations of human MECP2 gene lead to Rett syndrome, a severe neural developmental disorder. Here, we report that the MeCP2 protein can be modified by covalent linkage to small ubiquitin-like modifier (SUMO) and SUMOylation at lysine 223 is necessary for its transcriptional repression function. SUMOylation of MeCP2 is required for the recruitment of histone deacetylase complexes 1/2 complex. Mutation of MeCP2 lysine 223 to arginine abolishes its suppression of gene expression in mouse primary cortical neurons. Significantly, mutation of MeCP2 K223 site leads to developmental deficiency of rat hippocampal synapses in vitro and in vivo. Thus, the SUMOylation of MeCP2 at K223 is a critical switch for transcriptional repression and plays a crucial function in regulating synaptic development in the central nervous system.

  19. Gene induction and repression during terminal erythropoiesis are mediated by distinct epigenetic changes.

    PubMed

    Wong, Piu; Hattangadi, Shilpa M; Cheng, Albert W; Frampton, Garrett M; Young, Richard A; Lodish, Harvey F

    2011-10-20

    It is unclear how epigenetic changes regulate the induction of erythroid-specific genes during terminal erythropoiesis. Here we use global mRNA sequencing (mRNA-seq) and chromatin immunoprecipitation coupled to high-throughput sequencing (CHIP-seq) to investigate the changes that occur in mRNA levels, RNA polymerase II (Pol II) occupancy, and multiple posttranslational histone modifications when erythroid progenitors differentiate into late erythroblasts. Among genes induced during this developmental transition, there was an increase in the occupancy of Pol II, the activation marks H3K4me2, H3K4me3, H3K9Ac, and H4K16Ac, and the elongation methylation mark H3K79me2. In contrast, genes that were repressed during differentiation showed relative decreases in H3K79me2 levels yet had levels of Pol II binding and active histone marks similar to those in erythroid progenitors. We also found that relative changes in histone modification levels, in particular, H3K79me2 and H4K16ac, were most predictive of gene expression patterns. Our results suggest that in terminal erythropoiesis both promoter and elongation-associated marks contribute to the induction of erythroid genes, whereas gene repression is marked by changes in histone modifications mediating Pol II elongation. Our data map the epigenetic landscape of terminal erythropoiesis and suggest that control of transcription elongation regulates gene expression during terminal erythroid differentiation.

  20. CHES1/FOXN3 regulates cell proliferation by repressing PIM2 and protein biosynthesis

    PubMed Central

    Huot, Geneviève; Vernier, Mathieu; Bourdeau, Véronique; Doucet, Laurent; Saint-Germain, Emmanuelle; Gaumont-Leclerc, Marie-France; Moro, Alejandro; Ferbeyre, Gerardo

    2014-01-01

    The expression of the forkhead transcription factor checkpoint suppressor 1 (CHES1), also known as FOXN3, is reduced in many types of cancers. We show here that CHES1 decreases protein synthesis and cell proliferation in tumor cell lines but not in normal fibroblasts. Conversely, short hairpin RNA–mediated depletion of CHES1 increases tumor cell proliferation. Growth suppression depends on the CHES1 forkhead DNA-binding domain and correlates with the nuclear localization of CHES1. CHES1 represses the expression of multiple genes, including the kinases PIM2 and DYRK3, which regulate protein biosynthesis, and a number of genes in cilium biogenesis. CHES1 binds directly to the promoter of PIM2, and in cells expressing CHES1 the levels of PIM2 are reduced, as well as the phosphorylation of the PIM2 target 4EBP1. Overexpression of PIM2 or eIF4E partially reverses the antiproliferative effect of CHES1, indicating that PIM2 and protein biosynthesis are important targets of the antiproliferative effect of CHES1. In several human hematopoietic cancers, CHES1 and PIM2 expressions are inversely correlated, suggesting that repression of PIM2 by CHES1 is clinically relevant. PMID:24403608

  1. Pax6 represses androgen receptor-mediated transactivation by inhibiting recruitment of the coactivator SPBP.

    PubMed

    Elvenes, Julianne; Thomassen, Ernst Ivan Simon; Johnsen, Sylvia Sagen; Kaino, Katrine; Sjøttem, Eva; Johansen, Terje

    2011-01-01

    The androgen receptor (AR) has a central role in development and maintenance of the male reproductive system and in the etiology of prostate cancer. The transcription factor Pax6 has recently been reported to act as a repressor of AR and to be hypermethylated in prostate cancer cells. SPBP is a transcriptional regulator that previously has been shown to enhance the activity of Pax6. In this study we have identified SPBP to act as a transcriptional coactivator of AR. We also show that Pax6 inhibits SPBP-mediated enhancement of AR activity on the AR target gene probasin promoter, a repression that was partly reversed by increased expression of SPBP. Enhanced expression of Pax6 reduced the amount of SPBP associated with the probasin promoter when assayed by ChIP in HeLa cells. We mapped the interaction between both AR and SPBP, and AR and Pax6 to the DNA-binding domains of the involved proteins. Further binding studies revealed that Pax6 and SPBP compete for binding to AR. These results suggest that Pax6 represses AR activity by displacing and/or inhibiting recruitment of coactivators to AR target promoters. Understanding the mechanism for inhibition of AR coactivators can give rise to molecular targeted drugs for treatment of prostate cancer. PMID:21935435

  2. Pax6 Represses Androgen Receptor-Mediated Transactivation by Inhibiting Recruitment of the Coactivator SPBP

    PubMed Central

    Johnsen, Sylvia Sagen; Kaino, Katrine; Sjøttem, Eva; Johansen, Terje

    2011-01-01

    The androgen receptor (AR) has a central role in development and maintenance of the male reproductive system and in the etiology of prostate cancer. The transcription factor Pax6 has recently been reported to act as a repressor of AR and to be hypermethylated in prostate cancer cells. SPBP is a transcriptional regulator that previously has been shown to enhance the activity of Pax6. In this study we have identified SPBP to act as a transcriptional coactivator of AR. We also show that Pax6 inhibits SPBP-mediated enhancement of AR activity on the AR target gene probasin promoter, a repression that was partly reversed by increased expression of SPBP. Enhanced expression of Pax6 reduced the amount of SPBP associated with the probasin promoter when assayed by ChIP in HeLa cells. We mapped the interaction between both AR and SPBP, and AR and Pax6 to the DNA-binding domains of the involved proteins. Further binding studies revealed that Pax6 and SPBP compete for binding to AR. These results suggest that Pax6 represses AR activity by displacing and/or inhibiting recruitment of coactivators to AR target promoters. Understanding the mechanism for inhibition of AR coactivators can give rise to molecular targeted drugs for treatment of prostate cancer. PMID:21935435

  3. HDAC8 and STAT3 repress BMF gene activity in colon cancer cells.

    PubMed

    Kang, Y; Nian, H; Rajendran, P; Kim, E; Dashwood, W M; Pinto, J T; Boardman, L A; Thibodeau, S N; Limburg, P J; Löhr, C V; Bisson, W H; Williams, D E; Ho, E; Dashwood, R H

    2014-01-01

    Histone deacetylase (HDAC) inhibitors are undergoing clinical trials as anticancer agents, but some exhibit resistance mechanisms linked to anti-apoptotic Bcl-2 functions, such as BH3-only protein silencing. HDAC inhibitors that reactivate BH3-only family members might offer an improved therapeutic approach. We show here that a novel seleno-α-keto acid triggers global histone acetylation in human colon cancer cells and activates apoptosis in a p21-independent manner. Profiling of multiple survival factors identified a critical role for the BH3-only member Bcl-2-modifying factor (Bmf). On the corresponding BMF gene promoter, loss of HDAC8 was associated with signal transducer and activator of transcription 3 (STAT3)/specificity protein 3 (Sp3) transcription factor exchange and recruitment of p300. Treatment with a p300 inhibitor or transient overexpression of exogenous HDAC8 interfered with BMF induction, whereas RNAi-mediated silencing of STAT3 activated the target gene. This is the first report to identify a direct target gene of HDAC8 repression, namely, BMF. Interestingly, the repressive role of HDAC8 could be uncoupled from HDAC1 to trigger Bmf-mediated apoptosis. These findings have implications for the development of HDAC8-selective inhibitors as therapeutic agents, beyond the reported involvement of HDAC8 in childhood malignancy. PMID:25321483

  4. A Maternal System Initiating the Zygotic Developmental Program through Combinatorial Repression in the Ascidian Embryo

    PubMed Central

    Oda-Ishii, Izumi; Kubo, Atsushi; Kari, Willi; Suzuki, Nobuhiro; Rothbächer, Ute

    2016-01-01

    Maternal factors initiate the zygotic developmental program in animal embryos. In embryos of the chordate, Ciona intestinalis, three maternal factors—Gata.a, β-catenin, and Zic-r.a—are required to establish three domains of gene expression at the 16-cell stage; the animal hemisphere, vegetal hemisphere, and posterior vegetal domains. Here, we show how the maternal factors establish these domains. First, only β-catenin and its effector transcription factor, Tcf7, are required to establish the vegetal hemisphere domain. Second, genes specifically expressed in the posterior vegetal domain have additional repressive cis-elements that antagonize the activity of β-catenin/Tcf7. This antagonizing activity is suppressed by Zic-r.a, which is specifically localized in the posterior vegetal domain and binds to DNA indirectly through the interaction with Tcf7. Third, Gata.a directs specific gene expression in the animal hemisphere domain, because β-catenin/Tcf7 weakens the Gata.a-binding activity for target sites through a physical interaction in the vegetal cells. Thus, repressive regulation through protein-protein interactions among the maternal transcription factors is essential to establish the first distinct domains of gene expression in the chordate embryo. PMID:27152625

  5. Cyclic stretch of Embryonic Cardiomyocytes Increases Proliferation, Growth, and Expression While Repressing Tgf-β Signaling

    PubMed Central

    Banerjee, Indroneal; Carrion, Katrina; Serrano, Ricardo; Dyo, Jeffrey; Sasik, Roman; Lund, Sean; Willems, Erik; Aceves, Seema; Meili, Rudolph; Mercola, Mark; Chen, Ju; Zambon, Alexander; Hardiman, Gary; Doherty, Taylor A; Lange, Stephan; del Álamo, Juan C.; Nigam, Vishal

    2014-01-01

    Perturbed biomechanical stimuli are thought to be critical for the pathogenesis of a number of congenital heart defects, including Hypoplastic Left Heart Syndrome (HLHS). While embryonic cardiomyocytes experience biomechanical stretch every heart beat, their molecular responses to biomechanical stimuli during heart development are poorly understood. We hypothesized that biomechanical stimuli activate specific signaling pathways that impact proliferation, gene expression and myocyte contraction. The objective of this study was to expose embryonic mouse cardiomyocytes (EMCM) to cyclic stretch and examine key molecular and phenotypic responses. Analysis of RNA-Sequencing data demonstrated that gene ontology groups associated with myofibril and cardiac development were significantly modulated. Stretch increased EMCM proliferation, size, cardiac gene expression, and myofibril protein levels. Stretch also repressed several components belonging to the Transforming Growth Factor-β (Tgf-β) signaling pathway. EMCMs undergoing cyclic stretch had decreased Tgf-β expression, protein levels, and signaling. Furthermore, treatment of EMCMs with a Tgf-β inhibitor resulted in increased EMCM size. Functionally, Tgf-β signaling repressed EMCM proliferation and contractile function, as assayed via dynamic monolayer force microscopy (DMFM). Taken together, these data support the hypothesis that biomechanical stimuli play a vital role in normal cardiac development and for cardiac pathology, including HLHS. PMID:25446186

  6. Epigenetic repression of ribosomal RNA transcription by ROCK-dependent aberrant cytoskeletal organization

    PubMed Central

    Wu, Tse-Hsiang; Kuo, Yuan-Yeh; Lee, Hsiao-Hui; Kuo, Jean-Cheng; Ou, Meng-Hsin; Chang, Zee-Fen

    2016-01-01

    It is known that ribosomal RNA (rRNA) synthesis is regulated by cellular energy and proliferation status. In this study, we investigated rRNA gene transcription in response to cytoskeletal stress. Our data revealed that the cell shape constrained by isotropic but not elongated micropatterns in HeLa cells led to a significant reduction in rRNA transcription dependent on ROCK. Expression of a dominant-active form of ROCK also repressed rRNA transcription. Isotropic constraint and ROCK over-activation led to different types of aberrant F-actin organization, but their suppression effects on rRNA transcription were similarly reversed by inhibition of histone deacetylase (HDAC) or overexpression of a dominant negative form of Nesprin, which shields the signal transmitted from actin filament to the nuclear interior. We further showed that the binding of HDAC1 to the active fraction of rDNA genes is increased by ROCK over-activation, thus reducing H3K9/14 acetylation and suppressing transcription. Our results demonstrate an epigenetic control of active rDNA genes that represses rRNA transcription in response to the cytoskeletal stress. PMID:27350000

  7. HBXAP, a novel PHD-finger protein, possesses transcription repression activity.

    PubMed

    Shamay, Meir; Barak, Orr; Shaul, Yosef

    2002-04-01

    The PHD/LAP (plant homology domain/leukemia associated protein) finger motif is characteristically defined by a histidine and seven cysteines that are spatially arranged in a C4HC3 consensus sequence. This unique zinc finger, found primarily in a wide variety of chromatin-associated proteins, is considered to mediate protein-protein interactions. We have isolated a novel human PHD-finger protein, HBXAP (for hepatitis B virus x associated protein). HBXAP has three alternatively spliced isoforms. We also identified the Drosophila melanogaster HBXAP ortholog, gene CG8677. Based on alignment of four different proteins, we found a novel conserved domain in HBXAP that we designated the HBXAP conserved domain (XCD). We show that HBXAP represses transcription when recruited to DNA via the DNA binding of GAL4. Furthermore, the PHD finger alone suffices to repress transcription, thus attributing a functional role to this domain. The gene HBXAP is localized to the long arm of human chromosome 11 between q13.4 and q14.1. This region is amplified and rearranged in many tumors, suggesting a role for HBXAP in tumorigenesis similar to that of other PHD-containing proteins. PMID:11944984

  8. Lysine-specific demethylase 1 promotes brown adipose tissue thermogenesis via repressing glucocorticoid activation.

    PubMed

    Zeng, Xing; Jedrychowski, Mark P; Chen, Yi; Serag, Sara; Lavery, Gareth G; Gygi, Steve P; Spiegelman, Bruce M

    2016-08-15

    Brown adipocytes display phenotypic plasticity, as they can switch between the active states of fatty acid oxidation and energy dissipation versus a more dormant state. Cold exposure or β-adrenergic stimulation favors the active thermogenic state, whereas sympathetic denervation or glucocorticoid administration promotes more lipid accumulation. Our understanding of the molecular mechanisms underlying these switches is incomplete. Here we found that LSD1 (lysine-specific demethylase 1), a histone demethylase, regulates brown adipocyte metabolism in two ways. On the one hand, LSD1 associates with PRDM16 to repress expression of white fat-selective genes. On the other hand, LSD1 represses HSD11B1 (hydroxysteroid 11-β-dehydrogenase isozyme 1), a key glucocorticoid-activating enzyme, independently from PRDM16. Adipose-specific ablation of LSD1 impaired mitochondrial fatty acid oxidation capacity of the brown adipose tissue, reduced whole-body energy expenditure, and increased fat deposition, which can be significantly alleviated by simultaneously deleting HSD11B1. These findings establish a novel regulatory pathway connecting histone modification and hormone activation with mitochondrial oxidative capacity and whole-body energy homeostasis. PMID:27566776

  9. Trbp regulates heart function through miRNA-mediated Sox6 repression

    PubMed Central

    Ding, Jian; Chen, Jinghai; Wang, Yanqun; Kataoka, Masaharu; Ma, Lixin; Zhou, Pingzhu; Hu, Xiaoyun; Lin, Zhiqiang; Nie, Mao; Deng, Zhong-Liang; Pu, William T; Wang, Da-Zhi

    2015-01-01

    Cardiomyopathy is associated with altered expression of genes encoding contractile proteins. Here we show that Trbp (Tarbp2), an RNA binding protein, is required for normal heart function. Cardiac-specific inactivation of Trbp (TrbpcKO) caused progressive cardiomyopathy and lethal heart failure. Trbp loss of function resulted in upregulation of Sox6, repression of genes encoding normal cardiac slow-twitch myofiber proteins, and pathologically increased expression of skeletal fast-twitch myofiber genes. Remarkably, knockdown of Sox6 fully rescued the Trbp mutant phenotype, whereas Sox6 overexpression phenocopied the TrbpcKO phenotype. Trbp inactivation was mechanistically linked to Sox6 upregulation through altered processing of miR-208a, which is a direct inhibitor of Sox6. Transgenic overexpression of miR-208a sufficiently repressed Sox6, restored the balance of fast- and slow- twitch myofiber gene expression, and rescued cardiac function in TrbpcKO mice. Together, our studies reveal a novel Trbp-mediated microRNA processing mechanism in regulating a linear genetic cascade essential for normal heart function. PMID:26029872

  10. Neuronal development is promoted by weakened intrinsic antioxidant defences due to epigenetic repression of Nrf2

    PubMed Central

    Bell, Karen F.S.; Al-Mubarak, Bashayer; Martel, Marc-André; McKay, Sean; Wheelan, Nicola; Hasel, Philip; Márkus, Nóra M.; Baxter, Paul; Deighton, Ruth F.; Serio, Andrea; Bilican, Bilada; Chowdhry, Sudhir; Meakin, Paul J.; Ashford, Michael L.J.; Wyllie, David J.A.; Scannevin, Robert H.; Chandran, Siddharthan; Hayes, John D.; Hardingham, Giles E.

    2015-01-01

    Forebrain neurons have weak intrinsic antioxidant defences compared with astrocytes, but the molecular basis and purpose of this is poorly understood. We show that early in mouse cortical neuronal development in vitro and in vivo, expression of the master-regulator of antioxidant genes, transcription factor NF-E2-related-factor-2 (Nrf2), is repressed by epigenetic inactivation of its promoter. Consequently, in contrast to astrocytes or young neurons, maturing neurons possess negligible Nrf2-dependent antioxidant defences, and exhibit no transcriptional responses to Nrf2 activators, or to ablation of Nrf2's inhibitor Keap1. Neuronal Nrf2 inactivation seems to be required for proper development: in maturing neurons, ectopic Nrf2 expression inhibits neurite outgrowth and aborization, and electrophysiological maturation, including synaptogenesis. These defects arise because Nrf2 activity buffers neuronal redox status, inhibiting maturation processes dependent on redox-sensitive JNK and Wnt pathways. Thus, developmental epigenetic Nrf2 repression weakens neuronal antioxidant defences but is necessary to create an environment that supports neuronal development. PMID:25967870

  11. Military westernization and state repression in the post-Cold War era.

    PubMed

    Swed, Ori; Weinreb, Alexander

    2015-09-01

    The waves of unrest that have shaken the Arab world since December 2010 have highlighted significant differences in the readiness of the military to intervene in political unrest by forcefully suppressing dissent. We suggest that in the post-Cold War period, this readiness is inversely associated with the level of military westernization, which is a product of the acquisition of arms from western countries. We identify two mechanisms linking the acquisition of arms from western countries to less repressive responses: dependence and conditionality; and a longer-term diffusion of ideologies regarding the proper form of civil-military relations. Empirical support for our hypothesis is found in an analysis of 2523 cases of government response to political unrest in 138 countries in the 1996-2005 period. We find that military westernization mitigates state repression in general, with more pronounced effects in the poorest countries. However, we also identify substantial differences between the pre- and post-9/11 periods. PMID:26188453

  12. SUMOylation regulates the transcriptional repression activity of FOG-2 and its association with GATA-4.

    PubMed

    Perdomo, José; Jiang, Xing-Mai; Carter, Daniel R; Khachigian, Levon M; Chong, Beng H

    2012-01-01

    Friend of GATA 2 (FOG-2), a co-factor of several GATA transcription factors (GATA-4, -5 and 6), is a critical regulator of coronary vessel formation and heart morphogenesis. Here we demonstrate that FOG-2 is SUMOylated and that this modification modulates its transcriptional activity. FOG-2 SUMOylation occurs at four lysine residues (K324, 471, 915, 955) [corrected]. Three of these residues are part of the characteristic SUMO consensus site (ψKXE), while K955 is found in the less frequent TKXE motif. Absence of SUMOylation did not affect FOG-2's nuclear localization. However, mutation of the FOG-2 SUMOylation sites, or de-SUMOylation, with SENP-1 or SENP-8 resulted in stronger transcriptional repression activity in both heterologous cells and cardiomyocytes. Conversely, increased FOG-2 SUMOylation by overexpression of SUMO-1 or expression of a SUMO-1-FOG-2 fusion protein rendered FOG-2 incapable of repressing GATA-4-mediated activation of the B-type natriuretic peptide (BNP) promoter. Moreover, we demonstrate both increased interaction between a FOG-2 SUMO mutant and GATA-4 and enhanced SUMOylation of wild-type FOG-2 by co-expression of GATA-4. These data suggest a new dynamics in which GATA-4 may alter the activity of FOG-2 by influencing its SUMOylation status.

  13. Lamin A/C sustains PcG protein architecture, maintaining transcriptional repression at target genes

    PubMed Central

    Cesarini, Elisa; Mozzetta, Chiara; Marullo, Fabrizia; Gregoretti, Francesco; Gargiulo, Annagiusi; Columbaro, Marta; Cortesi, Alice; Antonelli, Laura; Di Pelino, Simona; Squarzoni, Stefano; Palacios, Daniela; Zippo, Alessio; Bodega, Beatrice; Oliva, Gennaro

    2015-01-01

    Beyond its role in providing structure to the nuclear envelope, lamin A/C is involved in transcriptional regulation. However, its cross talk with epigenetic factors—and how this cross talk influences physiological processes—is still unexplored. Key epigenetic regulators of development and differentiation are the Polycomb group (PcG) of proteins, organized in the nucleus as microscopically visible foci. Here, we show that lamin A/C is evolutionarily required for correct PcG protein nuclear compartmentalization. Confocal microscopy supported by new algorithms for image analysis reveals that lamin A/C knock-down leads to PcG protein foci disassembly and PcG protein dispersion. This causes detachment from chromatin and defects in PcG protein–mediated higher-order structures, thereby leading to impaired PcG protein repressive functions. Using myogenic differentiation as a model, we found that reduced levels of lamin A/C at the onset of differentiation led to an anticipation of the myogenic program because of an alteration of PcG protein–mediated transcriptional repression. Collectively, our results indicate that lamin A/C can modulate transcription through the regulation of PcG protein epigenetic factors. PMID:26553927

  14. Caenorhabditis elegans POT-1 and POT-2 repress telomere maintenance pathways.

    PubMed

    Shtessel, Ludmila; Lowden, Mia Rochelle; Cheng, Chen; Simon, Matt; Wang, Kyle; Ahmed, Shawn

    2013-02-01

    Telomeres are composed of simple tandem DNA repeats that protect the ends of linear chromosomes from replicative erosion or inappropriate DNA damage response mechanisms. The mammalian Protection Of Telomeres (POT1) protein interacts with single-stranded telomeric DNA and can exert positive and negative effects on telomere length. Of four distinct POT1 homologs in the roundworm Caenorhabditis elegans, deficiency for POT-1 or POT-2 resulted in progressive telomere elongation that occurred because both proteins negatively regulate telomerase. We created a POT-1::mCherry fusion protein that forms discrete foci at C. elegans telomeres, independent of POT-2, allowing for live analysis of telomere dynamics. Transgenic pot-1::mCherry repressed telomerase in pot-1 mutants. Animals deficient for pot-1, but not pot-2, displayed mildly enhanced telomere erosion rates in the absence of the telomerase reverse transcriptase, trt-1. However, trt-1; pot-1 double mutants exhibited delayed senescence in comparison to trt-1 animals, and senescence was further delayed in trt-1; pot-2; pot-1 triple mutants, some of which survived robustly in the absence of telomerase. Our results indicate that POT-1 and POT-2 play independent roles in suppressing a telomerase-independent telomere maintenance pathway but may function together to repress telomerase.

  15. Repression of the interleukin 6 gene promoter by p53 and the retinoblastoma susceptibility gene product

    SciTech Connect

    Santhanam, U.; Ray, A.; Sehgal, P.B. )

    1991-09-01

    The aberrant overexpression of interleukin 6 (IL-6) is implicated as an autocrine mechanism in the enhanced proliferation of the neoplastic cell elements in various B- and T-cell malignancies and in some carcinomas and sarcomas; many of these neoplasms have been shown to be associated with a mutated p53 gene. The possibility that wild-type (wt) p53, a nuclear tumor-suppressor protein, but not its transforming mutants might serve to repress IL-6 gene expression was investigated in HeLa cells. The authors transiently cotransfected these cells with constitutive cytomegalovirus (CMV) enhancer/promoter expression plasmids overproducing wt or mutant human or murine p53 and with appropriate chloramphenicol acetyltransferase (CAT) reporter plasmids containing the promoter elements of human IL-6, c-fos, or {beta}-actin genes or of porcine major histocompatibility complex (MHC) class I gene in pN-38 to evaluate the effect of the various p53 species on these promoters. These observations identify transcriptional repression as a property of p53 and suggest that p53 and RB may be involved as transcriptional repressors in modulating IL-6 gene expression during cellular differentiation and oncogenesis.

  16. The forkhead transcription factor FOXP1 represses human plasma cell differentiation.

    PubMed

    van Keimpema, Martine; Grüneberg, Leonie J; Mokry, Michal; van Boxtel, Ruben; van Zelm, Menno C; Coffer, Paul; Pals, Steven T; Spaargaren, Marcel

    2015-10-29

    Expression of the forkhead transcription factor FOXP1 is essential for early B-cell development, whereas downregulation of FOXP1 at the germinal center (GC) stage is required for GC B-cell function. Aberrantly high FOXP1 expression is frequently observed in diffuse large B-cell lymphoma and mucosa-associated lymphoid tissue lymphoma, being associated with poor prognosis. Here, by gene expression analysis upon ectopic overexpression of FOXP1 in primary human memory B cells (MBCs) and B-cell lines, combined with chromatin immunoprecipitation and sequencing, we established that FOXP1 directly represses expression of PRDM1, IRF4, and XBP1, transcriptional master regulators of plasma cell (PC) differentiation. In accordance, FOXP1 is prominently expressed in primary human naive and MBCs, but expression strongly decreases during PC differentiation. Moreover, as compared with immunoglobulin (Ig) M(+) MBCs, IgG(+) MBCs combine lower expression of FOXP1 with an enhanced intrinsic PC differentiation propensity, and constitutive (over)expression of FOXP1 in B-cell lines and primary human MBCs represses their ability to differentiate into PCs. Taken together, our data indicate that proper control of FOXP1 expression plays a critical role in PC differentiation, whereas aberrant expression of FOXP1 might contribute to lymphomagenesis by blocking this terminal B-cell differentiation. PMID:26289642

  17. I-mfa domain proteins specifically interact with HTLV-1 Tax and repress its transactivating functions.

    PubMed

    Kusano, Shuichi; Yoshimitsu, Makoto; Hachiman, Miho; Ikeda, Masanori

    2015-12-01

    The I-mfa domain proteins HIC (also known as MDFIC) and I-mfa (also known as MDFI) are candidate tumor suppressor genes that are involved in cellular and viral transcriptional regulation. Here, we show that HIC and I-mfa directly interact with human T-cell leukemia virus type-1 (HTLV-1) Tax protein in vitro. In addition, HIC and I-mfa repress Tax-dependent transactivation of an HTLV-1 long terminal repeat (LTR) reporter construct in COS-1, Jurkat and high-Tax-producing HTLV-1-infected T cells. HIC also interacts with Tax through its I-mfa domain in vivo and represses Tax-dependent transactivation of HTLV-1 LTR and NF-κB reporter constructs in an interaction-dependent manner. Furthermore, we show that HIC decreases the nuclear distribution and stimulates the proteasomal degradation of Tax. These data reveal that HIC specifically interacts with HTLV-1 Tax and negatively regulates Tax transactivational activity by altering its subcellular distribution and stability.

  18. TET2 repression by androgen hormone regulates global hydroxymethylation status and prostate cancer progression.

    PubMed

    Takayama, Ken-ichi; Misawa, Aya; Suzuki, Takashi; Takagi, Kiyoshi; Hayashizaki, Yoshihide; Fujimura, Tetsuya; Homma, Yukio; Takahashi, Satoru; Urano, Tomohiko; Inoue, Satoshi

    2015-09-25

    Modulation of epigenetic patterns has promising efficacy for treating cancer. 5-Hydroxymethylated cytosine (5-hmC) is an epigenetic mark potentially important in cancer. Here we report that 5-hmC is an epigenetic hallmark of prostate cancer (PCa) progression. A member of the ten-eleven translocation (TET) proteins, which catalyse the oxidation of methylated cytosine (5-mC) to 5-hmC, TET2, is repressed by androgens in PCa. Androgen receptor (AR)-mediated induction of the miR-29 family, which targets TET2, are markedly enhanced in hormone refractory PCa (HRPC) and its high expression predicts poor outcome of PCa patients. Furthermore, decreased expression of miR-29b results in reduced tumour growth and increased TET2 expression in an animal model of HRPC. Interestingly, global 5-hmC modification regulated by miR-29b represses FOXA1 activity. A reduction in 5-hmC activates PCa-related key pathways such as mTOR and AR. Thus, DNA modification directly links the TET2-dependent epigenetic pathway regulated by AR to 5-hmC-mediated tumour progression.

  19. The Costimulatory Receptor OX40 Inhibits Interleukin-17 Expression through Activation of Repressive Chromatin Remodeling Pathways.

    PubMed

    Xiao, Xiang; Shi, Xiaomin; Fan, Yihui; Wu, Chenglin; Zhang, Xiaolong; Minze, Laurie; Liu, Wentao; Ghobrial, Rafik M; Lan, Peixiang; Li, Xian Chang

    2016-06-21

    T helper 17 (Th17) cells are prominently featured in multiple autoimmune diseases, but the regulatory mechanisms that control Th17 cell responses are poorly defined. Here we found that stimulation of OX40 triggered a robust chromatin remodeling response and produced a "closed" chromatin structure at interleukin-17 (IL-17) locus to inhibit Th17 cell function. OX40 activated the NF-κB family member RelB, and RelB recruited the histone methyltransferases G9a and SETDB1 to the Il17 locus to deposit "repressive" chromatin marks at H3K9 sites, and consequently repressing IL-17 expression. Unlike its transcriptional activities, RelB acted independently of both p52 and p50 in the suppression of IL-17. In an experimental autoimmune encephalomyelitis (EAE) disease model, we found that OX40 stimulation inhibited IL-17 and reduced EAE. Conversely, RelB-deficient CD4(+) T cells showed enhanced IL-17 induction and exacerbated the disease. Our data uncover a mechanism in the control of Th17 cells that might have important clinic implications. PMID:27317259

  20. Cell type-specific translational repression of Cyclin B during meiosis in males.

    PubMed

    Baker, Catherine Craig; Gim, Byung Soo; Fuller, Margaret T

    2015-10-01

    The unique cell cycle dynamics of meiosis are controlled by layers of regulation imposed on core mitotic cell cycle machinery components by the program of germ cell development. Although the mechanisms that regulate Cdk1/Cyclin B activity in meiosis in oocytes have been well studied, little is known about the trans-acting factors responsible for developmental control of these factors in male gametogenesis. During meiotic prophase in Drosophila males, transcript for the core cell cycle protein Cyclin B1 (CycB) is expressed in spermatocytes, but the protein does not accumulate in spermatocytes until just before the meiotic divisions. Here, we show that two interacting proteins, Rbp4 and Fest, expressed at the onset of spermatocyte differentiation under control of the developmental program of male gametogenesis, function to direct cell type- and stage-specific repression of translation of the core G2/M cell cycle component cycB during the specialized cell cycle of male meiosis. Binding of Fest to Rbp4 requires a 31-amino acid region within Rbp4. Rbp4 and Fest are required for translational repression of cycB in immature spermatocytes, with Rbp4 binding sequences in a cell type-specific shortened form of the cycB 3' UTR. Finally, we show that Fest is required for proper execution of meiosis I.

  1. Role of RUNX family members in transcriptional repression and gene silencing.

    PubMed

    Durst, Kristie L; Hiebert, Scott W

    2004-05-24

    RUNX family members are DNA-binding transcription factors that regulate the expression of genes involved in cellular differentiation and cell cycle progression. The RUNX family includes three mammalian RUNX proteins (RUNX1, -2, -3) and two homologues in Drosophila. Experiments in Drosophila and mouse indicate that the RUNX proteins are required for gene silencing of engrailed and CD4, respectively. RUNX-mediated repression involves recruitment of corepressors such as mSin3A and Groucho as well as histone deacetylases. Furthermore, RUNX1 and RUNX3 associate with SUV39H1, a histone methyltransferase involved in gene silencing. RUNX1 is frequently targeted in human leukemia by chromosomal translocations that fuse the DNA-binding domain of RUNX1 to other transcription factors and corepressor molecules. The resulting leukemogenic fusion proteins are transcriptional repressors that form stable complexes with corepressors, histone deacetylases and histone methyltransferases. Thus, transcriptional repression and gene silencing through RUNX1 contribute to the mechanisms of leukemogenesis of the fusion proteins. Therapies directed at the associated cofactors may be beneficial for treatment of these leukemias. PMID:15156176

  2. miR-9a prevents apoptosis during wing development by repressing Drosophila LIM-only.

    PubMed

    Bejarano, Fernando; Smibert, Peter; Lai, Eric C

    2010-02-01

    Loss of Drosophila mir-9a induces a subtle increase in sensory bristles, but a substantial loss of wing tissue. Here, we establish that the latter phenotype is largely due to ectopic apoptosis in the dorsal wing primordium, and we could rescue wing development in the absence of this microRNA by dorsal-specific inhibition of apoptosis. Such apoptosis was a consequence of de-repressing Drosophila LIM-only (dLMO), which encodes a transcriptional regulator of wing and neural development. We observed cell-autonomous elevation of endogenous dLMO and a GFP-dLMO 3'UTR sensor in mir-9a mutant wing clones, and heterozygosity for dLMO rescued the apoptosis and wing defects of mir-9a mutants. We also provide evidence that dLMO, in addition to senseless, contributes to the bristle defects of the mir-9a mutant. Unexpectedly, the upregulation of dLMO, loss of Cut, and adult wing margin defects seen with mir-9a mutant clones were not recapitulated by clonal loss of the miRNA biogenesis factors Dicer-1 or Pasha, even though these mutant conditions similarly de-repressed miR-9a and dLMO sensor transgenes. Therefore, the failure to observe a phenotype upon conditional knockout of a miRNA processing factor does not reliably indicate the lack of critical roles of miRNAs in a given setting.

  3. Yeast nitrogen catabolite repression is sustained by signals distinct from glutamine and glutamate reservoirs.

    PubMed

    Fayyad-Kazan, Mohammad; Feller, A; Bodo, E; Boeckstaens, M; Marini, A M; Dubois, E; Georis, I

    2016-01-01

    Nitrogen catabolite repression (NCR) is a wide transcriptional regulation program enabling baker's yeast to downregulate genes involved in the utilization of poor nitrogen sources when preferred ones are available. Nowadays, glutamine and glutamate, the major nitrogen donors for biosyntheses, are assumed to be key metabolic signals regulating NCR. NCR is controlled by the conserved TORC1 complex, which integrates nitrogen signals among others to regulate cell growth. However, accumulating evidence indicate that the TORC1-mediated control of NCR is only partial, arguing for the existence of supplementary regulatory processes to be discovered. In this work, we developed a genetic screen to search for new players involved in NCR signaling. Our data reveal that the NADP-glutamate dehydrogenase activity of Gdh1 negatively regulates NCR-sensitive gene transcription. By determining the total, cytoplasmic and vacuolar pools of amino acids, we show that there is no positive correlation between glutamine/glutamate reservoirs and the extent of NCR. While our data indicate that glutamine could serve as initial trigger of NCR, they show that it is not a sufficient signal to sustain repression and point to the existence of yet unknown signals. Providing additional evidence uncoupling TORC1 activity and NCR, our work revisits the dogmas underlying NCR regulation. PMID:26419331

  4. Repression of the heat shock response is a programmed event at the onset of reproduction

    PubMed Central

    Labbadia, Johnathan; Morimoto, Richard I

    2015-01-01

    Summary The heat shock response (HSR) is essential for proteostasis and cellular health. In metazoans, aging is associated with a decline in quality control, thus increasing the risk for protein conformational disease. Here, we show that in C. elegans, the HSR declines precipitously over a four hour period in early adulthood coincident with the onset of reproductive maturity. Repression of the HSR occurs due to an increase in H3K27me3 marks at stress gene loci, the timing of which is determined by reduced expression of the H3K27 demethylase jmjd-3.1. This results in a repressed chromatin state that interferes with HSF-1 binding and suppresses transcription initiation in response to stress. The removal of germ line stem cells preserves jmjd-3.1 expression, suppresses the accumulation of H3K27me3 at stress gene loci and maintains the HSR. These findings suggest that competing requirements of the germ line and soma dictate organismal stress resistance as animals begin reproduction. PMID:26212459

  5. The SWI/SNF chromatin remodeling complex regulates germinal center formation by repressing Blimp-1 expression.

    PubMed

    Choi, Jinwook; Jeon, Shin; Choi, Seungjin; Park, Kyungsoo; Seong, Rho Hyun

    2015-02-17

    Germinal center (GC) reaction is crucial in adaptive immune responses. The formation of GC is coordinated by the expression of specific genes including Blimp-1 and Bcl-6. Although gene expression is critically influenced by the status of chromatin structure, little is known about the role of chromatin remodeling factors for regulation of GC formation. Here, we show that the SWI/SNF chromatin remodeling complex is required for GC reactions. Mice lacking Srg3/mBaf155, a core component of the SWI/SNF complex, showed impaired differentiation of GC B and follicular helper T cells in response to T cell-dependent antigen challenge. The SWI/SNF complex regulates chromatin structure at the Blimp-1 locus and represses its expression by interacting cooperatively with Bcl-6 and corepressors. The defect in GC reactions in mice lacking Srg3 was due to the derepression of Blimp-1 as supported by genetic studies with Blimp-1-ablated mice. Hence, our study identifies the SWI/SNF complex as a key mediator in GC reactions by modulating Bcl-6-dependent Blimp-1 repression.

  6. E3 ubiquitin ligase RNF31 cooperates with DAX-1 in transcriptional repression of steroidogenesis.

    PubMed

    Ehrlund, Anna; Anthonisen, Elin Holter; Gustafsson, Nina; Venteclef, Nicolas; Robertson Remen, Kirsten; Damdimopoulos, Anastasios E; Galeeva, Anastasia; Pelto-Huikko, Markku; Lalli, Enzo; Steffensen, Knut R; Gustafsson, Jan-Ake; Treuter, Eckardt

    2009-04-01

    Genetic and experimental evidence points to a critical involvement of the atypical mammalian orphan receptor DAX-1 in reproductive development and steroidogenesis. Unlike conventional nuclear receptors, DAX-1 appears not to function as a DNA-bound transcription factor. Instead, it has acquired the capability to act as a transcriptional corepressor of steroidogenic factor 1 (SF-1). The interplay of DAX-1 and SF-1 is considered a central, presumably ligand-independent element of adrenogonadal development and function that requires tight regulation. This raises a substantial interest in identifying its modulators and the regulatory signals involved. Here, we uncover molecular mechanisms that link DAX-1 to the ubiquitin modification system via functional interaction with the E3 ubiquitin ligase RNF31. We demonstrate that RNF31 is coexpressed with DAX-1 in steroidogenic tissues and participates in repressing steroidogenic gene expression. We provide evidence for the in vivo existence of a corepressor complex containing RNF31 and DAX-1 at the promoters of the StAR and CYP19 genes. Our data suggest that RNF31 functions to stabilize DAX-1, which might be linked to DAX-1 monoubiquitination. In conclusion, RNF31 appears to be required for DAX-1 to repress transcription, provides means to regulate DAX-1 in ligand-independent ways, and emerges as a relevant coregulator of steroidogenic pathways governing physiology and disease. PMID:19237537

  7. A Cell-Autonomous Molecular Cascade Initiated by AMP-Activated Protein Kinase Represses Steroidogenesis

    PubMed Central

    Abdou, Houssein S.; Bergeron, Francis

    2014-01-01

    Steroid hormones regulate essential physiological processes, and inadequate levels are associated with various pathological conditions. In testosterone-producing Leydig cells, steroidogenesis is strongly stimulated by luteinizing hormone (LH) via its receptor leading to increased cyclic AMP (cAMP) production and expression of the steroidogenic acute regulatory (STAR) protein, which is essential for the initiation of steroidogenesis. Steroidogenesis then passively decreases with the degradation of cAMP into AMP by phosphodiesterases. In this study, we show that AMP-activated protein kinase (AMPK) is activated following cAMP-to-AMP breakdown in MA-10 and MLTC-1 Leydig cells. Activated AMPK then actively inhibits cAMP-induced steroidogenesis by repressing the expression of key regulators of steroidogenesis, including Star and Nr4a1. Similar results were obtained in Y-1 adrenal cells and in the constitutively steroidogenic R2C cells. We have also determined that maximum AMPK activation following stimulation of steroidogenesis in MA-10 Leydig cells occurs when steroid hormone production has reached a plateau. Our data identify AMPK as a molecular rheostat that actively represses steroid hormone biosynthesis to preserve cellular energy homeostasis and prevent excess steroid production. PMID:25225331

  8. CHES1/FOXN3 regulates cell proliferation by repressing PIM2 and protein biosynthesis.

    PubMed

    Huot, Geneviève; Vernier, Mathieu; Bourdeau, Véronique; Doucet, Laurent; Saint-Germain, Emmanuelle; Gaumont-Leclerc, Marie-France; Moro, Alejandro; Ferbeyre, Gerardo

    2014-03-01

    The expression of the forkhead transcription factor checkpoint suppressor 1 (CHES1), also known as FOXN3, is reduced in many types of cancers. We show here that CHES1 decreases protein synthesis and cell proliferation in tumor cell lines but not in normal fibroblasts. Conversely, short hairpin RNA-mediated depletion of CHES1 increases tumor cell proliferation. Growth suppression depends on the CHES1 forkhead DNA-binding domain and correlates with the nuclear localization of CHES1. CHES1 represses the expression of multiple genes, including the kinases PIM2 and DYRK3, which regulate protein biosynthesis, and a number of genes in cilium biogenesis. CHES1 binds directly to the promoter of PIM2, and in cells expressing CHES1 the levels of PIM2 are reduced, as well as the phosphorylation of the PIM2 target 4EBP1. Overexpression of PIM2 or eIF4E partially reverses the antiproliferative effect of CHES1, indicating that PIM2 and protein biosynthesis are important targets of the antiproliferative effect of CHES1. In several human hematopoietic cancers, CHES1 and PIM2 expressions are inversely correlated, suggesting that repression of PIM2 by CHES1 is clinically relevant. PMID:24403608

  9. Coordinate Transcriptional and Translational Repression of p53 by TGFβ1 Impairs the Stress Response

    PubMed Central

    López-Díaz, Fernando J.; Gascard, Philippe; Balakrishnan, Sri Kripa; Zhao, Jianxin; del Rincon, Sonia V.; Spruck, Charles; Tlsty, Thea D.; Emerson, Beverly M.

    2013-01-01

    Summary Cellular stress results in profound changes in RNA and protein synthesis. How cells integrate this intrinsic, p53-centered program with extracellular signals is largely unknown. We demonstrate that TGFβ1 signaling interferes with the stress response through coordinate transcriptional and translational repression of p53 levels, which reduces p53-activated transcription, and apoptosis in precancerous cells. Mechanistically, E2F4 binds constitutively to the TP53 gene and induces transcription. TGFβ1-activated Smads are recruited to a composite Smad/E2F4 element by an E2F4/p107 complex that switches to a Smad co-repressor, which represses TP53 transcription. TGFβ1 also causes dissociation of ribosomal protein RPL26 and elongation factor eEF1A from p53 mRNA, thereby reducing p53 mRNA association with polyribosomes and p53 translation. TGFβ1-signalling is dominant over stress-induced transcription and translation of p53 and prevents stress-imposed downregulation of Smad proteins. Thus, crosstalk between the TGFβ and p53 pathways defines a major node of regulation in the cellular stress response, enhancing drug resistance. PMID:23706820

  10. Epigenetic Repression of PDZ-LIM Domain-containing Protein 2

    PubMed Central

    Qu, Zhaoxia; Fu, Jing; Yan, Pengrong; Hu, Jing; Cheng, Shi-Yuan; Xiao, Gutian

    2010-01-01

    The NF-κB transcription factor plays a pivotal role in breast cancer progression and therapy resistance. However, the mechanisms by which the tightly regulated NF-κB becomes constitutively activated during breast cancer pathogenesis remain obscure. Here, we report that PDZ-LIM domain-containing protein 2 (PDLIM2), an essential terminator of NF-κB activation, is repressed in both estrogen receptor-positive and estrogen receptor-negative breast cancer cells, suggesting one important mechanism for the constitutive activation of NF-κB. Indeed, PDLIM2 reexpression inhibited constitutive NF-κB activation and expression of NF-κB-targeted genes in those breast cancer cells. Importantly, PDLIM2, but not its mutants defective in NF-κB termination, could suppress in vitro anchorage-independent growth and in vivo tumor formation of those malignant breast cells. In addition, we have shown that PDLIM2 repression involves promoter methylation. Accordingly, treatment of the breast cancer cells with the DNA methyltransferase inhibitor 5-aza-2′-deoxycytidine reverses the methylation of the PDLIM2 promoter, restored PDLIM2 expression, and suppressed tumorigenicities of human breast cancer cells both in vitro and in vivo. These studies thus provide important mechanistic insights into breast cancer pathogenesis. These studies also suggest a tumor suppression function of PDLIM2 and a therapeutic strategy for breast cancer. PMID:20185823

  11. The forkhead transcription factor FOXP1 represses human plasma cell differentiation

    PubMed Central

    van Keimpema, Martine; Grüneberg, Leonie J.; Mokry, Michal; van Boxtel, Ruben; van Zelm, Menno C.; Coffer, Paul; Pals, Steven T.

    2015-01-01

    Expression of the forkhead transcription factor FOXP1 is essential for early B-cell development, whereas downregulation of FOXP1 at the germinal center (GC) stage is required for GC B-cell function. Aberrantly high FOXP1 expression is frequently observed in diffuse large B-cell lymphoma and mucosa-associated lymphoid tissue lymphoma, being associated with poor prognosis. Here, by gene expression analysis upon ectopic overexpression of FOXP1 in primary human memory B cells (MBCs) and B-cell lines, combined with chromatin immunoprecipitation and sequencing, we established that FOXP1 directly represses expression of PRDM1, IRF4, and XBP1, transcriptional master regulators of plasma cell (PC) differentiation. In accordance, FOXP1 is prominently expressed in primary human naive and MBCs, but expression strongly decreases during PC differentiation. Moreover, as compared with immunoglobulin (Ig) M+ MBCs, IgG+ MBCs combine lower expression of FOXP1 with an enhanced intrinsic PC differentiation propensity, and constitutive (over)expression of FOXP1 in B-cell lines and primary human MBCs represses their ability to differentiate into PCs. Taken together, our data indicate that proper control of FOXP1 expression plays a critical role in PC differentiation, whereas aberrant expression of FOXP1 might contribute to lymphomagenesis by blocking this terminal B-cell differentiation. PMID:26289642

  12. DEWAX-mediated transcriptional repression of cuticular wax biosynthesis in Arabidopsis thaliana.

    PubMed

    Suh, Mi Chung; Go, Young Sam

    2014-06-06

    The aerial parts of plants are covered with a cuticular wax layer, which is the first barrier between a plant and its environment. Although cuticular wax deposition increases more in the light than in the dark, little is known about the molecular mechanisms underlying the regulation of cuticular wax biosynthesis. Recently DEWAX (Decrease Wax Biosynthesis) encoding an AP2/ERF transcription factor was found to be preferentially expressed in the epidermis and induced by darkness. Wax analysis of the dewax knockout mutant, wild type, and DEWAX overexpression lines (OX) indicates that DEWAX is a negative regulator of cuticular wax biosynthesis. DEWAX represses the expression of wax biosynthetic genes CER1, LACS2, ACLA2, and ECR via direct interaction with their promoters. Cuticular wax biosynthesis is negatively regulated twice a day by the expression of DEWAX; throughout the night and another for stomata closing. Taken together, it is evident that DEWAX-mediated negative regulation of the wax biosynthetic genes plays role in determining the total wax loads produced in Arabidopsis during daily dark and light cycles. In addition, significantly higher levels of DEWAX transcripts in leaves than stems suggest that DEWAX-mediated transcriptional repression might be involved in the organ-specific regulation of total wax amounts on plant surfaces.

  13. JARID2 regulates binding of the Polycomb repressive complex 2 to target genes in ES cells.

    PubMed

    Pasini, Diego; Cloos, Paul A C; Walfridsson, Julian; Olsson, Linda; Bukowski, John-Paul; Johansen, Jens V; Bak, Mads; Tommerup, Niels; Rappsilber, Juri; Helin, Kristian

    2010-03-11

    The Polycomb group (PcG) proteins have an important role in controlling the expression of genes essential for development, differentiation and maintenance of cell fates. The Polycomb repressive complex 2 (PRC2) is believed to regulate transcriptional repression by catalysing the di- and tri-methylation of lysine 27 on histone H3 (H3K27me2/3). At present, it is unknown how the PcG proteins are recruited to their target promoters in mammalian cells. Here we show that PRC2 forms a stable complex with the Jumonji- and ARID-domain-containing protein, JARID2 (ref. 4). Using genome-wide location analysis, we show that JARID2 binds to more than 90% of previously mapped PcG target genes. Notably, we show that JARID2 is sufficient to recruit PcG proteins to a heterologous promoter, and that inhibition of JARID2 expression leads to a major loss of PcG binding and to a reduction of H3K27me3 levels on target genes. Consistent with an essential role for PcG proteins in early development, we demonstrate that JARID2 is required for the differentiation of mouse embryonic stem cells. Thus, these results demonstrate that JARID2 is essential for the binding of PcG proteins to target genes and, consistent with this, for the proper differentiation of embryonic stem cells and normal development.

  14. Polycomb repressive complex PRC1 spatially constrains the mouse embryonic stem cell genome

    PubMed Central

    Mifsud, Borbala; Dimitrova, Emilia; Matheson, Louise; Tavares-Cadete, Filipe; Furlan-Magaril, Mayra; Segonds-Pichon, Anne; Jurkowski, Wiktor; Wingett, Steven W.; Tabbada, Kristina; Andrews, Simon; Herman, Bram; LeProust, Emily; Osborne, Cameron S.; Koseki, Haruhiko; Fraser, Peter; Luscombe, Nicholas M.; Elderkin, Sarah

    2016-01-01

    The Polycomb Repressive Complexes PRC1 and PRC2 maintain embryonic stem cell (ESC) pluripotency by silencing lineage-specifying developmental regulator genes1. Emerging evidence suggests that Polycomb complexes act through controlling spatial genome organisation2–9. We show that PRC1 functions as a master regulator of ESC genome architecture by organizing genes in three-dimensional interaction networks. The strongest spatial network is composed of the four Hox clusters and early developmental transcription factor genes, the majority of which contact poised enhancers. Removal of Polycomb repression leads to disruption of promoter-promoter contacts in the Hox network. In contrast, promoter-enhancer contacts are maintained, accompanied by widespread acquisition of active chromatin signatures at network enhancers and pronounced transcriptional up-regulation of network genes. Thus, PRC1 physically constrains developmental transcription factor genes and their enhancers in a silenced but poised spatial network. We propose that selective release of genes from this spatial network underlies cell fate specification during early embryonic development. PMID:26323060

  15. Identification of novel secreted fatty acids that regulate nitrogen catabolite repression in fission yeast

    PubMed Central

    Sun, Xiaoying; Hirai, Go; Ueki, Masashi; Hirota, Hiroshi; Wang, Qianqian; Hongo, Yayoi; Nakamura, Takemichi; Hitora, Yuki; Takahashi, Hidekazu; Sodeoka, Mikiko; Osada, Hiroyuki; Hamamoto, Makiko; Yoshida, Minoru; Yashiroda, Yoko

    2016-01-01

    Uptake of poor nitrogen sources such as branched-chain amino acids is repressed in the presence of high-quality nitrogen sources such as NH4+ and glutamate (Glu), which is called nitrogen catabolite repression. Amino acid auxotrophic mutants of the fission yeast Schizosaccharomyces pombe were unable to grow on minimal medium containing NH4Cl or Glu even when adequate amounts of required amino acids were supplied. However, growth of these mutant cells was recovered in the vicinity of colonies of the prototrophic strain, suggesting that the prototrophic cells secrete some substances that can restore uptake of amino acids by an unknown mechanism. We identified the novel fatty acids, 10(R)-acetoxy-8(Z)-octadecenoic acid and 10(R)-hydroxy-8(Z)-octadecenoic acid, as secreted active substances, referred to as Nitrogen Signaling Factors (NSFs). Synthetic NSFs were also able to shift nitrogen source utilization from high-quality to poor nitrogen sources to allow adaptive growth of the fission yeast amino acid auxotrophic mutants in the presence of high-quality nitrogen sources. Finally, we demonstrated that the Agp3 amino acid transporter was involved in the adaptive growth. The data highlight a novel intra-species communication system for adaptation to environmental nutritional conditions in fission yeast. PMID:26892493

  16. Identification of novel secreted fatty acids that regulate nitrogen catabolite repression in fission yeast.

    PubMed

    Sun, Xiaoying; Hirai, Go; Ueki, Masashi; Hirota, Hiroshi; Wang, Qianqian; Hongo, Yayoi; Nakamura, Takemichi; Hitora, Yuki; Takahashi, Hidekazu; Sodeoka, Mikiko; Osada, Hiroyuki; Hamamoto, Makiko; Yoshida, Minoru; Yashiroda, Yoko

    2016-02-19

    Uptake of poor nitrogen sources such as branched-chain amino acids is repressed in the presence of high-quality nitrogen sources such as NH4(+) and glutamate (Glu), which is called nitrogen catabolite repression. Amino acid auxotrophic mutants of the fission yeast Schizosaccharomyces pombe were unable to grow on minimal medium containing NH4Cl or Glu even when adequate amounts of required amino acids were supplied. However, growth of these mutant cells was recovered in the vicinity of colonies of the prototrophic strain, suggesting that the prototrophic cells secrete some substances that can restore uptake of amino acids by an unknown mechanism. We identified the novel fatty acids, 10(R)-acetoxy-8(Z)-octadecenoic acid and 10(R)-hydroxy-8(Z)-octadecenoic acid, as secreted active substances, referred to as Nitrogen Signaling Factors (NSFs). Synthetic NSFs were also able to shift nitrogen source utilization from high-quality to poor nitrogen sources to allow adaptive growth of the fission yeast amino acid auxotrophic mutants in the presence of high-quality nitrogen sources. Finally, we demonstrated that the Agp3 amino acid transporter was involved in the adaptive growth. The data highlight a novel intra-species communication system for adaptation to environmental nutritional conditions in fission yeast.

  17. A role for repressive histone methylation in cocaine-induced vulnerability to stress

    PubMed Central

    Covington, Herbert E.; Maze, Ian; Sun, HaoSheng; Bomze, Howard M.; DeMaio, Kristine D.; Wu, Emma Y.; Dietz, David M.; Lobo, Mary Kay; Ghose, Subroto; Mouzon, Ezekiel; Neve, Rachael L.; Tamminga, Carol A.; Nestler, Eric J.

    2011-01-01

    SUMMARY Substance abuse increases an individual's vulnerability to stress-related illnesses, which is presumably mediated by drug-induced neural adaptations that alter subsequent responses to stress. Here, we identify repressive histone methylation in nucleus accumbens (NAc), an important brain reward region, as a key mechanism linking cocaine exposure to increased stress vulnerability. Repeated cocaine administration prior to chronic social defeat stress potentiated depressive-like behaviors in mice through decreased levels of histone H3 lysine 9 dimethylation in NAc. Cre-mediated reduction of the histone methyltransferase, G9a, in NAc promoted increased susceptibility to social stress, similar to that observed with repeated cocaine. Conversely, G9a overexpression in NAc after repeated cocaine protected mice from the consequences of subsequent stress. This resilience was mediated, in part, through repression of BDNF-TrkB-CREB signaling, which was induced after repeated cocaine or stress. Identifying such common regulatory mechanisms may aid in the development of new therapies for addiction and depression. PMID:21867882

  18. TQ inhibits hepatocellular carcinoma growth in vitro and in vivo via repression of Notch signaling

    PubMed Central

    Ke, Xiquan; Zhao, Yan; Lu, Xinlan; Wang, Zhe; Liu, Yuanyuan; Ren, Mudan; Lu, Guifang; Zhang, Dan; Sun, Zhenguo; Xu, Zhipeng; Song, Jee Hoon; Cheng, Yulan; Meltzer, Stephen J.; He, Shuixiang

    2015-01-01

    Thymoquinone (TQ) has been reported to possess anti-tumor activity in various types of cancer. However, its effects and molecular mechanism of action in hepatocellular carcinoma (HCC) are still not completely understood. We observed that TQ inhibited tumor cell growth in vitro, where treatment with TQ arrested the cell cycle in G1 by upregulating p21 and downregulating cyclinD1 and CDK2 expression; moreover, TQ induced apoptosis by decreasing expression of Bcl-2 and increasing expression of Bax. Simultaneously, TQ demonstrated a suppressive impact on the Notch pathway, where overexpression of NICD1 reversed the inhibitory effect of TQ on cell proliferation, thereby attenuating the repressive effects of TQ on the Notch pathway, cyclinD1, CDK2 and Bcl-2, and also diminishing upregulation of p21 and Bax. In a xenograft model, TQ inhibited HCC growth in nude mice; this inhibitory effect in vivo, as well as of HCC cell growth in vitro, was associated with a discernible decline in NICD1 and Bcl-2 levels and a dramatic rise in p21 expression. In conclusion, TQ inhibits HCC cell growth by inducing cell cycle arrest and apoptosis, achieving these effects by repression of the Notch signaling pathway, suggesting that TQ represents a potential preventive or therapeutic agent in HCC patients. PMID:26416455

  19. Melanie Klein and Repression: an examination of some unpublished Notes of 1934.

    PubMed

    Hinshelwood, R D

    2006-01-01

    Fifteen pages of unpublished Notes were found in the Melanie Klein Archives dating from early 1934, a crucial moment in Klein's development. She was at this time, 1934, moving away from child analysis, whilst also rethinking and revising her allegiance to Karl Abraham's theory of the phases of libidinal development. These Notes, entitled "Early Repression Mechanism," show Klein struggling to develop what became her characteristic theories of the depressive position and the paranoid-schizoid position. Although these Notes are precursors of the paper Klein gave later to the IPA Congress in 1934, they also show the origins of the emphasis she and her followers eventually gave to "splitting" rather than repression. The Notes give us an insight into the way that she worked clinically at the time. We see Klein's confidence develop as she diverged from the classical theories and technique. Her ideas were based on close attention to the detail of her clinical material, rather than attacking theoretical problems directly. The Notes show her method of struggling to her own conclusions, and they offer us a chance to grasp the roots of the subsequent controversy over Kleinian thought. PMID:19771670

  20. The T-box transcription factor Midline regulates wing development by repressing wingless and hedgehog in Drosophila

    PubMed Central

    Fu, Chong-Lei; Wang, Xian-Feng; Cheng, Qian; Wang, Dan; Hirose, Susumu; Liu, Qing-Xin

    2016-01-01

    Wingless (Wg) and Hedgehog (Hh) signaling pathways are key players in animal development. However, regulation of the expression of wg and hh are not well understood. Here, we show that Midline (Mid), an evolutionarily conserved transcription factor, expresses in the wing disc of Drosophila and plays a vital role in wing development. Loss or knock down of mid in the wing disc induced hyper-expression of wingless (wg) and yielded cocked and non-flat wings. Over-expression of mid in the wing disc markedly repressed the expression of wg, DE-Cadherin (DE-Cad) and armadillo (arm), and resulted in a small and blistered wing. In addition, a reduction in the dose of mid enhanced phenotypes of a gain-of-function mutant of hedgehog (hh). We also observed repression of hh upon overexpression of mid in the wing disc. Taken together, we propose that Mid regulates wing development by repressing wg and hh in Drosophila. PMID:27301278

  1. The T-box transcription factor Midline regulates wing development by repressing wingless and hedgehog in Drosophila.

    PubMed

    Fu, Chong-Lei; Wang, Xian-Feng; Cheng, Qian; Wang, Dan; Hirose, Susumu; Liu, Qing-Xin

    2016-01-01

    Wingless (Wg) and Hedgehog (Hh) signaling pathways are key players in animal development. However, regulation of the expression of wg and hh are not well understood. Here, we show that Midline (Mid), an evolutionarily conserved transcription factor, expresses in the wing disc of Drosophila and plays a vital role in wing development. Loss or knock down of mid in the wing disc induced hyper-expression of wingless (wg) and yielded cocked and non-flat wings. Over-expression of mid in the wing disc markedly repressed the expression of wg, DE-Cadherin (DE-Cad) and armadillo (arm), and resulted in a small and blistered wing. In addition, a reduction in the dose of mid enhanced phenotypes of a gain-of-function mutant of hedgehog (hh). We also observed repression of hh upon overexpression of mid in the wing disc. Taken together, we propose that Mid regulates wing development by repressing wg and hh in Drosophila. PMID:27301278

  2. PIASy, a nuclear matrix–associated SUMO E3 ligase, represses LEF1 activity by sequestration into nuclear bodies

    PubMed Central

    Sachdev, Shrikesh; Bruhn, Laurakay; Sieber, Heidemarie; Pichler, Andrea; Melchior, Frauke; Grosschedl, Rudolf

    2001-01-01

    The Wnt-responsive transcription factor LEF1 can activate transcription in association with β-catenin and repress transcription in association with Groucho. In search of additional regulatory mechanisms of LEF1 function, we identified the protein inhibitor of activated STAT, PIASy, as a novel interaction partner of LEF1. Coexpression of PIASy with LEF1 results in potent repression of LEF1 activity and in covalent modification of LEF1 with SUMO. PIASy markedly stimulates the sumoylation of LEF1 and multiple other proteins in vivo and functions as a SUMO E3 ligase for LEF1 in a reconstituted system in vitro. Moreover, PIASy binds to nuclear matrix–associated DNA sequences and targets LEF1 to nuclear bodies, suggesting that PIASy-mediated subnuclear sequestration accounts for the repression of LEF1 activity. PMID:11731474

  3. The T-box transcription factor Midline regulates wing development by repressing wingless and hedgehog in Drosophila.

    PubMed

    Fu, Chong-Lei; Wang, Xian-Feng; Cheng, Qian; Wang, Dan; Hirose, Susumu; Liu, Qing-Xin

    2016-06-15

    Wingless (Wg) and Hedgehog (Hh) signaling pathways are key players in animal development. However, regulation of the expression of wg and hh are not well understood. Here, we show that Midline (Mid), an evolutionarily conserved transcription factor, expresses in the wing disc of Drosophila and plays a vital role in wing development. Loss or knock down of mid in the wing disc induced hyper-expression of wingless (wg) and yielded cocked and non-flat wings. Over-expression of mid in the wing disc markedly repressed the expression of wg, DE-Cadherin (DE-Cad) and armadillo (arm), and resulted in a small and blistered wing. In addition, a reduction in the dose of mid enhanced phenotypes of a gain-of-function mutant of hedgehog (hh). We also observed repression of hh upon overexpression of mid in the wing disc. Taken together, we propose that Mid regulates wing development by repressing wg and hh in Drosophila.

  4. Repression of Essential Chloroplast Genes Reveals New Signaling Pathways and Regulatory Feedback Loops in Chlamydomonas[W

    PubMed Central

    Ramundo, Silvia; Rahire, Michèle; Schaad, Olivier; Rochaix, Jean-David

    2013-01-01

    Although reverse genetics has been used to elucidate the function of numerous chloroplast proteins, the characterization of essential plastid genes and their role in chloroplast biogenesis and cell survival has not yet been achieved. Therefore, we developed a robust repressible chloroplast gene expression system in the unicellular alga Chlamydomonas reinhardtii based mainly on a vitamin-repressible riboswitch, and we used this system to study the role of two essential chloroplast genes: ribosomal protein S12 (rps12), encoding a plastid ribosomal protein, and rpoA, encoding the α-subunit of chloroplast bacterial-like RNA polymerase. Repression of either of these two genes leads to the arrest of cell growth, and it induces a response that involves changes in expression of nuclear genes implicated in chloroplast biogenesis, protein turnover, and stress. This response also leads to the overaccumulation of several plastid transcripts and reveals the existence of multiple negative regulatory feedback loops in the chloroplast gene circuitry. PMID:23292734

  5. Control of inducer accumulation plays a key role in succinate-mediated catabolite repression in Sinorhizobium meliloti.

    PubMed

    Bringhurst, Ryan M; Gage, Daniel J

    2002-10-01

    The symbiotic, nitrogen-fixing bacterium Sinorhizobium meliloti favors succinate and related dicarboxylic acids as carbon sources. As a preferred carbon source, succinate can exert catabolite repression upon genes needed for the utilization of many secondary carbon sources, including the alpha-galactosides raffinose and stachyose. We isolated lacR mutants in a genetic screen designed to find S. meliloti mutants that had abnormal succinate-mediated catabolite repression of the melA-agp genes, which are required for the utilization of raffinose and other alpha-galactosides. The loss of catabolite repression in lacR mutants was seen in cells grown in minimal medium containing succinate and raffinose and grown in succinate and lactose. For succinate and lactose, the loss of catabolite repression could be attributed to the constitutive expression of beta-galactoside utilization genes in lacR mutants. However, the inactivation of lacR did not cause the constitutive expression of alpha-galactoside utilization genes but caused the aberrant expression of these genes only when succinate was present. To explain the loss of diauxie in succinate and raffinose, we propose a model in which lacR mutants overproduce beta-galactoside transporters, thereby overwhelming the inducer exclusion mechanisms of succinate-mediated catabolite repression. Thus, some raffinose could be transported by the overproduced beta-galactoside transporters and cause the induction of alpha-galactoside utilization genes in the presence of both succinate and raffinose. This model is supported by the restoration of diauxie in a lacF lacR double mutant (lacF encodes a beta-galactoside transport protein) grown in medium containing succinate and raffinose. Biochemical support for the idea that succinate-mediated repression operates by preventing inducer accumulation also comes from uptake assays, which showed that cells grown in raffinose and exposed to succinate have a decreased rate of raffinose transport

  6. Transforming Growth Factor-β1 Signaling Represses Testicular Steroidogenesis through Cross-Talk with Orphan Nuclear Receptor Nur77

    PubMed Central

    Park, Eunsook; Song, Chin-Hee; Park, Jae-Il; Ahn, Ryun-Sup; Choi, Hueng-Sik; Ko, CheMyong; Lee, Keesook

    2014-01-01

    Transforming growth factor- β1 (TGF-β1) has been reported to inhibit luteinizing hormone (LH) mediated-steroidogenesis in testicular Leydig cells. However, the mechanism by which TGF-β1 controls the steroidogenesis in Leydig cells is not well understood. Here, we investigated the possibility that TGF-β1 represses steroidogenesis through cross-talk with the orphan nuclear receptor Nur77. Nur77, which is induced by LH/cAMP signaling, is one of major transcription factors that regulate the expression of steroidogenic genes in Leydig cells. TGF-β1 signaling inhibited cAMP-induced testosterone production and the expression of steroidogenic genes such as P450c17, StAR and 3β-HSD in mouse Leydig cells. Further, TGF-β1/ALK5 signaling repressed cAMP-induced and Nur77-activated promoter activity of steroidogenic genes. In addition, TGF-β1/ALK5-activated Smad3 repressed Nur77 transactivation of steroidogenic gene promoters by interfering with Nur77 binding to DNA. In primary Leydig cells isolated from Tgfbr2flox/flox Cyp17iCre mice, TGF-β1-mediated repression of cAMP-induced steroidogenic gene expression was significantly less than that in primary Leydig cells from Tgfbr2flox/flox mice. Taken together, these results suggest that TGF-β1/ALK5/Smad3 signaling represses the expression of steroidogenic genes via the suppression of Nur77 transactivation in testicular Leydig cells. These findings may provide a molecular mechanism involved in the TGF-β1-mediated repression of testicular steroidogenesis. PMID:25140527

  7. Can the Neural Basis of Repression Be Studied in the MRI Scanner? New Insights from Two Free Association Paradigms

    PubMed Central

    Kessler, Henrik; Do Lam, Anne T. A.; Fell, Juergen; Schmidt, Anna-Christine; Axmacher, Nikolai

    2013-01-01

    Background The psychodynamic theory of repression suggests that experiences which are related to internal conflicts become unconscious. Previous attempts to investigate repression experimentally were based on voluntary, intentional suppression of stimulus material. Unconscious repression of conflict-related material is arguably due to different processes, but has never been studied with neuroimaging methods. Methods We used functional magnetic resonance imaging (fMRI) in addition with skin conductance recordings during two free association paradigms to identify the neural mechanisms underlying forgetting of freely associated words according to repression theory. Results In the first experiment, free association to subsequently forgotten words was accompanied by increases in skin conductance responses (SCRs) and reaction times (RTs), indicating autonomic arousal, and by activation of the anterior cingulate cortex. These findings are consistent with the hypothesis that these associations were repressed because they elicited internal conflicts. To test this idea more directly, we conducted a second experiment in which participants freely associated to conflict-related sentences. Indeed, these associations were more likely to be forgotten than associations to not conflict-related sentences and were accompanied by increases in SCRs and RTs. Furthermore, we observed enhanced activation of the anterior cingulate cortex and deactivation of hippocampus and parahippocampal cortex during association to conflict-related sentences. Conclusions These two experiments demonstrate that high autonomic arousal during free association predicts subsequent memory failure, accompanied by increased activation of conflict-related and deactivation of memory-related brain regions. These results are consistent with the hypothesis that during repression, explicit memory systems are down-regulated by the anterior cingulate cortex. PMID:23638050

  8. Repressed ghosts and dissociated vampires in the enacted dimension of psychoanalytic treatment.

    PubMed

    Katz, Gil

    2015-04-01

    One of the most evocative uses of the metaphor of a ghost in psychoanalytic writing was crafted by Hans Loewald in "On the Therapeutic Action of Psycho-Analysis" (1960). In this seminal work, Loewald likened the process of psychoanalytic change to that of transforming psychic ghosts into ancestors. In the present paper, the author supplements the metaphor of ghosts that haunt with the metaphor of vampires that menace, and links these two alien experiences to two psychological processes: repression and dissociation. Descriptions of ghosts and vampires in folklore, and the ways they are experienced in analytic treatment, are followed by an explication of the enacted dimension of analytic process-the arena of treatment in which all demons are inevitably revivified, "recognized," and ultimately laid to rest. The paper includes a clinical illustration of a dissociated vampire: a Holocaust trauma transmitted across three generations of survivors. PMID:25876540

  9. Polycomb repressive complex 2 regulates skeletal growth by suppressing Wnt and TGF-β signalling

    PubMed Central

    Mirzamohammadi, Fatemeh; Papaioannou, Garyfallia; Inloes, Jennifer B.; Rankin, Erinn B.; Xie, Huafeng; Schipani, Ernestina; Orkin, Stuart H.; Kobayashi, Tatsuya

    2016-01-01

    Polycomb repressive complex 2 (PRC2) controls maintenance and lineage determination of stem cells by suppressing genes that regulate cellular differentiation and tissue development. However, the role of PRC2 in lineage-committed somatic cells is mostly unknown. Here we show that Eed deficiency in chondrocytes causes severe kyphosis and a growth defect with decreased chondrocyte proliferation, accelerated hypertrophic differentiation and cell death with reduced Hif1a expression. Eed deficiency also causes induction of multiple signalling pathways in chondrocytes. Wnt signalling overactivation is responsible for the accelerated hypertrophic differentiation and kyphosis, whereas the overactivation of TGF-β signalling is responsible for the reduced proliferation and growth defect. Thus, our study demonstrates that PRC2 has an important regulatory role in lineage-committed tissue cells by suppressing overactivation of multiple signalling pathways. PMID:27329220

  10. Repression versus sensitization in response to media violence as predictors of cognitive avoidance and vigilance.

    PubMed

    Krahé, Barbara; Möller, Ingrid; Berger, Anja; Felber, Juliane

    2011-02-01

    Repression and sensitization as situational modes of coping with anxiety were examined as predictors of trait measures of cognitive avoidance and vigilance. In this study, 303 undergraduates saw a violent film clip to elicit anxiety. Increases in skin conductance level (SCL) and state anxiety (STA) from baseline were measured to identify repressors (high SCL, low STA) and contrast them with sensitizers (low SCL, high STA) and genuinely low anxious individuals (low SCL, low STA). State anger was also recorded. Trait measures of vigilance and cognitive avoidance were collected 2 weeks earlier. Significant SCL × STA interactions indicated that repressors scored higher on cognitive avoidance and lower on vigilance compared to sensitizers and low anxious participants. Repressors were less likely than sensitizers to report gaze avoidance during the clip. The anger by SCL interaction was nonsignificant, suggesting that repressors and sensitizers differ specifically in the processing of anxiety rather than negative affect in general. PMID:21223268

  11. Repressed ghosts and dissociated vampires in the enacted dimension of psychoanalytic treatment.

    PubMed

    Katz, Gil

    2015-04-01

    One of the most evocative uses of the metaphor of a ghost in psychoanalytic writing was crafted by Hans Loewald in "On the Therapeutic Action of Psycho-Analysis" (1960). In this seminal work, Loewald likened the process of psychoanalytic change to that of transforming psychic ghosts into ancestors. In the present paper, the author supplements the metaphor of ghosts that haunt with the metaphor of vampires that menace, and links these two alien experiences to two psychological processes: repression and dissociation. Descriptions of ghosts and vampires in folklore, and the ways they are experienced in analytic treatment, are followed by an explication of the enacted dimension of analytic process-the arena of treatment in which all demons are inevitably revivified, "recognized," and ultimately laid to rest. The paper includes a clinical illustration of a dissociated vampire: a Holocaust trauma transmitted across three generations of survivors.

  12. RNAi mediates post-transcriptional repression of gene expression in fission yeast Schizosaccharomyces pombe.

    PubMed

    Smialowska, Agata; Djupedal, Ingela; Wang, Jingwen; Kylsten, Per; Swoboda, Peter; Ekwall, Karl

    2014-02-01

    RNA interference (RNAi) is a gene silencing mechanism conserved from fungi to mammals. Small interfering RNAs are products and mediators of the RNAi pathway and act as specificity factors in recruiting effector complexes. The Schizosaccharomyces pombe genome encodes one of each of the core RNAi proteins, Dicer, Argonaute and RNA-dependent RNA polymerase (dcr1, ago1, rdp1). Even though the function of RNAi in heterochromatin assembly in S. pombe is established, its role in controlling gene expression is elusive. Here, we report the identification of small RNAs mapped anti-sense to protein coding genes in fission yeast. We demonstrate that these genes are up-regulated at the protein level in RNAi mutants, while their mRNA levels are not significantly changed. We show that the repression by RNAi is not a result of heterochromatin formation. Thus, we conclude that RNAi is involved in post-transcriptional gene silencing in S. pombe.

  13. Repression of In Vivo Synthesis of the Mitochondrial Elongation Factors T and G in Saccharomyces fragilis

    PubMed Central

    Richter, D.

    1973-01-01

    In vivo synthesis of the mitochondrial elongation factors T and G in the yeast Saccharomyces fragilis can be repressed. Enzymatic activity assays and immunochemical titration methods reveal that cells grown in the presence of 8% glucose or in the absence of oxygen contain relatively lower amounts of mitochondrial elongation factors than cells grown in the presence of lactate. In contrast, in vivo production of the cytoplasmic elongation factors 1 and 2 does not respond to such a change of extracellular conditions. The rate of growth does not affect the level of the mitochondrial elongation factors. Production of both enzymes is almost constant during logarithmic growth, but decreases when the stationary phase is reached. Chloramphenicol, an inhibitor of mitochondrial protein synthesis, does not block but, rather, seems to enhance the in vivo synthesis of mitochondrial T or G. PMID:4717524

  14. Long range repression conferring boundaries of Ultrabithorax expression in the Drosophila embryo.

    PubMed Central

    Müller, J; Bienz, M

    1991-01-01

    In an attempt to reconstruct the embryonic expression pattern of the homeotic gene Ultrabithorax (Ubx) by stable integration of fusion constructs, we identified three key control regions called PBX, ABX and BXD. Each of these confers an expression pattern mimicking certain aspects of Ubx expression. The PBX and ABX patterns are limited to the Ubx domain with anterior boundaries at parasegments 6 and 5. In contrast, the BXD pattern extends from head to tail. PBX or ABX expression boundaries are imposed on the BXD pattern, if PBX or ABX is linked to BXD. These boundaries, although not the PBX and ABX expression limits themselves, are dependent on Polycomb function. We conclude that PBX and ABX are recognized by repressors which act across large distances to suppress BXD activity. Stable and heritable Ubx expression boundaries are thus mediated by this process of long range repression. Images PMID:1680676

  15. Deregulated repression of c-Jun provides a potential link to its role in tumorigenesis.

    PubMed

    Weiss, Carsten; Bohmann, Dirk

    2004-02-01

    The transcription factor c-Jun cooperates with oncogenic alleles of ras in malignant transformation. Constitutively active Ras causes, via activation of mitogen activated protein kinases, phosphorylation of c-Jun which is essential for subsequent target gene activation and tumorigenesis. Studying the mechanisms controlling c-Jun activity we found that its transcription activation function is actively repressed by a presumably multimeric repressor complex that includes histone deacetylase 3 as a critical subunit. Suppression of c-Jun is relieved by MAP kinase-mediated phosphorylation and/or titration of inhibitor components. The viral tumorigenic counterpart of c-Jun, v-Jun, escapes this inhibition, suggesting deregulated transcriptional activity of c-Jun as a relevant cause for carcinogenesis.

  16. Evolutionary Design of Choline-Inducible and -Repressible T7-Based Induction Systems.

    PubMed

    Ike, Kohei; Arasawa, Yusuke; Koizumi, Satoshi; Mihashi, Satoshi; Kawai-Noma, Shigeko; Saito, Kyoichi; Umeno, Daisuke

    2015-12-18

    By assembly and evolutionary engineering of T7-phage-based transcriptional switches made from endogenous components of the bet operon on the Escherichia coli chromosome, genetic switches inducible by choline, a safe and inexpensive compound, were constructed. The functional plasticity of the BetI repressor was revealed by rapid and high-frequency identification of functional variants with various properties, including those with high stringency, high maximum expression level, and reversed phenotypes, from a pool of BetI mutants. The plasmid expression of BetI mutants resulted in the choline-inducible (Bet-ON) or choline-repressible (Bet-OFF) switching of genes under the pT7/betO sequence at unprecedentedly high levels, while keeping the minimal leaky expression in uninduced conditions.

  17. Methylation by NSun2 Represses the Levels and Function of MicroRNA 125b

    PubMed Central

    Yuan, Shuai; Tang, Hao; Xing, Junyue; Fan, Xiuqin; Cai, Xiaoyu; Li, Qiu; Han, Pei; Luo, Yuhong; Zhang, Zhuojun; Jiang, Bin; Dou, Yali; Gorospe, Myriam

    2014-01-01

    Methylation is a prevalent posttranscriptional modification of RNAs. However, whether mammalian microRNAs are methylated is unknown. Here, we show that the tRNA methyltransferase NSun2 methylates primary (pri-miR-125b), precursor (pre-miR-125b), and mature microRNA 125b (miR-125b) in vitro and in vivo. Methylation by NSun2 inhibits the processing of pri-miR-125b2 into pre-miR-125b2, decreases the cleavage of pre-miR-125b2 into miR-125, and attenuates the recruitment of RISC by miR-125, thereby repressing the function of miR-125b in silencing gene expression. Our results highlight the impact of miR-125b function via methylation by NSun2. PMID:25047833

  18. ZBTB7A acts as a tumor suppressor through the transcriptional repression of glycolysis

    PubMed Central

    Liu, Xue-Song; Haines, Jenna E.; Mehanna, Elie K.; Genet, Matthew D.; Ben-Sahra, Issam; Asara, John M.; Manning, Brendan D.

    2014-01-01

    Elevated glycolysis is a common metabolic trait of cancer, but what drives such metabolic reprogramming remains incompletely clear. We report here a novel transcriptional repressor-mediated negative regulation of glycolysis. ZBTB7A, a member of the POK (POZ/BTB and Krüppel) transcription repressor family, directly binds to the promoter and represses the transcription of critical glycolytic genes, including GLUT3, PFKP, and PKM. Analysis of The Cancer Genome Atlas (TCGA) data sets reveals that the ZBTB7A locus is frequently deleted in many human tumors. Significantly, reduced ZBTB7A expression correlates with up-regulation of the glycolytic genes and poor survival in colon cancer patients. Remarkably, while ZBTB7A-deficient tumors progress exceedingly fast, they exhibit an unusually heightened sensitivity to glycolysis inhibition. Our study uncovers a novel tumor suppressor role of ZBTB7A in directly suppressing glycolysis. PMID:25184678

  19. Cyclic AMP Can Decrease Expression of Genes Subject to Catabolite Repression in Saccharomyces cerevisiae

    PubMed Central

    Zaragoza, Oscar; Lindley, Chris; Gancedo, Juana M.

    1999-01-01

    External cyclic AMP (cAMP) hindered the derepression of gluconeogenic enzymes in a pde2 mutant of Saccharomyces cerevisiae, but it did not prevent invertase derepression. cAMP reduced nearly 20-fold the transcription driven by upstream activation sequence (UAS1FBP1) from FBP1, encoding fructose-1,6-bisphosphatase; it decreased 2-fold the activation of transcription by UAS2FBP1. Nuclear extracts from cells derepressed in the presence of cAMP were impaired in the formation of specific UASFBP1-protein complexes in band shift experiments. cAMP does not appear to act through the repressing protein Mig1. Control of FBP1 transcription through cAMP is redundant with other regulatory mechanisms. PMID:10198033

  20. Genome editing in butterflies reveals that spalt promotes and Distal-less represses eyespot colour patterns.

    PubMed

    Zhang, Linlin; Reed, Robert D

    2016-01-01

    Butterfly eyespot colour patterns are a key example of how a novel trait can appear in association with the co-option of developmental patterning genes. Little is known, however, about how, or even whether, co-opted genes function in eyespot development. Here we use CRISPR/Cas9 genome editing to determine the roles of two co-opted transcription factors that are expressed during early eyespot determination. We found that deletions in a single gene, spalt, are sufficient to reduce or completely delete eyespot colour patterns, thus demonstrating a positive regulatory role for this gene in eyespot determination. Conversely, and contrary to previous predictions, deletions in Distal-less (Dll) result in an increase in the size and number of eyespots, illustrating a repressive role for this gene in eyespot development. Altogether our results show that the presence, absence and shape of butterfly eyespots can be controlled by the activity of two co-opted transcription factors. PMID:27302525