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Sample records for derivative pentamidine represses

  1. Pentamidine Oral Inhalation

    MedlinePlus

    ... pentamidine.You may develop a cough while using aerosol pentamidine. The cough may be more severe if ... your doctor. Your doctor may suggest slowing the aerosol stream or may prescribe a bronchodilator (medication that ...

  2. 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

  3. 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

  4. Lung deposition of nebulised pentamidine in children.

    PubMed Central

    O'Doherty, M J; Thomas, S H; Gibb, D; Page, C J; Harrington, C; Duggan, C; Nunan, T O; Bateman, N T

    1993-01-01

    BACKGROUND: Nebulised pentamidine is effective for preventing Pneumocystis carinii pneumonia in adults with acquired immunodeficiency syndrome. The nebuliser dose required to produce equivalent lung concentrations of pentamidine in children is unknown. This study was performed to measure pulmonary pentamidine deposition in children and to relate this to age, ventilation pattern, and body size. METHODS: Nebulised pentamidine (50 mg in 6 ml saline) was administered to 12 children (including one with lymphocytic interstitial pneumonitis) and to six adults with human immunodeficiency virus infection using a Respirgard II nebuliser. Technetium-99m labeled colloidal human serum albumin was used as an indirect marker for pentamidine and deposition in the lungs was detected by a gamma camera. RESULTS: Absolute deposition of pentamidine was not related to age, height, weight, spirometry, or ventilation characteristics. Deposition, as a mean (SD) percentage of nebuliser output, was similar in children aged 8-11 years (5.5(2.4)%), teenagers aged 12-15 years (7.2(2.2)%) and adults (7.1(2.6)%). Aerosol concentration within the lungs (% nebuliser output deposited/predicted total lung capacity) was therefore higher in children (1.9(1.5)%/1) and teenagers (1.9(0.7)%/1) than in adults (1.0(0.7%)/1), and was negatively correlated with height (r = -0.69) and weight (r = -0.50). Deposition of aerosol in the region of the large central airways was particularly marked in children. Small reductions in forced expiratory volume in one second and forced vital capacity after treatment did not differ significantly between adults and children and visual analogue scores of subjective adverse effects did not vary with age. CONCLUSIONS: These results suggest that children probably require lower nebuliser pentamidine doses to produce lung pentamidine concentrations equivalent to those found to be effective for preventing P carinii pneumonia in adults using the Respirgard II nebuliser. PMID:8497819

  5. Pentamidine-induced dysglycaemia: experimental models in the rat.

    PubMed

    Assan, R; Assan, D; Delaby, J; Debussche, X; Toublanc, M

    1993-01-01

    In order to analyse further the pathophysiology of pentamidine effects on blood glucose regulation, the following experimental models were established in rats: impairment of the renal function, bile duct ligation, inhibition of the P450 cytochrome enzyme system. In otherwise intact rats, 7.5 mg/day pentamidine was well tolerated whereas doses of 15 mg/day induced severe, relapsing and eventually lethal hypoglycaemia within a few days. Induction of a renal insufficiency of graded severity by treatment with gentamycin, subtotal nephrectomy and total bilateral nephrectomy resulted in repetitive, severe (sometimes lethal) hypoglycaemia, alternating with hyperglycaemia, glucosuria and ketonuria in pentamidine-treated rats (7.5 mg/d). No long-standing insulin-dependent diabetes was observed. In the dysglycemic animals, plasma insulin levels were inappropriate to the concomitant glycaemia; no stimulation was obtained by i.v. glucose. Glucagon levels were higher than normal, suppressible by i.v. glucose, responsive to IV arginine and to hypoglycaemia. Dysglycemic events were more frequent and marked in the rats with the most severe renal functional derangement. They were more frequent in the rats treated with pentamidine mesylate than in those treated with the isethionate salt. Control uremic rats (free of pentamidine) remained euglycaemic. The islets of Langerhans displayed severe vascular congestion and degranulation and necrosis of the B cells, while the non B cells (and particularly the A cells) were intact. Exocrine pancreatitis was occasionally observed in the most severely uremic rats. In contrast with uremic rats, neither surgical ligation of choledocus, nor treatment by P450 cytochrome inhibitors (particularly ketoconazole) precipitated dysglycaemia in the pentamidine-treated rats. These experimental data: 1) strengthen the concept of inappropriate insulin release from pentamidine-lesioned islet B cells due to pentamidine accumulation; 2) indicate a predominant

  6. Pentamidine in Pneumocystis jirovecii prophylaxis in heart transplant recipients.

    PubMed

    Diken, Adem Ilkay; Diken, Ozlem Erçen; Hanedan, Onur; Yılmaz, Seyhan; Ecevit, Ata Niyazi; Erol, Emir; Yalçınkaya, Adnan

    2016-03-24

    Despite advances in transplantation techniques and the quality of post-transplantation care, opportunistic infections remain an important cause of complications. Pneumocystis jirovecii (P. jirovecii) is an opportunistic organism, represents an important cause of infections in heart transplantation patients. Almost 2% to 10% of patients undergoing cardiac transplantation have Pneumocystis pneumonia. Prophylaxis is essential after surgery. Various prophylaxis regimes had been defined in past and have different advantages. Trimethoprim/sulfamethoxazole (TMP/SMX) has a key role in prophylaxis against P. jirovecii. Generally, although TMP/SMX is well tolerated, serious side effects have also been reported during its use. Pentamidine is an alternative prophylaxis agent when TMP/SMX cannot be tolerated by the patient. Structurally, pentamidine is an aromatic diamidine compound with antiprotozoal activity. Since it is not effectively absorbed from the gastrointestinal tract, it is frequently administered via the intravenous route. Pentamidine can alternatively be administered through inhalation at a monthly dose in heart transplant recipients. Although, the efficiency and safety of this drug is well studied in other types of solid organ transplantations, there are only few data about pentamidine usage in heart transplantation. We sought to evaluate evidence-based assessment of the use of pentamidine against P. jirovecii after heart transplantation. PMID:27011917

  7. Pentamidine in Pneumocystis jirovecii prophylaxis in heart transplant recipients

    PubMed Central

    Diken, Adem Ilkay; Diken, Ozlem Erçen; Hanedan, Onur; Yılmaz, Seyhan; Ecevit, Ata Niyazi; Erol, Emir; Yalçınkaya, Adnan

    2016-01-01

    Despite advances in transplantation techniques and the quality of post-transplantation care, opportunistic infections remain an important cause of complications. Pneumocystis jirovecii (P. jirovecii) is an opportunistic organism, represents an important cause of infections in heart transplantation patients. Almost 2% to 10% of patients undergoing cardiac transplantation have Pneumocystis pneumonia. Prophylaxis is essential after surgery. Various prophylaxis regimes had been defined in past and have different advantages. Trimethoprim/sulfamethoxazole (TMP/SMX) has a key role in prophylaxis against P. jirovecii. Generally, although TMP/SMX is well tolerated, serious side effects have also been reported during its use. Pentamidine is an alternative prophylaxis agent when TMP/SMX cannot be tolerated by the patient. Structurally, pentamidine is an aromatic diamidine compound with antiprotozoal activity. Since it is not effectively absorbed from the gastrointestinal tract, it is frequently administered via the intravenous route. Pentamidine can alternatively be administered through inhalation at a monthly dose in heart transplant recipients. Although, the efficiency and safety of this drug is well studied in other types of solid organ transplantations, there are only few data about pentamidine usage in heart transplantation. We sought to evaluate evidence-based assessment of the use of pentamidine against P. jirovecii after heart transplantation. PMID:27011917

  8. p53 Represses the Oncogenic Sno-MiR-28 Derived from a SnoRNA

    PubMed Central

    Yu, Feng; Bracken, Cameron P.; Pillman, Katherine A.; Lawrence, David M.; Goodall, Gregory J.; Callen, David F.; Neilsen, Paul M.

    2015-01-01

    p53 is a master tumour repressor that participates in vast regulatory networks, including feedback loops involving microRNAs (miRNAs) that regulate p53 and that themselves are direct p53 transcriptional targets. We show here that a group of polycistronic miRNA-like non-coding RNAs derived from small nucleolar RNAs (sno-miRNAs) are transcriptionally repressed by p53 through their host gene, SNHG1. The most abundant of these, sno-miR-28, directly targets the p53-stabilizing gene, TAF9B. Collectively, p53, SNHG1, sno-miR-28 and TAF9B form a regulatory loop which affects p53 stability and downstream p53-regulated pathways. In addition, SNHG1, SNORD28 and sno-miR-28 are all significantly upregulated in breast tumours and the overexpression of sno-miR-28 promotes breast epithelial cell proliferation. This research has broadened our knowledge of the crosstalk between small non-coding RNA pathways and roles of sno-miRNAs in p53 regulation. PMID:26061048

  9. p53 Represses the Oncogenic Sno-MiR-28 Derived from a SnoRNA.

    PubMed

    Yu, Feng; Bracken, Cameron P; Pillman, Katherine A; Lawrence, David M; Goodall, Gregory J; Callen, David F; Neilsen, Paul M

    2015-01-01

    p53 is a master tumour repressor that participates in vast regulatory networks, including feedback loops involving microRNAs (miRNAs) that regulate p53 and that themselves are direct p53 transcriptional targets. We show here that a group of polycistronic miRNA-like non-coding RNAs derived from small nucleolar RNAs (sno-miRNAs) are transcriptionally repressed by p53 through their host gene, SNHG1. The most abundant of these, sno-miR-28, directly targets the p53-stabilizing gene, TAF9B. Collectively, p53, SNHG1, sno-miR-28 and TAF9B form a regulatory loop which affects p53 stability and downstream p53-regulated pathways. In addition, SNHG1, SNORD28 and sno-miR-28 are all significantly upregulated in breast tumours and the overexpression of sno-miR-28 promotes breast epithelial cell proliferation. This research has broadened our knowledge of the crosstalk between small non-coding RNA pathways and roles of sno-miRNAs in p53 regulation. PMID:26061048

  10. Drug resistance in African trypanosomiasis: the melarsoprol and pentamidine story

    PubMed Central

    Baker, Nicola; de Koning, Harry P.; Mäser, Pascal; Horn, David

    2013-01-01

    Melarsoprol and pentamidine represent the two main classes of drugs, the arsenicals and diamidines, historically used to treat the diseases caused by African trypanosomes: sleeping sickness in humans and Nagana in livestock. Cross-resistance to these drugs was first observed over sixty years ago and remains the only example of cross-resistance among sleeping sickness therapies. A Trypanosoma brucei adenosine transporter is well-known for its role in the uptake of both drugs. More recently, aquaglyceroporin 2 (AQP2) loss-of-function was linked to melarsoprol-pentamidine cross-resistance. AQP2, a channel that appears to facilitate drug accumulation, may also be linked to clinical cases of resistance. Here, we review these findings and consider some new questions as well as future prospects for tackling the devastating diseases caused by these parasites. PMID:23375541

  11. 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.

  12. Hypoxia-derived oxidative stress mediates epigenetic repression of PKCɛ gene in foetal rat hearts

    PubMed Central

    Patterson, Andrew J.; Xiao, Daliao; Xiong, Fuxia; Dixon, Brandon; Zhang, Lubo

    2012-01-01

    Aims Hypoxia causes protein kinase C epsilon (PKCɛ) gene repression in foetal hearts, resulting in heightened cardiac susceptibility to ischaemic injury in offspring. We tested the hypothesis that hypoxia inducible factor 1 (HIF-1) and/or reactive oxygen species (ROS) mediate hypoxia-induced PKCɛ gene repression. Methods and results Hypoxia induced in vivo to pregnant rats, ex vivo to isolated foetal rat hearts, and in vitro in the rat embryonic ventricular myocyte cell line H9c2 resulted in a comparable decrease in PKCɛ protein and mRNA abundance in foetal hearts and H9c2 cells, which was associated with a significant increase in CpG methylation of the SP1-binding sites at the PKCɛ promoter. In H9c2 cells and foetal hearts, hypoxia caused nuclear accumulation of HIF-1α, which was inhibited by 3-(5′-hydroxymethyl-2′-furyl)-1-benzylindazole and 2-methoxy estradiol. The HIF-1α inhibitors had no significant effect on hypoxia-induced PKCɛ mRNA repression. Hypoxia produced a time-dependent increase in ROS production in H9c2 cells and foetal hearts that was blocked by ROS scavengers N-acetyl-cysteine or tempol. In accordance, N-acetyl-cysteine and tempol, but not apocynin, inhibited the hypoxic effect and restored PKCɛ protein and mRNA expression to the control values in foetal hearts and H9c2 cells. The ROS scavengers blocked hypoxia-induced CpG methylation of the SP1-binding sites, restored SP1 binding to the PKCɛ promoter, and abrogated the hypoxia-induced increase in the susceptibility of the heart to ischaemic injury in offspring. Conclusions The results demonstrate that hypoxia induces epigenetic repression of the PKCɛ gene through a NADPH oxidase-independent ROS-mediated pathway in the foetal heart, leading to heightened heart vulnerability to ischaemic injury in offspring. PMID:22139554

  13. 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

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

    PubMed

    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

    2014-11-01

    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

  15. 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

  16. Intramuscular pentamidine for the prevention of Pneumocystis carinii pneumonia in patients infected with human immunodeficiency virus.

    PubMed

    Cheung, T W; Matta, R; Neibart, E; Hammer, G; Chusid, E; Sacks, H S; Szabo, S; Rose, D

    1993-01-01

    We retrospectively reviewed the charts of 96 patients infected with human immunodeficiency virus (HIV) who received intramuscular pentamidine for the prevention of Pneumocystis carinii pneumonia (PCP). These patients, all of whom had either a history of PCP or a CD4 lymphocyte count of < or = 0.2 x 10(9)/L, were intolerant of sulfa drugs, neutropenic, or intolerant of aerosolized treatment. Intramuscular pentamidine was given monthly by the Z-track technique at a dosage of 300 mg (4 mg/kg if the patient weighed < 50 kg). During a total of 350 months of primary prophylaxis in 47 patients and 426 months of secondary prophylaxis in 49 patients, only three cases of PCP occurred. More than 73% of the patients were receiving zidovudine concomitantly. Adverse reactions to intramuscular pentamidine included two episodes of hypotension, three of sterile abscess, two of glucose intolerance, and one of asymptomatic hypoglycemia. The administration of intramuscular pentamidine by the Z-track technique for PCP prophylaxis appears to be highly effective and minimally toxic. PMID:8448314

  17. Pulmonary deposition of nebulised pentamidine isethionate: effect of nebuliser type, dose, and volume of fill.

    PubMed

    O'Doherty, M; Thomas, S; Page, C; Bradbeer, C; Nunan, T; Bateman, N

    1990-06-01

    An estimate of the absolute pulmonary deposition of nebulised pentamidine isethionate was obtained in nine patients with AIDS. Two nebuliser systems were compared, System 22 Mizer (Medic-Aid) and Respirgard II (Marquest), with 50 and 150 mg doses of pentamidine in a 3 ml solution driven by an air flow of 6 l/min with the patient in the sitting position. The 50 mg pentamidine dose was repeated with a 6 ml fill with both devices. The nebuliser cloud was labelled with technetium-99m human serum albumin (Ventocol) and lung deposition was measured with a gamma camera. Of the two nebulisers studied, System 22 Mizer delivered more drug to the lungs as a whole and to each individual lung region, including the peripheral and upper zones. For the 50 mg dose the mean (SEM) total pulmonary deposition with the 3 and the 6 ml fill respectively was 2.63 (0.34) and 3.71 (0.41) mg for the System 22 Mizer and 1.37 (0.26) and 1.45 (0.18) mg for the Respirgard II. For the 150 mg dose the System 22 Mizer delivered 7.16 (1.02) mg and the Respirgard II 4.34 (0.57) mg. Increasing the volume of fill from 3 to 6 ml increased pulmonary deposition with System 22 Mizer, and this was related to an increase in nebuliser output. Neither pulmonary deposition nor nebuliser output was increased by using a 6 ml solution in the Respirgard II. Increasing the volume of fill prolonged the time required for nebulisation with both nebulisers. The System 22 Mizer produced more nonpulmonary (gastric and oropharyngeal) deposition of drug, more frequent local adverse effects (cough, burning in the throat, and a metallic taste), and small reductions in lung function, particularly with the 150 mg pentamidine dose. Thus nebuliser type, volume of fill, and nebuliser dose affect the pulmonary deposition of pentamidine. A 300 mg dose of pentamidine via a Respirgard II is generally recommended as providing effective prophylaxis; our results suggest that similar pulmonary deposition can be produced with System 22

  18. 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

  19. Serial use of pentamidine and miltefosine for treating Leishmania infantum-HIV coinfection.

    PubMed

    Faucher, Jean-François; Morquin, David; Reynes, Jacques; Chirouze, Catherine; Hoen, Bruno; Le Moing, Vincent

    2016-10-01

    Liposomal amphotericin B (LAmb) may fail to heal Leishmania infantum visceral leishmaniasis (VL) in the immunodeficient host. There are currently no guidelines on how to treat such patients and efficacy of miltefosine monotherapy seems limited in this indication. We present 2 cases of patients with VL and AIDS for which LAmb had to be interrupted (one because of toxicity, one because of treatment failure) and who were treated effectively with pentamidine followed by miltefosine. PMID:27353022

  20. 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.

  1. Epigenetic repression of PDZ-LIM domain-containing protein 2 promotes ovarian cancer via NOS2-derived nitric oxide signaling

    PubMed Central

    Lau, Wayne Bond; Lau, Bonnie; Luo, Zhongyue; Lin, Qiao; Yang, Huiliang; Xuan, Yu; Yi, Tao; Zhao, Xia; Wei, Yuquan

    2016-01-01

    Ovarian cancer constitutes one of the most lethal gynaecological malignancies worldwide and currently no satisfactory therapeutic approaches have been established. Therefore, elucidation of molecular mechanisms to develop targeted therapy of ovarian cancer is crucial. PDLIM2 is critical to promote ubiquitination of nuclear p65 and thus its role in inflammation has been highlighted recently. We demonstrate that PDLIM2 is decreased in both ovarian high-grade serous carcinoma and in various human ovarian cancer cell lines compared with normal ovary tissues and human ovarian surface epithelial cells (HOSE). Further functional analysis revealed that PDLIM2 is epigenetically repressed in ovarian cancer development and inhibition of PDLIM2 promoted ovarian cancer growth both in vivo and in vitro via NOS2-derived nitric oxide signaling, leading to recruitment of M2 type macrophages. These results suggest that PDLIM2 might be involved in ovarian cancer pathogenesis, which could serve as a promising therapeutic target for ovarian cancer patients. PMID:26593252

  2. A prospective comparison of Porta-sonic and Fisoneb ultrasonic nebulizers for administering aerosol pentamidine

    PubMed Central

    McIvor, Andrew; Flood, Diane; Lee-Pack, Leslie; Rachlis, Anita; Berger, Philip; Chan, Charles K

    1994-01-01

    Objective: To report patient acceptability and overall therapeutic effectiveness of two different ultrasonic nebulizers, Fisoneb and Porta-sonic, for the administration of aerosol pentamidine for Pneumocysitis carinii prophylaxis in human immunodeficiency virus (hiv)-infected individuals. Design: Prospective assessment of a random subgroup of 174 individuals from an inception cohort of 1093 patients attending a central aerosol pentamidine treatment centre in Toronto, Ontario. Methods: One hundred and seventy-four patients who had been receiving aerosolized pentamidine for more than 10 weeks using Fisoneb at 60 mg every two weeks were switched to Porta-sonic. Subjective evaluation included three standard 10 cm visual analogue scales rating cough/wheeze, aftertaste and overall preference. The individuals were also asked to compare the duration of time spent on the aerosol treatments. Objective evaluation included spirometry performed immediately before and 15 mins after pentamidine administration. Prospective surveillance of the entire cohort was preformed to record and document episodes of breakthrough P carinii pneumonia. Results: Porta-sonic was the overall preferred nebulizer in 82% of patients. Less time was spent on aerosol treatment using the Porta-sonic nebulizer compared with the Fisoneb in 66% of patients. The Porta-sonic nebulizer system produced less aftertaste compared with Fisoneb. Both nebulizers produced significant but modest reduction in flow rates. During the study period there was no statistically significant difference in the rates of breakthrough P carinii pneumonia between the two groups. A total of 91 episodes occurred, at a rate of 0.5 episodes per patient-month on Porta-sonic compared with 0.7 episodes per patient-month on Fisoneb (P=0.2536). Discussion: Aerosol pentamidine remains the proven second-line prophylaxis against P carinii pneumonia in hiv/aids for those intolerant to trimethoprim-sulphamethoxazole. Cough, bronchospasm and poor

  3. Differentiation of neurosphere-derived rat neural stem cells into oligodendrocyte-like cells by repressing PDGF-α and Olig2 with triiodothyronine.

    PubMed

    Abbaszadeh, Hojjat-Allah; Tiraihi, Taki; Delshad, AliReza; Saghedizadeh, Majid; Taheri, Taher; Kazemi, Hadi; Hassoun, Hayder K

    2014-12-01

    One of the approaches for treating demyelination diseases is cytotherapy, and adult stem cells are potential sources. In this investigation, we tried to increase the yield of oligodendrocyte-like cells (OLCs) by inducing neural stem cells generated from BMSCs-derived neurospheres, which were used for deriving the neural stem cells (NSCs). The latter were induced into OLCs by heregulin, PDGF-AA, bFGF and triiodothyronine (T3). The BMSCs, NS, NSCs and OLCs were characterized by using immunocytochemistry for fibronectin, CD44, CD90, CD45, Oct-4, O4, Olig2, O1 and MBP markers. PDGF receptor α (PDGFR-α), Olig2 and MOG expression were evaluated by RT-PCR. The BMSCs expressed CD44, CD90, CD106 and Oct-4; the NSCs were immunoreactive to nestin and neurofilament 68. Incubation of the NSCs for 4 days with heregulin, PDGF-AA and bFGF resulted in their induction into oligodendrocyte progenitor-like cells (OPLCs), which immunoreacted to O4, Olig2 and O1, while Olig2 and PDGFR-α were detected by RT-PCR. Replacing heregulin, PDGF-AA and bFGF with T3 for 6 days resulted in repression of O4, O1, Olig2 and PDGFR-α. The OLCs were co-cultured with motoneurons resulted in induction of MOG and MBP, which were expressed in functional OLCs. The latter can be generated from BMSCs-derive NS with high yield. PMID:25200619

  4. Computational repositioning and preclinical validation of pentamidine for renal cell cancer

    PubMed Central

    de Vasconcellos, Jaira F.; Paccez, Juliano D.; Gu, Xuesong; Kung, Andrew L.; Libermann, Towia A.

    2014-01-01

    While early stages of clear cell renal cell carcinoma (ccRCC) are curable, survival outcome for metastatic ccRCC remains poor. We previously established a highly accurate signature of differentially expressed genes that distinguish ccRCC from normal kidney. The purpose of the current study was to apply a new individualized bioinformatics analysis (IBA) strategy to these transcriptome data in conjunction with Gene Set Enrichment Analysis of the Connectivity Map (C-MAP) database to identify and reposition FDA-approved drugs for anti-cancer therapy. Here we demonstrate that one of the drugs predicted to revert the RCC gene signature towards normal kidney, pentamidine, is effective against RCC cells in culture and in a RCC xenograft model. ccRCC-specific gene expression signatures of individual patients were used to query the C-MAP software. Eight drugs with negative correlation and p-value <0.05 were analyzed for efficacy against RCC in vitro and in vivo. Our data demonstrate consistency across most ccRCC patients for the set of high scoring drugs. Most of the selected high scoring drugs potently induce apoptosis in RCC cells. Several drugs also demonstrate selectivity for VHL negative RCC cells. Most importantly, at least one of these drugs, pentamidine, slows tumor growth in the 786-O human ccRCC xenograft mouse model. Our findings suggest that pentamidine might be a new therapeutic agent to be combined with current standard-of-care regimens for metastatic ccRCC patients and support our notion that IBA combined with C-MAP analysis enables repurposing of FDA-approved drugs for potential anti-RCC therapy. PMID:24785412

  5. PSP94 contributes to chemoresistance and its peptide derivative PCK3145 represses tumor growth in ovarian cancer.

    PubMed

    Yan, B-X; Ma, J-X; Zhang, J; Guo, Y; Riedel, H; Mueller, M D; Remick, S C; Yu, J J

    2014-11-01

    Tumor drug resistance remains a major challenge in the treatment of cancer. Here, we show that Prostatic secretory protein 94 (PSP94) levels are reduced in ovarian cancer patients with high levels of excision repair cross-complementing 1 (ERCC1), a marker for chemoresistance. We find that PSP94 is decreased in an ovarian cancer drug-resistant cell line, and plays an important role in the development of drug resistance in vitro. Our studies indicate that PSP94 can partially reverse drug resistance in mouse tumor models in vivo and that a PSP94 peptide derivative PCK3145 suppresses chemoresistant cancer cell and tumor growth in vitro and in vivo. Our investigation of the involved molecular mechanisms suggests that PSP94 may confer drug resistance by modulating the Lin28b/Let-7 signaling pathway. We introduce PSP94 and its peptide derivative PCK3145 as potential target to reverse chemoresistance in ovarian cancer and have begun to identify their relevant molecular targets in specific signaling pathways. PMID:24186202

  6. 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. PMID:26965996

  7. Repressive Effect of Primary Virus Replication on Superinfection Correlated with Gut-Derived Central Memory CD4+ T Cells in SHIV-Infected Chinese Rhesus Macaques

    PubMed Central

    Xiong, Jing; Wang, Wei; Jiang, Hong; Chen, Ting; Wu, Fangxin; Liu, Kejian; Su, Aihua; Ju, Bin; Chen, Zhiwei; Couto, Marcelo A.; Wei, Qiang; Qin, Chuan

    2013-01-01

    A possible mechanism of susceptibility to superinfection with simian-human immunodeficiency virus (SHIV)-1157ipd3N4 was explored in twelve SHIVSF162P3-infected Chinese rhesus macaques. Based on the kinetics of viral replication for the second infecting virus following SHIV-1157ipd3N4 inoculation, the monkeys were divided into two groups: those relatively resistant to superinfection (SIR) and those relatively sensitive to superinfection (SIS). We found that superinfection-resistant macaques had high primary viremia, whereas superinfection-sensitive macaques had low primary viremia, suggesting that primary SHIVSF162P3 infection with a high viral-replication level would repress superinfection with a heterologous SHIV-1157ipd3N4. Although no correlation of protection against superinfection with virus-specific CD4+ T cell or CD8+ T cell immune responses from gut was observed prior to superinfection, superinfection susceptibility was strongly correlated with CD4+ Tcm cells from gut both prior to the second infecting virus inoculation and on day 7 after superinfection, but not with CD4+ Tem cells from gut or with CD4+ Tcm cells from peripheral blood and lymph node. These results point to the important roles of gut-derived CD4+ Tcm cells for the study of the mechanisms of protection against superinfection and the evaluation of the safety and efficacy of vaccines and therapies against acquired immune deficiency syndrome (AIDS). PMID:24023734

  8. EFFECT OF PENTAMIDINE ON CYTOKINE (IL-1B, TNFA, IL-6) PRODUCTION BY HUMAN ALVEOLAR MACROPHAGES IN VITRO

    EPA Science Inventory

    Pentamidine (Pe) is an aromatic diamidine drug used clinically to treat Pneumocystis carinii pneumonia by aerosol inhalation. othing has been reported about the effects of this drug on human alveolar macrophage (AM) properties. n this study AM were exposed in vitro to various con...

  9. Simvastatin represses protein synthesis in the muscle-derived C₂C₁₂ cell line with a concomitant reduction in eukaryotic initiation factor 2B expression.

    PubMed

    Tuckow, Alexander P; Jefferson, Sarah J; Kimball, Scot R; Jefferson, Leonard S

    2011-03-01

    Statins are a widely prescribed class of cholesterol lowering drugs whose use is frequently associated with muscle-related ailments. A number of mechanisms have been implicated in statin-induced myotoxicity including alterations in both protein synthesis and protein degradation. The objective of the present study was to explore the mechanism(s) contributing to the statin-induced reduction in protein synthesis in the muscle-derived C₂C₁₂ cell line. Cells were treated with 10 μM simvastatin or vehicle alone for 24 h in 1% serum. Cells exposed to simvastatin exhibited reduced rates of protein synthesis, as evidenced by [(35)S]methionine and [(35)S]cysteine incorporation into protein. The reduction in protein synthesis occurred with a concomitant decrease in expression and activity of eukaryotic initiation factor 2B (eIF2B), a regulated and rate-controlling guanine nucleotide exchange factor known to affect global rates of protein synthesis. The reductions in protein synthesis and eIF2B expression were prevented by coincubation with mevalonate. Simvastatin treatment also resulted in a proteasome-sensitive reduction in the protein expression of all the subunits of the eIF2B heteropentameric complex. Finally, increased phosphorylation of the catalytic ε-subunit at Ser(535) was observed, an event consistent with an observed reduction in eIF2B activity. These results suggest that repression of eIF2B expression and activity may contribute, at least in part, to the statin-induced reduction in protein synthesis. PMID:21224482

  10. Repression: A Bibliography.

    ERIC Educational Resources Information Center

    Pedrini, D. T.; Pedrini, Bonnie C.

    Repression was considered by Freud as a key mechanism for everyone, especially for normals and neurotics. His Repression paper, written in 1915, was psychoanalytically definitive. Of course, much had been written before and even more was written after. Anna Freud's book The Ego and the Mechanisms of Defence included repression and was published by…

  11. 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

  12. 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

  13. Randomized Single-Blinded Non-inferiority Trial Of 7 mg/kg Pentamidine Isethionate Versus 4 mg/kg Pentamidine Isethionate for Cutaneous Leishmaniaisis in Suriname

    PubMed Central

    Hu, Ricardo V. P. F.; Straetemans, Masja; Kent, Alida D.; Sabajo, Leslie O. A.; de Vries, Henry J. C.; Lai A Fat, Rudy F. M.

    2015-01-01

    Background Standard treatment of cutaneous leishmaniasis (CL) in Suriname entails three injections of pentamidine isethionate (PI) 4 mg/kg per injection in 7 days (7 day regimen). Compliance to treatment is low and may contribute to increasing therapy failure. A 3 day regimen, including 2 injections of 7 mg/kg in 3 days may increase compliance. Methods In a randomized, single-blinded non-inferiority trial conducted in Suriname, 84 CL patients received the 7 day regimen and 79 CL patients received the 3 day regimen. Primary objective was the proportion of patients clinically cured at 6 weeks follow-up. Secondary objectives were clinical cure at 12 weeks follow-up; parasitological cure at 6 and 12 weeks; adverse and drug related toxicity events recorded one week after the end of treatment and health related quality of life. The non-inferiority margin was set at 15%, 1 sided test, α = 0.1. Results At 6 weeks follow-up 31 (39%) patients in the 3 day regimen and 41 (49%) patients in the 7 day regimen were clinically cured. Intention to treat (ITT) analyses showed that the difference in proportion clinically cured was -9.6% (90% Confidence Interval (CI): -22.3% to 3.2%). Per protocol (PP) analysis showed that the difference in proportion clinically cured was 0.2% (90% CI: -14.6% to 15.2%). ITT analysis showed that the difference in proportion parasitological cured at 6 weeks was -15.2% (90% CI:-28.0% to -2.5%). PP analyses showed similar results. Non-inferiority could not be concluded for all adverse and toxicological events. Conclusion We cannot conclude that the 3 day regimen is non-inferior to the 7 day regimen regarding proportion clinically and parasitological cured. Therefore there is no evidence to change the current standard practice of the 7 day regimen for the treatment of CL in Suriname. PMID:25793773

  14. In vitro life cycle of pentamidine-resistant amastigotes: stability of the chemoresistant phenotypes is dependent on the level of resistance induced.

    PubMed Central

    Sereno, D; Lemesre, J L

    1997-01-01

    Using a continuous drug pressure protocol, we induced pentamidine resistance in an active and dividing population of amastigote forms of Leishmania mexicana. We selected in vitro two clones with different levels of resistance to pentamidine, with clone LmPENT5 being resistant to 5 microM pentamidine, while clone LmPENT20 was resistant to 20 microM pentamidine. Resistance indexes (50% inhibitory concentration [IC50] after drug presure/IC50 before drug pressure) of 2 (LmPENT5) and 6 (LmPENT20) were determined after drug selection. Both resistant clones expressed significant cross-resistance to diminazene aceturate and primaquine. Pentamidine resistance was not reversed by verapamil, a calcium channel blocker known to reverse multidrug resistance (A. J. Bitonti, et al., Science 242:1301-1303, 1988; A. R. C. Safa et al., J. Biol. Chem. 262:7884-7888, 1987). No difference in the in vitro infectivity for resident mouse macrophages was observed between the wild-type clone (clone LmWT) and pentamidine-resistant clones. During in vitro infectivity experiments, when the life cycle was performed starting from the intramacrophagic amastigote stage, the drug resistance of the resulting LmPENT20 amastigotes was preserved even if the intermediate promastigote stage could not be considered resistant to 20 microM pentamidine. In the same way, when a complete developmental sequence of L. mexicana was achieved axenically by manipulation of appropriate culture conditions, the resulting axenically grown LmPENT20 amastigotes remained pentamidine resistant, whereas LmPENT5 amastigotes lost their ability to resist pentamidine, with IC50s and index of resistance values close to those for the LmWT clone. These results strongly indicate that the level of pentamidine tolerated by resistant amastigotes after the life cycle was dependent on the induced level of resistance. This fact could be significant in the in vivo transmission of drug-resistant parasites by Phlebotominae. Particular

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

    PubMed

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

    2015-08-01

    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

  16. 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. PMID:9618445

  17. 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.

  18. 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

  19. 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…

  20. Repression of platelet-derived growth factor A-chain gene transcription by an upstream silencer element. Participation by sequence-specific single-stranded DNA-binding proteins.

    PubMed

    Liu, B; Maul, R S; Kaetzel, D M

    1996-10-18

    Platelet-derived growth factor A-chain is a potent mitogen expressed in a restricted number of normal and transformed cells. Transient transfection and deletion analysis in BSC-1 (African green monkey, renal epithelial) cells revealed that the -1680 to -1374 region of the A-chain gene repressed homologous and heterologous promoter activities by 60-80%. An S1 nuclease-hypersensitive region (5'SHS) was identified within this region (-1418 to -1388) that exhibited transcriptional silencer activity in BSC-1 and a variety of human tumor cell lines (U87, HepG2, and HeLa). Electrophoretic mobility shift assays conducted with 5'SHS oligodeoxynucleotide probes revealed several binding protein complexes that displayed unique preferences for binding to sense, antisense, and double-stranded forms of the element. Southwestern blot analysis revealed that the antisense strand of 5'SHS binds to nuclear proteins of molecular mass 97, 87, 44, and 17 kDa, whereas the double-stranded form of 5'SHS is recognized by a 70-kDa factor. Mutations within 5'SHS element indicated the necessity of a central 5'-GGGGAGGGGG-3' motif for protein binding and silencer function, while nucleotides flanking both sides of the motif were also critical for repression. These results support a model in which silencer function of 5'SHS is mediated by antisense strand binding proteins, possibly by stabilizing single-stranded DNA conformations required for interaction with enhancer sequences in the proximal promoter region of the A-chain gene. PMID:8824279

  1. 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

  2. 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

  3. MicroRNA-31 negatively regulates peripherally derived regulatory T-cell generation by repressing retinoic acid-inducible protein 3.

    PubMed

    Zhang, Lingyun; Ke, Fang; Liu, Zhaoyuan; Bai, Jing; Liu, Jinlin; Yan, Sha; Xu, Zhenyao; Lou, Fangzhou; Wang, Hong; Zhu, Huiyuan; Sun, Yang; Cai, Wei; Gao, Yuanyuan; Li, Qun; Yu, Xue-Zhong; Qian, Youcun; Hua, Zichun; Deng, Jiong; Li, Qi-Jing; Wang, Honglin

    2015-01-01

    Peripherally derived regulatory T (pT(reg)) cell generation requires T-cell receptor (TCR) signalling and the cytokines TGF-β1 and IL-2. Here we show that TCR signalling induces the microRNA miR-31, which negatively regulates pT(reg)-cell generation. miR-31 conditional deletion results in enhanced induction of pT(reg) cells, and decreased severity of experimental autoimmune encephalomyelitis (EAE). Unexpectedly, we identify Gprc5a as a direct target of miR-31. Gprc5a is known as retinoic acid-inducible protein 3, and its deficiency leads to impaired pT(reg-)cell induction and increased EAE severity. By generating miR-31 and Gprc5a double knockout mice, we show that miR-31 promotes the development of EAE through inhibiting Gprc5a. Thus, our data identify miR-31 and its target Gprc5a as critical regulators for pT(reg)-cell generation, suggesting a previously unrecognized epigenetic mechanism for dysfunctional T(reg) cells in autoimmune diseases. PMID:26165721

  4. 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 ...

  5. Use of Pentamidine As Secondary Prophylaxis to Prevent Visceral Leishmaniasis Relapse in HIV Infected Patients, the First Twelve Months of a Prospective Cohort Study

    PubMed Central

    Diro, Ermias; Ritmeijer, Koert; Boelaert, Marleen; Alves, Fabiana; Mohammed, Rezika; Abongomera, Charles; Ravinetto, Raffaella; De Crop, Maaike; Fikre, Helina; Adera, Cherinet; Colebunders, Robert; van Loen, Harry; Menten, Joris; Lynen, Lutgarde; Hailu, Asrat; van Griensven, Johan

    2015-01-01

    Background Visceral leishmaniasis (VL) has become an important opportunistic infection in persons with HIV-infection in VL-endemic areas. The co-infection leads to profound immunosuppression and high rate of annual VL recurrence. This study assessed the effectiveness, safety and feasibility of monthly pentamidine infusions to prevent recurrence of VL in HIV co-infected patients. Methods A single-arm, open-label trial was conducted at two leishmaniasis treatment centers in northwest Ethiopia. HIV-infected patients with a VL episode were included after parasitological cure. Monthly infusions of 4mg/kg pentamidine-isethionate diluted in normal-saline were started for 12months. All received antiretroviral therapy (ART). Time-to-relapse or death was the primary end point. Results Seventy-four patients were included. The probability of relapse-free survival at 6months and at 12 months was 79% and 71% respectively. Renal failure, a possible drug-related serious adverse event, occurred in two patients with severe pneumonia. Forty-one patients completed the regimen taking at least 11 of the 12 doses. Main reasons to discontinue were: 15 relapsed, five died and seven became lost to follow-up. More patients failed among those with a CD4+cell count ≤ 50cells/μl, 5/7 (71.4%) than those with counts above 200 cells/μl, 2/12 (16.7%), (p = 0.005). Conclusion Pentamidine secondary prophylaxis led to a 29% failure rate within one year, much lower than reported in historical controls (50%-100%). Patients with low CD4+cell counts are at increased risk of relapse despite effective initial VL treatment, ART and secondary prophylaxis. VL should be detected and treated early enough in patients with HIV infection before profound immune deficiency installs. PMID:26431253

  6. 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

  7. 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. PMID:26205245

  8. 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

  9. The unified theory of repression.

    PubMed

    Erdelyi, Matthew Hugh

    2006-10-01

    Repression has become an empirical fact that is at once obvious and problematic. Fragmented clinical and laboratory traditions and disputed terminology have resulted in a Babel of misunderstandings in which false distinctions are imposed (e.g., between repression and suppression) and necessary distinctions not drawn (e.g., between the mechanism and the use to which it is put, defense being just one). "Repression" was introduced by Herbart to designate the (nondefensive) inhibition of ideas by other ideas in their struggle for consciousness. Freud adapted repression to the defensive inhibition of "unbearable" mental contents. Substantial experimental literatures on attentional biases, thought avoidance, interference, and intentional forgetting exist, the oldest prototype being the work of Ebbinghaus, who showed that intentional avoidance of memories results in their progressive forgetting over time. It has now become clear, as clinicians had claimed, that the inaccessible materials are often available and emerge indirectly (e.g., procedurally, implicitly). It is also now established that the Ebbinghaus retention function can be partly reversed, with resulting increases of conscious memory over time (hypermnesia). Freud's clinical experience revealed early on that exclusion from consciousness was effected not just by simple repression (inhibition) but also by a variety of distorting techniques, some deployed to degrade latent contents (denial), all eventually subsumed under the rubric of defense mechanisms ("repression in the widest sense"). Freudian and Bartlettian distortions are essentially the same, even in name, except for motive (cognitive vs. emotional), and experimentally induced false memories and other "memory illusions" are laboratory analogs of self-induced distortions. PMID:17156548

  10. 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

  11. 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

  12. Rule of Repression in Chile.

    ERIC Educational Resources Information Center

    American Indian Journal, 1979

    1979-01-01

    This report on the current condition of the Mapuche Indians of Chile is edited from a document on the "Situation of Human Rights in Chile" and details the repressive and inhumane treatment of the largest indigenous ethnic minority in the country. (Author/RTS)

  13. Activity of Bisnaphthalimidopropyl Derivatives against Trypanosoma brucei.

    PubMed

    Graça, Nuno A G; Gaspar, Luis; Costa, David M; Loureiro, Inês; Thoo-Lin, Paul Kong; Ramos, Isbaal; Roura, Meritxell; Pruvost, Alain; Pemberton, Ian K; Loukil, Hadjer; MacDougall, Jane; Tavares, Joana; Cordeiro-da-Silva, Anabela

    2016-04-01

    Current treatments for African trypanosomiasis are either toxic, costly, difficult to administer, or prone to elicit resistance. This study evaluated the activity of bisnaphthalimidopropyl (BNIP) derivatives againstTrypanosoma brucei BNIPDiaminobutane (BNIPDabut), the most active of these compounds, showedin vitroinhibition in the single-unit nanomolar range, similar to the activity in the reference drug pentamidine, and presented low toxicity and adequate metabolic stability. Additionally, using a murine model of acute infection and live imaging, a significant decrease in parasite load in BNIPDabut-treated mice was observed. However, cure was not achieved. BNIPDabut constitutes a new scaffold for antitrypanosomal drugs that deserves further consideration. PMID:26787703

  14. Pentamidine Isethionate Injection

    MedlinePlus

    ... your doctor or pharmacist for more information.Your health care provider (doctor, nurse, or pharmacist) may measure ... solution, but show the damaged one to your health care provider.It is important that you use ...

  15. 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 ...

  16. A controlled, randomized nonblinded clinical trial to assess the efficacy of amphotericin B deoxycholate as compared to pentamidine for the treatment of antimony unresponsive visceral leishmaniasis cases in Bihar, India

    PubMed Central

    Das, Vidya Nand Rabi; Siddiqui, Niyamat Ali; Pandey, Krishna; Singh, Vijay Pratap; Topno, Roshan K; Singh, Dharmendra; Verma, Rakesh Bihari; Ranjan, Alok; Sinha, Prabhat Kumar; Das, Pradeep

    2009-01-01

    Background: There is significant variation in Amphotericin B (AMB) efficacy and relapses in antimony unresponsive visceral leishmaniasis (VL) cases over a period of time (10–15 years). Keeping in mind the above mentioned view this study was undertaken with an objective to assess the magnitude of cure and relapse rates of AMB in the treatment of antimony unresponsive VL cases. Methods: In a controlled, randomized nonblinded clinical trial, we evaluated the cure and relapse rate of Amphotericin B deoxycholate as compared to pentamidine. A total of 82 sodium stibogluconate (SSG) unresponsive and parasitologically confirmed VL cases were included in this study and randomized into two groups, test (Amphotericin B) and control (Pentamidine). Both the groups were treated with recommended dosages (as per World Health Organization guidelines) of respective medicines. All the patients were followed up on 1st, 2nd, and 6th month after end of treatment. Results: Apparent cure rate in the Amphotericin B group was found to be 95% (39/41) compared with 83% (34/41) in the Pentamidine group, which shows significant statistical difference (p = 0.05). The ultimate cure rate was found 92% (38/41) in the Amphotericin B group compared to 73% (30/41) in the Pentamidine group, which shows a significant statistical difference (Yates corrected chi-square = 4.42, p = 0.04). Similarly, significant statistical difference was observed in the relapse rate of the Amphotericin group compared to the Pentamidine group (p = 0.03). Conclusions: AMB may still be the drug of choice in the management of resistant VL cases in Bihar, India. This is due to its consistent apparent cure rate (95%), low relapse rate (2.5%), and cost effectiveness compared with other available antileishmanial drugs. It is a safe drug even in case of pregnancy. Efforts should be taken to form a future strategy so that this drug and coming newer drugs do not meet a similar fate as has happened to SSG and pentamidine over a span

  17. Promoter-binding and repression of PDGFRB by c-Myc are separable activities

    PubMed Central

    Mao, Daniel Y. L.; Barsyte-Lovejoy, Dalia; Ho, Cynthia S. W.; Watson, John D.; Stojanova, Angelina; Penn, Linda Z.

    2004-01-01

    The c-Myc transcription factor represses the mRNA expression of the platelet-derived growth factor receptor beta gene (PDGFRB). Using chromatin immunoprecipitation, we show that c-Myc binds to the proximal promoter of the PDGFRB gene in proliferating rat fibroblasts. Interestingly, mutant c-Myc proteins that are unable to repress PDGFRB gene expression, c-MycdBR and c-Mycd106-143, are still able to bind to the promoter in vivo. Hence, promoter-binding and repression of PDGFRB by c-Myc are separable activities. We also show that Myc repression of PDGFRB is not dependent on previously described or known transactivator-binding regions, suggesting Myc may be recruited to the promoter by multiple or yet unidentified transcription factors. In the presence of intact promoter-binding by Myc, trichostatin A (TSA) can block Myc repression of PDGFRB in vivo, again demonstrating that promoter-binding and repression are separable. Taken together, we hypothesize that Myc repression of PDGFRB expression occurs by a multi-step mechanism in which repression is initiated after Myc is recruited to the promoter. PMID:15226411

  18. Mechanism and Role of SOX2 Repression in Seminoma: Relevance to Human Germline Specification.

    PubMed

    Kushwaha, Ritu; Jagadish, Nirmala; Kustagi, Manjunath; Mendiratta, Geetu; Seandel, Marco; Soni, Rekha; Korkola, James E; Thodima, Venkata; Califano, Andrea; Bosl, George J; Chaganti, R S K

    2016-05-10

    Human male germ cell tumors (GCTs) are derived from primordial germ cells (PGCs). The master pluripotency regulator and neuroectodermal lineage effector transcription factor SOX2 is repressed in PGCs and the seminoma (SEM) subset of GCTs. The mechanism of SOX2 repression and its significance to GC and GCT development currently are not understood. Here, we show that SOX2 repression in SEM-derived TCam-2 cells is mediated by the Polycomb repressive complex (PcG) and the repressive H3K27me3 chromatin mark that are enriched at its promoter. Furthermore, SOX2 repression in TCam-2 cells can be abrogated by recruitment of the constitutively expressed H3K27 demethylase UTX to the SOX2 promoter through retinoid signaling, leading to expression of neuronal and other lineage genes. SOX17 has been shown to initiate human PGC specification, with its target PRDM1 suppressing mesendodermal genes. Our results are consistent with a role for SOX2 repression in normal germline development by suppressing neuroectodermal genes. PMID:27132888

  19. 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

  20. Multiple Gene Repression in Cyanobacteria Using CRISPRi.

    PubMed

    Yao, Lun; Cengic, Ivana; Anfelt, Josefine; Hudson, Elton P

    2016-03-18

    We describe the application of clustered regularly interspaced short palindromic repeats interference (CRISPRi) for gene repression in the model cyanobacterium Synechcocystis sp. PCC 6803. The nuclease-deficient Cas9 from the type-II CRISPR/Cas of Streptrococcus pyogenes was used to repress green fluorescent protein (GFP) to negligible levels. CRISPRi was also used to repress formation of carbon storage compounds polyhydroxybutryate (PHB) and glycogen during nitrogen starvation. As an example of the potential of CRISPRi for basic and applied cyanobacteria research, we simultaneously knocked down 4 putative aldehyde reductases and dehydrogenases at 50-95% repression. This work also demonstrates that tightly repressed promoters allow for inducible and reversible CRISPRi in cyanobacteria. PMID:26689101

  1. 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

  2. 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

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

    2016-05-01

    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

  3. 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

  4. The relationship of repression to the unconscious.

    PubMed

    Gillett, E

    1987-01-01

    I try to formulate the simplest topographic model that embodies current theoretical understanding. The repression mechanism is under the control of a single censorship located on the border of consciousness. I argue that neither the operation of the repression mechanism nor the decision process of the censorship, which controls the repression mechanism and other defence mechanisms, can be considered dynamically unconscious. I discuss the distinction drawn by Wallerstein, Sandler & Joffe between the experiential and the non-experiential, concluding that much of the non-conscious id, ego, and superego is non-experiential rather than dynamically unconscious. Within the experiential realm I present the reasons why the censorship is located on the edge of consciousness and the implications of this location for the distinction between the preconscious and the dynamic unconscious. PMID:3436713

  5. Repressive translational control in germ cells.

    PubMed

    Lai, Fangfang; King, Mary Lou

    2013-08-01

    The earliest stages of embryonic development in many animals proceed without zygotic transcription. Genetic control is executed by maternally inherited mRNAs that are under translational control. To set aside the future germ cell lineage, it is pivotal to both exert translational regulation of maternal germline mRNAs and to repress maternal signals in those same cells that drive somatic cell-fate determination. Here we review repressive translational regulation in the germline from the perspective of the conserved RNA binding proteins Pumilio and Nanos, and discuss common themes that have emerged. PMID:23408501

  6. Repression of arterial genes in hemogenic endothelium is sufficient for haematopoietic fate acquisition.

    PubMed

    Lizama, Carlos O; Hawkins, John S; Schmitt, Christopher E; Bos, Frank L; Zape, Joan P; Cautivo, Kelly M; Borges Pinto, Hugo; Rhyner, Alexander M; Yu, Hui; Donohoe, Mary E; Wythe, Joshua D; Zovein, Ann C

    2015-01-01

    Changes in cell fate and identity are essential for endothelial-to-haematopoietic transition (EHT), an embryonic process that generates the first adult populations of haematopoietic stem cells (HSCs) from hemogenic endothelial cells. Dissecting EHT regulation is a critical step towards the production of in vitro derived HSCs. Yet, we do not know how distinct endothelial and haematopoietic fates are parsed during the transition. Here we show that genes required for arterial identity function later to repress haematopoietic fate. Tissue-specific, temporally controlled, genetic loss of arterial genes (Sox17 and Notch1) during EHT results in increased production of haematopoietic cells due to loss of Sox17-mediated repression of haematopoietic transcription factors (Runx1 and Gata2). However, the increase in EHT can be abrogated by increased Notch signalling. These findings demonstrate that the endothelial haematopoietic fate switch is actively repressed in a population of endothelial cells, and that derepression of these programs augments haematopoietic output. PMID:26204127

  7. Junk DNA and sectorial gene repression.

    PubMed

    Zuckerkandl, E

    1997-12-31

    Transcriptional repression in eukaryotes often involves tens or hundreds of kilobase pairs, two to three orders of magnitude more than the bacterial operator/repressor model does. Classical repression, represented by this model, was maintained over the whole span of evolution under different guises, and consists of repressor factors interacting primarily with promoters and, in later evolution, also with enhancers. The use of much larger amounts of DNA in the other mode of repression, here called the sectorial mode ('superrepression'), results in the conceptual transfer of so-called junk DNA to the domain of functional DNA. This contribution to the solution of the c-value paradox involves perhaps 15% of genomic 'junk,' and encompasses the bulk of the introns, thought to fill a stabilizing role in sectorially repressed chromatin structures. In the case of developmental genes, such structures appear to be heterochromatoid in character. However, solid clues regarding general structural features of superrepressed terminal differentiation genes remain elusive. The competition among superrepressible DNA sectors for sectorially binding factors offers, in principle, a molecular mechanism for developmental switches. Position effect variegation may be considered an abnormal manifestation of normal processes that underly development and involve heterochromatoid sectorial repression, which is apparently required for local elimination or modulation of morphological features (morpholysis). Sectorial repression of genes participating either in development or in terminal differentiation is considered instrumental in establishing stable cell types, and provides a basis for the distinction between determination and cell type specification. The gamut of possible stable cell types may have been broadened by the appearance in evolution of heavy isochores. Additional types of relatively frequent GC-rich cis-acting DNA motifs may offer reiterated binding sites to factors endowed with a

  8. Repression and substitutive formation: the relationship between Freud's concepts reconsidered.

    PubMed

    Zepf, Siegfried

    2012-06-01

    This paper examines Freud's concept of repression and the relationship between repression and substitutive formation as it presents itself in Freud's writings. The author shows that Freud gives at least four different meanings to the term "repression": Freud uses it interchangeably with defense, as a consciously intended forgetting, as a specific unconscious mechanism of defense, and to describe the consequence of defense mechanisms leading to substitutive formations. The inconsistencies in this relationship are discussed and clarified, and Freud's economic and linguistic attempts at founding repression are subjected to critique; the need of a primal repression as a necessary condition for repression proper is pointed out. In developing Freud's linguistic foundation of repression further, the author presents defense as a semantic displacement. Ideas are excluded from the realm of the concepts that belong to them historically. These presentations become unconscious, that is, repressed, in that they can no longer be identified as "cases" of these conceptual internal contents. At the same time they are displaced into the extensions of concepts whose internal contents do not belong to them originally. It is by virtue of the internal contents of these concepts that the displaced elements as substitutive formations once again attain consciousness, albeit a false one. The author suggests dismissing repression as a specific defense mechanism of its own; to reversing Freud's thesis that repression, as a rule, creates a substitutive formation into its opposite; and recognizing that the mechanisms used to build substitutes, as a rule, create repression. PMID:22712593

  9. 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.

  10. Molecular mechanisms of COUP-TF-mediated transcriptional repression: evidence for transrepression and active repression.

    PubMed Central

    Leng, X; Cooney, A J; Tsai, S Y; Tsai, M J

    1996-01-01

    COUP-TF, an orphan member of the nuclear receptor superfamily, has been proposed to play a key role in regulating organogenesis, neurogenesis, and cellular differentiation during embryonic development. Since heterodimierization is a common theme within the nuclear receptor superfamily and has been demonstrated to modulate transcriptional properties of heterodimeric partners via allosteric interactions, we have devised a strategy to examine the silencing function of COUP-TF in a heterodimeric context. We find that the intrinsic active repression function of COUP-TF is not affected by heterodimerization. Moreover, COUP-TF can transrepress the ligand-dependent activation of its heterodimeric partners without its own DNA binding site. Using receptor deletion mutants in transfection assays, we show that the region necessary for COUP-TF silencing function is not sufficient for its transrepression activity. Furthermore, our studies indicate that in addition to its active repression function, COUP-TF can repress several different types of activator-dependent transactivation. However, this active repression function of COUP-TF may be differentially regulated by some other activator(s). These studies provide new insights into the molecular mechanism(s) of COUP-TF-mediated repression. PMID:8628300

  11. 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.

  12. 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

  13. Multiple mechanisms of transcriptional repression by YY1.

    PubMed Central

    Galvin, K M; Shi, Y

    1997-01-01

    The four C-terminal GLI-Krüppel type zinc fingers of YY1 have been identified as a transcriptional repression domain. Previous reports have proposed DNA-bending and activator-quenching mechanisms for this zinc finger-mediated repression. In addition, previous work indicated that p300 and CBP might be involved in YY1-mediated repression. We have analyzed these possible models for the zinc finger-mediated repression. The role of each zinc finger in the repression and DNA-binding functions was determined by using a structure-and-function approach. We show that zinc finger 2 of YY1 plays a central role in both DNA binding and transcriptional repression. However, a survey of a panel of YY1 mutants indicates that these two functions can be separated, which argues against the DNA-bending model for repression. We show that the physical interaction between YY1 and p300, a coactivator for CREB, is not sufficient for repression of CREB-mediated transcription. Our studies indicate that YY1 functions as an activator-specific repressor. Repression of CTF-1-directed transcription may be accomplished through direct physical interaction between YY1 and this activator. In contrast, physical interaction is not necessary for YY1 to repress Sp1- and CREB-mediated transcription. Rather, the repression likely reflects an ability of YY1 to interfere with communication between these activators and their targets within the general transcription machinery. Taken together, our results suggest that YY1 employs multiple mechanisms to achieve activator-specific repression. PMID:9199306

  14. 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

    2014-01-01

    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. 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

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

    PubMed

    Strauss, H; Hadar, M; Shavit, H; Itskowitz, R

    1981-08-01

    The present study dealt with the extent to which creativity may be identified in 71 first graders and raised the question of whether and how creativity is related to anxiety and repression at this young age. Furthermore, correlation of 0.62 was obtained between creativity and decrease in repression. The various subtests and the four dimensions of creativity were separately analyzed in relation to anxiety and repression, and the results were discussed. No relation was found between intelligence and the dynamic variables of anxiety and repression. PMID:7290875

  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. Nuclear AXIN2 represses MYC gene expression.

    PubMed

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

    2014-01-01

    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. PMID:24299953

  19. 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. PMID:26001292

  20. SAGA Complex Components and Acetate Repression in Aspergillus nidulans

    PubMed Central

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

    2012-01-01

    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. PMID:23173087

  1. 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. PMID:23173087

  2. Catabolite repression in Escherichia coli. A study of two hypotheses

    PubMed Central

    Moses, V.; Yudkin, M. D.

    1968-01-01

    1. Two hypotheses to account for general catabolite repression of the lactose enzymes in Escherichia coli were tested: the dilution model of Palmer & Moses (1967), and the specific catabolite repressor model of Loomis & Magasanik (1965, 1967). 2. The dilution model predicts that in mutants lacking the i–o regulation system the differential rate of β-galactosidase synthesis should increase when amino acid-synthesizing enzymes are repressed by the presence of amino acids in the medium. It also predicts that with such mutants the total absence of Pi from the medium should not result in the complete cessation of β-galactosidase synthesis that is observed with wild-type cells. 3. Neither prediction was confirmed experimentally, and it is concluded that this model cannot explain catabolite repression. 4. The specific repressor hypothesis depends on the properties of a strain of E. coli carrying the CR− mutation. It requires both that cells of this genotype should be totally resistant to general catabolite repression and that this resistance should be specific for the lactose enzymes. 5. In fact the synthesis of β-galactosidase by CR− cells, though showing resistance to catabolite repression by growth on glucose, was found to be repressed in several other circumstances. 6. Two other inducible enzymes, l-tryptophanase and d-serine deaminase, also showed resistance to repression by glucose in CR− cells. 7. It is concluded that this model, too, does not account for general catabolite repression. 8. Strains carrying deletions at either end of the lactose operon that extend into the structural genes of the operon continue to exhibit catabolite repression. 9. These experiments appear to eliminate the possibility that catabolite repression operates at the level of DNA transcription, and suggest that repression affects instead the translation of messenger RNA into protein. PMID:4881142

  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. 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

  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. 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

  7. Polycomb repressive complex 1 controls uterine decidualization.

    PubMed

    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. SMRT isoforms mediate repression and anti-repression of nuclear receptor heterodimers.

    PubMed Central

    Chen, J D; Umesono, K; Evans, R M

    1996-01-01

    Transcriptional repression represents an important component in the regulation of cell differentiation and oncogenesis mediated by nuclear hormone receptors. Hormones act to relieve repression, thus allowing receptors to function as transcriptional activators. The transcriptional corepressor SMRT was identified as a silencing mediator for retinoid and thyroid hormone receptors. SMRT is highly related to another corepressor, N-CoR, suggesting the existence of a new family of receptor-interacting proteins. We demonstrate that SMRT is a ubiquitous nuclear protein that interacts with unliganded receptor heterodimers in mammalian cells. Furthermore, expression of the receptor-interacting domain of SMRT acts as an antirepressor, suggesting the potential importance of splicing variants as modulators of thyroid hormone and retinoic acid signaling. Images Fig. 1 Fig. 2 Fig. 4 Fig. 5 PMID:8755515

  9. JAZ8 Lacks a Canonical Degron and Has an EAR Motif That Mediates Transcriptional Repression of Jasmonate Responses in Arabidopsis[C][W

    PubMed Central

    Shyu, Christine; Figueroa, Pablo; DePew, Cody L.; Cooke, Thomas F.; Sheard, Laura B.; Moreno, Javier E.; Katsir, Leron; Zheng, Ning; Browse, John; Howe, Gregg A.

    2012-01-01

    The lipid-derived hormone jasmonoyl-l-Ile (JA-Ile) initiates large-scale changes in gene expression by stabilizing the interaction of JASMONATE ZIM domain (JAZ) repressors with the F-box protein CORONATINE INSENSITIVE1 (COI1), which results in JAZ degradation by the ubiquitin-proteasome pathway. Recent structural studies show that the JAZ1 degradation signal (degron) includes a short conserved LPIAR motif that seals JA-Ile in its binding pocket at the COI1-JAZ interface. Here, we show that Arabidopsis thaliana JAZ8 lacks this motif and thus is unable to associate strongly with COI1 in the presence of JA-Ile. As a consequence, JAZ8 is stabilized against jasmonate (JA)-mediated degradation and, when ectopically expressed in Arabidopsis, represses JA-regulated growth and defense responses. These findings indicate that sequence variation in a hypervariable region of the degron affects JAZ stability and JA-regulated physiological responses. We also show that JAZ8-mediated repression depends on an LxLxL-type EAR (for ERF-associated amphiphilic repression) motif at the JAZ8 N terminus that binds the corepressor TOPLESS and represses transcriptional activation. JAZ8-mediated repression does not require the ZIM domain, which, in other JAZ proteins, recruits TOPLESS through the EAR motif–containing adaptor protein NINJA. These findings show that EAR repression domains in a subgroup of JAZ proteins repress gene expression through direct recruitment of corepressors to cognate transcription factors. PMID:22327740

  10. Regulation of Peripheral Nerve Myelin Maintenance by Gene Repression through Polycomb Repressive Complex 2.

    PubMed

    Ma, Ki H; Hung, Holly A; Srinivasan, Rajini; Xie, Huafeng; Orkin, Stuart H; Svaren, John

    2015-06-01

    Myelination of peripheral nerves by Schwann cells requires coordinate regulation of gene repression as well as gene activation. Several chromatin remodeling pathways critical for peripheral nerve myelination have been identified, but the functions of histone methylation in the peripheral nerve have not been elucidated. To determine the role of histone H3 Lys27 methylation, we have generated mice with a Schwann cell-specific knock-out of Eed, which is an essential subunit of the polycomb repressive complex 2 (PRC2) that catalyzes methylation of histone H3 Lys27. Analysis of this mutant revealed no significant effects on early postnatal development of myelin. However, its loss eventually causes progressive hypermyelination of small-diameter axons and apparent fragmentation of Remak bundles. These data identify the PRC2 complex as an epigenomic modulator of mature myelin thickness, which is associated with changes in Akt phosphorylation. Interestingly, we found that Eed inactivation causes derepression of several genes, e.g., Sonic hedgehog (Shh) and Insulin-like growth factor-binding protein 2 (Igfbp2), that become activated after nerve injury, but without activation of a primary regulator of the injury program, c-Jun. Analysis of the activated genes in cultured Schwann cells showed that Igfbp2 regulates Akt activation. Our results identify an epigenomic pathway required for establishing thickness of mature myelin and repressing genes that respond to nerve injury. PMID:26041929

  11. 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

  12. Recovered-memory therapy and robust repression: influence and pseudomemories.

    PubMed

    Ofshe, R J; Singer, M T

    1994-10-01

    A subset of the psychotherapists practicing trauma-focused therapy predicate their treatment on the existence of a newly claimed, powerful form of repression that differs from repression as used in the psychoanalytic tradition and from amnesia in any of its recognized forms. Recovered-memory specialists assist patients to supposedly retrieve vast quantities of information (e.g., utterly new dramatic life histories) that were allegedly unavailable to consciousness for years or decades. We refer to the hypothesized mental mechanism as "robust repression" and call attention to the absence of evidence documenting its validity and to the differences between it and other mental mechanisms and memory features. No recovered-memory practitioner has ever published a full specification of the attributes of this mechanism. That is, the properties it would have to have for the narratives developed during therapy to be historically accurate to any significant degree. This article reports a specification of the properties of the robust repression mechanism based on interviews with current and former patients, practitioners' writings, and reports to researchers and clinicians. The spread of reliance on the robust repression mechanism over the past 20 years through portions of the clinical community is traced. While involved in therapy, patients of recovered-memory practitioners come to believe that they have either instantly repressed large numbers of discrete events or simultaneously repressed all information about abuse they may have endured for as long as a decade.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7960294

  13. 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

  14. Pseudocatabolite repression of type 1 fimbriae of Escherichia coli.

    PubMed

    Eisenstein, B I; Dodd, D C

    1982-09-01

    Previous work on the control of fimbriation in bacteria has demonstrated the importance of environmental factors such as static versus shaking broth and the absence versus the presence of glucose on the degree of fimbriation. When the Pil+ K-12 strain of Escherichia coli CSH50 was grown in static broth, the bacteria grown with glucose were less fimbriate (as determined by electron microscopy) than those grown without glucose. In contrast, a derivative, the pil-lac operon fusion strain VL361, gave off similar proportions of Lac+ and Lac- colonies when grown with or without glucose. Introduction of delta cya into either CSH50 or VL361 did not affect synthesis of either fimbriae or beta-galactosidase, respectively. When total synthesis of fimbriae by strain CSH50 was assayed, using an enzyme-linked immunosorbent inhibition test, glucose-grown bacteria made less antigen when they were grown in static broth but not when they were grown in shaking broth. When results are taken together, we interpret them as showing that glucose does not suppress fimbrial synthesis by classic catabolite repression but rather merely prevents the outgrowth or fimbriate bacteria in static broth. PMID:6125501

  15. Glycerol-3-Phosphate-Induced Catabolite Repression in Escherichia coli

    PubMed Central

    Eppler, Tanja; Postma, Pieter; Schütz, Alexandra; Völker, Uwe; Boos, Winfried

    2002-01-01

    The formation of glycerol-3-phosphate (G3P) in cells growing on TB causes catabolite repression, as shown by the reduction in malT expression. For this repression to occur, the general proteins of the phosphoenolpyruvate-dependent phosphotransferase system (PTS), in particular EIIAGlc, as well as the adenylate cyclase and the cyclic AMP-catabolite activator protein system, have to be present. We followed the level of EIIAGlc phosphorylation after the addition of glycerol or G3P. In contrast to glucose, which causes a dramatic shift to the dephosphorylated form, glycerol or G3P only slightly increased the amount of dephosphorylated EIIAGlc. Isopropyl-β-d-thiogalactopyranoside-induced overexpression of EIIAGlc did not prevent repression by G3P, excluding the possibility that G3P-mediated catabolite repression is due to the formation of unphosphorylated EIIAGlc. A mutant carrying a C-terminally truncated adenylate cyclase was no longer subject to G3P-mediated repression. We conclude that the stimulation of adenylate cyclase by phosphorylated EIIAGlc is controlled by G3P and other phosphorylated sugars such as d-glucose-6-phosphate and is the basis for catabolite repression by non-PTS compounds. Further metabolism of these compounds is not necessary for repression. Two-dimensional polyacrylamide gel electrophoresis was used to obtain an overview of proteins that are subject to catabolite repression by glycerol. Some of the prominently repressed proteins were identified by peptide mass fingerprinting. Among these were periplasmic binding proteins (glutamine and oligopeptide binding protein, for example), enzymes of the tricarboxylic acid cycle, aldehyde dehydrogenase, Dps (a stress-induced DNA binding protein), and d-tagatose-1,6-bisphosphate aldolase. PMID:12003946

  16. 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

  17. 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

  18. YB-1 regulates tiRNA-induced Stress Granule formation but not translational repression.

    PubMed

    Lyons, Shawn M; Achorn, Chris; Kedersha, Nancy L; Anderson, Paul J; Ivanov, Pavel

    2016-08-19

    Stress-induced angiogenin (ANG)-mediated tRNA cleavage promotes a cascade of cellular events that starts with production of tRNA-derived stress-induced RNAs (tiRNAs) and culminates with enhanced cell survival. This stress response program relies on a subset tiRNAs that inhibit translation initiation and induce the assembly of stress granules (SGs), cytoplasmic ribonucleoprotein complexes with cytoprotective and pro-survival properties. SG-promoting tiRNAs bear oligoguanine motifs at their 5'-ends, assemble G-quadruplex-like structures and interact with the translational silencer YB-1. We used CRISPR/Cas9-based genetic manipulations and biochemical approaches to examine the role of YB-1 in tiRNA-mediated translational repression and SG assembly. We found that YB-1 directly binds to tiRNAs via its cold shock domain. This interaction is required for packaging of tiRNA-repressed mRNAs into SGs but is dispensable for tiRNA-mediated translational repression. Our studies reveal the functional role of YB-1 in the ANG-mediated stress response program. PMID:27174937

  19. 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.

  20. 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

  1. 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. PMID:26430118

  2. Bile Acids Repress Hypoxia-Inducible Factor 1 Signaling and Modulate the Airway Immune Response

    PubMed Central

    Legendre, Claire; Reen, F. Jerry; Woods, David F.; Mooij, Marlies J.; Adams, Claire

    2014-01-01

    Gastroesophageal reflux (GER) frequently occurs in patients with respiratory disease and is particularly prevalent in patients with cystic fibrosis. GER is a condition in which the duodenogastric contents of the stomach leak into the esophagus, in many cases resulting in aspiration into the respiratory tract. As such, the presence of GER-derived bile acids (BAs) has been confirmed in the bronchoalveolar lavage fluid and sputum of affected patients. We have recently shown that bile causes cystic fibrosis-associated bacterial pathogens to adopt a chronic lifestyle and may constitute a major host trigger underlying respiratory infection. The current study shows that BAs elicit a specific response in humans in which they repress hypoxia-inducible factor 1α (HIF-1α) protein, an emerging master regulator in response to infection and inflammation. HIF-1α repression was shown to occur through the 26S proteasome machinery via the prolyl hydroxylase domain (PHD) pathway. Further analysis of the downstream inflammatory response showed that HIF-1α repression by BAs can significantly modulate the immune response of airway epithelial cells, correlating with a decrease in interleukin-8 (IL-8) production, while IL-6 production was strongly increased. Importantly, the effects of BAs on cytokine production can also be more dominant than the bacterium-mediated effects. However, the effect of BAs on cytokine levels cannot be fully explained by their ability to repress HIF-1α, which is not surprising, given the complexity of the immune regulatory network. The suppression of HIF-1 signaling by bile acids may have a significant influence on the progression and outcome of respiratory disease, and the molecular mechanism underpinning this response warrants further investigation. PMID:24914220

  3. Gene expression in self-repressing system with multiple gene copies.

    PubMed

    Miekisz, Jacek; Szymańska, Paulina

    2013-02-01

    We analyze a simple model of a self-repressing system with multiple gene copies. Protein molecules may bound to DNA promoters and block their own transcription. We derive analytical expressions for the variance of the number of protein molecules in the stationary state in the self-consistent mean-field approximation. We show that the Fano factor (the variance divided by the mean value) is bigger for the one-gene case than for two gene copies and the difference decreases to zero as frequencies of binding and unbinding increase to infinity. PMID:23354928

  4. Androgen Receptor Repression of GnRH Gene Transcription

    PubMed Central

    Brayman, Melissa J.; Pepa, Patricia A.; Berdy, Sara E.

    2012-01-01

    Alterations in androgen levels lead to reproductive defects in both males and females, including hypogonadotropic hypogonadism, anovulation, and infertility. Androgens have been shown to down-regulate GnRH mRNA levels through an androgen receptor (AR)-dependent mechanism. Here, we investigate how androgen regulates expression from the GnRH regulatory region in the GT1-7 cell line, a model of GnRH neurons. A synthetic androgen, R1881, repressed transcription from the GnRH promoter (GnRH-P) in an AR-dependent manner, and liganded AR associated with the chromatin at the GnRH-P in live GT1-7 cells. The three known octamer-binding transcription factor-1 (Oct-1) binding sites in GnRH-P were required for AR-mediated repression, although other sequences were also involved. Although a multimer of the consensus Oct-1 binding site was not repressed, a multimer of the cluster of Oct-1, Pre-B cell leukemia transcription factor (Pbx)/Prep, and NK2 homeobox 1 (Nkx2.1) binding sites, found at −106/−91 in GnRH-P, was sufficient for repression. In fact, overexpression of any of these factors disrupted the androgen response, indicating that a balance of factors in this tripartite complex is required for AR repression. AR bound to this region in EMSA, indicating a direct interaction of AR with DNA or with other transcription factors bound to GnRH-P at this sequence. Collectively, our data demonstrate that GnRH transcription is repressed by AR via multiple sequences in GnRH-P, including three Oct-1 binding sites, and that this repression requires the complex interaction of several transcription factors. PMID:22074952

  5. Induction, production, repression, and de-repression of exoglucanase synthesis in Aspergillus niger.

    PubMed

    Hanif, Atif; Yasmeen, Amber; Rajoka, M I

    2004-09-01

    The influence of carbon and nitrogen sources on the production of cellulases was investigated. The enzyme production was variable according to the carbon source. Levels of beta-cellobiohydrolase (CBH) were minimal in the presence of even low concentrations of glucose. Enzyme production was stimulated by other carbohydrates. The enzyme is subject to carbon source control by easily metabolizable sugars. Wheat bran and cellulose were the most effective promoters of beta-cellobiohydrolase and filter paperase (FPase) activities respectively, followed by rice bran. Exogenously supplied glucose inhibited the synthesis of the enzyme in cultures of A. niger growing on wheat bran. In defined medium with cellobiose, the cellobiohydrolase titres were 2- to 110-fold higher with cells growing on monomeric sugars and 1.5 times higher than cells growing on other disaccharides. It appeared that synthesis of beta-cellobiohydrolase varied under an induction mechanism, and a repression mechanism which changed the rate of synthesis of beta-cellobiohydrolase and FPase in induced over non-induced cultures. In this organism, substantial synthesis of beta-cellobiohydrolase can be induced by cellobiose, cellodextrin, cellulose or cellulose and hemi-cellulose containing substrates which showed low volumetric substrate uptake rate. The organism required limiting concentration of carbon, nitrogen or phosphorous for production of beta-cellobiohydrolase and FPase. During growth of A. niger on wheat bran, maximum volumetric productivities (Qp) of beta-cellobiohydrolase and FPase were 39.6 and 32.5 IU/lh and were significantly higher than the values reported for some other potent fungi and bacteria. The addition of actinomycin D (a repressor of transcription) and cycloheximide, (a repressor of translation) completely repressed CBH/FPase biosynthesis, suggested that the regulation of CBH synthesis in this organism occurs at both transcriptional and translational level. Thermodynamic studies

  6. 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

  7. 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

  8. Rhizobacteria of Cotton and Their Repression of Seedling Disease Pathogens

    PubMed Central

    Hagedorn, C.; Gould, W. D.; Bardinelli, T. R.

    1989-01-01

    During the 1983 field season, the rhizobacteria (including organisms from rhizosphere soil and the root rhizoplane) of cotton plants at one location in Mississippi were inventoried at different plant growth stages. Isolates (1,000) were identified to the genus level and characterized for repression of Pythium ultimum and Rhizoctonia solani. Cotton seedlings were initially colonized by bacteria of many different genera, and populations quickly reached 108 CFU/g of root tissue. As the season progressed, the bacterial populations declined as root mass increased and the roots became more woodlike in consistency. Fluorescent pseudomonads were the most numerous gram-negative rhizobacterial isolates of those that were randomly collected and identified, and they provided the largest number of isolates with fungal repressive activity. Several other gram-negative bacterial genera were recovered throughout the growing season, and some gram-positive bacteria were also isolated routinely, but at lower numbers. There was no correlation between the proportion of rhizobacterial isolates that possessed fungal repressive activity and the plant growth stage from which the isolates were obtained. Approximately twice as many bacterial isolates demonstrated fungal repression in the agar assay compared with the inplanta assay, and isolates were found more frequently with fungal repressive activity against P. ultimum than against R. solai. PMID:16348043

  9. Reduced specificity of negative autobiographical memories in repressive coping.

    PubMed

    Geraerts, Elke; Dritschel, Barbara; Kreplin, Ute; Miyagawa, Liv; Waddington, Joanne

    2012-12-01

    The current study examined memory specificity of autobiographical memories in individuals with and without a repressive coping style. It seems conceivable that reduced memory specificity may be a way to reduce accessibility of negative experiences, one of the hallmark features of a repressive coping style. It was therefore hypothesized that repressors would show reduced specificity when retrieving negative memories. In order to study memory specificity, participants (N = 103) performed the autobiographical memory test. Results showed that individuals with a repressive coping style were significantly less specific in retrieving negative experiences, relative to control groups of low anxious, high anxious, and defensive high anxious individuals. This result was restricted to negative memory retrieval, as participants did not differ in memory specificity for positive experiences. These results show that repressors retrieve negative autobiographical memories in an overgeneral way, possibly in order to avoid negative affect. PMID:23200428

  10. Repression-sensitization, stress, and perception of pain in others.

    PubMed

    Von Baeyer, C

    1982-08-01

    To assess the influence of individuals' defensive style on perception of pain in others, 60 undergraduate women rated the amount of pain expressed in slides of people displaying high or low pain. Subjects were categorized as high or low on Byrne's Repression-Sensitization Scale, and their level of stress was varied by presentation of an anxiety-provoking film (stress condition) or a neutral film (control condition) prior to the rating task. A significant interaction between Repression-Sensitization and slide category (high versus low pain) indicated that sensitizers assigned higher ratings of pain than repressers to slides that were relatively low in rated expressiveness of pain. Individual differences in readiness to recognize potentially threatening stimuli seem most evident when the stimuli are relatively ambiguous. The manipulation of stress produced no significant effects on ratings of pain. PMID:7133920

  11. Pleiotropic Properties of a Yeast Mutant Insensitive to Catabolite Repression

    PubMed Central

    Stark, Helene Cherrick; Fugit, Donna; Mowshowitz, Deborah Bernhardt

    1980-01-01

    The flk1 mutation, which was originally isolated in the yeast Saccharomyces carlsbergenesis, causes insensitivity to catabolite repression. This mutation has been further characterized and mapped. The gene flk1 is located on chromosome III between thr4 and MAL2, 14 centimorgans from MAL2. flk1 is shown to be allelic to the pleiotropic mutants tup1, cyc9, and umr7; and flk1 is shown to exhibit an array of pleiotropic properties common to tup1, cyc9 and umr7; These results suggest that the flk1 mutation is not a specific lesion affecting catabolite repression. PMID:17249023

  12. DNA methylation in transcriptional repression of two differentially expressed X-linked genes, GPC3 and SYBL1

    PubMed Central

    Huber, Reid; Hansen, R. Scott; Strazzullo, Maria; Pengue, Gina; Mazzarella, Richard; D’Urso, Michele; Schlessinger, David; Pilia, Giuseppe; Gartler, Stanley M.; D’Esposito, Maurizio

    1999-01-01

    Methylation of CpG islands is an established transcriptional repressive mechanism and is a feature of silencing in X chromosome inactivation. Housekeeping genes that are subject to X inactivation exhibit differential methylation of their CpG islands such that the inactive alleles are hypermethylated. In this report, we examine two contrasting X-linked genes with CpG islands for regulation by DNA methylation: SYBL1, a housekeeping gene in the Xq pseudoautosomal region, and GPC3, a tissue-specific gene in Xq26 that is implicated in the etiology of the Simpson–Golabi–Behmel overgrowth syndrome. We observed that in vitro methylation of either the SYBL1 or the GPC3 promoter resulted in repression of reporter constructs. In normal contexts, we found that both the Y and inactive X alleles of SYBL1 are repressed and hypermethylated, whereas the active X allele is expressed and unmethylated. Furthermore, the Y and inactive X alleles of SYBL1 were derepressed by treatment with the demethylating agent azadeoxycytidine. GPC3 is also subject to X inactivation, and the active X allele is unmethylated in nonexpressing leukocytes as well as in an expressing cell line, suggesting that methylation is not involved in the tissue-specific repression of this allele. The inactive X allele, however, is hypermethylated in leukocytes, presumably reflecting early X inactivation events that become important for gene dosage in expressing lineages. These and other data suggest that all CpG islands on Xq, including the pseudoautosomal region, are subject to X inactivation-induced methylation. Additionally, methylation of SYBL1 on Yq may derive from a process related to X inactivation that targets large chromatin domains for transcriptional repression. PMID:9892682

  13. 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

  14. Selection of suitably non-repressing carbon sources for expression of alcohol oxidase isozyme promoters in the methylotrophic yeast Pichia methanolica.

    PubMed

    Nakagawa, Tomoyuki; Wakayama, Keishi; Hayakawa, Takashi

    2015-07-01

    In this work, we aimed to select suitable non-repressing carbon sources for the expression of promoters derived from the alcohol oxidase (AOD) isozyme genes, PMOD1 and PMOD2, during the growth of Pichia methanolica. Our results revealed that xylose is the best non-repressing carbon source for heterologous gene expression using both PMOD1 and PMOD2, and that glycerol is also a suitable carbon source with by which the on/off of PMOD2 expression can be controlled. PMID:25561326

  15. 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…

  16. 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

  17. Addressing the repressed needs of the Arabic client.

    PubMed

    Dwairy, M

    1997-01-01

    In comparison to families in Western society, the traditional Arabic family plays a relatively greater role in providing support for adult progeny. This serves to condition adult offspring to continue to comply with the will and values of the family. Therefore, in exchange for familial support, Arabic individuals learn to repress authentic needs and emotions, and within that process they relinquish the need for self-actualization. Arabic society discourages individualism and opposes self-actualization by means of simultaneous punishment and moralization. Thus, there is a relatively greater development of the social value system (or superego) and comparatively less development of the self (or ego). In comparison to Western society, Arabic individuals continue to experience greater oppression during adulthood. Given these cultural differences, the processes of reliving and activating repressed needs and emotions, which ultimately serves to promote self-actualization, will transform intrapsychic conflicts into interpersonal and social ones. Thus, personal actions typically encouraged during Western psychotherapy are likely to produce significant social oppression. Indeed, promoting awareness of repressed needs and emotions often leads the Arabic client to become more helpless, because such wishes will rarely be socially sanctioned or satisfactorily fulfilled. Therefore, when addressing repressed needs and emotions in psychotherapy, ego strength, cultural identity, and degree of strictness of the client's family of origin must be considered. PMID:9231529

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

    PubMed

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

    2015-01-01

    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. PMID:25966269

  19. 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.…

  20. Repression of apical homeobox genes is required for embryonic root development in Arabidopsis.

    PubMed

    Grigg, Stephen P; Galinha, Carla; Kornet, Noortje; Canales, Claudia; Scheres, Ben; Tsiantis, Miltos

    2009-09-15

    Development of seed plant embryos is polarized along the apical-basal axis. This polarization occurs in the absence of cell migration and culminates in the establishment of two distinct pluripotent cell populations: the shoot apical meristem (SAM) and root meristem (RM), which postembryonically give rise to the entire shoot and root systems of the plant. The acquisition of genetic pathways that delimit root from shoot during embryogenesis must have played a pivotal role during land plant evolution because roots evolved after shoots in ancestral vascular plants and may be shoot-derived organs. However, such pathways are very poorly understood. Here we show that RM establishment in the model plant Arabidopsis thaliana requires apical confinement of the Class III HOMEODOMAIN-LEUCINE ZIPPER (HD-ZIP III) proteins PHABULOSA (PHB) and PHAVOLUTA (PHV), which direct both SAM development and shoot lateral organ polarity. Failure to restrict PHB and PHV expression apically via a microRNA-dependent pathway prevents correct elaboration of the embryonic root development program and results in embryo lethality. As such, repression of a fundamental shoot development pathway is essential for correct root development. Additionally, our data suggest that a single patterning process, based on HD-ZIP III repression, mediates both apical-basal and radial polarity in the embryo and lateral organ polarity in the shoot. PMID:19646874

  1. 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

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

    PubMed

    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

  3. 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

  4. 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

  5. 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

  6. Repression of harmful meiotic recombination in centromeric regions.

    PubMed

    Nambiar, Mridula; Smith, Gerald R

    2016-06-01

    During the first division of meiosis, segregation of homologous chromosomes reduces the chromosome number by half. In most species, sister chromatid cohesion and reciprocal recombination (crossing-over) between homologous chromosomes are essential to provide tension to signal proper chromosome segregation during the first meiotic division. Crossovers are not distributed uniformly throughout the genome and are repressed at and near the centromeres. Rare crossovers that occur too near or in the centromere interfere with proper segregation and can give rise to aneuploid progeny, which can be severely defective or inviable. We review here how crossing-over occurs and how it is prevented in and around the centromeres. Molecular mechanisms of centromeric repression are only now being elucidated. However, rapid advances in understanding crossing-over, chromosome structure, and centromere functions promise to explain how potentially deleterious crossovers are avoided in certain chromosomal regions while allowing beneficial crossovers in others. PMID:26849908

  7. Repression predicts outcome following multidisciplinary treatment of chronic pain.

    PubMed

    Burns, J W

    2000-01-01

    This study examined whether repression predicts outcome following multidisciplinary treatment for chronic pain and whether links between anxiety and outcome are obscured by repressors. Ninety-three chronic pain patients completed a 4-week pain program. Lifting capacity, walking endurance, depression, pain severity, and activity were measured at pre- and posttreatment. Low-anxious, repressor, high-anxious, and defensive/high-anxious groups were formed from median splits of Anxiety Content (ACS) and Lie scales of the Minnesota Multiphasic Personality Inventory-2 (MMPI-2; Butcher, Dahlstrom, Graham, Tellegen, & Kaemmer, 1989). Significant ACS x Lie interactions were found for lifting capacity, depression, and pain severity changes. Planned comparisons showed that both repressors and high-anxious patients performed poorly on lifting capacity; repressors alone recovered poorly on depression and pain severity. Results imply that repression may interfere with the process and outcome of pain programs. PMID:10711590

  8. 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

  9. Carbon catabolite repression of maltase synthesis in Saccharomyces carlsbergensis.

    PubMed Central

    Federoff, H J; Eccleshall, T R; Marmur, J

    1983-01-01

    Carbon catabolite repression of maltase gene expression is brought about by the addition of glucose, resulting in a drastic inhibition of the induction of maltase. When added to induced cells, glucose leads to the inhibition of maltase synthesis within 30 min, which can be accounted for by the disappearance of hybridizable maltase RNA sequences. The loss of maltase-specific RNA due to catabolite repression can be traced to the combined effects of a 15-fold decrease in the rate of transcription of the maltase structural gene 15 to 20 min after the addition of glucose and a change in the half-life of maltase mRNA. However, the stability of maltase, once induced, is not affected by the addition of glucose. Images PMID:6352680

  10. Notochord repression of endodermal Sonic hedgehog permits pancreas development

    PubMed Central

    Hebrok, Matthias; Kim, Seung K.; Melton, Douglas A.

    1998-01-01

    Notochord signals to the endoderm are required for development of the chick dorsal pancreas. Sonic hedgehog (SHH) is normally absent from pancreatic endoderm, and we provide evidence that notochord, in contrast to its effects on adjacent neuroectoderm where SHH expression is induced, represses SHH expression in adjacent nascent pancreatic endoderm. We identify activin-βB and FGF2 as notochord factors that can repress endodermal SHH and thereby permit expression of pancreas genes including Pdx1 and insulin. Endoderm treatment with antibodies that block hedgehog activity also results in pancreatic gene expression. Prevention of SHH expression in prepancreatic dorsal endoderm by intercellular signals, like activin and FGF, may be critical for permitting early steps of chick pancreatic development. PMID:9620856

  11. 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

  12. Rest represses maturation within migrating facial branchiomotor neurons

    PubMed Central

    Love, Crystal E.; Prince, Victoria E.

    2015-01-01

    The vertebrate brain arises from the complex organization of millions of neurons. Neurogenesis encompasses not only cell fate specification from neural stem cells, but also the terminal molecular and morphological maturation of neurons at correct positions within the brain. RE1-silencing transcription factor (Rest) is expressed in non-neural tissues and neuronal progenitors where it inhibits the terminal maturation of neurons by repressing hundreds of neuron-specific genes. Here we show that Rest repression of maturation is intimately linked with the migratory capability of zebrafish facial branchiomotor neurons (FBMNs), which undergo a characteristic tangential migration from hindbrain rhombomere (r) 4 to r6/r7 during development. We establish that FBMN migration is increasingly disrupted as Rest is depleted in zebrafish rest mutant embryos, such that around two-thirds of FBMNs fail to complete migration in mutants depleted of both maternal and zygotic Rest. Although Rest is broadly expressed, we show that de-repression or activation of Rest target genes only within FBMNs is sufficient to disrupt their migration. We demonstrate that this migration defect is due to precocious maturation of FBMNs, based on both morphological and molecular criteria. We further show that the Rest target gene and alternative splicing factor srrm4 is a key downstream regulator of maturation; Srrm4 knockdown partially restores the ability of FBMNs to migrate in rest mutants while preventing their precocious morphological maturation. Rest must localize to the nucleus to repress its targets, and its subcellular localization is highly regulated: we show that targeting Rest specifically to FBMN nuclei rescues FBMN migration in Rest-deficient embryos. We conclude that Rest functions in FBMN nuclei to inhibit maturation until the neurons complete their migration. PMID:25769695

  13. 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

  14. 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

  15. 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

  16. 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. PMID:26686089

  17. ERalpha suppresses slug expression directly by transcriptional repression.

    PubMed

    Ye, Yin; Xiao, Yi; Wang, Wenting; Yearsley, Kurtis; Gao, Jian-Xin; Barsky, Sanford H

    2008-12-01

    Two of the most common signalling pathways in breast cancer are the ER (oestrogen receptor) ligand activation pathway and the E-cadherin snai1 slug EMT (epithelial-mesenchymal transition) pathway. Although these pathways have been thought to interact indirectly, the present study is the first to observe direct interactions between these pathways that involves the regulation of slug expression. Specifically we report that ligand-activated ERalpha suppressed slug expression directly by repression of transcription and that knockdown of ERalpha with RNA interference increased slug expression. More specifically, slug expression was down-regulated in ERalpha-negative MDA-MB-468 cells transfected with ERalpha after treatment with E2 (17beta-oestradiol). The down-regulation of slug in the ERalpha-positive MCF-7 cell line was mediated by direct repression of slug transcription by the formation of a co-repressor complex involving ligand-activated ERalpha protein, HDAC1 (histone deacetylase 1) and N-CoR (nuclear receptor co-repressor). This finding was confirmed by sequential ChIP (chromatin immunoprecipitation) studies. In the MCF-7 cell line, slug expression normally was low. In addition, knockdown of ERalpha with RNA interference in this cell line increased slug expression. This effect could be partially reversed by treatment of the cells with E2. The efficacy of the effect of ERalpha on slug repression was dependent on the overall level of ERalpha. These observations confirmed that slug was an E2-responsive gene. PMID:18588516

  18. 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

  19. 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

  20. Tgif1 represses apolipoprotein gene expression in liver

    PubMed Central

    Melhuish, Tiffany A.; Chung, David D.; Bjerke, Glen A.; Wotton, David

    2010-01-01

    Tgif1 (TG-interacting factor) represses gene expression by interaction with general corepressors, and can be recruited to target genes by transforming growth factor beta (TGFβ) activated Smads, or by the retinoid X receptor (RXR). Here we show that Tgif1 interacts with the LXRα nuclear receptor and can repress transcription from a synthetic reporter activated by LXRα. In cultured cells reducing endogenous Tgif1 levels resulted in increased expression of LXRα target genes. To test the in vivo role of Tgif1, we analyzed LXRα dependent gene expression in mice lacking Tgif1. In the livers of Tgif1 null mice, we observed significant derepression of the apolipoprotein genes, Apoa4 and Apoc2, suggesting that Tgif1 is an important in vivo regulator of apolipoprotein gene expression. In contrast, we observed relatively minimal effects on expression of other LXR target genes. This work suggests that Tgif1 can regulate nuclear receptor complexes, in addition to those containing retinoic acid receptors, but also indicates that there is some specificity to which NR target genes are repressed by Tgif1. PMID:20506222

  1. Glucocorticoid and TNF signaling converge at A20 (TNFAIP3) to repress airway smooth muscle cytokine expression.

    PubMed

    Sasse, Sarah K; Altonsy, Mohammed O; Kadiyala, Vineela; Cao, Gaoyuan; Panettieri, Reynold A; Gerber, Anthony N

    2016-08-01

    Airway smooth muscle is a major target tissue for glucocorticoid (GC)-based asthma therapies, however, molecular mechanisms through which the GC receptor (GR) exerts therapeutic effects in this key airway cell type have not been fully elucidated. We previously identified the nuclear factor-κB (NF-κB) inhibitor, A20 (TNFAIP3), as a mediator of cytokine repression by glucocorticoids (GCs) in airway epithelial cells and defined cooperative regulation of anti-inflammatory genes by GR and NF-κB as a key mechanistic underpinning of airway epithelial GR function. Here, we expand on these findings to determine whether a similar mechanism is operational in human airway smooth muscle (HASM). Using HASM cells derived from normal and fatal asthma samples as an in vitro model, we demonstrate that GCs spare or augment TNF-mediated induction of A20 (TNFAIP3), TNIP1, and NFKBIA, all implicated in negative feedback control of NF-κB-driven inflammatory processes. We applied chromatin immunoprecipitation and reporter analysis to show that GR and NF-κB directly regulate A20 expression in HASM through cooperative induction of an intronic enhancer. Using overexpression, we show for the first time that A20 and its interacting partner, TNIP1, repress TNF signaling in HASM cells. Moreover, we applied small interfering RNA-based gene knockdown to demonstrate that A20 is required for maximal cytokine repression by GCs in HASM. Taken together, our data suggest that inductive regulation of A20 by GR and NF-κB contributes to cytokine repression in HASM. PMID:27371733

  2. A new translational repression element and unusual transcriptional control regulate expression of don juan during Drosophila spermatogenesis.

    PubMed

    Blümer, Nicole; Schreiter, Kay; Hempel, Leonie; Santel, Ansgar; Hollmann, Martin; Schäfer, Mireille A; Renkawitz-Pohl, Renate

    2002-01-01

    The Drosophila don juan (dj) gene encodes a basic protein that is expressed solely in the male germline and shows structural similarities to the linker histone H1. Don Juan is located in two different subcellular structures: in the nucleus during the phase of chromatin condensation and later in the mitochondrial derivatives starting with spermatid individualization. The don juan gene is transcribed in primary spermatocytes under the control of 23 bp upstream in combination with downstream sequences. During meiotic stages and in early spermatid stages don juan mRNA is translationally repressed for several days. Analysis of male sterile mutants which fail to undergo meiosis shows that release of dj mRNA from translational repression is independent of meiosis. In gel retardation assays 60 nucleotides at the end of the dj leader form four major complexes with proteins that were extracted from testes but not with protein extracts from ovaries. Transformation studies prove that in vivo 35 bp within that region of the dj mRNA is essential to confer translational repression. UV cross-linking studies show that a 62 kDa protein specifically binds to the same region within the 5' untranslated region. The dj translational repression element, TRE, is distinct from the translational control element, TCE, described earlier for all members of the Mst(3)CGP gene family. Moreover, expression studies in several male sterile mutants reveal that don juan mRNA is translated in earlier developmental stages during sperm morphogenesis than the Mst(3)CGP mRNAs. This proves that translational activation of dormant mRNAs in spermatogenesis occurs at different time-points which are characteristic for each gene, an essential feature for coordinated sperm morphogenesis. PMID:11744372

  3. 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

  4. The relationship between repressive and defensive coping styles and monocyte, eosinophile, and serum glucose levels: support for the opioid peptide hypothesis of repression.

    PubMed

    Jamner, L D; Schwartz, G E; Leigh, H

    1988-01-01

    The opioid peptide hypothesis of repression (1) predicts that repressive coping is associated with increased functional endorphin levels in the brain, which can result in decreased immunocompetence and hyperglycemia. In a random sample of 312 patients seen at a Yale Medical School outpatient clinic, significant main effects of coping style were found for monocyte and eosinophile counts, serum glucose levels, and self-reports of medication allergies. Specifically, repressive and defensive high-anxious patients demonstrated significantly decreased monocyte counts. In addition, repressive coping was associated with elevated eosinophile counts, serum glucose levels, and self-reported reactions to medications. This behavioral, immunologic, and endocrine profile is consistent with the opioid peptide hypothesis, which provides an integrative framework for relating the attenuated emotional experience of pain and distress characteristic of repressive coping with reduced resistance to infectious and neoplastic disease. PMID:2853404

  5. Suppressors Reveal Two Classes of Glucose Repression Genes in the Yeast Saccharomyces Cerevisiae

    PubMed Central

    Erickson, J. R.; Johnston, M.

    1994-01-01

    We selected and analyzed extragenic suppressors of mutations in four genes-GRR1, REG1, GAL82 and GAL83-required for glucose repression of the GAL genes in the yeast Saccharomyces cerevisiae. The suppressors restore normal or nearly normal glucose repression of GAL1 expression in these glucose repression mutants. Tests of the ability of each suppressor to cross-suppress mutations in the other glucose repression genes revealed two groups of mutually cross-suppressed genes: (1) REG1, GAL82 and GAL83 and (2) GRR1. Mutations of a single gene, SRG1, were found as suppressors of reg1, GAL83-2000 and GAL82-1, suggesting that these three gene products act at a similar point in the glucose repression pathway. Mutations in SRG1 do not cross-suppress grr1 or hxk2 mutations. Conversely, suppressors of grr1 (rgt1) do not cross-suppress any other glucose repression mutation tested. These results, together with what was previously known about these genes, lead us to propose a model for glucose repression in which Grr1p acts early in the glucose repression pathway, perhaps affecting the generation of the signal for glucose repression. We suggest that Reg1p, Gal82p and Gal83p act after the step(s) executed by Grr1p, possibly transmitting the signal for repression to the Snf1p protein kinase. PMID:8013904

  6. NPAS1 Represses the Generation of Specific Subtypes of Cortical Interneurons

    PubMed Central

    Stanco, Amelia; Pla, Ramón; Vogt, Daniel; Chen, Yiran; Mandal, Shyamali; Walker, Jamie; Hunt, Robert F.; Lindtner, Susan; Erdman, Carolyn A.; Pieper, Andrew A.; Hamilton, Steven P.; Xu, Duan; Baraban, Scott C.; Rubenstein, John L. R.

    2014-01-01

    Summary Little is known about genetic mechanisms that regulate the ratio of cortical excitatory and inhibitory neurons. We show that NPAS1 and NPAS3 transcription factors (TF) are expressed in progenitor domains of the mouse basal ganglia (subpallium, MGE and CGE). NPAS1−/− mutants had increased proliferation, ERK signaling and expression of Arx in the MGE and CGE. NPAS1−/− mutants also had increased neocortical inhibition (sIPSC and mIPSC), and generated an excess of somatostatin+ (SST) (MGE-derived) and vasoactive intestinal polypeptide+ (VIP) (CGE-derived) neocortical interneurons, but had a normal density of parvalbumin+ (PV) (MGE-derived) interneurons. In contrast, NPAS3−/− mutants showed decreased proliferation and ERK signaling in progenitors of the ganglionic eminences and had fewer SST+ and VIP+ interneurons. NPAS1 repressed activity of an Arx enhancer, and Arx over-expression resulted in increased proliferation of CGE progenitors. These results provide novel insights into genetic regulation of cortical interneuron numbers and cortical inhibitory tone. PMID:25467980

  7. Thrombospondin-1 is a transcriptional repression target of PRMT6.

    PubMed

    Michaud-Levesque, Jonathan; Richard, Stéphane

    2009-08-01

    Protein arginine methyltransferase 6 (PRMT6) is known to catalyze the generation of asymmetric dimethylarginine in polypeptides. Although the cellular role of PRMT6 is not well understood, it has been implicated in human immunodeficiency virus pathogenesis, DNA repair, and transcriptional regulation. PRMT6 is known to methylate histone H3 Arg-2 (H3R2), and this negatively regulates the lysine methylation of H3K4 resulting in gene repression. To identify in a nonbiased manner genes regulated by PRMT6 expression, we performed a microarray analysis on U2OS osteosarcoma cells transfected with control and PRMT6 small interfering RNAs. We identified thrombospondin-1 (TSP-1), a potent natural inhibitor of angiogenesis, as a transcriptional repression target of PRMT6. Moreover, we show that PRMT6-deficient U2OS cells exhibited cell migration defects that were rescued by blocking the secreted TSP-1 with a neutralizing peptide or blocking alpha-TSP-1 antibody. PRMT6 associates with the TSP-1 promoter and regulates the balance of methylation of H3R2 and H3K4, such that in PRMT6-deficient cells H3R2 was hypomethylated and H3K4 was trimethylated at the TSP-1 promoter. Using a TSP-1 promoter reporter gene, we further show that PRMT6 directly regulates the TSP-1 promoter activity. These findings show that TSP-1 is a transcriptional repression target of PRMT6 and suggest that neutralizing the activity of PRMT6 could inhibit tumor progression and therefore may be of cancer therapeutic significance. PMID:19509293

  8. 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

  9. 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.

  10. 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

  11. Histone acetylation: a switch between repressive and permissive chromatin

    PubMed Central

    Eberharter, Anton; Becker, Peter B.

    2002-01-01

    The organization of eukaryotic chromatin has a major impact on all nuclear processes involving DNA substrates. Gene expression is affected by the positioning of individual nucleosomes relative to regulatory sequence elements, by the folding of the nucleosomal fiber into higher-order structures and by the compartmentalization of functional domains within the nucleus. Because site-specific acetylation of nucleosomal histones influences all three aspects of chromatin organization, it is central to the switch between permissive and repressive chromatin structure. The targeting of enzymes that modulate the histone acetylation status of chromatin, in synergy with the effects mediated by other chromatin remodeling factors, is central to gene regulation. PMID:11882541

  12. 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

  13. Glucose kinase has a regulatory role in carbon catabolite repression in Streptomyces coelicolor.

    PubMed Central

    Kwakman, J H; Postma, P W

    1994-01-01

    A glucose kinase (glkA) mutant of Streptomyces coelicolor A3(2) M145 was selected by the ability to grow in the presence of the nonmetabolizable glucose analog 2-deoxyglucose. In this glkA mutant, carbon catabolite repression of glycerol kinase and agarase was relieved on several carbon sources tested, even though most of these carbon sources are not metabolized via glucose kinase. This suggests that catabolite repression is not regulated by the flux through glucose kinase and that the protein itself has a regulatory role in carbon catabolite repression. A 10-fold overproduction of glucose kinase also results in relief of catabolite repression, suggesting that excess glucose kinase can titrate the repressing signal away. This could be achieved directly by competition of excess glucose kinase with its repressing form for binding sites on DNA promoter regions or indirectly by competition for binding of another regulatory protein. Images PMID:8169219

  14. Histone Deacetylase Inhibitors: The Epigenetic Therapeutics That Repress Hypoxia-Inducible Factors

    PubMed Central

    Chen, Shuyang; Sang, Nianli

    2011-01-01

    Histone deacetylase inhibitors (HDACIs) have been actively explored as a new generation of chemotherapeutics for cancers, generally known as epigenetic therapeutics. Recent findings indicate that several types of HDACIs repress angiogenesis, a process essential for tumor metabolism and progression. Accumulating evidence supports that this repression is mediated by disrupting the function of hypoxia-inducible factors (HIF-1, HIF-2, and collectively, HIF), which are the master regulators of angiogenesis and cellular adaptation to hypoxia. Since HIF also regulate glucose metabolism, cell survival, microenvironment remodeling, and other alterations commonly required for tumor progression, they are considered as novel targets for cancer chemotherapy. Though the precise biochemical mechanism underlying the HDACI-triggered repression of HIF function remains unclear, potential cellular factors that may link the inhibition of deacetylase activity to the repression of HIF function have been proposed. Here we review published data that inhibitors of type I/II HDACs repress HIF function by either reducing functional HIF-1α levels, or repressing HIF-α transactivation activity. In addition, underlying mechanisms and potential proteins involved in the repression will be discussed. A thorough understanding of HDACI-induced repression of HIF function may facilitate the development of future therapies to either repress or promote angiogenesis for cancer or chronic ischemic disorders, respectively. PMID:21151670

  15. Repression of host RNA polymerase II transcription by herpes simplex virus type 1.

    PubMed Central

    Spencer, C A; Dahmus, M E; Rice, S A

    1997-01-01

    Lytic infection of mammalian cells with herpes simplex virus type 1 (HSV-1) results in rapid repression of host gene expression and selective activation of the viral genome. This transformation in gene expression is thought to involve repression of host transcription and diversion of the host RNA polymerase (RNAP II) transcription machinery to the viral genome. However, the extent of virus-induced host transcription repression and the mechanisms responsible for these major shifts in transcription specificities have not been examined. To determine how HSV-1 accomplishes repression of host RNAP II transcription, we assayed transcription patterns on several cellular genes in cells infected with mutant and wild-type HSV-1. Our results suggest that HSV-1 represses RNAP II transcription on most cellular genes. However, each cellular gene we examined responds differently to the transcription repressive effects of virus infection, both quantitatively and with respect to the involvement of viral gene products. Virus-induced shutoff of host RNAP II transcription requires expression of multiple immediate-early genes. In contrast, expression of delayed-early and late genes and viral DNA replication appear to contribute little to repression of host cell RNAP II transcription. Modification of RNAP II to the intermediately phosphorylated (II(I)) form appears unlinked to virus-induced repression of host cell transcription. However, full repression of host transcription is correlated with depletion of the hyperphosphorylated (IIO) form of RNAP II. PMID:9032335

  16. HES-Mediated Repression of Pten in Caenorhabditis elegans

    PubMed Central

    Chou, Han Ting; Vazquez, Raymarie Gomez; Wang, Kun; Campbell, Richard; Milledge, Gaolin Zheng; Walthall, Walter W.; Johnson, Casonya M.

    2015-01-01

    The hairy/enhancer-of-split (HES) group of transcription factors controls embryonic development, often by acting downstream of the Notch signaling pathway; however, little is known about postembryonic roles of these proteins. In Caenorhabditis elegans, the six proteins that make up the REF-1 family are considered to be HES orthologs that act in both Notch-dependent and Notch-independent pathways to regulate embryonic events. To further our understanding of how the REF-1 family works to coordinate postembryonic cellular events, we performed a functional characterization of the REF-1 family member, HLH-25. We show that, after embryogenesis, hlh-25 expression persists throughout every developmental stage, including dauer, into adulthood. Like animals that carry loss-of-function alleles in genes required for normal cell-cycle progression, the phenotypes of hlh-25 animals include reduced brood size, unfertilized oocytes, and abnormal gonad morphology. Using gene expression microarray, we show that the HLH-25 transcriptional network correlates with the phenotypes of hlh-25 animals and that the C. elegans Pten ortholog, daf-18, is one major hub in the network. Finally, we show that HLH-25 regulates C. elegans lifespan and dauer recovery, which correlates with a role in the transcriptional repression of daf-18 activity. Collectively, these data provide the first genetic evidence that HLH-25 may be a functional ortholog of mammalian HES1, which represses PTEN activity in mice and human cells. PMID:26438299

  17. 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.

  18. Abscisic acid represses the transcription of chloroplast genes*

    PubMed Central

    Yamburenko, Maria V.; Zubo, Yan O.; Börner, Thomas

    2013-01-01

    Numerous studies have shown effects of abscisic acid (ABA) on nuclear genes encoding chloroplast-localized proteins. ABA effects on the transcription of chloroplast genes, however, have not been investigated yet thoroughly. This work, therefore, studied the effects of ABA (75 μM) on transcription and steady-state levels of transcripts in chloroplasts of basal and apical segments of primary leaves of barley (Hordeum vulgare L.). Basal segments consist of young cells with developing chloroplasts, while apical segments contain the oldest cells with mature chloroplasts. Exogenous ABA reduced the chlorophyll content and caused changes of the endogenous concentrations not only of ABA but also of cytokinins to different extents in the basal and apical segments. It repressed transcription by the chloroplast phage-type and bacteria-type RNA polymerases and lowered transcript levels of most investigated chloroplast genes drastically. ABA did not repress the transcription of psbD and a few other genes and even increased psbD mRNA levels under certain conditions. The ABA effects on chloroplast transcription were more pronounced in basal vs. apical leaf segments and enhanced by light. Simultaneous application of cytokinin (22 μM 6-benzyladenine) minimized the ABA effects on chloroplast gene expression. These data demonstrate that ABA affects the expression of chloroplast genes differentially and points to a role of ABA in the regulation and coordination of the activities of nuclear and chloroplast genes coding for proteins with functions in photosynthesis. PMID:24078671

  19. Catabolite-induced repression of sporulation in Bacillus subtilis.

    PubMed

    Shafikhani, Sasha H; Partovi, Amir Ali; Leighton, Terrance

    2003-10-01

    In response to nutrient limitations, Bacillus subtilis cells undergo a series of morphological and genetic changes that culminate in the formation of endospores. Conversely, excess catabolites inhibit sporulation. It has been demonstrated previously that excess catabolites caused a decrease in culture medium pH in a process that required functional AbrB. Culture medium acidification was also shown to inhibit sigmaH-dependent sporulation gene expression. The studies reported here investigate the effects of AbrB-mediated pH sensing on B. subtilis developmental competence. We have found that neither addition of a pH stabilizer, MOPS (pH 7.5), nor null mutations in abrB blocked catabolite repression of sporulation. Moreover, catabolite-induced culture medium acidification was observed in cultures of catabolite-resistant sporulation mutants, crsA47, rvtA11, and hpr-16, despite their efficient sporulation. These results suggest that AbrB-mediated pH sensing is not the only mechanism regulating catabolite repression of sporulation. The AbrB pathway may function to channel cells toward genetic competence, as opposed to other postexponential differentiation pathways. PMID:14629011

  20. Iron uptake and iron-repressible polypeptides in Yersinia pestis.

    PubMed Central

    Lucier, T S; Fetherston, J D; Brubaker, R R; Perry, R D

    1996-01-01

    Pigmented (Pgm+) cells of Yersinia pestis are virulent, are sensitive to pesticin, adsorb exogenous hemin at 26 degrees C (Hms+), produce iron-repressible outer membrane proteins, and grow at 37 degrees C in iron-deficient media. These traits are lost upon spontaneous deletion of a chromosomal 102-kb pgm locus (Pgm-). Here we demonstrate that an Hms+ but pesticin-resistant (Pst(r)) mutant acquired a 5-bp deletion in the pesticin receptor gene (psn) encoding IrpB to IrpD. Growth and assimilation of iron by Pgm- and Hms+ Pst(r) mutants were markedly inhibited by ferrous chelators at 37 degrees C; inhibition by ferric and ferrous chelators was less effective at 26 degrees C. Iron-deficient growth at 26 degrees C induced iron-regulated outer membrane proteins of 34, 28.5, and 22.5 kDa and periplasmic polypeptides of 33.5 and 30 kDa. These findings provide a basis for understanding the psn-driven system of iron uptake, indicate the existence of at least one additional 26 degrees C-dependent iron assimilation system, and define over 30 iron-repressible proteins in Y. pestis. PMID:8757829

  1. Stories of illness and trauma survival: liberation or repression?

    PubMed

    Crossley, M L

    1999-06-01

    This paper aims to expand upon recent research addressing the relationship between power and cultural stories of illness. It does this by exploring the stories of 'healing' and 'survival' produced by people who have undergone traumatic experiences such as childhood sexual abuse and a HIV positive diagnosis. The liberating and/or repressive potential of cultural stories of illness are defined in accordance with their capacity to produce 'minimal' or more 'reflective' selves, as characterised by Lasch [Lasch, C., 1985. The Minimal Self. Picador, London.] and Giddens [Giddens, A., 1991. Modernity and Self-identity: Self and Society in the Later Modern Age. Polity Press, Cambridge.], respectively. Two predominant stories of survival are identified in this paper: the 'healing' story and the 'normalising' story. Each of these are explored in an attempt to address the question: How do we distinguish between 'liberating' and 'repressing' technologies of the self with regard to the telling of illness stories? [Frank, A., 1998. Stories of illness as care of the self: a Foucauldian dialogue. Health 2(3), 329-348, forthcoming.]. Through an examination of survivors' attempts to overcome their traumatic experiences via the appropriation of various illness stories, it is concluded that this question can only be answered in the practical and social context of each individual's life. PMID:10400266

  2. Dlx transcription factors promote migration through repression of axon and dendrite growth

    PubMed Central

    Cobos, Inma; Borello, Ugo; Rubenstein, John L.R.

    2016-01-01

    In the mouse telencephalon, Dlx homeobox transcription factors are essential for the tangential migration of subpallial-derived GABAergic interneurons to neocortex. However, the mechanisms underlying this process are poorly understood. Here, we demonstrate that Dlx1&2 have a central role in restraining neurite growth of subpallial-derived immature interneurons at a stage when they migrate tangentially to cortex. In Dlx1−/−;Dlx2−/− mutants, neurite length is increased and cells fail to migrate. In Dlx1−/−;Dlx2+/− mutants, while the tangential migration of immature interneurons appears normal, they develop dendritic and axonal processes with increased length and decreased branching, and have deficits in the their neocortical laminar positions. Thus, Dlx1&2 are required for coordinating programs of neurite maturation and migration. In this regard, we provide genetic evidence that in immature interneurons Dlx1&2 repression of the p21-activated kinase PAK3, a downstream effector of the Rho-family of GTPases, is critical in restraining neurite growth and promoting tangential migration. PMID:17582329

  3. Dlx transcription factors promote migration through repression of axon and dendrite growth.

    PubMed

    Cobos, Inma; Borello, Ugo; Rubenstein, John L R

    2007-06-21

    In the mouse telencephalon, Dlx homeobox transcription factors are essential for the tangential migration of subpallial-derived GABAergic interneurons to neocortex. However, the mechanisms underlying this process are poorly understood. Here, we demonstrate that Dlx1/2 has a central role in restraining neurite growth of subpallial-derived immature interneurons at a stage when they migrate tangentially to cortex. In Dlx1-/-;Dlx2-/- mutants, neurite length is increased and cells fail to migrate. In Dlx1-/-;Dlx2+/- mutants, while the tangential migration of immature interneurons appears normal, they develop dendritic and axonal processes with increased length and decreased branching, and have deficits in their neocortical laminar positions. Thus, Dlx1/2 is required for coordinating programs of neurite maturation and migration. In this regard, we provide genetic evidence that in immature interneurons Dlx1/2 repression of the p21-activated serine/threonine kinase PAK3, a downstream effector of the Rho family of GTPases, is critical in restraining neurite growth and promoting tangential migration. PMID:17582329

  4. T lymphocyte-derived TNF and IFN-γ repress HFE expression in cancer cells.

    PubMed

    Reuben, Alexandre; Godin-Ethier, Jessica; Santos, Manuela M; Lapointe, Réjean

    2015-06-01

    The immune system and tumors are closely intertwined initially upon tumor development. During this period, tumors evolve to promote self-survival through immune escape, including by targeting crucial components involved in the presentation of antigens to the immune system in order to avoid recognition. Accordingly, components involved in MHC I presentation of tumor antigens are often mutated and down-regulated targets in tumors. On the other hand, the immune system has been shown to influence tumors through production of immunosuppressive cytokines, recruitment and polarization of cells favoring or impeding tumor escape or through production of anti-tumor cytokines promoting tumor rejection. We previously discovered that the hemochromatosis protein HFE, a negative regulator of iron absorption, dampens classical MHC I antigen presentation. In this study, we evaluated the impact of activated T lymphocytes purified from peripheral blood mononuclear cells (PBMC) on HFE expression in tumor cell lines. We co-cultured tumor cell lines from melanoma, lung, and kidney cancers with anti-CD3-activated PBMC and established that HFE expression is increased in tumor cell lines compared to healthy tissues, whilst being down-regulated significantly upon exposure to activated PBMC. HFE down-regulation was mediated by both CD4 and CD8 T lymphocytes, through production of soluble mediators, namely TNF and IFN-γ. These results suggest that the immune system may modulate tumor HFE expression in inflammatory conditions in order to regulate MHC I antigen presentation and promote tumor clearance. PMID:25700349

  5. 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

  6. Two evolutionarily conserved repression domains in the Drosophila Kruppel protein differ in activator specificity.

    PubMed Central

    Hanna-Rose, W; Licht, J D; Hansen, U

    1997-01-01

    To identify biologically functional regions in the product of the Drosophila melanogaster gene Kruppel, we cloned the Kruppel homolog from Drosophila virilis. Both the previously identified amino (N)-terminal repression region and the DNA-binding region of the D. virilis Kruppel protein are greater than 96% identical to those of the D. melanogaster Kruppel protein, demonstrating a selective pressure to maintain the integrity of each region during 60 million to 80 million years of evolution. An additional region in the carboxyl (C) terminus of Kruppel that was most highly conserved was examined further. A 42-amino-acid stretch within the conserved C-terminal region also encoded a transferable repression domain. The short, C-terminal repression region is a composite of three subregions of distinct amino acid composition, each containing a high proportion of either basic, proline, or acidic residues. Mutagenesis experiments demonstrated, unexpectedly, that the acidic residues contribute to repression function. Both the N-terminal and C-terminal repression regions were tested for the ability to affect transcription mediated by a variety of activator proteins. The N-terminal repression region was able to inhibit transcription in the presence of multiple activators. However, the C-terminal repression region inhibited transcription by only a subset of the activator proteins. The different activator specificities of the two regions suggest that they repress transcription by different mechanisms and may play distinct biological roles during Drosophila development. PMID:9234738

  7. 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

  8. Brain feminization requires active repression of masculinization via DNA methylation

    PubMed Central

    Nugent, Bridget M.; Wright, Christopher L.; Shetty, Amol C.; Hodes, Georgia E.; Lenz, Kathryn M.; Mahurkar, Anup; Russo, Scott J.; Devine, Scott E.; McCarthy, Margaret M.

    2015-01-01

    The developing mammalian brain is destined for a female phenotype unless exposed to gonadal hormones during a perinatal sensitive period. It has been assumed that the undifferentiated brain is masculinized by direct induction of transcription by ligand-activated nuclear steroid receptors. We found that a primary effect of gonadal steroids in the highly sexually-dimorphic preoptic area (POA) is to reduce activity of DNA methyltransferase (Dnmt) enzymes, thereby decreasing DNA methylation and releasing masculinizing genes from epigenetic repression. Pharmacological inhibition of Dnmts mimicked gonadal steroids, resulting in masculinized neuronal markers and male sexual behavior in females. Conditional knockout of the de novo Dnmt isoform, Dnmt3a, also masculinized sexual behavior in female mice. RNA sequencing revealed gene and isoform variants modulated by methylation that may underlie the divergent reproductive behaviors of males versus females. Our data show that brain feminization is maintained by the active suppression of masculinization via DNA methylation. PMID:25821913

  9. Plant Callus: Mechanisms of Induction and Repression[OPEN

    PubMed Central

    Ikeuchi, Momoko; Sugimoto, Keiko; Iwase, Akira

    2013-01-01

    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

  10. MORC1 represses transposable elements in the mouse male germline

    PubMed Central

    Pastor, William A.; Stroud, Hume; Nee, Kevin; Liu, Wanlu; Pezic, Dubravka; Manakov, Sergei; Lee, Serena A.; Moissiard, Guillaume; Zamudio, Natasha; Bourc’his, Déborah; Aravin, Alexei A.; Clark, Amander T.; Jacobsen, Steven E.

    2014-01-01

    The Microrchidia (Morc) family of GHKL ATPases are present in a wide variety of prokaryotic and eukaryotic organisms but are of largely unknown function. Genetic screens in Arabidopsis thaliana have identified Morc genes as important repressors of transposons and other DNA-methylated and silent genes. MORC1-deficient mice were previously found to display male-specific germ cell loss and infertility. Here we show that MORC1 is responsible for transposon repression in the male germline in a pattern that is similar to that observed for germ cells deficient for the DNA methyltransferase homologue DNMT3L. Morc1 mutants show highly localized defects in the establishment of DNA methylation at specific classes of transposons, and this is associated with failed transposon silencing at these sites. Our results identify MORC1 as an important new regulator of the epigenetic landscape of male germ cells during the period of global de novo methylation. PMID:25503965

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. BRCA1-mediated repression of select X chromosome genes.

    PubMed

    Jazaeri, Amir A; Chandramouli, Gadisetti VR; Aprelikova, Olga; Nuber, Ulrike A; Sotiriou, Christos; Liu, Edison T; Ropers, H Hilger; Yee, Cindy J; Boyd, Jeff; Barrett, J Carl

    2004-09-21

    Recently BRCA1 has been implicated in the regulation of gene expression from the X chromosome. In this study the influence of BRCA1 on expression of X chromosome genes was investigated. Complementary DNA microarrays were used to compare the expression levels of X chromosome genes in 18 BRCA1-associated ovarian cancers to those of the 13 "BRCA1-like" and 14 "BRCA2-like" sporadic tumors (as defined by previously reported expression profiling). Significance was determined using parametric statistics with P < 0.005 as a cutoff. Forty of 178 total X-chromosome transcripts were differentially expressed between the BRCA1-associated tumors and sporadic cancers with a BRCA2-like molecular profile. Thirty of these 40 genes showed higher mean expression in the BRCA1-associated samples including all 11 transcripts that mapped to Xp11. In contrast, four of 178 total X chromosome transcripts showed significant differential expression between BRCA1-associated and sporadic tumors with a BRCA1-like molecular profile. All four mapped to Xp11 and showed higher mean expression in BRCA1-associated tumors. Re-expression of BRCA1 in HCC1937 BRCA1-deficient breast cancer cell resulted in the repression of 21 transcripts. Eleven of the 21 (54.5%) transcripts mapped to Xp11. However, there was no significant overlap between these Xp11 genes and those found to be differentially expressed between BRCA1-associated and sporadic ovarian cancer samples. These results demonstrate that BRCA1 mediates the repression of several X chromosome genes, many of which map to the Xp11 locus. PMID:15383145

  17. EHD2 shuttles to the nucleus and represses transcription.

    PubMed

    Pekar, Olga; Benjamin, Sigi; Weidberg, Hilla; Smaldone, Silvia; Ramirez, Francesco; Horowitz, Mia

    2012-06-15

    EHD {EH [Eps15 (epidermal growth factor receptor substrate 15) homology]-domain-containing} proteins participate in several endocytic events, such as the internalization and the recycling processes. There are four EHD proteins in mammalian cells, EHD1-EHD4, each with diverse roles in the recycling pathway of endocytosis. EHD2 is a plasma-membrane-associated member of the EHD family that regulates internalization. Since several endocytic proteins have been shown to undergo nucleocytoplasmic shuttling and have been assigned roles in regulation of gene expression, we tested the possibility that EHD proteins also shuttle to the nucleus. Our results showed that, among the three EHD proteins (EHD1-EHD3) that were tested, only EHD2 accumulates in the nucleus under nuclear export inhibition treatment. Moreover, the presence of a NLS (nuclear localization signal) was essential for its entry into the nucleus. Nuclear exit of EHD2 depended partially on its NES (nuclear export signal). Elimination of a potential SUMOylation site in EHD2 resulted in a major accumulation of the protein in the nucleus, indicating the involvement of SUMOylation in the nuclear exit of EHD2. We confirmed the SUMOylation of EHD2 by employing co-immunoprecipitation and the yeast two-hybrid system. Using GAL4-based transactivation assay as well as a KLF7 (Krüppel-like factor 7)-dependent transcription assay of the p21WAF1/Cip1 [CDKN1A (cyclin-dependent kinase inhibitor 1A)] gene, we showed that EHD2 represses transcription. qRT-PCR (quantitative real-time PCR) of RNA from cells overexpressing EHD2 or of RNA from cells knocked down for EHD2 confirmed that EHD2 represses transcription of the p21WAF1/Cip1 gene. PMID:22448906

  18. The relationship between two types of impaired emotion processing: repressive coping and alexithymia

    PubMed Central

    Myers, Lynn B.; Derakshan, Nazanin

    2015-01-01

    The constructs of repressive coping and alexithymia are both related to impaired emotion processing, yet individuals with a repressive coping style (repressors) score lower than controls on standard self-report measures of alexithymia. A large body of evidence indicates that repressors avoid negative affect. Therefore, the current study examined the relationship between repressive coping and alexithymia by using independently-rated interviews with the aim of bypassing repressors’ tendency of avoiding negative affect. Results showed that repressors scored high on alexithymia, similar to anxious individuals on the independently-rated interview, but scored low on alexithymia on a questionnaire measure. Our findings confirm a link between alexithymia and repressive coping and stress the need for non-standard measures in exploring the nature of the relationship between repressive coping and alexithymia. PMID:26136706

  19. Osa-containing Brahma chromatin remodeling complexes are required for the repression of Wingless target genes

    PubMed Central

    Collins, Russell T.; Treisman, Jessica E.

    2000-01-01

    The Wingless signaling pathway directs many developmental processes in Drosophila by regulating the expression of specific downstream target genes. We report here that the product of the trithorax group gene osa is required to repress such genes in the absence of the Wingless signal. The Wingless-regulated genes nubbin, Distal-less, and decapentaplegic and a minimal enhancer from the Ultrabithorax gene are misexpressed in osa mutants and repressed by ectopic Osa. Osa-mediated repression occurs downstream of the up-regulation of Armadillo but is sensitive both to the relative levels of activating Armadillo/Pangolin and repressing Groucho/Pangolin complexes present and to the responsiveness of the promoter to Wingless. Osa functions as a component of the Brahma chromatin-remodeling complex; other components of this complex are likewise required to repress Wingless target genes. These results suggest that altering the conformation of chromatin is an important mechanism by which Wingless signaling activates gene expression. PMID:11124806

  20. 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

  1. 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

  2. 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

  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. 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

  5. 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

  6. 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

  7. An adaptable system for improving transposon-based gene expression in vivo via transient transgene repression

    PubMed Central

    Doherty, Joseph E.; Woodard, Lauren E.; Bear, Adham S.; Foster, Aaron E.; Wilson, Matthew H.

    2013-01-01

    Transposons permit permanent cellular genome engineering in vivo. However, transgene expression falls rapidly postdelivery due to a variety of mechanisms, including immune responses. We hypothesized that delaying initial transgene expression would improve long-term transgene expression by using an engineered piggyBac transposon system that can regulate expression. We found that a 2-part nonviral Tet-KRAB inducible expression system repressed expression of a luciferase reporter in vitro. However, we also observed nonspecific promoter-independent repression. Thus, to achieve temporary transgene repression after gene delivery in vivo, we utilized a nonintegrating version of the repressor plasmid while the gene of interest was delivered in an integrating piggyBac transposon vector. When we delivered the luciferase transposon and repressor to immunocompetent mice by hydrodynamic injection, initial luciferase expression was repressed by 2 orders of magnitude. When luciferase expression was followed long term in vivo, we found that expression was increased >200-fold compared to mice that received only the luciferase transposon and piggyBac transposase. We found that repression of early transgene expression could prevent the priming of luciferase-specific T cells in vivo. Therefore, transient transgene repression postgene delivery is an effective strategy for inhibiting the antitransgene immune response and improving long-term expression in vivo without using immunosuppression.—Doherty, J. E., Woodard, L. E., Bear, A. S., Foster, A. E., Wilson, M. H. An adaptable system for improving transposon-based gene expression in vivo via transient transgene repression. PMID:23752206

  8. REG1 binds to protein phosphatase type 1 and regulates glucose repression in Saccharomyces cerevisiae.

    PubMed Central

    Tu, J; Carlson, M

    1995-01-01

    Protein phosphatase type 1 (PP1) is encoded by GLC7, an essential gene in Saccharomyces cerevisiae. The GLC7 phosphatase is required for glucose repression and appears to function antagonistically to the SNF1 protein kinase. Previously, we characterized a mutation, glc7-T152K, that relieves glucose repression but does not interfere with the function of GLC7 in glycogen metabolism. We proposed that the mutant GLC7T152K phosphatase is defective in its interaction with a regulatory subunit that directs participation of PP1 in the glucose repression mechanism. Here, we present evidence that REG1, a protein required for glucose repression, is one such regulatory subunit. We show that REG1 is physically associated with GLC7. REG1 interacts with GLC7 strongly and specifically in the two-hybrid system, and REG1 and GLC7 fusion proteins co-immunoprecipitate from cell extracts. Moreover, overexpression of a REG1 fusion protein suppresses the glc7-T152K mutant defect in glucose repression. This and other genetic evidence indicate that the two proteins function together in regulating glucose repression. These results suggest that REG1 is a regulatory subunit of PP1 that targets its activity to proteins in the glucose repression regulatory pathway. Images PMID:8846786

  9. Induction of endocycles represses apoptosis independently of differentiation and predisposes cells to genome instability

    PubMed Central

    Hassel, Christiane; Zhang, Bingqing; Dixon, Michael; Calvi, Brian R.

    2014-01-01

    The endocycle is a common developmental cell cycle variation wherein cells become polyploid through repeated genome duplication without mitosis. We previously showed that Drosophila endocycling cells repress the apoptotic cell death response to genotoxic stress. Here, we investigate whether it is differentiation or endocycle remodeling that promotes apoptotic repression. We find that when nurse and follicle cells switch into endocycles during oogenesis they repress the apoptotic response to DNA damage caused by ionizing radiation, and that this repression has been conserved in the genus Drosophila over 40 million years of evolution. Follicle cells defective for Notch signaling failed to switch into endocycles or differentiate and remained apoptotic competent. However, genetic ablation of mitosis by knockdown of Cyclin A or overexpression of fzr/Cdh1 induced follicle cell endocycles and repressed apoptosis independently of Notch signaling and differentiation. Cells recovering from these induced endocycles regained apoptotic competence, showing that repression is reversible. Recovery from fzr/Cdh1 overexpression also resulted in an error-prone mitosis with amplified centrosomes and high levels of chromosome loss and fragmentation. Our results reveal an unanticipated link between endocycles and the repression of apoptosis, with broader implications for how endocycles may contribute to genome instability and oncogenesis. PMID:24284207

  10. 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

  11. Human involucrin promoter mediates repression-resistant and compartment-specific LEKTI expression.

    PubMed

    Di, Wei-Li; Semenova, Ekaterina; Larcher, Fernando; Del Rio, Marcela; Harper, John I; Thrasher, Adrian J; Qasim, Waseem

    2012-01-01

    Gene-modified skin grafts, produced through gene transfer to human keratinocyte stem cells, offer the possibility of therapeutic benefit for inherited skin diseases. We have previously described efficient lentiviral vector-mediated gene transfer to keratinocyte stem cells and the generation of human skin grafts for the inherited skin disease, Netherton syndrome, which arises due to mutations in serine protease inhibitor Kazal-type 5 (SPINK5). Vectors incorporating an internal murine retroviral-derived promoter [spleen focus-forming virus (SFFV)] in combination with a codon-optimized SPINK5 transgene supported high levels of reconstitution and robust correction of skin architecture. Subsequent longer-term experiments have uncovered unanticipated silencing phenomena, with loss of SPINK5 gene expression over time. The inadvertent introduction of CpG sites during codon optimization appears to have rendered vectors susceptible to silencing due to methylation across the promoter-transgene boundary. Substitution of the methylation-susceptible SFFV promoter with a 572-bp minimal human involucrin promoter (INVOp), which encodes very few CpG sites, prevented repression of the SPINK5 transgene and resulted in durable and highly compartment-specific reconstitution of lympho-epithelial Kazal-type-related inhibitor (LEKTI) in human skin grafted onto immunodeficient mice. We conclude that skin grafts modified with lentiviral vectors encoding INVOp offer a suitable platform for therapeutic gene therapy in Netherton syndrome, and our experience highlights unanticipated effects of transgene codon optimization. PMID:21895535

  12. 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

  13. Nonmetabolizable analogue of 2-oxoglutarate elicits heterocyst differentiation under repressive conditions in Anabaena sp. PCC 7120

    PubMed Central

    Laurent, Sophie; Chen, Han; Bédu, Sylvie; Ziarelli, Fabio; Peng, Ling; Zhang, Cheng-Cai

    2005-01-01

    In response to combined nitrogen starvation in the growth medium, the filamentous cyanobacterium Anabaena sp. PCC 7120 is able to develop a particular cell type, called a heterocyst, specialized in molecular nitrogen fixation. Heterocysts are regularly intercalated among vegetative cells and represent 5–10% of all cells along each filament. In unicellular cyanobacteria, the key Krebs cycle intermediate, 2-oxoglutarate (2-OG), has been suggested as a nitrogen status signal, but in vivo evidence is still lacking. In this study we show that nitrogen starvation causes 2-OG to accumulate transiently within cells of Anabaena PCC 7120, reaching a maximal intracellular concentration of ≈0.1 mM 1 h after combined nitrogen starvation. A nonmetabolizable fluorinated 2-OG derivative, 2,2-difluoropentanedioic acid (DFPA), was synthesized and used to demonstrate the signaling function of 2-OG in vivo. DFPA is shown to be a structural analogue of 2-OG and the process of its uptake and accumulation in vivo can be followed by 19F magic angle spinning NMR because of the presence of the fluorine atom and its chemical stability. DFPA at a threshold concentration of 0.3 mM triggers heterocyst differentiation under repressing conditions. The multidisciplinary approaches using synthetic fluorinated analogues, magic angle spinning NMR for their analysis in vivo, and techniques of molecular biology provide a powerful means to identify the nature of the signals that remain unknown or poorly defined in many signaling pathways. PMID:15985552

  14. The TOPLESS Interactome: A Framework for Gene Repression in Arabidopsis1[W][OA

    PubMed Central

    Causier, Barry; Ashworth, Mary; Guo, Wenjia; Davies, Brendan

    2012-01-01

    Transcription factors activate or repress target gene expression or switch between activation and repression. In animals and yeast, Groucho/Tup1 corepressor proteins are recruited by diverse transcription factors to induce context-specific transcriptional repression. Two groups of Groucho/Tup1-like corepressors have been described in plants. LEUNIG and LEUNIG_HOMOLOG constitute one group and TOPLESS (TPL) and the four TPL-related (TPR) corepressors form the other. To discover the processes in which TPL and the TPR corepressors operate, high-throughput yeast two-hybrid approaches were used to identify interacting proteins. We found that TPL/TPR corepressors predominantly interact directly with specific transcription factors, many of which were previously implicated in transcriptional repression. The interacting transcription factors reveal that the TPL/TPR family has been coopted multiple times to modulate gene expression in diverse processes, including hormone signaling, stress responses, and the control of flowering time, for which we also show biological validation. The interaction data suggest novel mechanisms for the involvement of TPL/TPR corepressors in auxin and jasmonic acid signaling. A number of short repression domain (RD) sequences have previously been identified in Arabidopsis (Arabidopsis thaliana) transcription factors. All known RD sequences were enriched among the TPL/TPR interactors, and novel TPL-RD interactions were identified. We show that the presence of RD sequences is essential for TPL/TPR recruitment. These data provide a framework for TPL/TPR-dependent transcriptional repression. They allow for predictions about new repressive transcription factors, corepressor interactions, and repression mechanisms and identify a wide range of plant processes that utilize TPL/TPR-mediated gene repression. PMID:22065421

  15. Transcriptional activation and repression by Fos are independent functions: the C terminus represses immediate-early gene expression via CArG elements.

    PubMed

    Gius, D; Cao, X M; Rauscher, F J; Cohen, D R; Curran, T; Sukhatme, V P

    1990-08-01

    The Fos-Jun complex has been shown to activate transcription through the regulatory element known as the AP-1 binding site. We show that Fos down regulates several immediate-early genes (c-fos, Egr-1, and Egr-2) after mitogenic stimulation. Specifically, we demonstrate that the target for this repression is a sequence of the form CC(A/T)6GG, also known as a CArG box. Whereas Fos bound to the AP-1 site through a domain rich in basic amino acids and associated with Jun via a leucine zipper interaction, mutant Fos proteins lacking these structures were still capable of causing repression. Furthermore, Jun neither enhanced nor inhibited down regulation by Fos. Critical residues required for repression are located within the C-terminal 27 amino acids of c-Fos, since v-Fos and C-terminal truncations of c-Fos did not down regulate. In addition, transfer of 180 c-Fos C-terminal amino acids to Jun conferred upon it the ability to repress. Finally, Fra-1, a Fos-related protein which has striking similarity to Fos in its C-terminal 40 amino acids, also down regulated Egr-1 expression. Thus, Fos is a transcriptional regulator that can activate or repress gene expression by way of two separate functional domains that act on distinct regulatory elements. PMID:2115122

  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. The Functions of MicroRNAs: mRNA Decay and Translational Repression.

    PubMed

    Iwakawa, Hiro-oki; Tomari, Yukihide

    2015-11-01

    MicroRNAs (miRNAs) are a class of endogenous small noncoding RNAs, which regulate complementary mRNAs by inducing translational repression and mRNA decay. Although this dual repression system seems to operate in both animals and plants, genetic and biochemical studies suggest that the mechanism underlying the miRNA-mediated silencing is different in the two kingdoms. Here, we review the recent progress in our understanding of how miRNAs mediate translational repression and mRNA decay, and discuss the contributions of the two silencing modes to the overall silencing effect in both kingdoms. PMID:26437588

  18. 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. PMID:19635812

  19. Repression of the Antioxidant NRF2 Pathway in Premature Aging.

    PubMed

    Kubben, Nard; Zhang, Weiqi; Wang, Lixia; Voss, Ty C; Yang, Jiping; Qu, Jing; Liu, Guang-Hui; Misteli, Tom

    2016-06-01

    Hutchinson-Gilford progeria syndrome (HGPS) is a rare, invariably fatal premature aging disorder. The disease is caused by constitutive production of progerin, a mutant form of the nuclear architectural protein lamin A, leading, through unknown mechanisms, to diverse morphological, epigenetic, and genomic damage and to mesenchymal stem cell (MSC) attrition in vivo. Using a high-throughput siRNA screen, we identify the NRF2 antioxidant pathway as a driver mechanism in HGPS. Progerin sequesters NRF2 and thereby causes its subnuclear mislocalization, resulting in impaired NRF2 transcriptional activity and consequently increased chronic oxidative stress. Suppressed NRF2 activity or increased oxidative stress is sufficient to recapitulate HGPS aging defects, whereas reactivation of NRF2 activity in HGPS patient cells reverses progerin-associated nuclear aging defects and restores in vivo viability of MSCs in an animal model. These findings identify repression of the NRF2-mediated antioxidative response as a key contributor to the premature aging phenotype. PMID:27259148

  20. 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

  1. 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

  2. The Notch intracellular domain represses CRE-dependent transcription.

    PubMed

    Hallaq, Rania; Volpicelli, Floriana; Cuchillo-Ibanez, Inmaculada; Hooper, Claudie; Mizuno, Keiko; Uwanogho, Dafe; Causevic, Mirsada; Asuni, Ayodeji; To, Alvina; Soriano, Salvador; Giese, K Peter; Lovestone, Simon; Killick, Richard

    2015-03-01

    Members of the cyclic-AMP response-element binding protein (CREB) transcription factor family regulate the expression of genes needed for long-term memory formation. Loss of Notch impairs long-term, but not short-term, memory in flies and mammals. We investigated if the Notch-1 (N1) exerts an effect on CREB-dependent gene transcription. We observed that N1 inhibits CREB mediated activation of cyclic-AMP response element (CRE) containing promoters in a γ-secretase-dependent manner. We went on to find that the γ-cleaved N1 intracellular domain (N1ICD) sequesters nuclear CREB1α, inhibits cAMP/PKA-mediated neurite outgrowth and represses the expression of specific CREB regulated genes associated with learning and memory in primary cortical neurons. Similar transcriptional effects were observed with the N2ICD, N3ICD and N4ICDs. Together, these observations indicate that the effects of Notch on learning and memory are, at least in part, via an effect on CREB-regulated gene expression. PMID:25479589

  3. 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

  4. The kinase activity of PKR represses inflammasome activity.

    PubMed

    Yim, Howard C H; Wang, Die; Yu, Liang; White, Christine L; Faber, Pieter W; Williams, Bryan R G; Sadler, Anthony J

    2016-03-01

    The protein kinase R (PKR) functions in the antiviral response by controlling protein translation and inflammatory cell signaling pathways. We generated a transgenic, knock-in mouse in which the endogenous PKR is expressed with a point mutation that ablates its kinase activity. This novel animal allows us to probe the kinase-dependent and -independent functions of PKR. We used this animal together with a previously generated transgenic mouse that is ablated for PKR expression to determine the role of PKR in regulating the activity of the cryopyrin inflammasome. Our data demonstrate that, in contradiction to earlier reports, PKR represses cryopyrin inflammasome activity. We demonstrate that this control is mediated through the established function of PKR to inhibit protein translation of constituents of the inflammasome to prevent initial priming during innate immune signaling. These findings identify an important role for PKR to dampen inflammation during the innate immune response and caution against the previously proposed therapeutic strategy to inhibit PKR to treat inflammation. PMID:26794869

  5. Repression of the albumin gene in Novikoff hepatoma cells.

    PubMed Central

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

    1982-01-01

    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 [32P]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. Images PMID:6180302

  6. 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

  7. 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

  8. 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

  9. NF90 coordinately represses the senescence-associated secretory phenotype

    PubMed Central

    Tominaga-Yamanaka, Kumiko; Abdelmohsen, Kotb; Martindale, Jennifer L.; Yang, Xiaoling; Taub, Dennis D.; Gorospe, Myriam

    2012-01-01

    A hallmark trait of cellular senescence is the acquisition of a senescence-associated secretory phenotype (SASP). SASP factors include cytokines and their receptors (IL-6, IL-8, osteoprotegerin, GM-CSF), chemokines and their ligands (MCP-1, HCC4), and oncogenes (Gro1 and Gro2), many of them encoded by mRNAs whose stability and translation are tightly regulated. Using two models of human fibroblast senescence (WI-38 and IDH4 cells), we report the identification of RNA-binding protein NF90 as a post-transcriptional repressor of several SASP factors. In ‘young’, proliferating fibroblasts, NF90 was highly abundant, associated with numerous SASP mRNAs, and inhibited their expression. By contrast, senescent cells expressed low levels of NF90, thus allowing SASP factor expression to increase. NF90 elicited these effects mainly by repressing the translation of target SASP mRNAs, since silencing NF90 did not increase the steady-state levels of SASP mRNAs but elevated key SASP factors including MCP-1, GROa, IL-6, and IL-8. Our findings indicate that NF90 contributes to maintaining low levels of SASP factors in non-senescent cells, while NF90 reduction in senescent cells allows SASP factor expression to rise. PMID:23117626

  10. 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

  11. The HTLV-1 Tax oncoprotein represses Ku80 gene expression.

    PubMed

    Ducu, Razvan I; Dayaram, Tajhal; Marriott, Susan J

    2011-07-20

    The HTLV-I oncoprotein Tax interferes with DNA double strand break repair. Since non-homologous end joining (NHEJ) is a major pathway used to repair DNA double strand breaks we examined the effect of Tax on this pathway, with particular interest in the expression and function of Ku80, a critical component of the NHEJ pathway. Tax expression decreased Ku80 mRNA and protein levels, and repressed transcription from the Ku80 promoter. Conversely, Ku80 mRNA increased following siRNA knockdown of Tax in HTLV-I infected cells. Tax expression was associated with an elevated number of micronuclei and nucleoplasmic bridges, hallmarks of improper DNA double strand break repair. Our studies identified Tax as a transcriptional repressor of Ku80 that correlates with decreased DNA repair function. The reduction of Ku80 transcription by Tax may deplete the cell of an essential DNA break binding protein, resulting in reduced repair of DNA double strand breaks and accumulation genomic mutations. PMID:21571351

  12. Superoxide dismutase during glucose repression of Hansenula polymorpha CBS 4732.

    PubMed

    Hristozova, Tsonka; Rasheva, Tanya; Nedeva, Trayana; Kujumdzieva, Anna

    2002-01-01

    Hansenula polymorpha CBS 4732 was studied during cultivation on methanol and different glucose concentrations. Activities of Cu/Zn and Mn superoxide dismutase, catalase and methanol oxidase were investigated. During cultivation on methanol, increased superoxide dismutase and catalase activities and an induced methanol oxidase were achieved. Transfer of a methanol grown culture to medium with a high glucose concentration caused growth inhibition, low consumption of carbon, nitrogen and phosphate substrates, methanol oxidase inactivation as well as decrease of catalase activity (21.8 +/- 0.61 deltaE240 x min(-1) x mg protein(-1)). At the same time, a high value for superoxide dismutase enzyme was found (42.9 +/- 0.98 U x mg protein(-1), 25% of which was represented by Mn superoxide dismutase and 75% - by the Cu/Zn type). During derepression methanol oxidase was negligible (0.005 +/- 0.0001 U x mg protein(-1)), catalase tended to be the same as in the repressed culture, while superoxide dismutase activity increased considerably (63.67 +/- 1.72 U x mg protein(-1), 69% belonging to the Cu/Zn containing enzyme). Apparently, the cycle of growth inhibition and reactivation of Hansenula polymorpha CBS 4732 cells is strongly connected with the activity of the enzyme superoxide dismutase. PMID:12064733

  13. Functional dissection of the global repressor Tup1 in yeast: dominant role of the C-terminal repression domain.

    PubMed Central

    Zhang, Zhizhou; Varanasi, Ushasri; Trumbly, Robert J

    2002-01-01

    In the yeast Saccharomyces cerevisiae, Tup1, in association with Cyc8 (Ssn6), functions as a general repressor of transcription. Tup1 and Cyc8 are required for repression of diverse families of genes coordinately controlled by glucose repression, mating type, and other mechanisms. This repression is mediated by recruitment of the Cyc8-Tup1 complex to target promoters by sequence-specific DNA-binding proteins. We created a library of XhoI linker insertions and internal in-frame deletion mutations within the TUP1 coding region. Insertion mutations outside of the WD domains were wild type, while insertions within the WD domains induced mutant phenotypes with differential effects on the target genes SUC2, MFA2, RNR2, and HEM13. Deletion mutations confirmed previous findings of two separate repression domains in the N and C termini. The cumulative data suggest that the C-terminal repression domain, located near the first WD repeat, plays the dominant role in repression. Although the N-terminal repression domain is sufficient for partial repression, deletion of this region does not compromise repression. Surprisingly, deletion of the majority of the histone-binding domain of Tup1 also does not significantly reduce repression. The N-terminal region containing potential alpha-helical coiled coils is required for Tup1 oligomerization and association with Cyc8. Association with Cyc8 is required for repression of SUC2, HEM13, and RNR2 but not MFA2 and STE2. PMID:12136003

  14. 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

  15. Isolation and characterization of a catabolite repression-insensitive mutant of a methanol yeast, Candida boidinii A5, producing alcohol oxidase in glucose-containing medium

    SciTech Connect

    Sakai, Y.; Sawai, T.; Tani, Y.

    1987-08-01

    Mutants exhibiting alcohol oxidase activity when grown on glucose in the presence of methanol were found among 2-deoxyglucose-resistant mutants derived from a methanol yeast, Candida boidinii A5. One of these mutants, strain ADU-15, showed the highest alcohol oxidase activity in glucose-containing medium. The growth characteristics and also the induction and degradation of alcohol oxidase were compared with the parent strain and mutant strain ADU-15. In the parent strain, initiation of alcohol oxidase synthesis was delayed by the addition of 0.5% glucose to the methanol medium, whereas it was not delayed in mutant strain ADU-15. This showed that alcohol oxidase underwent repression by glucose. On the other hand, degradation of alcohol oxidase after transfer of the cells from methanol to glucose medium (catabolite inactivation) was observed to proceed at similar rates in parent and mutant strains. The results of immunochemical titration experiments suggests that catabolite inactivation of alcohol oxidase is coupled with a quantitative change in the enzyme. Mutant strain ADU-15 was proved to be a catabolite repression-insensitive mutant and to produce alcohol oxidase in the presence of glucose. However, it was not an overproducer of alcohol oxidase and, in both the parent and mutant strains, alcohol oxidase was completely repressed by ethanol.

  16. A cis-acting element in the promoter of human ether à go-go 1 potassium channel gene mediates repression by calcitriol in human cervical cancer cells.

    PubMed

    Cázares-Ordoñez, V; González-Duarte, R J; Díaz, L; Ishizawa, M; Uno, S; Ortíz, V; Ordoñez-Sánchez, M L; Makishima, M; Larrea, F; Avila, E

    2015-02-01

    The human ether à go-go 1 potassium channel (hEAG1) is required for cell cycle progression and proliferation of cancer cells. Inhibitors of hEAG1 activity and expression represent potential therapeutic drugs in cancer. Previously, we have shown that hEAG1 expression is downregulated by calcitriol in a variety of cancer cells. Herein, we provided evidence on the regulatory mechanism involved in such repressive effect in cells derived from human cervical cancer. Our results indicate that repression by calcitriol occurs at the transcriptional level and involves a functional negative vitamin D response element (nVDRE) E-box type in the hEAG1 promoter. The described mechanism in this work implies that a protein complex formed by the vitamin D receptor-interacting repressor, the vitamin D receptor, the retinoid X receptor, and the Williams syndrome transcription factor interact with the nVDRE in the hEAG1 promoter in the absence of ligand. Interestingly, all of these transcription factors except the vitamin D receptor-interacting repressor are displaced from hEAG1 promoter in the presence of calcitriol. Our results provide novel mechanistic insights into calcitriol mode of action in repressing hEAG1 gene expression. PMID:25495694

  17. An Alternative Transcript of the FOG-2 Gene Encodes a FOG-2 Isoform lacking the FOG Repression Motif

    PubMed Central

    Dale, Rodney M.; Remo, Benjamin F.; Svensson, Eric C.

    2007-01-01

    The FOG family of transcriptional co-factors is composed of two members in mammals: FOG-1 and FOG-2. Both have been shown to bind to GATA factors and function as transcriptional co-repressors in specific cell and promoter contexts. We have previously defined a novel repression domain localized to the N-terminus of each FOG family member, the FOG Repression Motif, which is necessary for FOG-mediated transcriptional repression. In this report, we describe the identification and characterization of a novel isoform of FOG-2 lacking the FOG Repression Motif. In contrast to full-length FOG-2, this isoform is expressed predominately in the embryonic and adult heart. It can bind GATA4 avidly, but is unable to repress GATA4-mediated activation of cardiac-restricted gene promoters. Together, these results suggest that FOG-2 repressive activity may be modulated by the generation of isoforms of FOG-2 lacking the FOG repression motif. PMID:17445768

  18. Repressive coping style and autonomic reactions to two experimental stressors in healthy men and women.

    PubMed

    Jørgensen, Michael Martini; Zachariae, Robert

    2006-04-01

    Autonomic and affective responses to two different stress tasks were measured in 45 males and 74 females, categorized as repressive, true low-anxious, true high-anxious, and defensive high-anxious. Electrodermal activity (EDA) was used as a measure of sympathetic activity and the high frequency (HF) spectral component of heart rate variability as a measure of parasympathetic activity. Contrary to our predictions, reactivity of repressors did not differ from the reactivity of true low-anxious participants. The results draw attention to previous inconsistent findings within the literature on repressive coping style and autonomic nervous system dysregulation. It is suggested that future research could benefit from the use of more consistent operationalizations of the repressive coping construct and from comparing alternative measures of repressive coping within the same study. PMID:16542356

  19. Engrailed cooperates with extradenticle and homothorax to repress target genes in Drosophila

    PubMed Central

    Kobayashi, Masatomo; Fujioka, Miki; Tolkunova, Elena N.; Deka, Deepali; Abu-Shaar, Muna; Mann, Richard S.; Jaynes, James B.

    2009-01-01

    SUMMARY Engrailed is a key transcriptional regulator in the nervous system and in the maintenance of developmental boundaries in Drosophila, and its vertebrate homologs regulate brain and limb development. Here, we show that the functions of both of the Hox cofactors Extradenticle and Homothorax play essential roles in repression by Engrailed. Mutations that remove either of them abrogate the ability of Engrailed to repress its target genes in embryos, both cofactors interact directly with Engrailed, and both stimulate repression by Engrailed in cultured cells. We suggest a model in which Engrailed, Extradenticle and Homothorax function as a complex to repress Engrailed target genes. These studies expand the functional requirements for extradenticle and homothorax beyond the Hox proteins to a larger family of non-Hox homeodomain proteins. PMID:12506004

  20. Inactivation, sequence, and lacZ fusion analysis of a regulatory locus required for repression of nitrogen fixation genes in Rhodobacter capsulatus.

    PubMed Central

    Kranz, R G; Pace, V M; Caldicott, I M

    1990-01-01

    Transcription of the genes that code for proteins involved in nitrogen fixation in free-living diazotrophs is typically repressed by high internal oxygen concentrations or exogenous fixed nitrogen. The DNA sequence of a regulatory locus required for repression of Rhodobacter capsulatus nitrogen fixation genes was determined. It was shown that this locus, defined by Tn5 insertions and by ethyl methanesulfonate-derived mutations, is homologous to the glnB gene of other organisms. The R. capsulatus glnB gene was upstream of glnA, the gene for glutamine synthetase, in a glnBA operon. beta-Galactosidase expression from an R. capsulatus glnBA-lacZ translational fusion was increased twofold in cells induced by nitrogen limitation relative to that in cells under nitrogen-sufficient conditions. R. capsulatus nifR1, a gene that was previously shown to be homologous to ntrC and that is required for transcription of nitrogen fixation genes, was responsible for approximately 50% of the transcriptional activation of this glnBA fusion in cells induced under nitrogen-limiting conditions. R. capsulatus GLNB, NIFR1, and NIFR2 (a protein homologous to NTRB) were proposed to transduce the nitrogen status in the cell into repression or activation of other R. capsulatus nif genes. Repression of nif genes in response to oxygen was still present in R. capsulatus glnB mutants and must have occurred at a different level of control in the regulatory circuit. Images FIG. 4 FIG. 5 PMID:2152916

  1. Coordinate post-transcriptional repression of Dpp-dependent transcription factors attenuates signal range during development

    PubMed Central

    Newton, Fay G.; Harris, Robin E.; Sutcliffe, Catherine; Ashe, Hilary L.

    2015-01-01

    Precise control of the range of signalling molecule action is crucial for correct cell fate patterning during development. For example, Drosophila ovarian germline stem cells (GSCs) are maintained by exquisitely short-range BMP signalling from the niche. In the absence of BMP signalling, one GSC daughter differentiates into a cystoblast (CB) and this fate is stabilised by Brain tumour (Brat) and Pumilio (Pum)-mediated post-transcriptional repression of mRNAs, including that encoding the Dpp transducer, Mad. However, the identity of other repressed mRNAs and the mechanism of post-transcriptional repression are currently unknown. Here, we identify the Medea and schnurri mRNAs, which encode transcriptional regulators required for activation and/or repression of Dpp target genes, as additional Pum-Brat targets, suggesting that tripartite repression of the transducers is deployed to desensitise the CB to Dpp. In addition, we show that repression by Pum-Brat requires recruitment of the CCR4 and Pop2 deadenylases, with knockdown of deadenylases in vivo giving rise to ectopic GSCs. Consistent with this, Pum-Brat repression leads to poly(A) tail shortening and mRNA degradation in tissue culture cells, and we detect a reduced number of Mad and shn transcripts in the CB relative to the GSC based on single molecule mRNA quantitation. Finally, we show generality of the mechanism by demonstrating that Brat also attenuates pMad and Dpp signalling range in the early embryo. Together our data serve as a platform for understanding how post-transcriptional repression restricts interpretation of BMPs and other cell signals in order to allow robust cell fate patterning during development. PMID:26293305

  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. Influence of Catabolite Repression and Inducer Exclusion on the Bistable Behavior of the lac Operon

    PubMed Central

    Santillán, Moisés; Mackey, Michael C.

    2004-01-01

    A mathematical model of the lac operon which includes all of the known regulatory mechanisms, including external-glucose-dependent catabolite repression and inducer exclusion, as well as the time delays inherent to transcription and translation, is presented. With this model we investigate the influence of external glucose, by means of catabolite repression and the regulation of lactose uptake, on the bistable behavior of this system. PMID:14990461

  4. Chick Pcl2 regulates the left-right asymmetry by repressing Shh expression in Hensen's node.

    PubMed

    Wang, Shusheng; Yu, Xueyan; Zhang, Tao; Zhang, Xiaoyun; Zhang, Zunyi; Chen, YiPing

    2004-09-01

    Asymmetric expression of sonic hedgehog (Shh) in the left side of Hensen's node, a crucial step for specifying the left-right (LR) axis in the chick embryo, is established by the repression of Shh expression in the right side of the node. The transcriptional regulator that mediates this repression has not been identified. We report the isolation and characterization of a novel chick Polycomblike 2 gene, chick Pcl2, which encodes a transcription repressor and displays an asymmetric expression, downstream from Activin-betaB and Bmp4, in the right side of Hensen's node in the developing embryo. In vitro mapping studies define the transcription repression activity to the PHD finger domain of the chick Pcl2 protein. Repression of chick Pcl2 expression in the early embryo results in randomized heart looping direction, which is accompanied by the ectopic expression of Shh in the right side of the node and Shh downstream genes in the right lateral plate mesoderm (LPM), while overexpression of chick Pcl2 represses Shh expression in the node. The repression of Shh by chick Pcl2 was also supported by studies in which chick Pcl2 was overexpressed in the developing chick limb bud and feather bud. Similarly, transgenic overexpression of chick Pcl2 in the developing mouse limb inhibits Shh expression in the ZPA. In vitro pull-down assays demonstrated a direct interaction of the chick Pcl2 PHD finger with EZH2, a component of the ESC/E(Z) repressive complex. Taken together with the fact that chick Pcl2 was found to directly repress Shh promoter activity in vitro, our results demonstrate a crucial role for chick Pcl2 in regulating LR axis patterning in the chick by silencing Shh in the right side of the node. PMID:15294861

  5. 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

  6. 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

  7. Bacterial promoter repression by DNA looping without protein–protein binding competition

    PubMed Central

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

    2014-01-01

    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

  8. YY1 represses human papillomavirus type 16 transcription by quenching AP-1 activity.

    PubMed Central

    O'Connor, M J; Tan, S H; Tan, C H; Bernard, H U

    1996-01-01

    YY1 is a multifunctional transcription factor that has been shown to regulate the expression of a number of cellular and viral genes, including the human papillomavirus (HPV) oncogenes E6 and E7. In this study, we have analyzed the YY1-mediated repression of the HPV type 16 (HPV-16) E6-E7 promoter. A systematic analysis to identify YY1 sites present in the HPV-16 long control region showed that of 30 potential YY1 binding motifs, 24 bound purified recombinant YY1 protein, but only 10 of these were able to bind YY1 when nuclear extracts of HeLa cells were used. Of these, only a cluster of five sites, located in the vicinity of an AP-1 motif, were found to be responsible for repressing the HPV-16 P97 promoter. All five sites were required for repression, the mutation of any one site giving rise to a four- to sixfold increase in transcriptional activity. The target for YY1-mediated repression was identified as being a highly conserved AP-1 site, and we propose that AP-1 may represent a common target for YY1 repression. We also provide data demonstrating that YY1 can bind the transcriptional coactivator CREB-binding protein and propose a potentially novel mechanism by which YY1 represses AP-1 activity as a result of this YY1-CREB-binding protein interaction. PMID:8794287

  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. 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

  11. Bhlhe40 Represses PGC-1α Activity on Metabolic Gene Promoters in Myogenic Cells

    PubMed Central

    Chung, Shih Ying; Kao, Chien Han; Villarroya, Francesc; Chang, Hsin Yu; Chang, Hsuan Chia; Hsiao, Sheng Pin; Liou, Gunn-Guang

    2015-01-01

    PGC-1α is a transcriptional coactivator promoting oxidative metabolism in many tissues. Its expression in skeletal muscle (SKM) is induced by hypoxia and reactive oxidative species (ROS) generated during exercise, suggesting that PGC-1α might mediate the cross talk between oxidative metabolism and cellular responses to hypoxia and ROS. Here we found that PGC-1α directly interacted with Bhlhe40, a basic helix-loop-helix (bHLH) transcriptional repressor induced by hypoxia, and protects SKM from ROS damage, and they cooccupied PGC-1α-targeted gene promoters/enhancers, which in turn repressed PGC-1α transactivational activity. Bhlhe40 repressed PGC-1α activity through recruiting histone deacetylases (HDACs) and preventing the relief of PGC-1α intramolecular repression caused by its own intrinsic suppressor domain. Knockdown of Bhlhe40 mRNA increased levels of ROS, fatty acid oxidation, mitochondrial DNA, and expression of PGC-1α target genes. Similar effects were also observed when the Bhlhe40-mediated repression was rescued by a dominantly active form of the PGC-1α-interacting domain (PID) from Bhlhe40. We further found that Bhlhe40-mediated repression can be largely relieved by exercise, in which its recruitment to PGC-1α-targeted cis elements was significantly reduced. These observations suggest that Bhlhe40 is a novel regulator of PGC-1α activity repressing oxidative metabolism gene expression and mitochondrion biogenesis in sedentary SKM. PMID:25963661

  12. 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

  13. Freud's 'thought-transference', repression, and the future of psychoanalysis.

    PubMed

    Farrell, D

    1983-01-01

    Psychoanalysts since Freud have largely neglected his important, paradigmatic ideas on the possibility of 'thought-transference' (telepathy) as an influence in mental life. A chance recording of two dreams which proved to coincide in some detail with distant reality events again suggests evidence in favour of the telepathy hypothesis. On interpretation, one of these dreams reveals even greater correspondence with the reality event and shows the mechanism of transformation of the repressed wish from latent dream content into manifest dream, utilizing a number of elements of the dream instigator, an apparently telepathically received day residue. Working with this material proceeded against very strong resistance, most evident in repeated forgetting of one or another bit of the clinical data. This has been the fate of ideas pertaining to the occult since Freud's first formulations, as is documented here by references to the early history of psychoanalysis. The issue now and for the future is whether psychoanalysis will continue to ignore the crucial question of validity in regard to the telepathy hypothesis. The psychoanalytic method is uniquely qualified to investigate so-called parapsychological phenomena and has the same obligation to do so as with other mental events. We need to examine the evidence in spite of the threat posed to our conventional understanding of the limits of the mind by the very act of acknowledging the question. If we can overcome our resistance to undertaking this task, we may find that, once again, Freud pointed the way towards discovery of a new paradigm in science. PMID:6853049

  14. 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

  15. 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

  16. PTH and Vitamin D Repress DMP1 in Cementoblasts.

    PubMed

    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

    2015-10-01

    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

  17. Extra telomeres, but not internal tracts of telomeric DNA, reduce transcriptional repression at Saccharomyces telomeres

    SciTech Connect

    Wiley, E.A.; Zakian, V.A.

    1995-01-01

    Yeast telomeric DNA is assembled into a nonnucleosomal chromatin structure known as the telosome, which is thought to influence the transcriptional repression of genes placed in its vicinity, a phenomenon called telomere position effect (TPE). The product of the RAP1 gene, Rap1p, is a component of the telosome. We show that the fraction of cells exhibiting TPE can be substantially reduced by expressing large amounts of a deletion derivative of Rap1p that is unable to bind DNA, called Rap1{Delta}BBp, or by introducing extra telomeres on a linear plasmid, presumably because both compete in trans with telomeric chromatin for factor(s) important for TPE. This reduction in TPE, observed in three different strains, was demonstrated for two different genes, each assayed at a different telomere. In contrast, the addition of internal tracts of telomeric DNA on a circular plasmid had very little effect on TPE. The product of the SIR3 gene, Sir3p, appears to be limiting for TPE. Overexpression of Sir3p completely suppressed the reduction in TPE observed with expression of Rap1{Delta}BBp, but did not restore high levels of TPE to cells with extra telomeres. These results suggest that extra telomeres must titrate a factor other than Sir3p that is important for TPE. These results also provide evidence for a terminus-specific binding factor that is a factor with a higher affinity for DNA termini than for nonterminal tracts of telomeric DNA and indicate that this factor is important for TPE. 51 refs., 8 figs., 1 tab.

  18. Extra Telomeres, but Not Internal Tracts of Telomeric Dna, Reduce Transcriptional Repression at Saccharomyces Telomeres

    PubMed Central

    Wiley, E. A.; Zakian, V. A.

    1995-01-01

    Yeast telomeric DNA is assembled into a nonnucleosomal chromatin structure known as the telosome, which is thought to influence the transcriptional repression of genes placed in its vicinity, a phenomenon called telomere position effect (TPE). The product of the RAP1 gene, Rap1p, is a component of the telosome. We show that the fraction of cells exhibiting TPE can be substantially reduced by expressing large amounts of a deletion derivative of Rap1p that is unable to bind DNA, called Rap1δBBp, or by introducing extra telomeres on a linear plasmid, presumably because both compete in trans with telomeric chromatin for factor(s) important for TPE. This reduction in TPE, observed in three different strains, was demonstrated for two different genes, each assayed at a different telomere. In contrast, the addition of internal tracts of telomeric DNA on a circular plasmid had very little effect on TPE. The product of the SIR3 gene, Sir3p, appears to be limiting for TPE. Overexpression of Sir3p completely suppressed the reduction in TPE observed with expression of Rap1δBBp, but did not restore high levels of TPE to cells with extra telomeres. These results suggest that extra telomeres must titrate a factor other than Sir3p that is important for TPE. These results also provide evidence for a terminus-specific binding factor that is a factor with a higher affinity for DNA termini than for nonterminal tracts of telomeric DNA and indicate that this factor is important for TPE. PMID:7705652

  19. DNA binding by c-Ets-1, but not v-Ets, is repressed by an intramolecular mechanism.

    PubMed Central

    Lim, F; Kraut, N; Framptom, J; Graf, T

    1992-01-01

    The E26 avian retrovirus causes an acute leukemia in chickens and transforms both myeloid and erythroid cells. The virus encodes a 135 kDa fusion protein which contains amino acid sequences derived from the viral Gag protein and the two cellular transcription factors c-Myb and c-Ets-1p68. Previously we have shown that like v-myb, v-ets on its own is also active in transformation, but only within the erythroid lineage. To understand better the mechanisms involved in the oncogenic activation of c-Ets-1p68, we used the polyoma PEA3 element, a known Ets binding site, to compare the sequence-specific DNA binding and transactivating properties of v-Ets and c-Ets-1p68. Using Ets protein synthesized in rabbit reticulocyte lysate in gel retardation assays, we detected little binding of c-Ets-1p68 to an oligonucleotide containing the PEA3 motif whereas v-Ets bound strongly. However, in transient cotransfection assays in chicken embryo fibroblasts both c-Ets-1p68 and v-Ets transactivated transcription from a heterologous promoter linked to PEA3 elements. Interestingly, fragments of c-Ets-1p68 with strong DNA binding activity could be produced by limited proteolysis, indicating that the DNA binding domain is repressed within the full-length molecule. By deletion mapping the DNA binding domain was localized to the most highly conserved region of the Ets-related proteins known as the ETS domain. The C-terminus as well as a region in the middle of the polypeptide chain are involved in repression of DNA binding in c-Ets-1p68. Significantly, v-Ets contains a 16 amino acid substitution at the C-terminus. Our results suggest that intramolecular repression of DNA binding is a regulatory mechanism in c-Ets-1p68 which is lost in v-Ets. Images PMID:1311254

  20. 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. PMID:25791004

  1. 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

  2. FOG-1 recruits the NuRD repressor complex to mediate transcriptional repression by GATA-1

    PubMed Central

    Hong, Wei; Nakazawa, Minako; Chen, Ying-Yu; Kori, Rajashree; Vakoc, Christopher R; Rakowski, Carrie; Blobel, Gerd A

    2005-01-01

    Transcription factor GATA-1 and its cofactor FOG-1 coordinate erythroid cell maturation by activating erythroid-specific genes and repressing genes associated with the undifferentiated state. Here we show that FOG-1 binds to the NuRD corepressor complex in vitro and in vivo. The interaction is mediated by a small conserved domain at the extreme N-terminus of FOG-1 that is necessary and sufficient for NuRD binding. This domain defines a novel repression module found in diverse transcriptional repressors. NuRD is present at GATA-1/FOG-1-repressed genes in erythroid cells in vivo. Point mutations near the N-terminus of FOG-1 that abrogate NuRD binding block gene repression by FOG-1. Finally, the ability of GATA-1 to repress transcription was impaired in erythroid cells expressing mutant forms of FOG-1 that are defective for NuRD binding. Together, these studies show that FOG-1 and likely other FOG-like proteins are corepressors that link GATA factors to histone deacetylation and nucleosome remodeling. PMID:15920470

  3. 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

  4. Enhancer-bound LDB1 regulates a corticotrope promoter-pausing repression program

    PubMed Central

    Zhang, Feng; Tanasa, Bogdan; Merkurjev, Daria; Lin, Chijen; Song, Xiaoyuan; Li, Wenbo; Tan, Yuliang; Liu, Zhijie; Zhang, Jie; Ohgi, Kenneth A.; Krones, Anna; Skowronska-Krawczyk, Dorota; Rosenfeld, Michael G.

    2015-01-01

    Substantial evidence supports the hypothesis that enhancers are critical regulators of cell-type determination, orchestrating both positive and negative transcriptional programs; however, the basic mechanisms by which enhancers orchestrate interactions with cognate promoters during activation and repression events remain incompletely understood. Here we report the required actions of LIM domain-binding protein 1 (LDB1)/cofactor of LIM homeodomain protein 2/nuclear LIM interactor, interacting with the enhancer-binding protein achaete-scute complex homolog 1, to mediate looping to target gene promoters and target gene regulation in corticotrope cells. LDB1-mediated enhancer:promoter looping appears to be required for both activation and repression of these target genes. Although LDB1-dependent activated genes are regulated at the level of transcriptional initiation, the LDB1-dependent repressed transcription units appear to be regulated primarily at the level of promoter pausing, with LDB1 regulating recruitment of metastasis-associated 1 family, member 2, a component of the nucleosome remodeling deacetylase complex, on these negative enhancers, required for the repressive enhancer function. These results indicate that LDB1-dependent looping events can deliver repressive cargo to cognate promoters to mediate promoter pausing events in a pituitary cell type. PMID:25605944

  5. 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

  6. 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

  7. 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

  8. Dual role of NRSF/REST in activation and repression of the glucocorticoid response.

    PubMed

    Abramovitz, Lilach; Shapira, Tamar; Ben-Dror, Iris; Dror, Vardit; Granot, Limor; Rousso, Tal; Landoy, Elad; Blau, Lior; Thiel, Gerald; Vardimon, Lily

    2008-01-01

    Restriction of glutamine synthetase to the nervous system is mainly achieved through the mutual function of the glucocorticoid receptor and the neural restrictive silencing factor, NRSF/REST. Glucocorticoids induce glutamine synthetase expression in neural tissues while NRSF/REST represses the hormonal response in non-neural cells. NRSF/REST is a modular protein that contains two independent repression domains, at the N and C termini of the molecule, and is dominantly expressed in nonneural cells. Neural tissues express however splice variants, REST4/5, which contain the repression domain at the N, but not at the C terminus of the molecule. Here we show that full-length NRSF/REST or its C-terminal domain can inhibit almost completely the induction of gene transcription by glucocorticoids. By contrast, the N-terminal domain not only fails to repress the hormonal response but rather stimulates it markedly. The inductive activity of the N-terminal domain is mediated by hBrm, which is recruited to the promoter only in the concomitant presence of GR. Importantly, a similar inductive activity is also exerted by the splice variant REST4. These findings raise the possibility that NRSF/REST exhibits a dual role in regulation of glutamine synthetase. It represses gene induction in nonneural cells and enhances the hormonal response, via its splice variant, in the nervous system. PMID:17984088

  9. 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

  10. 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

  11. 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

  12. 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

  13. Transcriptional Repression of E-Cadherin by Human Papillomavirus Type 16 E6

    PubMed Central

    D'Costa, Zarina J.; Jolly, Carol; Androphy, Elliot J.; Mercer, Andrew; Matthews, Charles M.; Hibma, Merilyn H.

    2012-01-01

    There is increasing evidence supporting DNA virus regulation of the cell adhesion and tumour suppressor protein, E-cadherin. We previously reported that loss of E-cadherin in human papillomavirus (HPV) type 16-infected epidermis is contributed to by the major viral proto-oncogene E6 and is associated with reduced Langerhans cells density, potentially regulating the immune response. The focus of this study is determining how the HPV16 E6 protein mediates E-cadherin repression. We found that the E-cadherin promoter is repressed in cells expressing E6, resulting in fewer E-cadherin transcripts. On exploring the mechanism for this, repression by increased histone deacetylase activity or by increased binding of trans-repressors to the E-cadherin promoter Epal element was discounted. In contrast, DNA methyltransferase (DNMT) activity was increased in E6 expressing cells. Upon inhibiting DNMT activity using 5-Aza-2′-deoxycytidine, E-cadherin transcription was restored in the presence of HPV16 E6. The E-cadherin promoter was not directly methylated, however a mutational analysis showed general promoter repression and reduced binding of the transactivators Sp1 and AML1 and the repressor Slug. Expression of E7 with E6 resulted in a further reduction in surface E-cadherin levels. This is the first report of HPV16 E6-mediated transcriptional repression of this adhesion molecule and tumour suppressor protein. PMID:23189137

  14. 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

  15. 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

  16. Human SWI-SNF Component BRG1 Represses Transcription of the c-fos Gene

    PubMed Central

    Murphy, Daniel J.; Hardy, Stephen; Engel, Daniel A.

    1999-01-01

    Yeast and mammalian SWI-SNF complexes regulate transcription through active modification of chromatin structure. Human SW-13 adenocarcinoma cells lack BRG1 protein, a component of SWI-SNF that has a DNA-dependent ATPase activity essential for SWI-SNF function. Expression of BRG1 in SW-13 cells potentiated transcriptional activation by the glucocorticoid receptor, which is known to require SWI-SNF function. BRG1 also specifically repressed transcription from a transfected c-fos promoter and correspondingly blocked transcriptional activation of the endogenous c-fos gene. Mutation of lysine residue 798 in the DNA-dependent ATPase domain of BRG1 significantly reduced its ability to repress c-fos transcription. Repression by BRG1 required the cyclic AMP response element of the c-fos promoter but not nearby binding sites for Sp1, YY1, or TFII-I. Using human C33A cervical carcinoma cells, which lack BRG1 and also express a nonfunctional Rb protein, transcriptional repression by BRG1 was weak unless wild-type Rb was also supplied. Interestingly, Rb-dependent repression by BRG1 was found to take place through a pathway that is independent of transcription factor E2F. PMID:10082538

  17. 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. PMID:16769694

  18. 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

  19. Spe3, which encodes spermidine synthase, is required for full repression through NRE(DIT) in Saccharomyces cerevisiae.

    PubMed Central

    Friesen, H; Tanny, J C; Segall, J

    1998-01-01

    We previously identified a transcriptional regulatory element, which we call NRE(DIT), that is required for repression of the sporulation-specific genes, DIT1 and DIT2, during vegetative growth of Saccharomyces cerevisiae. Repression through this element is dependent on the Ssn6-Tup1 corepressor. In this study, we show that SIN4 contributes to NRE(DIT)-mediated repression, suggesting that changes in chromatin structure are, at least in part, responsible for regulation of DIT gene expression. In a screen for additional genes that function in repression of DIT (FRD genes), we recovered alleles of TUP1, SSN6, SIN4, and ROX3 and identified mutations comprising eight complementation groups of FRD genes. Four of these FRD genes appeared to act specifically in NRE(DIT)mediated repression, and four appeared to be general regulators of gene expression. We cloned the gene complementing the frd3-1 phenotype and found that it was identical to SPE3, which encodes spermidine synthase. Mutant spe3 cells not only failed to support complete repression through NRE(DIT) but also had modest defects in repression of some other genes. Addition of spermidine to the medium partially restored repression to spe3 cells, indicating that spermidine may play a role in vivo as a modulator of gene expression. We suggest various mechanisms by which spermidine could act to repress gene expression. PMID:9725830

  20. Region-Specific Activation of oskar mRNA Translation by Inhibition of Bruno-Mediated Repression

    PubMed Central

    Kim, Goheun; Pai, Chin-I; Sato, Keiji; Person, Maria D.; Nakamura, Akira; Macdonald, Paul M.

    2015-01-01

    A complex program of translational repression, mRNA localization, and translational activation ensures that Oskar (Osk) protein accumulates only at the posterior pole of the Drosophila oocyte. Inappropriate expression of Osk disrupts embryonic axial patterning, and is lethal. A key factor in translational repression is Bruno (Bru), which binds to regulatory elements in the osk mRNA 3′ UTR. After posterior localization of osk mRNA, repression by Bru must be alleviated. Here we describe an in vivo assay system to monitor the spatial pattern of Bru-dependent repression, separate from the full complexity of osk regulation. This assay reveals a form of translational activation—region-specific activation—which acts regionally in the oocyte, is not mechanistically coupled to mRNA localization, and functions by inhibiting repression by Bru. We also show that Bru dimerizes and identify mutations that disrupt this interaction to test its role in vivo. Loss of dimerization does not disrupt repression, as might have been expected from an existing model for the mechanism of repression. However, loss of dimerization does impair regional activation of translation, suggesting that dimerization may constrain, not promote, repression. Our work provides new insight into the question of how localized mRNAs become translationally active, showing that repression of osk mRNA is locally inactivated by a mechanism acting independent of mRNA localization. PMID:25723530

  1. Investigating giant (Gt) repression in the formation of partially overlapping pair-rule stripes.

    PubMed

    Ribeiro, Thiago Casé; Ventrice, Glauber; Machado-Lima, Ariane; Andrioli, Luiz Paulo

    2010-11-01

    Drosophila pair-rule genes are expressed in striped patterns with a precise order of overlap between stripes of different genes. We investigated the role of Giant (Gt) in the regulation of even-skipped, hairy, runt, and fushi tarazu stripes formed in the vicinity of Gt expression domains. In gt null embryos, specific stripes of eve, h, run, and ftz are disrupted. With an ectopic expression system, we verified that stripes affected in the mutant are also repressed. Simultaneously hybridizing gt misxpressing embryos with two pair-rule gene probes, we were able to distinguish differences in the repression of pairs of stripes that overlap extensively. Together, our results showed Gt repression roles in the regulation of two groups of partially overlapping stripes and that Gt morphogen activity is part of the mechanism responsible for the differential positioning of these stripes borders. We discuss the possibility that other factors regulate Gt stripe targets as well. PMID:20925117

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

    PubMed

    Du, Dan; Qi, Lei S

    2016-01-01

    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. PMID:26729914

  3. The effects of social context and defensiveness on the physiological responses of repressive copers.

    PubMed

    Barger, S D; Kircher, J C; Croyle, R T

    1997-11-01

    In previous research (T.L. Newton & R.J. Contrada, 1992), social context was found to moderate exaggerated physiological reactivity among individuals identified as using a repressive coping style. In this experiment, 119 undergraduates were classified into low-anxious, high-anxious, repressor, and defensive high-anxious coping categories. All participants completed a stressful speech task under either a public or private social context condition. The experimental social context was related to physiological reactivity and self-reported affect but did not moderate reactivity among repressive copers. Additionally, reactivity among repressive copers was not attributable to high defensiveness alone. Consistent with a theory of emotional inhibition, nonspecific skin conductance responses, but not heart rate, discriminated between repressors and nonrepressors. PMID:9417480

  4. Overcome of Carbon Catabolite Repression of Bioinsecticides Production by Sporeless Bacillus thuringiensis through Adequate Fermentation Technology.

    PubMed

    Ben Khedher, Saoussen; Jaoua, Samir; Zouari, Nabil

    2014-01-01

    The overcoming of catabolite repression, in bioinsecticides production by sporeless Bacillus thuringiensis strain S22 was investigated into fully controlled 3 L fermenter, using glucose based medium. When applying adequate oxygen profile throughout the fermentation period (75% oxygen saturation), it was possible to partially overcome the catabolite repression, normally occurring at high initial glucose concentrations (30 and 40 g/L glucose). Moreover, toxin production yield by sporeless strain S22 was markedly improved by the adoption of the fed-batch intermittent cultures technology. With 22.5 g/L glucose used into culture medium, toxin production was improved by about 36% when applying fed-batch culture compared to one batch. Consequently, the proposed fed-batch strategy was efficient for the overcome of the carbon catabolite repression. So, it was possible to overproduce insecticidal crystal proteins into highly concentrated medium. PMID:25309756

  5. INDUCTION AND REPRESSION OF l-ARABINOSE ISOMERASE IN PEDIOCOCCUS PENTOSACEUS1

    PubMed Central

    Dobrogosz, Walter J.; DeMoss, Ralph D.

    1963-01-01

    Dobrogosz, Walter J. (University of Illinois, Urbana) and Ralph D. DeMoss. Induction and repression of l-arabinose isomerase in Pediococcus pentosaceus. J. Bacteriol. 85:1350–1355. 1963.—The inducible l-arabinose isomerase of Pediococcus pentosaceus can be rapidly and conveniently measured in whole-cell preparations by use of a standard colorimetric procedure originally developed for studies with cell-free enzyme preparations. The enzyme is measured by its ability to catalyze the isomerization of l-arabinose to l-ribulose. Whole cells suspended in a suitable buffer and pretreated with toluene were shown to exhibit this isomerase activity at a level comparable with that observed in cell-free enzyme preparations. Conditions for optimal induction of l-arabinose isomerase are described. In addition, it was determined that the formation of this enzyme is subject to repression by glucose, i.e., via catabolite repression. PMID:14047229

  6. In simple synthetic promoters YY1-induced DNA bending is important in transcription activation and repression.

    PubMed Central

    Kim, J; Shapiro, D J

    1996-01-01

    Depending on promoter context, YY1 can activate or repress transcription, or provide a site for transcription initiation. To investigate whether the ability of YY1 to induce DNA bending influenced its ability to activate and repress transcription, simple synthetic promoters were constructed in which the YY1 binding site was inserted between the TATA box and either the NF1 or AP1 recognition sequences. In transient transfections of COS cells, the NF1YY1TATA and NF1RYY1TATA promoters exhibited a dramatic 15-20-fold increase in correctly initiated transcription. These promoters exhibited even larger 60-80-fold increases in transcription in HeLa cells. Neither multiple copies of the YY1 binding site alone, nor placement of a YY1 site upstream of the NF1 site activated transcription. Deletion of 4 bp between the NF1 and YY1 sites, which changes the phase of the DNA bends, abolished the 16-fold activation of transcription by NF1YY1TATA. Insertion of the YY1 site between the AP1 site and the TATA box decreased transcription approximately 3-fold. Replacing the YY1 binding site with an intrinsic DNA bending sequence mimicked this transcription repression. Sequences of similar length which do not bend DNA fail to repress AP1-mediated transcription. Gel mobility shift assays were used to show that binding of YY1 to its recognition sequence did not repress binding of AP1 to its recognition sequences. Our data indicate that YY1-induced DNA bending may activate and repress transcription by changing the spatial relationships between transcription activators and components of the basal transcription apparatus. PMID:8932392

  7. 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

  8. 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

  9. Repression of Hybrid Dysgenesis in Drosophila Melanogaster by Individual Naturally Occurring P Elements

    PubMed Central

    Rasmusson, K. E.; Raymond, J. D.; Simmons, M. J.

    1993-01-01

    Individual P elements that were genetically isolated from wild-type strains were tested for their abilities to repress two aspects of hybrid dysgenesis: gonadal dysgenesis and mutability of a double-P element-insertion allele of the singed locus (sn(w)). These elements were also characterized by Southern blotting, polymerase chain reaction amplification and DNA sequencing. Three of the elements were 1.1-kb KP elements, one was a 1.2-kb element called D50, and one was a 0.5-kb element called SP. These three types of elements could encode polypeptides of 207, 204, and 14 amino acids, respectively. Gonadal dysgenesis was repressed by two of the KP elements (denoted KP(1) and KP(6)) and by SP, but not by the third KP element (KP(D)), nor by D50. Repression of gonadal dysgenesis was mediated by a maternal effect, or by a combination of zygotic and maternal effects generated by the P elements themselves. The mutability of sn(w) was repressed by the KP(1) and KP(6) elements, by D50 and by SP, but not by KP(D); however, the SP element repressed sn(w) mutability only when the transposase came from complete P elements and the D50 element repressed it only when the transposase came from the modified P element known as Δ2-3. In all cases, repression of sn(w) mutability appeared to be mediated by a zygotic effect of the isolated P element. Each of the isolated elements was also tested for its ability to suppress the phenotype of a P-insertion mutation of the vestigial locus (vg(21-3)). D50 was a moderate suppressor whereas SP and the three KP elements had little or no effect. These results indicate that each isolated P element had its own profile of repression and suppression abilities. It is suggested that these abilities may be mediated by P-encoded polypeptides or by antisense P RNAs initiated from external genomic promoters. PMID:8384145

  10. Dominant negative autoregulation limits steady-state repression levels in gene networks.

    PubMed

    Semsey, Szabolcs; Krishna, Sandeep; Erdossy, János; Horváth, Péter; Orosz, László; Sneppen, Kim; Adhya, Sankar

    2009-07-01

    Many transcription factors repress transcription of their own genes. Negative autoregulation has been shown to reduce cell-cell variation in regulatory protein levels and speed up the response time in gene networks. In this work we examined transcription regulation of the galS gene and the function of its product, the GalS protein. We observed a unique operator preference of the GalS protein characterized by dominant negative autoregulation. We show that this pattern of regulation limits the repression level of the target genes in steady states. We suggest that transcription factors with dominant negative autoregulation are designed for regulating gene expression during environmental transitions. PMID:19429616

  11. Saccharomyces cerevisiae mutants resistant to catabolite repression: use in cheese whey hydrolysate fermentation

    SciTech Connect

    Bailey, R.B.; Benitez, T.; Woodward, A.

    1982-09-01

    Mutants of an industrial-type strain of Saccharomyces cerevisiae which rapidly and completely fermented equimolar mixtures of glucose and galactose to ethanol were isolated. These mutants fell into two general phenotypic classes based upon their fermentation kinetics and enzyme induction patterns. One class apparently specifically effects the utilization of galactose and allows sequential utilization of first glucose and then galactose in an anaerobic fermentation. The second class of mutants was resistant to general catabolite repression and produced maltase, invertase, and galactokinase in the presence of repressive levels of glucose. These mutants were completely dominant and appear to represent an as yet undescribed class of mutant. (Refs. 23).

  12. 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.

  13. 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

  14. 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

  15. Glucose repression of yeast mitochondrial transcription: kinetics of derepression and role of nuclear genes.

    PubMed Central

    Ulery, T L; Jang, S H; Jaehning, J A

    1994-01-01

    Yeast mitochondrial transcript and gene product abundance has been observed to increase upon release from glucose repression, but the mechanism of regulation of this process has not been determined. We report a kinetic analysis of this phenomenon, which demonstrates that the abundance of all classes of mitochondrial RNA changes slowly relative to changes observed for glucose-repressed nuclear genes. Several cell doublings are required to achieve the 2- to 20-fold-higher steady-state levels observed after a shift to a nonrepressing carbon source. Although we observed that in some yeast strains the mitochondrial DNA copy number also increases upon derepression, this does not seem to play the major role in increased RNA abundance. Instead we found that three- to sevenfold increases in RNA synthesis rates, measured by in vivo pulse-labelling experiments, do correlate with increased transcript abundance. We found that mutations in the SNF1 and REG1 genes, which are known to affect the expression of many nuclear genes subject to glucose repression, affect derepression of mitochondrial transcript abundance. These genes do not appear to regulate mitochondrial transcript levels via regulation of the nuclear genes RPO41 and MTF1, which encode the subunits of the mitochondrial RNA polymerase. We conclude that a nuclear gene-controlled factor(s) in addition to the two RNA polymerase subunits must be involved in glucose repression of mitochondrial transcript abundance. Images PMID:8289797

  16. Requirement for Rgr1 and Sin4 in Rme1-Dependent Repression in Saccharomyces Cerevisiae

    PubMed Central

    Covitz, P. A.; Song, W.; Mitchell, A. P.

    1994-01-01

    RME1 is a zinc-finger protein homolog that functions as a repressor of the meiotic activator IME1. RME1 is unusual among yeast repressors in two respects: it acts over a considerable distance (2 kbp) and it can activate transcription from a binding site separated from its natural flanking region. To identify genes required for RME1 to exert repression, we have selected mutants with improved RME1-dependent activation. One rare mutant was defective in RME1-dependent repression of an artificial reporter gene as well as the native IME1 gene. The mutation permits sporulation of a/a diploids, which express RME1 from its natural promoter, and of a/α diploids constructed to express RME1 from the GAL1 promoter. The mutation also causes temperature-sensitive growth and a methionine or cysteine requirement. Analysis of a complementing genomic clone indicates that the mutation lies in a known essential gene, RGR1. Prior studies have indicated a functional relationship between RGR1 and SIN4 (also called TSF3); we have found that a sin4 null mutation also causes a defect in RME1-dependent repression and a methionine or cysteine requirement. The rgr1 and sin4 mutations do not cause a reduction of RME1 polypeptide levels. The defect in RME1-dependent repression may result from effects of sin4 and, presumably, rgr1 on chromatin structure. PMID:7851756

  17. Improving Discipline in the Secondary School. A Catalogue of Alternatives to Repression. An Occasional Paper.

    ERIC Educational Resources Information Center

    Howard, Eugene R.; Jenkins, John M.

    The usual approach to improving discipline in the schools is the repressive approach -- more rules, stricter enforcement, more efficient pupil surveillance, suspensions of privileges, or additional rules imposed by the board of education. School administrators, faced with increased public concern and lacking well-defined alternatives to such…

  18. 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…

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

    PubMed Central

    McCall, K; Bender, W

    1996-01-01

    The Polycomb group (PcG) of genes are required for maintenance of the repressed state of the homeotic genes in Drosophila. There are similarities between the PcG repression and mating-type silencing in yeast or heterochromatic position effect in Drosophila, which suggest that PcG repression may involve a highly compacted chromatin structure. To test for such a structure, heterologous DNA- binding proteins were used as probes for DNA accessibility in Drosophila embryos. Binding sites for the yeast transcriptional activator GAL4 and for bacteriophage T7 RNA polymerase were inserted into the bithorax (bx) regulatory region of the endogenous Ultrabithorax (Ubx) gene, which is regulated by the PcG. Ubiquitously expressed GAL4 protein directs transcription through its binding sites only in the posterior segments where the bx region is active. The block to GAL4 activation in the more anterior segments is dependent on Polycomb (Pc) function. In contrast, T7 RNA polymerase can transcribe from its target promoter in all segments of the embryo. Thus, Pc-mediated repression blocks activated polymerase II transcription, but does not simply exclude all proteins. Images PMID:8599940

  20. 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

  1. RUNX1 represses the erythroid gene expression program during megakaryocytic differentiation.

    PubMed

    Kuvardina, Olga N; Herglotz, Julia; Kolodziej, Stephan; Kohrs, Nicole; Herkt, Stefanie; Wojcik, Bartosch; Oellerich, Thomas; Corso, Jasmin; Behrens, Kira; Kumar, Ashok; Hussong, Helge; Urlaub, Henning; Koch, Joachim; Serve, Hubert; Bonig, Halvard; Stocking, Carol; Rieger, Michael A; Lausen, Jörn

    2015-06-01

    The activity of antagonizing transcription factors represents a mechanistic paradigm of bidirectional lineage-fate control during hematopoiesis. At the megakaryocytic/erythroid bifurcation, the cross-antagonism of krueppel-like factor 1 (KLF1) and friend leukemia integration 1 (FLI1) has such a decisive role. However, how this antagonism is resolved during lineage specification is poorly understood. We found that runt-related transcription factor 1 (RUNX1) inhibits erythroid differentiation of murine megakaryocytic/erythroid progenitors and primary human CD34(+) progenitor cells. We show that RUNX1 represses the erythroid gene expression program during megakaryocytic differentiation by epigenetic repression of the erythroid master regulator KLF1. RUNX1 binding to the KLF1 locus is increased during megakaryocytic differentiation and counterbalances the activating role of T-cell acute lymphocytic leukemia 1 (TAL1). We found that corepressor recruitment by RUNX1 contributes to a block of the KLF1-dependent erythroid gene expression program. Our data indicate that the repressive function of RUNX1 influences the balance between erythroid and megakaryocytic differentiation by shifting the balance between KLF1 and FLI1 in the direction of FLI1. Taken together, we show that RUNX1 is a key player within a network of transcription factors that represses the erythroid gene expression program. PMID:25911237

  2. 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

  3. Reduced expression of ribosomal proteins relieves microRNA-mediated repression.

    PubMed

    Janas, Maja M; Wang, Eric; Love, Tara; Harris, Abigail S; Stevenson, Kristen; Semmelmann, Karlheinz; Shaffer, Jonathan M; Chen, Po-Hao; Doench, John G; Yerramilli, Subrahmanyam V B K; Neuberg, Donna S; Iliopoulos, Dimitrios; Housman, David E; Burge, Christopher B; Novina, Carl D

    2012-04-27

    MicroRNAs (miRNAs) regulate physiological and pathological processes by inducing posttranscriptional repression of target messenger RNAs (mRNAs) via incompletely understood mechanisms. To discover factors required for human miRNA activity, we performed an RNAi screen using a reporter cell line of miRNA-mediated repression of translation initiation. We report that reduced expression of ribosomal protein genes (RPGs) dissociated miRNA complexes from target mRNAs, leading to increased polysome association, translation, and stability of miRNA-targeted mRNAs relative to untargeted mRNAs. RNA sequencing of polysomes indicated substantial overlap in sets of genes exhibiting increased or decreased polysomal association after Argonaute or RPG knockdowns, suggesting similarity in affected pathways. miRNA profiling of monosomes and polysomes demonstrated that miRNAs cosediment with ribosomes. RPG knockdowns decreased miRNAs in monosomes and increased their target mRNAs in polysomes. Our data show that most miRNAs repress translation and that the levels of RPGs modulate miRNA-mediated repression of translation initiation. PMID:22541556

  4. 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.

  5. 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…

  6. 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…

  7. 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.

  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. PTEN represses RNA polymerase III-dependent transcription by targeting the TFIIIB complex.

    PubMed

    Woiwode, Annette; Johnson, Sandra A S; Zhong, Shuping; Zhang, Cheng; Roeder, Robert G; Teichmann, Martin; Johnson, Deborah L

    2008-06-01

    PTEN, a tumor suppressor whose function is frequently lost in human cancers, possesses a lipid phosphatase activity that represses phosphatidylinositol 3-kinase (PI3K) signaling, controlling cell growth, proliferation, and survival. The potential for PTEN to regulate the synthesis of RNA polymerase (Pol) III transcription products, including tRNAs and 5S rRNAs, was evaluated. The expression of PTEN in PTEN-deficient cells repressed RNA Pol III transcription, whereas decreased PTEN expression enhanced transcription. Transcription repression by PTEN was uncoupled from PTEN-mediated effects on the cell cycle and was independent of p53. PTEN acts through its lipid phosphatase activity, inhibiting the PI3K/Akt/mTOR/S6K pathway to decrease transcription. PTEN, through the inactivation of mTOR, targets the TFIIIB complex, disrupting the association between TATA-binding protein and Brf1. Kinetic analysis revealed that PTEN initially induces a decrease in the serine phosphorylation of Brf1, leading to a selective reduction in the occupancy of all TFIIIB subunits on tRNA(Leu) genes, whereas prolonged PTEN expression results in the enhanced serine phosphorylation of Bdp1. Together, these results demonstrate a new class of genes regulated by PTEN through its ability to repress the activation of PI3K/Akt/mTOR/S6K signaling. PMID:18391023

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

    PubMed

    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

  12. 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)

  13. 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…

  14. Catabolite repression in Lactobacillus casei ATCC 393 is mediated by CcpA.

    PubMed Central

    Monedero, V; Gosalbes, M J; Pérez-Martínez, G

    1997-01-01

    The chromosomal ccpA gene from Lactobacillus casei ATCC 393 has been cloned and sequenced. It encodes the CcpA protein, a central catabolite regulator belonging to the LacI-GalR family of bacterial repressors, and shows 54% identity with CcpA proteins from Bacillus subtilis and Bacillus megaterium. The L. casei ccpA gene was able to complement a B. subtilis ccpA mutant. An L. casei ccpA mutant showed increased doubling times and a relief of the catabolite repression of some enzymatic activities, such as N-acetylglucosaminidase and phospho-beta-galactosidase. Detailed analysis of CcpA activity was performed by using the promoter region of the L. casei chromosomal lacTEGF operon which is subject to catabolite repression and contains a catabolite responsive element (cre) consensus sequence. Deletion of this cre site or the presence of the ccpA mutation abolished the catabolite repression of a lacp::gusA fusion. These data support the role of CcpA as a common regulatory element mediating catabolite repression in low-GC-content gram-positive bacteria. PMID:9352913

  15. SOD1 Integrates Signals from Oxygen and Glucose to Repress Respiration

    PubMed Central

    Reddi, Amit R.; Culotta, Valeria C.

    2012-01-01

    Summary Cu/Zn Superoxide Dismutase (SOD1) is an abundant enzyme that has been best studied as a regulator of antioxidant defence. Using the yeast S. 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 in favour of aerobic glycolysis. PMID:23332757

  16. 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 theArabidopsis thaliana PSEUDO-RESPONSE REGULATOR(PRR) family is crucial for proper clock function, and transcriptional control ofPRRsremains incompletely defined. Here, we demonstrate that direct regulation ofPRR5by CIRCADIAN CLOCK-ASSOCIATED1 (CCA1) determines the repression state ofPRR5in the morning. Chromatin immunoprecipitation followed by deep sequencing (ChIP-seq) analyses indicated that CCA1 associates with three separate regions upstream ofPRR5 CCA1 and its homolog LATE ELONGATED HYPOCOTYL (LHY) suppressedPRR5promoter activity in a transient assay. The regions bound by CCA1 in thePRR5promoter gave rhythmic patterns with troughs in the morning, when CCA1 and LHY are at high levels. Furthermore,ChIP-seqrevealed that CCA1 associates with at least 449 loci with 863 adjacent genes. Importantly, this gene set contains genes that are repressed but upregulated incca1 lhydouble mutants in the morning. This study shows that direct binding by CCA1 in the morning provides strong repression ofPRR5, and repression by CCA1 also temporally regulates an evening-expressed gene set that includesPRR5. PMID:26941090

  17. Ring1b bookmarks genes in pancreatic embryonic progenitors for repression in adult β cells.

    PubMed

    van Arensbergen, Joris; García-Hurtado, Javier; Maestro, Miguel Angel; Correa-Tapia, Miguel; Rutter, Guy A; Vidal, Miguel; Ferrer, Jorge

    2013-01-01

    Polycomb-mediated gene repression is essential for embryonic development, yet its precise role in lineage-specific programming is poorly understood. Here we inactivated Ring1b, encoding a polycomb-repressive complex 1 subunit, in pancreatic multipotent progenitors (Ring1b(progKO)). This caused transcriptional derepression of a subset of direct Ring1b target genes in differentiated pancreatic islet cells. Unexpectedly, Ring1b inactivation in differentiated islet β cells (Ring1b(βKO)) did not cause derepression, even after multiple rounds of cell division, suggesting a role for Ring1b in the establishment but not the maintenance of repression. Consistent with this notion, derepression in Ring1b(progKO) islets occurred preferentially in genes that were targeted de novo by Ring1b during pancreas development. The results support a model in which Ring1b bookmarks its target genes during embryonic development, and these genes are maintained in a repressed state through Ring1b-independent mechanisms in terminally differentiated cells. This work provides novel insights into how epigenetic mechanisms contribute to shaping the transcriptional identity of differentiated lineages. PMID:23271347

  18. Proteolysis-independent down-regulation of DELLA repression by the gibberellin receptor GID1

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This paper presents evidence for proteolysis-independent regulation of DELLA repression of gibberellin (GA) signaling in Arabidopsis. DELLA proteins are negative regulators of GA responses including seed germination, stem elongation, and fertility. GA can stimulate GA responses by causing proteolys...

  19. 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

  20. CcpA-mediated repression of Clostridium difficile toxin gene expression.

    PubMed

    Antunes, Ana; Martin-Verstraete, Isabelle; Dupuy, Bruno

    2011-02-01

    The presence of glucose or other rapidly metabolizable carbon sources in the bacterial growth medium strongly represses Clostridium difficile toxin synthesis independently of strain origin. In Gram-positive bacteria, carbon catabolite repression (CCR) is generally regarded as a regulatory mechanism that responds to carbohydrate availability. In the C. difficile genome all elements involved in CCR are present. To elucidate in vivo the role of CCR in C. difficile toxin synthesis, we used the ClosTron gene knockout system to construct mutants of strain JIR8094 that were unable to produce the major components of the CCR signal transduction pathway: the phosphotransferase system (PTS) proteins (Enzyme I and HPr), the HPr kinase/phosphorylase (HprK/P) and the catabolite control protein A, CcpA. Inactivation of the ptsI, ptsH and ccpA genes resulted in derepression of toxin gene expression in the presence of glucose, whereas repression of toxin production was still observed in the hprK mutant, indicating that uptake of glucose is required for repression but that phosphorylation of HPr by HprK is not. C. difficile CcpA was found to bind to the regulatory regions of the tcdA and tcdB genes but not through a consensus cre site motif. Moreover in vivo and in vitro results confirmed that HPr-Ser45-P does not stimulate CcpA-dependent binding to DNA targets. However, fructose-1,6-biphosphate (FBP) alone did increase CcpA binding affinity in the absence of HPr-Ser45-P. These results showed that CcpA represses toxin expression in response to PTS sugar availability, thus linking carbon source utilization to virulence gene expression in C. difficile. PMID:21299645

  1. Specific repression of β-globin promoter activity by nuclear ferritin

    PubMed Central

    Broyles, Robert H.; Belegu, Visar; DeWitt, Christina R.; Shah, Sandeep N.; Stewart, Charles A.; Pye, Quentin N.; Floyd, Robert A.

    2001-01-01

    Developmental hemoglobin switching involves sequential globin gene activations and repressions that are incompletely understood. Earlier observations, described herein, led us to hypothesize that nuclear ferritin is a repressor of the adult β-globin gene in embryonic erythroid cells. Our data show that a ferritin-family protein in K562 cell nuclear extracts binds specifically to a highly conserved CAGTGC motif in the β-globin promoter at −153 to −148 bp from the cap site, and mutation of the CAGTGC motif reduces binding 20-fold in competition gel-shift assays. Purified human ferritin that is enriched in ferritin-H chains also binds the CAGTGC promoter segment. Expression clones of ferritin-H markedly repress β-globin promoter-driven reporter gene expression in cotransfected CV-1 cells in which the β-promoter has been stimulated with the transcription activator erythroid Krüppel-like factor (EKLF). We have constructed chloramphenicol acetyltransferase reporter plasmids containing either a wild-type or mutant β-globin promoter for the −150 CAGTGC motif and have compared the constructs for susceptibility to repression by ferritin-H in cotransfection assays. We find that stimulation by cotransfected EKLF is retained with the mutant promoter, whereas repression by ferritin-H is lost. Thus, mutation of the −150 CAGTGC motif not only markedly reduces in vitro binding of nuclear ferritin but also abrogates the ability of expressed ferritin-H to repress this promoter in our cell transfection assay, providing a strong link between DNA binding and function, and strong support for our proposal that nuclear ferritin-H is a repressor of the human β-globin gene. Such a repressor could be helpful in treating sickle cell and other genetic diseases. PMID:11481480

  2. 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.

  3. 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

  4. The osmoregulatory pathway represses mating pathway activity in Saccharomyces cerevisiae: isolation of a FUS3 mutant that is insensitive to the repression mechanism.

    PubMed Central

    Hall, J P; Cherkasova, V; Elion, E; Gustin, M C; Winter, E

    1996-01-01

    Mitogen-activated protein (MAP) kinase cascades are conserved signal transduction pathways that are required for eukaryotic cells to respond to a variety of stimuli. Multiple MAP kinase pathways can function within a single cell type; therefore, mechanisms that insulate one MAP kinase pathway from adventitious activations by parallel pathways may exist. We have studied interactions between the mating pheromone response and the osmoregulatory (high-osmolarity glycerol response [HOG]) pathways in Saccharomyces cerevisiae which utilize the MAP kinases Fus3p and Hog1p, respectively. Inactivating mutations in HOG pathway kinases cause an increase in the phosphotyrosine content of Fus3p, greater expression of pheromone-responsive genes, and increased sensitivity to growth arrest by pheromone. Therefore, the HOG pathway represses mating pathway activity. In a HOG1+ strain, Fus3p phosphotyrosine increases modestly and transiently following an increase in the extracellular osmolarity; however, it increases to a greater extent and for a sustained duration in a hog1-delta strain. Thus, the HOG-mediated repression of mating pathway activity may insulate the mating pathway from activation by osmotic stress. A FUS3 allele whose gene product is resistant to the HOG-mediated repression of its phosphotyrosine content has been isolated. This mutant encodes an amino acid substitution in the highly conserved DPXDEP motif in subdomain XI. Other investigators have shown that the corresponding amino acid is also mutated in a gain-of-function allele of the MAP kinase encoded by the rolled locus in Drosophila melanogaster. These data suggest that the DPXDEP motif plays a role in the negative regulation of MAP kinases. PMID:8943326

  5. Msx1 homeodomain transcription factor and TATA-binding protein interact to repress the expression of the glycoprotein hormone α subunit gene.

    PubMed

    Park, Ki-Sun; Kim, Kee K; Kim, Kyoon Eon

    Studying the regulatory mechanism of the glycoprotein hormone α subunit (αGSU) gene in thyrotropes is essential for understanding the synthesis of functional thyroid-stimulating hormone (TSH). Here, we investigated the influence of a homeodomain transcription factor Msx1 (Msh homeobox 1) on αGSU expression in thyrotropes. The transient expression of Msx1 inhibited the activity of an αGSU reporter gene, as well as its endogenous mRNA level in thyrotrope-derived αTSH cells. Luciferase reporter assays with serial deletion constructs and a close examination of the sequences revealed that the putative Msx1 binding site (PMS) in the αGSU promoter is not responsible for Msx1-mediated transcriptional repression. We also identified the TATA-box binding protein (TBP) as an interacting protein in thyrotropes. Interaction of TBP with Msx1 attenuates the inhibitory effect of Msx1 on αGSU gene expression in a DNA binding-independent manner. Furthermore, transient transfection studies with mutant Msx1 revealed that the interaction of TBP and Msx1 is critical for Msx1-mediated transcriptional repression of the αGSU. These results suggest that Msx1 functions as a transcriptional repressor of αGSU and that its interaction with TBP is an integral part of the mechanism by which Msx1 regulates the inhibition of αGSU gene expression. PMID:26505791

  6. GATA-1 Utilizes Ikaros and Polycomb Repressive Complex 2 To Suppress Hes1 and To Promote Erythropoiesis

    PubMed Central

    Ross, Julie; Mavoungou, Lionel; Bresnick, Emery H.

    2012-01-01

    The transcription factor Hairy Enhancer of Split 1 (HES1), a downstream effector of the Notch signaling pathway, is an important regulator of hematopoiesis. Here, we demonstrate that in primary erythroid cells, Hes1 gene expression is transiently repressed around proerythroblast stage of differentiation. Using mouse erythroleukemia cells, we found that the RNA interference (RNAi)-mediated depletion of HES1 enhances erythroid cell differentiation, suggesting that this protein opposes terminal erythroid differentiation. This is also supported by the decreased primary erythroid cell differentiation upon HES1 upregulation in Ikaros-deficient mice. A comprehensive analysis led us to determine that Ikaros favors Hes1 repression in erythroid cells by facilitating recruitment of the master regulator of erythropoiesis GATA-1 alongside FOG-1, which mediates Hes1 repression. GATA-1 is then necessary for the chromatin binding of the NuRD remodeling complex ATPase MI-2, the transcription factor GFI1B, and the histone H3K27 methyltransferase EZH2 along with Polycomb repressive complex 2. We show that EZH2 is required for the transient repression of Hes1 in erythroid cells. In aggregate, our results describe a mechanism whereby GATA-1 utilizes Ikaros and Polycomb repressive complex 2 to promote Hes1 repression as an important step in erythroid cell differentiation. PMID:22778136

  7. GRR1 of Saccharomyces cerevisiae is required for glucose repression and encodes a protein with leucine-rich repeats.

    PubMed Central

    Flick, J S; Johnston, M

    1991-01-01

    Growth of the yeast Saccharomyces cerevisiae on glucose leads to repression of transcription of many genes required for alternative carbohydrate metabolism. The GRR1 gene appears to be of central importance to the glucose repression mechanism, because mutations in GRR1 result in a pleiotropic loss of glucose repression (R. Bailey and A. Woodword, Mol. Gen. Genet. 193:507-512, 1984). We have isolated the GRR1 gene and determined that null mutants are viable and display a number of growth defects in addition to the loss of glucose repression. Surprisingly, grr1 mutations convert SUC2, normally a glucose-repressed gene, into a glucose-induced gene. GRR1 encodes a protein of 1,151 amino acids that is expressed constitutively at low levels in yeast cells. GRR1 protein contains 12 tandem repeats of a sequence similar to leucine-rich motifs found in other proteins that may mediate protein-protein interactions. Indeed, cell fractionation studies are consistent with this view, suggesting that GRR1 protein is tightly associated with a particulate protein fraction in yeast extracts. The combined genetic and molecular data are consistent with the idea that GRR1 protein is a primary response element in the glucose repression pathway and is required for the generation or interpretation of the signal that induces glucose repression. Images PMID:1922034

  8. The FBXL10/KDM2B scaffolding protein associates with novel polycomb repressive complex-1 to regulate adipogenesis.

    PubMed

    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

    2015-02-13

    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

  9. 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

  10. 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

  11. 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. PMID:25280397

  12. PPAR-δ is repressed in Huntington's disease, is required for normal neuronal function and can be targeted therapeutically.

    PubMed

    Dickey, Audrey S; Pineda, Victor V; Tsunemi, Taiji; Liu, Patrick P; Miranda, Helen C; Gilmore-Hall, Stephen K; Lomas, Nicole; Sampat, Kunal R; Buttgereit, Anne; Torres, Mark-Joseph Manalang; Flores, April L; Arreola, Martin; Arbez, Nicolas; Akimov, Sergey S; Gaasterland, Terry; Lazarowski, Eduardo R; Ross, Christopher A; Yeo, Gene W; Sopher, Bryce L; Magnuson, Gavin K; Pinkerton, Anthony B; Masliah, Eliezer; La Spada, Albert R

    2016-01-01

    Huntington's disease (HD) is a progressive neurodegenerative disorder caused by a CAG trinucleotide repeat expansion in the huntingtin (HTT) gene, which encodes a polyglutamine tract in the HTT protein. We found that peroxisome proliferator-activated receptor delta (PPAR-δ) interacts with HTT and that mutant HTT represses PPAR-δ-mediated transactivation. Increased PPAR-δ transactivation ameliorated mitochondrial dysfunction and improved cell survival of neurons from mouse models of HD. Expression of dominant-negative PPAR-δ in the central nervous system of mice was sufficient to induce motor dysfunction, neurodegeneration, mitochondrial abnormalities and transcriptional alterations that recapitulated HD-like phenotypes. Expression of dominant-negative PPAR-δ specifically in the striatum of medium spiny neurons in mice yielded HD-like motor phenotypes, accompanied by striatal neuron loss. In mouse models of HD, pharmacologic activation of PPAR-δ using the agonist KD3010 improved motor function, reduced neurodegeneration and increased survival. PPAR-δ activation also reduced HTT-induced neurotoxicity in vitro and in medium spiny-like neurons generated from stem cells derived from individuals with HD, indicating that PPAR-δ activation may be beneficial in HD and related disorders. PMID:26642438

  13. The binding capability of plasma phospholipid transfer protein, but not HDL pool size, is critical to repress LPS induced inflammation

    PubMed Central

    Yu, Yang; Cui, Yingjie; Zhao, Yanan; Liu, Shuai; Song, Guohua; Jiao, Peng; Li, Bin; Luo, Tian; Guo, Shoudong; Zhang, Xiangjian; Wang, Hao; Jiang, Xian-Cheng; Qin, Shucun

    2016-01-01

    Phospholipid transfer protein (PLTP) participates in high density lipoprotein (HDL) metabolism. Increased plasma PLTP activity was observed in lipopolysaccharide (LPS) triggered acute inflammatory diseases. This study aimed to determine the exact role of PLTP in LPS induced inflammation. HDL pool size was shrunk both in PLTP deficient mice (PLTP−/−) and PLTP transgenic mice (PLTP-Tg). PLTP displayed a strong protective effect on lethal endotoxemia in mice survival study. Furthermore, after LPS stimulation, the expression of pro-inflammatory cytokines were increased in bone marrow derived macrophage (BMDM) from PLTP−/−, while decreased in BMDM from PLTP-Tg compared with BMDM from wild-type mice (WT). Moreover, LPS induced nuclear factor kappa-B (NFκB) activation was enhanced in PLTP−/− BMDM or PLTP knockdown RAW264.7. Conversely, PLTP overexpression countered the NFκB activation in LPS challenged BMDM. Additionally, the activation of toll like receptor 4 (TLR4) induced by LPS showed no alteration in PLTP−/− BMDM. Finally, PLTP could bind to LPS, attenuate the pro-inflammatory effects of LPS, and improve the cell viability in vitro. To sum up, these findings elucidated that PLTP repressed LPS induced inflammation due to extracellular LPS binding capability, and the protective effects were not related to HDL pool size in mice. PMID:26857615

  14. Structure-function analysis of yeast hexokinase: structural requirements for triggering cAMP signalling and catabolite repression.

    PubMed Central

    Kraakman, L S; Winderickx, J; Thevelein, J M; De Winde, J H

    1999-01-01

    In baker's yeast (Saccharomyces cerevisiae) the hexokinases PI (Hxk1) and PII (Hxk2) are required for triggering of the activation of the Ras-cAMP pathway and catabolite repression. Specifically, Hxk2 is essential for the establishment of glucose repression, whereas either Hxk1 or Hxk2 can sustain fructose repression. Previous studies have suggested that the extent of glucose repression is inversely correlated with hexokinase catalytic activity and hence with an adequate elevation of intracellular sugar phosphate levels. However, several lines of evidence indicate that glucose 6-phosphate is not the trigger of catabolite repression in yeast. In the present study we employed site-directed mutagenesis of amino acids important for the binding of sugar and ATP, for efficient phosphoryl transfer and for the closure of the substrate-binding cleft, to obtain an insight into the structural requirements of Hxk2 for sugar-induced signalling. We show that the ATP-binding Lys-111 is not essential for catalysis in vivo or for signal triggering. Substitution of the catalytic-centre Asp-211 caused loss of catalytic activity, but high-affinity sugar binding was retained. However, this was not sufficient to cause cAMP activation nor catabolite repression. Mutation of Ser-158 abrogated glucose-induced, but not fructose-induced, repression. Moreover, 2-deoxyglucose sustained repression despite an extremely low catalytic activity. We conclude that the establishment of catabolite repression is dependent on the onset of the phosphoryl transfer reaction on hexokinase and is probably related to the stable formation of a transition intermediate and concomitant conformational changes within the enzyme. In contrast, the role of Hxk2 in Ras-cAMP activation seems to be directly connected to its catalytic function. The implications of this model are discussed. PMID:10493925

  15. 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

  16. 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. PMID:26306848

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

    PubMed Central

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

    2016-01-01

    Summary 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

  18. 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. PMID:20845577

  19. Development of a repressible mycobacterial promoter system based on two transcriptional repressors

    PubMed Central

    Boldrin, Francesca; Casonato, Stefano; Dainese, Elisa; Sala, Claudia; Dhar, Neeraj; Palù, Giorgio; Riccardi, Giovanna; Cole, Stewart T.; Manganelli, Riccardo

    2010-01-01

    Tightly regulated gene expression systems represent invaluable tools for studying gene function and for the validation of drug targets in bacteria. While several regulated bacterial promoters have been characterized, few of them have been successfully used in mycobacteria. In this article we describe the development of a novel repressible promoter system effective in both fast- and slow-growing mycobacteria based on two chromosomally encoded repressors, dependent on tetracycline (TetR) and pristinamycin (Pip), respectively. This uniqueness results in high versatility and stringency. Using this method we were able to obtain an ftsZ conditional mutant in Mycobacterium smegmatis and a fadD32 conditional mutant in Mycobacterium tuberculosis, confirming their essentiality for bacterial growth in vitro. This repressible promoter system could also be exploited to regulate gene expression during M. tuberculosis intracellular growth. PMID:20406773

  20. 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

  1. Selenite transiently represses transcription of photosynthesis-related genes in potato leaves.

    PubMed

    Poggi, Valeria; Del Vescovo, Valerio; Di Sanza, Claudio; Negri, Rodolfo; Hochkoeppler, Alejandro

    2008-01-01

    A striking response of potato leaves to aspersion with selenite was observed at the transcriptional level by means of cDNA microarrays analysis. This response is characterized by a general transient repression of genes coding for components of photosynthetic systems and of other light-regulated genes. In particular, maximal repression was observed 8 h after selenite aspersion, while 24 h after the treatment a complete recovery of normal transcriptional levels was detected. Another general feature of the transcriptional response to selenite is represented by the transcriptional induction of genes related to amino acid metabolism, and to stress defense; interestingly, two genes coding for glutathione S-transferases were found early-induced upon selenite treatment. PMID:17846914

  2. 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

  3. 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

  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. PMID:10862881

  5. 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

  6. Gfi1 and Gfi1b Repress Rag Transcription in Plasmacytoid Dendritic Cells In Vitro

    PubMed Central

    Chow, Kwan T.; Schulz, Danae; McWhirter, Sarah M.; Schlissel, Mark S.

    2013-01-01

    Growth factor independence genes (Gfi1 and Gfi1b) repress recombination activating genes (Rag) transcription in developing B lymphocytes. Because all blood lineages originate from hematopoietic stem cells (HSCs) and different lineage progenitors have been shown to share transcription factor networks prior to cell fate commitment, we hypothesized that GFI family proteins may also play a role in repressing Rag transcription or a global lymphoid transcriptional program in other blood lineages. We tested the level of Rag transcription in various blood cells when Gfi1 and Gfi1b were deleted, and observed an upregulation of Rag expression in plasmacytoid dendritic cells (pDCs). Using microarray analysis, we observed that Gfi1 and Gfi1b do not regulate a lymphoid or pDC-specific transcriptional program. This study establishes a role for Gfi1 and Gfi1b in Rag regulation in a non-B lineage cell type. PMID:24086657

  7. 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

  8. Huckebein is part of a combinatorial repression code in the anterior blastoderm.

    PubMed

    Andrioli, Luiz Paulo; Digiampietri, Luciano Antonio; de Barros, Lilian Ponce; Machado-Lima, Ariane

    2012-01-01

    The hierarchy of the segmentation cascade responsible for establishing the Drosophila body plan is composed by gap, pair-rule and segment polarity genes. However, no pair-rule stripes are formed in the anterior regions of the embryo. This lack of stripe formation, as well as other evidence from the literature that is further investigated here, led us to the hypothesis that anterior gap genes might be involved in a combinatorial mechanism responsible for repressing the cis-regulatory modules (CRMs) of hairy (h), even-skipped (eve), runt (run), and fushi-tarazu (ftz) anterior-most stripes. In this study, we investigated huckebein (hkb), which has a gap expression domain at the anterior tip of the embryo. Using genetic methods we were able to detect deviations from the wild-type patterns of the anterior-most pair-rule stripes in different genetic backgrounds, which were consistent with Hkb-mediated repression. Moreover, we developed an image processing tool that, for the most part, confirmed our assumptions. Using an hkb misexpression system, we further detected specific repression on anterior stripes. Furthermore, bioinformatics analysis predicted an increased significance of binding site clusters in the CRMs of h 1, eve 1, run 1 and ftz 1when Hkb was incorporated in the analysis, indicating that Hkb plays a direct role in these CRMs. We further discuss that Hkb and Slp1, which is the other previously identified common repressor of anterior stripes, might participate in a combinatorial repression mechanism controlling stripe CRMs in the anterior parts of the embryo and define the borders of these anterior stripes. PMID:22027434

  9. 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

  10. Post-transcriptional mechanisms contribute to Etv2 repression during vascular development

    PubMed Central

    Moore, John C.; Sheppard, Sarah; Shestopalov, Ilya A.; Chen, James K.; Lawson, Nathan

    2014-01-01

    etv2 is an endothelial-specific ETS transcription factor that is essential for vascular differentiation and morphogenesis in vertebrates. While recent data suggest that Etv2 is dynamically regulated during vascular development, little is known about the mechanisms involved in this process. Here, we find that etv2 transcript and protein expression are highly dynamic during zebrafish vascular development, with both apparent during early somitogenesis and subsequently down-regulated as development proceeds. Inducible knockdown of Etv2 in zebrafish embryos prior to mid-somitogenesis stages, but not later, caused severe vascular defects, suggesting a specific role in early commitment of lateral mesoderm to the endothelial linage. Accordingly, Etv2-overexpressing cells showed an enhanced ability to commit to endothelial lineages in mosaic embryos. We further find that the etv2 3’ untranslated region (UTR) is capable of repressing an endothelial autonomous transgene and contains binding sites for members of the let-7 family of microRNAs. Ectopic expression of let-7a could repress the etv2 3’UTR in sensor assays and was also able to block endogenous Etv2 protein expression, leading to concomitant reduction of endothelial genes. Finally, we observed that Etv2 protein levels persisted in maternal-zygotic dicer1 mutant embryos, suggesting that microRNAs contribute to its repression during vascular development. Taken together, our results suggest that etv2 acts during early development to specify endothelial lineages and is then down-regulated, in part through post-transcriptional repression by microRNAs, to allow normal vascular development. PMID:24036310

  11. Control of mRNA turnover as a mechanism of glucose repression in Saccharomyces cerevisiae.

    PubMed

    Scheffler, I E; de la Cruz, B J; Prieto, S

    1998-11-01

    The phenomenon of glucose repression in yeast is concerned with the repression of a large number of genes when glucose is an abundant carbon source and almost all of the energy requirements of the cell can be satisfied from glycolysis. Prominent among the repressed genes are those encoding mitochondrial proteins required for respiration and oxidative phosphorylation. Past studies have characterized a pathway by which a signal generated from extracellular glucose is transmitted to the nucleus. The ultimate outcome is the repression of transcription of numerous genes, but also the induction of a limited number of others. The emphasis has been almost exclusively on transcriptional control mechanisms. A discovery made originally with the transcript of the SDH2 gene prompted an investigation of post-transcriptional mechanisms, and more specifically a study of the turnover rate of this mRNA in the absence and presence of glucose. SDH2 mRNA has a very short half-life in medium with glucose (YPD) and a significantly longer half-life in medium with glycerol (YPG). Experimental evidence and recent progress in understanding of (1) mRNA turnover in yeast and (2) initiation of translation on the 5' untranslated region of mRNAs, lead to a working hypothesis with the following major features: the carbon source, via a signaling pathway involving kinase/phosphatase activities, controls the rate of initiation, and thus influences a competition between eukaryotic initiation factors (prominently eIF4E, eIF4G, eIF3) binding to the capped mRNA and a decapping activity (DCP1) which is one of the rate limiting activities in the turnover of such mRNAs. PMID:9839444

  12. 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

  13. 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

  14. Identification of Ind transcription activation and repression domains required for dorsoventral patterning of the CNS.

    PubMed

    Von Ohlen, Tonia L; Moses, Cade

    2009-07-01

    Specification of cell fates across the dorsoventral axis of the central nervous system in Drosophila involves the subdivision of the neuroectoderm into three domains that give rise to three columns of neural precursor cells called neuroblasts. Ventral nervous system defective (Vnd), intermediate neuroblasts defective (Ind) and muscle segment homeobox (Msh) are expressed in the three columns from ventral to dorsal, respectively. The products of these genes play multiple important roles in formation and specification of the embryonic nervous system. Ind, for example, is known to play roles in two important processes. First, Ind is essential for formation of neuroblasts conjunction with SoxB class transcription factors. Sox class transcription factors are known to specify neural stem cells in vertebrates. Second, Ind plays an important role in patterning the CNS in conjunction with, vnd and msh, which is also similar to how vertebrates pattern their neural tube. This work focuses two important aspects of Ind function. First, we used multiple approaches to identify and characterize specific domains within the protein that confer repressor or activator ability. Currently, little is known about the presence of activation or repression domains within Ind. Here, we show that transcriptional repression by Ind requires multiple conserved domains within the protein, and that Ind has a transcriptional activation domain. Specifically, we have identified a novel domain, the Pst domain, that has transcriptional repression ability and appears to act independent of interaction with the co-repressor Groucho. This domain is highly conserved among insect species, but is not found in vertebrate Gsh class homeodomain proteins. Second, we show that Ind can and does repress vnd expression, but does so in a stage specific manner. We conclude from this that the function of Ind in regulating vnd expression is one of refinement and maintenance of the dorsal border. PMID:19348939

  15. BMP signaling turns up in fragile X syndrome: FMRP represses BMPR2.

    PubMed

    Broihier, Heather T

    2016-01-01

    Fragile X syndrome is the most common inherited form of intellectual disability and results from a loss of function of the translational repressor FMRP. In this issue of Science Signaling, Kashima et al find that FMRP binds to and represses a specific isoform of BMPR2, a type II bone morphogenetic protein (BMP) receptor. Reducing signaling through this BMP pathway reverses neuroanatomical defects observed in fragile X models. PMID:27273094

  16. λ -prophage induction modeled as a cooperative failure mode of lytic repression

    NASA Astrophysics Data System (ADS)

    Chia, Nicholas; Golding, Ido; Goldenfeld, Nigel

    2009-09-01

    We analyze a system-level model for lytic repression of λ phage in E. coli using reliability theory, showing that the repressor circuit comprises four redundant components whose failure mode is prophage induction. Our model reflects the specific biochemical mechanisms involved in regulation, including long-range cooperative binding, and its detailed predictions for prophage induction in E. coli under ultraviolet radiation are in good agreement with experimental data.

  17. λ-prophage induction modeled as a cooperative failure mode of lytic repression

    NASA Astrophysics Data System (ADS)

    Chia, Nicholas; Golding, Ido; Goldenfeld, Nigel

    2009-03-01

    We analyze a system-level model for lytic repression of λ-phage in E. coli/ using reliability theory, showing that the repressor circuit comprises 4 redundant components whose failure mode is prophage induction. Our model reflects the specific biochemical mechanisms involved in regulation, including long-range cooperative binding, and its detailed predictions for prophage induction in E. coli/ under ultra-violet radiation are in good agreement with experimental data.

  18. 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

  19. Malondialdehyde inhibits an AMPK-mediated nuclear translocation and repression activity of ALDH2 in transcription

    SciTech Connect

    Choi, Ji-Woong; Kim, Jae-Hwan; Cho, Sung-Chun; Ha, Moon-Kyung; Song, Kye-Yong; Youn, Hong-Duk; Park, Sang Chul

    2011-01-07

    Research highlights: {yields} ALDH2 is an MDA-modified protein in old rat kidney tissues. {yields} AMPK associates with ALDH2 and triggers the nuclear localization of ALDH2. {yields} ALDH2 serves as a general transcriptional repressor by associating with HDACs. {yields} MDA inhibits the AMPK-mediated translocation of ALDH2 and its repression activity. -- Abstract: Aging process results from deleterious damages by reactive oxygen species, in particular, various metabolic aldehydes. Aldehyde dehydrogenase 2 (ALDH2) is one of metabolic enzymes detoxifying various aldehydes under oxidative conditions. AMP-activated protein kinase (AMPK) plays a key role in controlling metabolic process. However, little was known about the relationship of ALDH2 with AMPK under oxidative conditions. Here, we, by using MDA-specific monoclonal antibody, screened the tissues of young and old rats for MDA-modified proteins and identified an ALDH2 as a prominent MDA-modified protein band in the old rat kidney tissue. ALDH2 associates with AMPK and is phosphorylated by AMPK. In addition, AICAR, an activator of AMP-activated protein kinase, induces the nuclear translocation of ALDH2. ALDH2 in nucleus is involved in general transcription repression by association with histone deacetylases. Furthermore, MDA modification inhibited the translocation of ALDH2 and the association with AMPK, and ultimately led to de-repression of transcription in the reporter system analysis. In this study, we have demonstrated that ALDH2 acts as a transcriptional repressor in response to AMPK activation, and MDA modifies ALDH2 and inhibits repressive activity of ALDH2 in general transcription. We thus suggest that increasing amount of MDA during aging process may interrupt the nuclear function of ALDH2, modulated by AMPK.

  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. Evolution of VRN2/Ghd7-Like Genes in Vernalization-Mediated Repression of Grass Flowering.

    PubMed

    Woods, Daniel P; McKeown, Meghan A; Dong, Yinxin; Preston, Jill C; Amasino, Richard M

    2016-04-01

    Flowering of many plant species is coordinated with seasonal environmental cues such as temperature and photoperiod. Vernalization provides competence to flower after prolonged cold exposure, and a vernalization requirement prevents flowering from occurring prior to winter. In winter wheat (Triticum aestivum) and barley (Hordeum vulgare), three genes VRN1, VRN2, and FT form a regulatory loop that regulates the initiation of flowering. Prior to cold exposure, VRN2 represses FT. During cold, VRN1 expression increases, resulting in the repression of VRN2, which in turn allows activation of FT during long days to induce flowering. Here, we test whether the circuitry of this regulatory loop is conserved across Pooideae, consistent with their niche transition from the tropics to the temperate zone. Our phylogenetic analyses of VRN2-like genes reveal a duplication event occurred before the diversification of the grasses that gave rise to a CO9 and VRN2/Ghd7 clade and support orthology between wheat/barley VRN2 and rice (Oryza sativa) Ghd7 Our Brachypodium distachyon VRN1 and VRN2 knockdown and overexpression experiments demonstrate functional conservation of grass VRN1 and VRN2 in the promotion and repression of flowering, respectively. However, expression analyses in a range of pooids demonstrate that the cold repression of VRN2 is unique to core Pooideae such as wheat and barley. Furthermore, VRN1 knockdown in B. distachyon demonstrates that the VRN1-mediated suppression of VRN2 is not conserved. Thus, the VRN1-VRN2 feature of the regulatory loop appears to have evolved late in the diversification of temperate grasses. PMID:26848096

  2. Genetic analysis of transcriptional activation and repression in the Tn21 mer operon. [Bacteria

    SciTech Connect

    Ross, W.; Park, S.J.; Summers, A.O. )

    1989-07-01

    Transcription of the Tn21 mercury resistance operon (mer) is controlled by the toxic metal cation Hg(II). This control is mediated by the product of the merR gene, a 144-amino-acid protein which represses transcription of the structural genes (merTPCAD) in the absence of Hg(II) and activates transcription in the presence of Hg(II). We have used a mer-lac transcriptional fusion to obtain regulatory mutants in this metal-responsive system. Some mutants were defective in Hg(II)-induced activation while retaining repression function, others were defective in repression but not activation, and some had lost both functions. Mutations in three of the four cysteine residues of merR resulted in complete loss of Hg(II)-inducible activation but retention of the repressor function. Other lesions adjacent to or very near these cysteines exhibited severely reduced activation and also retained repressor function. There were two putative helix-turn-helix (HTH) domains in merR, and mutants in each had very different phenotypes. A partially dominant mutation in the more amino-terminal region of the two putative HTH regions resulted in loss of both activation and repression, consistent with a role for this region in DNA binding. Mutations in the more centrally located HTH region resulted only in loss of Hg(II)-induced activation. Lesions in the central and in the carboxy-terminal regions of merR exhibited both Hg(II)-independent and Hg(II)-dependent transcriptional activation. The sole cis-acting mutant obtained with this operon fusion strategy, a down-promoter mutation, lies in a highly conserved base in the -35 region of the merTPCAD promoter.

  3. From sensorimotor inhibition to freudian repression: insights from psychosis applied to neurosis.

    PubMed

    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. PMID:23162501

  4. Maintenance of Paternal Methylation and Repression of the Imprinted H19 Gene Requires MBD3

    PubMed Central

    Reese, Kimberly J; Lin, Shu; Verona, Raluca I; Schultz, Richard M; Bartolomei, Marisa S

    2007-01-01

    Paternal repression of the imprinted H19 gene is mediated by a differentially methylated domain (DMD) that is essential to imprinting of both H19 and the linked and oppositely imprinted Igf2 gene. The mechanisms by which paternal-specific methylation of the DMD survive the period of genome-wide demethylation in the early embryo and are subsequently used to govern imprinted expression are not known. Methyl-CpG binding (MBD) proteins are likely candidates to explain how these DMDs are recognized to silence the locus, because they preferentially bind methylated DNA and recruit repression complexes with histone deacetylase activity. MBD RNA and protein are found in preimplantation embryos, and chromatin immunoprecipitation shows that MBD3 is bound to the H19 DMD. To test a role for MBDs in imprinting, two independent RNAi-based strategies were used to deplete MBD3 in early mouse embryos, with the same results. In RNAi-treated blastocysts, paternal H19 expression was activated, supporting the hypothesis that MBD3, which is also a member of the Mi-2/NuRD complex, is required to repress the paternal H19 allele. RNAi-treated blastocysts also have reduced levels of the Mi-2/NuRD complex protein MTA-2, which suggests a role for the Mi-2/NuRD repressive complex in paternal-specific silencing at the H19 locus. Furthermore, DNA methylation was reduced at the H19 DMD when MBD3 protein was depleted. In contrast, expression and DNA methylation were not disrupted in preimplantation embryos for other imprinted genes. These results demonstrate new roles for MBD3 in maintaining imprinting control region DNA methylation and silencing the paternal H19 allele. Finally, MBD3-depleted preimplantation embryos have reduced cell numbers, suggesting a role for MBD3 in cell division. PMID:17708683

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

    PubMed Central

    Yap, Chui-Sun; Peterson, Abigail L; Castellani, Gastone

    2011-01-01

    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 two-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 data set 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. PMID:21623162

  6. 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

  7. Does base-pairing strength play a role in microRNA repression?

    PubMed

    Carmel, Ido; Shomron, Noam; Heifetz, Yael

    2012-11-01

    MicroRNAs (miRNAs) are short, single-stranded RNAs that silence gene expression by either degrading mRNA or repressing translation. Each miRNA regulates a specific set of mRNA "targets" by binding to complementary sequences in their 3' untranslated region. In this study, we examined the importance of the base-pairing strength of the miRNA-target duplex to repression. We hypothesized that if base-pairing strength affects the functionality of miRNA repression, organisms with higher body temperature or that live at higher temperatures will have miRNAs with higher G/C content so that the miRNA-target complex will remain stable. In the nine model organisms examined, we found a significant correlation between the average G/C content of miRNAs and physiological temperature, supporting our hypothesis. Next, for each organism examined, we compared the average G/C content of miRNAs that are conserved among distant organisms and that of miRNAs that are evolutionarily recent. We found that the average G/C content of ancient miRNAs is lower than recent miRNAs in homeotherms, whereas the trend was inversed in poikilotherms, suggesting that G/C content is associated with temperature, thus further supporting our hypothesis. In the organisms examined, the average G/C content of miRNA "seed" sequences was higher than that of mature miRNAs, which was higher than pre-miRNA loops, suggesting an association between the degree of functionality of the sequence and its average G/C content. Our analyses show a possible association between the base-pairing strength of miRNA-targets and the temperature of an organism, suggesting that base-pairing strength plays a role in repression by miRNAs. PMID:23019592

  8. The murine Sim-2 gene product inhibits transcription by active repression and functional interference.

    PubMed

    Moffett, P; Reece, M; Pelletier, J

    1997-09-01

    The Drosophila single-minded (Dsim) gene encodes a master regulatory protein involved in cell fate determination during midline development. This protein is a member of a rapidly expanding family of gene products possessing basic helix-loop-helix (bHLH) and hydrophobic PAS (designated a conserved region among PER, ARNT [aryl hydrocarbon receptor nuclear translocator] and SIM) protein association domains. Members of this family function as central transcriptional regulators in cellular differentiation and in the response to environmental stimuli such as xenobiotics and hypoxia. We have previously identified a murine member of this family, called mSim-2, showing sequence homology to the bHLH and PAS domains of Dsim. Immunoprecipitation experiments with recombinant proteins indicate that mSIM-2 associates with the arnt gene product. In the present work, by using fine-structure mapping we found that the HLH and PAS motifs of both proteins are required for optimal association. Forced expression of GAL4/mSIM-2 fusion constructs in mammalian cells demonstrated the presence of two separable repression domains within the carboxy terminus of mSIM-2. We found that mSIM-2 is capable of repressing ARNT-mediated transcriptional activation in a mammalian two-hybrid system. This effect (i) is dependent on the ability of mSIM-2 and ARNT to heterodimerize, (ii) is dependent on the presence of the mSIM-2 carboxy-terminal repression domain, and (iii) is not specific to the ARNT activation domain. These results suggest that mSIM-2 repression activity can dominantly override the activation potential of adjacent transcription factors. We also demonstrated that mSIM-2 can functionally interfere with hypoxia-inducible factor 1alpha (HIF-1alpha)/ARNT transcription complexes, providing a second mechanism by which mSIM-2 may inhibit transcription. PMID:9271372

  9. 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

  10. 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. PMID:25648574

  11. 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

  12. Sip1 Is a Catabolite Repression-Specific Negative Regulator of Gal Gene Expression

    PubMed Central

    Mylin, L. M.; Bushman, V. L.; Long, R. M.; Yu, X.; Lebo, C. M.; Blank, T. E.; Hopper, J. E.

    1994-01-01

    The yeast Snflp kinase is required for normal expression of amny genes involved in utilization of non-glucose carbon. Snflp is known to associate with several proteins. One is Sip1p, a protein that becomes phosphorylated in the presence of Snflp and thus is a candidate Snflp kinase substrate. We have isolated the SIP1 gene as a multicopy suppressor of the gal83-associated defect in glucose repression of GAL gene expression. Multicopy SIP1 also suppressed the gal82-associated defect in glucose repression, suggesting that SIP1, GAL83 and GAL82 function interdependently. Multicopy SIP1 gene reduces GAL1, GAL2, GAL7 and GAL10 gene expression three- to fourfold in cells grown in the presence of glucose but has no effect in cells grown on nonrepressing carbon. Sip1-deletion cells exhibited a two- to threefold increase in GAL gene expression compared to wild-type cells when grown on glucose. These studies show that SIP1 is a catabolite repression-specific negative regulator of GAL gene expression. Northern analysis revealed two SIP1 transcripts whose relative abundance changed with carbon source. Western blots revealed that Sip1p abundance is not markedly affected by carbon source, suggesting that Sip1p may be regulated post-translationally. PMID:8088514

  13. 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

  14. 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

  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. Epigenetic repression of cardiac progenitor gene expression by Ezh2 is required for postnatal cardiac homeostasis

    PubMed Central

    Delgado-Olguín, Paul; Huang, Yu; Li, Xue; Christodoulou, Danos; Seidman, Christine E.; Seidman, J.G.; Tarakhovsky, Alexander; Bruneau, Benoit G.

    2011-01-01

    Adult-onset diseases can be associated with in utero events, but mechanisms for this remain unknown1,2. The polycomb histone methyltransferase, Ezh2, stabilizes transcription by depositing repressive marks during development that persist into adulthood3–9, but its function in postnatal organ homeostasis is unknown. We show that Ezh2 stabilizes cardiac gene expression and prevents cardiac pathology by repressing the homeodomain transcription factor Six1, which functions in cardiac progenitors but is stably silenced upon cardiac differentiation10. Ezh2 deletion in cardiac progenitors caused postnatal myocardial pathology and destabilized cardiac gene expression with activation of Six1-dependent skeletal muscle genes. Six1 induced cardiomyocyte hypertrophy and skeletal muscle gene expression. Furthermore, genetically reducing Six1 levels rescued the pathology of Ezh2-deficient hearts. Thus, Ezh2-mediated repression of Six1 in differentiating cardiac progenitors is essential for stable postnatal heart gene expression and homeostasis. Our results suggest that epigenetic dysregulation in embryonic progenitor cells predisposes to adult disease and dysregulated stress responses. PMID:22267199

  17. 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.

  18. Repression of the human papillomavirus type 18 enhancer by the cellular transcription factor Oct-1.

    PubMed Central

    Hoppe-Seyler, F; Butz, K; zur Hausen, H

    1991-01-01

    The role of cellular factors involved in the transcriptional regulation of the cancer-associated human papillomavirus type 18 (HPV18) is yet poorly understood. The presence of an Oct-1-binding site within the HPV18 upstream regulatory region led us to investigate the influence of Oct-1 on viral transcription. Cotransfection of Oct-1 expression plasmids together with luciferase reporter constructs containing HPV18 regulatory sequences indicated that Oct-1 can transcriptionally repress the HPV18 upstream regulatory region. In contrast, heterologous control regions were not affected by Oct-1. HPV18 cis elements that can be repressed by Oct-1 mapped to a 135-bp subregion of the viral constitutive enhancer. Analysis of an Oct-1 mutant defective in DNA binding suggested that HPV18 down-modulation does not require direct binding of Oct-1 to DNA. These results make Oct-1 a candidate factor involved in the intracellular surveillance of HPV18 transcription and support the notion of a host cell mechanism that can specifically repress HPV E6-E7 transforming gene expression. Images PMID:1654457

  19. Genetic factors required to maintain repression of a paramutagenic maize pl1 allele.

    PubMed Central

    Hollick, J B; Chandler, V L

    2001-01-01

    A genetic screen identified two novel gene functions required to maintain mitotically and meiotically heritable gene silencing associated with paramutation of the maize purple plant 1 (pl1) locus. Paramutation at pl1 leads to heritable alterations of pl1 gene regulation; the Pl-Rhoades (Pl-Rh) allele, which typically confers strong pigmentation to juvenile and adult plant structures, changes to a lower expression state termed Pl'-mahogany (Pl'). Paramutation spontaneously occurs at low frequencies in Pl-Rh homozygotes but always occurs when Pl-Rh is heterozygous with Pl'. We identified four mutations that caused increased Pl' pigment levels. Allelism tests revealed that three mutations identified two new maize loci, required to maintain repression 1 (rmr1) and rmr2 and that the other mutation represents a new allele of the previously described mediator of paramutation 1 (mop1) locus. RNA levels from Pl' are elevated in rmr mutants and genetic tests demonstrate that Pl' can heritably change back to Pl-Rh in rmr mutant individuals at variable frequencies. Pigment levels controlled by two pl1 alleles that do not participate in paramutation are unaffected in rmr mutants. These results suggest that RMR functions are intimately involved in maintaining the repressed expression state of paramutant Pl' alleles. Despite strong effects on Pl' repression, rmr mutant plants have no gross developmental abnormalities even after several generations of inbreeding, implying that RMR1 and RMR2 functions are not generally required for developmental homeostasis. PMID:11139517

  20. 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.

  1. 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.

  2. Cold shock domain proteins repress transcription from the GM-CSF promoter.

    PubMed Central

    Coles, L S; Diamond, P; Occhiodoro, F; Vadas, M A; Shannon, M F

    1996-01-01

    The human granulocyte-macrophage colony stimulating factor (GM-CSF) gene promoter binds a sequence-specific single-strand DNA binding protein termed NF-GMb. We previously demonstrated that the NF-GMb binding sites were required for repression of tumor necrosis factor-alpha (TNF-alpha) induction of the proximal GM-CSF promoter sequences in fibroblasts. We now describe the isolation of two different cDNA clones that encode cold shock domain (CSD) proteins with NF-GMb binding characteristics. One is identical to the previously reported CSD protein dbpB and the other is a previously unreported variant of the dbpA CSD factor. This is the first report of CSD factors binding to a cytokine gene. Nuclear NF-GMb and expressed CSD proteins have the same binding specificity for the GM-CSF promoter and other CSD binding sites. We present evidence that CSD factors are components of the nuclear NF-GMb complex. We also demonstrate that overexpression of the CSD proteins leads to complete repression of the proximal GM-CSF promoter containing the NF-GMb/CSD binding sites. Surprisingly, we show that CSD overexpression can also directly repress a region of the promoter which apparently lacks NF-GMb/CSD binding sites. NF-GMb/CSD factors may hence be acting by two different mechanisms. We discuss the potential importance of CSD factors in maintaining strict regulation of the GM-CSF gene. PMID:8710501

  3. Foxk1 promotes cell proliferation and represses myogenic differentiation by regulating Foxo4 and Mef2.

    PubMed

    Shi, Xiaozhong; Wallis, Alicia M; Gerard, Robert D; Voelker, Kevin A; Grange, Robert W; DePinho, Ronald A; Garry, Mary G; Garry, Daniel J

    2012-11-15

    In response to severe injury, adult skeletal muscle exhibits a remarkable regenerative capacity due to a resident muscle stem/progenitor cell population. While a number of factors are expressed in the muscle progenitor cell (MPC) population, the molecular networks that govern this cell population remain an area of active investigation. In this study, utilizing knockdown techniques and overexpression of Foxk1 in the myogenic lineage, we observed dysregulation of Foxo and Mef2 downstream targets. Utilizing an array of technologies, we establish that Foxk1 represses the transcriptional activity of Foxo4 and Mef2 and physically interacts with Foxo4 and Mef2, thus promoting MPC proliferation and antagonizing the myogenic lineage differentiation program, respectively. Correspondingly, knockdown of Foxk1 in C2C12 myoblasts results in cell cycle arrest, and Foxk1 overexpression in C2C12CAR myoblasts retards muscle differentiation. Collectively, we have established that Foxk1 promotes MPC proliferation by repressing Foxo4 transcriptional activity and inhibits myogenic differentiation by repressing Mef2 activity. These studies enhance our understanding of the transcriptional networks that regulate the MPC population and muscle regeneration. PMID:22956541

  4. Repression of Igf1 expression by Ezh2 prevents basal cell differentiation in the developing lung.

    PubMed

    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

    2015-04-15

    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

  5. 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.

  6. H3K4 demethylase activities repress proliferative and postmitotic aging

    PubMed Central

    Alvares, Stacy M; Mayberry, Gaea A; Joyner, Ebony Y; Lakowski, Bernard; Ahmed, Shawn

    2014-01-01

    Homeostasis of postmitotic and proliferating cells is maintained by pathways that repress stress. We found that the Caenorhabditis elegans histone 3 lysine 4 (H3K4) demethylases RBR-2 and SPR-5 promoted postmitotic longevity of stress-resistant daf-2 adults, altered pools of methylated H3K4, and promoted silencing of some daf-2 target genes. In addition, RBR-2 and SPR-5 were required for germ cell immortality at a high temperature. Transgenerational proliferative aging was enhanced for spr-5; rbr-2 double mutants, suggesting that these histone demethylases may function sequentially to promote germ cell immortality by targeting distinct H3K4 methyl marks. RBR-2 did not play a comparable role in the maintenance of quiescent germ cells in dauer larvae, implying that it represses stress that occurs as a consequence of germ cell proliferation, rather than stress that accumulates in nondividing cells. We propose that H3K4 demethylase activities promote the maintenance of chromatin states during stressful growth conditions, thereby repressing postmitotic aging of somatic cells as well as proliferative aging of germ cells. PMID:24134677

  7. IL-7 signalling represses Bcl-6 and the TFH gene program.

    PubMed

    McDonald, Paul W; Read, Kaitlin A; Baker, Chandra E; Anderson, Ashlyn E; Powell, Michael D; Ballesteros-Tato, André; Oestreich, Kenneth J

    2016-01-01

    The transcriptional repressor Bcl-6 is linked to the development of both CD4(+) T follicular helper (TFH) and central memory T (TCM) cells. Here, we demonstrate that in response to decreased IL-2 signalling, T helper 1 (TH1) cells upregulate Bcl-6 and co-initiate TFH- and TCM-like gene programs, including expression of the cytokine receptors IL-6Rα and IL-7R. Exposure of this potentially bi-potent cell population to IL-6 favours the TFH gene program, whereas IL-7 signalling represses TFH-associated genes including Bcl6 and Cxcr5, but not the TCM-related genes Klf2 and Sell. Mechanistically, IL-7-dependent activation of STAT5 contributes to Bcl-6 repression. Importantly, antigen-specific IL-6Rα(+)IL-7R(+) CD4(+) T cells emerge from the effector population at late time points post influenza infection. These data support a novel role for IL-7 in the repression of the TFH gene program and evoke a divergent regulatory mechanism by which post-effector TH1 cells may contribute to long-term cell-mediated and humoral immunity. PMID:26743592

  8. 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.

  9. 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

  10. Flavonoid accumulation in Arabidopsis repressed in lignin synthesis affects auxin transport and plant growth.

    PubMed

    Besseau, Sébastien; Hoffmann, Laurent; Geoffroy, Pierrette; Lapierre, Catherine; Pollet, Brigitte; Legrand, Michel

    2007-01-01

    In Arabidopsis thaliana, silencing of hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyl transferase (HCT), a lignin biosynthetic gene, results in a strong reduction of plant growth. We show that, in HCT-silenced plants, lignin synthesis repression leads to the redirection of the metabolic flux into flavonoids through chalcone synthase activity. Several flavonol glycosides and acylated anthocyanin were shown to accumulate in higher amounts in silenced plants. By contrast, sinapoylmalate levels were barely affected, suggesting that the synthesis of that phenylpropanoid compound might be HCT-independent. The growth phenotype of HCT-silenced plants was shown to be controlled by light and to depend on chalcone synthase expression. Histochemical analysis of silenced stem tissues demonstrated altered tracheary elements. The level of plant growth reduction of HCT-deficient plants was correlated with the inhibition of auxin transport. Suppression of flavonoid accumulation by chalcone synthase repression in HCT-deficient plants restored normal auxin transport and wild-type plant growth. By contrast, the lignin structure of the plants simultaneously repressed for HCT and chalcone synthase remained as severely altered as in HCT-silenced plants, with a large predominance of nonmethoxylated H units. These data demonstrate that the reduced size phenotype of HCT-silenced plants is not due to the alteration of lignin synthesis but to flavonoid accumulation. PMID:17237352

  11. 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

  12. 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

  13. Political repression and children in South Africa: the social construction of damaging effects.

    PubMed

    Swartz, L; Levett, A

    1989-01-01

    This article discusses some dilemmas facing mental health and social service workers studying and providing services for children affected by political repression in South Africa. We argue that it is almost inevitable that progressive care providers are affected by an image of childhood as one of passive innocence and vulnerability, an image which is both outmoded in terms of modern developmental psychology and potentially destructive if the aim of intervention is empowerment. Practical experience with children affected by repression has led us to question commonly held views on the nature of psychological damage, and to recognise that our views on stress tend to be class-bound. Questions of partiality and credibility affect both practical work and the way that social service workers conceive of their role. Without an approach to the understanding of repression which takes account of underlying ideological factors, the social construction of illness and symptoms, and the historical antecedents of current abuses of children in South Africa, we are unable adequately to situate and evaluate critically the work we are doing. Even the focus on children as particular victims of apartheid needs to be thoroughly examined. PMID:2652325

  14. 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

  15. 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

  16. 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

  17. Estrogen receptor α can selectively repress dioxin receptor-mediated gene expression by targeting DNA methylation.

    PubMed

    Marques, Maud; Laflamme, Liette; Gaudreau, Luc

    2013-09-01

    Selective inhibitory crosstalk has been known to occur within the signaling pathways of the dioxin (AhR) and estrogen (ERα) receptors. More specifically, ERα represses a cytochrome P450-encoding gene (CYP1A1) that converts cellular estradiol into a metabolite that inhibits the cell cycle, while it has no effect on a P450-encoding gene (CYP1B1) that converts estrodiol into a genotoxic product. Here we show that ERα represses CYP1A1 by targeting the Dnmt3B DNA methyltransferase and concomitant DNA methylation of the promoter. We also find that histone H2A.Z can positively contribute to CYP1A1 gene expression, and its presence at that gene is inversely correlated with DNA methylation. Taken together, our results provide a framework for how ERα can repress transcription, and how that impinges on the production of an enzyme that generates genotoxic estradiol metabolites, and potential breast cancer progression. Finally, our results reveal a new mechanism for how H2A.Z can positively influence gene expression, which is by potentially competing with DNA methylation events in breast cancer cells. PMID:23828038

  18. Estrogen receptor α can selectively repress dioxin receptor-mediated gene expression by targeting DNA methylation

    PubMed Central

    Marques, Maud; Laflamme, Liette; Gaudreau, Luc

    2013-01-01

    Selective inhibitory crosstalk has been known to occur within the signaling pathways of the dioxin (AhR) and estrogen (ERα) receptors. More specifically, ERα represses a cytochrome P450-encoding gene (CYP1A1) that converts cellular estradiol into a metabolite that inhibits the cell cycle, while it has no effect on a P450-encoding gene (CYP1B1) that converts estrodiol into a genotoxic product. Here we show that ERα represses CYP1A1 by targeting the Dnmt3B DNA methyltransferase and concomitant DNA methylation of the promoter. We also find that histone H2A.Z can positively contribute to CYP1A1 gene expression, and its presence at that gene is inversely correlated with DNA methylation. Taken together, our results provide a framework for how ERα can repress transcription, and how that impinges on the production of an enzyme that generates genotoxic estradiol metabolites, and potential breast cancer progression. Finally, our results reveal a new mechanism for how H2A.Z can positively influence gene expression, which is by potentially competing with DNA methylation events in breast cancer cells. PMID:23828038

  19. Detection of messenger RNA from the isoleucine--valine operons of Salmonella typhimurium by heterologous DNA-RNA hybridization: involvement of transfer RNA in transcriptional repression.

    PubMed

    Childs, G; Sonnenberg, F; Freundlich, M

    1977-03-01

    A hybridization assay using Escherichia coli K-12 DNA isolated from the specialized transducing bacteriophage gammaCI857St68h80 dilv was used to examine the rate of synthesis of the messenger RNA's (mRNA) derived from the isoleucine-valine (ilv) gene cluster of Salmonella typhimurium. In all cases examined, changes in ilv enzyme levels could be correlated with changes in the rate of synthesis of ilv mRNA. Several well characterized regulatory mutants of S. typhimurium had rates of synthesis of ilv mRNA 3 to 8-fold higher than the repressed wild-type strain. The increased rates of ilv mRNA synthesis found in a hisT strain as well as in isoleucyl-and leucyl-tRNA SYNTHETASE MUTANTS, STRONGLY SUGGESTS A ROLE FOR BRANCHED-CHAIN AMINOACYL-TRNA's in transcriptional control. PMID:327261

  20. Cdx2 represses Oct4 function via inducing its proteasome-dependent degradation in early porcine embryos.

    PubMed

    Bou, Gerelchimeg; Liu, Shichao; Guo, Jia; Zhao, Yueming; Sun, Mingju; Xue, Binghua; Wang, Jiaqiang; Wei, Yanchang; Kong, Qingran; Liu, Zhonghua

    2016-02-01

    Reciprocal repression of inner cell mass specific factor OCT4 and trophectoderm specific factor CDX2 promotes mouse first lineage segregation. Studies in mouse embryonic stem (ES) cells revealed that they bind to each other's regulatory regions to reciprocally suppress transcription, additionally they form protein complex for mutual antagonism. However, so far the molecular interaction of Oct4 and Cdx2 in other mammal's early embryo is not yet investigated. Here, over-expression of Cdx2 in early porcine embryo showed CDX2 represses Oct4 through neither the transcriptional repression nor forming repressive complex, but promoting OCT4 nuclear export and proteasomal degradation. The results showed novel molecular regulation of CDX2 on Oct4, and provided important clues for clarifying the mechanism of interaction between CDX2 and Oct4 in embryo of mammals other than mouse. PMID:26708097

  1. 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.

  2. An exploratory study of the interaction of cognitive complexity, dogmatism, and repression-sensitization among college students

    ERIC Educational Resources Information Center

    Starbird, Dannel H.; Biller, Henry B.

    1976-01-01

    A total of 219 male and female college students returned questionnaire measures relating to cognitive complexity, dogmatism, and repression-sensitization. Analyses revealed very complex interactions among the variables. (Author/SB)

  3. TATA-less promoters of some Ets-family genes are efficiently repressed by wild-type p53.

    PubMed

    Iotsova, V; Crépieux, P; Montpellier, C; Laudet, V; Stehelin, D

    1996-12-01

    p53 has been reported to repress a number of TATA-containing promoters in transient transfection assays. TATA-less promoters are generally believed to be refractive to p53 repression. We report here that the TATA-less promoters of Ets-family genes (Ets-1 and Ets-2) are efficiently repressed by wild-type but not mutant p53 in transient co-transfection assays. Moreover, p53 was immunologically detected in protein complexes formed on oligonucleotides from both the TATA-containing and TATA-less promoters. Our data suggest that p53 is involved in the regulation of the expression of both promoter types, most probably by protein-protein interaction. A model for p53 function in promoter repression is proposed. PMID:8957074

  4. 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

  5. Brg1 Is Required for Cdx2-Mediated Repression of Oct4 Expression in Mouse Blastocysts

    PubMed Central

    Wang, Kai; Sengupta, Satyaki; Magnani, Luca; Wilson, Catherine A.; Henry, R. William; Knott, Jason G.

    2010-01-01

    During blastocyst formation the segregation of the inner cell mass (ICM) and trophectoderm is governed by the mutually antagonistic effects of the transcription factors Oct4 and Cdx2. Evidence indicates that suppression of Oct4 expression in the trophectoderm is mediated by Cdx2. Nonetheless, the underlying epigenetic modifiers required for Cdx2-dependent repression of Oct4 are largely unknown. Here we show that the chromatin remodeling protein Brg1 is required for Cdx2-mediated repression of Oct4 expression in mouse blastocysts. By employing a combination of RNA interference (RNAi) and gene expression analysis we found that both Brg1 Knockdown (KD) and Cdx2 KD blastocysts exhibit widespread expression of Oct4 in the trophectoderm. Interestingly, in Brg1 KD blastocysts and Cdx2 KD blastocysts, the expression of Cdx2 and Brg1 is unchanged, respectively. To address whether Brg1 cooperates with Cdx2 to repress Oct4 transcription in the developing trophectoderm, we utilized preimplantation embryos, trophoblast stem (TS) cells and Cdx2-inducible embryonic stem (ES) cells as model systems. We found that: (1) combined knockdown (KD) of Brg1 and Cdx2 levels in blastocysts resulted in increased levels of Oct4 transcripts compared to KD of Brg1 or Cdx2 alone, (2) endogenous Brg1 co-immunoprecipitated with Cdx2 in TS cell extracts, (3) in blastocysts Brg1 and Cdx2 co-localize in trophectoderm nuclei and (4) in Cdx2-induced ES cells Brg1 and Cdx2 are recruited to the Oct4 promoter. Lastly, to determine how Brg1 may induce epigenetic silencing of the Oct4 gene, we evaluated CpG methylation at the Oct4 promoter in the trophectoderm of Brg1 KD blastocysts. This analysis revealed that Brg1-dependent repression of Oct4 expression is independent of DNA methylation at the blastocyst stage. In toto, these results demonstrate that Brg1 cooperates with Cdx2 to repress Oct4 expression in the developing trophectoderm to ensure normal development. PMID:20485553

  6. 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

  7. 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

  8. Antileishmanial Activity of Semisynthetic Lupane Triterpenoids Betulin and Betulinic Acid Derivatives: Synergistic Effects with Miltefosine

    PubMed Central

    Sousa, Maria C.; Varandas, Raquel; Santos, Rita C.; Santos-Rosa, Manuel; Alves, Vera; Salvador, Jorge A. R.

    2014-01-01

    Leishmaniasis is a neglected tropical disease (NTDs), endemic in 88 countries, affecting more than 12 million people. The treatment consists in pentavalent antimony compounds, amphotericin B, pentamidine and miltefosine, among others. However, these current drugs are limited due to their toxicity, development of biological resistance, length of treatment and high cost. Thus, it is important to continue the search for new effective and less toxic treatments. The anti-Leishmania activity of sixteen semisynthetic lupane triterpenoids derivatives of betulin (BT01 to BT09) and betulinic acid (AB10 to AB16) were evaluated. Drug interactions between the active compounds and one current antileishmanial drug, miltefosine, were assessed using the fixed ratio isobologram method. In addition, effects on the cell cycle, apoptosis/necrosis events, morphology and DNA integrity were studied. The derivatives BT06 (3β-Hydroxy-(20R)-lupan-29-oxo-28-yl-1H-imidazole-1-carboxylate) and AB13 (28-(1H-imidazole-1-yl)-3,28-dioxo-lup-1,20(29)-dien-2-yl-1H-imidazole-1-carboxylate) were found to be the most active, with IC50 values of 50.8 µM and 25.8 µM, respectively. Interactions between these two compounds and miltefosine were classified as synergistic, with the most effective association being between AB13 and miltefosine, where decreases of IC50 values to 6 µM were observed, similar to the miltefosine activity alone. AB13 induced significant morphological changes, while both derivatives produced anti-proliferative activity through cell cycle arrest at the G0/G1 phase. Neither of these derivatives induced significant apoptosis/necrosis, as indicated by phosphatidylserine externalization and DNA fragmentation assays. In addition, neither of the derivatives induced death in macrophage cell lines. Thus, they do not present any potential risk of toxicity for the host cells. This study has identified the betulin derivative BT06 and the betulinic acid derivative AB13 as promising molecules

  9. Hormone-induced repression of genes requires BRG1-mediated H1.2 deposition at target promoters.

    PubMed

    Nacht, Ana Silvina; Pohl, Andy; Zaurin, Roser; Soronellas, Daniel; Quilez, Javier; Sharma, Priyanka; Wright, Roni H; Beato, Miguel; Vicent, Guillermo P

    2016-08-15

    Eukaryotic gene regulation is associated with changes in chromatin compaction that modulate access to DNA regulatory sequences relevant for transcriptional activation or repression. Although much is known about the mechanism of chromatin remodeling in hormonal gene activation, how repression is accomplished is much less understood. Here we report that in breast cancer cells, ligand-activated progesterone receptor (PR) is directly recruited to transcriptionally repressed genes involved in cell proliferation along with the kinases ERK1/2 and MSK1. PR recruits BRG1 associated with the HP1γ-LSD1 complex repressor complex, which is further anchored via binding of HP1γ to the H3K9me3 signal deposited by SUV39H2. In contrast to what is observed during gene activation, only BRG1 and not the BAF complex is recruited to repressed promoters, likely due to local enrichment of the pioneer factor FOXA1. BRG1 participates in gene repression by interacting with H1.2, facilitating its deposition and stabilizing nucleosome positioning around the transcription start site. Our results uncover a mechanism of hormone-dependent transcriptional repression and a novel role for BRG1 in progestin regulation of breast cancer cell growth. PMID:27390128

  10. Onset of carbon catabolite repression in Aspergillus nidulans. Parallel involvement of hexokinase and glucokinase in sugar signaling.

    PubMed

    Flipphi, Michel; van de Vondervoort, Peter J I; Ruijter, George J G; Visser, Jaap; Arst, Herbert N; Felenbok, Béatrice

    2003-04-01

    The role of hexose phosphorylating enzymes in the signaling of carbon catabolite repression was investigated in the filamentous fungus Aspergillus nidulans. A d-fructose non-utilizing, hexokinase-deficient (hxkA1, formerly designated frA1) strain was utilized to obtain new mutants lacking either glucokinase (glkA4) or both hexose kinases (hxkA1/glkA4). d-Glucose and d-fructose phosphorylation is completely abolished in the double mutant, which consequently cannot grow on either sugar. The glucokinase single mutant exhibits no nutritional deficiencies. Three repressible diagnostic systems, ethanol utilization (alcA and alcR genes), xylan degradation (xlnA), and acetate catabolism (facA), were analyzed in these hexose kinase mutants at the transcript level. Transcriptional repression by d-glucose is fully retained in the two single kinase mutants, whereas the hexokinase mutant is partially derepressed for d-fructose. Thus, hexokinase A and glucokinase A compensate each other for carbon catabolite repression by d-glucose in the single mutants. In contrast, both d-glucose and d-fructose repression are severely impaired for all three diagnostic systems in the double mutant. Unlike the situation in Saccharomyces cerevisiae, the hexose phosphorylating enzymes play parallel roles in glucose repression in A. nidulans. PMID:12519784

  11. 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

  12. Multiple determinants of splicing repression activity in the polypyrimidine tract binding proteins, PTBP1 and PTBP2.

    PubMed

    Keppetipola, Niroshika M; Yeom, Kyu-Hyeon; Hernandez, Adrian L; Bui, Tessa; Sharma, Shalini; Black, Douglas L

    2016-08-01

    Most human genes generate multiple protein isoforms through alternative pre-mRNA splicing, but the mechanisms controlling alternative splicing choices by RNA binding proteins are not well understood. These proteins can have multiple paralogs expressed in different cell types and exhibiting different splicing activities on target exons. We examined the paralogous polypyrimidine tract binding proteins PTBP1 and PTBP2 to understand how PTBP1 can exhibit greater splicing repression activity on certain exons. Using both an in vivo coexpression assay and an in vitro splicing assay, we show that PTBP1 is more repressive than PTBP2 per unit protein on a target exon. Constructing chimeras of PTBP1 and 2 to determine amino acid features that contribute to their differential activity, we find that multiple segments of PTBP1 increase the repressive activity of PTBP2. Notably, when either RRM1 of PTBP2 or the linker peptide separating RRM2 and RRM3 are replaced with the equivalent PTBP1 sequences, the resulting chimeras are highly active for splicing repression. These segments are distinct from the known region of interaction for the PTBP1 cofactors Raver1 and Matrin3 in RRM2. We find that RRM2 of PTBP1 also increases the repression activity of an otherwise PTBP2 sequence, and that this is potentially explained by stronger binding by Raver1. These results indicate that multiple features over the length of the two proteins affect their ability to repress an exon. PMID:27288314

  13. 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. PMID:27226589

  14. 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

  15. 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.

  16. 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

  17. Very low amounts of glucose cause repression of the stress-responsive gene HSP12 in Saccharomyces cerevisiae.

    PubMed

    de Groot, E; Bebelman, J P; Mager, W H; Planta, R J

    2000-02-01

    Changing the growth mode of Saccharomyces cerevisiae by adding fermentable amounts of glucose to cells growing on a non-fermentable carbon source leads to rapid repression of general stress-responsive genes like HSP12. Remarkably, glucose repression of HSP12 appeared to occur even at very low glucose concentrations, down to 0.005%. Although these low levels of glucose do not induce fermentative growth, they do act as a growth signal, since upon addition of glucose to a concentration of 0.02%, growth rate increased and ribosomal protein gene transcription was up-regulated. In an attempt to elucidate how this type of glucose signalling may operate, several signalling mutants were examined. Consistent with the low amounts of glucose that elicit HSP12 repression, neither the main glucose-repression pathway nor cAMP-dependent activation of protein kinase A appeared to play a role in this regulation. Using mutants involved in glucose metabolism, evidence was obtained suggesting that glucose 6-phosphate serves as a signalling molecule. To identify the target for glucose repression on the promoter of the HSP12 gene, a promoter deletion series was used. The major transcription factors governing (stress-induced) transcriptional activation of HSP12 are Msn2p and Msn4p, binding to the general stress-responsive promoter elements (STREs). Surprisingly, glucose repression of HSP12 appeared to be independent of Msn2/4p: HSP12 transcription in glycerol-grown cells was unaffected in a deltamsn2deltamsn4 strain. Nevertheless, evidence was obtained that STRE-mediated transcription is the target of repression by low amounts of glucose. These data suggest that an as yet unidentified factor is involved in STRE-mediated transcriptional regulation of HSP12. PMID:10708375

  18. 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

  19. 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.

  20. 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

  1. 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

  2. A Novel POK Family Transcription Factor, ZBTB5, Represses Transcription of p21CIP1 Gene*

    PubMed Central

    Koh, Dong-In; Choi, Won-Il; Jeon, Bu-Nam; Lee, Choong-Eun; Yun, Chae-Ok; Hur, Man-Wook

    2009-01-01

    Transcriptional repression through chromatin remodeling and histone deacetylation has been postulated as a driving force for tumorigenesis. We isolated and characterized a novel POZ domain Krüppel-like zinc finger transcription repressor, ZBTB5 (zinc finger and BTB domain-containing 5). Serial analysis of gene expression (SAGE) analysis showed that ZBTB5 expression is higher in retinoblastoma and muscle cancer tissues. Immunocytochemistry showed that ZBTB5 was localized to the nucleus, particularly nuclear speckles. ZBTB5 directly repressed transcription of cell cycle arrest gene p21 by binding to the proximal GC-box 5/6 elements and the two distal p53-responsive elements (bp −2323 ∼ −2299; bp −1416 ∼ −1392). Chromatin immunoprecipitation assays showed that ZBTB5 and p53 competed with each other in occupying the p53 binding elements. ZBTB5 interacted with co-repressor-histone deacetylase complexes such as BCoR (BCL-6-interacting corepressor), NCoR (nuclear receptor corepressor), and SMRT (silencing mediator for retinoid and thyroid receptors) via its POZ domain. These interactions resulted in deacetylation of histones Ac-H3 and Ac-H4 at the proximal promoter, which is important in the transcriptional repression of p21. MTT (3-(4,5-di meth yl thi azol-2-yl)-2,5-diphenyltetrazolium bromide) assays and fluorescent-activated cell sorter analysis revealed that ZBTB5 stimulated both cell proliferation and cell cycle progression, significantly increasing the number of cells in S-phase. Overall, our data suggest that ZBTB5 is a potent transcription repressor of cell cycle arrest gene p21 and a potential proto-oncogene stimulating cell proliferation. PMID:19491398

  3. 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

  4. Influence of Repressive Coping Style on Cortical Activation during Encoding of Angry Faces

    PubMed Central

    Rauch, Astrid Veronika; ter Horst, Lena; Paul, Victoria Gabriele; Bauer, Jochen; Dannlowski, Udo; Konrad, Carsten; Ohrmann, Patricia; Kugel, Harald; Egloff, Boris; Arolt, Volker; Suslow, Thomas

    2014-01-01

    Background Coping plays an important role for emotion regulation in threatening situations. The model of coping modes designates repression and sensitization as two independent coping styles. Repression consists of strategies that shield the individual from arousal. Sensitization indicates increased analysis of the environment in order to reduce uncertainty. According to the discontinuity hypothesis, repressors are sensitive to threat in the early stages of information processing. While repressors do not exhibit memory disturbances early on, they manifest weak memory for these stimuli later. This study investigates the discontinuity hypothesis using functional magnetic resonance imaging (fMRI). Methods Healthy volunteers (20 repressors and 20 sensitizers) were selected from a sample of 150 students on the basis of the Mainz Coping Inventory. During the fMRI experiment, subjects evaluated and memorized emotional and neutral faces. Subjects performed two sessions of face recognition: immediately after the fMRI session and three days later. Results Repressors exhibited greater activation of frontal, parietal and temporal areas during encoding of angry faces compared to sensitizers. There were no differences in recognition of facial emotions between groups neither immediately after exposure nor after three days. Conclusions The fMRI findings suggest that repressors manifest an enhanced neural processing of directly threatening facial expression which confirms the assumption of hyper-responsivity to threatening information in repression in an early processing stage. A discrepancy was observed between high neural activation in encoding-relevant brain areas in response to angry faces in repressors and no advantage in subsequent memory for these faces compared to sensitizers. PMID:25502775

  5. 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.

  6. TNF-Alpha Represses Transcription of Human Bone Morphogenetic Protein-4 in Lung Epithelial Cells

    PubMed Central

    Zhu, Nian-Ling; Li, Changgong; Huang, Hao Hao; Sebald, Matthew; Londhe, Vedang A.; Heisterkamp, Nora; Warburton, David; Bellusci, Saverio; Minoo, Parviz

    2007-01-01

    Bone Morphogenetic Proteins are key signaling molecules in vertebrate development. Little is known about Bmp gene regulation in any organ. In Drosophila, the Bmp gene, dpp is regulated by Dorsal, the invertebrate homologue of Rel-NFkB. In this study we examined whether TNF-alpha, which activates NF-kB, can regulate Bmp4 gene expression. TNF-alpha reduced Bmp4 mRNA in lung adenocarcinoma A549 cells and repressed transcriptional activity of the human Bmp4 promoter in a dose-dependent manner. Similar repression was observed when the Bmp4 promoter was co-transfected with a p65 (RelA) expression vector in the absence of TNF-alpha treatment, suggesting that RelA mediates the effect of TNF-alpha. In support of this finding, the repressor effect of TNF-alpha on Bmp4 was abrogated by a co-transfected dominant negative mutant of IkB (S32A/S36A). The human Bmp4 promoter contains 3 putative consensus binding sites for NF-kB. Surprisingly, only one of the latter binding sites was capable of binding NFkB. Repressor effect of NFkB was not dependent on any of the three binding sites, but localized to a 122 bp fragment which bound both RelA and SP1. SP1stimulated transcription, whereas increasing doses of RelA opposed this effect. In vivo, TNF-alpha inhibited branching morphogenesis and LacZ gene expression in Bmp4-lacz transgenic lungs. These data support a model in which TNF-alpha-induced RelA interacts with SP1 to bring about transcriptional repression of Bmp4 gene. These findings provide a mechanistic paradigm for interactions between mediators of inflammation and morphogenesis with relevant implications for normal lung development and pathogenesis of disease. PMID:17350185

  7. 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

  8. 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

  9. Dexamethasone Induces Cardiomyocyte Terminal Differentiation via Epigenetic Repression of Cyclin D2 Gene.

    PubMed

    Gay, Maresha S; Dasgupta, Chiranjib; Li, Yong; Kanna, Angela; Zhang, Lubo

    2016-08-01

    Dexamethasone treatment of newborn rats inhibited cardiomyocyte proliferation and stimulated premature terminal differentiation of cardiomyocytes in the developing heart. Yet mechanisms remain undetermined. The present study tested the hypothesis that the direct effect of glucocorticoid receptor-mediated epigenetic repression of cyclin D2 gene in the cardiomyocyte plays a key role in the dexamethasone-mediated effects in the developing heart. Cardiomyocytes were isolated from 2-day-old rats. Cells were stained with a cardiomyocyte marker α-actinin and a proliferation marker Ki67. Cyclin D2 expression was evaluated by Western blot and quantitative real-time polymerase chain reaction. Promoter methylation of CcnD2 was determined by methylated DNA immunoprecipitation (MeDIP). Overexpression of Cyclin D2 was conducted by transfection of FlexiCcnD2 (+CcnD2) construct. Treatment of cardiomyocytes isolated from newborn rats with dexamethasone for 48 hours significantly inhibited cardiomyocyte proliferation with increased binucleation and decreased cyclin D2 protein abundance. These effects were blocked with Ru486 (mifepristone). In addition, the dexamethasone treatment significantly increased cyclin D2 gene promoter methylation in newborn rat cardiomyocytes. 5-Aza-2'-deoxycytidine inhibited dexamethasone-mediated promoter methylation, recovered dexamethasone-induced cyclin D2 gene repression, and blocked the dexamethasone-elicited effects on cardiomyocyte proliferation and binucleation. In addition, the overexpression of cyclin D2 restored the dexamethasone-mediated inhibition of proliferation and increase in binucleation in newborn rat cardiomyocytes. The results demonstrate that dexamethasone acting on glucocorticoid receptors has a direct effect and inhibits proliferation and stimulates premature terminal differentiation of cardiomyocytes in the developing heart via epigenetic repression of cyclin D2 gene. PMID:27302109

  10. 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

  11. Transcription of the pcbAB, pcbC and penDE genes of Penicillium chrysogenum AS-P-78 is repressed by glucose and the repression is not reversed by alkaline pHs.

    PubMed

    Gutiérrez, S; Marcos, A T; Casqueiro, J; Kosalková, K; Fernández, F J; Velasco, J; Martín, J F

    1999-02-01

    Glucose repressed transcription of the penicillin biosynthesis genes pcbAB, pcbC and penDE when added at inoculation time to cultures of Penicillium chrysogenum AS-P-78 but it had little repressive effect when added at 12 h and no effect when added at 24 or 36 h. A slight increase in the expression of pcbC and penDE (and to a smaller extent of pcbAB) was observed in glucose-grown cultures at pH 6.8, 7.4 and 8.0 as compared with pH 6.2, but alkaline pHs did not override the strong repression exerted by glucose. Transcription of the actin gene used as control was not significantly affected by glucose or alkaline pHs. Repression by glucose of the three penicillin biosynthetic genes was also observed using the lacZ reporter gene coupled to each of the three promoters in monocopy transformants with the constructions integrated at the pyrG locus. Glucose repression of the three genes encoding enzymes of penicillin biosynthesis therefore appears to be exerted by a regulatory mechanism independent from pH regulation. PMID:10075414

  12. 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

  13. Individual differences in self-reported thought control: the role of the repressive coping sytle.

    PubMed

    Luciano, Juan Vicente; Algarabel, Salvador

    2006-05-01

    The purpose of the present research is to assess differences between repressors and non repressors in some aspects associated with conscious thought control. Thus, Sixty-three Spanish university students with different combinations of trait anxiety and defensiveness completed the Thought Control Ability Questionnaire (TCAQ) and the White Bear Suppression Inventory (WBSI). Data analysis showed that subjects with low anxiety (repressors and low anxious) reported higher perceived ability to control unpleasant thoughts and less tendency to suppress than did subjects with high anxiety (high anxious and defensive high anxious). Implications of these results are discussed in relation to recent researches that have explored the association between repression and thought suppression. PMID:17296036

  14. Functional Association between Eyegone and HP1a Mediates wingless Transcriptional Repression during Development

    PubMed Central

    Salvany, Lara; Requena, David

    2012-01-01

    The eyegone (eyg) gene encodes Eyg, a transcription factor of the Pax family with multiple roles during Drosophila development. Although Eyg has been shown to act as a repressor, nothing is known about the mechanism by which it represses its target genes. Here, we show that Eyg forms a protein complex with heterochromatin protein 1a (HP1a). Both proteins bind to the same chromatin regions on polytene chromosomes and act cooperatively to suppress variegation and mediate gene silencing. In addition, Eyg binds to a wingless (wg) enhancer region, recruiting HP1a to assemble a closed, heterochromatin-like conformation that represses transcription of the wg gene. We describe here the evidence that suggests that Eyg, encoded by eyegone (eyg), represses wingless (wg) during eye development by association with HP1a. We show that Eyg forms a protein complex with HP1a and both proteins colocalize on salivary gland polytene chromosomes. Using position effect variegation (PEV) experiments, we demonstrated that eyg has a dose-dependent effect on heterochromatin gene silencing and identified a genetic interaction with HP1a in this process. We further demonstrated that HP1a binds to the same wg enhancer element as Eyg. DNase I sensitivity assays indicated that this enhancer region has a closed heterochromatin-like conformation, which becomes open in eyg mutants. In these mutants, much less HP1a binds to the wg enhancer region, as shown by ChIP experiments. Furthermore, as previously described for Eyg, a reduction in the amount of HP1a in the eye imaginal disc derepresses wg. Together, our results suggest a model in which Eyg specifically binds to the wg enhancer region, recruiting HP1a to that site. The recruitment of HP1a prevents transcription by favoring a closed, heterochromatin-like structure. Thus, for the first time, we show that HP1a plays a direct role in the repression of a developmentally regulated gene, wg, during Drosophila eye development. PMID:22547675

  15. Repression and inhibition of transport systems for branched-chain amino acids in Salmonella typhimurium.

    PubMed

    Kiritani, K; Ohnishi, K

    1977-02-01

    Kinetics of the transport systems common for entry of L-isoleucine, L-leucine, and L-valine in Salmonella typhimurium LT2 have been analyzed as a function of substrateconcentration in the range of 0.5 to 45 muM. The systems of transport mutants, KA203 (ilvT3) and KA204 (ilvT4), are composed of two components; apparent Km values for uptake of isoleucine, leucine, and valine by the low Km component are 2 muM, 2 to 3 muM, and 1 muM, respectively, and by the high Km component 30 muM, 20 to 40 muM, and 0.1 mM, respectively. The transport system(s) of the wild type has not been separated into components but rather displays single Km values of 9 muM for isoleucine, 10 muM for leucine, and 30 muM for valine. The transport activity of the wild type was repressed by L-leucine, alpha ketoisocaproate, glycyl-L-isoleucine, glycyl-L-leucine, and glycyl-L-methionine. That for the transport mutants was repressed by L-alanine, L-isoleucine, L-methionine, L-valine, alpha-ketoisovalerate, alpha-keto-beta-methylvalerate, glycyl-L-alanine, glycyl-L-threonine, and glycyl-L-valine, in addition to the compounds described above. Repression of the mutant transport systems resulted in disappearance of the low Km component for valine uptake, together with a decrease in Vmax of the high Km component; the kinetic analysis with isoleucine and leucine as substrates was not possible because of poor uptake. The maximum reduction of the transport activity for isoleucine was obtained after growing cells for two to three generations in a medium supplemented with repressor, and for the depression, protein synthesis was essential after removal of the repressor. The transport activity for labeled isoleucine in the transport mutant and wild-type strains was inhibited by unlabeled L-alanine, L-cysteine, L-isoleucine, L-leucine, L-methionine, L-threonine, and L-valine. D-Amino acids neither repressed nor inhibited the transport activity of cells for entry of isoleucine. PMID:320186

  16. The base pairing RNA Spot 42 participates in a multi-output feedforward loop to help enact catabolite repression in Escherichia coli

    PubMed Central

    Beisel, Chase L.; Storz, Gisela

    2011-01-01

    SUMMARY Bacteria selectively consume some carbon sources over others through a regulatory mechanism termed catabolite repression. Here, we show that the base pairing RNA Spot 42 plays a broad role in catabolite repression in Escherichia coli by directly repressing genes involved in central and secondary metabolism, redox balancing, and the consumption of diverse non-preferred carbon sources. Many of the genes repressed by Spot 42 are transcriptionally activated by the global regulator CRP. Since CRP represses Spot 42, these regulators participate in a specific regulatory circuit called a multi-output feedforward loop. We found that this loop can reduce leaky expression of target genes in the presence of glucose and can maintain repression of target genes under changing nutrient conditions. Our results suggest that base pairing RNAs in feedforward loops can help shape the steady-state levels and dynamics of gene expression. PMID:21292161

  17. Activated Nrf2 Interacts with Kaposi's Sarcoma-Associated Herpesvirus Latency Protein LANA-1 and Host Protein KAP1 To Mediate Global Lytic Gene Repression

    PubMed Central

    Gjyshi, Olsi; Roy, Arunava; Dutta, Sujoy; Veettil, Mohanan Valiya; Dutta, Dipanjan

    2015-01-01

    ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) is etiologically associated with Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman's disease. We have previously shown that KSHV utilizes the host transcription factor Nrf2 to aid in infection of endothelial cells and oncogenesis. Here, we investigate the role of Nrf2 in PEL and PEL-derived cell lines and show that KSHV latency induces Nrf2 protein levels and transcriptional activity through the COX-2/PGE2/EP4/PKCζ axis. Next-generation sequencing of KSHV transcripts in the PEL-derived BCBL-1 cell line revealed that knockdown of this activated Nrf2 results in global elevation of lytic genes. Nrf2 inhibition by the chemical brusatol also induces lytic gene expression. Both Nrf2 knockdown and brusatol-mediated inhibition induced KSHV lytic reactivation in BCBL-1 cells. In a series of follow-up experiments, we characterized the mechanism of Nrf2-mediated regulation of KSHV lytic repression during latency. Biochemical assays showed that Nrf2 interacted with KSHV latency-associated nuclear antigen 1 (LANA-1) and the host transcriptional repressor KAP1, which together have been shown to repress lytic gene expression. Promoter studies showed that although Nrf2 alone induces the open reading frame 50 (ORF50) promoter, its association with LANA-1 and KAP1 abrogates this effect. Interestingly, LANA-1 is crucial for efficient KAP1/Nrf2 association, while Nrf2 is essential for LANA-1 and KAP1 recruitment to the ORF50 promoter and its repression. Overall, these results suggest that activated Nrf2, LANA-1, and KAP1 assemble on the ORF50 promoter in a temporal fashion. Initially, Nrf2 binds to and activates the ORF50 promoter during early de novo infection, an effect that is exploited during latency by LANA-1-mediated recruitment of the host transcriptional repressor KAP1 on Nrf2. Cell death assays further showed that Nrf2 and KAP1 knockdown induce significant cell death in PEL cell lines

  18. PABP and the poly(A) tail augment microRNA repression by facilitated miRISC binding.

    PubMed

    Moretti, Francesca; Kaiser, Constanze; Zdanowicz-Specht, Agnieszka; Hentze, Matthias W

    2012-06-01

    Polyadenylated mRNAs are typically more strongly repressed by microRNAs (miRNAs) than their nonadenylated counterparts. Using a Drosophila melanogaster cell-free translation system, we found that this effect is mediated by the poly(A)-binding protein (PABP). miRNA repression was positively correlated with poly(A) tail length, but this stimulatory effect on repression was lost when translation was repressed by the tethered GW182 silencing domain rather than the miRNA-induced silencing complex (miRISC) itself. These findings are mechanistically explained by a notable function of PABP: it promotes association of miRISC with miRNA-regulated mRNAs. We also found that PABP association with mRNA rapidly diminished with miRISC recruitment and before detectable deadenylation. We integrated these data into a revised model for the function of PABP and the poly(A) tail in miRNA-mediated translational repression. PMID:22635249

  19. NuRD mediates activating and repressive functions of GATA-1 and FOG-1 during blood development

    PubMed Central

    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

    2010-01-01

    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. PMID:19927129

  20. 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

  1. 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. PMID:23775117

  2. 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

  3. 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

  4. HISTONE DEACETYLASE 9 represses seedling traits in Arabidopsis thaliana dry seeds.

    PubMed

    van Zanten, Martijn; Zöll, Christian; Wang, Zhi; Philipp, Christina; Carles, Annaick; Li, Yong; Kornet, Noortje G; Liu, Yongxiu; Soppe, Wim J J

    2014-11-01

    Plant life is characterized by major phase changes. We studied the role of histone deacetylase (HDAC) activity in the transition from seed to seedling in Arabidopsis. Pharmacological inhibition of HDAC stimulated germination of freshly harvested seeds. Subsequent analysis revealed that histone deacetylase 9 (hda9) mutant alleles displayed reduced seed dormancy and faster germination than wild-type plants. Transcriptome meta-analysis comparisons between the hda9 dry seed transcriptome and published datasets demonstrated that transcripts of genes that are induced during imbibition in wild-type prematurely accumulated in hda9-1 dry seeds. This included several genes associated with photosynthesis and photoautotrophic growth such as RuBisCO and RuBisCO activase (RCA). Chromatin immunoprecipitation experiments demonstrated enhanced histone acetylation levels at their loci in young hda9-1 seedlings. Our observations suggest that HDA9 negatively influences germination and is involved in the suppression of seedling traits in dry seeds, probably by transcriptional repression via histone deacetylation. Accordingly, HDA9 transcript is abundant in dry seeds and becomes reduced during imbibition in wild-type seeds. The proposed function of HDA9 is opposite to that of its homologous genes HDA6 and HDA19, which have been reported to repress embryonic properties in germinated seedlings. PMID:25146719

  5. SAYP and Brahma are important for 'repressive' and 'transient' Pol II pausing.

    PubMed

    Vorobyeva, Nadezhda E; Nikolenko, Julia V; Nabirochkina, Elena N; Krasnov, Alexey N; Shidlovskii, Yulii V; Georgieva, Sofia G

    2012-08-01

    Drosophila SAYP, a homologue of human PHF10/BAF45a, is a metazoan coactivator associated with Brahma and essential for its recruitment on the promoter. The role of SAYP in DHR3 activator-driven transcription of the ftz-f1 gene, a member of the ecdysone cascade was studied. In the repressed state of ftz-f1 in the presence of DHR3, the Pol II complex is pre-recruited on the promoter; Pol II starts transcription but is paused 1.5 kb downstream of the promoter, with SAYP and Brahma forming a 'nucleosomal barrier' (a region of high nucleosome density) ahead of paused Pol II. SAYP depletion leads to the removal of Brahma, thereby eliminating the nucleosomal barrier. During active transcription, Pol II pausing at the same point correlates with Pol II CTD Ser2 phosphorylation. SAYP is essential for Ser2 phosphorylation and transcription elongation. Thus, SAYP as part of the Brahma complex participates in both 'repressive' and 'transient' Pol II pausing. PMID:22638575

  6. Chimeric DNA methyltransferases target DNA methylation to specific DNA sequences and repress expression of target genes

    PubMed Central

    Li, Fuyang; Papworth, Monika; Minczuk, Michal; Rohde, Christian; Zhang, Yingying; Ragozin, Sergei; Jeltsch, Albert

    2007-01-01

    Gene silencing by targeted DNA methylation has potential applications in basic research and therapy. To establish targeted methylation in human cell lines, the catalytic domains (CDs) of mouse Dnmt3a and Dnmt3b DNA methyltransferases (MTases) were fused to different DNA binding domains (DBD) of GAL4 and an engineered Cys2His2 zinc finger domain. We demonstrated that (i) Dense DNA methylation can be targeted to specific regions in gene promoters using chimeric DNA MTases. (ii) Site-specific methylation leads to repression of genes controlled by various cellular or viral promoters. (iii) Mutations affecting any of the DBD, MTase or target DNA sequences reduce targeted methylation and gene silencing. (iv) Targeted DNA methylation is effective in repressing Herpes Simplex Virus type 1 (HSV-1) infection in cell culture with the viral titer reduced by at least 18-fold in the presence of an MTase fused to an engineered zinc finger DBD, which binds a single site in the promoter of HSV-1 gene IE175k. In short, we show here that it is possible to direct DNA MTase activity to predetermined sites in DNA, achieve targeted gene silencing in mammalian cell lines and interfere with HSV-1 propagation. PMID:17151075

  7. Transcript analysis of nrrF, a Fur repressed sRNA of Neisseria gonorrhoeae

    PubMed Central

    Ducey, Thomas F.; Jackson, Lydgia; Orvis, Joshua; Dyer, David W.

    2016-01-01

    Like most microorganisms, Neisseria gonorrhoeae alters gene expression in response to iron availability. The ferric uptake regulator Fur has been shown to be involved in controlling this response, but the extent of this involvement remains unknown. It is known that in addition to working directly to repress gene expression, Fur may also work indirectly by controlling additional regulatory elements. Using in silico analysis, we identified a putative small RNA (sRNA) homolog of the meningococcal nrrF locus, and demonstrate that this sRNA is iron-repressible, suggesting that this is the gonococcal analog of the rhyB locus in Escherichia coli. Quantitative real-time RT-PCR analysis indicates that this transcript may also be temporally regulated. Transcript analysis identified the 5′ start of the transcript, using a single reaction, fluorescent-based, primer extension assay. This protocol allows for the rapid identification of transcriptional start sites of RNA transcripts, and could be used for high-throughput transcript mapping. PMID:19162160

  8. YB1 binds to and represses the p16 tumor suppressor gene.

    PubMed

    Kotake, Yojiro; Ozawa, Yuichi; Harada, Masanori; Kitagawa, Kyoko; Niida, Hiroyuki; Morita, Yasutaka; Tanaka, Kenji; Suda, Takafumi; Kitagawa, Masatoshi

    2013-11-01

    Y box binding protein 1 (YB1) has multiple functions associated with drug resistance, cell proliferation and metastasis through transcriptional and translational regulation. Increased expression of YB1 is closely related to tumor growth and aggressiveness. We showed that YB1 protein levels were decreased through replicative and premature senescence and were correlated with increased expression levels of p16(INK) (4A) tumor suppressor gene. Depletion of YB1 was associated with increased levels of p16 in human and murine primary cells. Forced expression of YB1 in mouse embryonic fibroblasts resulted in decreased expression of p16 and increased cell proliferation. Senescence-associated expression of β-galactosidase was repressed in YB1-over-expressing cells. Chromatin immunoprecipitation assays showed that YB1 directly associates with the p16 promoter. Taken together, all our findings indicate that YB1 directly binds to and represses p16 transcription, subsequently resulting in the promotion of cell growth and prevention of cellular senescence. PMID:24165022

  9. Smad3 Sensitizes Hepatocelluar Carcinoma Cells to Cisplatin by Repressing Phosphorylation of AKT

    PubMed Central

    Zhou, Hong-Hao; Chen, Lin; Liang, Hui-Fang; Li, Guang-Zhen; Zhang, Bi-Xiang; Chen, Xiao-Ping

    2016-01-01

    Background: Heptocelluar carcinoma (HCC) is insensitive to chemotherapy due to limited bioavailability and acquired drug resistance. Smad3 plays dual roles by inhibiting cell growth initially and promoting the progression of advanced tumors in HCC. However, the role of smad3 in chemosensitivity of HCC remains elusive. Methods: The role of smad3 in chemosensitivity of HCC was measured by cell viability, apoptosis, plate colony formation assays and xenograft tumor models. Non-smad signaling was detected by Western blotting to search for the underlying mechanisms. Results: Smad3 enhanced the chemosensitivity of HCC cells to cisplatin. Smad3 upregulated p21Waf1/Cip1 and downregulated c-myc and bcl2 with the treatment of cisplatin. Moreover, overexpression of smad3 repressed the phosphorylation of AKT, and vice versa. Inhibition of PI3K/AKT pathway by LY294002 restored chemosensitivity of smad3-deficiency cells to cisplatin in HCC. Conclusion: Smad3 sensitizes HCC cells to the effects of cisplatin by repressing phosphorylation of AKT and combination of inhibitor of AKT pathway and conventional chemotherapy may be a potential way to solve drug resistance in HCC. PMID:27110775

  10. Tumor Protein 53-Induced Nuclear Protein 1 Enhances p53 Function and Represses Tumorigenesis.

    PubMed

    Shahbazi, Jeyran; Lock, Richard; Liu, Tao

    2013-01-01

    Tumor protein 53-induced nuclear protein 1 (TP53INP1) is a stress-induced p53-target gene whose expression is modulated by transcription factors such as p53, p73, and E2F1. TP53INP1 gene encodes two isoforms of TP53INP1 proteins, TP53INP1α and TP53INP1β, both of which appear to be key elements in p53 function. In association with homeodomain-interacting protein kinase-2 (HIPK2), TP53INP1 phosphorylates p53 protein at Serine-46. This enhances p53 protein stability and its transcriptional activity, leading to transcriptional activation of p53-target genes such as p21 and PIG3, cell growth arrest and apoptosis upon DNA damage stress. The anti-proliferative and pro-apoptotic activities of TP53INP1 indicate that TP53INP1 has an important role in cellular homeostasis and DNA damage response. Deficiency in TP53INP1 expression results in increased tumorigenesis, whereas TP53INP1 expression is repressed during early stages of cancer by factors such as miR-155. This review aims to summarize the roles of TP53INP1 in blocking tumor progression through p53-dependant and p53-independent pathways, as well as the elements which repress TP53INP1 expression, hence highlighting its potential as a therapeutic target in cancer treatment. PMID:23717325

  11. 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

  12. Activation and repression by oncogenic MYC shape tumour-specific gene expression profiles.

    PubMed

    Walz, Susanne; Lorenzin, Francesca; Morton, Jennifer; Wiese, Katrin E; von Eyss, Björn; Herold, Steffi; Rycak, Lukas; Dumay-Odelot, Hélène; Karim, Saadia; Bartkuhn, Marek; Roels, Frederik; Wüstefeld, Torsten; Fischer, Matthias; Teichmann, Martin; Zender, Lars; Wei, Chia-Lin; Sansom, Owen; Wolf, Elmar; Eilers, Martin

    2014-07-24

    In mammalian cells, the MYC oncoprotein binds to thousands of promoters. During mitogenic stimulation of primary lymphocytes, MYC promotes an increase in the expression of virtually all genes. In contrast, MYC-driven tumour cells differ from normal cells in the expression of specific sets of up- and downregulated genes that have considerable prognostic value. To understand this discrepancy, we studied the consequences of inducible expression and depletion of MYC in human cells and murine tumour models. Changes in MYC levels activate and repress specific sets of direct target genes that are characteristic of MYC-transformed tumour cells. Three factors account for this specificity. First, the magnitude of response parallels the change in occupancy by MYC at each promoter. Functionally distinct classes of target genes differ in the E-box sequence bound by MYC, suggesting that different cellular responses to physiological and oncogenic MYC levels are controlled by promoter affinity. Second, MYC both positively and negatively affects transcription initiation independent of its effect on transcriptional elongation. Third, complex formation with MIZ1 (also known as ZBTB17) mediates repression of multiple target genes by MYC and the ratio of MYC and MIZ1 bound to each promoter correlates with the direction of response. PMID:25043018

  13. 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

  14. DEWAX-mediated transcriptional repression of cuticular wax biosynthesis in Arabidopsis thaliana

    PubMed Central

    Suh, Mi Chung; Go, Young Sam

    2014-01-01

    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. PMID:25763625

  15. 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.

  16. 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

  17. 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

  18. Mutant huntingtin represses CBP, but not p300, by binding and protein degradation.

    PubMed

    Cong, Shu-Yan; Pepers, Barry A; Evert, Bernd O; Rubinsztein, David C; Roos, Raymund A C; van Ommen, Gert-Jan B; Dorsman, Josephine C

    2005-12-01

    Huntington's disease can be used as a model to study neurodegenerative disorders caused by aggregation-prone proteins. It has been proposed that the entrapment of transcription factors in aggregates plays an important role in pathogenesis. We now report that the transcriptional activity of CBP is already repressed in the early time points by soluble mutant huntingtin, whereas the histone acetylase activity of CBP/p300 is gradually diminished over time. Mutant huntingtin bound much stronger to CBP than normal huntingtin, possibly contributing to repression. Especially at the later time points, CBP protein level was gradually reduced via the proteasome pathway. In sharp contrast, p300 was unaffected by mutant huntingtin. This selective degradation of CBP was absent in spinocerebellar ataxia 3. Thus, mutant huntingtin specifically affects CBP and not p300 both at the early and later time points, via multiple mechanisms. In addition to the reduction of CBP, also the altered ratio of these closely related histone acetyl transferases may affect chromatin structure and transcription and thus contribute to neurodegeneration. PMID:16456924

  19. Mutant huntingtin represses CBP, but not p300, by binding and protein degradation.

    PubMed

    Cong, Shu-Yan; Pepers, Barry A; Evert, Bernd O; Rubinsztein, David C; Roos, Raymund A C; van Ommen, Gert-Jan B; Dorsman, Josephine C

    2005-09-01

    Huntington's disease can be used as a model to study neurodegenerative disorders caused by aggregation-prone proteins. It has been proposed that the entrapment of transcription factors in aggregates plays an important role in pathogenesis. We now report that the transcriptional activity of CBP is already repressed in the early time points by soluble mutant huntingtin, whereas the histone acetylase activity of CBP/p300 is gradually diminished over time. Mutant huntingtin bound much stronger to CBP than normal huntingtin, possibly contributing to repression. Especially at the later time points, CBP protein level was gradually reduced via the proteasome pathway. In sharp contrast, p300 was unaffected by mutant huntingtin. This selective degradation of CBP was absent in spinocerebellar ataxia 3. Thus, mutant huntingtin specifically affects CBP and not p300 both at the early and later time points, via multiple mechanisms. In addition to the reduction of CBP, also the altered ratio of these closely related histone acetyltransferases may affect chromatin structure and transcription and thus contribute to neurodegeneration. PMID:15994095

  20. SUMOylation Regulates the Transcriptional Repression Activity of FOG-2 and Its Association with GATA-4

    PubMed Central

    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 (K312, 471, 915, 955). 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. PMID:23226341

  1. 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

  2. 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

  3. Transcriptional repression by MYB3R proteins regulates plant organ growth

    PubMed Central

    Kobayashi, Kosuke; Suzuki, Toshiya; Iwata, Eriko; Nakamichi, Norihito; Suzuki, Takamasa; Chen, Poyu; Ohtani, Misato; Ishida, Takashi; Hosoya, Hanako; Müller, Sabine; Leviczky, Tünde; Pettkó-Szandtner, Aladár; Darula, Zsuzsanna; Iwamoto, Akitoshi; Nomoto, Mika; Tada, Yasuomi; Higashiyama, Tetsuya; Demura, Taku; Doonan, John H; Hauser, Marie-Theres; Sugimoto, Keiko; Umeda, Masaaki; Magyar, Zoltán; Bögre, László; Ito, Masaki

    2015-01-01

    In multicellular organisms, temporal and spatial regulation of cell proliferation is central for generating organs with defined sizes and morphologies. For establishing and maintaining the post-mitotic quiescent state during cell differentiation, it is important to repress genes with mitotic functions. We found that three of the Arabidopsis MYB3R transcription factors synergistically maintain G2/M-specific genes repressed in post-mitotic cells and restrict the time window of mitotic gene expression in proliferating cells. The combined mutants of the three repressor-type MYB3R genes displayed long roots, enlarged leaves, embryos, and seeds. Genome-wide chromatin immunoprecipitation revealed that MYB3R3 binds to the promoters of G2/M-specific genes and to E2F target genes. MYB3R3 associates with the repressor-type E2F, E2FC, and the RETINOBLASTOMA RELATED proteins. In contrast, the activator MYB3R4 was in complex with E2FB in proliferating cells. With mass spectrometry and pairwise interaction assays, we identified some of the other conserved components of the multiprotein complexes, known as DREAM/dREAM in human and flies. In plants, these repressor complexes are important for periodic expression during cell cycle and to establish a post-mitotic quiescent state determining organ size. PMID:26069325

  4. 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

  5. Parallel pathways of repression and antirepression governing the transition to stationary phase in Bacillus subtilis.

    PubMed

    Banse, Allison V; Chastanet, Arnaud; Rahn-Lee, Lilah; Hobbs, Errett C; Losick, Richard

    2008-10-01

    The AbrB protein of the spore-forming bacterium Bacillus subtilis is a repressor of numerous genes that are switched on during the transition from the exponential to the stationary phase of growth. The gene for AbrB is under the negative control of the master regulator for entry into sporulation, Spo0A-P. It has generally been assumed that derepression of genes under the negative control of AbrB is achieved by Spo0A-P-mediated repression of abrB followed by rapid degradation of the AbrB protein. Here, we report that AbrB levels do decrease during the transition to stationary phase, but that this decrease is not the entire basis by which AbrB-controlled genes are derepressed. Instead, AbrB is inactivated by the product of a uncharacterized gene, abbA (formerly ykzF), whose transcription is switched on by Spo0A-P. The abbA gene encodes an antirepressor that binds to AbrB and prevents it from binding to DNA. Combining our results with previous findings, we conclude that Spo0A-P sets in motion two parallel pathways of repression and antirepression to trigger the expression of diverse categories of genes during the transition to stationary phase. PMID:18840696

  6. 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

  7. Chronic idiopathic urticaria, psychological co-morbidity and posttraumatic stress: the impact of alexithymia and repression.

    PubMed

    Hunkin, Victoria; Chung, Man Cheung

    2012-12-01

    The objective of this study was to investigate the interrelationship between chronic idiopathic urticaria (CIU), psychological co-morbidity, posttraumatic stress, repression and alexithymia. 89 participants with CIU and 105 without CIU responded to an online questionnaire. Both groups completed the general health questionnaire-12, the perceived stress scale, the posttraumatic stress diagnostic scale and the Toronto alexithymia scale-20 and were categorised into four defence mechanism groups (repressive, defensive, high-anxious, low-anxious). CIU participants also completed the Skindex-17 and a self-report severity measure. CIU participants reported higher levels of alexithymia than the control group and their defence mechanism was most likely to be categorised as defensive, with conscious self-image management reported alongside high manifest anxiety. Partial least squares analysis revealed significant paths between posttraumatic stress and CIU severity and psychological co-morbidity. Posttraumatic stress was associated with alexithymia and type of defence mechanism. Only being in the high-anxious group partially mediated the relationship between posttraumatic stress and CIU severity. In conclusion, there is evidence for a relationship between CIU and trauma. The severity of posttraumatic symptoms varies depending upon alexithymic traits and defence mechanisms used. Disease severity and psychological co-morbidity are differentially influenced by the relationships between trauma, alexithymic traits and defence mechanisms. PMID:22362490

  8. Repressive coping style: relationships with depression, pain, and pain coping strategies in lung cancer outpatients.

    PubMed

    Prasertsri, Nusara; Holden, Janean; Keefe, Francis J; Wilkie, Diana J

    2011-02-01

    Researchers have shown that coping style is related to pain and adjustment in people with chronic illness. This study was the first to examine how coping style related to pain, pain coping strategies, and depression in lung cancer outpatients. We conducted a comparative, secondary data analysis of 107 lung cancer patients (73% male, mean age 61.4±10.43 years, 88% Caucasian). As in prior studies, we classified patients into four coping style groups based on Marlowe-Crowne Social Desirability Scale and trait anxiety scores. The coping style groups were low-anxious (n=25); high-anxious (n=31); defensive high-anxious (n=21); and repressive (n=30). Compared to other coping style groups, the repressive group reported statistically significant lower mean scores for pain quality, pain catastrophizing, and depression. Assessing coping style by measuring personal characteristics such as social desirability and trait anxiety may help clinicians to identify vulnerable individuals with lung cancer who may be candidates for early and timely intervention efforts to enhance adjustment to pain. PMID:20557973

  9. 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

  10. MTF-1-Mediated Repression of the Zinc Transporter Zip10 Is Alleviated by Zinc Restriction

    PubMed Central

    Lichten, Louis A.; Ryu, Moon-Suhn; Guo, Liang; Embury, Jennifer; Cousins, Robert J.

    2011-01-01

    The regulation of cellular zinc uptake is a key process in the overall mechanism governing mammalian zinc homeostasis and how zinc participates in cellular functions. We analyzed the zinc transporters of the Zip family in both the brain and liver of zinc-deficient animals and found a large, significant increase in Zip10 expression. Additionally, Zip10 expression decreased in response to zinc repletion. Moreover, isolated mouse hepatocytes, AML12 hepatocytes, and Neuro 2A cells also respond differentially to zinc availability in vitro. Measurement of Zip10 hnRNA and actinomycin D inhibition studies indicate that Zip10 was transcriptionally regulated by zinc deficiency. Through luciferase promoter constructs and ChIP analysis, binding of MTF-1 to a metal response element located 17 bp downstream of the transcription start site was shown to be necessary for zinc-induced repression of Zip10. Furthermore, zinc-activated MTF-1 causes down-regulation of Zip10 transcription by physically blocking Pol II movement through the gene. Lastly, ZIP10 is localized to the plasma membrane of hepatocytes and neuro 2A cells. Collectively, these results reveal a novel repressive role for MTF-1 in the regulation of the Zip10 zinc transporter expression by pausing Pol II transcription. ZIP10 may have roles in control of zinc homeostasis in specific sites particularly those of the brain and liver. Within that context ZIP10 may act as an important survival mechanism during periods of zinc inadequacy. PMID:21738690

  11. MiR-133 promotes cardiac reprogramming by directly repressing Snai1 and silencing fibroblast signatures

    PubMed Central

    Muraoka, Naoto; Yamakawa, Hiroyuki; Miyamoto, Kazutaka; Sadahiro, Taketaro; Umei, Tomohiko; Isomi, Mari; Nakashima, Hanae; Akiyama, Mizuha; Wada, Rie; Inagawa, Kohei; Nishiyama, Takahiko; Kaneda, Ruri; Fukuda, Toru; Takeda, Shu; Tohyama, Shugo; Hashimoto, Hisayuki; Kawamura, Yoshifumi; Goshima, Naoki; Aeba, Ryo; Yamagishi, Hiroyuki; Fukuda, Keiichi; Ieda, Masaki

    2014-01-01

    Fibroblasts can be directly reprogrammed into cardiomyocyte-like cells (iCMs) by overexpression of cardiac transcription factors or microRNAs. However, induction of functional cardiomyocytes is inefficient, and molecular mechanisms of direct reprogramming remain undefined. Here, we demonstrate that addition of miR-133a (miR-133) to Gata4, Mef2c, and Tbx5 (GMT) or GMT plus Mesp1 and Myocd improved cardiac reprogramming from mouse or human fibroblasts by directly repressing Snai1, a master regulator of epithelial-to-mesenchymal transition. MiR-133 overexpression with GMT generated sevenfold more beating iCMs from mouse embryonic fibroblasts and shortened the duration to induce beating cells from 30 to 10 days, compared to GMT alone. Snai1 knockdown suppressed fibroblast genes, upregulated cardiac gene expression, and induced more contracting iCMs with GMT transduction, recapitulating the effects of miR-133 overexpression. In contrast, overexpression of Snai1 in GMT/miR-133-transduced cells maintained fibroblast signatures and inhibited generation of beating iCMs. MiR-133-mediated Snai1 repression was also critical for cardiac reprogramming in adult mouse and human cardiac fibroblasts. Thus, silencing fibroblast signatures, mediated by miR-133/Snai1, is a key molecular roadblock during cardiac reprogramming. PMID:24920580

  12. 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

  13. Puf3p induces translational repression of genes linked to oxidative stress

    PubMed Central

    Rowe, William; Kershaw, Christopher J.; Castelli, Lydia M.; Costello, Joseph L.; Ashe, Mark P.; Grant, Christopher M.; Sims, Paul F. G.; Pavitt, Graham D.; Hubbard, Simon J.

    2014-01-01

    In response to stress, the translation of many mRNAs in yeast can change in a fashion discordant with the general repression of translation. Here, we use machine learning to mine the properties of these mRNAs to determine specific translation control signals. We find a strong association between transcripts acutely translationally repressed under oxidative stress and those associated with the RNA-binding protein Puf3p, a known regulator of cellular mRNAs encoding proteins targeted to mitochondria. Under oxidative stress, a PUF3 deleted strain exhibits more robust growth than wild-type cells and the shift in translation from polysomes to monosomes is attenuated, suggesting puf3Δ cells perceive less stress. In agreement, the ratio of reduced:oxidized glutathione, a major antioxidant and indicator of cellular redox state, is increased in unstressed puf3Δ cells but remains lower under stress. In untreated conditions, Puf3p migrates with polysomes rather than ribosome-free fractions, but this is lost under stress. Finally, reverse transcriptase-polymerase chain reaction (RT-PCR) of Puf3p targets following affinity purification shows Puf3p-mRNA associations are maintained or increased under oxidative stress. Collectively, these results point to Puf3p acting as a translational repressor in a manner exceeding the global translational response, possibly by temporarily limiting synthesis of new mitochondrial proteins as cells adapt to the stress. PMID:24163252

  14. Sequestration and Inhibition of Daxx-Mediated Transcriptional Repression by PML

    PubMed Central

    Li, Hui; Leo, Christopher; Zhu, Jiang; Wu, Xiaoyang; O'Neil, Jennifer; Park, Eun-Ju; Chen, J. Don

    2000-01-01

    PML fuses with retinoic acid receptor α (RARα) in the t(15;17) translocation that causes acute promyelocytic leukemia (APL). In addition to localizing diffusely throughout the nucleoplasm, PML mainly resides in discrete nuclear structures known as PML oncogenic domains (PODs), which are disrupted in APL and spinocellular ataxia cells. We isolated the Fas-binding protein Daxx as a PML-interacting protein in a yeast two-hybrid screen. Biochemical and immunofluorescence analyses reveal that Daxx is a nuclear protein that interacts and colocalizes with PML in the PODs. Reporter gene assay shows that Daxx drastically represses basal transcription, likely by recruiting histone deacetylases. PML, but not its oncogenic fusion PML-RARα, inhibits the repressor function of Daxx. In addition, SUMO-1 modification of PML is required for sequestration of Daxx to the PODs and for efficient inhibition of Daxx-mediated transcriptional repression. Consistently, Daxx is found at condensed chromatin in cells that lack PML. These data suggest that Daxx is a novel nuclear protein bearing transcriptional repressor activity that may be regulated by interaction with PML. PMID:10669754

  15. Histone demethylase Lsd1 represses hematopoietic stem and progenitor cell signatures during blood cell maturation

    PubMed Central

    Kerenyi, Marc A; Shao, Zhen; Hsu, Yu-Jung; Guo, Guoji; Luc, Sidinh; O'Brien, Kassandra; Fujiwara, Yuko; Peng, Cong; Nguyen, Minh; Orkin, Stuart H

    2013-01-01

    Here, we describe that lysine-specific demethylase 1 (Lsd1/KDM1a), which demethylates histone H3 on Lys4 or Lys9 (H3K4/K9), is an indispensible epigenetic governor of hematopoietic differentiation. Integrative genomic analysis, combining global occupancy of Lsd1, genome-wide analysis of its substrates H3K4 monomethylation and dimethylation, and gene expression profiling, reveals that Lsd1 represses hematopoietic stem and progenitor cell (HSPC) gene expression programs during hematopoietic differentiation. We found that Lsd1 acts at transcription start sites, as well as enhancer regions. Loss of Lsd1 was associated with increased H3K4me1 and H3K4me2 methylation on HSPC genes and gene derepression. Failure to fully silence HSPC genes compromised differentiation of hematopoietic stem cells as well as mature blood cell lineages. Collectively, our data indicate that Lsd1-mediated concurrent repression of enhancer and promoter activity of stem and progenitor cell genes is a pivotal epigenetic mechanism required for proper hematopoietic maturation. DOI: http://dx.doi.org/10.7554/eLife.00633.001 PMID:23795291

  16. 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

  17. 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

  18. Runx1 repression by histone deacetylation is critical for Setbp1-induced mouse myeloid leukemia development

    PubMed Central

    Vishwakarma, Bandana A.; Nguyen, Nhu; Makishima, Hideki; Hosono, Naoko; Gudmundsson, Kristbjorn O.; Negi, Vijay; Oakley, Kevin; Han, Yufen; Przychodzen, Bartlomiej; Maciejewski, Jaroslaw P.; Du, Yang

    2015-01-01

    Abnormal activation of SETBP1 through overexpression or missense mutations is highly recurrent in various myeloid malignancies; however, it is unclear whether such activation alone is able to induce leukemia development. Here we show that Setbp1 overexpression in mouse bone marrow progenitors through retroviral transduction is capable of initiating leukemia development in irradiated recipient mice. Before leukemic transformation, Setbp1 overexpression significantly enhances the self-renewal of hematopoietic stem cells (HSCs) and expands granulocyte macrophage progenitors (GMPs). Interestingly, Setbp1 overexpression also causes transcriptional repression of critical hematopoiesis regulator gene Runx1 and this effect is crucial for Setbp1-induced transformation. Runx1 repression is induced by Setbp1-mediated recruitment of a nucleosome remodeling deacetylase (NuRD) complex to Runx1 promoters and can be reversed by treatment with histone deacetylase (HDAC) inhibitors Entinostat and Vorinostat. Moreover, treatment with these inhibitors caused efficient differentiation of Setbp1 activation-induced leukemia cells in vitro, and significantly extended the survival of mice transplanted with such leukemias, suggesting that HDAC inhibition could be an effective strategy for treating myeloid malignancies with SETBP1 activation. PMID:26205084

  19. 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

  20. 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

  1. 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

  2. RNA-binding protein RBM20 represses splicing to orchestrate cardiac pre-mRNA processing

    PubMed Central

    Maatz, Henrike; Jens, Marvin; Liss, Martin; Schafer, Sebastian; Heinig, Matthias; Kirchner, Marieluise; Adami, Eleonora; Rintisch, Carola; Dauksaite, Vita; Radke, Michael H.; Selbach, Matthias; Barton, Paul J.R.; Cook, Stuart A.; Rajewsky, Nikolaus; Gotthardt, Michael; Landthaler, Markus; Hubner, Norbert

    2014-01-01

    Mutations in the gene encoding the RNA-binding protein RBM20 have been implicated in dilated cardiomyopathy (DCM), a major cause of chronic heart failure, presumably through altering cardiac RNA splicing. Here, we combined transcriptome-wide crosslinking immunoprecipitation (CLIP-seq), RNA-seq, and quantitative proteomics in cell culture and rat and human hearts to examine how RBM20 regulates alternative splicing in the heart. Our analyses revealed the presence of a distinct RBM20 RNA-recognition element that is predominantly found within intronic binding sites and linked to repression of exon splicing with RBM20 binding near 3′ and 5′ splice sites. Proteomic analysis determined that RBM20 interacts with both U1 and U2 small nuclear ribonucleic particles (snRNPs) and suggested that RBM20-dependent splicing repression occurs through spliceosome stalling at complex A. Direct RBM20 targets included several genes previously shown to be involved in DCM as well as genes not typically associated with this disease. In failing human hearts, reduced expression of RBM20 affected alternative splicing of several direct targets, indicating that differences in RBM20 expression may affect cardiac function. Together, these findings identify RBM20-regulated targets and provide insight into the pathogenesis of human heart failure. PMID:24960161

  3. RNA-binding protein RBM20 represses splicing to orchestrate cardiac pre-mRNA processing.

    PubMed

    Maatz, Henrike; Jens, Marvin; Liss, Martin; Schafer, Sebastian; Heinig, Matthias; Kirchner, Marieluise; Adami, Eleonora; Rintisch, Carola; Dauksaite, Vita; Radke, Michael H; Selbach, Matthias; Barton, Paul J R; Cook, Stuart A; Rajewsky, Nikolaus; Gotthardt, Michael; Landthaler, Markus; Hubner, Norbert

    2014-08-01

    Mutations in the gene encoding the RNA-binding protein RBM20 have been implicated in dilated cardiomyopathy (DCM), a major cause of chronic heart failure, presumably through altering cardiac RNA splicing. Here, we combined transcriptome-wide crosslinking immunoprecipitation (CLIP-seq), RNA-seq, and quantitative proteomics in cell culture and rat and human hearts to examine how RBM20 regulates alternative splicing in the heart. Our analyses revealed the presence of a distinct RBM20 RNA-recognition element that is predominantly found within intronic binding sites and linked to repression of exon splicing with RBM20 binding near 3' and 5' splice sites. Proteomic analysis determined that RBM20 interacts with both U1 and U2 small nuclear ribonucleic particles (snRNPs) and suggested that RBM20-dependent splicing repression occurs through spliceosome stalling at complex A. Direct RBM20 targets included several genes previously shown to be involved in DCM as well as genes not typically associated with this disease. In failing human hearts, reduced expression of RBM20 affected alternative splicing of several direct targets, indicating that differences in RBM20 expression may affect cardiac function. Together, these findings identify RBM20-regulated targets and provide insight into the pathogenesis of human heart failure. PMID:24960161

  4. 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

    2016-01-01

    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

  5. Autophagy-regulating TP53INP2 mediates muscle wasting and is repressed in diabetes

    PubMed Central

    Sala, David; Ivanova, Saška; Plana, Natàlia; Ribas, Vicent; Duran, Jordi; Bach, Daniel; Turkseven, Saadet; Laville, Martine; Vidal, Hubert; Karczewska-Kupczewska, Monika; Kowalska, Irina; Straczkowski, Marek; Testar, Xavier; Palacín, Manuel; Sandri, Marco; Serrano, Antonio L.; Zorzano, Antonio

    2014-01-01

    A precise balance between protein degradation and synthesis is essential to preserve skeletal muscle mass. Here, we found that TP53INP2, a homolog of the Drosophila melanogaster DOR protein that regulates autophagy in cellular models, has a direct impact on skeletal muscle mass in vivo. Using different transgenic mouse models, we demonstrated that muscle-specific overexpression of Tp53inp2 reduced muscle mass, while deletion of Tp53inp2 resulted in muscle hypertrophy. TP53INP2 activated basal autophagy in skeletal muscle and sustained p62-independent autophagic degradation of ubiquitinated proteins. Animals with muscle-specific overexpression of Tp53inp2 exhibited enhanced muscle wasting in streptozotocin-induced diabetes that was dependent on autophagy; however, TP53INP2 ablation mitigated experimental diabetes-associated muscle loss. The overexpression or absence of TP53INP2 did not affect muscle wasting in response to denervation, a condition in which autophagy is blocked, further indicating that TP53INP2 alters muscle mass by activating autophagy. Moreover, TP53INP2 expression was markedly repressed in muscle from patients with type 2 diabetes and in murine models of diabetes. Our results indicate that TP53INP2 negatively regulates skeletal muscle mass through activation of autophagy. Furthermore, we propose that TP53INP2 repression is part of an adaptive mechanism aimed at preserving muscle mass under conditions in which insulin action is deficient. PMID:24713655

  6. 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

  7. 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

  8. 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

  9. 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

  10. The Ski oncoprotein interacts with the Smad proteins to repress TGFbeta signaling.

    PubMed

    Luo, K; Stroschein, S L; Wang, W; Chen, D; Martens, E; Zhou, S; Zhou, Q

    1999-09-01

    Smad proteins are critical signal transducers downstream of the receptors of the transforming growth factor-beta (TGFbeta) superfamily. On phosphorylation and activation by the active TGFbeta receptor complex, Smad2 and Smad3 form hetero-oligomers with Smad4 and translocate into the nucleus, where they interact with different cellular partners, bind to DNA, regulate transcription of various downstream response genes, and cross-talk with other signaling pathways. Here we show that a nuclear oncoprotein, Ski, can interact directly with Smad2, Smad3, and Smad4 on a TGFbeta-responsive promoter element and repress their abilities to activate transcription through recruitment of the nuclear transcriptional corepressor N-CoR and possibly its associated histone deacetylase complex. Overexpression of Ski in a TGFbeta-responsive cell line renders it resistant to TGFbeta-induced growth inhibition and defective in activation of JunB expression. This ability to overcome TGFbeta-induced growth arrest may be responsible for the transforming activity of Ski in human and avian cancer cells. Our studies suggest a new paradigm for inactivation of the Smad proteins by an oncoprotein through transcriptional repression. PMID:10485843

  11. 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

  12. Translational repression by the human iron-regulatory factor (IRF) in Saccharomyces cerevisiae.

    PubMed Central

    Oliveira, C C; Goossen, B; Zanchin, N I; McCarthy, J E; Hentze, M W; Stripecke, R

    1993-01-01

    The regulation of the synthesis of ferritin and erythroid 5-aminolevulinate synthase in mammalian cells is mediated by the interaction of the iron regulatory factor (IRF) with a specific recognition site, the iron responsive element (IRE), in the 5' untranslated regions (UTRs) of the respective mRNAs. A new modular expression system was designed to allow reconstruction of this regulatory system in Saccharomyces cerevisiae. This comprised two components: a constitutively expressed reporter gene (luc; encoding luciferase) preceded by a 5' UTR including an IRE sequence, and an inducibly expressed cDNA encoding human IRF. Induction of the latter led to the in vivo synthesis of IRF, which in turn showed IRE-binding activity and also repressed translation of the luc mRNA bearing an IRE-containing 5' UTR. The upper stem-loop region of an IRE, with no further IRE-specific flanking sequences, sufficed for recognition and repression by IRF. Translational regulation of IRE-bearing mRNAs could also be demonstrated in cell-free yeast extracts. This work defines a minimal system for IRF/IRE translational regulation in yeast that requires no additional mammalian-specific components, thus providing direct proof that IRF functions as a translational repressor in vivo. It should be a useful tool as the basis for more detailed studies of eukaryotic translational regulation. Images PMID:8265343

  13. Iron- and molybdenum-repressible outer membrane proteins in competent Azotobacter vinelandii.

    PubMed

    Page, W J; von Tigerstrom, M

    1982-07-01

    Azotobacter vinelandii produced three major proteins of 93,000, 85,000, and 81,000 daltons and a minor 77,000-dalton protein in the outer membrane of Fe-limited cells, and these cells were competent for transformation by DNA. The synthesis of these proteins was repressed in Fe-sufficient medium. Mo limitation of nitrogen-fixing cells resulted in the hyperproduction of a 44,000-dalton protein and the production of a minor 77,000-dalton protein in the outer membrane. Mo limitation enhanced competence in Fe-limited medium and induced competence in Fe-sufficient medium. The 44,000-dalton protein was replaced by a 45,000-dalton protein when Fe-sufficient medium also contained NH4+, but the cells were noncompetent. The synthesis of these proteins was repressed in Mo-sufficient medium and by NH4+ in Fe-limited medium. All of the culture supernatants contained a blue-white fluorescent material (absorbance maximum, 214 nm) which appeared to coordinate Fe3+, Fe2+, MoO4(2-), WO3(2-), and VO3(-). PMID:7085558

  14. HDAC8 and STAT3 repress BMF gene activity in colon cancer cells

    PubMed Central

    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

  15. The transcription factor TBX2 regulates melanogenesis in melanocytes by repressing Oca2.

    PubMed

    Chen, Yu; Pan, Li; Su, Zhongyuan; Wang, Jing; Li, Huirong; Ma, Xiaoyin; Liu, Yin; Lu, Fan; Qu, Jia; Hou, Ling

    2016-04-01

    The T-box transcription factor TBX2 is known for its role as a critical regulator of melanoma cell proliferation, but its role in regulating melanogenesis has not been widely studied. Here we use a series of experiments to show in primary and immortalized mouse melanocytes that TBX2 acts as regulator of melanogenesis by repressing the expression of the gene encoding the melanosomal protein OCA2. We find that α-MSH or forskolin, both of which stimulate melanogenesis, also reduce TBX2 expression, and that specific knockdown of TBX2 increases melanogenesis. This effect primarily involves an increase in Oca2 expression as the combined knockdown of both Tbx2 and Oca2 interferes with the Tbx2 knockdown-mediated increase in melanogenesis. Standard chromatin immunoprecipitation and reporter assays suggest that TBX2 represses Oca2 at least in part directly. Hence, the results suggest that TBX2 may act as a nexus linking cell proliferation and melanogenesis. PMID:26971330

  16. Piwi Modulates Chromatin Accessibility by Regulating Multiple Factors Including Histone H1 to Repress Transposons.

    PubMed

    Iwasaki, Yuka W; Murano, Kensaku; Ishizu, Hirotsugu; Shibuya, Aoi; Iyoda, Yumiko; Siomi, Mikiko C; Siomi, Haruhiko; Saito, Kuniaki

    2016-08-01

    PIWI-interacting RNAs (piRNAs) mediate transcriptional and post-transcriptional silencing of transposable element (TE) in animal gonads. In Drosophila ovaries, Piwi-piRNA complexes (Piwi-piRISCs) repress TE transcription by modifying the chromatin state, such as by H3K9 trimethylation. Here, we demonstrate that Piwi physically interacts with linker histone H1. Depletion of Piwi decreases H1 density at a subset of TEs, leading to their derepression. Silencing at these loci separately requires H1 and H3K9me3 and heterochromatin protein 1a (HP1a). Loss of H1 increases target loci chromatin accessibility without affecting H3K9me3 density at these loci, while loss of HP1a does not impact H1 density. Thus, Piwi-piRISCs require both H1 and HP1a to repress TEs, and the silencing is correlated with the chromatin state rather than H3K9me3 marks. These findings suggest that Piwi-piRISCs regulate the interaction of chromatin components with target loci to maintain silencing of TEs through the modulation of chromatin accessibility. PMID:27425411

  17. Repression by ARP-1 sensitizes apolipoprotein AI gene responsiveness to RXR alpha and retinoic acid.

    PubMed Central

    Widom, R L; Rhee, M; Karathanasis, S K

    1992-01-01

    The gene coding for apolipoprotein AI (apoAI), a lipid binding protein involved in the transport of cholesterol and other lipids in the plasma, is expressed in mammals predominantly in the liver and the intestine. Liver-specific expression is controlled by synergistic interactions between transcription factors bound to three separate sites, sites A (-214 to -192), B (-169 to -146), and C (-134 to -119), within a powerful liver-specific enhancer located between nucleotides -222 and -110 upstream of the apoAI gene transcription start site (+1). Previous studies in our laboratory have shown that ARP-1, a member of the nuclear receptor superfamily whose ligand is unknown (orphan receptor), binds to site A and represses transcription of the apoAI gene in liver cells. In a more recent series of experiments, we found that site A is a retinoic acid (RA) response element that responds preferentially to the recently identified RA-responsive receptor RXR alpha over the previously characterized RA receptors RAR alpha and RAR beta. In this study we investigated the combined effects of ARP-1 and RXR alpha on apoAI gene expression in liver cells. Transient transfection assays showed that site A is necessary and sufficient for RXR alpha-mediated transactivation of the apoAI gene basal promoter in human hepatoma HepG2 cells in the presence of RA and that this transactivation is abolished by increasing amounts of cotransfected ARP-1. Electrophoretic mobility shift assays and subsequent Scatchard analysis of the data revealed that ARP-1 and RXR alpha bind to site A with similar affinities. These assays also revealed that ARP-1 and RXR alpha bind to site A as heterodimers with an affinity approximately 10 times greater than that of either ARP-1 or RXR alpha alone. Further transfection assays in HepG2 cells, using as a reporter a construct containing the apoAI gene basal promoter and its upstream regulatory elements (including site A) in their natural context, revealed that RXR alpha

  18. 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

  19. 2D DIGE proteomic analysis highlights delayed postnatal repression of α-fetoprotein expression in homocystinuria model mice.

    PubMed

    Kamata, Shotaro; Akahoshi, Noriyuki; Ishii, Isao

    2015-01-01

    Cystathionine β-synthase-deficient (Cbs (-/-)) mice, an animal model for homocystinuria, exhibit hepatic steatosis and juvenile semilethality via as yet unknown mechanisms. The plasma protein profile of Cbs (-/-) mice was investigated by proteomic analysis using two-dimensional difference gel electrophoresis and matrix-assisted laser desorption/ionization-time of flight/mass spectrometry. We found hyperaccumulation of α-fetoprotein (AFP) and downregulation of most other plasma proteins. AFP was highly expressed in fetal liver, but its expression declined dramatically via transcriptional repression after birth in both wild-type and Cbs (-/-) mice. However, the repression was delayed in Cbs (-/-) mice, causing high postnatal AFP levels, which may relate to transcriptional repression of most plasma proteins originating from liver and the observed hepatic dysfunction. PMID:26199862

  20. 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

  1. 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

  2. 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

  3. Different mechanisms contribute to the E2-mediated transcriptional repression of human papillomavirus type 18 viral oncogenes.

    PubMed

    Demeret, C; Desaintes, C; Yaniv, M; Thierry, F

    1997-12-01

    Transcription of the human papillomavirus type 18 (HPV18) E6 and E7 oncogenes is repressed by the viral E2 protein. In C33 cells, we have previously shown that of the four E2 binding sites (E2 BS) present in the HPV18 long control region (LCR), only the binding site adjacent to the TATA box (E2 BS 1) was involved in E2-mediated repression. In the present study, we sought to determine whether this phenomenon was conserved in other cell lines. We first showed that all three E2 BS proximal to the P105 promoter were required for full repression of its activity in HeLa and HaCaT cells. Repression by E2 at E2 BS 2 occurred through the displacement of Sp1. Second, a truncated E2 product, lacking the N-terminal transactivation domain, repressed transcription more efficiently than the full-length protein. Repression was abolished when the N-terminal domain of E2 was replaced by the activation domain of VP16. The VP16-E2 chimeric protein could activate transcription from an LCR mutated in its TATA box. DNA-protein binding studies showed that E2 associates with its four binding sites in the LCR with similar affinities. However, challenge of such complexes with excess binding sites demonstrated that interaction with E2 BS 4 was the most stable while interaction with E2 BS 1 was the least stable. Furthermore, complexes with the full-length E2 were less stable than those formed with the N-terminally truncated protein. PMID:9371593

  4. Unraveling the regulatory network in Streptococcus pyogenes: the global response regulator CovR represses rivR directly.

    PubMed

    Roberts, Samantha A; Churchward, Gordon G; Scott, June R

    2007-02-01

    The response regulator CovR acts as a master regulator of virulence in Streptococcus pyogenes by repressing transcription of approximately 15% of the group A streptococcus genome directly or indirectly. We demonstrate that phosphorylated CovR represses transcription of rivR directly by binding to conserved sequences located downstream from the promoter to block procession of RNA polymerase. This establishes the first link in a regulatory network where CovR interacts directly with other proteins that modulate gene expression. PMID:16963575

  5. Life in the Cold: a Proteomic Study of Cold-Repressed Proteins in the Antarctic Bacterium Pseudoalteromonas haloplanktis TAC125▿†

    PubMed Central

    Piette, Florence; D'Amico, Salvino; Mazzucchelli, Gabriel; Danchin, Antoine; Leprince, Pierre; Feller, Georges

    2011-01-01

    The proteomes expressed at 4°C and 18°C by the psychrophilic Antarctic bacterium Pseudoalteromonas haloplanktis were compared using two-dimensional differential in-gel electrophoresis with special reference to proteins repressed by low temperatures. Remarkably, the major cold-repressed proteins, almost undetectable at 4°C, were heat shock proteins involved in folding assistance. PMID:21478318

  6. Invasive filamentous growth of Candida albicans is promoted by Czf1p-dependent relief of Efg1p-mediated repression.

    PubMed Central

    Giusani, Angela D; Vinces, Marcelo; Kumamoto, Carol A

    2002-01-01

    Filamentation of Candida albicans occurs in response to many environmental cues. During growth within matrix, Efg1p represses filamentation and Czf1p relieves this repression. We propose that Czf1p interacts with Efg1p, altering its function. The complex regulation of filamentation may reflect the versatility of C. albicans as a pathogen. PMID:11973327

  7. MLL repression domain interacts with histone deacetylases, the polycomb group proteins HPC2 and BMI-1, and the corepressor C-terminal-binding protein

    PubMed Central

    Xia, Zhen-Biao; Anderson, Melanie; Diaz, Manuel O.; Zeleznik-Le, Nancy J.

    2003-01-01

    The MLL (mixed-lineage leukemia) gene is involved in many chromosomal translocations associated with acute myeloid and lymphoid leukemia. We previously identified a transcriptional repression domain in MLL, which contains a region with homology to DNA methyltransferase. In chromosomal translocations, the MLL repression domain is retained in the leukemogenic fusion protein and is required for transforming activity of MLL fusion proteins. We explored the mechanism of action of the MLL repression domain. Histone deacetylase 1 interacts with the MLL repression domain, partially mediating its activity; binding of Cyp33 to the adjacent MLL-PHD domain potentiates this binding. Because the MLL repression domain activity was only partially relieved with the histone deacetylase inhibitor trichostatin A, we explored other protein interactions with this domain. Polycomb group proteins HPC2 and BMI-1 and the corepressor C-terminal-binding protein also bind the MLL repression domain. Expression of exogenous BMI-1 potentiates MLL repression domain activity. Functional antagonism between Mll and Bmi-1 has been shown genetically in murine knockout models for Mll and Bmi-1. Our new data suggest a model whereby recruitment of BMI-1 to the MLL protein may be able to modulate its function. Furthermore, repression mediated by histone deacetylases and that mediated by polycomb group proteins may act either independently or together for MLL function in vivo. PMID:12829790

  8. STAT3 Represses Nitric Oxide Synthesis in Human Macrophages upon Mycobacterium tuberculosis Infection

    PubMed Central

    Queval, Christophe J.; Song, Ok-Ryul; Deboosère, Nathalie; Delorme, Vincent; Debrie, Anne-Sophie; Iantomasi, Raffaella; Veyron-Churlet, Romain; Jouny, Samuel; Redhage, Keely; Deloison, Gaspard; Baulard, Alain; Chamaillard, Mathias; Locht, Camille; Brodin, Priscille

    2016-01-01

    Mycobacterium tuberculosis is a successful intracellular pathogen. Numerous host innate immune responses signaling pathways are induced upon mycobacterium invasion, however their impact on M. tuberculosis replication is not fully understood. Here we reinvestigate the role of STAT3 specifically inside human macrophages shortly after M. tuberculosis uptake. We first show that STAT3 activation is mediated by IL-10 and occurs in M. tuberculosis infected cells as well as in bystander non-colonized cells. STAT3 activation results in the inhibition of IL-6, TNF-α, IFN-γ and MIP-1β. We further demonstrate that STAT3 represses iNOS expression and NO synthesis. Accordingly, the inhibition of STAT3 is detrimental for M. tuberculosis intracellular replication. Our study thus points out STAT3 as a key host factor for M. tuberculosis intracellular establishment in the early stages of macrophage infection. PMID:27384401

  9. Long term consequences of suppression of intrusive anxious thoughts and repressive coping.

    PubMed

    Geraerts, Elke; Merckelbach, Harald; Jelicic, Marko; Smeets, Elke

    2006-10-01

    The current experiment employed a thought suppression paradigm to investigate whether repressors (N=40) are more skilled in suppressing positive and anxious autobiographical thoughts than low anxious (N=40), high anxious (N=40), and defensive high anxious (N=40) individuals, both immediately and over a longer time period (i.e., 7 days). Regardless of suppression instructions, repressors reported during their lab visit fewer target thoughts for their most anxious events than participants in the other three groups. However, over a 7 days period, repressors showed the highest number of intrusive thoughts about their anxious autobiographical events. Thus, our results demonstrate that repressive coping might be adaptive in the short run, but counterproductive in the long run. PMID:16337604

  10. Assembly of the SMRT–histone deacetylase 3 repression complex requires the TCP-1 ring complex

    PubMed Central

    Guenther, Matthew G.; Yu, Jiujiu; Kao, Gary D.; Yen, Tim J.; Lazar, Mitchell A.

    2002-01-01

    The acetylation of histone tails is a primary determinant of gene activity. Histone deacetylase 3 (HDAC3) requires the nuclear receptor corepressor SMRT for HDAC enzyme activity. Here we report that HDAC3 interacts with SMRT only after priming by cellular chaperones including the TCP-1 ring complex (TRiC), which is required for proper folding of HDAC3 in an ATP-dependent process. SMRT displaces TRiC from HDAC3, yielding an active HDAC enzyme. The SMRT–HDAC3 repression complex thus joins the VHL–elongin BC tumor suppression complex and the cyclin E–Cdk2 cell cycle regulation complex as critical cellular machines requiring TRiC for proper assembly and function. The strict control of HDAC3 activity underscores the cellular imperative that histone deacetylation occur only in targeted regions of the genome. PMID:12502735

  11. Agency and expression despite repression: a comparative study of five ethiopian lesbians.

    PubMed

    Ephrem, Betelhem; White, Aaronette M

    2011-01-01

    Same-sex sexual practices are illegal in Ethiopia; consequently, little is known about Ethiopian lesbians. We explored the lives of five Ethiopian lesbians in order to understand their sexuality from their perspectives. We were particularly interested in how they perceived their sexual identities and practices, the obstacles they faced, and how they coped with such obstacles. Three major themes emerged from their responses to a semi-structured questionnaire, which we analyze from radical, African feminist perspectives. First, these women consistently described the negative impact of Ethiopian laws on their lives. Second, all testified to experiences of sexual agency, despite repression. Finally, their responses revealed considerable diversity and fluidity regarding sexual desire, attraction, and sexual behavior, demonstrating the complexities of lesbian sexuality. We conclude with recommendations for future research and lesbian activism. PMID:21491317

  12. Sucrose Represses the Developmentally Controlled Transient Activation of the Plastocyanin Gene in Arabidopsis thaliana Seedlings.

    PubMed Central

    Dijkwel, P. P.; Kock, PAM.; Bezemer, R.; Weisbeek, P. J.; Smeekens, SCM.

    1996-01-01

    The plastocyanin (PC) gene of Arabidopsis thaliana is activated independently of light during early seedling development. In etiolated seedlings, PC mRNA levels increase transiently and a maximum dark level is reached after 2 d of growth in darkness. In etiolated transgenic seedlings carrying a chimeric PC-promoter: luciferase fusion gene, luciferase activity is similarly increased after 2 d of growth. The transient increase in PC mRNA and luciferase activity levels can be repressed by sucrose. Nonmetabolizable sugars and polyethylene glycol do not have a major effect on PC gene expression. Also, light-grown seedlings show a similar transient and sucrose-sensitive increase in PC mRNA levels and luciferase activity, as in dark-grown seedlings, but here expression levels are 15- fold higher. These findings suggest the presence of a sucrose-sensitive, developmentally controlled expression mechanism that operates independently of light. PMID:12226197

  13. 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. PMID:26289535

  14. Using synthetic bacterial enhancers to reveal a looping-based mechanism for quenching-like repression

    NASA Astrophysics Data System (ADS)

    Brunwasser-Meirom, Michal; Pollak, Yaroslav; Goldberg, Sarah; Levy, Lior; Atar, Orna; Amit, Roee

    2016-02-01

    We explore a model for `quenching-like' repression by studying synthetic bacterial enhancers, each characterized by a different binding site architecture. To do so, we take a three-pronged approach: first, we compute the probability that a protein-bound dsDNA molecule will loop. Second, we use hundreds of synthetic enhancers to test the model's predictions in bacteria. Finally, we verify the mechanism bioinformatically in native genomes. Here we show that excluded volume effects generated by DNA-bound proteins can generate substantial quenching. Moreover, the type and extent of the regulatory effect depend strongly on the relative arrangement of the binding sites. The implications of these results are that enhancers should be insensitive to 10-11 bp insertions or deletions (INDELs) and sensitive to 5-6 bp INDELs. We test this prediction on 61 σ54-regulated qrr genes from the Vibrio genus and confirm the tolerance of these enhancers' sequences to the DNA's helical repeat.

  15. Site-Specific Oligonucleotide Binding Represses Transcription of the Human c-myc Gene in vitro

    NASA Astrophysics Data System (ADS)

    Cooney, Michael; Czernuszewicz, Graznya; Postel, Edith H.; Flint, S. Jane; Hogan, Michael E.

    1988-07-01

    A 27-base-long DNA oligonucleotide was designed that binds to duplex DNA at a single site within the 5' end of the human c-myc gene, 115 base pairs upstream from the transcription origin P1. On the basis of the physical properties of its bound complex, it was concluded that the oligonucleotide forms a colinear triplex with the duplex binding site. By means of an in vitro assay system, it was possible to show a correlation between triplex formation at -115 base pairs and repression of c-myc transcription. The possibility is discussed that triplex formation (site-specific RNA binding to a DNA duplex) could serve as the basis for an alternative program of gene control in vivo.

  16. A hot L1 retrotransposon evades somatic repression and initiates human colorectal cancer.

    PubMed

    Scott, Emma C; Gardner, Eugene J; Masood, Ashiq; Chuang, Nelson T; Vertino, Paula M; Devine, Scott E

    2016-06-01

    Although human LINE-1 (L1) elements are actively mobilized in many cancers, a role for somatic L1 retrotransposition in tumor initiation has not been conclusively demonstrated. Here, we identify a novel somatic L1 insertion in the APC tumor suppressor gene that provided us with a unique opportunity to determine whether such insertions can actually initiate colorectal cancer (CRC), and if so, how this might occur. Our data support a model whereby a hot L1 source element on Chromosome 17 of the patient's genome evaded somatic repression in normal colon tissues and thereby initiated CRC by mutating the APC gene. This insertion worked together with a point mutation in the second APC allele to initiate tumorigenesis through the classic two-hit CRC pathway. We also show that L1 source profiles vary considerably depending on the ancestry of an individual, and that population-specific hot L1 elements represent a novel form of cancer risk. PMID:27197217

  17. Response to Comment on "Multiple repressive mechanisms in the hippocampus during memory formation".

    PubMed

    Cho, Jun; Yu, Nam-Kyung; Kim, V Narry; Kaang, Bong-Kiun

    2016-07-29

    Mathew et al. propose that many candidate genes identified in our study may reflect the events in the choroid plexus (ChP) potentially included in hippocampal samples. We reanalyze our data and find that the ChP inclusion is unlikely to affect our major conclusions regarding the basal suppression of translational machinery or the early translational repression (at 5 to 10 minutes). As Mathew et al. examined for a subset of genes at 4 hours, we agree that the late suppression may partly reflect the events in the ChP. Although the precise contribution of anatomical sources remains to be clarified, our behavioral analyses indicate that the late-phase suppression of these genes may contribute to memory formation. PMID:27482553

  18. 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

  19. 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