Biomedical subjects

T Hai

Publications and source records attributed to T Hai.

At least 19 recordsLinked to original sources

PubMed2006

Induction of activating transcription factor 3 by anoxia is independent of p53 and the hypoxic HIF signalling pathway.

Solid tumors often have an inadequate blood supply, which results in large regions that are subjected to hypoxic or anoxic stress. Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that regulates much of the transcriptional response of cells to hypoxia. Activating transcription factor 3 (ATF3) is another transcription factor that responds to a variety of stresses and is often upregulated in cancer. We investigated the regulation of ATF3 by oxygen deprivation. ATF3 induction occurred most robustly under anoxia, is common, and it is not dependent on presence of HIF-1 or p53, but is sensitive to the inhibition of c-Jun NH2-terminal kinase activation and the antioxidant N-acetylcystein. ATF3 could also be induced by desferrioxamine but not by the mitochondrial poison cyanide or the nonspecific 2-oxoglutarate dioxygenase inhibitor dimethyloxalylglycine. We also show that anoxic ATF3 mRNA is more stable than normoxic mRNA providing a mechanism for this induction. Thus, this study demonstrates that the regulation of ATF3 under anoxia is independent of 2-oxoglutarate dioxygenase, HIF-1 and p53, presumably involving multiple regulatory pathways.

Acetylcysteine↗

PubMed2001

The molecular biology and nomenclature of the activating transcription factor/cAMP responsive element binding family of transcription factors: activating transcription factor proteins and homeostasis.

The mammalian ATF/CREB family of transcription factors represents a large group of basic region-leucine zipper (bZip) proteins which was originally defined in the late 1980s by their ability to bind to the consensus ATF/CRE site 'TGACGTCA'. Over the past decade, cDNA clones encoding identical or homologous proteins have been isolated by different laboratories and given different names. These proteins can be grouped into subgroups according to their amino acid similarity. In this review, we will briefly describe the classification of these proteins with a historical perspective of their nomenclature. We will then review three members of the ATF/CREB family of proteins: ATF3, ATF4 and ATF6. We will address four issues for each protein: (a) homologous proteins and alternative names, (b) dimer formation with other bZip proteins, (c) transcriptional activity, and (d) potential physiological functions. Although the name Activating Transcription Factor (ATF) implies that they are transcriptional activators, some of these proteins are transcriptional repressors. ATF3 homodimer is a transcriptional repressor and ATF4 has been reported to be either an activator or a repressor. We will review the reports on the transcriptional activities of ATF4, and propose potential explanations for the discrepancy. Although the physiological functions of these proteins are not well understood, some clues can be gained from studies with different approaches. When the data are available, we will address the following questions. (a) How is the expression (at the mRNA level or protein level) regulated? (b) How are the transcriptional activities regulated? (c) What are the interacting proteins (other than bZip partners)? (d) What are the consequences of ectopically expressing the gene (gain-of-function) or deleting the gene (loss-of-function)? Although answers to these questions are far from being complete, together they provide clues to the functions of these ATF proteins. Despite the diversity in the potential functions of these proteins, one common theme is their involvement in cellular responses to extracellular signals, indicating a role for these ATF proteins in homeostasis.

Activating Transcription Factor 2↗

PubMed2001

NF-kappa B-inducible BCL-3 expression is an autoregulatory loop controlling nuclear p50/NF-kappa B1 residence.

NF-kappa B is a transcription factor whose nuclear residence is controlled by I kappa B family members. In the NF-kappa B-I kappa B autoregulatory loop, activated (nuclear) Rel A.NF-kappa B1 induces the resynthesis of I kappa B alpha recapturing nuclear Rel A back into the cytoplasm within 1 h of stimulation. In contrast, NF-kappa B1 subunits redistribute more slowly into the cytoplasm (from 6 to 12 h). Here we examine the role of inducible cytoplasmic BCL-3 expression in terminating nuclear NF-kappa B1. Although BCL-3 is a nuclear protein in B lymphocytes, surprisingly, BCL-3 is primarily a cytoplasmic protein in HepG2 cells. Cytoplasmic BCL-3 abundance is induced 6-12 h after tumor necrosis factor-alpha stimulation where it complexes with NF-kappa B1 homodimers. Moreover, BCL-3 mRNA and protein expression are induced by NF-kappa B-activating agents. Two observations are interpreted to indicate that bcl-3 is transactivated by NF-kappa B/Rel A: 1) expression of a dominant negative NF-kappa B inhibitor blocks tumor necrosis factor-alpha-induced BCL-3 expression and 2) expression of constitutively active Rel A is sufficient to induce BCL-3 expression. In gene transfer studies, we identify two high affinity NF-kappa B-binding sites, kappa B1 (located at -872 to -861 nucleotides) and kappa B2 (-106 to -96 nucleotides), and although both bind with high affinity to Rel A, only kappa B2 is required for NF-kappa B-dependent induction of the native BCL-3 promoter. Down-regulation of BCL-3 induction results in prolonged, enhanced NF-kappa B1 binding and increased NF-kappa B-dependent transcription. Together, these data suggest the presence of an NF-kappa B-BCL-3 autoregulatory loop important in terminating NF-kappa B1 action and that individual NF-kappa B isoforms are actively terminated through coordinate induction of inhibitory I kappa B molecules to restore cellular homeostasis.

B-Cell Lymphoma 3 Protein↗

PubMed2001

The roles of ATF3 in glucose homeostasis. A transgenic mouse model with liver dysfunction and defects in endocrine pancreas.

Activating transcription factor 3 (ATF3) is a member of the ATF/cAMP-response element-binding protein family of transcription factors. It is a transcriptional repressor, and the expression of its corresponding gene is induced by stress signals in a variety of tissues, including the liver. In this report, we demonstrate that ATF3 is induced in the pancreas by partial pancreatectomy, streptozotocin treatment, and ischemia coupled with reperfusion. Furthermore, ATF3 is induced in cultured islet cells by oxidative stress. Interestingly, transgenic mice expressing ATF3 in the liver and pancreas under the control of the transthyretin promoter have defects in glucose homeostasis and perinatal lethality. We present evidence that expression of ATF3 in the liver represses the expression of genes encoding gluconeogenic enzymes. Furthermore, expression of ATF3 in the pancreas leads to abnormal endocrine pancreas and reduced numbers of hormone-producing cells. Analyses of embryos indicated that the ATF3 transgene is expressed in the ductal epithelium in the developing pancreas, and the transgenic pancreas has fewer mitotic cells than the non-transgenic counterpart, providing a potential explanation for the reduction of endocrine cells. Because ATF3 is a stress-inducible gene, these mice may represent a model to investigate the molecular mechanisms for some stress-associated diseases.

Activating Transcription Factor 3↗

PubMed2001

On-site field sampling and analysis of fragrance from living lavender (Lavandula angustifolia L.) flowers by solid-phase microextraction coupled to gas chromatography and ion-trap mass spectrometry.

Solid-phase microextraction coupled to gas chromatography and mass spectrometry has been applied as a simple alternative method for the analysis of essential oil directly from lavender intact flowering spikes and genuine oils. All recognised major oil constituents were detected by this procedure, with results comparable to those given by a conventional method (organic solvent extraction). Distinctive chromatographic profiles were found for various species.

Gas Chromatography-Mass Spectrometry↗

PubMed2001

Transgenic mice with cardiac-specific expression of activating transcription factor 3, a stress-inducible gene, have conduction abnormalities and contractile dysfunction.

Activating transcription factor 3 (ATF3) is a member of the CREB/ATF family of transcription factors. Previously, we demonstrated that the expression of the ATF3 gene is induced by many stress signals. In this report, we demonstrate that expression of ATF3 is induced by cardiac ischemia coupled with reperfusion (ischemia-reperfusion) in both cultured cells and an animal model. Transgenic mice expressing ATF3 under the control of the alpha-myosin heavy chain promoter have atrial enlargement, and atrial and ventricular hypertrophy. Microscopic examination showed myocyte degeneration and fibrosis. Functionally, the transgenic heart has reduced contractility and aberrant conduction. Interestingly, expression of sorcin, a gene whose product inhibits the release of calcium from sarcoplasmic reticulum, is increased in these transgenic hearts. Taken together, our results indicate that expression of ATF3, a stress-inducible gene, in the heart leads to altered gene expression and impaired cardiac function.

Activating Transcription Factor 3↗

PubMed2001

Multiple evidence for widespread and general occurrence of type-III PHA synthases in cyanobacteria and molecular characterization of the PHA synthases from two thermophilic cyanobacteria: Chlorogloeopsis fritschii PCC 6912 and Synechococcus sp. strain MA19.

Eleven different cyanobacteria were investigated with respect to their capabilities to synthesize poly-3-hydroxybutyrate [poly(3HB)] and the type of poly-beta-hydroxyalkanoic acid (PHA) synthase accounting for the synthesis of this polyester. Several methods, including (i) Southern blot analysis using a phaC-specific DNA probe, (ii) Western blot analysis using specific polyclonal anti-PhaE antibodies raised in this study against PhaE of Synechocystis sp. strain PCC 6803, (iii) generation and sequence analysis of PCR products using phaC-specific oligonucleotides as primers, and/or (iv) cloning and sequence analysis of PHA synthase structural genes, were used to provide evidence for the presence of a type-III PHA synthase in the following cyanobacteria: Synechococcus sp. strains MA19 and PCC 6715, Chlorogloeopsis fritschii PCC 6912, Anabaena cylindrica SAG 1403-2, Cyanothece sp. strains PCC 7424, PCC 8303 and PCC 8801, and Gloeocapsa sp. strain PCC 7428. The screening was compared with corresponding studies using crude protein extracts and genomic DNA of Synechocystis sp. strain PCC 6803, as a positive control, which is so far the only cyanobacterium for which molecular data of the PHA synthase genes are available. No evidence for the presence of a type-III PHA synthase could be obtained for only three of the eleven investigated cyanobacteria (Stanieria sp. strain PCC 7437, Cyanothece sp. strain PCC 8955 and Gloeothece sp. strain PCC 6501). The entire PHA synthase structural genes of the two thermophilic cyanobacteria Synechococcus sp. strain MA19 and Chlorogloeopsis fritschii PCC 6912, and in addition a central region of the phaC gene of Cyanothece sp. strain PCC 8303, were cloned, sequenced and also heterologously expressed in Escherichia coli.

Acyltransferases↗

PubMed2001

ATF4 degradation relies on a phosphorylation-dependent interaction with the SCF(betaTrCP) ubiquitin ligase.

The ubiquitin-proteasome pathway regulates gene expression through protein degradation. Here we show that the F-box protein betaTrCP, the receptor component of the SCF E3 ubiquitin ligase responsible for IkappaBalpha and beta-catenin degradation, is colocalized in the nucleus with ATF4, a member of the ATF-CREB bZIP family of transcription factors, and controls its stability. Association between the two proteins depends on ATF4 phosphorylation and on ATF4 serine residue 219 present in the context of DSGXXXS, which is similar but not identical to the motif found in other substrates of betaTrCP. ATF4 ubiquitination in HeLa cells is enhanced in the presence of betaTrCP. The F-box-deleted betaTrCP protein behaves as a negative transdominant mutant that inhibits ATF4 ubiquitination and degradation and, subsequently, enhances its activity in cyclic AMP-mediated transcription. ATF4 represents a novel substrate for the SCF(betaTrCP) complex, which is the first mammalian E3 ubiquitin ligase identified so far for the control of the degradation of a bZIP transcription factor.

Activating Transcription Factor 4↗

PubMed2000

Transcriptional autorepression of the stress-inducible gene ATF3.

Previously, we demonstrated that ATF3 (activating transcription factor-3) is a stress-inducible gene, and the protein it encodes is a transcriptional repressor. In this report, we present evidence suggesting that ATF3 represses the transcription of its own gene. Interestingly, efficient repression requires a consensus ATF/cAMP-responsive element site in the promoter and a previously unidentified ATF3-binding site immediately downstream from the TATA box. Although this new site resembles the known ATF/cAMP-responsive element sequences at the flanking sequence, it differs from them at the center key residues. These observations indicate that ATF3 can tolerate variations in the center of the binding sites if the flanking sequences are favorable. The repression of the ATF3 promoter by its own gene product provides a mechanistic explanation, at least in part, for the transient expression pattern of the ATF3 gene upon stress induction.

Activating Transcription Factor 3↗

PubMed2000

Axenic cultivation of anoxygenic phototrophic bacteria, cyanobacteria, and microalgae in a new closed tubular glass photobioreactor.

A low-cost closed tubular glass photobioreactor allowing axenic cultivation of phototrophic microorganisms was constructed. Standard glass tubes were arranged in a helical array providing a working volume of 80 1. The glass tubes were connected with a degassing chamber, which also provided ports for measuring and regulating oxygen supply, pH, foam, and optical density and for adding substrates and antifoam agents as well as disposing of vent gas. A pump module allowed agitation of the medium in the bioreactor at a laminar flow rate of 1.5 m/s. Upstream of the pump module a gas inlet was located, allowing efficient mixing of the used gases with the medium. The temperature of the medium was controlled by a Pt-100 sensor and by a heat exchanger with an effective surface of 0.12 m2 connected to an external thermostat. Irradiation was provided by three light panels each consisting of ten fluorescent tubes. The entire photobioreactor - apart from the light panels and motor - could be sterilized at 121 degrees C in an autoclave. In addition to a detailed description of this photobioreactor, we report on first experiments to cultivate the anoxygenic phototrophic bacteria Rhodobacter sphaeroides and Rhodospirillum rubrum, the oxygenic phototrophic cyanobacterium Synechocystis sp. strain PCC6803, and the microalga Chlorella sp. in this photobioreactor.

Bacteria↗

PubMed1999

Purification and characterization of cyanophycin and cyanophycin synthetase from the thermophilic Synechococcus sp. MA19.

The biosynthesis and accumulation of cyanophycin in the thermophilic cyanobacterium Synechococcus sp. MA19 were studied. By growing the cells in a 80-l closed tubular photobioreactor under controlled conditions, the cells accumulated cyanophycin amounting up to 3.5% of the dry cell matter. The cyanophycin was purified and chemical analysis showed that it was composed of arginine and aspartic acid occurring at a molar ratio of 1:0.9. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a broad distribution of the apparent molecular masses ranging from 20 to 130 kDa with a maximum at 50 kDa. During a three-step purification procedure involving ion exchange chromatography and gel filtration, the cyanophycin synthetase from strain MA19 was purified 144-fold to electrophoretic homogeneity. It consisted of only one single type of subunit exhibiting an apparent molecular mass of 130 kDa. The enzyme catalyzed the polymerization of arginine and aspartate at elevated temperatures and was even active at 80 degrees C.

Arginine↗

PubMed1999

Complexes containing activating transcription factor (ATF)/cAMP-responsive-element-binding protein (CREB) interact with the CCAAT/enhancer-binding protein (C/EBP)-ATF composite site to regulate Gadd153 expression during the stress response.

Gadd153, also known as chop, encodes a member of the CCAAT/enhancer-binding protein (C/EBP) transcription factor family and is transcriptionally activated by cellular stress signals. We recently demonstrated that arsenite treatment of rat pheochromocytoma PC12 cells results in the biphasic induction of Gadd153 mRNA expression, controlled in part through binding of C/EBPbeta and two uncharacterized protein complexes to the C/EBP-ATF (activating transcription factor) composite site in the Gadd153 promoter. In this report, we identified components of these additional complexes as two ATF/CREB (cAMP-responsive-element-binding protein) transcription factors having differential binding activities dependent upon the time of arsenite exposure. During arsenite treatment of PC12 cells, we observed enhanced binding of ATF4 to the C/EBP-ATF site at 2 h as Gadd153 mRNA levels increased, and enhanced binding of ATF3 complexes at 6 h as Gadd153 expression declined. We further demonstrated that ATF4 activates, while ATF3 represses, Gadd153 promoter activity through the C/EBP-ATF site. ATF3 also repressed ATF4-mediated transactivation and arsenite-induced activation of the Gadd153 promoter. Our results suggest that numerous members of the ATF/CREB family are involved in the cellular stress response, and that regulation of stress-induced biphasic Gadd153 expression in PC12 cells involves the ordered, sequential binding of multiple transcription factor complexes to the C/EBP-ATF composite site.

Animals↗

PubMed1999

ATF3 and stress responses.

The purpose of this review is to discuss ATF3, a member of the ATF/CREB family of transcription factors, and its roles in stress responses. In the introduction, we briefly describe the ATF/CREB family, which contains more than 10 proteins with the basic region-leucine zipper (bZip) DNA binding domain. We summarize their DNA binding and heterodimer formation with other bZip proteins, and discuss the nomenclature of these proteins. Over the years, identical or homologous cDNA clones have been isolated by different laboratories and given different names. We group these proteins into subgroups according to their amino acid similarity; we also list the alternative names for each member, and clarify some potential confusion in the nomenclature of this family of proteins. We then focus on ATF3 and its potential roles in stress responses. We review the evidence that the mRNA level of ATF3 greatly increases when the cells are exposed to stress signals. In animal experiments, the signals include ischemia, ischemia coupled with reperfusion, wounding, axotomy, toxicity, and seizure; in cultured cells, the signals include serum factors, cytokines, genotoxic agents, cell death-inducing agents, and the adenoviral protein E1A. Despite the overwhelming evidence for its induction by stress signals, not much else is known about ATF3. Preliminary results suggest that the JNK/SAPK pathway is involved in the induction of ATF3 by stress signals; in addition, IL-6 and p53 have been demonstrated to be required for the induction of ATF3 under certain conditions. The consequences of inducing ATF3 during stress responses are not clear. Transient transfection and in vitro transcription assays indicate that ATF3 represses transcription as a homodimer; however, ATF3 can activate transcription when coexpressed with its heterodimeric partners or other proteins. Therefore, it is possible that, when induced during stress responses, ATF3 activates some target genes but represses others, depending on the promoter context and cellular context. Even less is understood about the physiological significance of inducing ATF3. We will discuss our preliminary results and some reports by other investigators in this regard.

Activating Transcription Factor 3↗

PubMed1999

Biochemical changes of plasma in paratroops after parachuting: a preliminary investigation.

OBJECTIVE: To study whether physiological and psychological stresses during parachuting jumps may result in biochemical changes of plasma in parachutists. METHOD: Differences in the levels of hormones (cortisol, growth hormone, insulin, pancreatic glucagon, endothelin, angiotonin I and II, aldosterone), activities of enzymes (superoxide dismutase, glutathione peroxidase, glutathione S transferase), levels of the free radical damage indicator malondialdehyde (MDA), tumor necrosis factor alpha (TNF-alpha), and the main heat stress protein, HSP70, in the plasma and serum were investigated in control (non-parachuting) and parachuting paratroops. RESULT: Significantly higher levels of serum hormones such as growth hormone, insulin, angiotonin 1, renin activities, as well as MDA and plasma TNF-alpha and HSP70 were observed in the parachuting group. CONCLUSION: Whether these changes can potentially serve as useful biomarkers to assess possible abnormal stress in parachutists and to evaluate the health condition and to select parachutists remains to be further studied.

Adolescent↗

PubMed1999

[Study of HSP70 gene upstream regulation element on expression efficiency of GST gene in M. smegmatis].

Four different expression vectors were constructed by cloning foreign gene which encode Schistosoma japonicum 26 kD antigen (Sj26GST) into Escherichia coli-Mycobacteria shuttle plasmid pBCG-2000 and investigated their expression efficiency in mycobacteria smegmatis. The plasmid which contains promoter of human mycobacterial tuberculosis heat shock protein 70 was firstly digested with Nco I and modified with two different ways to lead to two kinds of SD sequences, and ligated with Sj26GST encoding gene. Then, the DNA fragment contained HSP70 promoter and Sj26GST gene was obtained and cloned into E. coil-mycobacteria shuttle plasmid pBCG-2000, and finally four recombinant mycobacterial expression vectors that differenciated in SD sequence, orientation and copy number were selected. The expressed native recombinant Sj26GST(rSj26GST) was soluble and could be observed on SDS-PAGE about at the molecular weight of 26 kD obviously. Analysis with protein density scanning indicated: the expression efficiency that containing double-copy promoter-foreign gene vector was the highest and the expressed protein which was about 1.6 times than others was 28% of total protein of Mycobacteria smegmatis. The cloned direction and SD sequence had no significant effect on expression efficiency.

Animals↗

PubMed1998

Epidermal growth factor induction of the c-jun promoter by a Rac pathway.

The c-jun proto-oncogene encodes a transcription factor which is activated by mitogens both transcriptionally and by phosphorylation by Jun N-terminal kinase (JNK). We have investigated the cellular signalling pathways involved in epidermal growth factor (EGF) induction of the c-jun promoter. We find that two sequence elements, which bind ATF1 and MEF2D transcription factors, are required in HeLa cells, although they are not sufficient for maximal induction. Activated forms of Ras, RacI, Cdc42Hs, and MEKK increased expression of the c-jun promoter, while dominant negative forms of Ras, RacI, and MEK kinase (MEKK) inhibited EGF induction. These and previously published results suggest that EGF activates the c-jun promoter by a Ras-to-Rac-to-MEKK pathway. This pathway is similar to that used for posttranslational activation of c-jun by JNK.

Activating Transcription Factor 1↗

PubMed1998

[Effects of selenium polysaccharide and sodium selenite on blood selenium concentration and liver cytochrome P450 monooxygenase system in rat].

The effects of selenium polysaccharide and sodium selenite administered by single or repetitive intraperitoneal injection (i.p.) on blood selenium concentration, the activities of liver cytochrome P450, b5 as well as NAD(P)H cytochrome C reductase, glutathione S-transferase and glutathione were studied in rats. The biological effects of selenium polysaccharide and sodium selenite were also compared. The results indicated that the blood selenium concentration was increased rapidly and reached the peak in 2 hours followed by gradual decline after selenium polysaccharide and sodium selenite were i.p. injected at a dose of Se 0.6 mg/kg. The absorption and eliminating rates of Se from sodium selenite were faster than that from selenium polysaccharide. Administration of selenium polysaccharide and sodium selenite at a dose of 0.2 mg/kg by i.p. increased the blood selenium concentration to 2.6 and 2.1 times of those of control group, respectively, and the blood selenium concentration of selenium polysaccharide group was significantly higher than that of sodium selenite group (P < 0.05). The activities of liver cytochrome P450, b5 and GST were inhibited by selenium polysaccharide and sodium selenium in vivo and in vitro experiments. Those proteins were decreased to 57%, 70% and 62% of the control, respectively, by selenium polysaccharide which has particularly stronger effects on cytochrome P-450 monooxygenase system (P < 0.05). The two selenium compounds did not appear to affect the activity of NAD(P)H cytochrome C reductase. Both of the selenium polysaccharide and sodium selenite could enhance the activity of glutathion peroxidase significantly (P < 0.05).

Animals↗

PubMed1997

Characterization of human activating transcription factor 4, a transcriptional activator that interacts with multiple domains of cAMP-responsive element-binding protein (CREB)-binding protein.

We demonstrate that human activating transcription factor 4 (hATF4), a member of the activating transcription factor/cAMP-responsive element-binding protein (ATF/CREB) family of transcription factors, is a potent transcriptional activator in both mammalian cells and yeast. The N-terminal 113 amino acids of hATF4 activate transcription efficiently, and unexpectedly, the C-terminal bZip DNA binding domain of hATF4 also activates transcription, albeit weakly. Our results indicate that hATF4 interacts with several general transcription factors: TATA-binding protein, TFIIB, and the RAP30 subunit of TFIIF. In addition, hATF4 interacts with the coactivator CREB-binding protein (CBP) at four regions: 1) the KIX domain, 2) a region that contains the third zinc finger and the E1A-interacting domain, 3) a C-terminal region that contains the p160/SRC-1-interacting domain, and 4) the recently identified histone acetyltransferase domain. Interestingly, both the N-terminal and C-terminal regions of hATF4 interact with the above general transcription factors and CBP, providing a mechanistic explanation for their ability to activate transcription. Consistent with its role as a coactivator, CBP potentiates the ability of hATF4 to activate transcription. The potential significance of the interaction between hATF4 and multiple factors is discussed.

Activating Transcription Factor 4↗