Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.6.5.2 (NQO1)
6,196 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Deletion mutagenesis and transfection studies into hepatic (mouse hepatoma (Hepa-1) and human hepatoblastoma (Hep-G2)) and nonhepatic (HeLa) cells indicated that high levels of expression of the human NAD(P)H:quinone oxidoreductase gene in tumor cells and its induction by beta-naphthoflavone and 3-(2)-tert-butyl-4-hydroxyanisole are mediated by human antioxidant response element (hARE) located in the region between -470 and -445. The hARE, when attached to the thymidine kinase promoter and transfected into several mammalian cells, expressed high levels of the chloramphenicol acetyltransferase gene that was inducible by beta-naphthoflavone and 3-(2)-tert-butyl-4-hydroxyanisole. Nucleotide sequence analysis of the hARE revealed the presence of a recognition site for binding to the AP1 protein. Mutation of the AP1 binding site located within the hARE resulted in the loss of expression and induction upon transfection into various cell types. Band shift and competition assays with hARE and nuclear extracts from control and beta-naphthoflavone-treated Hepa-1, Hep-G2 and HeLa cells indicated specific interaction of regulatory protein(s) to the hARE. The supershift assays using antibodies against specific proteins of the AP1 family identified Jun-D and c-Fos as two members in the hARE-protein complex observed in band shift assays.
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PMID:Regulation of human NAD(P)H:quinone oxidoreductase gene. Role of AP1 binding site contained within human antioxidant response element. 840 91

Deletion mutagenesis in human NAD(P)H:Quinone Oxidoreductase (NQO1) gene and transfection studies into mammalian cells identified a segment of DNA designated as human Antioxidant Response Element (hARE) responsible for high basal expression in tumor cells and its induction by beta-naphthoflavone (beta-NF). The twenty four base pairs of the hARE contains an essential cis-element AP1 binding site and has been shown to bind to jun-D and c-fos proteins from mouse hepatoma (Hepa-1) nuclear extract. In the present report, we have identified jun-B as the third major protein in the hARE-Hepa-1 proteins complex observed in the band shift assays.
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PMID:Identification of jun-B as third member in human antioxidant response element-nuclear proteins complex. 144 67

NAD(P)H:quinone oxidoreductase1 (DT-diaphorase or NQO1) is a flavoprotein that promotes obligatory two-electron reduction of quinones, preventing their participation in redox cycling, oxidative stress, and neoplasia. NQO1 is ubiquitously expressed. However, a large amount of variation in NQO1 gene expression was noticed among various human tissues. NQO1 gene is upregulated in livers of hepatocarcinoma patients, and its expression is induced in response to a variety of compounds, including planar aromatic hydrocarbons, phenolic antioxidants/chemoprotectors, tumor promoters, and hydrogen peroxide. Deletion mutagenesis in the NQO1 gene promoter identified several cis-elements including antioxidant response element (ARE), xenobiotic response element, and AP2 element, which regulate the expression and induction of the NQO1 gene. Among these DNA elements, ARE is the most important cis-element required for high basal expression of the NQO1 gene in tumor tissues, as compared to the normal tissues of the same origin, and for its induction in response to xenobiotics and antioxidants. Nucleotide sequence analysis of the ARE indicated presence of three AP1/AP1-like elements and a GCA box. Mutational analysis indicated a requirement of two AP1/AP1-like elements arranged as inverse repeats at the interval of three base pairs for the ARE activity. The GCA box in the ARE was required for optimum basal and induced expression. ARE is a novel cis-element because a single AP1/AP1-like element did not stimulate gene expression in response to xenobiotics and antioxidants. Band shift and supershift assays identified Jun, Fos, and novel proteins in the hARE-nuclear protein complexes that mediate regulation of the NQO1 gene expression.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:NAD(P)H:quinone oxidoreductase1 (DT-diaphorase): expression, regulation, and role in cancer. 762 Feb 21

Antioxidant response elements (AREs) containing 12-O-tetradecanoylphorbol-13-acetate response element (TRE) (perfect AP1) and TRE-like (imperfect AP1) elements mediate high basal transcription of the NAD(P)H:quinone oxidoreductase1 (NQO1) and glutathione S-transferase Ya genes in tumor cells and its induction in response to xenobiotics and antioxidants. Mutations in the human NQO1 gene ARE (hARE) revealed the requirement for two TRE or TRE-like elements arranged in inverse orientation at the interval of three base pairs and a GC box for optimal expression and beta-naphthoflavone induction of the NQO1 gene. A single TRE element from the human collagenase gene failed to respond to beta-naphthoflavone. These results demonstrate that ARE (2 x TRE or TRE-like elements)-containing detoxifying enzyme genes and not genes that contain 1 x TRE are responsive to xenobiotics and antioxidants. Bandshift assays showed shifting of a complex of more or less similar mobility with hARE and TRE that could be competed by each other. Mutations in the 3'-TRE of the NQO1 gene hARE eliminated binding of nuclear proteins to the hARE and resulted in the loss of basal and induced expression, indicating that 3'-TRE is the most important element within the hARE. 5'-TRE-like element within the NQO1 gene hARE is required for xenobiotic response but may not bind to the nuclear proteins by itself. The GC box located immediately following the 3'-TRE is required for optimal expression and induction of the NQO1 gene. The comparison of AREs from several different genes indicated the requirement for specific arrangement and spacing of two TRE and TRE-like elements within the AREs.
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PMID:ARE- and TRE-mediated regulation of gene expression. Response to xenobiotics and antioxidants. 789 38

Human antioxidant-response element (hARE) containing two copies of the AP1/AP1-like elements arranged as inverse repeat is known to mediate basal and beta-naphthoflavone-induced transcription of the type 1 NAD(P)H:quinone oxidoreductase (NQO1) gene. Band-shift assays revealed that beta-naphthoflavone increased binding of nuclear proteins at the hARE. Super shift assays identified Jun-D and c-Fos proteins in the band-shift complexes observed with control and beta-naphthoflavone-treated Hepa-1 nuclear extracts. Hepa-1 cells stably transformed with hARE-tk-chloramphenicol acetyl transferase (CAT) recombinant plasmid were used to demonstrate that, in addition to beta-naphthoflavone, a variety of antioxidants, tumor promoters and hydrogen peroxide (H2O2) also increased expression of hARE-mediated CAT gene. beta-naphthoflavone induction of the CAT gene expression in Hepa-1 cells was found insensitive to inhibitors of protein kinase C and tyrosine kinases. However, binding of regulatory proteins at the hARE and the CAT gene expression in Hepa-1 cells were increased by dithiothreitol, 2-mercaptoethanol and diamide. Treatment of the Hepa-1 cells with N-ethylmaleimide reduced binding of proteins at the hARE and interfered with expression and beta-naphthoflavone induction of the CAT gene. These results suggested a role of sulfhydryl modification of hARE binding (Jun and Fos) proteins which mediate basal and induced expression of the NQO1 gene. We also report that in-vitro-translated products of the proto-oncogenes, Jun and Fos, bind to the hARE in band-shift assays. The incubation of Jun and Fos proteins with small amounts of nuclear extract from dimethylsulfoxide-treated (control) or beta-naphthoflavone treated Hepa-1 cells prior to band-shift assays increased the binding of Jun and Fos proteins to the hARE. Interestingly, the increase in binding of Jun and Fos proteins to the hARE was more prominent with beta-naphthoflavone-treated nuclear extract as compared to the control nuclear extract. In addition, incubation of control nuclear extract with beta-naphthoflavone, microsomes and NADPH increased the binding of Jun and Fos proteins to the hARE. Evidence from in vitro studies indicate the presence of unknown nuclear factor(s) that receive signals from metabolites of beta-naphthoflavone and modulate Jun and Fos binding to the AP1 site contained within the hARE.
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PMID:Human antioxidant-response-element-mediated regulation of type 1 NAD(P)H:quinone oxidoreductase gene expression. Effect of sulfhydryl modifying agents. 795 57

NAD(P)H:Quinone oxidoreductase1 (NQO1) is a flavoprotein which promotes obligatory two-electron reduction of quinones, preventing their participation in redox cycling, oxidative stress and neoplasia. High levels of NQO1 have been observed in several kinds of tumours including that of the liver, lung, colon and breast. Transcription of the NQO1 gene is increased in response to bifunctional [e.g. beta-naphthoflavone (beta-NF), 2,3,7,8,-tetrachlordibenzo-p-dioxin (dioxin)] and monofunctional [phenolic antioxidants/chemoprotectors e.g. 2(3)tert-butyl-4-hydroxy-anisole (BHA)] inducers. High basal expression of the NQO1 gene and its induction by beta-NF and BHA are mediated by 31 bp of the antioxidant response element (ARE) containing more than one copy of the AP1/AP1-like binding sites, Jun and Fos and other(s) as yet unknown regulatory proteins. The arrangement of AP1/AP1-like elements within a short region of DNA may be important for beta-NF and BHA response. The high basal expression of the NQO1 gene in several types of tumour tissues may be due to a high expression and/or modification of regulatory proteins that result from tumour formation. Signal transduction from beta-NF and BHA for increased expression of the NQO1 gene involve metabolism of beta-NF and generation of 'redox signals'. The sequence of events after generation of 'redox signals' leading to the modification/activation of regulatory proteins that bind to ARE and increase expression of the NQO1 gene are less clear. The possibilities include involvement of protein(s) which receive signals from beta-NF and BHA and modulate the Jun and Fos proteins for increased binding to the ARE element or increased activities of the transcriptional activation domains of the regulatory proteins. The modifications in the regulatory proteins may be reduction of a cysteine residue in the DNA binding domain and/or phosphorylation of the DNA binding/transcriptional activation domains. Further studies are required to identify the intermediary components in the signal transduction pathway to completely understand the mechanism of induction of the NQO1 gene expression in response to beta-NF and BHA. Dioxin induction of the NQO1 gene expression is mediated by XRE, an element best characterized in the case of the CYP1A1 gene.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Jun and Fos regulation of NAD(P)H: quinone oxidoreductase gene expression. 800 28

NAD(P)H:Quinone Oxidoreductase1 (NQO1) also known as DT-diaphorase is a flavoprotein that catalyzes the two-electron reduction of quinones, quinone imines and azo-dyes and thereby protects cells against mutagenicity and carcinogenicity resulting from free radicals and toxic oxygen metabolites generated by the one-electron reductions catalyzed by cytochromes P450 and other enzymes. High levels of NQO1 gene expression have been observed in liver, lung, colon and breast tumors as compared to normal tissues of the same origin. The transcription of the NQO1 gene is activated in response to exposure to bifunctional (e.g. beta-naphthoflavone (beta-NF), 2, 3, 7, 8 tetrachorodibenzo-p-dioxin (TCDD)) and monofunctional (phenolic antioxidants/chemoprotectors e.g. 2(3)-tert-butyl-4-hydroxy-anisole (BHA)) inducers. The high level of expression of the NQO1 gene and its induction by beta-NF and BHA require the presence of an AP1 binding site contained within the human Antioxidant Response Element (hARE) and are mediated by products of proto-oncogenes, Jun and Fos. Induction of NQO1 gene expression involves transfer of a redox signal from xenobiotics to unknown 'redox protein(s)' which in turn, modify the Jun and Fos proteins for greater affinity towards the AP1 site of the NQO1 gene and activates transcription. The expression and regulation of the NQO1 gene is complex as many additional cis-elements have been identified in the promoter region and is a subject of great future interest. In addition to established tumors, NQO1 gene expression is also increased in developing tumors, indicating a role in cellular defense during tumorigenesis. It has been proposed that low molecular weight substance(s) can diffuse from tumor cells into surrounding normal cells and activate the expression of the NQO1 gene. Purification and characterization of such substance(s) may provide important information in regard to the mechanism of activation of NQO1 gene expression and the role of increased NQO1 expression in tumor development. In view of the general consensus that NQO1 is over-expressed in tumor cells and the realization that NQO1 may either activate or detoxify xenobiotics, it is important to establish the role of NQO1 in the activation, and the detoxification of xenobiotics and drugs and in the intrinsic sensitivity of tumors to bioreductive alkylating aziridinyl benzoquinones such as diaziquone (AZQ), mitomycin C (MMC), and indoloquinone EO9, as well as to the dinitrophenyl aziridine, CB1954, and the benzotriazine-di-N-oxide, SR 4233.
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PMID:NAD(P)H:quinone oxidoreductase1 (DT-diaphorase) expression in normal and tumor tissues. 837 15

Twenty-four base pairs of the human antioxidant response element (hARE) are required for high basal transcription of the NAD(P)H:quinone oxidoreductase1 (NQO1) gene and its induction in response to xenobiotics and antioxidants. hARE is a unique cis-element that contains one perfect and one imperfect AP1 element arranged as inverse repeats separated by 3 bp, followed by a "GC" box. We report here that Jun, Fos, Fra, and Nrf nuclear transcription factors bind to the hARE. Overexpression of cDNA derived combinations of the nuclear proteins Jun and Fos or Jun and Fra1 repressed hARE-mediated chloramphenicol acetyltransferase (CAT) gene expression in transfected human hepatoblastoma (Hep-G2) cells. Further experiments suggested that this repression was due to overexpression of c-Fos and Fra1, but not due to Jun proteins. The Jun (c-Jun, Jun-B, and Jun-D) proteins in all the possible combinations were more or less ineffective in repression or upregulation of hARE-mediated gene expression. Interestingly, overexpression of Nrf1 and Nrf2 individually in Hep-G2 and monkey kidney (COS1) cells significantly increased CAT gene expression from reporter plasmid hARE-thymidine kinase-CAT in transfected cells that were inducible by beta-naphthoflavone and teri-butyl hydroquinone. These results indicated that hARE-mediated expression of the NQO1 gene and its induction by xenobiotics and antioxidants are mediated by Nrf1 and Nrf2. The hARE-mediated basal expression, however, is repressed by overexpression of c-Fos and Fra1.
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PMID:Nrf1 and Nrf2 positively and c-Fos and Fra1 negatively regulate the human antioxidant response element-mediated expression of NAD(P)H:quinone oxidoreductase1 gene. 896 64

Regulation of the basal and induced expression of detoxifying enzymes such as NAD(P)H:quinone oxidoreductasel (NQO1) and glutathione S-transferase (GST) by the antioxidant response element (ARE) is important for cellular protection against oxidative stress. The ARE contains AP1 and AP1-like elements and is known to bind to several leucine zipper proteins including c-Fos. Previous studies (Venugopal, R., and Jaiswal, A.K. (1996) Proc. NatL Acad. Sci. USA 93, 14960-14965) have shown that overexpression of c-Fos in transfected cells leads to repression of ARE-mediated gene expression. In the present report, we used c-Fos-/- mice and investigated the physiological (in vivo) role of c-Fos in repression of the NQO1 and GST genes expression. The analysis of enzyme activity levels showed significant increases in NQO1 and GST activities in several tissues of c-Fos-/- mice, as compared with wild type (c-Fos+/+) mice. The increases in enzyme activities were supported by Wetern analysis of respective proteins. Western analyses showed significant increases in the expression of NQO1 in kidney, liver and skin tissues of c-Fos-/- mice, as compared with wild type (c-Fos+/+) controls. Western analyses also demonstrated an increased expression of the GST Ya gene in kidney and liver tissues of the c-Fos-/-mice. These results confirm a negative (repressive) role for c-Fos in the expression of NQO1, GST Ya, and other detoxifying enzyme genes.
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PMID:Disruption of c-Fos leads to increased expression of NAD(P)H:quinone oxidoreductase1 and glutathione S-transferase. 991 19

DT-diaphorase is a two-electron reducing enzyme that is an important detoxifying enzyme and activator of bioreductive antitumor agents. Expression of the DT-diaphorase gene, NQO1, appears to be transcriptionally regulated, and the gene is induced by a wide variety of compounds. We showed that 1,2-dithiole-3-thione can selectively increase DT-diaphorase activity in human and murine tumors, and that this enhanced the antitumor activity of bioreductive antitumor agents. However, we found that DT-diaphorase activity was not increased in some human tumor cell lines after treatment with the inducer, and this appeared to be due to a lack of increased transcription. To determine if this lack of increased transcription was due to a mutation in the promoter region of the NQO1 gene in these cells, we sequenced approximately 2000 bases of the NQO1 promoter region from non-induced cells and compared these with sequences from human HT29 colon cancer cells, which showed significant increases in NQO1 transcription, and the sequence reported for human liver cells in Genbank. Sequence analysis showed no changes in the sequences of the major transcriptional elements, XRE, CAT box, ARE, AP1 site or AP2 site, in the tumor cells compared with the Genbank sequences. The only major change was a deletion of a 20 base repeat region approximately 400 bases 5' to the XRE element in all the cells, including the HT29 cells, compared with the sequence reported in Genbank. There were also several insertions of a single base in various parts of the sequences which occurred in most, or all, of the cell lines compared with the reported sequence, and a small number of single base changes, insertions or deletions that occurred in a single cell line. However, these changes did not appear to correlate with differences in induced transcription of the NQO1 gene. These results suggest that the differences in transcription of the NQO1 gene after treatment with DT-diaphorase inducers was not due to alterations in the promoter region of the gene.
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PMID:Lack of NQO1 induction in human tumor cells is not due to changes in the promoter region of the gene. 1189 33


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