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

---

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

Monkey kidney COS1 cells transiently transfected with plasmids pMT2-cytochrome P450 1A1 (CYP1A1), pMT2-cytochrome P450 reductase (P450 reductase), and pMT2-NAD(P)H:quinone oxidoreductase1 (NQO1 or DT diaphorase), individually or in combination, expressed significantly elevated levels of the respective enzyme(s). The transfected cells were homogenized to break cell membranes without affecting the nuclei and incubated with benzo[a]pyrene (BP) to determine the role of cDNA-encoded enzymes in metabolic activation and/or detoxification of BP. These studies were performed by measuring the capacity of the transfected cells to form DNA adducts as determined by 32P postlabeling and protein adduct detection. Cotransfection of the COS1 cells with cDNAs encoding CYP1A1 and P450 reductase resulted in eight distinct BP-DNA adducts. Inclusion of cDNA encoding NQO1 along with CYP1A1 and P450 reductase in transfection reduced the number of DNA adducts to six. The two lost DNA adducts were specifically eliminated due to the presence of cDNA-derived NQO1 activity. Subsequent experiments with BP-1,6-quinone, BP-3,6-quinone, and BP-6,12-quinone identified these two adducts as those of BP quinones. In an in vitro system, BP-3,6-quinone produced two adducts with deoxyguanosine (dG) but not with dA, dC, and dT. Furthermore, the positions of BP-3,6-quinone-dG adducts on TLC plate correspond to those that are prevented by cDNA-derived NQO1, thus identifying these adducts as BP quinones of dG. In addition, NQO1 reduced the amount of protein-BP adducts generated by CYP1A1 and P450 reductase into transfected COS1 cells. These results show that semiquinones can directly bind to DNA and demonstrate that NQO1 activity can specifically reduce the binding of quinone metabolites of BP generated by CYP1A1 and P450 reductase to DNA and protein.
...
PMID:NAD(P)H:quinone oxidoreductase1 (DT diaphorase) specifically prevents the formation of benzo[a]pyrene quinone-DNA adducts generated by cytochrome P4501A1 and P450 reductase. 807 96

Human NAD(P)H:quinone oxidoreductase2 (NQO2) gene, 1336 base pairs (bp) of the 5'-flanking region and 165 bp of the 3'-flanking region, have been sequenced. NQO2 gene is 20 kilobase pairs in length and have seven exons interrupted by six introns as compared to the previously cloned NQO1 gene which contains six exons. 187 bp of the first exon in the NQO2 gene are noncoding and are absent in the NQO1 gene. 92 bp of the second exon in the NQO2 gene corresponded to the first exon of the NQO1 gene and so on. The sizes and nucleotide sequences of exons 3-6 are highly conserved between NQO2 and NQO1 genes. The last exon in the NQO2 gene is 1603 bp shorter than the last exon of the NQO1 gene and encodes for 58 amino acids as compared to 101 amino acids encoded by the NQO1 gene. This makes NQO2 protein 43 amino acids shorter than the NQO1 protein. The high degree of conservation between NQO2 and NQO1 gene organization and sequence confirmed that NQO2 gene encodes for a second member of the NQO gene family in human. Nucleotide sequence analysis of the 5'-flanking region of the NQO2 gene revealed presence of four SP1 binding sites at positions -214, -170, -106, and -75, a single copy of the antioxidant response element (ARE) at nucleotide -936, and three copies of xenobiotic response element (XRE) at positions -708, -557, and -51. ARE and XRE elements have previously been found in the promoters of the NQO1 and glutathione S-transferase Ya subunit genes and mediate increases in their expression in response to polycyclic aromatic compounds, phenolic antioxidants, and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), respectively. The NQO2 cDNA-derived protein in monkey kidney COS1 cells efficiently catalyzed nitroreduction of anti-tumor compound CB10-200, an analog of nitrophenylaziridine. Northern blot analysis indicates that NQO2 gene is expressed in human heart, brain, lung, liver, and skeletal muscle but does not express in placenta. In contrast, the NQO1 gene was expressed in all human tissues. Large variations were noticed for expression of the NQO2 and NQO1 genes among various tissues, 1336 bp of the 5'-flanking region of the NQO2 gene containing ARE and XRE was found sufficient to increase expression of the CAT gene in response to beta-naphthoflavone and tCDD in transfected human hepatoblastoma (Hep-G2) cells.
...
PMID:Human NAD(P)H:quinone oxidoreductase2. Gene structure, activity, and tissue-specific expression. 818 56

In conclusion, recent work has highlighted the fact that NSCLCs have elevated levels of NQO1 activity and that such an increase represents an excellent target for therapeutic exploitation. The 5-year survival rate seen with lung cancer is dismal and there is a high number of cancer deaths associated with this disease each year. This renders the design of molecules that can be activated by NQO1 (such as MeDZQ or CB 10-200) an extremely important and urgent issue.
...
PMID:Mitomycin C. 831 13

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.
...
PMID:NAD(P)H:quinone oxidoreductase1 (DT-diaphorase) expression in normal and tumor tissues. 837 15

In our previous papers, seven structural genes (NQO1-7) of the energy-transducing NADH-quinone (Q) oxidoreductase of Paracoccus denitrificans were characterized [Xu, X., Matsuno-Yagi, A., & Yagi, T. (1991a) Biochemistry 30, 8678-8684; (1991b) Biochemistry 30, 6422-6428; (1992a) Biochemistry 31, 6925-6932; (1992b) Arch. Biochem. Biophys. 296, 40-48]. This paper reports the identification, cloning, and sequencing of seven additional structural genes in the same gene cluster (P. denitrificans enzyme complex). These seven genes, designated NQO8-14, are composed of 1038, 492, 603, 306, 2112, 1542, and 1500 base pairs, respectively. The polypeptides encoded by the NQO8-14 genes are homologous, respectively, to the ND1 product, the 23-kDa polypeptide, and the ND6, ND4L, ND5, ND4, and ND2 products of the bovine NADH-Q oxidoreductase. The order of the 14 structural genes of the Paracoccus energy-transducing NADH-Q oxidoreductase in the gene cluster is NQ07, NQO6, NQO5, NQO2, NQO1, NQO3, NQO8, NQO9, NQO10, NQO11, NQO12, NQO13, and NQO14. Downstream from the NQO14 gene an open reading frame (designated URF240) was detected which encodes a predicted polypeptide homologous to the biotin [acetyl-CoA-carboxylase] ligase of Escherichia coli. In addition, a putative terminal sequence motif was observed downstream of the NQO14 gene, suggesting that the structural gene NQO14 is the 3'-terminal gene of the Paracoccus NADH-Q oxidoreductase gene cluster. Nucleotide sequencing of the entire gene cluster revealed the presence of three unidentified reading frames: one between the NQO3 and NQO8 genes and other two between the NQO9 and NQO10 genes. These are designated URF4, URF5, and URF6 and are composed of 768, 393, and 405 base pairs, respectively. The possible functions of the putative proteins encoded by URF5 and URF6 are discussed.
...
PMID:DNA sequencing of the seven remaining structural genes of the gene cluster encoding the energy-transducing NADH-quinone oxidoreductase of Paracoccus denitrificans. 842

The enzyme NAD(P)H:quinone oxidoreductase (NQO1) catalyses bioreduction and bioactivation reactions. A mutation in the NQO1 gene had previously been demonstrated in a cancer cell line with reduced NQO1 activity. In this study, several regions of the NQO1 locus were examined for constitutional variation at the DNA level. The previously described mutation in exon 6 was detected by the single-strand conformation polymorphism technique. This was confirmed by sequencing to result from a C-->T substitution. Genotype analysis in the Centre d'Etude Polymorphisme Humain (CEPH) reference panel revealed two alleles with frequencies of 0.87 and 0.13 and demonstrated Mendelian transmission. Genotype distributions were consistent with Hardy-Weinberg equilibrium. Linkage analysis mapped the gene locus to chromosome 16q. NQO1 was felt to be a candidate gene for the susceptibility to lung cancer, given its potential role in protection against carcinogenic compounds. The frequency of NQO1 variants was examined in 150 lung cancer cases and in two reference populations. The allele distribution in CEPH parent controls was significantly different from cases (chi 2 = 5.52, p = 0.019), but no difference was noted between cases and a healthy local reference population. When the local reference distribution was stratified on smoking status, a significant difference was observed (chi 2 = 3.88, p = 0.048).(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Identification of an NAD(P)H:quinone oxidoreductase polymorphism and its association with lung cancer and smoking. 852 66

NAD(P)H:quinone oxidoreductase 1 (NQO1) is a flavoprotein that catalyzes two-electron reduction and detoxification of quinones. We have shown previously that twenty-four base pairs of the human Antioxidant Response Element (hARE) mediate basal and xenobiotic-induced expression of the NQO1 gene [Li and Jaiswal, J Biol Chem 267: 15097-15104, 1992]. In the present report, we have characterized a second cis-element, AP-2, at nucleotide position -157 of the human NQO1 gene promotor that regulates basal and cAMP-induced transcription of the NQO1 gene. The NQO1 gene AP-2 mediated expression of the chloramphenicol acetyl transferase (CAT) gene and the binding of nuclear proteins to the AP-2 element were observed in HeLa (AP-2 positive) cells but not in human hepatoblastoma Hep-G2 (AP-2 deficient) cells, indicating the involvement of transcription factors AP-2 in the regulation of NQO1 gene expression. Affinity purification of nuclear protein that binds to the NQO1 gene AP-2 DNA element and western analysis revealed that AP-2 indeed binds to the NQO1 gene AP-2 element and regulates its expression HeLa cells. The involvement of AP-2 in the regulation of NQO1 gene expression was confirmed by the observation that cDNA-derived AP-2 protein in Hep-G2 cells increased in NQO1 gene AP-2 but not mutant AP-2 mediated expression of CAT gene in Hep-G2 cells.
...
PMID:AP-2-mediated regulation of human NAD(P)H: quinone oxidoreductase 1 (NQO1) gene expression. 860 72

This study reports the expression of the flavoprotein (FP) subcomplex of the proton-translocating NADH-quinone oxidoreductase (NDH-1) from Paracoccus denitrificans, which is composed of the NQO1 (50 kDa) and the NQO2 (25 kDa) subunits. The two subunits are co-expressed in Escherichia coli using a double expression plasmid system. The expressed subunits form a water-soluble heterodimer complex with 1:1 stoichiometry. The expressed complex contained one [2Fe 2S] cluster but almost no FMN or [4Fe 4S] cluster. The two latter prosthetic groups could be partially reconstituted with FMN, Na2S, and (NH4)2Fe(SO4)2 in vitro under anaerobic conditions. The reconstituted FP subcomplex showed EPR signals from two distinct species of iron-sulfur cluster. One resonance transition originates from a [2Fe-2S] cluster with g values of gx,y,z = 1.92, 1.95, and 2.00 and slow spin relaxation, which was tentatively assigned to the cluster N1a. These EPR properties are very similar to those reported for the NQO2 subunit expressed alone (Yano, T., Sled', V. D., Ohnishi, T., and Yagi, T. (1994) Biochemistry 33, 494-499). The other originates from a [4Fe 4S] cluster with g values of gx,y, z = 1.87, 1.94, and 2.04 and fast relaxing behavior, which are reminiscent of the cluster N3 in the membrane bound enzyme complex. After reconstitution with FMN, the FP subcomplex catalyzed electron transfer from NADH and from deamino-NADH to a variety of electron acceptors. The enzymatic properties of the FP subcomplex, reconstituted with FMN and iron-sulfur, correspond to those of the isolated P. denitrificans NADH-dehydrogenase complex.
...
PMID:Expression and characterization of the flavoprotein subcomplex composed of 50-kDa (NQO1) and 25-kDa (NQO2) subunits of the proton-translocating NADH-quinone oxidoreductase of Paracoccus denitrificans. 862 64

The upstream region of the human NAD(P)H:quinone oxidoreductase (NQO1) gene contains a functional antioxidant responsive element (ARE) and an overlapping 12-O-tetradecanoyl-phorbol-13-acetate responsive element (TRE), with the sequence TGACTCAGCA. We show that the ARE (TGACNNNGCA) is required for induction by redox cycling phenolics (p-benzoquinone, catechol and hydroquinone), which are monofunctional inducers and induce NQO1 without the requirement for activation by cytochrome P-450. The TRE (TGACTCA) is involved only in basal expression. A plasmid containing overlapping ARE-TRE (TGACTCAGCA) sequences (-587 to -379) from the NAD(P)H:quinone oxidoreductase gene was transiently transfected into Hep G2 cells. In the absence of inducers, basal expression was 4-fold higher than in F9 cells (which lack AP-1 activity). Using subcloned oligonucleotides containing the ARE-TRE sequence (-473 to -440), the ARE sequence alone (TCA changed to GAC) and the TRE sequence alone (GC changed to TA), the basal level of expression was in the order: TRE > TRE-ARE > ARE in Hep G2 cells. Using F9 cells, basal expression was detected using the combination ARE-TRE sequence or the ARE, but not the TRE alone, p-Benzoquinone, catechol and hydroquinone, but not resorcinol, induced gene expression in both Hep G2 and F9 cells via the ARE-TRE and ARE sequences, but the TRE sequence did not contribute to this induction. We therefore conclude that induction of human NAD(P)H:quinone oxidoreductase by monofunctional inducers is via the ARE and not the TRE, and that the induction is mediated by proteins other than Fos and Jun.
...
PMID:Transcriptional regulation of the human NAD(P)H:quinone oxidoreductase (NQO1) gene by monofunctional inducers. 865 59

Mitomycin C (MMC), a known cytotoxic agent, requires cellular enzyme-mediated activation for effective antitumor activity. To study the bioreductive enzymes responsible for MMC activation in tumor cells, we examined the enzyme activities of DT-diaphorase (DTD) and NADPH:cytochrome P-450 reductase in 13 colon and gastric carcinoma cell lines and then compared these activities to the respective cellular MMC sensitivity. We found that cell lines with nonexistent or marginal DTD activity, such as St-4 and MKN7, showed resistance to MMC, in comparison to cell lines with DTD activity ranging from 210 to 1420 nmol/min/mg protein. No correlation was found between NADPH:cytochrome P-450 reductase activity and MMC sensitivity in these cell lines. To confirm the role of DTD in cellular MMC sensitivity, we constructed an expression vector containing NQO1, a gene that codes for DTD, and transfected the vector into St-4 cells expressing no DTD activity. Several transfectant clones with DTD activity from 144 to 2085 nmol/min/mg protein were obtained. All of the transfectants showed 5-10-fold higher sensitivity to MMC compared to the parental St-4 cells. Consistent with the MMC sensitivity, we also found that MMC-DNA adduct was formed more extensively in the NQO1 transfectants than in the St-4 cells. These results indicate that DTD activity is required for effective cytotoxicity of MMC in colon and gastric carcinoma cells.
...
PMID:DT-diaphorase as a critical determinant of sensitivity to mitomycin C in human colon and gastric carcinoma cell lines. 866 20


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---