Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:5.99.1.2 (topoisomerase)
 9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using isolated rat liver mitochondria, which have previously been shown to carry out true replicative DNA synthesis, we have obtained results which are in accord with the presence and functioning of a DNA gyrase in this organelle. The effects of the Escherichia coli DNA gyrase inhibitors, novobiocin, coumermycin, nalidixic acid and oxolinic acid, upon mtDNA replication suggest the involvement of the putative mitochondrial enzyme in various aspects of this process. First, the preferential inhibition of [3H]dATP incorporation into highly supercoiled DNA together with the appearance of labeled, relaxed DNA are consistent with the involvement of a gyrase in the process of generating negative supercoils in mature mtDNA. Second, the overall depression of incorporation of labeled dATP into mtDNA, including the reduction of radioactivity incorporated into replicative intermediates, suggests a 'swivelase' role for the putative gyrase, and this hypothesis is further supported by results obtained on sucrose gradient centrifugation of heat-denatured, D-loop mtDNA. Here, the synthesis of the completed clean circles is inhibited while 9 S initiator strand synthesis is not, suggesting that chain elongation is blocked by the gyrase inhibitors.
Biochim Biophys Acta 1983 Sep 09
PMID:The effect of bacterial DNA gyrase inhibitors on DNA synthesis in mammalian mitochondria. 630 36

Evidence is presented that the topoisomerase inhibitors novobiocin and coumermycin inhibit the production of double-strand breaks in mouse mastocytoma cell nuclear DNA by the anticancer drug 4'[(9-acridinyl)amino]-methanesulphon-m-anisidide (mAMSA). Novobiocin did not inhibit resealing of DNA breaks induced by mAMSA. It is suggested that mAMSA intercalation into DNA induces the action of a type II topoisomerase. mAMSA and oAMSA were equally effective in breaking the DNA in isolated nuclei.
FEBS Lett 1983 Sep 05
PMID:Evidence that mAMSA induces topoisomerase action. 630 76

The effect on DNA repair of several inhibitors of DNA synthesis has been investigated in CHO cells. Three assays were employed following ultraviolet irradiation of G1 cells: unscheduled DNA synthesis, removal of antibody binding sites and alkaline elution. Cytosine arabinoside and aphidicolin were found to reduce unscheduled DNA synthesis in a dose-dependent manner without affecting the removal of antibody-binding sites. Strand rejoining was also inhibited. These results are consistent with the hypothesis that inhibition is due to premature chain termination during repair synthesis some time after excision of the lesion. Conversely, inhibition of unscheduled DNA synthesis by novobiocin is paralleled by inhibition of excision of the lesion. However, no inhibition of incision was apparent. Since nalidixic acid, an inhibitor of topoisomerase II, did not inhibit excision, it is unlikely that the primary site of action of novobiocin is this topoisomerase. The possibility that a second topoisomerase and/or a polymerase are affected is discussed in the light of previously published data.
Biochim Biophys Acta 1983 Sep 09
PMID:The effect of various inhibitors of DNA synthesis on the repair of DNA photoproducts. 641 Nov 22

A histone-like protein (H) from Escherichia coli has been purified to more than 98% homogeneity by using its capacity to inhibit DNA functions. H protein behaves as a dimer of 28,000-dalton subunits. The histone H2A-like properties of H protein are: (i) binding to DNA at a stoichiometry of 1 H protein dimer per 75 bases; (ii) abundance of about 30,000 molecules per cell, sufficient to bind about 20% of the chromosome; (iii) limiting digestion of double-stranded DNA by micrococcal nuclease; (iv) reannealing of complementary single-stranded DNA; (v) amino acid composition resembling that of eukaryotic histone H2A; (vi) neutralization of H protein by antibody specific for H2A; (vii) heat stability; and (viii) acid solubility. The capacity of H protein to bind DNA prevents its template or substrate functions n several reactions in vitro: DNA synthesis by several polymerases; transcription by RNA polymerase; DNA topoisomerase activity; and DNA-dependent ATP hydrolysis by rep protein, dnaB protein, or protein n'. Together with other histone-like proteins of E. coli, H protein may organize the E. coli chromosome into nucleosomes, such as in eukaryotic chromatin.
Proc Natl Acad Sci U S A 1980 Sep
PMID:Novel histone H2A-like protein of escherichia coli. 700 71

NK 611 is a new semisynthetic analogue of etoposide, which presumably also acts through inhibition of topoisomerase II, and has been found to be more potent against several cancer cell lines in vitro than etoposide. The objectives of our study were to determine the activity of NK 611 against freshly explanted clonogenic cells from human tumours and compare this agent with etoposide and other clinically useful agents. After exposure for 1 h in 45 evaluable tumour specimens, NK 611 showed clear concentration-dependent antitumour activity. At 51 microM, 49% of specimens were markedly inhibited. Using a long-term (21-28 day) exposure at 6.8 microM, 58% of 50 evaluable specimens were profoundly inhibited. At equimolar concentrations, NK 611 was as active as etoposide. Across all tumour types studied, NK 611 was as active as vinblastine, bleomycin, doxorubicin, 5-fluorouracil, mitomycin-C and cisplatin. Our results showed cross resistance to etoposide in the majority of specimens. Activity of NK 611 was greater with long-term exposure than with short-term exposure indicating schedule dependency. We conclude that NK 611 has a wide spectrum of in vitro antitumour activity. Since preliminary clinical information suggests that this drug is well tolerated at high doses, further development of this agent in Phase II trials with multiple dosing schedules is warranted.
Eur J Cancer 1995 Sep
PMID:Activity of NK 611, a new epipodophyllotoxin derivative, against colony forming units from freshly explanted human tumours in vitro. 748 24

Cytokine stimulation of human umbilical vein endothelial cells (HUVE) induces surface expression of the adhesion molecules vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and endothelial leukocyte adhesion molecule-1 (E-selectin). We previously found that induction of adhesion molecule expression in HUVE is regulated, at least in part, by protein kinase C (PKC) activation, although this is not associated with the expected translocation of PKC from the cytosolic to the particulate fraction. We therefore investigated potential nuclear targets for PKC. Topoisomerase II is localized to the nuclear matrix and has been shown to be phosphorylated, both in vitro and in vivo, by PKC. In HUVE, the topoisomerase II selective inhibitors novobiocin, nalidixic acid, and etoposide prevented cytokine-induced VCAM-1 surface expression, but not E-selectin or ICAM-1 surface expression. Similarly, novobiocin and nalidixic acid reduced the accumulation of VCAM-1 mRNA in response to tumor necrosis factor-alpha treatment of HUVE. The inhibitory effect of the topoisomerase II inhibitors on VCAM-1 expression was not due to non-specific toxicity, as protein synthesis, measured by trichloroacetic acid precipitation of 35S-methionine labeled proteins, and transcription, determined by beta-actin mRNA levels, were not decreased. In contrast to the observed reduction of VCAM-1 mRNA accumulation and surface protein expression, inhibition of topoisomerase II activity enhanced E-selectin mRNA accumulation and surface protein expression in response to tumor necrosis factor-alpha stimulation of HUVE. This work demonstrates that topoisomerase II activity may differentially regulate the expression of adhesion molecules on HUVE.
Cell Adhes Commun 1993 Sep
PMID:Inhibitors of topoisomerase II prevent cytokine-induced expression of vascular cell adhesion molecule-1, while augmenting the expression of endothelial leukocyte adhesion molecule-1 on human umbilical vein endothelial cells. 752 51

We have established the first homologous cell-free DNA replication system for a papillomavirus. The replication of the human papillomavirus type 11 (HPV-11) origin was achieved by using human 293 cell extracts supplemented with the HPV-11 E1 and E2 proteins purified from insect cells infected with recombinant baculoviruses. Efficient replication depends on the HPV-11 origin, the HPV-11 E1 and E2 proteins, as well as human DNA polymerase alpha, delta, replication protein A, topoisomerase I, and topoisomerase II. High concentrations of E1 protein also promoted a low level of origin-independent replication which was suppressed by the addition of the E2 protein, whereas E2 protein stimulated origin-dependent replication. We also show that an intact E2 protein binding site was absolutely necessary for origin activity, as a strong HPV-11 origin was rendered inactive when one half-site of each of the three E2 binding sites was mutated. In contrast, there was only a relatively small reduction in this mutant origin activity when the cell extracts were supplemented with the bovine papillomavirus type 1 (BPV-1) proteins. These results suggest that the HPV-11 E2 protein plays a primary role in HPV origin recognition. Furthermore, unlike transient replication in which HPV-11 and BPV-1 viral proteins promote efficient replication of homologous and heterologous origins, efficient cell-free replication took place only with the homologous combinations.
J Biol Chem 1994 Sep 30
PMID:Cell-free replication of the human papillomavirus DNA with homologous viral E1 and E2 proteins and human cell extracts. 752 66

We describe here a simple and easily manipulatable Escherichia coli-based genetic system that permits us to identify bacterial gene products that modulate the sensitivity of bacteria to tumoricidal agents, such as DMP 840, a bisnaphthalimide drug. To the extent that the action of these agents is conserved, these studies may expand our understanding agents is conserved, these studies may expand our understanding of how the agents work in mammalian cells. The approach briefly is to use a library of E. coli genes that are overexpressed in a high copy number vector to select bacterial clones that are resistant to the cytotoxic effects of drugs. AtolC bacterial mutant is used to maximize permeability of cells to hydrophobic organic molecules. By using DMP 840 to model the system, we have identified two genes, designated mdaA and mdaB, that impart resistance to DMP 840 when they are expressed at elevated levels. mdaB maps to E. coli map coordinate 66, is located between the parE and parC genes, and encodes a protein of 22 kDa. mdaA maps to E. coli map coordinate 18, is located adjacent to the glutaredoxin (grx) gene, and encodes a protein of 24 kDa. Specific and regulatable overproduction of both of these proteins correlates with DMP 840 resistance. Overproduction of the MdaB protein also imparts resistance to two mammalian topoisomerase inhibitors, Adriamycin and etoposide. In contrast, overproduction of the MdaA protein produces resistance only to Adriamycin. Based on its drug-resistance properties and its location between genes that encode the two subunits of the bacterial topoisomerase IV, we suggest that mdaB acts by modulating topoisomerase IV activity. The location of the mdaA gene adjacent to grx suggests it acts by a drug detoxification mechanism.
Proc Natl Acad Sci U S A 1995 Sep 12
PMID:A general genetic approach in Escherichia coli for determining the mechanism(s) of action of tumoricidal agents: application to DMP 840, a tumoricidal agent. 756 50

A series of twelve structurally related bisdioxopiperazines that included ICRF-187 (dexrazoxane), ICRF-159 (razoxane), ICRF-193, and ICRF-154 were examined both for their ability to inhibit the growth of Chinese hamster ovary (CHO) cells and their ability to inhibit the catalytic activity of mammalian DNA topoisomerase II. The bisdioxopiperazines exhibited a wide range in both growth inhibitory effects (30,000-fold), and in their ability to inhibit the catalytic activity of topoisomerase II (150-fold). The cytotoxicity of the bisdioxopiperazines toward CHO cells was highly correlated (correlation coefficient r = 0.86, P = 0.0003) with their inhibition of the catalytic activity of DNA topoisomerase II. This result strongly suggests that DNA topoisomerase II is the functional target of the bisdioxopiperazines. The stereoisomers (+)-ICRF-187 and (-)-ICRF-186 were observed to be equally cytotoxic and equally inhibitory toward DNA topoisomerase II. This result indicates that the bisdioxopiperazine binding site on DNA topoisomerase II is large enough or flexible enough to accommodate either form of the drug. The strongly metal-ion binding fully rings-opened hydrolysis product of ICRF-187, ADR-925, demonstrated no measurable inhibitory activity toward DNA topoisomerase II or cytotoxicity toward CHO cells.
Biochem Pharmacol 1995 Sep 28
PMID:A QSAR study comparing the cytotoxicity and DNA topoisomerase II inhibitory effects of bisdioxopiperazine analogs of ICRF-187 (dexrazoxane). 757 79

We have used two different approaches to study the consequences of NAD/poly(ADP-ribose) deficiency on p53 expression and its activity in V79-derived cell lines. In the first approach, we have used two cell lines that are deficient in poly(ADP-ribose) (pADPR) synthesis because of deficiency in the enzyme poly(ADP-ribose) polymerase (PARP). In a second approach, we have used a cell line that is deficient in NAD/pADPR metabolism due to unavailability of NAD, the substrate for PARP. These NAD/PARP-deficient cell lines exhibit a significant reduction in both baseline p53 expression and its activity compared to their parental V79 cells. Furthermore, etoposide, a topoisomerase II inhibitor that was shown to cause an increase in p53 expression and subsequent apoptosis in V79 cells, failed to produce any significant increase in p53 expression or apoptotic DNA fragmentation in NAD/PARP-deficient cell lines. Thus, our studies suggest that NAD/pADPR synthesis may be involved in the regulation of p53 and its dependent pathways.
Cancer Res 1995 Sep 01
PMID:Involvement of NAD-poly(ADP-ribose) metabolism in p53 regulation and its consequences. 764 Nov 78


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