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:5.99.1.3 (topoisomerase)
9,911 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

DNA in bacterial cells is under negative superhelical tension, a feature that facilitates many of the activities of DNA. Supercoiling is introduced enzymatically by DNA gyrase, and the accumulation of excessively high levels is prevented by the relaxing activity of DNA topoisomerase I. Among the factors likely to influence supercoiling are topoisomerase gene expression, the ratio of ATP to ADP concentration, and processes such as transcription that unwind DNA and then translocate along it.
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PMID:Bacterial topoisomerases and the control of DNA supercoiling. 196 69

Short-term (2-6 h) exposure of human promyelocytic HL-60 cell cultures to the DNA topoisomerase I inhibitor camptothecin (0.05-0.5 microgram/ml) or to the topoisomerase II inhibitor, teniposide (VM-26; 0.3-3.0 micrograms/ml) or 4'-(9-acridinylamino)methanesulfon-m-anisidide (amsacrine; 0.8 microgram/ml) triggered rapid degradation of DNA specifically in S-phase cells. As a result of the selective death of S-phase cells, only G1 cells remained in these cultures. On the other hand, mitoxantrone (0.02-0.4 microgram/ml) or doxorubicin (adriamycin; 0.4-10.0 micrograms/ml) did not induce DNA degradation in S phase but arrested HL-60 cells in S and G2 phases. In contrast to HL-60 cells, human lymphocytic leukemic MOLT-4 cells responded to all of these drugs (camptothecin, teniposide, amsacrine, mitoxantrone, and adriamycin) at all concentrations tested, invariably by being arrested in G2 and S phases and also by entering a higher DNA ploidy cycle. The data illustrate the differences in the sensitivity of S-phase cells in myelogenous versus lymphocytic leukemic lines to both DNA topoisomerase I and II inhibitors and emphasize the tissue (leukemia type)-specific factors that modulate the cytostatic and cytotoxic effects of these inhibitors. The qualitatively different response of HL-60 cells to camptothecin, teniposide, or amsacrine (by rapidly triggered DNA degradation in S phase) as compared to mitoxantrone or adriamycin (by cell arrest in G2 and S) suggests that, despite the generally assumed common mode of action attributed to these drugs (i.e., via stabilization of the cleavable DNA-topoisomerase complexes), there are significant differences in the mechanisms by which they exert cytostatic/cytotoxic effects.
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PMID:Camptothecin, teniposide, or 4'-(9-acridinylamino)-3-methanesulfon-m-anisidide, but not mitoxantrone or doxorubicin, induces degradation of nuclear DNA in the S phase of HL-60 cells. 199 59

There is multiple evidence linking the inhibition of DNA topoisomerases I and II with the cytotoxic effects of antitumor drugs such as camptothecin and the DNA intercalators, 4-(9-acridinylamino)methanesulfon-m-anisidine) (mAMSA) and Adriamycin. We have assessed the effect of the DNA intercalator 3-nitrobenzothiazolo(3,2-a)quinolinium (NBQ) on the DNA topoisomerase I and II activities. NBQ has no effect on the activity of purified topoisomerase I, whereas it induced purified topoisomerase II binding to DNA without inducing DNA scission. Above 30 microM, NBQ stimulated formation of double- and single-strand breaks mediated by topoisomerase II in plasmid DNA. Using the alkaline elution technique we determined that NBQ induced single-strand and DNA-protein-associated breaks in the human promyelocytic leukemia cell line HL-60. At sublethal concentrations (less than or equal to 1 microM), NBQ induce HL-60 cells to differentiate. Topoisomerase II-mediated DNA cleavage induced by mAMSA was substantially reduced in NBQ-differentiated cells. Our data suggest that topoisomerase II could play a major role in the biological activity of NBQ in vivo.
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PMID:Interaction of DNA intercalator 3-nitrobenzothiazolo (3,2-a)quinolinium with DNA topoisomerases: a possible-mechanism for its biological activity. 215 51

Fostriecin causes a delayed inhibition of replicative DNA synthesis in human cells, consistent with a role for DNA topoisomerase II (its target enzyme) at a late stage in replication. Fostriecin does not inhibit UV-induced excision repair. The less specific inhibitor novobiocin blocks repair in permeabilised cells given a low dose of UV, presumably through a mechanism other than the inhibition of topoisomerase II. Its effect cannot be accounted for by a depletion of the ATP required for incision. Camptothecin, an inhibitor of DNA topoisomerase I, blocks replicative DNA synthesis immediately but incompletely, suggesting a participation of topoisomerase I at the replication fork, but it, too, has no influence on DNA repair. We thus find no evidence for involvement of either topoisomerase I or II in the response of cells to UV damage.
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PMID:Comparison of effects of fostriecin, novobiocin, and camptothecin, inhibitors of DNA topoisomerases, on DNA replication and repair in human cells. 215 21

We have developed a simple, effective genetic screen for mutant alleles of eukaryotic DNA topoisomerase I that manifest severely depressed or complete loss of enzymatic function. The screen is based on the extreme toxicity of vaccinia topoisomerase expression in the Escherichia coli lysogen strain BL21(DE3) and is notable for its ease in distinguishing nonsense mutations (that result in truncated proteins) from missense mutations. The power of the method is evinced by our observation that 100% of the candidate alleles identified in the screen were ultimately found to have single-base changes at the DNA level that result in amino acid substitutions at the protein level. By mutagenizing plasmid DNA in vitro with hydroxylamine and applying this phenotypic screen, we have isolated five distinct single amino acid substitution mutants, each of which shows a biochemical phenotype, that is, greater than or equal to 90% reduction in specific DNA relaxing activity of the mutant protein relative to wild type. The amino acids thus implicated in topoisomerase function have identical or related counterparts at homologous positions in the topoisomerases from yeast and man. The same genetic screen has been applied to the selection of temperature-sensitive alleles of the vaccinia topoisomerase, leading to the isolation of two additional single-hit mutant alleles that display a temperature-sensitive growth phenotype in E. coli BL21(DE3). By broadening our mutagenesis procedures, we expect to generate a comprehensive map of vaccinia topoisomerase function and primary protein structure that should have direct application to eukaryotic cellular enzymes. Our methodology should be applicable to the selection of missense and conditional mutant alleles in other genes whose expression in bacteria is toxic.
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PMID:Phenotypic selection and characterization of mutant alleles of a eukaryotic DNA topoisomerase I. 216 40

Type I topoisomerases (EC 5.99.1.2) are those enzymes capable of relaxing negatively supercoiled DNA without the need for ATP. The central role played by these enzymes in cell function suggests that the structure of type I topoisomerases may be highly conserved in eukaryotic cells. However, the extent of the conservation among eukaryotes is unknown. Human DNA topoisomerase I is an autoimmune antigen (Scl-70) of scleroderma patients. We have found that the autoimmune antibodies in human Scl-70 sera recognize protein from various plants, and these proteins display DNA relaxation function. In addition, Scl-70 antibodies were able to inhibit enzymatic activity of plant topoisomerase I. Therefore, the immunological cross-reactivity of the plant topoisomerase with human antibodies demonstrates that, despite divergence of eukaryotic organisms, these plant and animal enzymes retain structurally similar enzymatic features.
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PMID:Plant DNA topoisomerase I is recognized and inhibited by human Scl-70 sera autoantibodies. 216 85

The effect of cyanomorpholinyldoxorubicin, morpholinyldoxorubicin, doxorubicin, and Actinomycin D were studied on purified mouse leukemia (L1210) DNA topoisomerases I and II. DNA unwinding and cross-linking were also studied. It was found that 1) morpholinyldoxorubicin, cyanomorpholinyldoxorubicin, and Actinomycin D (but not doxorubicin) stimulated DNA topoisomerase I-induced cleavage at specific DNA sites; 2) only doxorubicin and Actinomycin D stimulated DNA cleavage by DNA topoisomerase II; 3) at higher drug concentrations, DNA intercalators suppressed enzyme-mediated DNA cleavage induced by DNA topoisomerase I, as well as topoisomerase II; 4) only cyanomorpholinyldoxorubicin produced DNA-DNA cross-links; no DNA unwinding could be observed; and 5) DNA intercalation (unwinding) potency of morpholinyldoxorubicin was about 2-fold less than that of doxorubicin. The data indicate that some DNA intercalators are not only inhibitors of DNA topoisomerase II but act also on DNA topoisomerase I. The stabilization of cleavage intermediates by intercalators may have a common mechanism for DNA topoisomerase I and DNA topoisomerase II.
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PMID:Effects of morpholinyl doxorubicins, doxorubicin, and actinomycin D on mammalian DNA topoisomerases I and II. 216 30

A protein factor with an estimated molecular mass of 50 kDa has been purified to homogeneity from the silk gland of Bombyx mori. In the presence of a molar excess of this factor and eukaryotic DNA topoisomerase II, relaxed circular DNA is converted to the negatively supercoiled form. Eukaryotic DNA topoisomerase I cannot substitute for eukaryotic DNA topoisomerase II in the supercoiling reaction. The reaction is dependent on ATP and is inhibited by VP-16, a specific inhibitor of eukaryotic DNA topoisomerase II. When DNA topoisomerase I is subsequently added to the supercoiling reaction mixture, the supercoiled DNA becomes relaxed. These results suggest that when both the 50-kDa protein and eukaryotic DNA topoisomerase II are present in excess, unconstrained negative supercoils are introduced into DNA.
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PMID:Purification of a DNA supercoiling factor from the posterior silk gland of Bombyx mori. 216 76

We have isolated stable teniposide (VM26)-resistant cell lines from human cancer KB cells by stepwise exposure to increasing doses of the drug. At each step, we have purified VM26-resistant cell lines. KB/VM-a, KB/VM-b, KB/VM-1, KB/VM-2, KB/VM-3, and KB/VM-4 showed 3-, 6-, 12-, 16-, 74-, and 95-fold higher resistance to VM26 than did KB. We have further characterized KB/VM-2 and KB/VM-4 which showed about 15- and 100-fold higher resistance to VM26 or etoposide (VP16) than did KB. Both VM26-resistant cell lines showed 4- to 11-fold higher relative resistance to daunomycin and Adriamycin than did KB. Steady-state levels of the cellular accumulation of radioactive VP16 in KB/VM-2 and KB/VM-4 cells were about 40% of that of KB cells, whereas similar levels of radioactive daunomycin accumulation were observed in KB/VM-2 and KB/VM-4 cells as KB cells. Topoisomerase II activity of nuclear extracts of both KB/VM-2 and KB/VM-4 assayed by decatenation of kinetoplast DNA was consistently two-thirds or less the activity of KB cells. A similar reduction was seen in both immunoblot assays with specific anti-topoisomerase II antibody and Northern blot analysis with specific human DNA topoisomerase II complementary DNA. DNA topoisomerase I activity, however, was similar between the mutants and their parent. Furthermore, cell growth of KB/VM-2 and KB/VM-4 was more thermolabile than that of KB, while KB/VM-b already showed temperature-sensitive growth. KB/VM-1 did show reduced accumulation of VP16 as in KB/VM-2 or KB/VM-4, but it had a normal level of topoisomerase II content as in KB cells. These data suggest that the reduced expression of DNA topoisomerase II, possibly combined with decreased permeability to the drugs, can account for the acquired VM26 resistance of KB/VM-2 and KB/VM-4 cells and also that the temperature-sensitive phenotype might not be obligatorily coupled with the reduced expression of topoisomerase II or the decreased permeability.
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PMID:Reduction of drug accumulation and DNA topoisomerase II activity in acquired teniposide-resistant human cancer KB cell lines. 216 82

Collateral drug sensitivity was induced in CPT-11-resistant cell lines (CPT-K and T). Ten of the 19 kinds of antineoplastic agents (especially, 5 of 6 kinds of DNA topoisomerase II inhibiting agents) were effective in inducing collateral drug sensitivity. Alteration of DNA topoisomerase I seemed to be unrelated to acquisition of multidrug resistance.
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PMID:Collateral drug sensitivity induced in CPT-11 (a novel derivative of camptothecin)-resistant cell lines. 216 67


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