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:5.99.1.2 (topoisomerase)
9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

MNNG-induced killing of V79 cells has been found to be enhanced on inhibition of topoisomerase II activity by nalidixic acid and poly(ADP-ribose) polymerase synthesis by benzamide. Using these 2 inhibitors in conjunction after MNNG treatment, some overlap in the functions of these 2 enzymes was observed. Nalidixic acid and benzamide were found to suppress the yields of mutations and SCEs induced by MNNG. Benzamide was more effective in suppressing the mutation yield whereas nalidixic acid was more effective in suppressing SCEs. A model based on the relative requirement of topoisomerase and poly(ADP-ribose) for the repair of different types of damage has been proposed to explain the results.
...
PMID:Response of V79 cells to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) treatment: inhibition of poly(ADP-ribose) and topoisomerase activity. 164 62

Treatment of a human promyelocytic leukemia cell line (HL-60) with etoposide for 3-4 hrs produced an extensive degradation of DNA. Agarose gel electrophoresis showed DNA fragmentation in a nucleosomal ladder pattern. Simultaneous addition of zinc ion (ZnSO4, 1 mM) inhibited DNA fragmentation, although the amount of DNA strand breakage introduced initially by etoposide did not change significantly as measured by the DNA unwinding assay. Furthermore, zinc ion abrogated both the activation of poly(ADP-ribose) synthesis and the morphologic changes characteristic of apoptosis by etoposide. These results suggest that zinc ion inhibits a metabolic process somewhere between initial DNA cleavage through an interference with type II topoisomerase and delayed degradation of cellular DNA to a nucleosome-like pattern.
...
PMID:Inhibition of both etoposide-induced DNA fragmentation and activation of poly(ADP-ribose) synthesis by zinc ion. 216 30

Mutant Chinese hamster V79 cells selected for alterations in poly(ADP-ribose) metabolism were shown to be resistant to epipodophyllotoxin (VP-16)-induced cytotoxicity. Cell lines ADPRT 54 and ADPRT 351 have reduced activity of poly(ADP-ribose) polymerase. N2, N3, and N4 cell lines grow in the absence of nicotinamide, with total NAD levels 1.5-3% of those found in parental V79 cells grown in complete medium. When grown in complete medium, the mutant cell lines are 2.3- to 9.6-fold resistant to VP-16-induced cytotoxicity. All of the cell lines respond to VP-16 treatment by formation of protein-cross-linked DNA strand breaks. Upon drug removal, all the cell lines reverse the DNA strand breaks at similar rates. Our studies show a clear dissociation between induction of DNA strand breaks and cytotoxicity. However, there is a good correlation between drug-induced sister chromatid exchanges and cytotoxicity. Thus, N3 cells, with low levels of VP-16-induced sister chromatid exchanges, show reduced levels of cytotoxicity relative to parental V79 cells, despite the fact that both cell lines show similar levels of VP-16-induced protein-cross-linked DNA strand breaks. Additional studies show that the time course of VP-16-induced cytotoxicity correlated better with the time course of sister chromatid exchange formation than with protein-cross-linked DNA strand break formation. These studies provide strong support for the proposal that VP-16-induced cytotoxicity involves the induction of sister chromatid exchanges. Thus, we suggest that drug-induced stabilization of topoisomerase II-DNA complexes stimulates induction of sister chromatid exchanges, which consequently lead to cell death.
...
PMID:Mechanism of epipodophyllotoxin-induced cell death in poly(adenosine diphosphate-ribose) synthesis-deficient V79 Chinese hamster cell lines. 232 96

The nuclear poly(ADP-ribose)polymerase activity of neuronal and glial cells during postnatal development of rats was studied. It was shown that the poly(ADP-ribose)polymerase activity of nuclei and nuclear matrix of neuronal cells during postnatal development of rats is increased, whereas the polymerase activity of glial cell nuclei and nuclear matrix in newborn and adult rats is higher than in 14-day-old animals. The DNA-topoisomerase II activity of neuronal nuclear matrix during the postnatal development of rats does not change, whereas the topoisomerase activity of glial nuclear matrix decreases but is always higher than the DNA-topoisomerase II activity of neuronal cell matrix during the postnatal development of rats. It is suggested that ADP-ribosylation in the nuclear matrix of neuronal cells causes the inhibition of the DNA-topoisomerase II activity of nuclear matrix.
...
PMID:[Study of nuclear poly(ADP-ribose)polymerase and DNA-topoisomerase II of brain cells during postnatal development of rats]. 254 54

We have investigated the association of human topoisomerase I with poly(ADP-ribosylated) domains of chromatin and the effects of this modification on the enzyme activity. In vitro poly(ADP-ribosylation) assays demonstrated that this enzyme was one of the major acceptors for this chromatin-dependent post-translational modification. Western blotting procedures using antibody to topoisomerase I indicated that under extensive poly(ADP-ribosylation) conditions, where a majority of poly(ADP-ribose) acceptor molecules form aggregates, the major population of the topoisomerase I associated with chromatin was apparently non-aggregated. The catalytic activity of the topoisomerase I associated with the poly(ADP-ribosylated) chromatin was 3-5-fold inhibited. Additionally, antibody to poly(ADP-ribose) was used to immunofractionate selectively the modified domains of chromatin. Our data suggests the presence of topoisomerase I, both adjacent and distal to the poly(ADP-ribosylated) sites of chromatin. Unmodified and a significant portion of the modified species of enzyme migrated as approximately 100-kDa proteins. However, the modified form of topoisomerase was noted to be catalytically less active as compared to the enzyme bound to the non-poly(ADP-ribosylated) nucleosomes. These results provide evidence, at the cellular level, for the poly(ADP-ribosylation)-mediated regulation of human topoisomerase I and suggest a functional significance for poly(ADP-ribosylation) in topoisomerase-related processes (replication, transcription, and recombination) in eukaryotes.
...
PMID:Poly(ADP-ribose)-mediated post-translational modification of chromatin-associated human topoisomerase I. Inhibitory effects on catalytic activity. 255 19

Chinese hamster V79 cells grown for several hours in suspension culture form spheroids which are more resistant to killing by ionizing radiation than cells grown on petri dishes, a phenomenon known as the "contact effect." Previous results using the alkali-unwinding assay as a measure of DNA damage have implicated differences in DNA conformation as contributing to this effect; spheroid DNA denatures more slowly in dilute alkali than monolayer DNA, perhaps due to the presence of constraints to DNA unwinding. In this paper, the rate of development of radiation resistance is shown to be similar when either cell survival or DNA unwinding is used as an end point. At the midpoint for development of resistance, approximately 10 h, the unwinding kinetics indicate that either half of the cells contain constraints to DNA unwinding, or half of the DNA in all of the cells contains constraints. The latter explanation appears more likely since all cells seem to develop these constraints at the same rate, regardless of position in the cell cycle or the degree of contact with other cells. Results using the microelectrophoresis assay to measure damage to individual nuclei confirm the fact that 10-h cultures show a homogeneous radiation response intermediate between that of monolayers and spheroids. Incubation of cells at room temperature or in the presence of drugs which inhibit cell cycle progression prevents full development of the contact effect. Conversely, incubation of cells in medium containing inhibitors of polyamine synthesis, adenylcyclase, glutathione synthesis, poly(ADP-ribose)polymerase, topoisomerase II, or cell-cell communication does not inhibit development of the contact effect as measured by DNA-unwinding kinetics.
...
PMID:Cell proliferation as a requirement for development of the contact effect in Chinese hamster V79 spheroids. 291 10

The effect of poly(ADP-ribosylation) on calf thymus topoisomerase type II reactions has been investigated. Unknotting of phage P4 head DNA, and relaxation and catenation of supercoiled PM2 DNA are inhibited. We conclude that the inhibition results from poly(ADP-ribosylation) on the following grounds. Firstly, the enzyme poly(ADP-ribose) (PADPR) synthetase and NAD are required, secondly, the competitive synthetase inhibitor nicotinamide abolishes topoisomerase inhibition, and thirdly, the polymer alone is not inhibitory. The mechanism of inhibition appears to be disruption of the strand cleavage reaction. A topoisomerase-DNA complex can be formed that upon treatment with protein denaturant at low ionic strength results in strand cleavage. The amount of DNA present in such a cleavable-complex progressively decreased following pretreatment of topoisomerase type II with PADPR synthetase and increasing concentrations of NAD. Treatment of the pre-formed complex with NAD and PADPR synthetase had no effect on its salt-induced dissociation. This suggests that either poly(ADP-ribosylation) has no influence on dissociation of topoisomerase, in contrast to association, or topoisomerase is not accessible to the synthetase when bound to DNA. Similar data were obtained with calf thymus type I topoisomerase.
...
PMID:Inhibition of calf thymus type II DNA topoisomerase by poly(ADP-ribosylation). 299 83

Newly-repaired DNA in chromatin is more sensitive to micrococcal nuclease than bulk DNA, but tends to become equally sensitive with time. This rearrangement of chromatin, which had previously been observed following repair of lesions produced by UV-light and of some bulky adducts, has now been shown to occur after repair of lesions induced by hydrogen peroxide and dimethylsulfate. In both cases there was an enhanced sensitivity to nuclease digestion of newly repaired DNA followed by a rearrangement whose kinetics was very similar to that observed in UV irradiated cells. Benzamide and 3-aminobenzamide, inhibitors of the synthesis of poly (ADP-ribose) and novobiocin, an inhibitor of topoisomerase, had no effect on the initially enhanced digestibility of repaired regions or on the chromatin rearrangement that followed. Poly (ADP-ribose) polymerase and topoisomerase are known to play some role in excision repair and have also been shown to cause alterations in the chromatin structure. However, the present results show that these alterations are not involved in this kind of chromatin rearrangement.
...
PMID:Rearrangement of mammalian chromatin structure following excision repair: absence of an effect of inhibitors of poly (ADP-ribose) polymerase and topoisomerase. 301 3

Poly(ADP-ribose) is synthesized in response to DNA strand breaks and covalently modifies numerous intracellular proteins. We have proposed that this modification regulates, i.e., inhibits, the activity of these enzymes, e.g., topoisomerases and proteases, which could otherwise cause additional DNA damage or alterations in chromatin structure. Inhibition of poly(ADP-ribose) polymerase by 3-amino-benzamide (3AB) in cells exposed to DNA-damaging agents would, according to this proposal, eliminate the regulatory role of ADP-ribosylation. When Chinese hamster ovary cells are cultured with methyl methanesulfonate (MMS) and 3AB, a synergistic increase in sister chromatid exchange frequency is observed. We investigated the regulatory role of poly(ADP-ribose) polymerase to see if topoisomerases or proteases are involved in this synergistic increase. Cells were exposed to MMS or the intercalating agent 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA), 3AB, and either the topoisomerase inhibitor novobiocin or the protease inhibitor antipain. Neither novobiocin nor antipain affected the synergistic response of MMS and 3AB or the additive response of m-AMSA and 3AB. These results suggest that topoisomerases or proteases do not account for the effect of 3AB on sister chromatid exchange frequency after DNA damage.
...
PMID:Potentiation of sister chromatid exchange by 3-aminobenzamide is not modulated by topoisomerases or proteases. 301 82

The frequency of sister chromatid exchanges (SCEs), both spontaneous and induced by UV-light, X-rays, mitomycin C and ethylmetansulphonate (EMS), has been investigated in cultured human peripheral blood lymphocytes. Besides, frequency of spontaneous and induced SCEs was studied under the action of the inhibitors of topoisomerase II, polymerase poly(ADP-ribose), and DNA repair, i. e. novobiocin, 3-metoxybenzamide, and caffeine, respectively. It is shown that the base-line SCEs in lymphocytes of the patient with xeroderma pigmentosum II (XP2LE) is dramatically higher compared to that in normal and pigmented xerodermoid cells (XP3LE). The above inhibitors of DNA synthesis and repair enhance the rate of spontaneous SCEs in normal, XP2LE and XP3LE cells. UV-, X-ray and chemical mutagens induced an increased frequency of SCEs in these cells. Simultaneous treatment with mutagenes and inhibitors of DNA synthesis and DNA repair enhanced the rate of SCEs in lymphocytes of healthy donors and in the XP3LE patient. The frequency of the XP2LE cells. Novobiocin, 3-MBA and caffeine significantly decreased the frequency of SCEs in mitomycin C- and EMS-treated XP2LE lymphocyte, which nevertheless was much higher than that in normal cells treated with the same agents.
...
PMID:[Spontaneous and induced sister chromatid exchanges in the blood lymphocytes of healthy persons and of xeroderma pigmentosum patients exposed to the inhibitors of DNA repair and replication caffeine, 3-methoxybenzamide and novobiocin]. 308 51


1 2 3 4 5 6 Next >>

---