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)

DNA topoisomerase II was isolated from mouse leukemia L1210 cells and the activity was determined by using P4 phage knotted DNA and pBR 322 DNA as the substrates. Based on these results, a method for screening antitumor agents by using DNA topoisomerase II as a target was established. The experiments showed that DNA topoisomerase II catalyzed pBR 322 DNA breaking and relaxing which were reversible and dependent on ATP. The activity was increased 2-4 times in the presence of ATP 1 mmol.L-1. In contrast with type II enzyme, the activity of DNA topoisomerase I was completely inhibited in the presence of ATP 1 mmol.L-1 and had full activity in the absence of ATP. Type II enzyme also showed the unknotting activity by using p4 phage knotted DNA as a substrate. DNA cleavage and relaxing reaction induced by type II enzyme increased 5-fold in the presence of Doxorubicin (Dox) 1 microgram.ml-1 or daunorubicin (Dau). Etoposide (Eto) and aclarubicin B (Acl B) also stimulated the reaction at 100 micrograms.ml-1. The cleavage reaction resulted from topoisomerase II was inhibited by other agents, such as frankincense extracts, terpenic compounds (BC series).
...
PMID:Determination of DNA topoisomerase II activity from L1210 cells--a target for screening antitumor agents. 166 90

We have examined the relationship between topoisomerase II content and the DNA cleavage activity and cytotoxicity of etoposide during proliferative and quiescent culture conditions. In proliferating cultures of Chinese hamster ovary (CHO) cells, human lymphoblastic CCRF cells, and mouse leukemia L1210 cells, there was easily detectable topoisomerase II by immunoblotting. In contrast, quiescent CHO cells contained virtually no detectable topoisomerase II, while the content of L1210 cells was unchanged. Enzyme content of quiescent CCRF cells was diminished but detectable. DNA cleavage activity induced by etoposide correlated well with enzyme content in proliferating and quiescent cells. Quiescent CHO and CCRF cultures were highly resistant to the cytotoxic effects of etoposide as expected. However, despite unchanged enzyme content and DNA cleavage activity, there was also significant resistance observed in plateau L1210 cells. We have also investigated topoisomerase content and drug activity as a function of cell cycle progression. Following serum stimulation of confluent BalbC/3T3 cells, maximal etoposide-induced DNA cleavage activity is observed in G2/M and is associated with an increase in topoisomerase II content. Maximum cytotoxicity, however, occurs during mid to late S phase. Our data suggest that topoisomerase II content may be an important determinant of chemotherapeutic sensitivity during alterations in the proliferative status of the cell. However, it is clear that other factors must be involved in cell sensitivity, and elucidation of these may contribute to our understanding of the mechanism of action of these drugs.
...
PMID:Role of proliferation in determining sensitivity to topoisomerase II-active chemotherapy agents. 281 35

An attempt was made to analyze the mechanism by which 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA) inhibits mammalian DNA topoisomerase II. The effects of various 9-aminoacridine derivatives differing by their DNA affinities and DNA sequence selectivity of binding were compared in the presence of purified mouse leukemia L1210 DNA topoisomerase II. No correlation was found between DNA unwinding and topoisomerase II inhibition. 9-Aminoacridine was inactive as a topoisomerase II inhibitor and o-AMSA was only weakly active. The location of L1210 topoisomerase II mediated DNA breaks produced in the absence or presence of 9-aminoacridines were studied in [32P]-end-labeled pBR 322 DNA. All 9-aminoacridines, even those differing by their DNA sequence selectivity of binding, produced similar DNA cleavage patterns. Most drug-induced topoisomerase II mediated DNA breaks appeared at sites that were already cleaved by the enzyme in the absence of drug. The present results suggest that 9-aminoacridines inhibit L1210 DNA topoisomerase II by interacting at or near enzyme-DNA complexes by some unknown DNA effect or by direct protein interaction.
...
PMID:Role of DNA intercalation in the inhibition of purified mouse leukemia (L1210) DNA topoisomerase II by 9-aminoacridines. 282 23

Treatment of mouse leukemia L1210 cells with the polyamine biosynthesis inhibitor alpha-difluoromethylornithine (DFMO) increased the magnitude of the DNA scission produced by the DNA intercalator 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA). This enhanced DNA scission was protein concealed and protein associated, as was the m-AMSA-induced scission in cells unexposed to DFMO. The effect of DFMO required more than 6 hr to develop and was greater at 48 hr than at 24 hr of exposure to DFMO. Exogenously added putrescine partially reversed the effects of DFMO, while exerting no effect on m-AMSA-induced DNA scission in cells unexposed to DFMO. The cellular uptake of [14C]-m-AMSA was the same in DFMO-treated or untreated cells. The DNA scission and DNA-protein cross-linking produced by m-AMSA appear to represent the stabilization of an intermediate in the normal cycle of topoisomerase II function (Nelson, E.M., Tewey, K.M., and Liu, L.F., Proc. Natl. Acad. Sci. USA, 81: 1361-1365, 1984). Since polyamine depletion appears to affect the magnitude of this effect in cells, and since polyamines can alter topoisomerase II function in vitro, polyamines may be involved in topoisomerase function in vivo either directly or through secondary effects, such as alterations of the conformation of chromatin, the intracellular site at which topoisomerase acts.
...
PMID:Effect of difluoromethylornithine, an inhibitor of polyamine biosynthesis, on the topoisomerase II-mediated DNA scission produced by 4'-(9-acridinylamino)methanesulfon-m-anisidide in L1210 murine leukemia cells. 298 83

Topoisomerase II mediated DNA scission induced by both a nonintercalating agent [4'-demethylepipodophyllotoxin 4-(4,6-O-ethylidene-beta-D-glucopyranoside) (VP-16)] and an intercalator [4'-(9-acridinylamino) methanesulfon-m-anisidide (m-AMSA)] was studied as a function of proliferation in Chinese hamster ovary (CHO), HeLa, and mouse leukemia L1210 cell lines. Log-phase CHO cells exhibited dose-dependent drug-induced DNA breaks, while plateau cells were found to be resistant to the effects of VP-16 and m-AMSA. Neither decreased viability nor altered drug uptake accounted for the drug resistance of these confluent cells. In contrast to CHO cells, plateau-phase HeLa and L1210 cells remained sensitive to VP-16 and m-AMSA. Recovery of drug sensitivity by plateau-phase CHO cells was found to reach a maximum approximately 18 h after these cells regained exponential growth and was independent of DNA synthesis. DNA strand break frequency correlated with cytotoxicity in CHO cells; log cells demonstrated an inverse log linear relationship between drug dose (or DNA damage) and colony survival, whereas plateau-derived colony survival was virtually unaffected by increasing drug dose. Topoisomerase II activity, whether determined by decatenation of kinetoplast DNA, by cleavage of pBR322 DNA, or by precipitation of the DNA-topoisomerase II complex, was uniformly severalfold greater in log-phase CHO cells compared to plateau-phase cells.
...
PMID:Proliferation dependence of topoisomerase II mediated drug action. 301 Oct 82

The DNA intercalator, 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA) and the nonintercalator, etoposide (VP-16) produce topoisomerase II-mediated protein-linked DNA strand breaks. This function of topoisomerase II was investigated in relation to cell proliferation and cell cycle. Mouse fibroblasts NIH 3T3 and mouse leukemia L1210 cells stop proliferation when they reach a certain density. Nuclei were isolated from proliferative or quiescent cells and then treated with drug for 30 min. DNA modifications were assayed by alkaline elution. We found that the frequencies of m-AMSA- or VP-16-induced DNA-protein links were higher in nuclei from exponentially growing than in those from quiescent cells in both the 3T3 and the L1210 lines. Drug-induced protein-associated DNA breaks were also studied as a function of the cell cycle in 3T3 cells that had been arrested by contact inhibition in medium containing 1% calf serum and then stimulated to proliferate by raplating at a lower cell density in medium containing 10% serum. In these synchronized cells, a large peak of [3H]thymidine incorporation occurred 18-30 h after replating. The yield of DNA-protein cross-links produced by 30-min drug treatments of nuclei isolated at various times after growth initiation increased concomitantly with the peak of the DNA synthesis. The topoisomerase II activity of nuclear extracts, as measured by kinetoplast DNA decatenation followed a similar pattern. Using colony-forming assays, we also observed that m-AMSA and VP-16 were most cytotoxic in proliferative cells and during DNA synthesis. These results suggest that alkaline elution measurement of m-AMSA- or VP-16-induced protein-linked DNA breaks reflects the association of topoisomerase II with DNA. This association is increased during DNA replication, making the cells more vulnerable to m-AMSA and VP-16 at this time.
...
PMID:Topoisomerase II-mediated DNA breaks and cytotoxicity in relation to cell proliferation and the cell cycle in NIH 3T3 fibroblasts and L1210 leukemia cells. 303 May 40

We have shown previously that quiescent Chinese hamster ovary (CHO) cells are less sensitive than log phase CHO cells to the cytotoxic and DNA cleavage effects of etoposide, a drug which appears to act via DNA topoisomerase II. This loss of sensitivity was associated with a decrease in topoisomerase enzyme activity in nuclear extracts of the quiescent cells. We have now extended our observations by examining the basis for the reduction in enzyme activity during quiescence. DNA topoisomerase II content, as assayed by immunoblotting with a polyclonal rabbit anti-topoisomerase II antiserum, was virtually absent in nuclear extracts of quiescent CHO cells in contrast to logarithmically growing cells. This suggests that the previously demonstrated loss of enzyme activity in CHO cells is a function of reduction in content rather than posttranslational modifications of the enzyme. Quiescent human lymphoblastic CCRF cells also exhibited reduced topoisomerase II content compared to actively proliferating cultures, but the difference was less than that observed in CHO cells. In contrast, log and plateau phase cultures of mouse leukemia L1210 cells exhibited similar topoisomerase II content. Reduction in enzyme content correlated with the ability of these cell lines to accumulate during quiescence with a G0-G1 content of DNA. Sensitivity to the DNA cleavage effects of etoposide in dividing and nondividing cells correlated well with enzyme content. As has been observed with CHO cells, both CCRF and L1210 cells in plateau phase were more resistant to the cytotoxic effects of etoposide than those actively dividing. The result with L1210 cells was surprising, however, in light of the equivalent DNA damage observed under the two growth conditions. Our data indicate that topoisomerase II enzyme content is proliferation dependent in some but not all cells and suggest that while enzyme content may be important in drug resistance in some cell types, other factors can decrease the sensitivity of the cell to cleavable complex formation as well.
...
PMID:Proliferation-dependent topoisomerase II content as a determinant of antineoplastic drug action in human, mouse, and Chinese hamster ovary cells. 303 4

A nuclear type I topoisomerase from mouse leukemia L1210 cells has been partially purified and characterized. The sedimentation coefficient of the enzyme by velocity sedimentation is 4.3 S, consistent with a globular protein of 68 kDa. Enzyme activity is stimulated 20-fold in the presence of magnesium over that achieved in KCl alone. The enzyme is completely inhibited in the presence of the berenil congeners HOE 13548 and 15030 while berenil itself caused only partial inhibition at concentrations below 200 micrograms/ml. An acid soluble protein of 30 kDa (by SDS-polyacrylamide gel electrophoresis) co-purified with the topoisomerase but could be separated by precipitation in a low salt buffer. This protein, as well as a protein of similar characteristics, histone H1, stimulated topoisomerase activity over a narrow concentration range. The role of topoisomerase in the DNA strand scission observed in L1210 cells following exposure to intercalating agents remains conjectural as the purified enzyme did not produce nicks in plasmid DNA in the presence of adriamycin.
...
PMID:Properties of a purified nuclear topoisomerase from L1210 cells. 631 36

The DNA intercalating agents 4'-(9-acridinyl-amino) methanesulfon-m-anisidide (m-AMSA) and adriamycin were studied by using filter elution methods to measure DNA single-strand breaks (SSB's), DNA-protein cross-links (DPC's), and double-stranded breaks (DSB's) in mouse leukemia L1210 cells. Both compounds produced SSB's and DPC's at nearly 1:1 ratios. The SSB's and DPC's were shown to be localized with respect to each other; this was inferred from the finding that filter assays based on protein adsorption completely prevented the elution of the DNA single-strand segments between SSB's. In the case of m-AMSA, which produces relatively high frequencies of DNA lesions, the possibility that a protein bridges across the SSB was excluded by alkaline sedimentation studies. Both compounds also produced DSB's, but the SSB/DSB ratios differed; the SSB/DSB ratios increase in the following order: ellipticine greater than adriamycin greater than m-AMSA greater than X-ray [results of this paper combined with those of Ross, W. E., & Bradley, M. O. (1981) Biochim. Biophys. Acta (in press)]. The o-AMSA isomer is much less cytotoxic than m-AMSA and did not produce protein-associated strand breaks. The simplest model to explain the results is that a protein becomes covalently bound to either the 3' or the 5' termini of the intercalator-induced strand breaks. At moderately cytotoxic doses, m-AMSA yielded much larger frequencies of protein-associated SSB's than did adriamycin. m-AMSA-induced protein-associated SSB's saturated at approximately 60000 per cell over a concentration range in which m-AMSA uptake by the cells was proportional to the drug concentration. m-AMSA was found to enter and exit from cells very rapidly at 37 degrees C; protein-associated SSB's and DSB's also appeared and disappeared rapidly. At reduced temperature, however, the appearance and disappearance of protein-associated SSB's could be blocked while m-AMSA entry and exit still occurred. The saturation behavior and temperature dependence suggest that the formation and disappearance of protein-associated strand breaks is enzymatic. The simplest hypothesis is that the linked protein is a nuclease, such as a topoisomerase, which becomes bound to one terminus of the strand break it produces. It is proposed that topoisomerases producing SSB's and DSB's are stimulated to different degrees by different intercalators.
...
PMID:Protein-associated deoxyribonucleic acid strand breaks in L1210 cells treated with the deoxyribonucleic acid intercalating agents 4'-(9-acridinylamino) methanesulfon-m-anisidide and adriamycin. 689 73

A series of DNA-intercalating 9-anilinoacridines, namely 9-phenoxyacridines, 9-(phenylthio)acridines, and 9-(3',5'-disubstituted anilino)acridines, were synthesized as potential antitumor agents with inhibitory effects on DNA topoisomerase II. Unlike amsacrine (m-AMSA), these agents were designed to avoid the oxidative metabolic pathway. These acridine derivatives were, therefore, expected to have long half-life in plasma. Both 9-phenoxyacridines and 9-(phenylthio)acridines were found to have moderate cytotoxicity against mouse leukemia L1210 and human leukemic HL-60 cell growth in culture. Among 9-(3',5'-disubstituted anilino)acridines, 3-(9-acridinylamino)-5-(hydroxymethyl)aniline (AHMA) was found to be a potent topoisomerase II inhibitor and exhibited significant antitumor efficacy both in vitro and in vivo. Chemotherapy of solid-tumor-bearing mice with 10, 10, and 5 mg/kg (QD x 4, ip) AHMA, VP-16, and m-AMSA, respectively, resulted in more tumor volume reduction by AHMA than by VP-16 or m-AMSA for E0771 mammary adenocarcinoma and B-16 melanoma. For Lewis lung carcinoma, AHMA was as potent as VP-16 but more active than m-AMSA. Structure-activity relationships of AHMA derivatives are discussed.
...
PMID:9-substituted acridine derivatives with long half-life and potent antitumor activity: synthesis and structure-activity relationships. 765 Jun 75


1 2 Next >>

---