Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nucleotide sequences that are cleaved by calf thymus type I topoisomerase have been determined using cloned human Ha-ras and p53 genes. Localization and relative frequency of single-strand cleavages within these sequences were observed to change in the presence of the cytotoxic alkaloid camptothecin.
Mol Biol (Mosk)
PMID:[Effect of camptothecin on the DNA-relaxing and DNA-cleavage activity of calf thymus topoisomerase I]. 254 95

A well defined extrachromosomal DNA element, referred to as an episome (Ostrowski, M., Richard-Foy, H., Wolford, R., Berard, D., and Hager, G. (1983) Mol. Cell. Biol. 3, 2045-2057), was employed as a target for the topoisomerase II inhibitors amsacrine and teniposide. Both drugs have distinct mechanisms of action in cleaving the episome, as defined by topological forms conversion assays. The concentration ranges required to measure episomal cleavage are similar. The onset of damage induced by amsacrine begins within 1 min and is maintained at that level for at least 1 h. Teniposide induces damage that peaks between 30 and 60 min. The amsacrine-induced damage is only partially reversible, whereas teniposide-induced damage is almost completely reversible. Sites of specific cleavage are quite dissimilar. Multiple cleavage sites are formed in the episomal regulatory regions after amsacrine treatment, whereas a single cleavage in the regulatory region and one outside this region are found after teniposide treatment. Transcriptional activation using dexamethasone does not change the amount or site preference of episomal cleavage induced by either agent. Damage to the episome was quantitatively compared with damage produced in genomic DNA between 500 and 24,000 rad equivalents. The study showed that amsacrine has a significant (33-38-fold) preference for episomal DNA over genomic DNA.
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PMID:A study of drug-induced topoisomerase II-mediated DNA lesions on episomal chromatin. 255 Apr 34

Treatment of SV40-infected monkey cells with amonafide (benzisoquinolinedione), an intercalative antitumor drug, resulted in rapid accumulation of linearized intracellular SV40 DNA molecules that were protein linked. Studies using purified mammalian DNA topoisomerase II have shown that amonafide and its structural analogs interfere with the breakage-rejoining reaction of the enzyme by stabilizing a reversible enzyme-DNA "cleavable complex." Denaturation of the cleavable complex with sodium dodecyl sulfate resulted in DNA cleavage and the covalent association of topoisomerase II polypeptides with the cleaved DNA. Unwinding measurements indicate that amonafide is a DNA intercalator. These results suggest that amonafide and its structural analogs (e.g., mitonafide) represent a new class of intercalative topoisomerase II-active antitumor drugs. Different from other topoisomerase II-active antitumor drugs, amonafide and mitonafide induce specific DNA cleavage at a single major site on pBR322 DNA. The strong site specificity of amonafide may allow detailed characterization of the intercalator-stabilized, topoisomerase II-DNA cleavable complex.
Mol Pharmacol 1989 Sep
PMID:Topoisomerase II-mediated DNA cleavage by amonafide and its structural analogs. 255 Jul 74

Conditions, such as anoxia or glucose starvation, which induce the glucose-regulated set of stress proteins also lead to resistance to adriamycin (J. Shen, C. Hughes, C. Chao, J. Cai, C. Bartels, T. Gessner, and J. Subjeck, Proc. Natl. Acad. Sci. USA 84:3278-3282, 1987) and etoposide. We report here that chronic anoxia, glucose starvation, 2-deoxyglucose, the calcium ionophore A23187, glucosamine, ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), and tunicamycin (all specific inducers of the glucose regulated system) lead to a rapid and selective depletion of topoisomerase II from isolated nuclei of Chinese hamster ovary cells. This effect precedes a decline in tritiated thymidine incorporation and a redistribution of cells from S into G1/G0. The depletion of the enzyme is not accompanied by a decline in mRNA levels. We have also examined the mutant Chinese hamster K12 cell line which is temperature sensitive for expression of glucose-regulated proteins. When nuclei were isolated from K12 cells incubated at the nonpermissive temperature, a loss of topoisomerase II was again observed in congruence with the expression of stress proteins and cellular resistance to etoposide. These changes were not obtained in parental Wg1A cells incubated at the same temperature. These studies indicate that topoisomerase II is highly sensitive to glucose-regulated stresses and that its depletion from the nucleus, with the associated changes in cell cycle parameters, may represent general characteristics of the glucose-regulated state. Since anoxia and glucose starvation can occur during tumor development, this pathway for expression of drug resistance may have clinical ramifications.
Mol Cell Biol 1989 Aug
PMID:Depletion of topoisomerase II in isolated nuclei during a glucose-regulated stress response. 255 89

Immunoscreening of the human placenta cDNA-library in the expression vector lambda gt11 using non-isotope detection based on the avidin-biotin system allowed to identify a number of clones encoding human topoisomerase I. The fusion protein from an extract of Escherichia coli cells infected with the recombinant phage lambda gt11 interacts with the monoclonal antibody raised against topoisomerase I from calf thymus; the dissociation constant being 5.7.10(-8) M. The restricted DNA fragments coding for the topoisomerase polypeptide in the composition of the fusion protein were recloned, and expression in the pEX vector was obtained. The functional analysis of the expression products has enabled localization of the epitope of binding the monoclonal antibody. It was demonstrated that the identified fusion protein can be applied for diagnosis of autoimmune diseases.
Mol Biol (Mosk)
PMID:[Topoisomerase I from human placenta. Functional activity of products of expression of cloned cDNA fragments]. 256 Nov 76

A consensus sequence has been derived for vertebrate topoisomerase II cleavage of DNA (Spitzner, J. R. and Muller, M. T. (1988) Nucleic Acid. Res. 16, 5533-5556). An independent sample of 65 topoisomerase II sites (obtained in the absence of topoisomerase II inhibitors) was analyzed and found to match the consensus sequence as well as enzyme sites determined in the presence of the anti-tumor drug 4'-(9-acridinyl-amino)-methanesulfon-m-anisidide (m-AMSA). As originally described, conventional application of the consensus sequence afforded accuracy in the prediction of the locations but not the frequencies of topoisomerase II cleavages. In the present report, we describe a new method which quantitatively discriminates sites from nonsites, called the 'matrix mean' method (the mean match of a site to the matrix of base proportions from the original consensus sequence derivation). Furthermore, we derived a second method, called the 'unique score' model, which predicts frequency of topoisomerase II activity at a cleavage site. In the unique score method both DNA strands of a site are examined to determine the total number of the consensus positions that match on at least one strand of a potential site. From the new data base of 65 topoisomerase II sites, cleavages were scored for relative cleavage strength. Linear regression analysis showed a significant (p less than 0.01) correlation between the unique score and cleavage strength. The study was extended to show that the unique score model accurately and quantitatively predicts topoisomerase II sites either in the absence or presence of m-AMSA using the same consensus sequence.
J Mol Recognit 1989 Sep
PMID:Application of a degenerate consensus sequence to quantify recognition sites by vertebrate DNA topoisomerase II. 256 27

The nuclear enzyme DNA topoisomerase II catalyzes the breakage and resealing of duplex DNA and plays an important role in several genetic processes. It also mediates the DNA cleavage activity and cytotoxicity of clinically important anticancer agents such as etoposide. We have examined the activity of topoisomerase II during the first cell cycle of quiescent BALB/c 3T3 cells following serum stimulation. Etoposide-mediated DNA break frequency in vivo was used as a parameter of topoisomerase II activity, and enzyme content was assayed by immunoblotting. Density-arrested A31 cells exhibited a much lower sensitivity to the effects of etoposide than did actively proliferating cells. Upon serum stimulation of the quiescent cells, however, there was a marked increase in drug sensitivity which began during S phase and reached its peak just before mitosis. Maximal drug sensitivity during this period was 2.5 times greater than that of log-phase cells. This increase in drug sensitivity was associated with an increase in intracellular topoisomerase II content as determined by immunoblotting. The induction of topoisomerase II-mediated drug sensitivity was aborted within 1 h of exposure of cells to the protein synthesis inhibitor cycloheximide, but the DNA synthesis inhibitor aphidicolin had no effect. In contrast to the sensitivity of cells to drug-induced DNA cleavage, maximal cytotoxicity occurred during S phase. A 3-h exposure to cycloheximide before etoposide treatment resulted in nearly complete loss of cytotoxicity. Our findings indicate that topoisomerase II activity fluctuates with cell cycle progression, with peak activity occurring during the G2 phase. This increase in topoisomerase II is protein synthesis dependent and may reflect a high rate of enzyme turnover. The dissociation between maximal drug-induced DNA cleavage and cytotoxicity indicates that the topoisomerase-mediated DNA breaks may be necessary but are not sufficient for cytotoxicity and that the other factors which are particularly expressed during S phase may be important as well.
Mol Cell Biol 1987 Sep
PMID:Topoisomerase-specific drug sensitivity in relation to cell cycle progression. 282 20

Resistance of noncycling cells to amsacrine (m-AMSA) has been widely reported and may limit the activity of this drug against solid tumors. The biochemical mechanism(s) for this resistance have been investigated using spontaneously transformed Chinese hamster fibroblasts (AA8 cells, a subline of Chinese hamster ovary-cells) in log- and plateau-phase spinner cultures. In early plateau phase most cells entered a growth-arrested state with a G1-G0 DNA content and showed a marked decrease in sensitivity to cytotoxicity induced by a 1-h exposure to m-AMSA or to its solid tumor-active analogue, CI-921. Studies with radiolabeled m-AMSA established that similar levels of drug were accumulated by log- and plateau-phase cells and that there was no significant drug metabolism in either of these cultures after 1 h. However, marked differences in sensitivity to m-AMSA-induced DNA breakage were observed using a fluorescence assay for DNA unwinding (Kanter P.M., and Schwartz, H.S., Mol. Pharmacol., 22: 145-151, 1982). Changes in sensitivity to DNA breakage occurred in parallel with changes in sensitivity to m-AMSA-induced cell killing. DNA breaks disappeared rapidly after drug removal (half-time approximately 4 min), suggesting that these lesions were probably mediated by DNA topoisomerase II. Resistance to m-AMSA may therefore be associated with changes in topoisomerase II activity in noncycling cells.
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PMID:Mechanism of resistance of noncycling mammalian cells to 4'-(9-acridinylamino)methanesulfon-m-anisidide: comparison of uptake, metabolism, and DNA breakage in log- and plateau-phase Chinese hamster fibroblast cell cultures. 282 71

The gene gyrA of Escherichia coli, which encodes the A subunit of DNA gyrase (topoisomerase II), has been cloned and a region of approximately 3300 base-pairs sequenced. An open reading frame of 2625 nucleotides coding for a protein of 97,000 Mr is located. The peptide weight of the subunit predicted from this open reading frame is in close agreement with previously published estimates of that of the A subunit. There is a "TATAAT" promoter motif located 44 bases upstream from the first "ATG" of the open reading frame. The amino acid sequence derived from the nucleotide sequence is about 50% homologous with that derived from the Bacillus subtilis gyrA gene sequence, with several regions showing greater than 90% homology.
J Mol Biol 1987 Oct 20
PMID:Cloning and sequencing of the Escherichia coli gyrA gene coding for the A subunit of DNA gyrase. 282 31

We characterized a DNA repair system in frog oocytes by comicroinjection of UV-irradiated pBR322 DNA and radiolabeled nucleotides. Repair synthesis was monitored by incorporation of label into recovered pBR322 DNA and by a novel method in which the removal of UV photoproducts was determined from the shift of DNA topoisomers that occurs during gel electrophoresis upon repair of these lesions. We investigated the effects of several drugs in the oocyte system and found that although novobiocin, an inhibitor of topoisomerase II, was an effective inhibitor of repair, VM-26, another inhibitor of topoisomerase II, was not. In addition, the topoisomerase I inhibitor camptothecin had no effect on repair in this system. Finally, circular DNA (either supercoiled or nicked circular) was repaired at least 50 times more rapidly than linear DNA.
Mol Cell Biol 1987 Dec
PMID:Repair of UV-induced lesions in Xenopus laevis oocytes. 283 Apr 88


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