Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:5.99.1.3 (topoisomerase)
 9,911 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Teniposide [4'-demethylepipophyllotoxin-4-(4,6-O-thenylidene-beta-D- glucopyranoside) (VM-26)] is a cancer chemotherapeutic drug with a high target specificity for DNA topoisomerase II. This agent induces repairable protein-bridged double-strand DNA breaks, which have been correlated with cytotoxicity, but high concentrations of VM-26 also induce irreversible DNA degradation and apoptotic cell death. It is not known whether this degradation occurs uniformly throughout the genome or in a gene-specific manner. To answer this question, DNA was isolated from HL-60 promyelocytic leukemia cells exposed to 5 microM VM-26 for varying periods of up to 12 h. Nucleosomal "ladders" on 2.0% agarose gels stained with ethidium bromide were detectable after 3 h of exposure, indicative of apoptosis. Gene-specific DNA degradation was investigated by Southern blot analysis. The genes for 18S rRNA and glucose-6-phosphate dehydrogenase were representatives of constitutively expressed (i.e., "housekeeping") genes. The proto-oncogenes c-myc, c-Ha-ras, and bcl-2 were examined as examples of other transcriptionally active genes, while transcriptionally inactive genes in HL-60 cells were studied by probing for the immunoglobulin heavy chain joining region and lambda light chain constant region genes. The rates of DNA degradation, and its extent after 12 h, were similar for all nuclear genes studied. However, there was striking resistance of mitochondrial DNA to endonucleolytic degradation. These data demonstrate that VM-26 can elicit a widespread degradative process which affects nuclear but not mitochondrial DNA.
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PMID:Teniposide induces nuclear but not mitochondrial DNA degradation. 159 97

Sequences located several kilobases both 5' and 3' of the stably transcribed portion of several genes hybridize to radio-labeled pure fragments of the alternating sequence poly (dG-dT) (dC-dA) ["poly(GT)"]. The genes include the ribosomal DNA of mouse, rat, and human, and also human glucose-6-phosphate dehydrogenase (G6PD) and mouse hypoxanthine-guanine phosphoribosyl transferase (HPRT). HPRT has additional hybridizing sequences in introns. Fragments that include the hybridizing sequences and up to 300 bp of adjoining DNA show perfect runs of poly(GT) (greater than 30bp) in all but the human 5' region of rDNA, which shows a somewhat different alternating purine:pyrimidine sequence, poly(GTAT) (36bp). Within 150 bp of these sequences in various instances are found a number of other sequences reported to affect DNA conformation in model systems. Most marked is an enhancement of sequences matching at least 67% to the consensus binding sequence for topoisomerase II. Two to ten-fold less of such sequences were found in other sequenced portions of the nontranscribed spacer or in the transcribed portion of rDNA. The conservation of the locations of tracts of alternating purine:pyrimidine between evolutionarily diverse species is consistent with a possible functional role for these sequences.
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PMID:Locations and contexts of sequences that hybridize to poly(dG-dT).(dC-dA) in mammalian ribosomal DNAs and two X-linked genes. 326 16

Many of the discoveries of multidrug resistance (MDR) have resulted from studies using drug-resistant cultured tumor cell lines as experimental models. To date, there has been no report on the detailed characterization of such a cell line from renal cell carcinoma (RCC). By long-term exposure of an established RCC (RCC8701) to increasing concentrations of adriamycin, we established a series of subcultures that were considerably more resistant to the cytotoxic effect of this drug. Biological morphology and cell cycles were analyzed by morphometry and flow cytometry. The chemoresistance index of cells were measured by methyl tetrazolium assay. For evaluation of the expression of MDR-related protein (MRP), mdr-1, glutathione transferase (GST-pi), and topoisomerase II mRNAs, the reverse transcription-polymerase chain reaction was used. Membranous expression of mdr-1-related p-glycoprotein was analyzed by immunofluorescence cytometry. The intracellular content of both glutathione (GSH) and glucose-6-phosphate dehydrogenase (G-6-PDH) were measured using a capillary electrophoresis method. Compared with parent cells, the resistant sublines had a slower growth rate and lower confluent density. They were smaller and mixed with giant cells in different sizes and with different numbers of nucleoli. Flow cytometric analyses showed that resistant cells had a greater percentage of cells in the G2/M phase. The resistant cells, RCC8701/ADR800, were 122 times more resistant to adriamycin and 238 times more resistant to epirubicin than the parent cells. The resistant cells also demonstrated cross-resistance to cisplatin and 5-fluorouracil. In addition to MRP, the contents of mRNA coding for mdr-1, GST-pi, and topoisomerase II in the MDR sublines were higher than in the native cell line. A higher content of cytoplasmic GSH and G-6-PDH were found in the resistant cells; however, the expression of the MDR-related membranous glycoprotein, p-glycoprotein, was not raised. The adriamycin-induced MDR sublines may be used as an experimental system for the search of a means to overcome drug resistance and elucidate possible mechanisms of acquired MDR involved in human renal cancer.
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PMID:Establishment and characterization of renal cell carcinoma cell lines with multidrug resistance. 1085 Jun 29