Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:5.99.1.2 (topoisomerase)
 9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The studies described below were carried out to analyze the damage induced by DNA active drugs to episomal (Epstein-Barr virus, EBV) DNA in the Raji Burkitt's lymphoma cell line. This work: (i) applies pulsed-field gel electrophoresis (PFGE) techniques to quantify DNA damage on a large (approximately 180 kbp), circular target, (ii) investigates the DNA strand-scission behavior of different classes of drugs on the EBV episome, and (iii) compares EBV episomal damage to that generated in genomic DNA in the Raji cell line. Cells were treated with ionizing radiation to induce random strand scission, and the migration of topological forms of EBV was measured using PFGE. DNA damage induced in the episome by DNA active drugs was then assayed. Three drugs, acting by different types of DNA interactive mechanisms, were used: bleomycin, an intercalative DNA strand-scission agent; and amsacrine (mAMSA) and teniposide (VM26), intercalative and nonintercalative topoisomerase II active drugs, respectively. Rad equivalency of damage was determined by comparing the drug-induced change in percentage of Forms I and III to that generated by ionizing radiation. Additionally, single- and double-strand scission induced in genomic (total cellular) DNA by X-rays, bleomycin, amsacrine, and teniposide were assayed by high-sensitivity alkaline and neutral filter elution techniques. We demonstrate that pulsed-field gel electrophoresis is a useful technique for measuring form conversion in large episomal DNA. While all three drugs effect both episomal and genomic DNA strand scission, bleomycin appears to preferentially damage the EBV episome. The topoisomerase II active drugs mAMSA and VM26 show no evidence of episome-directed damage in this system and, in fact, damage genomic DNA at somewhat higher rates.
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PMID:Damage induced in episomal EBV DNA in Raji cells by antitumor drugs as measured by pulsed field gel electrophoresis. 752 29

In response to DNA damage and replication blocks, cells activate pathways that arrest the cell cycle and induce the transcription of genes that facilitate repair. In mammals, ATM (ataxia telangiectasia mutated) kinase together with other checkpoint kinases are important components in this response. We have cloned the rat and human homologs of Saccharomyces cerevisiae Rad 53 and Schizosaccharomyces pombe Cds1, called checkpoint kinase 2 (chk2). Complementation studies suggest that Chk2 can partially replace the function of the defective checkpoint kinase in the Cds1 deficient yeast strain. Chk2 was phosphorylated and activated in response to DNA damage in an ATM dependent manner. Its activation in response to replication blocks by hydroxyurea (HU) treatment, however, was independent of ATM. Using mass spectrometry, we found that, similar to Chk1, Chk2 can phosphorylate serine 216 in Cdc25C, a site known to be involved in negative regulation of Cdc25C. These results suggest that Chk2 is a downstream effector of the ATM-dependent DNA damage checkpoint pathway. Activation of Chk2 might not only delay mitotic entry, but also increase the capacity of cultured cells to survive after treatment with gamma-radiation or with the topoisomerase-I inhibitor topotecan.
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PMID:Mammalian Chk2 is a downstream effector of the ATM-dependent DNA damage checkpoint pathway. 1043 85

The objective of this study was to investigate the effect of arsenic trioxide (As(2)O(3)) on topoisomerase II levels using western blotting method on MDAH 2774 ovarian carcinoma cell culture. Experimental designs were established to determine the cytotoxic effects of As(2)O(3) on MDAH 2774 cells and the IC50 (fatal dose for the 50% of cells) value. Cytotoxicity experiments were carried out using various concentrations of As(2)O(3). The 2,3-bis[2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT) and trypan blue dye-exclusion tests were used to evaluate cytotoxicity. Topoisomerase II expressions were investigated using western blotting method with various concentrations of As(2)O(3). Densitometric analysis of topoisomerase 2 bands was carried out using Quantity One 1-D analysis software (Bio-Rad USA, Life Science Research, Hercules, CA). IC50 value of As(2)O(3) was found to be 5 x 10(-6) M for MDAH 2774 cells. When the bands were evaluated, it was observed that there was a decrease in topoisomerase II levels in MDAH 2774 cells with increasing concentrations of As(2)O(3). It was also observed by the densitometric analysis that topoisomerase II expression ratios of MDAH 2774 cells were decreased by approximately 50% at this concentration. Topoisomerase II levels were significantly decreased with the increasing concentrations of As(2)O(3). Inhibition of topoisomerase II enzyme was one of the antiproliferative influence mechanisms of As(2)O(3).
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PMID:Arsenic trioxide exposure to ovarian carcinoma cells leads to decreased level of topoisomerase II and cytotoxicity. 1688 64

The performance of immunoassays for the detection of autoantibodies is of critical importance to the diagnosis and assessment of patients with systemic lupus erythematosus (SLE). Our objective was to compare 3 multiplexed assays for measurement of multiple autoantibodies and their association with global disease activity, active nephritis and cumulative organ damage in systemic lupus erythematosus (SLE). Stored sera, clinical and laboratory data from the enrollment visit of a long-term lupus registry were used. Autoantibodies were measured using the BioPlex 2200 ANA screen (Bio-Rad), QuantaPlex ENA8 (INOVA Diagnostics) and recomLine ANA/ENA (Mikrogen). The analytes included dsDNA, chromatin, ribosomal P protein, SS-A/Ro60, Ro52, SS-B/La, Sm, U1-RNP, centromere B, topoisomerase 1 and Jo-1 (histidyl tRNA synthetase). Global SLE disease activity was measured by the SLE disease activity index (SLEDAI) and cumulative organ damage by the SLICC/ACR damage index (SDI). One hundred ninety two patients (87% female; 91% Caucasian; mean disease duration 8.8years) were studied. Agreement between the 3 assays varied from 70% to 99% (Cohen's kappa: 0.04-0.88). There were significant associations between SLEDAI scores (excluding anti-dsDNA) and ANA (INOVA, Mikrogen), anti-dsDNA (Bio-Rad, Mikrogen), anti-chromatin (Bio-Rad, INOVA), anti-Ro (Mikrogen), anti-Sm and anti-U1-RNP (all 3 immunoassays) (p=0.002-0.05). Concurrent lupus nephritis was associated with anti-dsDNA (Bio-Rad (p=0.017) or Bio-Rad and Mikrogen together (p=0.015)). There was no significant association between autoantibodies and SDI scores. The overall agreement between assays for the detection of autoantibodies was reasonable. The greatest discordance (70-83%) occurred with those autoantibodies most strongly associated with global SLE disease activity (ANA, anti-dsDNA, anti-chromatin and anti-Sm). Furthermore, there were differences between assays in their associations with global SLE disease activity and lupus nephritis.
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PMID:Comparison between multiplex assays for autoantibody detection in systemic lupus erythematosus. 2043 30