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

We have characterized the topoisomerase I and II activities in nuclear extracts from immature embryos of Zea mays and the effect of the treatment with 2,4-dichlorophenoxyacetic acid (2,4-D) and abscisic acid (ABA). These extracts were shown to be essentially devoid of protease and nuclease activities and they were tested for their ability to relax supercoiled DNA, unknotting P4 DNA and catenate circular duplex DNA under catalytic conditions. Unknotting and catenation reactions are strictly magnesium- and ATP-dependent, but not the relaxation of circular supercoiled DNA allowing the detection of both topoisomerase I and II activities. Two cytotoxic drugs, camptothecin, a plant alkaloid that inhibits eukaryotic topoisomerase I, and epipodophyllotoxin VM-26 (teniposide) that inhibits topoisomerase II, have been assayed in our extracts showing similar inhibitory effects on topoisomerase enzymes. Alkaline phosphatase treatment of nuclear extracts abolishes both topoisomerase activities. Nuclear extracts from embryos treated with 2,4-D showed 200% increase on topoisomerase II activity as compared with untreated ones, but only residual activity was detected in ABA-treated embryos. Nuclear extracts from hormone-treated and untreated embryos showed similar topoisomerase I activity with deviations of less than 25%. These differences are discussed in terms of possible post-translational modifications of the enzymes associated with the increase in proliferation activity of calli.
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PMID:Characterization of topoisomerase I and II activities in nuclear extracts during callogenesis in immature embryos of Zea mays. 165 30

The spatial expression of carrot (Daucus carota L.) top1 genes encoding the two isoforms of the enzyme DNA topoisomerase I (EC 5.99.1.2) was investigated. In situ hybridization analysis performed with a probe recognizing both top1 transcripts provided evidence that in explanted hypocotyls induced to proliferate in vitro by the addition of the growth regulator 2,4-dichlorophenoxyacetic acid (2,4-D), the mRNA accumulation parallels the proliferation of provascular cells of the stelar cylinder. During somatic embryogenesis, the histological distribution of top1 transcripts was strongly evident at the stage of torpedo-shaped embryos, but gene expression was not only restricted to meristematic regions. When the spatial localization was extended to carrot vegetative apices and the investigation was carried out with specific probes for top1alpha and top1beta, both transcripts preferentially accumulated in tissues having mitotic activity.
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PMID:Spatial expression of DNA topoisomerase I genes during cell proliferation in Daucus carota. 1141 62