Many viral oncogenes encode protein—yrosine kinase activities. However, important in vivo substrates of these enzymes have yet to be identified. Recently, type I topoisomerases were shown to be in vitro substrates for two tyrosine kinases. Following tyrosine phosphorylation, topoisomerase I activity was reduced 10-fold (Tse-Dinh et al. Nature312:785–786, 1984). To determine whether topoisomerase I activity was modulated by tyrosine phosphorylation in vivo, we have measured topoisomerase I activity in nuclear lysates prepared from both normal fibroblasts and cells transformed by two different viral oncogenes (v-abl, v-src). Under a variety of experimental conditions, we have found no evidence to support the notion that type I topoisomerase activity is modulated by tyrosine phosphorylation in vivo.
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March 01 1986
A comparison of topoisomerase I activity in normal and transformed cells
W. H. Colledge;
W. H. Colledge
1Laboratory of Eukaryotic Molecular Genetics, National Institute of Medical Research, London, NW7 1AA, UK
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M. Edge;
M. Edge
2ICI Pharmaceuticals Division, Alderley Park, Macclesfield, Cheshire, SK10 4TG, UK
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J. G. Foulkes
J. G. Foulkes
1Laboratory of Eukaryotic Molecular Genetics, National Institute of Medical Research, London, NW7 1AA, UK
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Publisher: Portland Press Ltd
Received:
February 10 1986
Online ISSN: 1573-4935
Print ISSN: 0144-8463
© 1986 Plenum Publishing Corporation
1986
Biosci Rep (1986) 6 (3): 301–307.
Article history
Received:
February 10 1986
Citation
W. H. Colledge, M. Edge, J. G. Foulkes; A comparison of topoisomerase I activity in normal and transformed cells. Biosci Rep 1 March 1986; 6 (3): 301–307. doi: https://doi.org/10.1007/BF01115159
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