Abstract
Calf thymus DNA-Topoisomerase I activity was found to be altered by changing in phosphorylation: it was completely inhibited upon dephosphorylation by alkaline phosphatase, but incubation with N II protein kinase and ATP restored the relaxation activity to a level higher than that observed prior to dephosphorylation. The calf thymus Topoisomerase I-mediated DNA cleavage, induced by camptothecin, also proved to be inhibited by dephosphorylation, which, apparently, stabilizes the initial enzymesubstrate complex. We conclude that:
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- the native protein is partially phosphorylated,
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- the phosphorylation involvement is essential for the activity expression and also for DNA-protein interaction,
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- changes in the degree of phosphorylation might be involved in the regulation of DNA processing; that evokes some properties of chromatinic peptide models, which bind DNA only when phosphorylated and leads to the assumption that they represent the minimum functional substrate for N II protein kinase.
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Abbreviations
- CPT:
-
campothecin
- DMSO:
-
dimethyl sulfoxide
- DTT:
-
dithiothreitol
- PAGE:
-
poly acrylamide gel electrophoresis
- SDS:
-
sodium dodecyl sulfate
- Topo I:
-
Topoisomerase I
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Coderoni, S., Paperelli, M. & Gianfranceschi, G.L. Role of calf thymus DNA-Topoisomerase I phosphorylation on relaxation activity expression and on DNA-protein interaction. Mol Biol Rep 14, 35–39 (1990). https://doi.org/10.1007/BF00422713
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DOI: https://doi.org/10.1007/BF00422713