Molecular Biology Reports

, Volume 14, Issue 1, pp 35–39

Role of calf thymus DNA-Topoisomerase I phosphorylation on relaxation activity expression and on DNA-protein interaction

Role of DNA-Topoisomerase I phosphorylation
  • S. Coderoni
  • M. Paperelli
  • G. L. Gianfranceschi


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:
  • - the native protein is partially phosphorylated,

  • - the phosphorylation involvement is essential for the activity expression and also for DNA-protein interaction,

  • - 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.

Key words

DNA-protein interaction phosphorylation/dephosphorylation Topoisomerase I 





dimethyl sulfoxide




poly acrylamide gel electrophoresis


sodium dodecyl sulfate

Topo I

Topoisomerase I


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Copyright information

© Kluwer Academic Publishers 1990

Authors and Affiliations

  • S. Coderoni
    • 1
  • M. Paperelli
    • 1
  • G. L. Gianfranceschi
    • 2
  1. 1.Department of Cell BiologyUniversity of CamerinoCamerino (MC)Italy
  2. 2.Institute of Cell BiologyUniversity of PerugiaPerugiaItaly

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