T Cell Mitogens Induce Increased DNA Topoisomerase I Protein Levels and Its Translocation to the Nucleus Where Activation of the Enzyme Occurs Academic Article uri icon


  • Induction of proliferation of human peripheral blood lymphocyte by T cell mitogens was found to be associated with dramatic increase in topoisomerase I DNA relaxing activity in the nuclear, but not in the cytosol, fraction. In addition, cell proliferation was associated with increased DNA topoisomerase I protein levels in both nuclear and cytosol fractions. Inhibitors of T cell proliferation abrogated both topoisomerase I protein levels and enzymatic activity. The results support a model in which cell proliferation is followed by increased DNA topoisomerase I protein levels and translocation of the enzymatically inactive molecule to the nucleus where additional regulatory mechanisms convert it into an active enzyme.

publication date

  • January 1, 1995