Protein kinase C phosphorylates DNA topoisomerase I

D. Scott Samuels, Yoshiko Shimizu, Nobuyoshi Shimizi

Research output: Contribution to journalArticlepeer-review

62 Scopus citations


The induction of mammalian cell proliferation requires the expression of a specific set of genes. Tumor promoters stimulate cell growth by activating the Ca2+ and phospholipid-dependent protein kinase, protein kinase C (PKC). DNA topoisomerase I, a nuclear enzyme involved in transcription, was phosphorylated by activated PKC in vitro. Phosphorylation by PKC stimulated the DNA relaxation activity of topoisomerase I two- to three-fold. Therefore, DNA topoisomerase I is a substrate for PKC-mediated activation by phosphorylation and may serve as a nuclear target of mitogenic signals generated by tumor promoters in vivo.

Original languageEnglish
Pages (from-to)57-60
Number of pages4
JournalFEBS Letters
Issue number1
StatePublished - Dec 18 1989


  • Mitogenic signal transduction
  • Nuclear target
  • Protein kinase C
  • Protein phosphorylation
  • Topoisomerase I, DNA-


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