Phosphorylation of human topoisomerase I by protein kinase C in vitro and in phorbol 12-myristate 13-acetate-activated HL-60 promyelocytic leukaemia cells.
Topoisomerase I was phosphorylated in vitro by protein kinase C (PKC) purified from rat brain with high affinity (Km about 0.1 microM). Tryptic phosphopeptide mapping indicated that two major topoisomerase I peptides phosphorylated in vivo were comigrating with minor peptides phosphorylated by PKC in vitro. Topoisomerase I phosphorylation was stimulated 3-fold in HL-60 cells exposed to the tumour promoter phorbol 12-myristate 13-acetate. The results suggest that topoisomerase I phosphorylation in HL-60 cells is indirectly controlled by PKC.
Department of Pharmacology, Baylor College of Medicine, Houston, TX 77030.
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Cardellini
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Durban
D000818:Animals; D001921:Brain / Q000201:enzymology; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D015473:Leukemia, Promyelocytic, Acute / Q000473:pathology*; D010449:Peptide Mapping; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014357:Trypsin; D014407:Tumor Cells, Cultured
D011493:Protein Kinase C; D014357:Trypsin; D004264:DNA Topoisomerases, Type I; D013755:Tetradecanoylphorbol Acetate