title: Differentiating agents modulate topoisomerase I activity in U-937 promonocytic cells.
abstract: Phorbol 12-myristate 13-acetate (PMA), N,N'-hexamethylenebisacetamide (HMBA) and retinoic acid induce cell differentiation in U-937 promonocytic cells. This report examines the effects of these agents on DNA topoisomerase I activity. A decrease in enzyme activity could be detected as early as 30 min after treatment with all three differentiating compounds and lasted at least 48 h. No alteration in the levels of DNA topoisomerase I transcript or protein was observed during these treatments. The results might be explained by post-translational events that render DNA topoisomerase type I less active.
authors.affiliation: Institute of Biology and Experimental Medicine-CONICET, Buenos Aires, Argentina.
authors.forename: C C
authors.initials: CC
authors.lastname: Shayo
authors.forename: A G
authors.initials: AG
authors.lastname: Mladovan
authors.forename: A
authors.initials: A
authors.lastname: Baldi
mesh_terms: D000081:Acetamides / Q000633:toxicity*; D000970:Antineoplastic Agents / Q000633:toxicity*; D015152:Blotting, Northern; D015153:Blotting, Western; D002273:Carcinogens / Q000633:toxicity*; D002471:Cell Transformation, Neoplastic / Q000187:drug effects; D004264:DNA Topoisomerases, Type I / Q000187:drug effects* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007951:Leukemia, Myeloid / Q000473:pathology; D013755:Tetradecanoylphorbol Acetate / Q000633:toxicity*; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics; D014212:Tretinoin / Q000633:toxicity*; D014407:Tumor Cells, Cultured
chemical_list: D000081:Acetamides; D000970:Antineoplastic Agents; D002273:Carcinogens; D014212:Tretinoin; D004264:DNA Topoisomerases, Type I; C014026:hexamethylene bisacetamide; D013755:Tetradecanoylphorbol Acetate