title: Changes in topoisomerase I levels and localization during myeloid maturation in vitro and in vivo.
abstract: Changes in topoisomerase I (topo I) levels and localization were examined during the course of granulocytic maturation in vitro and in vivo. Western blotting revealed that granulocytic maturation in DMSO-treated HL-60 human leukemia cells was accompanied by a 5-fold decrease in topo I polypeptide content. Consistent with this result, 3- to 5-fold higher concentrations of the topo I poison camptothecin were required to stabilize topo I-DNA adducts in DMSO-treated HL-60 cells compared to untreated cells. Northern blotting revealed that these changes occurred without any decrease in topo I message. Immunolocalization studies revealed that these quantitative changes were accompanied by redistribution of topo I away from the nucleoli, where it was prominently accumulated in untreated HL-60 cells, to a more uniform nuclear distribution in DMSO-treated cells. Similar changes occurred during granulocytic maturation in human marrow in vivo. Western blotting revealed that topo I levels in normal progranulocytes were 50% as high as those in HL-60 cells, levels in metamyelocytes were 35% as high as HL-60 cells, and levels in peripheral blood granulocytes were 5% as high as HL-60 cells. Two other polypeptides that are concentrated in nucleoli, poly(ADP-ribose) polymerase and B23/nucleophosmin, also decreased during the course of granulocytic maturation. These changes were accompanied by an alteration in topo I localization similar to that observed in HL-60 cells during the course of granulocytic maturation. Conversely, treatment of human lymphocytes with the mitogenic lectin concanavalin A resulted in a 3-fold increase in topo I polypeptide content concomitant with a prominent increase in the amount of nucleolar antigen. These observations not only provide a context for understanding the recent observation that topo I levels are higher in human leukemia specimens than in normal marrow but also raise the possibility that elevated topo I levels in other cells might reflect alterations in nucleolar structure and function.
authors.affiliation: Oncology Center, Johns Hopkins Hospital, Baltimore, Maryland.
authors.forename: S H
authors.initials: SH
authors.lastname: Kaufmann
authors.forename: M
authors.initials: M
authors.lastname: Charron
authors.forename: P J
authors.initials: PJ
authors.lastname: Burke
authors.forename: J E
authors.initials: JE
authors.lastname: Karp
mesh_terms: D002467:Cell Nucleus / Q000201:enzymology; D004264:DNA Topoisomerases, Type I / Q000032:analysis*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D006098:Granulocytes / Q000201:enzymology* / Q000502:physiology; D006801:Humans; D007150:Immunohistochemistry; D015473:Leukemia, Promyelocytic, Acute / Q000201:enzymology / Q000473:pathology; D008214:Lymphocytes / Q000201:enzymology
chemical_list: D004264:DNA Topoisomerases, Type I; D004121:Dimethyl Sulfoxide