Purification and characterization of human DNA topoisomerase IIIalpha.

Human topoisomerase IIIalpha (hTopo IIIalpha), the recently identified first member of the topoisomerase IA subfamily in humans, has a central domain which is highly homologous to the yeast topoisomerase III, but an overall organization closer to that of Escherichia coli DNA topoisomerase I. In order to determine the properties of hTopo IIIalpha, compared to those of other topoisomerase IA subfamily members, we purified this enzyme to near homogeneity, together with an active site-mutant Y337F. We show that hTopo IIIalpha is able to relax negatively supercoiled DNA in a distributive manner, leading to the total disappearance of the initial substrate and the appearance of intermediate topoisomers.

Effects of two distamycin-ellipticine hybrid molecules on topoisomerase I and II mediated DNA cleavage: relation to cytotoxicity.

Two distamycin-ellipticine conjugates were examined for their ability to modulate topoisomerase I and topoisomerase II-DNA cleavable complex formation in vitro. Hybrid molecules Distel (1+) and Distel (2+) both contain a DNA-intercalating chromophore and a tris-pyrrole element capable of binding within the minor groove of DNA. The two drugs differ only in the nature of the side chain attached to the distamycin moiety.

Intoplicine (RP 60475) and its derivatives, a new class of antitumor agents inhibiting both topoisomerase I and II activities.

Intoplicine (RP 60475, NSC 645008) is an antitumor derivative in the 7H-benzo[e]pyrido[4,3-b]indole series which is now being tested in clinical trials. Intoplicine strongly binds DNA (KA = 2 x 10(5) M-1) and thereby increases the length of linear DNA. These properties are consistent with DNA unwinding by intoplicine.

The antileukemic alkaloid fagaronine is an inhibitor of DNA topoisomerases I and II.

The antileukemic alkaloid, fagaronine, is a potent differentiation inducer of various hematopoietic cell lines. We show here that fagaronine is a DNA base-pair intercalator with a K(app) of 2.1 x 10(5) M-1 for calf thymus DNA.

Altered topoisomerase I activity and recombination activating gene expression in a human leukemia cell line resistant to doxorubicin.

We examined the expression of the genes encoding topoisomerases I and II and those associated with V(D)J [variable(diversity)joining] recombination in two human T-cell acute lymphoblastic leukemia (T.ALL) cell lines, CEM and CEM/DOX. In CEM/DOX cells, which are resistant to doxorubicin, the topoisomerase I gene was found to be 4-fold overexpressed and nuclear topoisomerase I relaxation activity was 2-fold greater in CEM/DOX than in CEM cells.