By altering the accessibility of DNA sequences for alkylation or platination, and/or for subsequent repair, topoisomerase II can potentially affect the level of DNA interstrand cross-links induced in cells by bifunctional agents. In this study, we investigated the extent to which inhibition of topoisomerase II activity in a human glioblastoma multiforme cell line alters the kinetics of both the...

DNA cleavage by eukaryotic type II DNA topoisomerase (EC 5.99.1.3) was strongly inhibited by an oligonucleotide containing 10 dGua residues. Catalytic activities of topoisomerase II, as measured by relaxation and decatenation reactions, were also inhibited by oligo(dG)10. Inhibition was specific to oligo(dG)10; other oligonucleotides, nucleotides, or single-stranded DNAs tested did not influenc...

We have shown previously that quiescent Chinese hamster ovary (CHO) cells are less sensitive than log phase CHO cells to the cytotoxic and DNA cleavage effects of etoposide, a drug which appears to act via DNA topoisomerase II. This loss of sensitivity was associated with a decrease in topoisomerase enzyme activity in nuclear extracts of the quiescent cells. We have now extended our observation...

We have obtained a polyclonal antibody that recognizes a major polypeptide component of chicken mitotic chromosome scaffolds. This polypeptide migrates in SDS PAGE with Mr 170,000. Indirect immunofluorescence and subcellular fractionation experiments confirm that it is present in both mitotic chromosomes and interphase nuclei. Two lines of evidence suggest that this protein is DNA topoisomerase...

DNA topoisomerase II is a homodimeric molecular machine that couples ATP usage to the transport of one DNA segment through a transient break in another segment. In the presence of a nonhydrolyzable ATP analog, the enzyme is known to promote a single turnover of DNA transport. Current models for the enzyme's mechanism based on this result have hydrolysis of two ATPs as the last step, used only t...

Most DNA intercalators and epipodophyllotoxins inhibit mammalian topoisomerase II by trapping the enzyme within DNA cleavage complexes that can be detected in cells as protein-associated DNA strand breaks. We have characterized previously a line of Chinese hamster cells (DC3F/9-OHE cells) the resistance of which to the cytotoxic effect of intercalators and etoposide is associated with a reduced...

A human cDNA encoding a protein homologous to the Escherichia coli DNA topoisomerase I subfamily of enzymes has been identified through cloning and sequencing. Expressing the cloned human cDNA in yeast Atopi cells lacking endogenous DNA topoisomerase I yielded an activity in cell extracts that specifically reduces the number of supercoils in a highly negatively supercoiled DNA. On the basis of ...

Two isoforms of DNA topoisomerase II, and , coded by separate genes, are expressed in actively cycling vertebrate cells. Some previous studies have suggested that only topoisomerase II remains associated with chromosomes at mitosis. Here, the distributions of topoisomerase II and in mitosis were studied by subcellular fractionation and by immunolocalization. Both isoforms of topoisomerase II we...

Etoposide is one of the most successful chemotherapeutic agents used for the treatment of human cancers. The drug kills cells by inhibiting the ability of topoisomerase II to ligate nucleic acids that it cleaves during the double-stranded DNA passage reaction. Etoposide is composed of a polycyclic ring system (rings A-D), a glycosidic moiety at the C4 position, and a pendent ring (E-ring) at th...

The primary cytotoxic mechanism of camptothecin has been proposed to involve an interaction between the replication machinery and the camptothecin-mediated topoisomerase I-DNA cleavable complex (Y. H. Hsiang, M.G. Lihou, and L.F. Liu, Cancer Res., 49:5077-5082, 1989). In the present study, we show that killing of V79 cells by the topoisomerase II poisons 4'-(9-acridinylamino)methanesulfon-m-ani...