Murine transgenic cell lines lacking DNA topoisomerase II (topo II)beta have been used to assess the importance of topo IIbeta as a drug target. Western blot analysis confirmed that the topo IIbeta -/- cell lines did not contain topo IIbeta protein. In addition, both the topo IIbeta +/+ and topo IIbeta -/- cell lines contained similar levels of topo IIalpha protein. The trapped in agarose DNA i...

Topoisomerase (topo) IIα and IIβ maintain genome stability and are targets for anti-tumor drugs. In this study, we demonstrate that the decatenation checkpoint is regulated, not only by topo IIα, as previously reported, but also by topo IIβ. The decatenation checkpoint is most efficient when both isoforms are present. Regulation of this checkpoint and sensitivity to topo II-targeted drugs is in...

Type II DNA topoisomerase (topo II) is required for diverse biological functions including DNA replication, maintenance of genome stability, chromosome segregation and chromosome condensation. While the identity of topo II in rodent testis has been established, the regulation of topo II expression during the development of the postnatal testis and gametogenesis is unclear. Here, we report that ...

DNA topoisomerases (topos) are essential enzymes that participate in many cellular processes involving DNA. The presence of the DNA-gyrase genes in various mycoplasmas has been reported elsewhere. However, the characterization of DNA topo activity in mycoplasmas has not been previously undertaken. In this study, we characterized the topo activity in extracts of Mycoplasma fermentans K7 and inco...

Cellular DNA topoisomerases (topo I and topo II) are highly conserved enzymes that regulate the topology of DNA during normal genome transactions, such as DNA transcription and replication. In budding yeast, topo I is dispensable whereas topo II is essential, suggesting fundamental and exclusive roles for topo II, which might include the functions of the topo IIa and topo IIb isoforms found in ...

BACKGROUND The condensed state of the human sperm's chromatin is essential for the compact structure of the spermatozoon head, which is important for the fertilization process. The enzymes DNA topoisomerases (topo I and topo II) are responsible for the topological structure of the chromatin in somatic cells. The activities and the characterization of topoisomerases in mature human sperm cells h...

Pyrazoloacridine (PA), an acridine congener with an unknown mechanism of action, has shown selective activity against solid tumor cells, cytotoxicity in noncycling and hypoxic cells, and promising antitumor activity in Phase I clinical trials. In the present study, the effect of PA on topoisomerase (topo) activity was evaluated using yeast strains lacking functional topo I or II, mammalian cell...

We related cellular content of DNA topoisomerase (topo) IIalpha and IIbeta with the cell cycle position in proliferating, differentiated, and apoptotic HL-60 cells using two-dimensional flow cytometry. In logarithmically growing HL-60 cells, topo IIalpha increased especially in late S to G2/M phases, although the topo IIbeta level was almost constant throughout the cell cycle. Induction of diff...

DNA topoisomerases I and II (topo I and II) are nuclear enzymes involved in cellular replication and are targets for several anticancer drugs. We showed previously that E1A gene transfer enhanced the sensitivity of Ewing's sarcoma cells to the topo IIalpha targeting agents etoposide and Adriamycin in vitro and in vivo. To determine whether this effect was specific for topo IIalpha, we investiga...