title: Active heterodimers are formed from human DNA topoisomerase II alpha and II beta isoforms.
abstract: DNA topoisomerase II is a nuclear enzyme essential for chromosome dynamics and DNA metabolism. In mammalian cells, two genetically and biochemically distinct topoisomerase II forms exist, which are designated topoisomerase II alpha and topoisomerase II beta. In our studies of human topoisomerase II, we have found that a substantial fraction of the enzyme exists as alpha/beta heterodimers in HeLa cells. The ability to form heterodimers was verified when human topoisomerases II alpha and II beta were coexpressed in yeast and investigated in a dimerization assay. Analysis of purified heterodimers shows that these enzymes maintain topoisomerase II specific catalytic activities. The natural existence of an active heterodimeric subclass of topoisomerase II merits attention whenever topoisomerases II alpha and II beta function, localization, and cell cycle regulation are investigated.
authors.affiliation: Department of Molecular and Structural Biology, University of Aarhus, Denmark.
authors.forename: H
authors.initials: H
authors.lastname: Biersack
authors.forename: S
authors.initials: S
authors.lastname: Jensen
authors.forename: I
authors.initials: I
authors.lastname: Gromova
authors.forename: I S
authors.initials: IS
authors.lastname: Nielsen
authors.forename: O
authors.initials: O
authors.lastname: Westergaard
authors.forename: A H
authors.initials: AH
authors.lastname: Andersen
mesh_terms: D000595:Amino Acid Sequence; D002384:Catalysis; D002467:Cell Nucleus / Q000201:enzymology; D004264:DNA Topoisomerases, Type I / Q000737:chemistry* / Q000276:immunology / Q000302:isolation & purification; D006367:HeLa Cells; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000276:immunology; D011233:Precipitin Tests; D011485:Protein Binding; D011994:Recombinant Proteins; D012441:Saccharomyces cerevisiae; D013329:Structure-Activity Relationship
chemical_list: D007527:Isoenzymes; D046911:Macromolecular Substances; D010455:Peptides; D011994:Recombinant Proteins; D004264:DNA Topoisomerases, Type I