title: Topoisomerase activity associated with polyoma virus large tumor antigen.
abstract: Polyomavirus (Py) large tumor antigen (LT) was produced in mammalian or insect cells infected with a suitable viral expression vector, and purified by a procedure combining immunoprecipitation with ion-exchange chromatography. Fractions containing the bulk of LT displayed a DNA-relaxing activity (LT-topo) which could be attributed neither to topoisomerase II (topo II) nor to topoisomerase I (topo I) encoded by the cell or the viral vector. On the one hand, LT-topo relaxed pBR322 DNA in a reaction which, unlike that characteristic of topo II, was ATP-independent and inhibited by camptothecin. On the other hand, serum from scleroderma patients which strongly inhibited calf thymus topo I had no effect on LT-topo, which absolutely required Mg2+ ions to relax DNA. Thus, LT-topo is either inherent to LT or belongs to a LT-bound enzyme similar to, but distinct from, topo I.
authors.affiliation: Department of Microbiology, Faculty of Medicine, Université de Sherbrooke, Québec, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Marton
authors.forename: B
authors.initials: B
authors.lastname: Marko
authors.forename: L
authors.initials: L
authors.lastname: Delbecchi
authors.forename: P
authors.initials: P
authors.lastname: Bourgaux
mesh_terms: D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002460:Cell Line; D003001:Cloning, Molecular; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008274:Magnesium / Q000378:metabolism; D018411:Spodoptera; D013950:Thymus Gland / Q000201:enzymology; D014616:Vaccinia virus / Q000201:enzymology
chemical_list: D000952:Antigens, Polyomavirus Transforming; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II; D008274:Magnesium