title: Casein kinase II stimulates Xenopus laevis DNA topoisomerase I by physical association.
abstract: A Xenopus laevis casein kinase II-like activity copurified with X. laevis DNA topoisomerase I activity during chromatography on DEAE-cellulose, phosphocellulose, and hydroxylapatite, but the two activities were resolved by chromatography on DNA-agarose [Kaiserman, H. B., Ingebritsen, T. S., & Benbow, R. M. (1988) Biochemistry 27, 3216-3222]. Phosphorylation of the catalytic polypeptides of dephosphorylated X. laevis DNA topoisomerase I by the endogenous X. laevis casein kinase II-like activity apparently resulted in a severalfold increase in catalytic activity. In this study, we show that incubation of purified X. laevis DNA topoisomerase I with electrophoretically homogeneous bovine brain casein kinase II and ATP strongly stimulated catalytic activity. Surprisingly, purified bovine casein kinase II stimulated X. laevis DNA topoisomerase I activity by more than an order of magnitude in the absence of ATP, although ATP resulted in additional stimulation. Other basic proteins, such as histone H1 and HMG proteins, also stimulated X. laevis DNA topoisomerase I catalytic activity 2-3-fold in the absence of ATP. Modulation of catalytic activity by direct physical association (protein-protein interactions) must, therefore, be considered in addition to phosphorylation in assessing the physiological role of casein kinase II and other basic proteins during regulation of X. laevis DNA topoisomerase I activity in vivo.
authors.affiliation: Department of Zoology and Genetics, Iowa State University, Ames 50011-3223.
authors.forename: G J
authors.initials: GJ
authors.lastname: Kordiyak
authors.forename: S
authors.initials: S
authors.lastname: Jakes
authors.forename: T S
authors.initials: TS
authors.lastname: Ingebritsen
authors.forename: R M
authors.initials: RM
authors.lastname: Benbow
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001923:Brain Chemistry; D047390:Casein Kinase II; D002417:Cattle; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D006609:High Mobility Group Proteins / Q000378:metabolism / Q000494:pharmacology; D006657:Histones / Q000378:metabolism / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D014982:Xenopus laevis / Q000378:metabolism
chemical_list: D006609:High Mobility Group Proteins; D006657:Histones; D000255:Adenosine Triphosphate; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D004264:DNA Topoisomerases, Type I