DNA TOPOISOMERASE-II AND CASEIN KINASE-II ASSOCIATE IN A MOLECULAR-COMPLEX THAT IS CATALYTICALLY ACTIVE

Immunoprecipitation of DNA topoisomerase II from yeast results in a pr eparation that contains casein kinase II; this suggests that the two p roteins may associate in the intact cell. Purified recombinant topoiso merase II and casein kinase II associate to form a complex in vitro wh ich is stable after topoisomerase II becomes phosphorylated by the kin ase. Studies with isolated recombinant casein kinase II subunits discl osed that although the alpha (catalytic) subunit alone can efficiently phosphorylate topoisomerase II, the formation of a stable topoisomera se II-casein kinase II association requires the presence of the beta s ubunit of the kinase. Both proteins engaged in this complex retain the ir catalytic activities. Naturally occurring polyamines and polyanioni c compounds appear to be crucial factors governing the interaction bet ween the two proteins. Although the biological significance of a stabl e catalytically active topoisomerase II-casein kinase II molecular com plex remains to be defined, these observations suggest the possibility of a novel mechanism regulating topoisomerase II and casein kinase II activities.