Stimulation of human DNA topoisomerase II activity by its direct association with the beta subunit of protein kinase CKII

DNA topoisomerase TI copurifies with and is phosphorylated by protein kinas e CKII. In this study, a yeast two-hybrid system was used to investigate th e interaction between human topoisomerase II isozymes and CKII: subunits, T he two-hybrid test clearly showed that both topoisomerase II alpha and II b eta interact with the CKII beta, but not the CKII alpha subunit. The two-hy brid test also demonstrated that topoisomerase ZIP residues 1099-1263 and t opoisomerase II alpha residues 1078-1182 mediate the interaction with the C KII beta subunit, providing evidence that the leucine zipper motif and the major CKII-dependent phosphorylation sites of topoisomerase II are unnecess ary for its physical binding to CKII beta. Furthermore, a DNA relaxation as say demonstrated that the CKII subunit enhances topoisomerase II activity b y physical interaction with topoisomerase II.