title: Phosphorylation of DNA topoisomerase II in vivo and in total homogenates of Drosophila Kc cells. The role of casein kinase II.
abstract: The phosphorylation of DNA topoisomerase II in Drosophila Kc tissue culture cells was characterized by in vivo labeling studies and in vitro studies that examined the modification of exogenous enzyme in total homogenates of these embryonic cells. Several lines of evidence identified casein kinase II as the kinase primarily responsible for phosphorylating DNA topoisomerase II. First, the only amino acyl residue modified in the enzyme was serine. Second, partial proteolytic maps of topoisomerase II which had been labeled with [32P]phosphate by Drosophila cells in vivo, by cell homogenates in vitro, or by purified casein kinase II were indistinguishable from one another. Third, phosphorylation in cell homogenates was inhibited by micrograms/ml concentrations of heparin, micromolar concentrations of nonradioactive GTP, or anti-Drosophila casein kinase II antiserum. Fourth, cell homogenates were able to employ [gamma-32P]GTP as a phosphate donor nearly as well as [gamma-32P]ATP. Although topoisomerase II was phosphorylated in homogenates under conditions that specifically stimulate protein kinase C, calcium/calmodulin-dependent protein kinase, or cAMP-dependent protein kinase, modification was always sensitive to anti-casein kinase II antiserum or heparin. Thus, under a variety of conditions, topoisomerase II appears to be phosphorylated primarily by casein kinase II in the Drosophila embryonic Kc cell system.
authors.affiliation: Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
authors.forename: P
authors.initials: P
authors.lastname: Ackerman
authors.forename: C V
authors.initials: CV
authors.lastname: Glover
authors.forename: N
authors.initials: N
authors.lastname: Osheroff
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D047388:Casein Kinases; D002460:Cell Line; D000242:Cyclic AMP / Q000494:pharmacology; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000196:embryology / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D006160:Guanosine Triphosphate / Q000378:metabolism; D006493:Heparin / Q000494:pharmacology; D007106:Immune Sera / Q000494:pharmacology; D007163:Immunosorbent Techniques; D008970:Molecular Weight; D010446:Peptide Fragments / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000276:immunology / Q000378:metabolism*
chemical_list: D007106:Immune Sera; D010446:Peptide Fragments; D010710:Phosphates; D010768:Phosphoserine; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D006493:Heparin; D000242:Cyclic AMP; D011494:Protein Kinases; D047388:Casein Kinases; D011493:Protein Kinase C; D010447:Peptide Hydrolases; D004250:DNA Topoisomerases, Type II