title: In vivo phosphorylation of the 170-kDa form of eukaryotic DNA topoisomerase II. Cell cycle analysis.
abstract: We have examined the level of incorporation of 32P into DNA topoisomerase II in vivo in chicken lymphoblastoid cells that were fractionated into the various cell cycle phases by centrifugal elutriation. We find that topoisomerase II is phosphorylated in vivo, with the level of incorporation being approximately 3.5-fold higher in the G2 + M fraction than earlier in the cell cycle. Our antibody studies have revealed that topoisomerase II antigen exists as a number of discrete polypeptide species in these cells. Of these, the 170-kDa intact polypeptide is phosphorylated approximately 4.5-fold more than several antigenic fragments that actually comprise the bulk of the topoisomerase II antigen in these cells at mitosis. Phosphorylation of the 170-kDa form of the enzyme may be involved in activation of the enzyme for its role in the disjunction of sister chromatids at anaphase.
authors.affiliation: Department of Cell Biology and Anatomy, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
authors.forename: M M
authors.initials: MM
authors.lastname: Heck
authors.forename: W N
authors.initials: WN
authors.lastname: Hittelman
authors.forename: W C
authors.initials: WC
authors.lastname: Earnshaw
mesh_terms: D000818:Animals; D002453:Cell Cycle; D002460:Cell Line; D002645:Chickens; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D007457:Iodine Radioisotopes; D008970:Molecular Weight; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D011480:Protease Inhibitors / Q000494:pharmacology; D011865:Radioisotope Dilution Technique
chemical_list: D007457:Iodine Radioisotopes; D010761:Phosphorus Radioisotopes; D011480:Protease Inhibitors; D004250:DNA Topoisomerases, Type II