title: Role of tyrosine phosphorylation in radiation-induced cell cycle-arrest of leukemic B-cell precursors at the G2-M transition checkpoint.
abstract: Here we provide experimental evidence that ionizing radiation induces inhibitory tyrosine phosphorylation of the p34cdc2 kinase in human leukemic B-cell precursors. Herbimycin A markedly reduced tyrosine phosphorylation of p34cdc2 in irradiated leukemic B-cell precursors, thereby preventing radiation-induced cell cycle arrest at the G2-M transition checkpoint. Thus, tyrosine phosphorylation is directly responsible for the inactivation of p34cdc2 in irradiated human leukemic B-cell precursors and activation of protein tyrosine kinases is a proximal and mandatory step in radiation-induced G2-arrest arrest at the G2-M checkpoint. Human WEE1 kinase isolated from unirradiated or irradiated leukemic B-cell precursors had minimal tyrosine kinase activity towards p34cdc2. We detected no increase of human WEE1 kinase activity after radiation of leukemic B-cell precursors, as measured by (a) autophosphorylation, (b) tyrosine phosphorylation of a synthetic peptide derived from the p34cdc2 amino-terminal region or (c) recombinant human p34cdc2-cyclin B complex. Thus the signaling pathway leading to inhibitory tyrosine phosphorylation of p34cdc2 and G2-arrest in irradiated human leukemic B-cell precursors functions independent of p49 WEE1 HU and enzymes which augment the tyrosine kinase activity of p49 WEE 1HU.
authors.affiliation: Department of Therapeutic Radiology-Radiation Oncology, University of Minnesota Health Sciences Center, Minneapolis, USA.
authors.forename: L
authors.initials: L
authors.lastname: Tuel-Ahlgren
authors.forename: X
authors.initials: X
authors.lastname: Jun
authors.forename: K G
authors.initials: KG
authors.lastname: Waddick
authors.forename: J
authors.initials: J
authors.lastname: Jin
authors.forename: J
authors.initials: J
authors.lastname: Bolen
authors.forename: F M
authors.initials: FM
authors.lastname: Uckun
mesh_terms: D001402:B-Lymphocytes / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D016227:Benzoquinones; D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018797:Cell Cycle Proteins; D004789:Enzyme Activation / Q000528:radiation effects; D016195:G2 Phase / Q000528:radiation effects*; D006412:Hematopoietic Stem Cells / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D006801:Humans; D047029:Lactams, Macrocyclic; D046911:Macromolecular Substances; D016200:Maturation-Promoting Factor / Q000502:physiology; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D009687:Nuclear Proteins; D010446:Peptide Fragments / Q000378:metabolism; D010766:Phosphorylation / Q000528:radiation effects; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000201:enzymology / Q000473:pathology*; D011499:Protein Processing, Post-Translational / Q000528:radiation effects*; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D011809:Quinones / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017828:Rifabutin / Q000031:analogs & derivatives; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism
chemical_list: D016227:Benzoquinones; D018797:Cell Cycle Proteins; D047029:Lactams, Macrocyclic; D046911:Macromolecular Substances; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D011809:Quinones; D011993:Recombinant Fusion Proteins; D017828:Rifabutin; D014443:Tyrosine; C020754:herbimycin; D011505:Protein-Tyrosine Kinases; C499349:WEE1 protein, human; D016203:CDC2 Protein Kinase; D016200:Maturation-Promoting Factor