title: ATM regulates ionizing radiation-induced disruption of HDAC1:PP1:Rb complexes.
abstract: Ionizing radiation elicits signaling events that coordinate DNA repair and interruption of cell cycle progression. We previously demonstrated that ionizing radiation (IR) of cells activates nuclear protein phosphatase-1 (PP1) by promoting dephosphorylation of Thr320, an inhibitory site in the enzyme and that the ATM kinase is required for this response. We sought to identify potential targets of IR-activated PP1. Untreated and IR-treated Jurkat cells were labeled with (32)P orthophosphate, and nuclear extracts were subjected to microcystin affinity chromatography to recover phosphatase complexes that were analyzed by 2D-PAGE and mass spectrometry. Several proteins associated with protein phosphatases demonstrated a significant decrease in (32)P intensity following IR, and one of these was identified as HDAC1. Co-immunoprecipitation revealed complexes containing PP1 with HDAC1 and Rb in cell extracts. In response to IR, there was an ATM-dependent activation of PP1, dephosphorylation of HDAC1, dissociation of HDAC1-PP1-Rb complexes and increased HDAC1 activity. These results suggest that IR regulates HDAC1 phosphorylation and activity through ATM-dependent activation of PP1.
authors.affiliation: Department of Radiation Oncology, University of Virginia Health System, Charlottesville, VA 22908, United States.
authors.forename: Changyue
authors.initials: C
authors.lastname: Guo
authors.forename: Jun
authors.initials: J
authors.lastname: Mi
authors.forename: David L
authors.initials: DL
authors.lastname: Brautigan
authors.forename: James M
authors.initials: JM
authors.lastname: Larner
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002461:Cell Line, Transformed; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation / Q000528:radiation effects; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D019169:Jurkat Cells; D052998:Microcystins / Q000494:pharmacology; D008954:Models, Biological; D010749:Phosphoprotein Phosphatases / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011839:Radiation, Ionizing; D016160:Retinoblastoma Protein / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D052998:Microcystins; D016160:Retinoblastoma Protein; D025521:Tumor Suppressor Proteins; C078588:microcystin; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; C110550:HDAC1 protein, human; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases