title: Threonine 68 phosphorylation by ataxia telangiectasia mutated is required for efficient activation of Chk2 in response to ionizing radiation.
abstract: Eukaryotic cells activate an evolutionarily conserved set of proteins that rapidly induce cell cycle arrest to prevent replication or segregation of damaged DNA before repair is completed. In response to ionizing radiation (IR), the cell cycle checkpoint kinase, Chk2 (hCds1), is phosphorylated and activated in an ataxia telangiectasia mutated (ATM)-dependent manner. Here we show that the ATM protein kinase directly phosphorylates T68 within the SQ/TQ-rich domain of Chk2 in vitro and that T68 is phosphorylated in vivo in response to IR in an ATM-dependent manner. Furthermore, phosphorylation of T68 was required for full activation of Chk2 after IR. Together, these data are consistent with the model that ATM directly phosphorylates Chk2 in vivo and that this event contributes to the activation of Chk2 in irradiated cells.
authors.affiliation: Department of Hematology-Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
authors.forename: J Y
authors.initials: JY
authors.lastname: Ahn
authors.forename: J K
authors.initials: JK
authors.lastname: Schwarz
authors.forename: H
authors.initials: H
authors.lastname: Piwnica-Worms
authors.forename: C E
authors.initials: CE
authors.lastname: Canman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins; D064447:Checkpoint Kinase 2; D004268:DNA-Binding Proteins; D004789:Enzyme Activation / Q000528:radiation effects; D005347:Fibroblasts / Q000201:enzymology / Q000528:radiation effects; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009447:Neuroblastoma; D010766:Phosphorylation / Q000528:radiation effects; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D013912:Threonine / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000201:enzymology / Q000528:radiation effects; D025521:Tumor Suppressor Proteins
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; D013912:Threonine; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; C578634:CHEK2 protein, human; C578633:Chek2 protein, mouse; D017346:Protein Serine-Threonine Kinases