Regulation of DNA-dependent protein kinase activity by ionizing radiation-activated abl kinase is an ATM-dependent process.
Ionizing radiation (IR) treatment results in activation of the nonreceptor tyrosine kinase c-Abl because of phosphorylation by ATM. In vitro evidence indicates that DNA-dependent protein kinase (DNA-PK) can also phosphorylate and thus potentially activate Abl kinase activity in response to IR exposure. To unravel the role of ATM and DNA-PK in the activation of Abl, we assayed Abl, ATM, and DNA-PK activity in ATM- and DNA-PKcs-deficient cells after irradiation. Our results show that despite the presence of higher than normal levels of DNA-PK kinase activity, c-Abl fails to become activated after IR exposure in ATM-deficient cells. Conversely, normal activation of both ATM and c-Abl occurs in DNA-PKcs-deficient cells, indicating that ATM but not DNA-PK is required for activation of Abl in response to IR treatment. Moreover, activation of Abl kinase activity by IR correlates well with activation of ATM activity in all phases of the cell cycle. These results indicate that ATM is primarily responsible for activation of Abl in response to IR exposure in a cell cycle-independent fashion. Examination of DNA-PK activity in response to IR treatment in Abl-deficient cells expressing mutant forms of Abl or in normal cells exposed to an inhibitor of Abl suggests an in vivo role for Abl in the down-regulation of DNA-PK activity. Collectively, these results suggest a convergence of the ATM and DNA-PK pathways in the cellular response to IR through c-Abl kinase.
Shangary
S
S
Department of Molecular Genetics and Biochemistry and the Department of Pharmacology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15261, USA.
Brown
K D
KD
Adamson
A W
AW
Edmonson
S
S
Ng
B
B
Pandita
T K
TK
Yalowich
J
J
Taccioli
G E
GE
Baskaran
R
R
D000818:Animals; D001260:Ataxia Telangiectasia / Q000378:metabolism*; D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins; D004249:DNA Damage; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D004789:Enzyme Activation; D005720:Gamma Rays; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D051379:Mice; D009687:Nuclear Proteins; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D016315:Proto-Oncogene Proteins c-abl / Q000528:radiation effects*; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D025521:Tumor Suppressor Proteins; D016315:Proto-Oncogene Proteins c-abl; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases