Abstract
Induction of checkpoint responses in G1, S, and G2 phases of the cell cycle after exposure of cells to ionizing radiation (IR) is essential for maintaining genomic integrity. Ataxia telangiectasia mutated (ATM) plays a key role in initiating this response in all three phases of the cell cycle. However, cells lacking functional ATM exhibit a prolonged G2 arrest after IR, suggesting regulation by an ATM-independent checkpoint response. The mechanism for this ataxia telangiectasia (AT)-independent G2-checkpoint response remains unknown. We report here that the G2 checkpoint in irradiated human AT cells derives from an overactivation of the ATR/CHK1 pathway. Chk1 small interfering RNA abolishes the IR-induced prolonged G2 checkpoint and radiosensitizes AT cells to killing. These results link the activation of ATR/CHK1 with the prolonged G2 arrest in AT cells and show that activation of this G2 checkpoint contributes to the survival of AT cells.
Publication types
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Alkaloids / pharmacology
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Ataxia Telangiectasia Mutated Proteins
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Caffeine / pharmacology
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Cell Cycle Proteins / antagonists & inhibitors
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Cell Cycle Proteins / metabolism*
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Cell Line, Transformed
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Cell Survival / physiology
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Cell Survival / radiation effects
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Checkpoint Kinase 1
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Enzyme Inhibitors / pharmacology
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Fibroblasts / cytology*
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Fibroblasts / metabolism
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Fibroblasts / radiation effects
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G2 Phase / physiology
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G2 Phase / radiation effects*
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Humans
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Phosphodiesterase Inhibitors / pharmacology
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Protein Kinase Inhibitors
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Protein Kinases / genetics
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Protein Kinases / metabolism*
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Protein Serine-Threonine Kinases*
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RNA, Small Interfering
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Radiation, Ionizing
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Staurosporine / analogs & derivatives
Substances
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Alkaloids
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Cell Cycle Proteins
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Enzyme Inhibitors
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Phosphodiesterase Inhibitors
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Protein Kinase Inhibitors
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RNA, Small Interfering
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Caffeine
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7-hydroxystaurosporine
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Protein Kinases
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ATR protein, human
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Ataxia Telangiectasia Mutated Proteins
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CHEK1 protein, human
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Checkpoint Kinase 1
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Protein Serine-Threonine Kinases
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Staurosporine