Transient ATM kinase inhibition disrupts DNA damage-induced sister chromatid exchange.
Cells derived from ataxia telangiectasia (A-T) patients exhibit defective cell cycle checkpoints because of mutations in the gene encoding ATM (ataxia telangiectasia mutated). After exposure to ionizing radiation (IR), A-T cells exhibit sensitivity to IR-induced cellular damage that results in increased chromosome aberrations and cell death (radiosensitivity). ATM is a member of a family of kinases that become activated in response to DNA damage. We showed that even transient inhibition of ATM kinase for 1 hour, initiated 15 minutes after cellular irradiation, resulted in an accumulation of persistent chromosome aberrations and increased cell death. Using reversible inhibitors of DNA-PK (DNA-dependent protein kinase), another kinase involved in responding to DNA damage, and ATM, we showed that these two kinases acted through distinct DNA repair mechanisms: ATM resolved DNA damage through a mechanism involving sister chromatid exchange (SCE), whereas DNA-PK acted through nonhomologous end joining. Furthermore, because DNA damage-induced SCE occurred in A-T fibroblasts that lack functional ATM protein, and the inhibitors of ATM kinase had no effect on DNA damage-induced SCE in A-T fibroblasts, we showed that the consequences of short-term inhibition of the kinase activity of ATM and adaptation to ATM protein disruption were distinct. This suggests that A-T fibroblasts have adapted to the loss of ATM and have alternative mechanisms to initiate SCE.
Department of Radiation Oncology, University of Pittsburgh Medical School, Hillman Cancer Center, Research Pavilion, Suite 2.6, Pittsburgh, PA 15213-1863, USA.
Jason S
JS
White
Serah
S
Choi
Christopher J
CJ
Bakkenist
D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects / Q000528:radiation effects; D002461:Cell Line, Transformed; D002869:Chromosome Aberrations / Q000187:drug effects / Q000528:radiation effects; D002877:Chromosomes, Human / Q000378:metabolism*; D004249:DNA Damage / Q000187:drug effects / Q000528:radiation effects; D051747:DNA-Activated Protein Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D005347:Fibroblasts / Q000201:enzymology*; D005720:Gamma Rays / Q000009:adverse effects*; D006801:Humans; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011836:Radiation Tolerance / Q000187:drug effects / Q000528:radiation effects; D012854:Sister Chromatid Exchange / Q000187:drug effects / Q000528:radiation effects; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D047428:Protein Kinase Inhibitors; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D051747:DNA-Activated Protein Kinase; D017346:Protein Serine-Threonine Kinases