DNA-Dependent Protein Kinase and Ataxia Telangiectasia Mutated (ATM) Promote Cell Survival in Response to NK314, a Topoisomerase IIα Inhibitor

The DNA-dependent protein kinase (DNA-PK) is composed of a DNA-dependent protein kinase catalytic subunit (DNA-PKcs) and Ku70/Ku80 heterodimer. DNA-PK is thought to act as the “sensor” for DNA double-stranded breaks (DSB), which are considered the most deleterious type of DNA damage. In particular, DNA-PKcs and Ku are shown to be essential for DSB repair through nonhomologous end joining (NHEJ). The phenotypes of animals and human individuals with defective DNA-PKcs or Ku functions indicate their essential roles in these developments, especially in neuronal and immune systems. DNA-PKcs are structurally related to Ataxia–telangiectasia mutated (ATM), which is also implicated in the cellular responses to DSBs. DNA-PKcs and ATM constitute the phosphatidylinositol 3-kinase-like kinases (PIKKs) family with several other molecules. Here, we review the accumulated knowledge on the functions of DNA-PKcs, mainly based on the phenotypes of DNA-PKcs-deficient cells in animals and human individuals, and also discuss its relationship with ATM in the maintenance of genomic stability.

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Defective regulation of Ca2+ /calmodulin-dependent protein kinase II in γ-irradiated ataxia telangiectasia fibroblasts

FEBS Letters ◽

10.1016/s0014-5793(99)00664-x ◽

1999 ◽

Vol 453 (1-2) ◽

pp. 183-186 ◽

Cited By ~ 6

Author(s):

Konrad S Famulski ◽

Malcolm C Paterson

Keyword(s):

Protein Kinase ◽

Ataxia Telangiectasia ◽

Dependent Protein Kinase ◽

Protein Kinase Ii ◽

Dependent Protein

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Characterization of ATM Expression, Localization, and Associated DNA-dependent Protein Kinase Activity

Molecular Biology of the Cell ◽

10.1091/mbc.9.9.2361 ◽

1998 ◽

Vol 9 (9) ◽

pp. 2361-2374 ◽

Cited By ~ 120

Author(s):

Dennis P. Gately ◽

James C. Hittle ◽

Gordon K. T. Chan ◽

Tim J. Yen

Keyword(s):

Dna Damage ◽

Protein Kinase ◽

Ataxia Telangiectasia ◽

Kinase Activity ◽

Human Fibroblasts ◽

Protein Kinase Activity ◽

Dependent Manner ◽

Dependent Protein Kinase ◽

Dependent Protein ◽

Atm Protein

Ataxia telangiectasia–mutated gene (ATM) is a 350-kDa protein whose function is defective in the autosomal recessive disorder ataxia telangiectasia (AT). Affinity-purified polyclonal antibodies were used to characterize ATM. Steady-state levels of ATM protein varied from undetectable in most AT cell lines to highly expressed in HeLa, U2OS, and normal human fibroblasts. Subcellular fractionation showed that ATM is predominantly a nuclear protein associated with the chromatin and nuclear matrix. ATM protein levels remained constant throughout the cell cycle and did not change in response to serum stimulation. Ionizing radiation had no significant effect on either the expression or distribution of ATM. ATM immunoprecipitates from HeLa cells and the human DNA-dependent protein kinase null cell line MO59J, but not from AT cells, phosphorylated the 34-kDa subunit of replication protein A (RPA) complex in a single-stranded and linear double-stranded DNA–dependent manner. Phosphorylation of p34 RPA occurred on threonine and serine residues. Phosphopeptide analysis demonstrates that the ATM-associated protein kinase phosphorylates p34 RPA on similar residues observed in vivo. The DNA-dependent protein kinase activity observed for ATM immunocomplexes, along with the association of ATM with chromatin, suggests that DNA damage can induce ATM or a stably associated protein kinase to phosphorylate proteins in the DNA damage response pathway.

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