DNA protein kinase-dependent G2 checkpoint revealed following knockdown of ataxia-telangiectasia mutated in human mammary epithelial cells. 2008

Sonnet J H Arlander, and Bryan T Greene, and Cynthia L Innes, and Richard S Paules
Environmental Stress and Cancer Group, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, North Carolina 27709, USA.

Members of the phosphatidylinositol 3-kinase-related kinase family, in particular the ataxia-telangiectasia mutated (ATM) kinase and the catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs), regulate cellular responses to DNA double-strand breaks. Increased sensitivity to ionizing radiation (IR) in DNA-PKcs- or ATM-deficient cells emphasizes their important roles in maintaining genome stability. Furthermore, combined knockout of both kinases is synthetically lethal, suggesting functional complementarity. In the current study, using human mammary epithelial cells with ATM levels stably knocked down by >90%, we observed an IR-induced G(2) checkpoint that was only slightly attenuated. In marked contrast, this G(2) checkpoint was significantly attenuated with either DNA-PK inhibitor treatment or RNA interference knockdown of DNA-PKcs, the catalytic subunit of DNA-PK, indicating that DNA-PK contributes to the G(2) checkpoint in these cells. Furthermore, in agreement with the checkpoint attenuation, DNA-PK inhibition in ATM-knockdown cells resulted in reduced signaling of the checkpoint kinase CHK1 as evidenced by reduced CHK1 phosphorylation. Taken together, these results show a DNA-PK-dependent component to the IR-induced G(2) checkpoint, in addition to the well-defined ATM-dependent component. This may have important implications for chemotherapeutic strategies for breast cancers.

UI MeSH Term Description Entries
D009154 Mutation Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations. Mutations
D009687 Nuclear Proteins Proteins found in the nucleus of a cell. Do not confuse with NUCLEOPROTEINS which are proteins conjugated with nucleic acids, that are not necessarily present in the nucleus. Nucleolar Protein,Nucleolar Proteins,Nuclear Protein,Protein, Nuclear,Protein, Nucleolar,Proteins, Nuclear,Proteins, Nucleolar
D010766 Phosphorylation The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety. Phosphorylations
D011494 Protein Kinases A family of enzymes that catalyze the conversion of ATP and a protein to ADP and a phosphoprotein. Protein Kinase,Kinase, Protein,Kinases, Protein
D011836 Radiation Tolerance The ability of some cells or tissues to survive lethal doses of IONIZING RADIATION. Tolerance depends on the species, cell type, and physical and chemical variables, including RADIATION-PROTECTIVE AGENTS and RADIATION-SENSITIZING AGENTS. Radiation Sensitivity,Radiosensitivity,Sensitivity, Radiation,Tolerance, Radiation,Radiation Sensitivities,Radiation Tolerances,Radiosensitivities,Sensitivities, Radiation,Tolerances, Radiation
D001761 Bleomycin A complex of related glycopeptide antibiotics from Streptomyces verticillus consisting of bleomycin A2 and B2. It inhibits DNA metabolism and is used as an antineoplastic, especially for solid tumors. BLEO-cell,Blanoxan,Blenoxane,Bleolem,Bleomicina,Bleomycin A(2),Bleomycin A2,Bleomycin B(2),Bleomycin B2,Bleomycin Sulfate,Bleomycins,Bleomycinum Mack,Bléomycine Bellon,BLEO cell,BLEOcell,Bellon, Bléomycine,Mack, Bleomycinum,Sulfate, Bleomycin
D004268 DNA-Binding Proteins Proteins which bind to DNA. The family includes proteins which bind to both double- and single-stranded DNA and also includes specific DNA binding proteins in serum which can be used as markers for malignant diseases. DNA Helix Destabilizing Proteins,DNA-Binding Protein,Single-Stranded DNA Binding Proteins,DNA Binding Protein,DNA Single-Stranded Binding Protein,SS DNA BP,Single-Stranded DNA-Binding Protein,Binding Protein, DNA,DNA Binding Proteins,DNA Single Stranded Binding Protein,DNA-Binding Protein, Single-Stranded,Protein, DNA-Binding,Single Stranded DNA Binding Protein,Single Stranded DNA Binding Proteins
D004847 Epithelial Cells Cells that line the inner and outer surfaces of the body by forming cellular layers (EPITHELIUM) or masses. Epithelial cells lining the SKIN; the MOUTH; the NOSE; and the ANAL CANAL derive from ectoderm; those lining the RESPIRATORY SYSTEM and the DIGESTIVE SYSTEM derive from endoderm; others (CARDIOVASCULAR SYSTEM and LYMPHATIC SYSTEM) derive from mesoderm. Epithelial cells can be classified mainly by cell shape and function into squamous, glandular and transitional epithelial cells. Adenomatous Epithelial Cells,Columnar Glandular Epithelial Cells,Cuboidal Glandular Epithelial Cells,Glandular Epithelial Cells,Squamous Cells,Squamous Epithelial Cells,Transitional Epithelial Cells,Adenomatous Epithelial Cell,Cell, Adenomatous Epithelial,Cell, Epithelial,Cell, Glandular Epithelial,Cell, Squamous,Cell, Squamous Epithelial,Cell, Transitional Epithelial,Cells, Adenomatous Epithelial,Cells, Epithelial,Cells, Glandular Epithelial,Cells, Squamous,Cells, Squamous Epithelial,Cells, Transitional Epithelial,Epithelial Cell,Epithelial Cell, Adenomatous,Epithelial Cell, Glandular,Epithelial Cell, Squamous,Epithelial Cell, Transitional,Epithelial Cells, Adenomatous,Epithelial Cells, Glandular,Epithelial Cells, Squamous,Epithelial Cells, Transitional,Glandular Epithelial Cell,Squamous Cell,Squamous Epithelial Cell,Transitional Epithelial Cell
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000071877 Checkpoint Kinase 1 A serine/threonine-specific protein kinase which is encoded by the CHEK1 gene in humans. Checkpoint kinase 1 (also known as Chk1) coordinates DNA damage response and cell cycle checkpoint response. Under these conditions, activation of Chk1 results in the initiation of cell cycle checkpoints, cell cycle arrest, DNA repair and cell death, to prevent damaged cells from progressing through the cell cycle. Checkpoint-1 Kinase,Chk1 Kinase,Chk1 Protein Kinase,Protein Kinase, Chk1

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