Defective chromatin recruitment and retention of NHEJ core components in human tumor cells expressing a Cyclin E fragment
- Cleveland Clinic, Cleveland, OH (United States). Lerner Research Inst. Dept. of Cancer Biology; Kent State Univ., Kent, OH (United States). School of Biomedical Sciences
- Cleveland Clinic, Cleveland, OH (United States). Lerner Research Inst. Dept. of Cancer Biology
- Cleveland Clinic, Cleveland, OH (United States). Lerner Research Inst. Dept. of Cancer Biology; Cleveland State Univ., Cleveland, OH (United States). Dept. of Chemistry
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Life Sciences Division
- Cleveland Clinic, Cleveland, OH (United States). Lerner Research Inst. Dept. of Cancer Biology; Cleveland Clinic, Cleveland, OH (United States). Taussing Cancer Inst. Dept. of Radiation Oncology
Exposure to genotoxic agents, such as ionizing radiation (IR), produces double-strand breaks, repaired predominantly in mammalian cells by non-homologous end-joining (NHEJ). Ku70 was identified as an interacting partner of a proteolytic Cyclin E (CycE) fragment, p18CycE. p18CycE endogenous generation during IR-induced apoptosis in leukemic cells and its stable expression in epithelial tumor cells sensitized to IR. cH2AX IR-induced foci (IRIFs) and comet assays indicated ineffective NHEJ DNA repair in p18CycE-expressing cells. DNA pull-down and chromatin recruitment assays revealed that retention of NHEJ factors to double strand breaks, but not recruitment, was diminished. Similarly, IRIFs of phosphorylated T2609 and S2056- DNA-PKcs and its target S1778-53BP1 were greatly decreased in p18CycE-expressing cells. As a result, DNA-PKcs chromatin association was also increased. 53BP1 IRIFs were suppressed when p18CycE was generated in leukemic cells and in epithelial cells stably expressing p18CycE. Ataxia telangiectasia mutated was activated but not its 53BP1 and MDC1 targets. These data indicate a profound influence of p18CycE on NHEJ through its interference with DNA-PKcs conformation and/ or dimerization, which is required for effective DNA repair, making the p18CycE-expressing cells more IR sensitive. These studies provide unique mechanistic insights into NHEJ misregulation in human tumor cells, in which defects in NHEJ core components are rare.
- Research Organization:
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER). Biological Systems Science Division
- Grant/Contract Number:
- AC02-05CH11231
- OSTI ID:
- 1625528
- Journal Information:
- Nucleic Acids Research, Vol. 41, Issue 22; ISSN 0305-1048
- Publisher:
- Oxford University PressCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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