Office of Biological and Environmental Research

DOE Low Dose Radiation Program Workshop V

2005 Abstract

Title: Adaptive Response of Mouse Skin Epithelial Cells to Low Dose Ionizing Radiation: Induction of NF-κB, MnSOD, 14-3-3ζ and Cyclin B1

Authors: Jian Jian Li, Kazi M. Ahmed, Ming Fan, Shaozhong Dong, Douglas R. Spitz, and Cheng-Rong Yu

Institutions: Division of Molecular Radiobiology, Purdue University School of Health Sciences, West Lafayette, Indiana; Free Radical and Radiation Biology Program, Department of Radiation Oncology, Holden Comprehensive Cancer Center, The University of Iowa, Iowa City, Iowa; Molecular Immunology Section, Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland

Gene expression profiles demonstrate that a group of key stress-responsive genes are associated with radiation exposure and may contribute to cellular responses to radiation. The present study provides evidence suggesting that the transcription factor NF-κB, the mitochondrial antioxidant MnSOD, and cell-cycle regulatory elements 14-3-3ζ as well as Cyclin B1 are specifically induced in mouse skin JB6 P+ cells by exposure to a single low dose of ionizing radiation (0-20 cGy). In contrast to NF-κB activation, NF-κB subunit p65 protein levels were not altered in irradiated cells, indicating an early response of NF-κB to low dose, radiation-induced stress. Protein levels of MnSOD, 14-3-3ζ and Cyclin B1 were increased as early as 1 hour following radiation (Figure 1) and were maintained for different time periods after radiation. To further investigate the function of low dose induced signaling proteins, fluorescencefusion vectors containing the full-length 14-3-3ζ and Cyclin B1 genes were co-transfected and protein interactions and localization were analyzed with or without radiation. Compared to the known interactions between 14-3-3ζ and GADD45β, interactions between 14-3-3ζ and Cyclin B1 were increased in cells with or without low dose radiation. In addition, the protein complexes containing 14-3-3ζ and Cyclin B1 were found to be translocated into the nucleus (Figure 2) after radiation with different doses, which contrasts to the complexes of 14-3-3ζ and GADD45β that stay in the cytoplasm. Overall, these results demonstrate that a group of pro-survival elements are specifically activated in mouse skin epithelial cells by low dose radiation. Interaction and nuclear translocation of 14-3-3ζ and Cyclin B1 could play a key role in low dose-induced adaptive responses.

Figure 1. MnSOD 14-3-3ζ and Cyclin B1 but not β-Actin proteins were increased in JB6 P+ cells after low dose radiation and Figure 2. The protein complexes in 14-3-3ζ and Cyclin B1 (A) is translocated into the nucleus of JB6 cells 16 hours after 10cGY radiation (B).

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