1. Department of Biological Sciences, Faculty of Science, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512 Japan
2. Department of Genome Repair Dynamics, Radiation Biology Center, Kyoto University, Yoshida-Konoe Cho, Sakyo-ku, Kyoto 606-8501, Japan
3. Department of Radiation Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8553 Japan