1. Laboratory of Chromatin Structure and Function, Institute for Quantitative Biosciences, The University of Tokyo , 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
2. Department of Biological Sciences, Graduate School of Science, The University of Tokyo , 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
3. School of Life Science and Technology, Tokyo Institute of Technology , 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan