1. Department of Molecular and Cellular Biology, Institute for Frontier Medical Sciences, Kyoto University, Kyoto 606-8397, Japan.
2. Core Research for Evolutional Science and Technology, Japan Science Technology Agency, Kawaguchi, Saitama 332-0012, Japan.
3. Biochemistry Department, Faculty of Medicine, McGill University, Montréal, Québec H3G 1Y6, Canada.