1. Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan, Laboratory of Molecular Genetics, NICHD, National Institutes of Health, Bethesda, Maryland 20892, and Mitsubishi-Kasei Institute of Life Sciences, 11 Minamiooya, Machida, Tokyo 194-8511, Japan