*Department of Molecular and Developmental Biology, The Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokane-dai, Minato-ku, Tokyo 108, Japan; tDepartment of Cell Signaling, DNAX Research Institute of Molecular and Cellular Biology, Palo Alto, California 943041104; tDepartment of Cytogenetics, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45, Yushima, Bu...