1. Department of Biological Responses, Institute for Virus Research, Kyoto University (T.M., J.Y., H.S.), Kyoto 606-8397
2. Department of Obstetrics and Gynecology, Keio University School of Medicine, (T.M., Y.Y.), Tokyo 160-0016
3. the Department of Molecular Biology, Osaka Bioscience Institute (H.S.), Osaka 565-0874, Japan