Laboratory of DNA Technology, Kazusa DNA Research Institute, 1532-3 Yana, Kisarazu, Chiba 292-0812, Japan. suyama@embl-heidelberg.de|Laboratory of DNA Technology, Kazusa DNA Research Institute, 1532-3 Yana, Kisarazu, Chiba 292-0812, Japan. suyama@embl-heidelberg.de