1. Section of Molecular Carcinogenesis, Institute of Cancer Research, Brookes Lawley Building, Cotswold Road, Sutton, Surrey SM2 5NG, United Kingdom, Division of Molecular Toxicology, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany, and Department of Biochemistry, Charles University, Faculty of Science, Albertov 2030, 128 40 Prague 2, The Czech Republic