1. Fred Hutchinson Cancer Research Center, Division of Basic Sciences, Seattle, WA, 98109, USA, 2Max F. Perutz Laboratories, University of Vienna, Dr. Bohr-Gasse 9, 1030 Vienna, Austria, 3Cancer Research Institute, Slovak Academy of Sciences, 83391 Bratislava, Slovak Republic 4Department of Genetics, Faculty of Natural Sciences, Comenius University, Mlynska Dolina, 842 15 Bratislava, Slovak Republic