1. Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056, Basel, Switzerland
2. Institute of Genetics, University of Cologne, Zülpicher Strasse 47, 50674 Cologne, Germany
3. Max-Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
4. The European Molecular Biology Laboratory, Meyerhofstrasse 1, 67112 Heidelberg, Germany