1. Molecular Cell Physiology Bielefeld University D‐33615 Bielefeld Germany
2. Institute for Genome Research and Systems Biology CeBiTec Bielefeld University D‐33615 Bielefeld Germany
3. Institut de Biologie de L'Ecole Normale Supérieure (IBENS) 46 Rue d'Ulm 75230 Paris Cedex 05 France