1. Department of Biology,
2. Protein & Peptide Group, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69012 Heidelberg, Germany.
3. Department of Molecular, Cellular and Developmental Biology, Yale University, Post Office Box 208104, New Haven, CT 06520, USA.
4. Department of Cancer Cell Biology, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA.
5. Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125, USA.