1. Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA.
2. Division of Signal Transduction, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02115, USA.
3. Peptide Biology Laboratories, The Salk Institute, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
4. Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon 440-746, Korea.
5. Massachusetts General Hospital Cancer Center, Massachusetts General Hospital, 185 Cambridge Street, Boston, MA 02114, USA.