1. Howard Hughes Medical InstituteDepartment of Molecular Biophysics and BiochemistryYale University School of MedicineNew HavenConnecticut06510USA
2. University of Wisconsin Biotechnology CenterMadisonWisconsin53705USA
3. The Rockefeller UniversityNew YorkNew York10021USA
4. Department of Biological Chemistry and Molecular Biology InstituteUCLA School of MedicineLos AngelesCalifornia90024USA
5. Eastman PharmaceuticalsGreat ValleyPennsylvania19355USA
6. Department of Biological ChemistryUniversity of CaliforniaDavisCalifornia95616USA