1. N. D. Perkins, L. K. Felzien, J. C. Betts, K. Leung, G. J. Nabel, Howard Hughes Medical Institute, Departments of Internal Medicine and Biological Chemistry, University of Michigan Medical Center, 4520 MSRB I, 1150 West Medical Center Drive, Ann Arbor, MI 48109, USA.
2. D. H. Beach, Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, Bungtown Road, Cold Spring Harbor, NY 11724, USA.