1. N. S. Duesbery, C. P. Webb, T. D. Copeland, M. K. Oskarsson, G. F. Vande Woude, Advanced BioScience Laboratories–Basic Research Program, National Cancer Institute–Frederick Cancer Research and Development Center, Post Office Box B, Frederick, MD 21702, USA.
2. S. H. Leppla, V. M. Gordon, K. R. Klimpel, National Institute of Dental Research–National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA.
3. N. G. Ahn, Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of Colorado, Campus Box 215, Boulder, CO 80309, USA.
4. K. Fukasawa, Department of Cell Biology, University of Cincinnati, College of Medicine, P.O. Box 670521, Cincinnati, OH 45267, USA.
5. K. D. Paull, Division of Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.