1. Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109 (T.C., B.J.T., R.T., M.N.S., C.M.M., S.H.);
2. Department of Botany, University of Washington, Seattle, Washington 98195 (S.R., L.C.); and
3. Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111 (A.T.Y.)