1. Department of Biochemistry and Molecular Genetics, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908 1 ;
2. Howard Hughes Medical Institute, Department of Biochemistry and Molecular Biology and The Center for Gene Regulation, The Pennsylvania State University, University Park, Pennsylvania 16802-4500 2 ;
3. Proscript Inc., Cambridge, Massachusetts 01890 3 ;
4. Department of Microbiology and Immunology, Baylor College of Medicine, Houston, Texas 77030 4 ; and
5. Laval University Cancer Research Center, Hôtel-Dies de Québec, Québec QC G1R-2J6, Canada5