[1] Dartmouth Coll Sch Med, Dept Genet, Hanover, NH 03755 USA
[2] Rice Univ, Dept Biochem & Cell Biol, Houston, TX 77005 USA
[3] MIT, Dept Biol, Cambridge, MA 02139 USA
[4] Whitehead Inst Biomed Res, Cambridge, MA 02139 USA
[5] Rutgers State Univ, Waksman Inst, Piscataway, NJ 08854 USA
[6] Univ Penn, Sch Med, Howard Hughes Med Inst, Philadelphia, PA 19104 USA
[7] Univ Penn, Sch Med, Dept Biochem & Biophys, Philadelphia, PA 19104 USA
[8] Washington Univ, Howard Hughes Med Inst, Dept Genet, St Louis, MO 63110 USA
[9] Wellcome Trust Sanger Inst, Cambridge CB10 1SA, England
[10] Austrian Acad Sci, Inst Mol Biol, A-5020 Salzburg, Austria
[11] Harvard Univ, Sch Med, Dept Genet, Boston, MA 02114 USA
[12] Massachusetts Gen Hosp, Dept Mol Biol, Boston, MA 02114 USA
[13] Max Planck Inst Biophys Chem, Dept Cellular Biochem, Gottingen, Germany
[14] MIT, Dept Biol, Cambridge, MA 02142 USA