1. Department of Genetics, Yale School of Medicine, New Haven, CT 06520, USA.
2. Howard Hughes Medical Institute, Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA.
3. Department of Biochemistry and Molecular Genetics, University of Colorado Denver, Aurora, CO 80045, USA.
4. Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02155, USA.
5. Department of Chemistry, Appalachian State University, Boone, NC 28608, USA.
6. Salk Institute for Biological Studies, La Jolla, CA 92037, USA.