1Department of Biochemistry and Molecular Biophysics, Columbia University, 650 West 168 Street, New York, NY 10032, USA
2Architecture et Réactivité de l'ARN, Institut de Biologie Moléculaire et Cellulaire, CNRS, Université de Strasbourg, 15 Rue René Descartes, 67084 Strasbourg, France
3Department of Biological Sciences, Columbia University, 600 Fairchild Center, New York, NY 10027, USA
4Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University, 650 West 168 Street, New York, NY 10032, USA