1. Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305-5307, USA.
2. Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305-5307, USA.
3. Department of Internal Medicine, Division of Pulmonary and Critical Care, and Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305-5307, USA.