1. Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
2. Graduate Program in Cell and Molecular Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
3. Graduate Program in Biochemistry and Molecular Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
4. Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
5. Instituto Gulbenkian de Ciência, 2780-156 Oeiras, Portugal.