1. Department of Biochemistry and Molecular Genetics, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908
2. Department of Cell Cultures, Institute of Cytology RAS, St. Petersburg, Russia
3. Institute of Theoretical and Experimental Biophysics RAS, Puschino, Russia
4. Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037