1. Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
2. Laboratory of Virology and Infectious Disease, Center for the Study of Hepatitis C, The Rockefeller University, New York, NY 10065, USA.
3. Automatic Control Laboratory, ETH Zurich, 8092 Zurich, Switzerland.
4. Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA.