1. Department of Oncological Sciences, Division of Molecular Biology and Genetics, and Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
2. Department of Chemistry and Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1 Z3, Canada.
3. Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.