1. Key Laboratory of Gene Engineering of the Ministry of Education, State Key Laboratory for Biocontrol, Sun Yat-sen University, Guangzhou 510275, P. R. China
2. Department of Systems Biology, Beckman Research Institute of City of Hope, Monrovia, California 91016, USA
3. Department of Chemistry and Institute for Biophysical Dynamics, the University of Chicago, Chicago, IL 60637, USA