Program in Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA. zsh@amss.ac.cn|Program in Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA. zsh@amss.ac.cn|Program in Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA. zsh@amss.ac.cn|Program in Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA. zsh@amss.ac.cn