aHoward Hughes Medical Institute, Harvard University Faculty of Arts and Sciences Center for Systems Biology, 52 Oxford Street, Cambridge, MA 02138, USA
bDepartment of Molecular and Cellular Biology, Harvard University Faculty of Arts and Sciences, 52 Oxford Street, Cambridge, MA 02138, USA
cDepartment of Chemistry and Chemical Biology, Harvard University Faculty of Arts and Sciences Center for Systems Biology, 52 Oxford Street, Cambridge, MA 02138, USA