EV71-VP1-Flag plasmid was transfected into 293T cells for 36 hours and then treated with MG132 for 12 hours. After drug treatment, cells were collected, cell lysates were incubated with FLAG-Beads overnight and competed with FLAG peptides for 4 hours the next day. Proteins were separated by SDS-PAGE and analyzed by mass spectrometry after Coomassie brilliant blue staining.