HOIP truncations proteins GST-PUB, GST-NZF, GST-UBA and GST-RBR-LDD were purified, GST was used as a negative control. The tissue lysates from the C57BL/6 mice were incubated with glutathione-S-transferase (GST) beads which bound to the GST-HOIP truncation proteins beforehand. The pull-down component were separated by SDS-PAGE and stained with Coomassie brilliant blue. The band were cut off and subject to mass spectrometry.