Protein ubiquitination is a fundamental post-translational modification event that serves as a signaling function in diversebiological processes,including cell-cycle progression,cell apoptosis,gene transcriptional regulation and expression,etc. In these processesof ubiquitin-proteasome pathway,ubiquitin-conjugating enzyme E2 is of pivotal importance that mediates more than 80 percent of proteindegradation of eukaryotic cells,and it plays a key role on the specific selection of degraded of target protein. In...