Ubiquitin-20S proteasome pathway is a universal pathway for protein degradation in eukaryotes,this pathway is essential for many cellular processes,like cell cycle,the regulation of gene expression and responses to oxidative stress.20S proteasome core particles(20S-CPs)are huge protein complexes assembled by 14 α-subunits and 14 β-subunits,these subunits stacked as four rings to form the highly conserved α7β7β7α7 cylindrical assembly with a central pore,only inner β7β7 rings contain protease active sites and the outer α7 rings serve as a gate,all protein substrates have to be recognized and translocated by regulation particle(RP),then the RP complexes hydrolyze ATP and open-up the gate of 20S–CPs to deliver the substrate for degradation.