Anaphase-Promoting Complex (APC) which is also called cyclosome, a highly conserved protein, plays a key role in both cell cycle and Ubq degradation pathway. The APC can results in degradation of specific proteins which are involved in cell cycle by tagging those proteins during the transition from metaphase to anaphase. When spindle checkpoint is silenced, APC can easily bind to Cdc20 after phosphorylated by M-Cdks. Then APC targets cyclin A and cyclin B for degradation.