Anaphase promoting complex/cyclosome Cdc20 (APC/CCdc20) is thought to be assembled in prophase (P) and initiates the degradation of cyclin A (CycA) already in prometaphase (PM). Proteolysis of cyclin B (CycB) and the separase inhibitor securin (Sec) also depends on APC/CCdc20 but is delayed until metaphase (M) by the spindle-assembly checkpoint (SAC). During anaphase (A) and telophase (T), APCCdh1 is activated, contributes to the degradation of securin and cyclin B, and mediates the destruction of additional substrates such as Polo-like kinase-1 (Plk1) and Cdc20, which leads to the inactivation of APC/CCdc20. In G1 phase, APC/CCdh1 mediates the destruction of the ubiquitin-conjugating (E2) enzyme UBCH10, and thereby allows for the accumulation of cyclin A, which contributes to the inactivation of APC/CCdh1 at the transition from G1 to S phase.