SKP2 is degraded by the anaphase promoting complex/Cyclosome and its activator FZR1 (Cdh1) [APC/C(Cdh1)] (Bashir et al, 2004; Wei et al, 2004). The tight regulation of APC/C(Cdh1) activity ensures the timely elimination SKP2 and, thus, plays a critical role in controlling the M/G1 transition (mitotic exit). APC/C:Cdh1-mediated degradation of SKP2 depends on RB1, as RB1 recruits SKP2 to the APC/C:Cdh1 complex, by simultaneously interacting with SKP2 and FZR1. RB1 does not undergo APC/C:Cdh1-mediated ubiquitination (Binne et al. 2007).