Fig. 3. Fertilization-mediated Emi2 degradation and CSF release. CSF arrest is controlled by Emi2-mediated APC/C inhibition. Upon fertilization, CaMKII kinase activity increases, leading to Emi2 phosphorylation, which creates a Plx1-binding motif on Emi2. Emi2-bound Plx1 then phosphorylates Emi2, allowing Emi2 to be recognized by the β-TrCP E3 ubiquitin ligase. Emi2 ubiquitylation primes Emi2 for degradation, leading to APC/C activation and, eventually, exit from CSF arrest.