Emi2 mediates meiotic MII arrest by competitively inhibiting the binding of Ube2S to the APC/C

In vertebrates, unfertilized eggs arrest at metaphase of meiosis II via Emi2, which inhibits APC/C ubiquitin ligase. Here, Sako et al. show that on fertilization the degradation of Emi2 allows binding between APC/C and the C-terminal tail of the ubiquitin-conjugating enzyme Ube2S, thus releasing the meiotic arrest.