During mitosis, ubiquitylation of the anaphase inhibitor securin by the E3 ligase anaphase-promoting complex/cyclosome (APC/C) targets securin for proteolysis, which triggers sister chromatid separation. Securin is also implicated in meiotic progression. Thus, during both mitosis and meiosis, securin expression must be tightly regulated to enable its timely action. On , Risa Kitagawa and co-workers investigate the mechanism underlying this regulation by analysing the subcellular localisation of the securin IFY-1 during C. elegans development. IFY-1 expression is high in the cytoplasm of germ cells, they report, but declines following meiosis I, and remains low during meiosis II and following mitoses. The researchers identify the HECT-E3 ligase ETC-1 as a regulator of the cytoplasmic levels of IFY-1 and CYB-1 (cyclin B1), and show that ETC-1 ubiquitylates IFY-1 and CYB-1 in vitro in the presence of the E2 enzyme UBC-18. These and other data suggest that a novel mechanism, mediated by ETC-1, cooperates with APC/C to regulate the timing of meiosis during germ cell development in C. elegans.
