Control of Meiotic and Mitotic Progression by the F Box Protein β-Trcp1 In Vivo

SCF ubiquitin ligases, composed of three major sub- units, Skp1, Cul1, and one of many F box proteins (Fbps), control the proteolysis of important cellular regulators. We have inactivated the gene encoding the Fbp -Trcp1 in mice. -Trcp1/ males show reduced fer- tility correlating with an accumulation of methaphase I spermatocytes. -Trcp1/ MEFs display a lengthened mitosis, centrosome overduplication, multipolar meta- phase spindles, and misaligned chromosomes. Fur- thermore, cyclin A, cyclin B, and Emi1, an inhibitor of the anaphase promoting complex, are stabilized in mitotic -Trcp1/ MEFs. Indeed, we demonstrate that Emi1 is a bona fide substrate of -Trcp1. In contrast, stabilization of -catenin and IB, two previously re- ported -Trcp1 substrates, does not occur in the ab- sence of -Trcp1 and instead requires the additional silencing of -Trcp2 by siRNA. Thus, -Trcp1 regulates the timely order of meiotic and mitotic events.