Loss of Cdc20 Causes a Securin-Dependent Metaphase Arrest in Two-Cell Mouse Embryos

Abstract

The anaphase-promoting complex/cyclosome (APC/C) is an E3 ubiquitin ligase mediating targeted proteolysis through ubiquitination of protein substrates to control the progression of mitosis. The APC/C recognizes its substrates through two adapter proteins, Cdc20 and Cdh1, which contain similar C-terminal domains composed of seven WD-40 repeats believed to be involved in interacting with their substrates. During the transition from metaphase to anaphase, APC/C-Cdc20 mediates the ubiquitination of securin and cyclin B1, allowing the activation of separase and the onset of anaphase and mitotic exit. APC/C-Cdc20 and APC/C-Cdh1 have overlapping substrates. It is unclear whether they are redundant for mitosis. Using a gene-trapping approach, we have obtained mice which lack Cdc20 function. These mice show failed embryogenesis. The embryos were arrested in metaphase at the two-cell stage with high levels of cyclin B1, indicating an essential role of Cdc20 in mitosis that is not redundant with that of Cdh1. Interestingly, Cdc20 and securin double mutant embryos could not maintain the metaphase arrest, suggesting a role of securin in preventing mitotic exit.

Timing of anaphase-promoting complex activation in mouse oocytes is predicted by microtubule-kinetochore attachment but not by bivalent alignment or tension

“…By comparison, the duration of cyclin B1 degradation in somatic cells is about 20 minutes (Clute and Pines, 1999;Gavet and Pines, 2010). Given that in both oocytes and somatic cells this APC/C substrate loss is Cdc20 dependent (Jin et al, 2010;Li et al, 2007;Reis et al, 2007), the data collectively point towards a period of meiotic APC/C activity that lasts 10 times longer, from APC/C cdc20 activation to cytokinesis, than it does in mitosis of most cultured cell lines.…”

The Ubiquitin Receptors DA1, DAR1, and DAR2 Redundantly Regulate Endoreduplication by Modulating the Stability of TCP14/15 in Arabidopsis

“…For example, the anaphase-promoting complex/cyclosome (APC/C) is a multisubunit E3 ubiquitin ligase complex that has a central role in the degradation of CYC proteins. CELL CYCLE SWITCH52 (CCS52) and CELL CYCLE DIVISION20, which activate APC/C, have conserved functions in plants, yeast, and animals (Li et al, 2007;Kevei et al, 2011;Breuer et al, 2012;Guttery et al, 2012). Arabidopsis CCS52A proteins regulate endocycle onset and progression (Lammens et al, 2008;Larson-Rabin et al, 2009;Breuer et al, 2012).…”

Functional Interaction between BubR1 and Securin in an Anaphase-Promoting Complex/CyclosomeCdc20–Independent Manner

“…However, it is possible that BubR1 may function independently of APC/C Cdc20 to inhibit the onset of anaphase. It has recently been reported that loss of Cdc20 causes a securin-dependent metaphase arrest in mouse embryos, but a Cdc20 and securin double mutant could not maintain the metaphase arrest (34), suggesting that securin has both Cdc20-independent anddependent roles in preventing mitotic exit. In this study, our data provide compelling evidence that the mitotic checkpoint protein BubR1 forms a complex with securin, and that BubR1 contributes to the stability of securin by a Cdc20-independent interaction.…”