/manager/Index ${session.getAttribute("locale")} 5 Repetitive sperm-induced Ca²⁺ transients in mouse oocytes are cell cycle dependent /manager/Repository/uon:6546 Wed 11 Apr 2018 16:15:33 AEST ]]> Spatial regulation of APC<sup>Cdh1</sup>-induced cyclin B1 degradation maintains G2 arrest in mouse oocytes /manager/Repository/uon:11246 Cdh1) activity, which ubiquitylates and so targets cyclin B1 for degradation. Thus, APCCdh1 activity prevents precocious meiotic entry by promoting cyclin B1 degradation. However, it remains unresolved how cyclin B1 levels are suppressed sufficiently to maintain arrest but not so low that they make oocytes hormonally insensitive. Here, we examined spatial control of this process by determining the intracellular location of the proteins involved and using nuclear-targeted cyclin B1. We found that raising nuclear cyclin B1 concentrations, an event normally observed in the minutes before nuclear envelope breakdown, was a very effective method of inducing the G2/M transition. Oocytes expressed only the α-isoform of Cdh1, which was predominantly nuclear, as were Cdc27 and Psmd11, core components of the APC and the 26S proteasome, respectively. Furthermore, APCCdh1 activity appeared higher in the nucleus, as nuclear-targeted cyclin B1 was degraded at twice the rate of wild-type cyclin B1. We propose a simple spatial model of G2 arrest in which nuclear APCCdh1-proteasomal activity guards against any cyclin B1 accumulation mediated by nuclear import.]]> Sat 24 Mar 2018 08:10:55 AEDT ]]>