Asymmetric cell divisions generate cell diversity during development, but what regulates the segregation of cell fate determinants during these divisions? Slack and co-workers have been examining the localization of Miranda (an adaptor for several neural cell fate determinants) to the basal cortex of Drosophila neuroblasts, which divide asymmetrically into an apical neuroblast and a basal ganglion mother cell. On , the researchers report that this localization of Miranda requires the anaphase-promoting complex/cyclosome (APC/C), a new function for this mitotic regulator. They show that when APC/C activity is attenuated, Miranda accumulates near the centrosome instead of at the basal cortex. They also show that the C-terminal domain of Miranda is ubiquitylated, that removal of this domain disrupts Miranda localization similarly to APC/C attenuation, and that addition of ubiquitin to this C-terminal truncated protein restores its localization. As APC/C is an E3 ubiquitin ligase, the researchers speculate that APC/C normally adds a ubiquitin tag to Miranda that regulates its asymmetric localization in neuroblasts.
