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Regulation of Separase in Meiosis: Separase is Activated at the Metaphase I-II Transition in Xenopus Oocytes during Meiosis
Heng-Yu Fan, Qing-Yuan Sun and Hui Zou
volume 5 | issue 2
16 january 2006Pages: 198 - 204
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Separase is a cysteine protease conserved in all eukaryotes and functions to remove the sister chromatid cohesion in anaphase by cleaving the SCC1 subunit of the cohesin complex. The regulation of separase activity as the degradation of its inhibitor, securin, and the downregulation of the inhibitory phosphorylation has never been directly investigated in the meiotic cell cycle of vertebrates. In this study, we cloned the full-length gene encoding Xenopus separase from an oocyte cDNA library. Purified xSeparase can cleave the human ?- kleisin subunit of cohesin in vitro but cannot bind with hSecurin when these two proteins are co-expressed in 293T cells. Similar to its human counterpart, xSeparase cleaves itself upon activation but at a single site. The cleavage site is conserved with one of the three selfcleavage sites in hSeparase. Using self-cleavage as a reporter for its activation, we demonstrated that xSeparase was transiently activated between the two meioses and may be involved in the homologous chromosome separation, as observed in other organisms. Taking the advantage of the inability of xSecurin to interact with hSeparase, we demonstrated that the CSF extract re-inhibit both full-length and auto-cleaved hSeparase, indicating that phosphorylation inhibition of separase does occur under the physiological condition. In addition, we found that the endogenous xSecurin was accumulated in response to progesterone-induced oocyte maturation, and was degraded at both the anaphase I and II in an APC/C-dependent manner.
We now provide open access to journal articles published online for one year or more. This article may be downloaded at the following link:
Download PDF If the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.