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Translational Unmasking of Emi2 Directs Cytostatic Factor Arrest in Meiosis II

Jeffrey J. Tung, Kiran Padmanabhan, David V. Hansen, Joel D. Richter and Peter K. Jackson

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Cytostatic factor (CSF) arrests unfertilized vertebrate eggs in metaphase of meiosis II by inhibiting the anaphase-promoting complex/cyclosome (APC/C) from mediating cyclin destruction. The APC/C inhibitor Emi2/XErp1 satisfies a number of historical criteria for the molecular identification of CSF, but the mechanism by which CSF is activated selectively in meiosis II is the remaining unexplained criterion. Here we provide an explanation by showing that Emi2 is expressed specifically in meiosis II through translational de-repression or “unmasking” of its mRNA. We find that Emi2 protein is undetectable in immature, G2/prophase-arrested Xenopus oocytes and accumulates ~90 minutes after germinal vesicle breakdown. The 3’ untranslated region of Emi2 mRNA contains cytoplasmic polyadenylation elements that directly bind the CPEB protein and confer temporal regulation of Emi2 polyadenylation and translation. Our results demonstrate that cytoplasmic polyadenylation and translational unmasking of Emi2 directs meiosis II-specific CSF arrest.

Authors

Jeffrey J. Tung

Genentech, Inc., San Francisco, California

Kiran Padmanabhan

University of Massachusetts Medical School, Worcester, Massachusetts

David V. Hansen

Genentech, Inc., San Francisco, California

Joel D. Richter

University of Massachusetts Medical School, Worcester, Massachusetts

Peter K. Jackson

Genentech, Inc., San Francisco, California

This is an open-access article

 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.