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Translational unmasking of Emi2 directs cytostatic factor arrest in meiosis II

Jeffrey J Tung1, Kiran Padmanabhan, David V Hansen

  • 1Genentech, Inc., South San Francisco, California, USA.

Cell Cycle (Georgetown, Tex.)
|March 16, 2007
PubMed

Insights

Cytostatic factor (CSF) arrests eggs in meiosis II by inhibiting the anaphase-promoting complex/cyclosome (APC/C). Emi2 protein unmasking via translational de-repression drives this specific cell cycle arrest.

Area of Science:

  • Cell Biology
  • Developmental Biology
  • Molecular Biology

Background:

  • Cytostatic factor (CSF) is crucial for arresting vertebrate eggs in meiosis II.
  • The anaphase-promoting complex/cyclosome (APC/C) inhibitor Emi2/XErp1 is a candidate for CSF.
  • The precise mechanism of CSF activation during meiosis II remained unclear.

Purpose of the Study:

  • To elucidate the mechanism of selective CSF activation during meiosis II.
  • To identify how Emi2/XErp1 mediates the meiosis II arrest.

Main Methods:

  • Analysis of Emi2 protein expression timing in Xenopus oocytes.
  • Investigating the role of the 3' untranslated region of Emi2 mRNA.
  • Studying the interaction between Emi2 mRNA and cytoplasmic polyadenylation element-binding protein (CPEB).

Main Results:

  • Emi2 protein is undetectable in immature oocytes and accumulates post-germinal vesicle breakdown.
  • The 3' untranslated region of Emi2 mRNA contains regulatory elements.
  • CPEB binding to Emi2 mRNA regulates its polyadenylation and translation.

Conclusions:

  • CSF arrest in meiosis II is directed by the translational de-repression of Emi2.
  • Cytoplasmic polyadenylation and translational unmasking of Emi2 mRNA control CSF activity.
  • This mechanism ensures accurate progression through meiosis.

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