• Register
Forgot Password

If you have forgotten your password you can enter your email here and get a temporary password sent to your email.


Leaving Community

Are you sure you want to leave this community? Leaving the community will revoke any permissions you have been granted in this community.


CaMKII and polo-like kinase 1 sequentially phosphorylate the cytostatic factor Emi2/XErp1 to trigger its destruction and meiotic exit.

In vertebrate meiosis, unfertilized eggs are arrested in metaphase II by cytostatic factor (CSF), which is required to maintain mitotic cyclin-dependent kinase activity. Fertilization triggers a transient increase in cytosolic free Ca(2+), which leads to CSF inactivation and ubiquitin-dependent cyclin destruction through the anaphase promoting complex or cyclosome (APC/C). The Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and the Polo-like kinase Plx1 are essential factors for Ca(2+)-induced meiotic exit, but the critical targets of these kinases were unknown. The APC/C inhibitor Emi2 or XErp1 has recently been characterized as a pivotal CSF component, required to maintain metaphase II arrest and rapidly destroyed in response to Ca(2+) signaling through phosphorylation by Plx1 and ubiquitination by the SCF(betaTrCP) complex. An important question is how the increase in free Ca(2+) targets Plx1 activity toward Emi2. Here, we demonstrate that CaMKII is required for Ca(2+)-induced Emi2 destruction, and that CaMKII functions as a "priming kinase," directly phosphorylating Emi2 at a specific motif to induce a strong interaction with the Polo Box domain of Plx1. We show that the strict requirement for CaMKII to phosphorylate Emi2 is a specific feature of CSF arrest, and we also use phosphatase inhibitors to demonstrate an additional mode of Emi2 inactivation independent of its destruction. We firmly establish the CSF component Emi2 as the first-known critical and direct target of CaMKII in CSF release, providing a detailed molecular mechanism explaining how CaMKII and Plx1 coordinately direct APC/C activation and meiotic exit upon fertilization.

Pubmed ID: 16407128


  • Hansen DV
  • Tung JJ
  • Jackson PK


Proceedings of the National Academy of Sciences of the United States of America

Publication Data

January 17, 2006

Associated Grants

  • Agency: NCI NIH HHS, Id: 5T32 CA09302-27
  • Agency: NIGMS NIH HHS, Id: GM54811
  • Agency: NIGMS NIH HHS, Id: R01 GM60439

Mesh Terms

  • Animals
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Cell Cycle Proteins
  • Cyclin B
  • F-Box Proteins
  • Fertilization
  • Meiosis
  • Oocytes
  • Phosphoric Monoester Hydrolases
  • Phosphorylation
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-mos
  • Xenopus
  • Xenopus Proteins