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Essential Role of Protein Phosphatase 2A in Metaphase II Arrest and Activation of Mouse Eggs Shown by Okadaic Acid, Dominant Negative Protein Phosphatase 2A, and FTY720

Lookup NU author(s): Dr Hsin Yu Chang


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Vertebrate eggs arrest at second meiotic metaphase. The fertilizing sperm causes meiotic exit through Ca2+-mediated activation of the anaphase-promoting complex/cyclosome (APC/C). Although the loss in activity of the M-phase kinase CDK1 is known to be an essential downstream event of this process, the contribution of phosphatases to arrest and meiotic resumption is less apparent, especially in mammals. Therefore, we explored the role of protein phosphatase 2A (PP2A) in mouse eggs using pharmacological inhibition and activation as well as a functionally dominant-negative catalytic PP2A subunit (dn-PP2Ac-L199P) coupled with live cell imaging. We observed that PP2A inhibition using okadaic acid induced events normally observed at fertilization: degradation of the APC/C substrates cyclin B1 and securin resulting from loss of the APC/C inhibitor Emi2. Although sister chromatids separated, chromatin remained condensed, and polar body extrusion was blocked as a result of a rapid spindle disruption, which could be ameliorated by non-degradable cyclin B1, suggesting that spindle integrity was affected by CDK1 loss. Similar cell cycle effects to okadaic acid were also observed using dominant-negative PP2Ac. Preincubation of eggs with the PP2A activator FTY720 could block many of the actions of okadaic acid, including Emi2, cyclin B1, and securin degradation and sister chromatid separation. Therefore, in conclusion, we used okadaic acid, dn-PP2Ac-L199P, and FTY720 on mouse eggs to demonstrate that PP2A is needed to for both continued metaphase arrest and successful exit from meiosis.

Publication metadata

Author(s): Chang HY, Jennings PC, Stewart J, Verrills NM, Jones KT

Publication type: Article

Publication status: Published

Journal: Journal of Biological Chemistry

Year: 2011

Volume: 286

Issue: 16

Pages: 14705-14712

Print publication date: 07/03/2011

ISSN (print): 0021-9258

ISSN (electronic): 1083-351X

Publisher: American Society for Biochemistry and Molecular Biology, Inc.


DOI: 10.1074/jbc.M110.193227


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Funder referenceFunder name
DP0986217Australian Research Council