Inhibition of Xenopus oocyte meiotic maturation by catalytically inactive protein kinase A.

Progesterone induces G2-arrested Xenopus oocytes to develop into fertilizable eggs in a process called meiotic maturation. Protein kinase A the cAMP-dependent protein kinase, has long been known to be a potent inhibitor of meiotic maturation, but little information is available on how functions. We have cloned two Xenopus duanyu1529 catalytic subunit isoforms, and These proteins are 89% identical and both inhibit progesterone-induced meiotic maturation when overexpressed at low levels, suggesting that duanyu1529 activity is tightly regulated in the oocyte. Unexpectedly, catalytically inactive mutants are able to block progesterone-induced maturation as efficiently as the wild-type active These mutants also block meiotic maturation induced by Mos, but are less efficient at inhibiting Cdc25C-induced maturation. Our results indicate that duanyu1529 can inhibit meiotic maturation by a novel mechanism, which does not require its kinase activity and is also independent of binding to the duanyu1529 regulatory subunits.

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