Figure 3.

Developmental regulation of the PNG kinase coupled to cell cycle progression. In mature oocytes arrested at metaphase of meiosis I, cyclinB-CDK1 dependent phospohorylation of GNU exerts an inhibition of PNG complex assembly and activation. The completion of meiosis that follows egg activation results in CDK1 inactivation, prompting the dephosphorylation of GNU. In meiosis II, the accumulation of dephosphorylated GNU proteins leads to the spontaneous assembly of an active PNG kinase complex, consisting of GNU, PNG and PLU. The PNG kinase regulates the translation of hundreds of maternal mRNAs, including cycB and and smg. In addition, GNU protein degradation is promoted by PNG activity, enacting a negative feedback loop that restricts the activity of the complex to the temporal context of early embryonic development.