PARENT SESSION

(T404) DE NOVO SYNTHESIS AND HYPERPHOSPHORYLATION OF pEg3 DURING MEIOTIC MATURATION OF Xenopus laevis OOCYTES.

Xi, Yanwei^{1, 2}, Tassan, Jean-Pierre ³, Liu, Johné ^{1, 2}, ¹ Ottawa Health Research Institute, Ottawa Hospital, Ottawa, ON, Canada² University of Ottawa, Ottawa, ON, Canada³ UMR6061-CNRS, Université de Rennes, Rennes, France

ABSTRACT- RNA transcription is undetectable during the process of oocyte maturation. The oocyte relies solely on proteins already present in cell and on proteins synthesized de novo from the stockpile of maternal mRNAs. pEg3 is a Xenopus protein kinase encoded by a maternal mRNA which is polyadenylated in unfertilized eggs and deadenylated in embryos. During oocyte maturation, pEg3 is synthesized and hyperphosphorylated and then, after fertilization, is rapidly dephosphorylated. In addition, pEg3 is closely related to other KIN1/PAR-1/MARK kinase family members, which have a common conserved primary structure and share a common function in the establishment of cell polarity and asymmetric cell division. The function of pEg3 de novo synthesis or hyperphosphorylation is not known. We employed antisense morpholino oligos to pEg3 to address this question. After being injected pEg3_morph, the de novo synthesis of pEg3 was inhibited during oocyte maturation. But the stability or hyperphosphorylation of the existing pEg3 protein was not affected. Oocytes injected pEg3_morph did not affect the biphasic pattern of MPF (maturation promoting factor) activation. These oocytes, like control oocytes, properly matured and arrested at metaphase II. These data suggest that the accumulation of pEg3 during oocyte meiotic maturation might have no contribution to this process. However, this accumulation may function in the second polar body extrusion or in the mitotic cell cycle after fertilization.

KEY WORDS: pEg3, Xenopus laevis, meiotic