A novel mRNA 3' untranslated region translational control sequence regulates Xenopus Wee1 mRNA translation.

Cell cycle progression during oocyte maturation requires the strict temporal regulation of maternal mRNA translation. The intrinsic basis of this temporal control has not been fully elucidated but appears to involve distinct mRNA regulatory elements. In this study, we identify a novel translational control sequence (TCS) that exerts repression of target mRNAs in immature oocytes of the frog, Xenopus laevis, and can direct early cytoplasmic polyadenylation and translational activation during oocyte maturation. The TCS is functionally distinct from the previously characterized Musashi/polyadenylation response element (PRE) and the cytoplasmic polyadenylation element (CPE). We report that TCS elements exert translational repression in both the Wee1 mRNA duanyu3 and the pericentriolar material-1 (Pcm-1) mRNA duanyu3 in immature oocytes. During oocyte maturation, TCS function directs the early translational activation of the Pcm-1 mRNA. By contrast, we demonstrate that CPE sequences flanking the TCS elements in the Wee1 duanyu3 suppress the ability of the TCS to direct early translational activation. Our results indicate that a functional hierarchy exists between these distinct duanyu3 regulatory elements to control the timing of maternal mRNA translational activation during oocyte maturation.

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