Masking, unmasking, and regulated polyadenylation cooperate in the translational control of a dormant mRNA in mouse oocytes

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Abstract
The mechanisms responsible for translational silencing of certain mRNAs in growing oocytes, and for their awakening during meiotic maturation, are not completely elucidated. We show that binding of a ∼80-kD protein to a UA-rich element in the 3′ UTR of tissue-type plasminogen activator mRNA, a mouse oocyte mRNA that is translated during meiotic maturation, silences the mRNA in primary oocytes. Translation can be triggered by injecting a competitor transcript that displaces this silencing factor, without elongation of a pre-existing short poly(A) tail, the presence of which is mandatory. During meiotic maturation, cytoplasmic polyadenylation is necessary to maintain a poly(A) tail, but the determining event for translational activation appears to be the modification or displacement of the silencing factor.