Abstract
The poly(A) tail of mRNAs plays an important role in translational control. In Xenopus laevis matured oocytes, maternal mRNAs that contain a cytoplasmic polyadenylation element (CPE) are polyadenylated, whereas CPE deficient mRNAs are deadenylated by a default process. Eg mRNAs are maternal transcripts that are poly(A)+ in matured oocytes and rapidly deadenylated after fertilization. This post-fertilization deadenylation of Eg mRNAs requires specific sequence information. Such a deadenylation element has been identified previously in the 3'UTR of Eg2 mRNA. In this study, we show that cell-free extracts made from embryos or activated eggs contain two kinetically distinct deadenylation activities, with different substrate specificities. One, responsible for the slow deadenylation of RNAs that are devoid of a functional CPE, has the characteristics of a default PAN activity. The other effectuates the rapid deadenylation of RNAs containing a deadenylation element. The in vitro system described here will allow the characterization of factors controlling the deadenylation of Eg mRNAs in embryos.
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