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Substrate-specific regulation of RNA deadenylation in Xenopus embryo and activated egg extracts
V Legagneux1, F Omilli, H B Osborne
1Departement de Biologie et Génétique du Développement, CNRS URA 256, Université de Rennes I, France. vincent.legagneux@univ-rennes1.fr
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.
Insights
Two distinct deadenylation activities were identified in Xenopus egg extracts, controlling the poly(A) tail length of maternal mRNAs during early development. This research clarifies mRNA deadenylation mechanisms in embryos.
Area of Science:
- Molecular Biology
- Developmental Biology
- Xenopus laevis research
Background:
- The poly(A) tail of messenger RNAs (mRNAs) is crucial for translational control.
- In Xenopus laevis oocytes, maternal mRNAs with a cytoplasmic polyadenylation element (CPE) are polyadenylated, while those lacking a CPE undergo default deadenylation.
- Eg mRNAs are polyadenylated in oocytes but rapidly deadenylated post-fertilization, requiring specific sequence elements.
Purpose of the Study:
- To investigate the deadenylation mechanisms of Eg mRNAs after fertilization in Xenopus.
- To characterize the distinct deadenylation activities present in cell-free extracts from Xenopus embryos and eggs.
- To identify factors controlling Eg mRNA deadenylation in developing embryos.
Main Methods:
- Utilized cell-free extracts from Xenopus embryos and activated eggs.
- Assayed for deadenylation activities using RNA substrates with and without functional CPEs.
- Compared kinetic properties and substrate specificities of different deadenylation activities.
Main Results:
- Identified two kinetically distinct deadenylation activities in Xenopus egg/embryo extracts.
- One activity corresponds to default Poly(A) Nuclease (PAN) activity, responsible for slow deadenylation of CPE-deficient RNAs.
- A second, distinct activity mediates rapid deadenylation of RNAs containing a specific deadenylation element.
Conclusions:
- Xenopus egg and embryo extracts possess separable deadenylation activities with differing substrate preferences.
- These activities differentially regulate maternal mRNA poly(A) tail length post-fertilization.
- The described in vitro system facilitates the study of factors governing Eg mRNA deadenylation in early development.