Related Experiment Videos
Dissolution of the maskin-eIF4E complex by cytoplasmic polyadenylation and poly(A)-binding protein controls cyclin B1
1Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA.
Abstract:
Cytoplasmic polyadenylation stimulates the translation of several dormant mRNAs during oocyte maturation in Xenopus. Polyadenylation is regulated by the cytoplasmic polyadenylation element (CPE), a cis-acting element in the 3'-untranslated region of responding mRNAs, and its associated factor CPEB. CPEB also binds maskin, a protein that in turn interacts with eIF4E, the cap-binding factor. Here, we report that based on antibody and mRNA reporter injection assays, maskin prevents oocyte maturation and the translation of the CPE-containing cyclin B1 mRNA by blocking the association of eIF4G with eIF4E. Dissociation of the maskin-eIF4E complex is essential for cyclin B1 mRNA translational activation, and requires not only cytoplasmic polyadenylation, but also the poly(A)-binding protein. These results suggest a molecular mechanism by which CPE- containing mRNA is activated in early development.
Insights
Cytoplasmic polyadenylation activates dormant mRNAs for oocyte maturation in Xenopus. This process requires maskin-eIF4E complex dissociation, enabling cyclin B1 mRNA translation.
Area of Science:
- Molecular Biology
- Developmental Biology
- Xenopus Oocyte Maturation
Background:
- Cytoplasmic polyadenylation is crucial for activating dormant mRNAs during Xenopus oocyte maturation.
- This process is mediated by the cytoplasmic polyadenylation element (CPE) and its binding factor, CPEB.
- CPEB interacts with maskin, which then binds to the cap-binding factor eIF4E.
Purpose of the Study:
- To elucidate the molecular mechanism by which maskin regulates CPE-containing mRNA translation during oocyte maturation.
- To identify the factors involved in the dissociation of the maskin-eIF4E complex and subsequent mRNA activation.
Main Methods:
- Antibody injection assays in Xenopus oocytes.
- mRNA reporter injection assays to study translation.
- Investigating protein-protein interactions between maskin, eIF4E, and eIF4G.
Main Results:
- Maskin inhibits oocyte maturation and cyclin B1 mRNA translation by preventing eIF4G from associating with eIF4E.
- Dissociation of the maskin-eIF4E complex is essential for activating cyclin B1 mRNA translation.
- This dissociation requires both cytoplasmic polyadenylation and the poly(A)-binding protein.
Conclusions:
- A molecular mechanism for CPE-containing mRNA activation in early development is proposed.
- Maskin acts as a translational repressor, and its removal is a key step in oocyte maturation.
- Cytoplasmic polyadenylation and poly(A)-binding protein are critical for relieving maskin-mediated translational repression.