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Meiotic maturation in Xenopus requires polyadenylation of multiple mRNAs
A Barkoff1, S Ballantyne, M Wickens
1Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA.
Abstract:
Cytoplasmic polyadenylation of specific mRNAs commonly is correlated with their translational activation during development. Here, we focus on links between cytoplasmic polyadenylation, translational activation and the control of meiotic maturation in Xenopus oocytes. We manipulate endogenous c-mos mRNA, which encodes a protein kinase that regulates meiotic maturation. We determined that translational activation of endogenous c-mos mRNA requires a long poly(A) tail per se, rather than the process of polyadenylation. For this, we injected 'prosthetic' poly(A)_synthetic poly(A) tails designed to attach by base pairing to endogenous c-mos mRNA that has had its own polyadenylation signals removed. This prosthetic poly(A) tail activates c-mos translation and restores meiotic maturation in response to progesterone. Thus the role of polyadenylation in activating c-mos mRNA differs from its role in activating certain other mRNAs, for which the act of polyadenylation is required. In the absence of progesterone, prosthetic poly(A) does not stimulate c-mos expression, implying that progesterone acts at additional steps to elevate c-Mos protein. By using a general inhibitor of polyadenylation together with prosthetic poly(A), we demonstrate that these additional steps include polyadenylation of at least one other mRNA, in addition to that of c-mos mRNA. These other mRNAs, encoding regulators of meiotic maturation, act upstream of c-Mos in the meiotic maturation pathway.
Insights
The presence of a long poly(A) tail, not the process of polyadenylation, activates c-mos mRNA translation for meiotic maturation in Xenopus oocytes. Progesterone triggers additional steps, including other mRNA polyadenylation, upstream of c-Mos.
Area of Science:
- Molecular Biology
- Developmental Biology
- Cell Biology
Background:
- Cytoplasmic polyadenylation is linked to mRNA translational activation during development.
- Meiotic maturation in Xenopus oocytes is a key developmental process regulated by specific mRNAs.
- The c-mos mRNA encodes a protein kinase crucial for regulating meiotic maturation.
Purpose of the Study:
- To investigate the role of cytoplasmic polyadenylation in translational activation of c-mos mRNA.
- To determine the specific requirements for activating c-mos translation and meiotic maturation.
- To elucidate the mechanism by which progesterone controls meiotic maturation via c-mos mRNA.
Main Methods:
- Injection of 'prosthetic' poly(A) tails into Xenopus oocytes with modified c-mos mRNA.
- Manipulation of endogenous c-mos mRNA polyadenylation status.
- Use of a general polyadenylation inhibitor in conjunction with prosthetic poly(A) tails.
Main Results:
- A long poly(A) tail, rather than the act of polyadenylation, is sufficient for c-mos mRNA translational activation.
- Prosthetic poly(A) tails restore progesterone-induced meiotic maturation.
- Progesterone acts at additional steps, including polyadenylation of other mRNAs, to elevate c-Mos protein levels.
Conclusions:
- The mechanism of c-mos mRNA activation by polyadenylation differs from other mRNAs.
- Progesterone signaling involves multiple regulatory steps, including polyadenylation of upstream regulatory mRNAs.
- These findings provide insights into the intricate control of meiotic maturation in Xenopus oocytes.