Oocyte meiosis-coupled poly(A) polymerase α phosphorylation and activation trigger maternal mRNA translation in mice

Area of Science:

• Cell Biology
• Molecular Biology
• Reproductive Biology

Background:

• Mammalian oocyte maturation relies on regulated mRNA polyadenylation and translation.
• The specific poly(A) polymerase (PAP) responsible for cytoplasmic polyadenylation in oocytes remained unidentified.

Purpose of the Study:

• To identify the PAP enzyme catalyzing cytoplasmic mRNA polyadenylation during mouse oocyte maturation.
• To elucidate the regulatory mechanisms controlling PAP activity and its role in meiotic progression.

Main Methods:

• Identification and localization studies of PAPα in oocytes.
• Functional assays involving PAPα inhibition.
• Analysis of PAPα phosphorylation by cell cycle kinases (CDK1, ERK1/2).
• Investigation of PAPα's role in maternal transcript polyadenylation and translation.

Main Results:

• PAPα was identified as the key enzyme for cytoplasmic mRNA polyadenylation in mouse oocytes.
• PAPα localization shifts from the germinal vesicle to the ooplasm upon maturation.
• Inhibition of PAPα blocked polyadenylation, translation, and meiotic progression.
• CDK1 and ERK1/2 phosphorylate PAPα, enhancing its activity and promoting translation of specific transcripts.
• PAPα activates its own mRNA translation via a positive feedback loop, amplifying its levels and activity.

Conclusions:

• PAPα is essential for mammalian oocyte maturation, mediating cytoplasmic polyadenylation and translational control.
• Phosphorylation by CDK1 and ERK1/2 is a critical regulatory mechanism for PAPα activity during meiosis.
• PAPα amplification through positive feedback ensures sufficient polyadenylation and translation for successful meiotic progression.