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Monitoring eIF4F Assembly by Measuring eIF4E-eIF4G Interaction in Live Cells
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Differential phosphorylation controls Maskin association with eukaryotic translation initiation factor 4E and

Daron C Barnard1, Quiping Cao, Joel D Richter

  • 1Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, 01605, USA.

Molecular and Cellular Biology
|August 19, 2005
PubMed

Insights

Maskin phosphorylation by cdk1 during Xenopus oocyte maturation is crucial for releasing translation initiation factor 4E (eIF4E) and activating mRNA translation. This differential phosphorylation also controls Maskin

Area of Science:

  • Molecular Biology
  • Developmental Biology
  • Cell Biology

Background:

  • Cytoplasmic polyadenylation element (CPE)-containing mRNAs are repressed in Xenopus oocytes.
  • Maskin protein binds CPEB and eukaryotic translation initiation factor 4E (eIF4E), inhibiting translation initiation complex formation.
  • Meiotic maturation triggers cytoplasmic polyadenylation and translational activation of these mRNAs.

Purpose of the Study:

  • To investigate the role of Maskin phosphorylation in translational activation during oocyte maturation.
  • To identify specific phosphorylation sites on Maskin and their impact on protein interactions and function.

Main Methods:

  • Site-directed mutagenesis of identified Maskin phosphorylation sites.
  • Analysis of Maskin-eIF4E interaction during oocyte maturation.
  • Assessment of CPE-containing mRNA translational activation.

Main Results:

  • Maskin undergoes phosphorylation at multiple sites (T58, S152, S311, S343, S453, S638) by cdk1 during oocyte maturation.
  • Mutation of these sites prevents Maskin dissociation from eIF4E, inhibiting translational activation.
  • Prior phosphorylation of Maskin at S626 by protein kinase A is essential for its localization in somatic cells but not for oocyte maturation translation.

Conclusions:

  • Differential phosphorylation of Maskin by cdk1 is a key regulatory mechanism for translational activation of CPE-mRNAs during Xenopus oocyte maturation.
  • Phosphorylation controls Maskin's interaction with eIF4E, facilitating the displacement of Maskin and subsequent translation initiation.
  • Maskin phosphorylation also plays a role in its subcellular localization in somatic cells, indicating distinct regulatory roles in different cellular contexts.

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