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XB-ART-1488
Mol Cell Biol September 1, 2005; 25 (17): 7605-15.

Differential phosphorylation controls Maskin association with eukaryotic translation initiation factor 4E and localization on the mitotic apparatus.

Barnard DC , Cao Q , Richter JD .


Abstract
Several cytoplasmic polyadenylation element (CPE)-containing mRNAs that are repressed in Xenopus oocytes become active during meiotic maturation. A group of factors that are anchored to the CPE are responsible for this repression and activation. Two of the most important are CPEB, which binds directly to the CPE, and Maskin, which associates with CPEB. In oocytes, Maskin also binds eukaryotic translation initiation factor 4E (eIF4E), an interaction that excludes eIF4G and prevents formation of the eIF4F initiation complex. When the oocytes are stimulated to reenter the meiotic divisions (maturation), CPEB promotes cytoplasmic polyadenylation. The newly elongated poly(A) tail becomes bound by poly(A) binding protein (PABP), which in turn binds eIF4G and helps it displace Maskin from eIF4E, thereby inducing translation. Here we show that Maskin undergoes several phosphorylation events during oocyte maturation, some of which are important for its dissociation from eIF4E and translational activation of CPE-containing mRNA. These sites are T58, S152, S311, S343, S453, and S638 and are phosphorylated by cdk1. Mutation of these sites to alanine alleviates the cdk1-induced dissociation of Maskin from eIF4E. Prior to maturation, Maskin is phosphorylated on S626 by protein kinase A. While this modification has no detectable effect on translation during oocyte maturation, it is critical for this protein to localize on the mitotic apparatus in somatic cells. These results show that Maskin activity and localization is controlled by differential phosphorylation.

PubMed ID: 16107707
PMC ID: PMC1190291
Article link: Mol Cell Biol
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: cdk1 cpeb1 eif4a2 eif4e eif4g1 mos pabpc4 prss1 ptpa tacc3
Morpholinos: mos MO3


Article Images: [+] show captions
References [+] :
Barnard, Symplekin and xGLD-2 are required for CPEB-mediated cytoplasmic polyadenylation. 2004, Pubmed, Xenbase