title: XGef mediates early CPEB phosphorylation during Xenopus oocyte meiotic maturation.
abstract: Polyadenylation-induced translation is an important regulatory mechanism during metazoan development. During Xenopus oocyte meiotic progression, polyadenylation-induced translation is regulated by CPEB, which is activated by phosphorylation. XGef, a guanine exchange factor, is a CPEB-interacting protein involved in the early steps of progesterone-stimulated oocyte maturation. We find that XGef influences early oocyte maturation by directly influencing CPEB function. XGef and CPEB interact during oogenesis and oocyte maturation and are present in a c-mos messenger ribonucleoprotein (mRNP). Both proteins also interact directly in vitro. XGef overexpression increases the level of CPEB phosphorylated early during oocyte maturation, and this directly correlates with increased Mos protein accumulation and acceleration of meiotic resumption. To exert this effect, XGef must retain guanine exchange activity and the interaction with CPEB. Overexpression of a guanine exchange deficient version of XGef, which interacts with CPEB, does not enhance early CPEB phosphorylation. Overexpression of a version of XGef that has significantly reduced interaction with CPEB, but retains guanine exchange activity, decreases early CPEB phosphorylation and delays oocyte maturation. Injection of XGef antibodies into oocytes blocks progesterone-induced oocyte maturation and early CPEB phosphorylation. These findings indicate that XGef is involved in early CPEB activation and implicate GTPase signaling in this process.
authors.affiliation: Department of Biology, Boston College, Chestnut Hill, MA 02467, USA.
authors.forename: Susana E
authors.initials: SE
authors.lastname: Martínez
authors.forename: Lei
authors.initials: L
authors.lastname: Yuan
authors.forename: Charlemagne
authors.initials: C
authors.lastname: Lacza
authors.forename: Heather
authors.initials: H
authors.lastname: Ransom
authors.forename: Gwendolyn M
authors.initials: GM
authors.lastname: Mahon
authors.forename: Ian P
authors.initials: IP
authors.lastname: Whitehead
authors.forename: Laura E
authors.initials: LE
authors.lastname: Hake
mesh_terms: D000818:Animals; D019556:COS Cells; D002853:Chromatography, Liquid; D020558:GTP Phosphohydrolases / Q000378:metabolism; D017930:Genes, Reporter; D005982:Glutathione Transferase / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D013058:Mass Spectrometry; D008540:Meiosis; D009865:Oocytes / Q000378:metabolism*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011374:Progesterone / Q000378:metabolism; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*; D029867:Xenopus Proteins / Q000235:genetics* / Q000378:metabolism*; D014982:Xenopus laevis; D039221:mRNA Cleavage and Polyadenylation Factors
chemical_list: C502823:ARHGEF39 protein, Xenopus; C490388:Cpeb1 protein, Xenopus; D020662:Guanine Nucleotide Exchange Factors; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; D039221:mRNA Cleavage and Polyadenylation Factors; D011374:Progesterone; D012313:RNA; D005982:Glutathione Transferase; D011494:Protein Kinases; C102333:histone H1 kinase; D020558:GTP Phosphohydrolases