title: XGef is a CPEB-interacting protein involved in Xenopus oocyte maturation.
abstract: XGef was isolated in a screen for proteins interacting with CPEB, a regulator of mRNA translation in early Xenopus development. XGef is a Rho-family guanine nucleotide exchange factor and activates Cdc42 in mammalian cells. Endogenous XGef (58 kDa) interacts with recombinant CPEB, and recombinant XGef interacts with endogenous CPEB in Xenopus oocytes. Injection of XGef antibodies into stage VI Xenopus oocytes blocks progesterone-induced oocyte maturation and prevents the polyadenylation and translation of c-mos mRNA; injection of XGef rescues these events. Overexpression of XGef in oocytes accelerates progesterone-induced oocyte maturation and the polyadenylation and translation of c-mos mRNA. Overexpression of a nucleotide exchange deficient version of XGef, which retains the ability to interact with CPEB, no longer accelerates oocyte maturation or Mos synthesis, suggesting that XGef exchange factor activity is required for the influence of overexpressed XGef on oocyte maturation. XGef overexpression continues to accelerate c-mos polyadenylation in the absence of Mos protein, but does not stimulate MAPK phosphorylation, MPF activation, or oocyte maturation, indicating that XGef may function through the Mos pathway to influence oocyte maturation. These results suggest that XGef may be an early acting component of the progesterone-induced oocyte maturation pathway.
authors.affiliation: Biology Department, Boston College, Chestnut Hill, MA 02467, USA. hakel@bc.edu
authors.forename: Carlos G
authors.initials: CG
authors.lastname: Reverte
authors.forename: Lei
authors.initials: L
authors.lastname: Yuan
authors.forename: Brian T
authors.initials: BT
authors.lastname: Keady
authors.forename: Charlemagne
authors.initials: C
authors.lastname: Lacza
authors.forename: Kathleen R
authors.initials: KR
authors.lastname: Attfield
authors.forename: Gwendolyn M
authors.initials: GM
authors.lastname: Mahon
authors.forename: Benjamin
authors.initials: B
authors.lastname: Freeman
authors.forename: Ian P
authors.initials: IP
authors.lastname: Whitehead
authors.forename: Laura E
authors.initials: LE
authors.lastname: Hake
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005260:Female; D018507:Gene Expression Regulation, Developmental; D016258:Genes, mos; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D009865:Oocytes / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D011374:Progesterone / Q000494:pharmacology; D014176:Protein Biosynthesis; D017231:Proto-Oncogene Proteins c-mos / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014981:Xenopus / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D029867:Xenopus Proteins; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D039221:mRNA Cleavage and Polyadenylation Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C490388:Cpeb1 protein, Xenopus; D020662:Guanine Nucleotide Exchange Factors; D012333:RNA, Messenger; D014157:Transcription Factors; D029867:Xenopus Proteins; D039221:mRNA Cleavage and Polyadenylation Factors; D011374:Progesterone; D017231:Proto-Oncogene Proteins c-mos; D020764:cdc42 GTP-Binding Protein