CPEB is a specificity factor that mediates cytoplasmic polyadenylation during Xenopus oocyte maturation.
The translational activation of several maternal mRNAs during Xenopus oocyte maturation is stimulated by cytoplasmic poly(A) elongation, which requires the uridine-rich cytoplasmic polyadenylation element (CPE) and the hexanucleotide AAUAAA. Here, we have enriched a CPE-binding protein (CPEB) by single-step RNA affinity chromatography, have obtained a CPEB cDNA, and have assessed the role of CPEB in cytoplasmic polyadenylation. The 62 kDa CPEB contains two RNA recognition motifs, and within this region, it is 62% identical to orb, an oocyte-specific RNA-binding protein from Drosophila. CPEB mRNA and protein are abundant in oocytes and are not detected in embryos beyond the gastrula stage. During oocyte maturation, CPEB is phosphorylated at a time that corresponds with the induction of polyadenylation. Immunodepletion of CPEB from polyadenylation-proficient egg extracts renders them incapable of adenylating exogenous RNA. Partial restoration of polyadenylation in depleted extracts is achieved by the addition of CPEB, thus demonstrating that this protein is required for cytoplasmic polyadenylation.
Hake
L E
LE
Worcester Foundation for Experimental Biology Shrewsbury, Massachusetts 01545.
Richter
J D
JD
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002846:Chromatography, Affinity; D003593:Cytoplasm / Q000378:metabolism; D018076:DNA, Complementary / Q000737:chemistry; D004330:Drosophila; D005260:Female; D008969:Molecular Sequence Data; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D011061:Poly A / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D016601:RNA-Binding Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D014981:Xenopus; D029867:Xenopus Proteins; D039221:mRNA Cleavage and Polyadenylation Factors
C490388:Cpeb1 protein, Xenopus; D018076:DNA, Complementary; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; D039221:mRNA Cleavage and Polyadenylation Factors; D011061:Poly A