Involvement of Xenopus Pumilio in the translational regulation that is specific to cyclin B1 mRNA during oocyte maturation.
Protein synthesis of cyclin B by translational activation of the dormant mRNA stored in oocytes is required for normal progression of maturation. In this study, we investigated the involvement of Xenopus Pumilio (XPum), a cyclin B1 mRNA-binding protein, in the mRNA-specific translational activation. XPum exhibits high homology to mammalian counterparts, with amino acid identity close to 90%, even if the conserved RNA-binding domain is excluded. XPum is bound to cytoplasmic polyadenylation element (CPE)-binding protein (CPEB) through the RNA-binding domain but not to its phosphorylated form in mature oocytes. In addition to the CPE, the XPum-binding sequence of cyclin B1 mRNA acts as a cis-element for translational repression. Injection of anti-XPum antibody accelerated oocyte maturation and synthesis of cyclin B1, and, conversely, over-expression of XPum retarded oocyte maturation and translation of cyclin B1 mRNA, which was accompanied by inhibition of poly(A) tail elongation. The injection of antibody and the over-expression of XPum, however, had no effect on translation of Mos mRNA, which also contains the CPE. These findings provide the first evidence that XPum is a translational repressor specific to cyclin B1 in vertebrates. We propose that in cooperation with the CPEB-maskin complex, the master regulator common to the CPE-containing mRNAs, XPum acts as a specific regulator that determines the timing of translational activation of cyclin B1 mRNA by its release from phosphorylated CPEB during oocyte maturation.
Nakahata
Shingo
S
Laboratory of Molecular and Cellular Interactions, Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
Kotani
Tomoya
T
Mita
Koichi
K
Kawasaki
Tomoko
T
Katsu
Yoshinao
Y
Nagahama
Yoshitaka
Y
Yamashita
Masakane
M
D020413:3' Untranslated Regions / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019926:Cyclin B / Q000235:genetics*; D056744:Cyclin B1; D018507:Gene Expression Regulation, Developmental; D008845:Microinjections; D008969:Molecular Sequence Data; D009865:Oocytes / Q000254:growth & development / Q000378:metabolism*; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000502:physiology; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000378:metabolism; D014981:Xenopus / Q000235:genetics / Q000378:metabolism*; D029867:Xenopus Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D039221:mRNA Cleavage and Polyadenylation Factors
D020413:3' Untranslated Regions; C490388:Cpeb1 protein, Xenopus; D019926:Cyclin B; D056744:Cyclin B1; C430875:PUM1 protein, Xenopus; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; D039221:mRNA Cleavage and Polyadenylation Factors