Biochemical identification of Xenopus Pumilio as a sequence-specific cyclin B1 mRNA-binding protein that physically interacts with a Nanos homolog, Xcat-2, and a cytoplasmic polyadenylation element-binding protein.
Translational activation of dormant cyclin B1 mRNA stored in oocytes is a prerequisite for the initiation or promotion of oocyte maturation in many vertebrates. Using a monoclonal antibody against the domain highly homologous to that of Drosophila Pumilio, we have shown for the first time in any vertebrate that a homolog of Pumilio is expressed in Xenopus oocytes. This 137-kDa protein binds to the region including the sequence UGUA at nucleotides 1335-1338 in the 3'-untranslated region of cyclin B1 mRNA, which is close to but does not overlap the cytoplasmic polyadenylation elements (CPEs). Physical in vitro association of Xenopus Pumilio with a Xenopus homolog of Nanos (Xcat-2) was demonstrated by a protein pull-down assay. The results of immunoprecipitation experiments showed in vivo interaction between Xenopus Pumilio and CPE-binding protein (CPEB), a key regulator of translational repression and activation of mRNAs stored in oocytes. This evidence provides a new insight into the mechanism of translational regulation through the 3'-end of mRNA during oocyte maturation. These results also suggest the generality of the function of Pumilio as a translational regulator of dormant mRNAs in both invertebrates and vertebrates.
Nakahata
S
S
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
Katsu
Y
Y
Mita
K
K
Inoue
K
K
Nagahama
Y
Y
Yamashita
M
M
D020413:3' Untranslated Regions / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D019926:Cyclin B / Q000235:genetics*; D056744:Cyclin B1; D003593:Cytoplasm / Q000378:metabolism; D029721:Drosophila Proteins; D005260:Female; D006801:Humans; D019476:Insect Proteins / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology*; D011061:Poly A; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D012097:Repressor Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D029867:Xenopus Proteins; D014982:Xenopus laevis; D016335:Zinc Fingers
D020413:3' Untranslated Regions; C534699:CCNB1 protein, human; C503698:CycB protein, Drosophila; D019926:Cyclin B; D056744:Cyclin B1; D029721:Drosophila Proteins; D019476:Insect Proteins; C430875:PUM1 protein, Xenopus; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D029867:Xenopus Proteins; C558784:nanos1 protein, Xenopus; C074333:pum protein, Drosophila; C070574:nos protein, Drosophila; D011061:Poly A