title: Translational regulation of cyclin B mRNA by 17alpha,20beta-dihydroxy-4-pregnen-3-one (maturation-inducing hormone) during oocyte maturation in a teleost fish, the goldfish (Carassius auratus).
abstract: 17Alpha,20beta-dihydroxy-4-pregnen-3-one (17alpha,20beta-DP) was identified as maturation-inducing hormone (MIH) in several teleost fishes. In goldfish (Carassius auratus), 17alpha,20beta-DP induces oocyte maturation by stimulating the de novo synthesis of cyclin B, a regulatory subunit of maturation-promoting factor (MPF). In this study, we examined the control mechanisms of 17alpha,20beta-DP-induced de novo synthesis of cyclin B protein in oocytes, which is a prerequisite step for MPF activation during oocyte maturation in goldfish. Cycloheximide-treated oocytes failed to undergo meiotic maturation in response to 17alpha,20beta-DP; in this group neither cyclin B nor 34-kDa active cdc2 was detectable in oocytes. In contrast, oocytes exposed to actinomycin D plus 17alpha,20beta-DP or 17alpha,20beta-DP underwent maturation; in these groups both cyclin B and 34-kDa cdc2 were present. Northern blotting showed that cyclin B mRNA is present in both immature and mature oocytes. Sequence analysis revealed that goldfish cyclin B mRNA contains four copies of cytoplasmic polyadenylation element (CPE)-like motifs in the 3' noncoding region, suggesting that the initiation of cyclin B synthesis during oocyte maturation may be controlled by the elongation of poly (A) tail. We then examined the polyadenylation state of cyclin B mRNA during 17alpha,20beta-DP-induced oocyte maturation by means of a PCR poly (A) test, and found that cyclin B mRNA is polyadenylated during oocyte maturation. Polyadenylation of cyclin B mRNA occurred at the same time of germinal vesicle breakdown. Furthermore, cordycepin, an inhibitor of poly (A) addition of mRNA, prevented 17alpha,20beta-DP-induced oocyte maturation. These findings suggest that in goldfish oocytes, the synthesis of cyclin B protein is under translational control and that cytoplasmic 3' poly(A) elongation is involved in 17alpha,20beta-DP-induced translation of cyclin B mRNA.
authors.affiliation: Laboratory of Reproductive Biology, National Institute for Basic Biology, Okazaki, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Katsu
authors.forename: M
authors.initials: M
authors.lastname: Yamashita
authors.forename: Y
authors.initials: Y
authors.lastname: Nagahama
mesh_terms: D020413:3' Untranslated Regions / Q000032:analysis; D000818:Animals; D001483:Base Sequence; D019926:Cyclin B / Q000096:biosynthesis / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D003839:Deoxyadenosines / Q000494:pharmacology; D005786:Gene Expression Regulation; D006054:Goldfish / Q000378:metabolism*; D006908:Hydroxyprogesterones / Q000494:pharmacology*; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D009865:Oocytes / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D009866:Oogenesis / Q000187:drug effects; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000378:metabolism*
chemical_list: D020413:3' Untranslated Regions; D019926:Cyclin B; D003839:Deoxyadenosines; D006908:Hydroxyprogesterones; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; C007433:17,20-dihydroxy-4-pregnen-3-one; D003609:Dactinomycin; D003513:Cycloheximide; C058120:cordycepin