Molecular cloning of cyclin B transcript with an unusually long 3' untranslation region and its expression analysis during oogenesis in the Chinese mitten crab, Eriocheir sinensis.

The meiotic maturation of oocyte in animals is regulated by maturation promotion factor (MPF), a complex of Cdc2 and cyclin B. Although the role of MPF during oocyte maturation has been well studied in a wide variety of eukaryotic organisms, little is known for crustacean species. In this study, a full-length cDNA of cyclin B was cloned from the Chinese mitten crab using degenerate RT-PCR and RACE methods. The crab cyclin B cDNA was 3,794 bp containing an unusually long 3' untranslation region (UTR) of 2,403 bp and an open-reading frame encoding for a protein of 410 amino acids, with a calculated molecular mass of 45 kDa. The long 3'UTR harbors many cytoplasmic polyadenylation elements (CPE), and the GY-box, Brd-box, K-box that are perfectly complementary to the 5'-ends of various Drosophila microRNAs. The crab cyclin B transcript was predominantly expressed in ovary and testis. Semi-quantitative RT-PCR analysis revealed that the amount of cyclin B mRNA was high at previtellogenesis and late vitellogenesis stages, while low at early and middle vitellogenesis, suggesting that differential expression of cyclin B is closely related to oogonial proliferation (mitosis) and oocyte meiotic maturation.