Cytoplasmic polyadenylation elements mediate masking and unmasking of cyclin B1 mRNA
Department of Molecular Genetics and Microbiology
3' Untranslated Regions; Animals; Base Sequence; Chloramphenicol O-Acetyltransferase; Cyclin B; Cytoplasm; DNA Primers; Oocytes; Poly A; Protein Biosynthesis; RNA, Messenger; Xenopus laevis
Life Sciences | Medicine and Health Sciences
During oocyte maturation, cyclin B1 mRNA is translationally activated by cytoplasmic polyadenylation. This process is dependent on cytoplasmic polyadenylation elements (CPEs) in the 3' untranslated region (UTR) of the mRNA. To determine whether a titratable factor might be involved in the initial translational repression (masking) of this mRNA, high levels of cyclin B1 3' UTR were injected into oocytes. While this treatment had no effect on the poly(A) tail length of endogenous cyclin B1 mRNA, it induced cyclin B1 synthesis. A mutational analysis revealed that the most efficient unmasking element in the cyclin 3' UTR was the CPE. However, other U-rich sequences that resemble the CPE in structure, but which do not bind the CPE-binding polyadenylation factor CPEB, failed to induce unmasking. When fused to the chloramphenical acetyl transferase (CAT) coding region, the cyclin B1 3' UTR inhibited CAT translation in injected oocytes. In addition, a synthetic 3' UTR containing multiple copies of the CPE also inhibited translation, and did so in a dose-dependent manner. Furthermore, efficient CPE-mediated masking required cap-dependent translation. During the normal course of progesterone-induced maturation, cytoplasmic polyadenylation was necessary for mRNA unmasking. A model to explain how cyclin B1 mRNA masking and unmasking could be regulated by the CPE is presented.
DOI of Published Version
EMBO J. 1999 Apr 15;18(8):2294-303. Link to article on publisher's site
The EMBO journal
de Moor, Cornelia H. and Richter, Joel D., "Cytoplasmic polyadenylation elements mediate masking and unmasking of cyclin B1 mRNA" (1999). Open Access Articles. 498.