Cloning by differential screening of a Xenopus cDNA that encodes a kinesin-related protein.

By differential screening of a Xenopus egg cDNA library, we selected nine clones (Eg1 to Eg9) corresponding to mRNAs which are deadenylated and released from polysomes soon after fertilization. The sequence of one of these clones (Eg5) revealed that the corresponding protein has the characteristic features of a kinesin-related protein. More specifically, Eg5 was found to be nearly 30% identical to a kinesin-related protein encoded by bimc, a gene involved in nuclear division in Aspergillus nidulans.     

EDEN and EDEN-BP, a cis element and an associated factor that mediate sequence-specific mRNA deadenylation in Xenopus embryos.

During Xenopus early development, gene expression is regulated mainly at the translational level by the length of the poly(A) tail of mRNAs. The Eg family and c-mos maternal mRNAs are deadenylated rapidly and translationally repressed after fertilization. Here, we characterize a short sequence element (EDEN) responsible for the rapid deadenylation of Eg5 mRNA. Determining the core EDEN sequence permitted us to localize the c-mos EDEN sequence. The c-mos EDEN confered a rapid deadenylation to a reporter gene. The EDEN-specific RNA-binding protein (EDEN-BP) was purified and a cDNA obtained. EDEN-BP is highly homologous to a human protein possibly involved in myotonic dystrophy. Immunodepleting EDEN-BP from an egg extract totally abolished the EDEN-mediated deadenylation activity, but did not affect the default deadenylation activity. Therefore, EDEN-BP constitutes the first trans-acting factor for which an essential role in the specificity of mRNA deadenylation has been directly demonstrated.