Localized XId3 mRNA activation in Xenopus embryos by cytoplasmic polyadenylation

In Xenopus development, during meiosis and cleavage, the extent of polyaden ylation plays a central role in regulating the expression of transcripts an d this is mediated by cis regulatory cytoplasmic polyadenylation elements ( CPE) in the 3'-UTRs. We have identified a palindromic CPE in the mRNA of Xe nopus Id3 which is conserved in the Id genes from other vertebrates. It pro motes cytoplasmic polyadenylation and is negatively regulated by sequences further upstream in the 3'-UTR. This palindromic CPE promotes polyadenylati on in both the epithelial and sensorial layers of the dorsal ectoderm in ea rly embryos, but association with the upstream negative element blocks this effect in the epithelial layer. The asymmetric polyadenylation may be impo rtant for establishing a prepattern of transcriptional regulators. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.