Functional mapping of destabilizing elements in the protein-coding region of the Drosophila fushi tarazu mRNA

The instability of the fushi tarazu (ftz) mRNA is essential for the proper development of the Drosophila embryo. Previously, we identified a 201-nucle otide instability element (FLE3) in the 3 ' untranslated region (UTR) of th e ftz mRNA Here we report on the identification of two additional elements in the protein-coding region of the message: the 83-nucleotide-long FIE5-1 and the 69-nucleotide-long FLE5-2. The function of both elements was positi on dependent; the same elements destabilized RNAs when present within the c oding region but did not when embedded in the 3 ' UTR of the hybrid mRNAs. We conclude that ftz mRNA has three redundant instability elements, two in the protein-coding region and one in the 3 ' UTR. Although each instability element is sufficient to destabilize a heterologous mRNA, the destabilizin g activity of the two 5 ' -elements depended on their position within the m essage.