9630369 Jacobs-Lorena The ultimate goal of this project is to understand the role of mRNA stability in cell differentiation and in the establishment of the embryonic body plan. The focus is on the Drosophila fushi tarazu (ftz) mRNA, whose instability is likely to play a major role in the establishment of the ftz expression pattern in seven stripes that encircle the embryo. Previously, a destabilizing element was mapped to the 3'-untranslated region of the message, close to the polyadenylation site (named FIE3 or ftz instability element in the 3'UTR). At least one more destabilizing element (named FIE5) is located in the 5'-one-third of the mRNA. The research plan has the following aims. 1) To probe into the FIE3 structure-function relationships. The FIE3 will be modified by site- directed mutagenesis and the stability of mRNAs carrying mutant FIE3s will be assessed in embryos by use of the in vivo assay. 2) To map and characterize the 5'-instability element. The location of the other instability element, FIE5, will be determined by deletion-mapping. Its sequence and structure will be compared to that of FlE3 and of other unstable embryonic mRNAs. 3) To determine the importance of ftz mRNA instability for early embryonic development. Genes bearing ftz mRNAs with altered instability elements but encoding the wild type protein will be transformed into the germ line and the phenotypes of the resulting transgenic flies will be analyzed. The functional importance of each FIE will be assessed by measuring ftz expression patterns, and embryonic and adult phenotypes, of flies lacking one or both FIEs. 4) To determine whether the activity that degrades the ftz mRNA is developmentally regulated.. Previous experiments have shown that a mRNA carrying FIE3 is stable in the ovary and unstable in the embryo. Possible developmental regulation of ftz degrading activity will be investigated by measuring the stability of FIE containing mRNAs at different developmental stages and in different cell type s.
