RNA editing via the ADAR enzymes (adenosine deaminases that act on RNA) has emerged as a novel and significant post- transcriptional mechanism for altering protein products encoded by a single genetic locus. ADAR activity has been detected across phyletically distant organisms and within a variety of tissues within an organism. Paradoxically, the number of mRNA targets of ADARs remains small and limited primarily to ligand- gated ion channels of the mammalian nervous system. A limited number of well characterized mRNA substrates for ADARs have been characterized and a general requirement for a dsRNA intermediate in pre-mRNA has been proven. Still, central questions with no consistent answers remain such as; What determines ADAR specificity? What comprises an RNA editing site and can we predict their existence rather than relying on serendipity? What are the phenotypic consequences for the organism of editing of a particular RNA editing site? What is the global role of RNA editing in gene regulation? In this proposal, these major areas are addressed using Drosophila as a model genetic system. First, known RNA editing sites in several Drosophila voltage- and ligand-gated ion channels as well as one in an enzyme will be utilized to elucidate the cis-determinants of pre-mRNA editing sites via in vivo transgenic and in vitro methods. Second, a genetic and molecular approach will determine the effects of knocking out or reducing RNA editing of a specific RNA editing site in a ion-channel gene known to have effects on nervous system function and behavior. Lastly, a recently isolated knock- out mutation of the Drosophila ADAR, dADAR, will be characterized at the molecular, genetic and behavioral level to assess the global significance of specific RNA editing.
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