Title

RNA editing of para sodium channel transcripts in Drosophila

Date of Completion

January 2001

Keywords

Biology, Genetics

Degree

Ph.D.

Abstract

RNA editing has been previously described for glutamate receptor (GluR) subunit genes in the mammalian brain. Modification of a mRNA primary transcript by a double-stranded (ds) RNA adenosine deaminase, which converts select adenosines to inosine, can alter primary amino acid sequence by changing the codon for select amino acid residues. These non-templated amino-acid substitutions to (GluR) subunits have profound functional consequences. ^ RNA editing sites were found in cDNAs derived from the para locus of Drosophila, which encodes a major sodium channel of the CNS. These three sites all involve single nucleotide changes in cDNAs, differing from the corresponding genomic sequence and resulting in single amino acid changes. Based upon the proposed editing mechanism for GluR subunits, we hypothesized that, in each case, a dsRNA secondary structure would form near the editing site providing a substrate for the editase. We describe putative RNA secondary structures for these editing sites found in Drosophila melanogaster. Evolutionary conservation of editing at two sites was observed by sequence comparison with the para locus of Drosophila virilis, while another site was abolished through evolution. In D. melanogaster, editing sites appear to be differentially developmentally regulated. Two sites are edited at low frequencies in embryo and all larval stages (∼2%), increasing during pupal development to adult levels (25–45%). However, the third site is edited at a relatively high frequency in embryo (∼12%) and increases rapidly to adult levels (∼70%) during the third instar larval stage. ^ Subsequently, constructs of two of the sites and sequence required for their proposed dsRNA secondary structures were used to produce transgenic flies. Editing of these constructs is demonstrated in transgenic flies. The implications of these results for Drosophila biology and the RNA editing field are discussed. ^