Characterization of Dis3 in Drosophila melanogaster. Amanda Raimer¹, Mark Snee², Hemlata Mistry¹, James Skeath². 1) Department of Biochemistry, Widener University, Chester, PA; 2) Department of Genetics, Washington University School of Medicine, St. Louis, MO.

   The exosome is the complex responsible for RNA degradation in the cell; Dis3 is a 3 to 5 exoribonuclease subunit of the exosome. Dis3 functions in both the nucleus and the cytoplasm, while its homolog Dis3-like is apparently restricted to the cytoplasm. Dis3 function has been implicated in accurate RNA degradation. However the mechanism that determines the cellular and temporal specificity of RNA degradation is unclear. Furthermore, it is uncertain how particular RNAs are targeted for destruction. To better understand the importance of Dis3 function in vivo, sixteen homozygous lethal Dis3 alleles have been generated. Each allele will be molecularly characterized through sequencing the coding region and intron-exon junctions to specifically identify missense mutations. The stage of arrest in development will also be determined by comparing embryonic and larval development of the mutant lines to that of a Dis3 RNAi line. The mRNA and protein expression patterns of Dis3 in both embryos and larval imaginal discs will be compared using in situ hybridization and immunostaining, respectively. Finally, GST-tagged wild-type and exoribonuclease-defective Dis3 proteins will be used to identify potential Dis3 targets and the mechanism by which RNA degradation is modulated. This research will lead to a better understanding of Dis3 function in Drosophila, and begin to uncover its importance in many developmental processes.