Poster abstracts

Poster number 74 submitted by Miriam Ruiz

Distinct effects of exosome subunit depletion on hsp70 and hsp26 mRNA levels upon recovery from heat shock

Daniel L. Kiss (Department of Molecular Biology and Microbiology, School of Medicine, Case Western Reserve University), Miriam I. Ruiz (Department of Molecular Biology and Microbiology, School of Medicine, Case Western Reserve University), Erik D. Andrulis (Department of Molecular Biology and Microbiology, School of Medicine, Case Western Reserve University)

Abstract:
The RNA processing exosome was originally defined as an evolutionarily conserved multi-subunit complex of ribonucleases responsible for the processing and/or turnover of stable RNAs and mRNAs. Results from several in vivo systems challenge the prevailing model of exosome complex function, and we have proposed the exozyme model to address the discrepancies. The exozyme model posits that, in addition to assembling into the core, exosome subunits compose smaller complexes with distinct roles in RNA metabolic events. Here, we test the exozyme model by using RNAi to deplete exosome subunits and an exosome cofactor in Drosophila melanogaster S2 tissue culture cells and assay the effects on hsp70 and hsp26 mRNA levels using S1 nuclease protection assays. As predicted by the exozyme hypothesis, we find different effects on hsp70 and hsp26 mRNA levels when different subunits are depleted. We also observe continued accumulation of heat shock transcripts when we deplete either Rrp4 or Rrp40. This study provides evidence for multiple independent functions for individual exosome subunits and intimates greater complexity of exosome subunit assemblages than heretofore anticipated.

Keywords: exosome, Rrp4, Rrp40