Date of Award
Doctor of Philosophy (PhD)
Lipid overload contributes to the pathogenesis of diabetic complications, causing tissue damage and cell death in a number of organ systems. This process is termed lipotoxicity. Animal and cell culture studies have demonstrated that oxidative stress and endoplasmic reticulum stress are major pathways engaged in the lipotoxic response. However, the molecular mechanisms of lipotoxicity are not well understood. A genetic screen revealed that small nucleolar RNAs (snoRNAs) encoded in the introns of the Rpl13a locus are critical for cell death in response to lipotoxicity. Initial studies have suggested that the Rpl13a snoRNAs function in this pathway through non-canonical modes of action, involving trafficking to the cytoplasm.To gain insight into the mechanism of action of Rpl13a snoRNA U33, snoRNPs were isolated from cells. We observed many previously undescribed snoRNA-interacting proteins in whole cell lysates. Identification of proteins that co-precipitate from cytosolic and post-cytosolic lysates, under lipotoxic stress and basal conditions, demonstrated that U33-containing complexes are dynamic, and the composition of these complexes depends on both subcellular localization and the presence or absence of stress. We hypothesized that Rpl13a snoRNAs may direct modification of cytosolic mRNAs to affect their abundance or translation efficiency. Consistent with this model, RNA-seq analysis identified over 200 transcripts with significant changes in abundance under lipotoxic conditions. Metabolic labeling revealed that many of these changes are due, at least in part, to changes in transcript stability. Furthermore, ribosome footprinting indicated that a number of transcripts are differentially translated during lipotoxicity. Together, these studies add to a growing body of evidence that snoRNAs function in roles beyond the processing and modification of ribosomal RNAs.
Chair and Committee
Jean E. Schaffer
John Edwards, Kathleen Hall, Jason Held, Jason Weber,
Henderson, Miquia Sherree, "The RpL13a snoRNA U33 Forms Novel snoRNPs During Lipotoxicity" (2017). Arts & Sciences Electronic Theses and Dissertations. 1111.