Poster abstracts

Poster number 72 submitted by Mridusmita Saikia

Exploring tRNA cleavage as the mechanism of translational repression in response to osmotic stress

Mridusmita Saikia (Department of Nutrition, Case Western Reserve University), Dawid Krokowski (Department of Nutrition, Case Western Reserve University), Maria Hatzoglou (Department of Nutrition, Case Western Reserve University)

Abstract:
Regulation of cell volume is a fundamental process in living cells. Cells have developed adaptive mechanisms to respond to physiological changes in extracellular osmolarity (as known for kidney medulla cells) and restore cell volume. However, pathological exposure of cells to increased osmolarity (inflammation, diabetes, hypernatremia) induces a competing to adaptation apoptotic program. Oxidative stress is part of the pathologic features of hypertonic stress. The cellular response to hypertonic stress involves global decrease of protein synthesis, in a manner independent of eIF2a phosphorylation, the master regulator of most stress responses. Prior studies with Mouse Embryonic Fibroblast (MEF) cells in our lab have shown that osmotic stress triggers eIF2α phosphorylation, but it is not the cause of translational repression. MEFs deficient in eIF2α phosphorylation showed a dramatic decrease in protein synthesis when subjected to hyperosmolar treatment (Bevilaqua et. al., 2010). We are interested to investigate the mechanism of the eIF2a phosphorylation independent translational repression. A study reported in the literature, showed that oxidative stress induces tRNA cleavage in mammalian cells in a manner independent of phophorylation of eIF2α (Yamasaki et. al. 2009). We propose to study the involvement of this mechanism during hypertonic stress. This project aims to identify/quantify specific populations of cleaved tRNA fragments in MEFs under hypertonic stress using a microarray based technique. Selectivity if observed, may point to cleaved tRNA fragments being regulatory molecules in the osmotic stress signaling pathway. In addition we are also exploring the mechanism of translational repression caused by these tRNA fragments and the mechanism of tRNA substrate recognition for cleavage by specific nucleases.

References:
Bevilacqua E, Wang X, Majumder M, Gaccioli F, Yuan CL, Wang C, Zhu X, Jordan LE, Scheuner D, Kaufman RJ, Koromilas AE, Snider MD, Holcik M, Hatzoglou M (2010). eIF2alpha phosphorylation tips the balance to apoptosis during osmotic stress. J Biol Chem.;285(22):17098-111.

Yamasaki S, Ivanov P, Hu GF, Anderson P. (2009) Angiogenin cleaves tRNA and promotes stress-induced translational repression. J Cell Biol.;185(1):35-42.

Keywords: tRNA Cleavage, Hyperosmotic stress