Poster abstracts

Poster number 7 submitted by Hui-Yi Chu

Strategy to learn the function of the tRNA retrograde pathway via polysome RNAs and microarray analyses

Hui-Yi Chu (MCDB, the Ohio State University), Anita K Hopper (Department of Molecular Genetics, the Ohio State University)

Abstract:
In eukaryotic cells, tRNAs are transcribed in the nucleus and previously were thought to be unidirectly transported to the cytoplasm for function in protein synthesis. However, our recent studies showed that cytoplasmic tRNAs accumulate in the nucleus following amino acid deprivation in yeast and rat hepatoma cells (Shaheen and Hopper, 2005; Shaheen et al, 2007). Upon re-feeding, cytoplasmic tRNAs accumulated in the nucleus are re-exported to the cytoplasm. Current data indicate that tRNA movement includes three steps: 1) primary export of partially matured tRNA; 2) retrograde movement of tRNA into nucleus; 3) re-export of fully mature tRNA to the cytoplasm. At least three members of the β-importin family participate in tRNA subcellular dynamics. Los1 functions in step 1, Mtr10 in step 2, and Msn 5 in step 3. However, it remains unclear what the ultimate cellular consequences are of the tRNA nuclear accumulation. We propose that the retrograde process helps to regulate protein synthesis in response to nutrient deprivation. To test this hypothesis, our strategy is to monitor changes in mRNAs associated with polysomes. Therefore, we are investigating changes of protein synthesis by analyzing polysome profiles and by microarray analysis using polysomal mRNAs isolated from mtr10 and msn5 mutants grown in the presence or absence of amino acids.

Keywords: tRNA, transport, polysomes