RRM
2007 Rustbelt RNA Meeting
RRM
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Poster abstracts
Abstract:
In Saccharomyces cerevisiae, tRNAs are not only exported from the nucleus to the cytoplasm, but also undergo retrograde movement that returns tRNAs to the nucleus. Cells harboring conditional defects in tRNA aminoacylation or starved for various nutrients accumulate tRNAs, which were previously located in the cytoplasm, with in their nuclei. To uncover novel factors important for tRNA nuclear export and/or re-export, a screen for muliticopy suppressors of temperature sensitive growth inhibition caused by the tys1-1 mutation was conducted and Sbp1 and Tat1 were identified. Tat1 is an amino acid permerase that imports amino acids from the media into the cytoplasm. The increased intracellular pools of tyrosine, resulting from TAT1 overexpression, may suppress the growth inhibition and tRNA nuclear accumulation caused by the tys1-1 mutation by increasing the rate of aminoacylation. Sbp1 is a cytoplasmic protein of unknown function that has a nuclei acid binding motif and is involved in glucose starvation induced P-body formation and translational repression. Overexpression of Sbp1 has been previously shown to cause translational repression independent of starvation (Segal et al., 2006), while deletion of SBP1 enhances the defect in translation repression caused by deletion of DHH1 or PAT1 (Dhh1 and Pat1 function in parallel to promote P-body formation; Segal et al., 2007). Additionally, dhh1pat1 cells do not accumulate tRNA with nuclei in response to glucose or amino acid starvation. One possible explanation undergoing testing is that overexpression of Sbp1 allows translation to continue in cells containing the tys1-1 mutation by altering the rate of translation initiation to match the availability of aminoacylated tRNATyr, thereby preventing stress signaling caused by impaired translation.
Keywords: tRNA, translation, nutrient starvation
