Stm1p, a Ribosome-associated Protein, is Important for Protein Synthesis in Saccharomyces cerevisiae under Nutritional Stress Conditions

Stm1p is a Saccharomyces cerevisiae protein that has been implicated in several biological processes, ranging from apoptosis to telomere biosynthesis. Likewise, Stm1p has been identified as a protein associated with supramolecular structures, including ribosomes and nuclear telomere cap complexes. Using a variety of biochemical methods, we found that the vast majority of cellular Stm1p is associated with free cytosolic 80 S ribosomes and polysomes. In its association with ribosomes, Stm1p interacts in an equimolar complex with both ribosomal subunits and is not associated with mRNA. Functionally, targeted disruption of the STM1 gene results in rapamycin hypersensitivity and a defect in recovery following nitrogen starvation and replenishment. These effects coincide with severe polysome depletion and reduced total protein synthesis. Taken together, our data indicate that Stm1p plays a critical role in facilitating translation under nutrient stress conditions and suggest that Stm1p acts in concert with the target of rapamycin (TOR) signaling pathway.