Loss of protein quality control gene UBR1 sensitizes Saccharomyces cerevisiae to the aminoglycoside hygromycin B.

Ubr1 is a conserved ubiquitin ligase involved in the degradation of aberrant proteins in eukaryotic cells. The human enzyme is found mutated in patients with Johanson-Blizzard syndrome. We hypothesized that Ubr1 is necessary for optimal cellular fitness in conditions associated with elevated abundance of aberrant and misfolded proteins. Indeed, we found that loss of Ubr1 in the model eukaryotic microorganism Saccharomyces cerevisiae strongly sensitizes cells to hygromycin B, which reduces translational fidelity by causing ribosome A site distortion. Our results are consistent with a prominent role for Ubr1 in protein quality control. We speculate that disease manifestations in patients with Johanson-Blizzard syndrome are linked, at least in part, to defects in protein quality control caused by loss of Ubr1 function.