Multiple ubiquitin-specific protease genes are involved in degradation of yeast tryptophan permease Tat2 at high pressure.

When Saccharomyces cerevisiae cells are exposed to high hydrostatic pressure, tryptophan permease Tat2 is degraded in a manner dependent on Rsp5 ubiquitin ligase. Consequently, cell growth is arrested in tryptophan auxotrophic strains. Here we show that of 17 ubiquitin-specific protease genes (UBP), deletion of DOA4, UBP6 or UBP14 causes stabilization of Tat2 and hence the cells can grow at 25 MPa. These disruptant cells displayed marked sensitivity to the arginine analogue canavanine. Internal free ubiquitin decreased 2- to 5-fold upon UBP deletion, although overproduction of ubiquitin did not affect their high-pressure growth and canavanine sensitivity. These results suggest that multiple ubiquitin-specific proteases are involved in pressure-induced degradation of Tat2, rather than free ubiquitin depletion.