Defect in the development of thermotolerance in the mouse temperature-sensitive mutant ts85 lacking ubiquitin-activating enzyme.

We investigated the effect of heat shock on the development of thermotolerance using mouse FM3A cells and the temperature-sensitive mutant ts85. The shift-up incubation of FM3A from 33 to 39.5 degrees induced thermotolerance to subsequent heating at 44 degrees. In contrast, the similar treatment of ts85 at the nonpermissive temperature of 39.5 degrees could not induce thermotolerance. Furthermore, when ts85 cells were treated at 33 degrees after being heated at 44 degrees, they developed a reduced level of thermotolerance as compared with that developed in FM3A cells. Since ts85 cells are defective in ubiquitin-activating enzyme, these results suggest a role of the ubiquitin-protein conjugation system in the development of thermotolerance.