SYNERGY BETWEEN TREHALOSE AND HSP104 FOR THERMOTOLERANCE IN SACCHAROMYCES-CEREVISIAE

We isolated a mutant strain unable to acquire heat shock resistance in stationary phase. Two mutations contributed to this phenotype. One mu tation was at the TPS2 locus, which encodes trehalose-G-phosphate phos phatase. The mutant fails to make trehalose and accumulates trehalose- 6-phosphate. The other mutation was at the HSP104 locus. Gene disrupti ons showed that tps2 and hsp104 null mutants each produced moderate he at shock sensitivity in stationary phase cells. The two mutations were synergistic and the double mutant had little or no stationary phase-i nduced heat shock resistance. The same effect was seen in the tps1 (tr ehalose-6-phosphate synthase) hsp104 double mutant, suggesting that th e extreme heat shock sensitivity was due mainly to a lack of trehalose rather than to the presence of trehalose-6-phosphate. However, accumu lation of trehalose-6-phosphate did cause some phenotypes in the tps2 mutant, such as temperature sensitivity for growth. Finally, we isolat ed a high copy number suppressor of the temperature sensitivity of tps 2 which we call PMU1, which reduced the levels of trehalose-6-phosphat e in tps2 mutants. The encoded protein has a region homologous to the active site of phosphomutases.