EVIDENCE THAT THE SACCHAROMYCES-CEREVISIAE CIFI (GGS1 TPSI) GENE MODULATES HEAT-SHOCK RESPONSE POSITIVELY/

The CIF1 gene (also called GGSI/TPS1) encodes a protein of the trehalo se synthase complex that affects trehalose accumulation and general gl ucose sensing by Saccharomyces cerevisiae cells, There is considerable debate as to whether CIF1-dependent trehalose accumulation is a deter minant in heat shock-acquired thermotolerance, Thermosensitivity of ci f1 mutants could alternatively or also, be related to gene expression- signalling defects in such strains, Because many signal-dependent fact ors are involved in stress protection and repair in yeast, we have com pared the expression of various stress response and heat shock genes i n 'isogenic' CIF1 and cif1 strains growing exponentially in galactose medium, Transcription of CTT1, CIF1, HSP26, HSP82, HSP104 SSA4 and UBI 4 nas notably lower in the cif1 mutant following heat shock, Moreover, a single copy of chromosomally integrated HSP104-lacZ fusion gave up to 5.5-fold more heat shock induction in the CIF1 strain compared to t he cif1 mutant, We conclude that reduced heat shock-acquired thermotol erance in cif1-deletion mutants growing exponentially on galactose is more likely to result from a general reduction in expression of stress response and heat shock genes, than simply or solely through deficien cy of trehalose accumulation, The possible role of CIF1 in modulating stress response is discussed.