Uncoating ATPase is a member of the 70 kilodalton family of stress proteins

The synthetic peptide, VGIDLGTTYSC, derived from the heat shock-induced genes human hsp70, Drosophila hsp70, S. cerevisiae YG100, and E. coli dnaK, elicited antibodies that recognized two constitutive proteins in bovine extracts. One of these proteins, 71 kd, has previously been identified as uncoating ATPase, an enzyme that releases clathrin from coated vesicles. This immunological data complemented the result that uncoating ATPase was indistinguishable from the constitutive mammalian 71 kd stress protein by either partial proteolytic mapping or two-dimensional gel analysis. In addition, affinity-purified uncoating ATPase antibodies recognize proteins in yeast identified as the gene products of the heat shock or heat shock cognate genes YG100 and YG102. The results show that uncoating ATPase is a member of the 70 kd heat shock protein family.     

Differential regulation of glutaredoxin gene expression in response to stress conditions in the yeast Saccharomyces cerevisiae

Glutaredoxins are small heat-stable proteins that are active as glutathione-dependent oxidoreductases and are encoded by two genes, designated GRX1 and GRX2, in the yeast Saccharomyces cerevisiae. We report here that the expression of both genes is induced in response to various stress conditions including oxidative, osmotic, and heat stress and in response to stationary phase growth and growth on non-fermentable carbon sources. Furthermore, both genes are activated by the high-osmolarity glycerol pathway and negatively regulated by the Ras-protein kinase A pathway via stress-responsive STRE elements. GRX1 contains a single STRE element and is induced to significantly higher levels compared to GRX2 following heat and osmotic shock. GRX2 contains two STRE elements, and is rapidly induced in response to reactive oxygen species and upon entry into stationary phase growth. Thus, these data support the idea that the two glutaredoxin isoforms in yeast play distinct roles during normal cellular growth and in response to stress conditions.     

Transcriptional regulation of an hsp70 heat shock gene in the yeast Saccharomyces cerevisiae.

The yeast Saccharomyces cerevisiae contains three heat-inducible hsp70 genes. We have characterized the promoter region of the hsp70 heat shock gene YG100, that also displays a basal level of expression. Deletion of the distal region of the promoter resulted in an 80% drop in the basal level of expression without affecting expression after heat shock. Progressive-deletion analysis suggested that sequences necessary for heat-inducible expression are more proximal, within 233 base pairs of the initiation region. The promoter region of YG100 contains multiple elements related to the Drosophila melanogaster heat shock element (HSE; CnnGAAnnT TCnnG). Deletion of a proximal promoter region containing one element, HSE2, eliminated most of the heat-inducible expression of YG100. The upstream activation site (UAS) of the yeast cytochrome c gene (CYC1) can be substituted by a single copy of HSE2 plus its adjoining nucleotides (UASHS). This hybrid promoter displayed a substantial level of expression before heat shock, and the level of expression was elevated eightfold by heat shock. YG100 sequences that flank UASHS inhibited basal expression of UASHS in the hybrid promoter but not its heat-inducible expression. This inhibition of basal UASHS activity suggests that negative regulation is involved in modulating expression of this yeast heat shock gene.     

Heat shock inhibits the induced expression of the SOS genes and SoxRS regulons in Escherichia coli

Oxidative stress formed in Escherichia coli cells is known to bring about a complex induction of alternative DNA repair processes, including SOS, SoxRS, and heat-shock response (HSR). The modification by heat shock of the expression of sfiA and soxS genes induced by oxidative agents H2O2, menadione and 4-nitroquinoline-1-oxide (4NQO) was studied for the first time. Quantitative parameters of gene expression were examined in E. coli strains with fused genes (promoters) sfiA::lacZ and soxS::lacZ. The expression of these genes induced by cell treatment with H2O2, but not menadione or 4NQO, was shown to decrease selectively after exposure to heat shock. Since genetic activity of menadione and 4NQO depends mainly on the formation of superoxide anion O2-, it is assumed that the effect of selective inhibition by heat-shock of sfiA and soxS gene expression in experiments with H2O2 is connected with activity of DnaK heat shock protein, which, unlike other heat-shock proteins, cannot be induced by superoxide anion O2-.