Very low amounts of glucose cause repression of the stress-responsive gene HSP12 in Saccharomyces cerevisiae

Abstract

Changing the growth mode of Saccharomyces cerevisiae by adding fermentable amounts of glucose to cells growing on a non-fermentable carbon source leads to rapid repression of general stress-responsive genes like HSP12. Remarkably, glucose repression of HSP12 appeared to occur even at very low glucose concentrations, down to 0005 %. Although these low levels of glucose do not induce fermentative growth, they do act as a growth signal, since upon addition of glucose to a concentration of 002 %, growth rate increased and ribosomal protein gene transcription was up-regulated. In an attempt to elucidate how this type of glucose signalling may operate, several signalling mutants were examined. Consistent with the low amounts of glucose that elicit HSP12 repression, neither the main glucose-repression pathway nor cAMP-dependent activation of protein kinase A appeared to play a role in this regulation. Using mutants involved in glucose metabolism, evidence was obtained suggesting that glucose 6-phosphate serves as a signalling molecule. To identify the target for glucose repression on the promoter of the HSP12 gene, a promoter deletion series was used. The major transcription factors governing (stress-induced) transcriptional activation of HSP12 are Msn2p and Msn4p, binding to the general stress-responsive promoter elements (STREs). Surprisingly, glucose repression of HSP12 appeared to be independent of Msn2/4p : HSP12 transcription in glycerol-grown cells was unaffected in a ∆msn2∆msn4 strain. Nevertheless, evidence was obtained that STRE-mediated transcription is the target of repression by low amounts of glucose. These data suggest that an as yet unidentified factor is involved in STRE-mediated transcriptional regulation of HSP12.

A Rapid Method to Determine the Stress Status of Saccharomyces cerevisiae by Monitoring the Expression of a Hsp12:Green Fluorescent Protein (GFP) Construct under the Control of the Hsp12 Promoter

“…This agrees with previous studies that expression of the HSP12 gene is suppressed by even small quantities of glucose in the growth medium. 27 Continued growth into the stationary phase resulted in the yeast appearing fluorescent (Fig. 3A,B).…”

Comparative Transcriptome Analysis Reveals Novel Roles of the Ras and Cyclic AMP Signaling Pathways in Environmental Stress Response and Antifungal Drug Sensitivity in Cryptococcus neoformans

“…In S. cerevisiae, HSP12 expression is undetectable under unstressed, glucoserich conditions but is highly induced in response to a wide range of environmental stresses, such as heat or cold shock, osmotic shock, desiccation, and exposure to alcohol or oxidative damage agents (51,59,66,71,72). Interestingly, even a very low concentration of glucose (0.005%) can repress HSP12 expression (18). In C. neoformans, however, HSP12 and HSP122 were highly expressed even under unstressed conditions with abundant glucose (2%).…”

Genomic organization of the Neurospora crassa gsn gene: possible involvement of the STRE and HSE elements in the modulation of transcription during heat shock

“…However, in N. crassa, heat shock down-regulates transcription of the gsn gene, and this regulation may depend also on the STRE and HSE motifs present in the promoter region, as we have shown here. The involvement of STRE as a transcriptional repressor was previously demonstrated for the HSP12 gene in S. cerevisiae when cells were transferred to a medium containing very low amounts of glucose (Groot et al 2000). In addition, these authors suggested that the gene repression was independent of Msn2/4p.…”