A SACCHAROMYCES-CEREVISIAE UAS ELEMENT CONTROLLED BY PROTEIN KINASE-AACTIVATES TRANSCRIPTION IN RESPONSE TO A VARIETY OF STRESS CONDITIONS

Transcription of the Saccharomyces cerevisiae CTT1 gene encoding the c ytosolic catalase T is activated by a variety of stress conditions: it is derepressed by nitrogen starvation and induced by heat shock. Furt hermore, it is activated by osmotic and oxidative stress. This study s hows that a CTT1 upstream region previously found to be involved in ni trogen, cAMP and heat control (base pairs -382 to -325) contains a UAS element (STRE, -368 to -356), which is sufficient for the activation of a reporter gene by all types of stress acting on CTT1. Gel retardat ion experiments demonstrated the existence of a factor specifically bi nding to STRE, but to a lesser extent to mutated elements having partl y or entirely lost the ability to mediate stress control. Heat activat ion of STRE, but not of a canonical heat shock element, is enhanced by a ras2 defect mutation, which enhances thermotolerance, and is dramat ically reduced by a bcy1 disruption mutation, which decreases thermoto lerance. It can be hypothesized, therefore, that the novel stress cont rol element is important for the establishment of induced stress toler ance.