Regulation of a yeast HSP70 gene by a cAMP responsive transcriptional control element.

HSP70 genes exhibit complex regulation in response to stress and a variety of cellular and developmental events. The SSA3 HSP70 gene of Saccharomyces cerevisiae is activated at the transcriptional level under conditions of nutrient limitation. Analysis of deletions revealed that cis-acting DNA sequences present immediately upstream and downstream of the previously identified heat shock elements (UASHS) mediate this regulation. A 35 bp region of SSA3, distinct from UASHS, contains sequences capable of activating a heterologous promoter following the diauxic shift and in the stationary phase of the yeast life cycle; this region has been designated an upstream activating sequence, UASPDS. Expression driven by UASPDS is regulated by the RAS/cAMP pathway. Reduced cAMP dependent protein kinase activity results in UASPDS dependent activation of the SSA3 promoter while constitutive cAMP dependent protein kinase activity prevents UASPDS mediated transcription, even under growth conditions that would normally result in full activation. Although the heat shock element alone exhibits no UAS activity under conditions in which UASPDS promotes transcription, UASHS interacts positively with UASPDS to mediate high levels of SSA3 transcription in response to nutrient limitation and lowered intracellular cAMP concentration. This interaction is independent of the precise spacing and relative orientation of the two elements.