Negative regulation of transcription of the Saccharomyces cerevisiae catalase T (CTT1) gene by cAMP is mediated by a positive control element.

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Transcription of the CTT1 (catalase T) gene of Saccharomyces cerevisiae is controlled by oxygen via heme, by nutrients via cAMP and by heat shock. Nitrogen limitation triggers a rapid, cycloheximide-insensitive derepression of the gene. Residual derepression in a cAMP-nonresponsive mutant with attenuated protein kinase activity (bcy1 tpk1w tpk2 tpk3) demonstrates the existence of an alternative, cAMP-independent nutrient signaling mechanism. Deletion analysis using CTT1-lacZ fusion genes revealed the contribution of multiple control elements to derepression, not all of which respond to the cAMP signal. A positive promoter element responding to negative control by cAMP was inactivated by deletion of a DNA region between base pairs -340 and -364. Upstream fragments including this element confer negative cAMP control to a LEU2-lacZ fusion gene. Northern analysis of CTT1 expression in the presence or absence of heme, in RAS2+ (high cAMP) and ras2 mutant (low cAMP) strains and in cells grown at low temperature (23 degrees C) and in heat-shocked cells (37 degrees C) shows that CTT1 is only induced to an appreciable extent when at least two of the three factors contributing to its expression (oxidative stress signaled by heme, nutrient starvation (low cAMP) and heat stress) activate the CTT1 promoter.

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