High cAMP levels antagonize the reprogramming of gene expression that occurs at the diauxic shift in Saccharomyces cerevisiae

In order to analyse the involvement of the cAMP pathway in the regulation of gene expression in Saccharomyces cerevisiae, we have examined the effect of cAMP on protein synthesis by using two-dimensional gel electrophoresis. cAMP had only a minor effect on the protein pattern of cells growing exponentially on glucose. However, it interfered with the changes in gene expression normally occurring upon glucose exhaustion in yeast cultures, maintaining a protein pattern typical of cells growing on glucose. This effect was accompanied by a delay before growth recovery on ethanol. We propose a model in which the cAMP-signalling pathway has a role in the maintenance of gene expression, rather than in the determination of a specific programme. A decrease of cAMP would then be required for metabolic transitions such as the diauxic phase.