HIGH CAMP LEVELS ANTAGONIZE THE REPROGRAMMING OF GENE-EXPRESSION THATOCCURS AT THE DIAUXIC SHIFT IN SACCHAROMYCES-CEREVISIAE

In order to analyse the involvement of the cAMP pathway in the regulat ion of gene expression in Saccharomyces cerevisiae, we have examined t he effect of cAMP on protein synthesis by using two-dimensional gel el ectrophoresis. cAMP had only a minor effect on the protein pattern of cells growing exponentially on glucose. However, it interfered with th e changes in gene expression normally occurring upon glucose exhaustio n in yeast cultures, maintaining a protein pattern typical of cells gr owing 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.