A CARBON SOURCE-RESPONSIVE PROMOTER ELEMENT NECESSARY FOR ACTIVATION OF THE ISOCITRATE LYASE GENE ICL1 IS COMMON TO GENES OF THE GLUCONEOGENIC PATHWAY IN THE YEAST SACCHAROMYCES-CEREVISIAE

The expression of yeast genes encoding gluconeogenic enzymes depends s trictly on the carbon source available in the growth medium. We have c haracterized the control region of the isocitrate lyase gene ICL1, whi ch is derepressed more than 200-fold after transfer of cells from ferm entative to nonfermentative growth conditions. Deletion analysis of th e ICL1 promoter led to the identification of an upstream activating se quence element, UAS(ICL1) (5' CATTCATCCG 3'), necessary and sufficient for conferring carbon source-dependent regulation on a heterologous r eporter gene. Similar sequence motifs were also found in the upstream regions of coregulated genes involved in gluconeogenesis. This carbon source-responsive element (CSRE) interacts with a protein factor, desi gnated Ang1 (activator of nonfermentative growth), detectable only in extracts derived from derepressed cells. Gene activation mediated by t he CSRE requires the positively acting derepression genes CAT1 (=SNF1 and CCR1) and CAT3 (=SNF4). In the respective mutants, Ang1-CSRE inter action was no longer observed under repressing or derepressing conditi ons. Since binding of Ang1 factor to the CSRE could be completed for b y an upstream sequence derived from the fructose-1,6-bisphosphatase ge ne FBP1, we propose that the CSRE functions as a UAS element common to genes of the gluconeogenic pathway.