A complex regulatory element from the yeast gene ENO2 modulates GCR1-dependent transcriptional activation

The GCR1 gene product is required for maximal transcription of many yeast genes including genes encoding glycolytic enzymes. Transcription of the yeast enolase gene EN02 is reduced 50-fold in strains carrying a gcrl null mutation. cis-acting sequences that are sufficient for GCRI-dependent regulation ofEN02 expression were identified by using an enhancerless CYC1 promoter which is not normally dependent on GCR1 for expression. A 60-bp EN02 sequence that was sufficient to provide high-level, GCRI-dependent transcriptional activation of the CYCi promoter was identified. This 60-bp element could be subdivided into a 30-bp sequence containing a novel RAPl-binding site and a GCR1-binding site which did not activate CYCi transcription and a 30-bp sequence containing a novel enhancer element that conferred moderate levels of GCRI-independent transcrip-tional activation. The 60-bp GCRI-dependent upstream activator sequence is located immediately downstream from previously mapped overlapping binding sites for the regulatory proteins ABFI and RAPI. Evidence is presented that the overlapping ABFI- and RAPl-binding sites function together with sequences that bind GCR1 and RAP1 to stage transcriptional activation ofEN02 expression. Genes encoding enzymes of the glycolytic pathway are expressed coordinately in response to changes in the carbon source and growth phase. Investigations of the upstrea