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

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RESUMO

The GCR1 gene product is required for maximal transcription of many yeast genes including genes encoding glycolytic enzymes. Transcription of the yeast enolase gene ENO2 is reduced 50-fold in strains carrying a gcr1 null mutation. cis-acting sequences that are sufficient for GCR1-dependent regulation of ENO2 expression were identified by using an enhancerless CYC1 promoter which is not normally dependent on GCR1 for expression. A 60-bp ENO2 sequence that was sufficient to provide high-level, GCR1-dependent transcriptional activation of the CYC1 promoter was identified. This 60-bp element could be subdivided into a 30-bp sequence containing a novel RAP1-binding site and a GCR1-binding site which did not activate CYC1 transcription and a 30-bp sequence containing a novel enhancer element that conferred moderate levels of GCR1-independent transcriptional activation. The 60-bp CGCR1-dependent upstream activator sequence is located immediately downstream from previously mapped overlapping binding sites for the regulatory proteins ABFI and RAP1. Evidence is presented that the overlapping ABFI- and RAP1-binding sites function together with sequences that bind GCR1 and RAP1 to stage transcriptional activation of ENO2 expression.

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