The UAS of the yeastPGKgene contains functionally distinct domains

The upstream activation site (UAS) of the yeast phosphoglycerate kinase gene (PGK) has been localised by deletion analysis (1). Here we show that the UASPGK contains two functionally distinct domains. These two domains, designated activator (A) and modulator (M), appear to be located within bases -460 to -402 and -531 to -461, respectively, relative to the initiating ATG; although it is possible that part of the M domain resides within the A domain. They have been shown, using a heterologous assay promoter, to have distinct transcriptional functions. Domain A is responsible for activation of transcription whilst domain M is required for carbon source dependent regulation of transcription. Protein-DNA binding studies have demonstrated that the DNA fragment containing domain M has high affinity for at least one specific DNA-binding protein, whilst domain A does not appear to interact strongly in protein-binding assays under the same conditions. The domain M binding activity is dependent on the carbon source in the growth medium and may be functional in the carbon source control of PGK expression.