DNA-binding properties of the yeast transcriptional activator,Gcr1p

In Saccharomyces cerevisiae the GCR1 gene product is required for high-level expression of genes encoding glycolytic enzymes. In this communication, we extend our analysis of the DNA binding properties of Gcr1p. The DNA-binding domain of Gcr1p binds DNA with high affinity. The apparent dissociation constant of the Gcr1p DNA-binding domain for one of its specific binding sites (TTTCAGCTTCCTCTAT) is 2·9×10⁻¹⁰ M. However, competition experiments showed that Gcr1p binds this site in vitro with a low degree of specificity. We measured a 33-fold difference between the ability of specific competitor and DNA of random sequence to inhibit the formation of nucleoprotein complexes between Gcr1p and a radiolabeled DNA probe containing its binding site. DNA band-shift experiments, utilizing probes of constant length in which the positions of Gcr1p-binding sites are varied relative to the ends, indicated that Gcr1p–DNA nucleoprotein complexes contain bent DNA. The implications of these findings in terms of the combinatorial interactions that occur at the upstream activating sequence elements of genes encoding glycolytic enzymes are discussed.