A YEAST PROTEIN THAT INFLUENCES THE CHROMATIN STRUCTURE OF UASG AND FUNCTIONS AS A POWERFUL AUXILIARY GENE ACTIVATOR

GRF2, an abundant yeast protein of Mr ∼127,000, binds to the GAL upstream activating sequence (UASG) and creates a nucleosome-free region of ∼230 bp. Purified GRF2 binds to sequences found in many other UASs, in the 35S rRNA enhancer, at centromeres, and at telomeres. Although GRF2 stimulates transcription only slightly on its own, it combines with a neighboring weak activator to give as much as a 170-fold enhancement. This effect of GRF2 is strongly distance-dependent, declining by 85% when 22 bp is interposed between the GRF2 and neighboring activator sites.