TRANSACTIVATION OF A GLOBIN PROMOTER IN NONERYTHROID CELLS

We show that expression in fibroblasts of a single cDNA, encoding the erythroid DNA-binding protein Eryfl (GF-1, NF-E1), very efficiently activates transcription of a chicken alpha-globin promoter. trans-Activation in these cells occurred when Eryfl bound to a single site within a minimal globin promoter. In contrast, efficient activation in erythroid cells required multiple Eryfl binding sites. Our results indicate that mechanisms exist that are capable of modulating the trans-acting capabilities of Eryfl in a cell-specific manner, without affecting DNA binding. The response of the minimal globin promoter to Eryfl in fibroblasts was at least as great as for optimal constructions in erythroid cells. Therefore, the assay provides a very simple and sensitive system with which to study gene activation by a tissue-specific factor.