BIOCHEMICAL-CHARACTERIZATION OF THE DEVELOPMENTAL STAGE-SPECIFIC AND TISSUE-SPECIFIC ERYTHROID TRANSCRIPTION FACTOR, NF-E4

Analysis of the nuclear factors responsible for erythroid gene regulat ion has led to the cloning of several transcriptional regulatory prote ins with clear lines of evidence suggesting or demonstrating their rol es in tissue-specific gene expression. However, the erythroid cell lin eage-restricted proteins that have been characterized to date do not d iffer significantly in activity during the distinct developmental stag es of erythropoiesis, a characteristic that might be expected for a nu clear factor that actively participates in the differential regulation of various alpha- or beta-type globin genes (called globin gene switc hing) at distinct stages of embryonic development. We reported previou sly the identification of such a differentially expressed DNA binding activity, which appeared to be present in mature definitive (adult) er ythroid cells but absent in immature definitive or primitive (embryoni c) erythroid cells. Here we detail the biochemical properties of this erythroid tissue- and developmental stage-specific DNA binding activit y (called nuclear factor-erythroid 4; NF-E4), which contains character istics of a molecule that may be intimately involved in globin gene sw itching.