An insulator element and condensed chromatin region separate the chicken beta-globin locus from an independently regulated erythroid-specific folate receptor gene

We have identified a folate receptor gene upstream of the chicken beta-glob in locus and separated from it by a 16 kbp region of silent chromatin, We f ind that this receptor is expressed only at a stage of erythroid differenti ation (CFU-E) preceding the activation of beta-globin genes, consistent wit h the role of folate receptors in proliferation. This discovery raises the question of how these two loci are regulated during erythropoiesis. Our dat a suggest that the folate receptor gene and the beta-globin locus are regul ated independently. We show that a 3.3 kbp DNA region upstream of the folat e receptor gene is sufficient to induce strong expression of a transgene in CFU-E stage cells. We also find that the region between the beta-globin lo cus and the folate receptor gene is fully methylated and condensed at this stage of differentiation. Its 3' boundary coincides with the 5' beta-globin insulator. We speculate that the 5' beta-globin boundary element might be important for the proper regulation of two adjacent domains activated at tw o different stages during differentiation.