A MAJOR POSITIVE REGULATORY REGION LOCATED FAR UPSTREAM OF THE HUMAN ALPHA-GLOBIN GENE LOCUS

We have identified a remote, tissue-specific, positive regulatory element that is of major importance in determining the level of human α-globin gene expression. Stable transformants containing this DNA segment linked to the α gene in mouse erythroleukemia cells expressed human α mRNA at levels that are indistinguishable from those seen in interspecific hybrids containing the human α genes in their normal context on chromosome 16. Furthermore, all transgenic mice containing the α genes linked to this region expressed α-globin mRNA at high levels in erythroid tissues; and in one such mouse, readily detectable levels of human α-globin chains could be demonstrated in the peripheral blood. There is considerable similarity in the position, structure, and function of this region upstream of the α-globin complex with previously described elements within the β-globin dominant control region (DCR). This is in marked contrast to other structural and functional differences between the two gene clusters. It seems likely that these critical, positive regulatory regions might provide target sequences through which coordinate regulation of the α- and β-like globin genes is achieved.