FLANKING AND INTRAGENIC SEQUENCES REGULATING THE EXPRESSION OF THE RABBIT ALPHA-GLOBIN GENE

Despite their descent from a common ancestral gene and the requirement for coordinated, tissue-specific regulation, the alpha- and beta-glob in genes in many mammals are regulated in distinctly different ways. U nlike the beta-globin gene, the rabbit alpha-globin gene is transientl y expressed at a high level without an added enhancer in transfected e rythroid and non-erythroid cells. By examining a series of alpha/beta fusion genes, we show that internal sequences of the rabbit alpha-glob in gene (within the first two exons and introns) are required along wi th the 5' flank for this enhancer-independent expression. Furthermore, deletion of the introns of the alpha-globin gene, or replacement by i ntrons of the beta-globin gene, results in severely decreased expressi on of the transfecting genes, Hybrid constructs between segments of th e alpha-globin gene and a luciferase gene confirm that internal alpha- globin sequences are needed for high level production of RNA in transf ected cells, The flanking and internal sequences implicated in regulat ion of the rabbit alpha-globin gene coincide with a prominent CpG-rich island and may comprise an extended promoter (including both flanking and intragenic sequences) that is active in transfected cells without an enhancer,