HS-48 alone has no enhancement role on the expression of human α-globin gene cluster

To investigate the in vivo function of the newly defined DNase I hypersensitive site HS-48 on the whole human α-globin gene cluster, the region containing all the other known 5 hypersensitive sites HS-4 to HS-40 was deleted from a 117 kb bacterial artificial chromosome clone bearing the whole human α-globin gene cluster. Transgenic mice were generated from this construct. The RNase protection assays showed that with HS-48 left and all the other 5 hypersensitive sites deleted, the expression of human α-like globin genes was completely silenced in embryonic, fetal and adult stages in all tissues. This finding indicates that HS-48 alone has no enhancer activity on the expression of human α-like globin genes, and that the region of HS-4 to HS-40 already contains all the upstream cis-elements needed for regulating human α-like globin genes.