Conservation of sequence and structure flanking the mouse and human β-globin loci: The β-globin genes are embedded within an array of odorant receptor genes

In mouse and human, the β-globin genes reside in a linear array that is associated with a positive regulatory element located 5′ to the genes known as the locus control region (LCR). The sequences of the mouse and human β-globin LCRs are homologous, indicating conservation of an essential function in β-globin gene regulation. We have sequenced regions flanking the β-globin locus in both mouse and human and found that homology associated with the LCR is more extensive than previously known, making up a conserved block of ≈40 kb. In addition, we have identified DNaseI-hypersensitive sites within the newly sequenced regions in both mouse and human, and these structural features also are conserved. Finally, we have found that both mouse and human β-globin loci are embedded within an array of odorant receptor genes that are expressed in olfactory epithelium, and we also identify an olfactory receptor gene located 3′ of the β-globin locus in chicken. The data demonstrate an evolutionarily conserved genomic organization for the β-globin locus and suggest a possible role for the β-globin LCR in control of expression of these odorant receptor genes and/or the presence of mechanisms to separate regulatory signals in different tissues.