Characterization, expression, and evolution of the mouse embryonic zeta-globin gene

We have determined the complete sequence of the embryonic alpha-like, zeta (zeta)-globin gene of the BALB/c mouse. The structure of this gene establishes the amino acid sequence of the mouse embryonic zeta-globin polypeptide chain and allows us to identify sequences within the gene that may be important for its expression. One of these is a 300-base segment that is tightly conserved between mice and humans and is located at the 5' end of the zeta-globin gene. By introducing the cloned gene into permanently transfected mouse erythroleukemic cell lines and comparing its transcript with that of zeta-globin mRNA derived from embryonic yolk sac erythrocytes, we are able to show that the cloned gene is transcriptionally active and that its transcript is correctly initiated and processed. Interestingly, the zeta-globin gene is also active when permanently transfected into an immunoglobulin-producing B-cell, a cell that presumably has tissue-specific requirements for gene expression. Further, a comparison of the amino acid coding sequence of the mouse zeta-globin gene to that of zeta-like globin genes of other species supports a revised evolutionary lineage in which goats and humans are closely related, whereas mice are further removed.