The nucleotide sequence of the rabbit embryonic globin gene beta 4.

In the rabbit, two beta-like globin genes, beta 3 and beta 4, are expressed in embryonic erythrocytes and one, beta 1, is expressed in fetal and adult erythrocytes. The complete nucleotide sequence of embryonic gene beta 4 is presented, including the region from 582 base pairs before the cap site to 508 base pairs after the poly(A) addition site. beta 4 has the tripartite structure characteristic of animal globin genes, being interrupted by intervening sequences within codon 30 and between codons 104 and 105. Conserved sequences thought to play roles in transcription, RNA processing, and translation are found in beta 4. Rabbit gene beta 4 shows substantial homology to the human embryonic epsilon-globin gene, not only in message-coding blocks, but also in the 5' and 3' flanking regions and in the two intervening sequences. Comparison of all four rabbit beta-like genes with those of humans suggests that a primordial four gene family, 5'-epsilon-gamma-delta-beta-3', existed prior to the mammalian radiation. An alignment of the 5' flanking sequences of a collection of animal beta-like globin genes shows some conserved regions that differ between the adult genes and the embryonic/fetal genes. These could reflect a common evolutionary lineage rather than stage-specific control sequences.