The structure and transcription of four linked rabbit β-like globin genes

Rabbit chromosomal DNA contains a cluster of four linked β-like globin genes arranged in the orientation 5′-β4-(8 kb)-β3-(5 kb)-β2-(7 kb)-β1-3′. Determination of the nucleotide sequence of gene β1 confirms that this gene corresponds to the second type of two common co-dominant alleles encoding the adult β-globin chain. With the exception of two nucleotide substitutions in the large intervening sequence (intron), the intron and flanking sequences are identical with the nucleotide sequence of the first type determined by Weissmann et al. (1979). A 14S polyadenylated transcript containing large intron sequences (possibly a mRNA precursor) is detected in the bone marrow cells of anemic rabbits. Gene β2 has limited sequence homology to adult and embryonic β-globin probes and lacks a detectable mRNA transcript in the erythropoietic tissues examined. It contains at least one intervening sequence analogous to the large intron in gene β1. Genes β3 and β4 both contain an intron of 0.8 kb. Partial DNA sequence analysis indicates that the large intron in β4 is located between codons for amino acids lysine and leucine in an analogous position to that of the large intron in β1. In addition, a second smaller intron interrupts the 5′ coding sequences of gene β4. Both genes β3 and β4 are transcribed in embryonic globin-producing cells. Their DNA sequence homology is limited, however, to a segment of approximately 0.2 kb located on the 5′ side of the large intron.