Abstract

The highly heterogeneous rat hemoglobin system was investigated at the gene level. Two regions of the α-like globin gene cluster from a Wistar rat were isolated. Four λ Dash recombinant clones carrying rat α-like globin genes were localized on two distinct gene regions. A region of approximately 16 kb was found to contain the 5′-IIα1-ψθ1-3′ loci, and another of approximately 24 kb the 5′-IIα2-ψθ2-ψIα3-3′ loci. Both IIα1 and IIα2 are considered to be active, coding the IIα-globin chain. The nt sequences of IIα1 and IIα2 are identical except for six nt in the non-coding region. The ψIα3 locus is a truncated pseudogene. The putative promoter region of an α-like globin gene is joined directly to the third exon, homologous to that of Iα-globin cDNA. ψθ1 and ψθ2 are also pseudogenes, as evidenced by several deletions located in the protein-coding regions of these loci. The ψθ1 and ψθ2 loci exhibit extensive homology, but the restriction maps of these genes and their flanking regions differ considerably. Genomic Southern blot analyses of the total liver DNA from six rats showed the existence of three θ-globin-related genes, including ψθ1 and ψθ2. These results indicate that the two gene regions investigated are not allelic variants, but may be generated by block duplication. This is the first report of the existence of rodent θ-globin genes.

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