Molecular cloning and characterization of two sets of alpha-theta genes inthe rat alpha-like globin gene cluster

The highly heterogeneous rat hemoglobin system was investigated at the gene level. Two regions of the alpha-like globin gene cluster from a Wistar rat were isolated. Four lambda Dash recombinant clones carrying rat alpha-like globin genes were localized on two distinct gene regions. A region of appr oximately 16 kb was found to contain the 5'-(II)alpha 1-psi theta 1-3' loci , and another of approximately 24 kb the 5'-(II)alpha 2-psi theta 2-psi(I)a lpha 3-3' loci. Both (II)alpha 1 and (II alpha)2 are considered to be activ e, coding the (II)alpha-globin chain. The nt sequences of (II)alpha 1 and ( II)alpha 2 are identical except for six nt in the non-coding region. The ps i(I)alpha 3 locus is a truncated pseudogene. The putative promoter region o f an alpha-like globin gene is joined directly to the third exon, homologou s to that of (1)alpha-globin cDNA. psi theta 1 and psi theta 2 are also pse udogenes, as evidenced by several deletions located in the protein-coding r egions of these loci. The psi theta 1 and psi theta 2 loci exhibit extensiv e homology, but the restriction maps of these genes and their flanking regi ons differ considerably. Genomic Southern blot analyses of the total liver DNA from six rats showed the existence of three theta-globin-related genes, including psi theta 1 and psi theta 2. These results indicate that the two gene regions investigated are not allelic variants, but may be generated b y block duplication. This is the first report of the existence of rodent th eta-globin genes. (C) 1999 Elsevier Science B.V. All rights reserved.