Plasmids containing mouse cDNA encoding haptoglobin, a major plasma protein that binds free hemoglobin, have been isolated and characterized. The amino acid sequence predicted by the mouse haptoglobin cDNA was 80% identical to human haptoglobin and 90% identical to rat haptoglobin sequence. The mouse haptoglobin probe was used to demonstrate a single haptoglobin gene in the genome of C57BL6 mice mapped to chromosome 8. Sequence analysis of the mouse Hp gene promoter revealed two unique features: the presence of a second TATA box with a 48-bp trinucleotide repeat immediately upstream. The enhancer element and the sequences shown to be required for cytokine and hormonal regulation of the rat lip gene are highly conserved in mouse. Interestingly, the single nucleotide variation G to A, which completely inactivates the IL-6 responsive element A in the rat Hp gene, is identical in mouse. This suggests that the presence of an inactive IL-6-responsive element A in Hp genes is common in rodents.
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