Lactoferrin gene promoter in human and mouse. Analogous and dissimilar characteristics.

Lactoferrin promoter and the 5'-flanking region of both human and mouse were isolated from a genomic library constructed with lambda phage. A 2.0 kbp Sac I fragment of the human clone (HLF031a.30) and a 3.0 kbp Eco R I/Hinc II fragment of the mouse clone (mL14p9E) containing the lactoferrin promoter, 5'-flanking region, first exon and partial intron were sequenced completely. There were many sequence homologies between human and mouse at the promoter/enhancer (1 to -363) region, yet substantial divergence was observed beyond this region. To determine the promoter activity, 5'-deletion mutants of the mouse lactoferrin gene were linked to a CAT-reporter plasmid and transfected into the human endometrium carcinoma cell line, RL95-2. We identified a number of positive and negative regulatory sequences as well as the estrogen-response element in the 5'-flanking region of the lactoferrin gene. The imperfect estrogen response elements of both human and mouse are functional as demonstrated by transfection experiments, band-shift assay and DNase I footprint analysis. The molecular mechanism that governs the estrogen-stimulated response, however, differs between human and mouse.