Nuclear proteins form lactating mammary glands bind to the promoter of a milk protein gene

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Abstract
The gene for the whey acidic protein (WAP) is expressed specifically in the lactatlng mammary glands of rodents. We present evidence that nuclear proteins from mammary epithelial cells form a multiple nucleoproteln complex with the WAP gene promoterSol;upstream region. As monitored by mobility shifts, nuclear proteins from lactatlng mammary glands and from the mammary cell line MCF-7 form four high affinity complexes with a fragment spanning the region between nucleotldes -175 and -88. Suclear proteins from liver and HeLa cells generate only three high affinity complexes. DNAasel and Exonucleaselll protection confirmed the binding of mammary nuclear proteins to specific sequences in the WAP gene upstream region. This is the first report to describe the interaction of nuclear proteins from lactating mammary glands with cognate binding sites in the promoter/upstream region of a milk protein gene. The possibility of the binding sites being candidates for cls-acting regulatory elements governing the regulated expression of the WAP gene is discussed