Lactogenic Hormone and Cell Type-Specific Control of the Whey Acidic Protein Gene Promoter in Transfected Mouse Cells

Abstract

The whey acidic protein (WAP) is a major milk protein. It is abundantly expressed in mammary epithelial cells, and its gene is controlled by lactogenic hormones. The identification of regulatory cis-acting sequences of the mouse WAP gene was so far dependent on the analysis of transgenic animals. We report here the possibility of analyzing regulatory sequences by gene transfer experiments using the lactogenic hormone-dependent mammary epithelial cell line HC11. A WAP-chloramphenicol acetyltransferase construct containing 2.5 kilobases of the 5'-flanking sequence of the WAP gene was stably transfected into HC11 cells. High chloramphenicol acetyltransferase activity was induced in pools of transfected cells cultured in the presence of the lactogenic hormones glucocorticoid, PRL, and insulin. A lower induction was observed by glucocorticoid hormone alone. PRL by itself was not able to induce the WAP gene promoter above the level observed in the absence of lactogenic hormones. A time course of hormone induction showed a weak initial response with a steady increase over at least 4 days of hormone treatment. Induction was not observable in the mammary epithelial cell line NOG-8 and NIH3T3 fibroblasts, despite the presence of functional glucocorticoid receptor in these cells. This indicates the requirement for a cell type-specific transcription factor present in the mammary epithelial cell line HC11, but not in NOG-8 epithelial cells or NIH3T3 fibroblasts.(ABSTRACT TRUNCATED AT 250 WORDS)