BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH
Mammary gland development and differentiation is regulated by a number of growth factors and hormones. Milk protein gene expression represents a hallmark of functional mammary epithelial differentiation and is coordinated by the lactogenic hormone prolactin and glucocorticoids. To date, few 'early-response' genes transcriptionally activated by lactogenic hormones have been described. We have used representational difference analysis (RDA) to search for lactogenic-responsive genes in SCp2 mouse mammary epithelial cells. One of the cDNAs identified encoded the DNA-binding protein Taxreb 107, originally identified as a HTLV-1 Tax responsive element binding protein. Increased Taxreb 107 expression was confirmed following prolactin and dexamethasone-induced differentiation of SCp2 and HC I I mammary epithelial cells. Taxreb 107 RNA levels were developmentally regulated in the mouse mammary gland, where levels increased substantially during mid- and late pregnancy and persisted during lactation. Overexpression of an antisense Taxreb 107 cDNA construct or antisense oligonucleotide in HC I I mammary epithelial cells attenuated milk protein gene expression following prolactin and dexamethasone treatment. These findings indicate a role for Taxreb107 as a lactogenic hormone-responsive gene during differentiation of the mammary gland. (C) 2003 Elsevier B.V. All rights reserved.