Activation of the Caprine ${\beta}$-Lactoglobulin Gene Promoter by Lactogenic Hormones in Cultured Mammary HC11 Cells

Analysis of the 5'-regulatory sequence of the caprine ${\beta}$-lactoglobulin (BLG) gene promoter revealed that two different types of activation were mediated by discrete regions, from -740 to -470 and from -205 to 109, in cultured mammary HC11 cells. Activation mediated by the proximal region was observed regardless of cell growth status. Distal activation, however, was observed only after confluent growth of the cells and was enhanced by the lactogenic hormones. This activation was accompanied by appearance of binding activity of proteins to these regions in the mammary HC11 cells. The binding motifs were broadly distributed over the upstream regulatory sequence. Comparison of the binding regions and mutation analysis suggest that a binding motif homologous to the ${\gamma}$-interferon responsive element (${\gamma}$-IRE) is responsible for transcriptional activation by hormonal induction in the mammary HC11 cells. The multiple ${\gamma}$-IRE homologous motifs seem to play a significant role in enhancing mammary cell-specific activation of the caprine BLG gene.