Location: Children's Nutrition Research CenterTitle: Lactogenic hormonal induction of long distance interactions between beta-casein gene regulatory elements Author
Submitted to: Journal of Biological Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2009
Publication Date: 8/21/2009
Citation: Kabotyanski, E.B., Rijnkels, M., Freeman-Zadrowski, C., Buser, A.C., Edwards, D.P., Rosen, J.M. 2009. Lactogenic hormonal induction of long distance interactions between beta-casein gene regulatory elements. Journal of Biological Chemistry. 281:22815-22824. Interpretive Summary: The way DNA is packaged in the space of the cell’s nucleus is important for gene expression regulation and tissue maturation. The hormones associated with lactation regulate the milk protein beta-casein. We investigated the effect of different hormones on the interaction of two different regions in the DNA that are important for beta-casein expression. We show that the lactogenic hormones induce the interaction of these two regions, and that this interaction is present in mammary gland tissue of lactating animals, but not in non-lactating virgin animals. These results indicate that hormones play a role in the regulation of milk protein expression in part through their organization of the DNA in the nucleus. DNA packaging in the nucleus and gene expression are important for mammary gland maturation.
Technical Abstract: Lactogenic hormone regulation of beta-casein gene expression in mammary epithelial cells provides, an excellent model in which to study the mechanisms by which steroid and peptide hormone signaling control gene expression. Prolactin- and glucocorticoid-mediated induction of beta-casein gene expression involves two principal regulatory regions, a proximal promoter, and a distal enhancer located in the mouse approximately -6 kb upstream of the transcription start site. Using a chromosome conformation capture assay and quantitative real time PCR, we demonstrated that a chromatin loop is created in conjunction with the recruitment of specific transcription factors and p300 in HC11 mammary epithelial cells. Stimulation with both prolactin and hydrocortisone is required for the induction of these long range interactions between the promoter and enhancer, and no DNA looping was observed in nontreated cells or cells treated with each of the hormones separately. The lactogenic hormone-induced interaction between the proximal promoter, and distal enhancer was confirmed in hormone-treated primary three-dimensional mammary acini cultures. In addition, the developmental regulation of DNA looping between the beta-casein regulatory regions was observed in lactating, but not in virgin mouse mammary glands. Furthermore, beta-casein mRNA induction and long range interactions between these regulatory regions were inhibited in a progestin-dependent manner following stimulation with prolactin and hydrocortisone in HC11 cells expressing human PR-B. Collectively, these data suggest that the communication between these regulatory regions with intervening DNA looping is a crucial step required to both create and maintain active chromatin domains and regulate transcription.