期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1990
卷号：87
期号：23
页码：9118-9122
DOI：10.1073/pnas.87.23.9118
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Milk protein regulation involves synergistic action of lactogenic hormones and extracellular matrix (ECM). It is well established that substratum has a dramatic effect on morphology and function of mammary cells. The molecular mechanisms that regulate the ECM- and hormone-dependent gene expression, however, have not been resolved. To address this question, a subpopulation (designated CID 9) of the mouse mammary epithelial cell strain COMMA-1D has been developed in which more than 35% of the cells express beta-casein, form alveoli-like structures when plated onto a reconstituted basement membrane, and secrete beta-casein unidirectionally into a lumen. These cells were stably transfected with a series of chloramphenicol acetyltransferase (CAT) fusion genes to study transcriptional regulation of the bovine beta-casein gene. The expression of CAT in these lines demonstrated a striking matrix and hormone dependency (greater than 150-fold induction in some cases). This regulation occurred primarily at the transcriptional level and was dependent on the length of the 5' flanking region of the beta-casein promotor. Both matrix and hormonal control of transcription occurred within at least the first 1790 base pairs upstream and/or 42 base pairs downstream of the transcriptional initiation site. The ECM effect was independent of glucocorticoid stimulation. However, prolactin was essential and hydrocortisone further increased CAT expression. Endogenous beta-casein expression in these lines was similar to that of the parent CID 9 cells. Our data indicate the existence of matrix-dependent elements that regulate transcription.
