Extracellular matrix and hormones transcriptionally regulate bovine beta-casein 5' sequences in stably transfected mouse mammary cells.
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.
Schmidhauser
C
C
Cell and Molecular Biology Division, Lawrence Berkeley Laboratory, University of California, Berkeley 94720.
Bissell
M J
MJ
Myers
C A
CA
Casperson
G F
GF
D000818:Animals; D002364:Caseins / Q000096:biosynthesis / Q000235:genetics*; D002417:Cattle; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis / Q000235:genetics; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D005109:Extracellular Matrix / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects; D015723:Gene Library; D051379:Mice; D016133:Polymerase Chain Reaction; D011388:Prolactin / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D015183:Restriction Mapping; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection
D002364:Caseins; D011993:Recombinant Fusion Proteins; D011388:Prolactin; D004247:DNA; D015500:Chloramphenicol O-Acetyltransferase