Pretreatment with glucocorticoid is essential for lactogenic induction of the bovine beta-casein/CAT expression in HC11 cells.
Hormonal regulation of the bovine beta-casein gene expression was studied in a murine mammary epithelial HC11 cells and compared with that of the rat beta-casein gene expression. CAT expression vectors driven by their promoter sequences were transfected into HC11 cells. Stable transfectents were treated with lactogenic hormones, dexamethasone and prolactin for 2 days in confluent cultures. While the lactogenic hormones synergistically induced a strong activation of the rat beta-casein/CAT expression, neither a single or combined treatment of dexamethasone and prolactin induced the bovine beta-casein/CAT expression. To test a sequential treatment effect of lactogenic hormones on the bovine beta-casein/CAT expression, cells were first treated with either dexamethasone or prolactin for various days and then subjected to the second treatment with both hormones for 2 days. Only dexamethasone-, but not prolactin-pretreated cells showed a strong lactogenic induction. Moreover, the fold induction of dexamethasone-pretreated cells increased gradually as a function of duration of dexamethasone pretreatment. A series of the bovine beta-casein/CAT constructs with different length of the bovine beta-casein 5' flanking region ranged from 0.3 kb to about 15 kb was analyzed in 12-days dexamethasone-pretreated cultures. CAT expression was increased even in 0.3 kb-containing construct, but prominent induction was seen in more than 1.8 kb-containing constructs. Therefore, it could be concluded that a long-term dexamethasone pretreatment is essential for lactogenic induction of the bovine beta-casein expression and the 0.3 kb proximal promoter region is important, but more distal promoter element(s) is necessary for mediating the coordinated action of lactogenic hormones to the bovine beta-casein expression.
Lee
C S
CS
Korea Research Institute of Bioscience and Biotechnology, KIST, Taejon, Korea.
Kim
K
K
Yu
D Y
DY
Lee
K K
KK
D000818:Animals; D019677:Artificial Gene Fusion; D002364:Caseins / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics*; D002417:Cattle; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis / Q000235:genetics; D003907:Dexamethasone / Q000494:pharmacology*; D004847:Epithelial Cells / Q000166:cytology; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000235:genetics*; D005938:Glucocorticoids / Q000494:pharmacology*; D008321:Mammary Glands, Animal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D011388:Prolactin / Q000494:pharmacology*; D051381:Rats; D012045:Regulatory Sequences, Nucleic Acid / Q000187:drug effects / Q000235:genetics*; D013268:Stimulation, Chemical; D013997:Time Factors; D014162:Transfection
D002364:Caseins; D005938:Glucocorticoids; D003907:Dexamethasone; D011388:Prolactin; D015500:Chloramphenicol O-Acetyltransferase