Relative contribution of promoter and intragenic sequences in the hormonal regulation of rat beta-casein transgenes.
In order to identify DNA sequences responsible for the regulation beta-casein gene expression, lines of transgenic mice bearing the entire rat beta-casein gene and two rat beta-casein promoter chloramphenicol acetyltransferase (CAT) fusion genes have been established. All three transgenes have been shown previously to be regulated in a tissue- and stage specific manner. To investigate the relative contribution of promoter and intragenic sequences in the hormonal regulation of the beta-casein gene, mammary explant cultures derived from these lines of mice have now been performed, and the effects of PRL and glucocorticoids on transgene as compared with endogenous beta-casein gene expression have been quantified. After the addition of PRL to cultures performed in the presence of insulin and glucocorticoids, a 25- to 40-fold induction of endogenous mouse beta-casein mRNA was observed after 48 hr. A comparable greater than 25-fold induction of transgene expression after PRL addition was observed in explant cultures derived from a line of mice expressing the entire rat beta-casein gene. In contrast, PRL addition elicited only a 1- to 4.5-fold increase in CAT activity in cultures derived from two lines of mice bearing casein-CAT fusion genes with either 524 or 2300 base pairs of 5'-flanking DNA. In the presence of insulin, glucocorticoid or PRL addition alone increased endogenous beta-casein gene expression 2- to 2.5-fold and 5- to 10-fold, respectively, but only a 1.2- to 2.5-fold induction of CAT activity was observed for each hormone.(ABSTRACT TRUNCATED AT 250 WORDS)
Lee
K F
KF
Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030.
Atiee
S H
SH
Henning
S J
SJ
Rosen
J M
JM
D000818:Animals; D002364:Caseins / Q000235:genetics*; D003001:Cloning, Molecular; D005786:Gene Expression Regulation; D051379:Mice; D008822:Mice, Transgenic; D011388:Prolactin / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D051381:Rats; D014158:Transcription, Genetic / Q000187:drug effects
D002364:Caseins; D011388:Prolactin