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Prolactin and Glucocorticoid Hormones Synergistically Induce Expression of Transfected Rat β -casein Gene Promoter Constructs in a Mammary Epithelial Cell Line

Wolfgang Doppler, Bernd Groner and Roland K. Ball
Proceedings of the National Academy of Sciences of the United States of America
Vol. 86, No. 1 (Jan. 1, 1989), pp. 104-108
Stable URL: http://www.jstor.org/stable/33066
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Prolactin and Glucocorticoid Hormones Synergistically Induce Expression of Transfected Rat β -casein Gene Promoter Constructs in a Mammary Epithelial Cell Line
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Abstract

We have detected hormone response elements in the promoter region of the rat β -casein gene that confer the synergistic action of prolactin and glucocorticoid hormones upon transcription of chimeric gene constructs. A 2800-base-pair (bp) rat β -casein gene fragment containing 2300 bp of 5 flanking sequence was placed in front of a chloramphenicol acetyltransferase (CAT) reporter gene and stably transfected into the mouse mammary epithelial cell line HC11. Addition of prolactin or dexamethasone alone was sufficient for a modest induction of the fusion gene. The simultaneous presence of both hormones produced a strongly synergistic effect, which did not require the presence of insulin. Induction of the β -casein-CAT gene was only observed in stably transfected confluent cell cultures. Analysis of a 5 deletion series of the β -casein-CAT gene construct revealed a stepwise loss of hormone inducibility; 285 bp of 5 flanking sequence was sufficient to mediate the synergistic action of lactogenic hormones on expression. The response was reduced by half when compared with the construct containing 2300 bp of the 5 flanking region. Synergistic inducibility further decreased in deletion mutants between -285 and -265 and was completely abolished between -180 and -170. Thus, the 5 flanking region between -285 and -170 contains cis-acting sequences, which are required for mediating the effect of prolactin and dexamethasone.

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