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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
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/33066
Page Count: 5
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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.
Proceedings of the National Academy of Sciences of the United States of America © 1989 National Academy of Sciences