Hormonal regulation of the bovine prolactin promoter in rat pituitary tumor cells.

A 1-kilobase DNA fragment containing the promoter of the bovine prolactin gene was fused to the chloramphenicol acetyltransferase gene and the activity of the promoter was assayed by transfection of the fusion gene into COS-1, HeLa, and GH3 cells. Transcription of the chloramphenicol acetyltransferase gene driven by the prolactin promoter was detected only in GH3 cells, a rat pituitary tumor cell line. Epidermal growth factor and thyroid releasing hormone produced a stimulation of transcription, and the synthetic glucocorticoid hormone dexamethasone effected an inhibition of transcription from the prolactin promoter. None of these factors significantly affected transcription of the chloramphenicol acetyltransferase gene fused to the Rous sarcoma virus promoter. Deletion of all but 250 base pairs of bovine prolactin 5'-flanking DNA had no effect, indicating that the signals sufficient for both stimulation and inhibition of transcription reside in close proximity to the promoter.