Prolactin stimulates milk protein promoter in CHO cells cotransfected with prolactin receptor cDNA.

A functional biological system was developed by cotransfecting mammalian cell lines with the cDNA of the prolactin receptor (PRL-R) and a fusion gene containing the promoter of the milk protein, ovine beta-lactoglobulin linked to the coding sequence of the chloramphenicol acetyltransferase (CAT) gene. Surprisingly, this system is effective even if a non-mammary cell line is used, since Chinese hamster ovary (CHO) cells transfected both transiently and stably with PRL-R cDNA respond to PRL, as observed by stimulation of the reporter gene. This newly developed system should help precisely define the functional domains of both the PRL-R molecule and of the regulatory elements of a PRL target gene.