A distal region enhances the prolactin induced promoter activity of the rabbit αs1-casein gene

Casein gene expression is induced in the rabbit mammary gland by prolactin (PRL). αs1-casein is the major casein secreted into milk. In order to define the position of the DNA sequences involved in the control of rabbit αs1-casein gene regulation by PRL, chimeric genes were constructed between upstream regions of the rabbit αs1-casein gene and the chloramphenicol acetyl transferase (CAT) reporter gene. A series of 5'-deleted fusion genes was obtained by nuclease digestion of the αs1-casein gene upstream region. These gene constructs were transfected into rabbit primary mammary cells, or cotransfected in CHO cells with the plasmid coding for the rabbit mammary receptor (PRL-R). A regulatory region has been located between nt −3768 and −3155. This region enhances the prolactin induced promoter activity of the αs1-casein gene. It might possess or cooperate with prolactin responsive elements located further downstream in the αs1-casein gene.