Rat prolactin-like protein A partial gene and promoter structure: promoter activity in placental and pituitary cells.

Rat prolactin-like protein A (rPLP-A) is a member of a rapidly expanding family of prolactin-related proteins that are expressed during pregnancy by the rat placenta according to specific developmental patterns. Although the factors involved in the pituitary-specific expression of the prolactin and growth hormone genes themselves have been extensively studied, essentially nothing is known of the factors responsible for the placental expression of these new family members. In this paper we describe the isolation of rPLP-A genomic clones, analyze a portion of the 5' flanking sequence of this gene and use the recently described rat choriocarcinoma cell line, Rcho, in transient transfection studies to show that a 975 base-pair (bp) fragment of 5' flanking sequence is sufficient to specify placental expression of the rPLP-A gene.