Abstract
Human placental lactogen (hPL) and human growth hormone (hGH) are members of a multigene family that share amino acid sequence homology and similarity in gene structure and nucleotide sequence, but differ in both function and expression. To determine the sequence requirements for tissue specific expression recombinant plasmids containing the members of the hPL-hGH multigene family and flanking regions were analyzed by both transient and stable transfection assays. We have identified a transcriptional enhancer in a 1.0 kb region located 2.0 kb downstream of the hPL3 structural gene. This enhancer sequence is not strictly cell-type specific since it functions in cell lines of both placental (JEG-3) and pituitary (18-54,SF) origin. However, its efficiency is several fold higher in placental cells than in pituitary cells.