Effects of adenine nucleotides on choriogonadotropin α and β subunit synthesis

The α subunit of human chorionic gonadotropin (CG) contains a discrete cAMP response element in the 5′ flanking region of the gene. Since cAMP also stimulates the synthesis of the CGβ subunit the presence of a cAMP cis element in the CGβ gene was examined. Deletion mutants bearing various lengths of CGβ 5′ region in front of the chloramphenicol acetyl transferase (CAT) gene were transfected in placental tumor cells. No discrete cAMP response element could be identified. Unexpectedly we also observed that AMP and adenosine not only stimulated CAT activity driven by CGβ promoter sequences but also enhanced synthesis of CGα and β subunits in cultured choriocarcinoma cells. GMP, CMP, guanosine, and cytosine were inactive at comparable concentrations. These data suggest that the response of the CGα and β genes to the non-cyclic adenine derivatives occurs by a mechanism that differs from cAMP.