Regulation of Chorionic Gonadotropin Gene Expression*

Abstract

I. Introduction CHORIONIC gonadotropin (CG) is a placental hormone that maintains the corpus luteum of pregnancy. Because CG is expressed at high levels soon after fertilization and implantation, it is used to detect pregnancy at early stages and to monitor the progress of pregnancy during the first trimester (1). CG is also produced in trophoblastic disease and in a variety of different malignancies, and it is useful as a tumor marker in these conditions (2). The mechanisms that control CG production have been investigated extensively, and there are several recent comprehensive reviews (3, 4). CG is a heterodimer composed of α- and β-subunits (Fig. 1). The α-subunit is identical to that in other members of the glycoprotein hormone family (TSH, FSH, LH), whereas the β-subunits in each of the hormones are distinct and confer receptor and biological specificity (5). Little hormone is stored intracellularly and, for the most part, hormone secretion reflects de novo biosynthesis. Therefore, many recent studie...