Two 17 beta-hydroxysteroid dehydrogenases (17HSDs) of estradiol biosynthesis: 17HSD type 1 and type 7

Two 17 beta-hydroxysteroid dehydrogenases (17HSDs), type 1 and type 7, are enzymes of estradiol biosynthesis, in addition to which rodent type 1 enzym es are also able to catalyze androgens. Both of the 17HSDs are abundantly e xpressed in ovaries, the type 1 enzyme in granulosa cells and type 7 in lut einized cells. The expression of 17HSD7, which has also been described as a prolactin receptor-associated protein (PRAP), is particularly up-regulated in corpus luteum during the second half of rodent pregnancy. A moderate or slight signal for mouse 17HSD7/PRAP mRNA has also been demonstrated in sam ples of placenta and mammary gland, for example. Human, but not rodent, 17H SD1 is expressed in placenta, breast epithelium and endometrium in addition to ovaries. A cell-specific enhancer, silencer and promoter in the hHSD17B 1 gene participate in the regulation of type 1 enzyme expression. The enhan cer consists of several subunits, including a retinoic acid response elemen t, the silencer has a binding motif for GATA factors, and the proximal prom oter contains adjacent and competing AP-2 and Sp binding sites. (C) 1999 El sevier Science Ltd. All rights reserved.