Identification of essential subelements in the hHSD17B1 enhancer: difference in function of the enhancer and that of the hHSD17BP1 analog is due to -480C and -486G

Role of hydroxysteroid (17beta) dehydrogenase type 1 in reproductive tissues and hormone-dependent diseases

Abnormal synthesis and metabolism of sex steroids is involved in the pathogenesis of various human diseases, such as endometriosis and cancers arising from the breast and uterus. Steroid biosynthesis is a multistep enzymatic process proceeding from cholesterol to highly active sex steroids via different intermediates. Human Hydroxysteroid (17beta) dehydrogenase 1 (HSD17B1) enzyme shows a high capacity to produce the highly active estrogen, estradiol, from a precursor hormone, estrone. However, the enzyme may also play a role in other steps of the steroid biosynthesis pathway. In this article, we have reviewed the literature on HSD17B1, and summarize the role of the enzyme in hormone-dependent diseases in women as evidenced by preclinical studies.

Decreased Transcription Factor Binding Levels Nearby Primate Pseudogenes Suggest Regulatory Degeneration

Characteristics of pseudogene degeneration at the coding level are well-known, such as a shift toward neutral rates of nonsynonymous substitutions and gain of frameshift mutations. In contrast, degeneration of pseudogene transcriptional regulation is not well understood. Here, we test two predictions of regulatory degeneration along a pseudogenized lineage: 1) Decreased transcription factor (TF) binding and 2) accelerated evolution in putative cis-regulatory regions.We find evidence for decreased TF binding levels nearby two primate pseudogenes compared with functional liver genes. However, the majority of TF-bound sequences nearby pseudogenes do not show evidence for lineage-specific accelerated rates of evolution. We conclude that decreases in TF binding level could be a marker for regulatory degeneration, while sequence degeneration in primate cis-regulatory modules may be obscured by background rates of TF binding site turnover.

Estrogen metabolism as a regulator of estrogen action in the mammary gland

Estrogen action in the target cells is dependent on estrogen receptor activity and intracellular estrogen concentration, which, in turn, is affected by the serum concentration and local metabolism in these cells. During the reproductive years the main source of estrogens is the ovarian follicles, but in postmenopausal women most of the estrogens are formed in peripheral tissues. 17Beta-hydroxysteroid dehydrogenases (17HSDs) catalyze the reaction between 17beta-hydroxysteroids and 17-ketosteroids, and several distinct 17HSD isoenzymes have been characterized. 17HSD type 1 catalyzes the reaction from low-activity estrone to high-activity estradiol. The type 2 enzyme has an opposite activity, thereby reducing the exposure of tissues to estrogen action. 17HSD type 1 is expressed both in steroidogenic tissues and in the target tissues of steroid action, such as normal and malignant breast tissue, where it may be responsible for maintaining the high intracellular estradiol concentration seen in breast cancer specimens. Therefore, 17HSD type 1 inhibitors may be useful in the treatment and/or prevention of estrogen-dependent malignancies, such as breast cancer. This article deals mainly with 17HSD types 1 and 2 and their role in estrogen action in breast tissue.