Cloning and expression of human liver dehydroepiandrosterone sulphotransferase

Abstract

Dehydroepiandrosterone sulphotransferase (DHEA-ST) catalyses the 3'-phosphoadenosine 5'-phosphosulphate-dependent sulphation of a wide variety of steroids in human liver and adrenal tissue and is responsible for most, if not all, of the sulphation of bile acids in human liver. This report describes the isolation, characterization and expression of a cDNA which encodes human liver DHEA-ST. The DHEA-ST cDNA, designated DHEA-ST8, was isolated from a Uni-Zap XR human liver cDNA library and is composed of 1060 bp and contains an open reading frame encoding a 285-amino-acid protein with a molecular mass of approx. 33765 Da. Translation of DHEA-ST8 in vitro generated a protein identical in molecular size with that of DHEA-ST. Expression of DHEA-ST8 in COS-7 cells produces an active DHEA-ST protein which is capable of sulphating DHEA, has the same molecular mass as human liver DHEA-ST and is recognized by rabbit anti-(human liver DHEA-ST) antibodies. Northern-blot analysis of human liver RNA detects the presence of three different size transcripts; however, Southern-blot analysis of human DNA suggests that only one gene may be present in the genome. These results describe the cloning of a human ST which has an important role in the sulphation of steroids and bile acids in human liver and adrenals.