Positive and negative regulation of human hepatic hydroxysteroid sulfotransferase (SULT2A1) gene transcription by rifampicin: roles of hepatocyte nuclear factor 4alpha and pregnane X receptor.
The effects of rifampicin treatment on SULT2A1 mRNA expression were evaluated in 23 preparations of primary cultured human hepatocytes. In contrast to the consistently occurring induction of CYP3A4, a prototypical pregnane X receptor (PXR) target gene, rifampicin treatment increased SULT2A1 mRNA levels in 12 of the hepatocyte preparations, but it produced little change or even suppression in the others. Transient transfection of HepG2 cells with a series of reporter constructs implicated two SULT2A1 5'-flanking regions as containing rifampicin-responsive information. Each of these regions contained a hepatocyte nuclear factor 4 (HNF4) binding site (at nucleotide [nt] -6160 and -54), as demonstrated by in vitro binding and site-directed mutagenesis. HNF4alpha bound to the HNF4-54 region of the endogenous SULT2A1 gene, as indicated by chromatin immunoprecipitation. Cotransfection of HepG2 cells with pregnane X receptor (PXR) dose-dependently suppressed reporter expression from SULT2A1 constructs containing the HNF4 sites, and rifampicin treatment augmented the suppression. Rifampicin treatment concentration-dependently suppressed SULT2A1 reporter expression at the same concentrations that progressively induced expression from a PXR-responsive CYP3A4 reporter, whereas higher rifampicin concentrations reversed the SULT2A1 suppression. The suppressive effect of rifampicin was diminished, whereas the activating effect was augmented, in HepG2 cells with RNA interference-mediated PXR knockdown. These results suggest that HNF4alpha plays a central role in the control of SULT2A1 transcription and that rifampicin-liganded PXR suppresses SULT2A1 expression by interfering with HNF4alpha activity. By contrast, the rifampicin-inducible SULT2A1 expression that occurs in many human hepatocyte preparations seems to be mediated through a PXR-independent mechanism.
Institute of Environmental Health Sciences, Wayne State University, Detroit, Michigan 48201, USA.
Hai-Lin
HL
Fang
Stephen C
SC
Strom
Ewa
E
Ellis
Zhengbo
Z
Duanmu
Jiaqi
J
Fu
Zofia
Z
Duniec-Dmuchowski
Charles N
CN
Falany
Josie L
JL
Falany
Thomas A
TA
Kocarek
Melissa
M
Runge-Morris
D022762:CCAAT-Enhancer-Binding Proteins / Q000502:physiology; D002478:Cells, Cultured; D002790:Cholesterol 7-alpha-Hydroxylase / Q000235:genetics; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D051557:Hepatocyte Nuclear Factor 4 / Q000502:physiology*; D022781:Hepatocytes / Q000201:enzymology*; D006801:Humans; D000077297:Pregnane X Receptor; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D011987:Receptors, Steroid / Q000502:physiology*; D012293:Rifampin / Q000494:pharmacology*; D015238:Sulfotransferases / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects*
D022762:CCAAT-Enhancer-Binding Proteins; C496592:HNF4A protein, human; D051557:Hepatocyte Nuclear Factor 4; D000077297:Pregnane X Receptor; D012333:RNA, Messenger; D011987:Receptors, Steroid; D003577:Cytochrome P-450 Enzyme System; D051544:Cytochrome P-450 CYP3A; D002790:Cholesterol 7-alpha-Hydroxylase; C510163:CYP3A4 protein, human; D015238:Sulfotransferases; C028152:alcohol sulfotransferase; D012293:Rifampin