The orphan nuclear receptor LRH-1 activates the ABCG5/ABCG8 intergenic promoter.
The ATP binding cassette (ABC) half-transporters ABCG5 and ABCG8 facilitate biliary and intestinal removal of neutral sterols. Here, we identify a binding site for the orphan nuclear receptor liver receptor homolog-1 (LRH-1) at nt 134-142 of the ABCG5/ABCG8 intergenic region necessary for the activity of both the ABCG5 and ABCG8 promoters. Mutating this LRH-1 binding site reduced promoter activity of the human ABCG5/ABCG8 intergenic region more than 7-fold in HepG2 and Caco2 cells. Electrophoretic mobility shift assays with HepG2 nuclear extracts demonstrated specific binding of LRH-1 to the LRH-1 binding motif in the human ABCG5/ABCG8 intergenic region. LRH-1 overexpression increased promoter activity up to 1.6-fold and 3-fold in Caco2 and 293 cells, respectively. Finally, deoxycholic acid repressed the ABCG5 and ABCG8 promoters, consistent with bile acid regulation via the farnesoid X receptor-small heterodimeric partner-LRH-1 pathway. These results demonstrate that LRH-1 is a positive transcription factor for ABCG5 and ABCG8 and, in conjunction with studies on LRH-1 activation of other promoters, identify LRH-1 as a "master regulator" for genes involved in sterol and bile acid secretion from liver and intestine.
Freeman
Lita A
LA
Molecular Disease Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA. litaf@mail.nih.gov
Kennedy
Arion
A
Wu
Justina
J
Bark
Samantha
S
Remaley
Alan T
AT
Santamarina-Fojo
Silvia
S
Brewer
H Bryan
HB
D000071018:ATP Binding Cassette Transporter, Subfamily G, Member 5; D000071019:ATP Binding Cassette Transporter, Subfamily G, Member 8; D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D001647:Bile Acids and Salts / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics / Q000502:physiology; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000502:physiology*; D003840:Deoxycholic Acid / Q000494:pharmacology; D006801:Humans; D008074:Lipoproteins / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics*; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology*; D013261:Sterols / Q000378:metabolism; D014157:Transcription Factors / Q000502:physiology; D015533:Transcriptional Activation
C416945:ABCG5 protein, human; C416946:ABCG8 protein, human; D000071018:ATP Binding Cassette Transporter, Subfamily G, Member 5; D000071019:ATP Binding Cassette Transporter, Subfamily G, Member 8; D018528:ATP-Binding Cassette Transporters; D001647:Bile Acids and Salts; D004268:DNA-Binding Proteins; D008074:Lipoproteins; C082631:NR5A2 protein, human; D018160:Receptors, Cytoplasmic and Nuclear; D013261:Sterols; D014157:Transcription Factors; D003840:Deoxycholic Acid