Estrogen activates the high-density lipoprotein receptor gene via binding to estrogen response elements and interaction with sterol regulatory element binding protein-1A.
The effects of E2 on the high-density lipoprotein receptor (HDL-R) scavenger receptor class B type I (SR-BI) gene were examined. Four putative estrogen response element half-site motifs (ERE(1/2)) (-2176, -1726, -1622, and -1211, designated ERE(1/2)-1, 2, 3, and 4, respectively) were identified in the HDL-R SR-BI promoter. Transfection studies and mutation analysis demonstrated that E2 significantly increased HDL-R SR-BI promoter activity and that mutating ERE(1/2)-1, 2, and 4 resulted in a loss of E2 responsiveness. Both ER alpha and ER beta formed specific complexes with ERE(1/2)-1, 2, and 4 but did not bind ERE(1/2)-3 in vitro. Interestingly, ERE(1/2)-3 was the motif shown not to be important for E2-activation of the HDL-R SR-BI promoter in the mutational analysis studies. The influence of SREBP-1a (sterol regulatory element binding protein-1a) on E2 regulation of the HDL-R SR-BI gene was also examined. SREBP-1a was able to bind directly to the ERE(1/2) motifs and enhanced ER binding when both ER subtypes were present. ER alpha and beta also bound to a sterol response element motif, but they did not enhance SREBP-1a binding. Cotransfection studies demonstrated that the presence of the three factors, ER alpha, ER beta, and SREBP-1a, enhanced the overall luciferase activity produced from the HDL-R SR-BI promoter construct in the presence of only one of the factors. Interaction of SREBP-1a with both ERs was demonstrated using a mammalian two-hybrid assay. The data confirmed that E2 through the ERs can positively regulate the HDL-R SR-BI through binding and activation of three ERE(1/2) motifs and identified SREBP-1a as a potential coactivator of the E2-ER-dependent effects on the HDL-R SR-BI gene.
Lopez
Dayami
D
Department of Obstetrics & Gynecology, College of Medicine, University of South Florida, Tampa, Florida 33606, USA.
Sanchez
Mark D
MD
Shea-Eaton
Wendy
W
McLean
Mark P
MP
D015153:Blotting, Western; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics*; D018955:CD36 Antigens / Q000235:genetics*; D002352:Carrier Proteins; D002460:Cell Line; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics*; D004586:Electrophoresis; D004958:Estradiol / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D017403:In Situ Hybridization; D008075:Lipoproteins, HDL; D008156:Luciferases; D008565:Membrane Proteins; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic / Q000235:genetics; D016601:RNA-Binding Proteins; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein / Q000235:genetics*; D051116:Receptors, Scavenger; D051122:Scavenger Receptors, Class B; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors; D014162:Transfection
D022762:CCAAT-Enhancer-Binding Proteins; D018955:CD36 Antigens; D002352:Carrier Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D008075:Lipoproteins, HDL; D008565:Membrane Proteins; D016601:RNA-Binding Proteins; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C495124:SCARB1 protein, human; C497387:SREBF1 protein, human; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors; C031616:high density lipoprotein receptors; C075197:high density lipoprotein binding protein; D004958:Estradiol; D008156:Luciferases