Regulation of human CETP gene expression: role of SP1 and SP3 transcription factors at promoter sites -690, -629, and -37.
Cholesteryl ester transfer protein (CETP) is a key factor in plasma reverse cholesterol transport and is implicated in the pathophysiology of atherogenic dyslipidemia. Variations observed in plasma CETP mass and activity in both normolipidemic and dyslipidemic individuals may reflect differences in CETP gene expression. We evaluated the respective roles of the Sp1 and Sp3 transcription factors on the promoter activity of the human CETP gene at a new Sp1/Sp3 site identified at position -690, and at two previously described Sp1/Sp3 sites at positions -37 and -629. In transient transfection in HepG2 cells, site-directed mutagenesis using luciferase reporter constructs containing a promoter fragment from +32 to -745 indicated that the new -690 site acts as a repressive element in reducing CETP promoter activity (-22%; P < 0.05); equally, this site exerts an additive effect with the -629 site, inducing marked repression (-42%; P < 0.005). In contrast, in NCTC cells that display a 16-fold lower level of Sp3, the repressive effect at the -690 site was enhanced 2-fold (-45%; P < 0.05), whereas the -629 site exerted no effect. Cotransfection of Sp1 and/or Sp3 in SL2 insect cells lacking endogenous Sp factors demonstrated that Sp1 and Sp3 act as activators at the -690 and -37 sites, whereas Sp3 acts as a repressor at the -629 site. Taken together, our data demonstrate that Sp1 and Sp3 regulate human CETP promoter activity through three Sp1/Sp3 binding sites in a distinct manner, and that the Sp1/Sp3 ratio is a key factor in determining the relative contribution of these sites to total promoter activity.
Le Goff
Wilfried
W
Institut National de la Santé et de la Recherche Médicale (INSERM) Unité 551 "Dyslipoproteinemias and Atherosclerosis: Genetics, Metabolism and Therapy" , Hôpital de la Pitié, 83 boulevard de l'Hôpital, 75651 Paris, France.
Guerin
Maryse
M
Petit
Laure
L
Chapman
M John
MJ
Thillet
Joëlle
J
D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics*; D002460:Cell Line; D053480:Cholesterol Ester Transfer Proteins; D004268:DNA-Binding Proteins / Q000235:genetics*; D003850:Deoxyribonuclease I / Q000378:metabolism; D003851:Deoxyribonucleases / Q000378:metabolism; D005786:Gene Expression Regulation; D006023:Glycoproteins; D006801:Humans; D007313:Insecta; D008156:Luciferases / Q000378:metabolism; D008957:Models, Genetic; D016297:Mutagenesis, Site-Directed; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D016329:Sp1 Transcription Factor / Q000235:genetics*; D051705:Sp3 Transcription Factor; D014157:Transcription Factors / Q000235:genetics*; D014162:Transfection
C506642:CETP protein, human; D002352:Carrier Proteins; D053480:Cholesterol Ester Transfer Proteins; D004268:DNA-Binding Proteins; D006023:Glycoproteins; C497121:SP3 protein, human; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; D051705:Sp3 Transcription Factor; D008156:Luciferases; D003851:Deoxyribonucleases; D003850:Deoxyribonuclease I