Genetics
C/EBP-beta binds the CETP gene promoter in liver cells but does not actually drive CETP expression (Atherosclerosis 1999)
Original title: Cholesteryl ester transfer protein gene expression is not specifically regulated by CCAAT/enhancer-binding protein in HepG2-cells
Because CETP is expressed predominantly in liver and intestine, researchers investigated whether the transcription factor family C/EBP regulates CETP gene expression. Using band shift assays with HepG2 cell nuclear extracts, they identified C/EBPbeta as the predominant C/EBP isoform binding to the C/EBP consensus sequence in the CETP gene's 5' upstream region, confirmed by supershift experiments with isoform-specific antibodies and a point mutation (CAAT to CTAT) at this site. However, expressing a CETP promoter-luciferase construct in transiently transfected HepG2 and CaCo-2 cells showed that promoter activity was unaffected by the consensus-sequence mutation or by eliminating this binding site along with a second potential C/EBP site, and co-transfecting HepG2 cells with human C/EBPalpha did not enhance promoter activity or influence synthesis of endogenous CETP. The results indicate that C/EBP binding to the CETP promoter in HepG2 cells does not specifically drive expression of either the transfected reporter or the endogenous CETP gene.
Original abstract
Cholesteryl ester transfer protein (CETP) mediates the exchange of neutral lipids among plasma lipoproteins and is expressed predominantly in liver and intestine. In band shift assays employing nuclear extracts of HepG2 cells we identified C/EBPbeta as the predominant C/EBP isoform involved in binding to the C/EBP consensus sequence within the 5' upstream region of the CETP gene. This was demonstrated by supershift experiments using antibodies specific for C/EBPalpha, C/EBPbeta and C/EBPdelta and an oligonucleotide containing a single point mutation (CAAT-->CTAT) in this site. Expression of a CETP promoter-fragment/luciferase construct in transiently transfected HepG2 and CaCo-2 cells and enhancement of promoter activity by co-transfection with human C/EBPalpha in HepG2 cells could be influenced neither by the mutation in the consensus sequence nor by elimination of this site together with a second potential binding site for C/EBP. Furthermore, transfection of HepG2 with human C/EBPalpha did not influence the synthesis of CETP by these cells. Our results indicate that the expression of C/EBP in HepG2 cells is not able (1) to influence specifically the expression of a transfected CETP promoter dependent reporter through binding to C/EBP sites in the promoter region and (2) to significantly enhance expression of the endogenous CETP gene.
Summary written by cetpinhibition.org from the published abstract; figures as published. Page updated 18 August 2026. Methods.