Characterization of a cholesterol response element (CRE) in the promoter of the cholesteryl ester transfer protein gene: functional role of the transcription factors SREBP-1a,-2, and YY1.

Cholesteryl ester transfer protein (CFTP) is expressed in human adipocytes, where it acts to promote selective uptake of HDL CE (Benoist, F., M. McDon nell, P. Lau, R. Milne, and R. McPherson. 1997. J. Biol. Chem. 272:23572-23 577), In contrast to other major sterol-responsive genes such as 3-hydroxy- 3-methylglutaryl coenzyme A reductase CETP expression is up-regulated rathe r than downregulated in response to cholesterol, To define elements involve d in cholesterol-mediated up-regulation of CETP gene expression, deletion d erivatives of the CETP promoter ic ere cloned into a luciferase reporter co nstruct and transfected into the human liposarcoma cell line SW872, culture d in the presence or absence of lipoproteins, A fragment associated with a positive cholesterol response was identified between nucleotides -361 and - 138 (relative to the initiation site of transcription) of the promoter. Thi s region contains a tandem repeat of a sequence known to mediate sterol dep endent regulation of the hamster HMG-CoA. reductase gene. We have putativel y denoted this region, the cholesterol response element (CRE). Using gel mo bility shift assays we demonstrate that both YY1 and SREBP-1 interact with the CRE of CETP, Furthermore, in transient cotransfection experiments, both YY1 and SREBP-1a were found to trans-activate, in a dose-dependent manner, the luciferase activity of constructs harboring the CRE. We also demonstra te that SREBP-2, is able to trans-activate a luciferase construct harboring the CRE although much less effectively as compared to SREBP-1. Finally, fu nctional analysis of the CRE confirms its regulatory role in modulating CET P gene expression through its interaction with YY1 and SREBP-1a.