Identification of retinoic acid receptor element in human cholesteryl ester transfer protein gene

The transcriptional regulation of the human cholesteryl ester transfer protein (CETP) gene by retinoic acid was investigated by a transient transfection assay. A series of deleted vectors generated from the 5'-upstream region (3434 bp) of the CETP gene linked to the luciferase reporter gene was individually transfected to HepG2 cells. Promoter analyses revealed essential regulatory machinery in the -110/-40 region of the upstream sequence of the human CETP gene. When the cells transfected with the reporter vectors were stimulated with all-trans retinoic acid (tRA), the hormone response was drastically reduced when the -165/-110 region was deleted, thereby suggesting that there may be a retinoic acid receptor element (RARE) in the region. A footprinting analysis showed that the DNA segment at the -165/-134 is protected by the HepG2 nuclear extract. A competition analysis on the gel mobility shift assay using consensus RARE and a purified retinoic acid receptor confirmed the -165/-134 region as being RARE.