A Set of Proximal Regulatory Elements Contribute to the Transcriptional Activity of the Human Lipoprotein Lipase Promoter

Abstract

Lipoprotein lipase (LPL) is a multifunctional protein that catalyzes the hydrolysis of plasma triglycerides, releasing free fatty acids, which play critical roles in the metabolism and transport of lipids. The transcription of LPL in response to cell types and regulatory factors is a complex process that starts with its promoter. In previous studies, several proximal regulatory elements within the human LPL promoter were individually characterized. This study was designed to characterize the effect of 12 proximal regulatory elements as a combined unit on the transcriptional activity of the LPL promoter. The hypothesis was that these proximal regulatory elements collectively result in the optimal transcriptional activity of the human LPL promoter. Full and partial LPL promoter sequences, which contained and excluded the 12 regulatory elements, respectively, were cloned and inserted into a promoterless luciferase reporter vector. The functional activities of these constructs were tested in vitro using a dual-luciferase reporter assay. Our results showed that HEK-293 cells transfected with the full LPL promoter exhibited significantly greater luciferase activity than cells transfected with partial LPL promoters. Our results indicate that the proximal regulatory elements within the LPL promoter, including four TATA boxes, two Oct-1 sites, one CT element, two C/EBPα sites, one SP1 site, and two cis-acting regions (LP-α and LP-β), are essential for its transcriptional activity.