Hepatic DGAT2 gene expression is regulated by the synergistic action of ChREBP and SP1 in HepG2 cells

Abstract

Diacylglycerol acyltransferase 2 (DGAT2) catalyzes the final step of triglyceride synthesis and plays a critical role in the development of fatty liver disease and insulin resistance. The expression of DGAT2 is mostly induced by dietary carbohydrate in the mammalian liver; however, the transcription factors that regulate DGAT2 expression have yet to be identified. In this study, we investigated the molecular mechanism underlying the glucose-induced transcriptional regulation of human DGAT2 in HepG2 cells. Human DGAT2 expression was increased by glucose in HepG2 cells. Transfection studies of the DGAT2 promoter-luciferase reporter construct in vitro and in silico analysis identified two glucose-responsive regions in the DGAT2 promoter. Each region contains one ChREBP/MLX (carbohydrate response element binding protein/Max-like protein) binding site (ChoRE, −539 to −551 and −6067 to −6083) and one specificity protein 1 (SP1) binding site (GC-rich motif, −556 to −572 and −6016 to −6032). Mutational analysis showed that both ChREBP/MLX and SP1 sites are required for the glucose-induced transcription of DGAT2. Gel shift assays and chromatin immunoprecipitation assays demonstrated that ChREBP and SP1 bind directly to ChoRE and the GC-rich motif, respectively. High glucose promoted the recruitment of ChREBP to ChoRE, whereas SP1 was recruited to the GC-rich motif even under low-glucose conditions. These data demonstrate that both ChREBP and SP1 are key factors to regulate the expression of human DGAT2 by glucose.