Polyunsaturated Fatty Acids (PUFA) Regulate Hepatic Nuclear Factor‐4 (HNF4) Binding to the Rat Hepatic L‐Pyruvate Kinase (LPK) Promoter.

Abstract

Transcription of hepatic LPK is induced by glucose and insulin and repressed by dietary n-3 PUFA. The cis-regulatory region, −197 to −124 bp upstream from the LPK gene is targeted by glucose and PUFA. This region binds HNF4 and the carbohydrate regulatory element binding protein (ChREBP) - Max-like factor X (MLX) heterodimer. In vivo and rat hepatocyte studies show that PUFA suppress hepatic MLX nuclear content, with little effect on HNF4 or ChREBP nuclear abundance. Over expressed MLX attenuates PUFA suppression of LPK promoter activity in rat hepatocytes. Chromatin immunoprecipitation (CHIP) assays revealed that PUFA induced a rapid, but transient inhibition of HNF4 interaction with the LPK promoter. This response correlated with attenuated glucose-stimulated acetylated histone H4 and RNA polymerase II (RNA Pol II) interaction with the LPK promoter. PUFA did not affect HNF4 interaction with other HNF4-regulated promoters, e.g., phosphoenolpyruvate carboxykinase. In conclusion, glucose and PUFA regulate LPK promoter composition and gene transcription. PUFA inhibition of RNA Pol II, acetylated H4 and HNF4 interaction with the LPK promoter represent key steps in the PUFA suppression of LPK gene transcription. Supported by NIH DK43220, USDA 2003-5200-3400 and MAES.