SREBP-1 Interacts with Hepatocyte Nuclear Factor-4α and Interferes with PGC-1 Recruitment to Suppress Hepatic Gluconeogenic Genes

• Published in: The Journal of biological chemistry 2004-03, Vol.279 (13), p.12027-12035
• Main Authors: Yamamoto, Takashi, Shimano, Hitoshi, Nakagawa, Yoshimi, Ide, Tomohiro, Yahagi, Naoya, Matsuzaka, Takashi, Nakakuki, Masanori, Takahashi, Akimitsu, Suzuki, Hiroaki, Sone, Hirohito, Toyoshima, Hideo, Sato, Ryuichiro, Yamada, Nobuhiro
• Format: Article
• Language: English
• Subjects: Animals; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Binding Sites; Binding, Competitive; Blotting, Northern; CCAAT-Enhancer-Binding Proteins - metabolism; Cell Line; Colforsin - pharmacology; DNA-Binding Proteins - metabolism; Dose-Response Relationship, Drug; Gene Expression Regulation; Glutathione Transferase - metabolism; Hepatocyte Nuclear Factor 4; Humans; Ligands; Lipoproteins, LDL - metabolism; Liver - metabolism; Luciferases - metabolism; Mice; Mice, Transgenic; Models, Genetic; Phosphoenolpyruvate Carboxykinase (GTP) - biosynthesis; Phosphoproteins - metabolism; Plasmids - metabolism; Precipitin Tests; Promoter Regions, Genetic; Protein Binding; Protein Isoforms; Protein Structure, Tertiary; Recombinant Fusion Proteins - metabolism; RNA - metabolism; Sterol Regulatory Element Binding Protein 1; Sterol Regulatory Element Binding Protein 2; Transcription Factors - metabolism; Transcription, Genetic; Transcriptional Activation; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M310333200

The hepatocyte nuclear factor-4α (HNF-4α)/PGC-1 pathway plays a crucial role in the transcriptional regulation of hepatic gluconeogenic enzymes such as phosphoenolpyruvate carboxykinase (PEPCK) and Glc-6-Pase, genes that are activated at fasting and suppressed in a fed state. SREBP-1c dominates the nutritional regulation of lipogenic genes inverse to gluconeogenesis. Here we show the mechanism by which SREBP-1 suppresses expression of gluconeogenic genes. A series of luciferase reporter assays demonstrated that SREBP-1a and -1c effectively inhibited the PEPCK promoter activity that was induced by HNF-4α. The HNF-4α-binding site in the glucocorticoid-response unit was responsible for the SREBP-1 inhibition, although SREBP-1 did not bind to the PEPCK promoter as demonstrated by electrophoretic mobility shift assays. The inhibitory effect was more potent in the isoform of SREBP-1a than SREBP-1c and was eliminated by deletion of the amino-terminal transactivation domain of SREBP-1. Coimmunoprecipitation experiments demonstrated that these two transcription factors directly interact through the transactivation domain of SREBP-1 and the ligand binding/AF2 domains of HNF-4α. Estimation of coactivator recruitment using HNF-4α-Gal4DBD fusion assay showed that SREBP-1 competitively inhibited PGC-1 recruitment, a requirement for HNF-4α activation. Consistent with these results, hepatic PEPCK and Glc-6-Pase mRNA levels are suppressed by overexpression of SREBP-1a and -1c in the transgenic mice. Our data indicate that SREBP-1 has a novel role as negative regulator of gluconeogenic genes through a cross-talk with HNF-4α interference with PGC-1 recruitment.