Hepatocyte Nuclear Factor 4 Is a Transcription Factor that Constitutively Binds Fatty Acids

• Published in: Structure (London) Vol. 10; no. 9; pp. 1225 - 1234
• Main Authors: Wisely, G.Bruce, Miller, Ann B., Davis, Roderick G., Thornquest, Alan D., Johnson, Robert, Spitzer, Tim, Sefler, Andrea, Shearer, Barry, Moore, John T., Miller, Aaron B., Willson, Timothy M., Williams, Shawn P.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-09-2002
• Subjects: Amino Acid Sequence; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Cell Line; Crystallography, X-Ray; diabetes; DNA-Binding Proteins; fatty acids; Fatty Acids - metabolism; Gas Chromatography-Mass Spectrometry; Hepatocyte Nuclear Factor 4; HNF4; Humans; Magnetic Resonance Spectroscopy; Models, Molecular; MODY; Molecular Sequence Data; nuclear receptor; Phosphoproteins - chemistry; Phosphoproteins - metabolism; Protein Binding; Protein Conformation; Protein Isoforms - chemistry; Sequence Homology, Amino Acid; Structure-Activity Relationship; transcription factor; Transcription Factors - chemistry; Transcription Factors - metabolism; Transcription, Genetic; transcription factor; nuclear receptor; MODY; fatty acids; HNF4; diabetes
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/S0969-2126(02)00829-8

The 2.7 Å X-ray crystal structure of the HNF4γ ligand binding domain (LBD) revealed the presence of a fatty acid within the pocket, with the AF2 helix in a conformation characteristic of a transcriptionally active nuclear receptor. GC/MS and NMR analysis of chloroform/methanol extracts from purified HNF4α and HNF4γ LBDs identified mixtures of saturated and
cis-monounsaturated C14-18 fatty acids. The purified HNF4 LBDs interacted with nuclear receptor coactivators, and both HNF4 subtypes show high constitutive activity in transient transfection assays, which was reduced by mutations designed to interfere with fatty acid binding. The endogenous fatty acids did not readily exchange with radiolabeled palmitic acid, and all attempts to displace them without denaturing the protein failed. Our results suggest that the HNF4s may be transcription factors that are constitutively bound to fatty acids.