HNF4α is required for Tkfc promoter activation by ChREBP

Area of Science:

• Metabolic regulation
• Gene expression
• Molecular biology

Background:

• Triokinase/FMN cyclase (Tkfc) is crucial for fructose metabolism, phosphorylating glyceraldehyde.
• Hepatic Tkfc expression is induced by refeeding in mice.
• Understanding Tkfc regulation is key to comprehending fructose metabolism.

Purpose of the Study:

• To investigate the transcriptional regulation of the Tkfc gene.
• To identify the roles of hepatocyte nuclear factor 4α (HNF4α) and carbohydrate-responsive element-binding protein (ChREBP) in Tkfc regulation.

Main Methods:

• Luciferase reporter gene assays with Tkfc promoter constructs.
• Site-directed mutagenesis of putative transcription factor binding sites (HNF4RE1, HNF4RE2, ChoRE1).
• HNF4α knockdown and analysis of Tkfc expression in knockout mouse models (ChREBP-/- and Hnf4αΔHep).

Main Results:

• The Tkfc promoter contains HNF4α- and ChREBP-responsive elements.
• HNF4α and ChREBP synergistically activate Tkfc promoter activity.
• ChREBP-mediated activation requires HNF4α; HNF4α-mediated activation is partially dependent on ChREBP.
• Tkfc expression is reduced in ChREBP-/- and Hnf4αΔHep mice.

Conclusions:

• Tkfc is a direct target gene of both HNF4α and ChREBP in the liver.
• HNF4α is essential for ChREBP to effectively stimulate Tkfc promoter activity.
• This study elucidates a key regulatory mechanism in fructose metabolism.