Mitogen-activated protein kinase-mediated disruption of enhancer-promoter communication inhibits hepatocyte nuclear factor 4alpha expression

Mol Cell Biol. 2006 Oct;26(19):7017-29. doi: 10.1128/MCB.00297-06.

Abstract

Hepatocyte nuclear factor 4 (HNF-4) is a key member of the transcription factor network regulating hepatocyte differentiation and function. Activation of the HNF-4 gene involves physical interaction between a distant enhancer and the proximal promoter region, bound by distinct sets of transcription factors. Here we report that, upon mitogen-activated protein (MAP) kinase activation, HNF-4 expression is downregulated in human hepatoma cells. This effect is mediated by the loss of CEBPalpha expression. During MAP kinase signaling, the recruitment of HNF-3beta and HNF-1alpha to the HNF-4 enhancer and RNA polymerase II to the proximal HNF-4 promoter was compromised. CBP, Brg1, and TFIIB were also dissociated from the HNF-4 regulatory regions, and the enhancer-promoter complex was disrupted. Interestingly, the extent of nucleosome acetylation did not decrease at either regulatory region, and HNF-6 and HNF-1alpha, as well as components of the TFIID, remained associated with the proximal promoter during the repressed state. The results point to an absolute requirement of enhancer-promoter communication for maintaining the active state of the HNF-4 gene and provide evidence for a molecular bookmarking mechanism, which may contribute to the prevention of permanent silencing of the locus during the repressed state.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylation / drug effects
  • CCAAT-Enhancer-Binding Protein-alpha / deficiency
  • CCAAT-Enhancer-Binding Protein-alpha / genetics
  • Cells, Cultured
  • DNA Helicases
  • Down-Regulation / drug effects
  • Enhancer Elements, Genetic / genetics*
  • Enzyme Activation / drug effects
  • Hepatocyte Nuclear Factor 4 / deficiency
  • Hepatocyte Nuclear Factor 4 / genetics*
  • Hepatocyte Nuclear Factor 4 / metabolism*
  • Histones / metabolism
  • Humans
  • Mitogen-Activated Protein Kinase 1 / metabolism*
  • Models, Genetic
  • Nuclear Proteins / metabolism
  • Promoter Regions, Genetic / genetics*
  • RNA Interference
  • RNA Polymerase II / metabolism
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Signal Transduction / drug effects
  • Tetradecanoylphorbol Acetate / pharmacology
  • Transcription Factors / metabolism

Substances

  • CCAAT-Enhancer-Binding Protein-alpha
  • HNF4A protein, human
  • Hepatocyte Nuclear Factor 4
  • Histones
  • Nuclear Proteins
  • RNA, Messenger
  • Transcription Factors
  • Mitogen-Activated Protein Kinase 1
  • RNA Polymerase II
  • SMARCA4 protein, human
  • DNA Helicases
  • Tetradecanoylphorbol Acetate