title: Repression of hepatocyte nuclear factor 4alpha tumor suppressor p53: involvement of the ligand-binding domain and histone deacetylase activity.
abstract: Tumor suppressor p53 is known to inhibit transactivation by certain nuclear receptors, and overexpressed p53 is known to correlate with poor differentiation in liver cancer. Therefore, we investigated whether wild-type p53 might also affect the function of hepatocyte nuclear factor 4alpha1 (HNF4alpha1), an orphan receptor required for liver differentiation. Our results show that HNF4alpha1-mediated transactivation is repressed by p53 but that the mechanism of repression is not due to inhibition of HNF4alpha1 DNA binding. Rather, transfections with Gal4 fusion constructs indicate that the repression is via the ligand-binding domain of HNF4alpha1. Furthermore, we found that p53 in human embryonic kidney whole-cell extracts preferentially bound the ligand-binding domain of HNF4alpha1 and that the activation function 2 region was required for the binding. Competition for coactivator CREB binding protein could not entirely account for the repression but trichostatin A, an inhibitor of histone deacetylase activity, could reverse p53-mediated repression of HNF4alpha1. In contrast, p53-mediated repression of transcriptional activation of the same promoter by another transcriptional activator, CCAAT/enhancer-binding protein-alpha, could not be reversed by the addition of trichostatin A. These results suggest that p53, like other transcriptional repressors, inhibits transcription by multiple mechanisms, one of which involves interaction with the ligand-binding domain and recruitment of histone deacetylase activity.
authors.affiliation: Environmental Toxicology Graduate Program, University of California, Riverside, California 92521, USA.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Maeda
authors.forename: Shawn D
authors.initials: SD
authors.lastname: Seidel
authors.forename: Gang
authors.initials: G
authors.lastname: Wei
authors.forename: Xuan
authors.initials: X
authors.lastname: Liu
authors.forename: Frances M
authors.initials: FM
authors.lastname: Sladek
mesh_terms: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D050882:CREB-Binding Protein; D002460:Cell Line; D004268:DNA-Binding Proteins; D024202:Electrophoretic Mobility Shift Assay; D015870:Gene Expression; D051557:Hepatocyte Nuclear Factor 4; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism*; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D008024:Ligands; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021122:Protein Subunits; D012097:Repressor Proteins / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D051557:Hepatocyte Nuclear Factor 4; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D008024:Ligands; C403128:MLX protein, human; D009687:Nuclear Proteins; D010750:Phosphoproteins; D021122:Protein Subunits; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; C012589:trichostatin A; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; D006655:Histone Deacetylases