Abstract
Small heterodimer partner (SHP; NR0B2) is an atypical orphan nuclear receptor and acts as a coregulator of various nuclear receptors. Herein, we examined a novel cross talk between SHP and a forkhead transcription factor HNF3 (hepatocyte nuclear factor 3/Foxa. Transient transfection assay demonstrated that SHP inhibited the transcriptional activity of all three isoforms of HNF3, HNF3alpha, beta, and gamma. In vivo and in vitro protein interaction studies showed that SHP physically interacted with HNF3. Adenovirus-mediated overexpression of SHP significantly decreased the mRNA levels of glucose-6-phosphase (G6Pase), cholesterol 7-alpha-hydroxylase (CYP7A1), and phosphoenolpyruvate carboxykinase (PEPCK) in HepG2 cells and rat primary hepatocytes. Moreover, the mRNA level of G6Pase was notably increased by down-regulation of SHP with small interfering RNA. Interestingly, HNF3 transactivity was still repressed by SHPDelta128-139 that fails to repress nuclear receptors. Mapping of interaction domain revealed that SHP interacted with forkhead DNA binding domain of HNF3alpha. Gel mobility shift and chromatin immunoprecipitation assays demonstrated that SHP inhibits DNA binding of HNF3. These results suggest that SHP is involved in the regulation of G6Pase, CYP7A1, and PEPCK gene expression via novel mechanism of inhibition of HNF3 activity and expand the role of SHP as a coregulator of other family of transcription factors in addition to nuclear receptors.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Binding, Competitive
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Cell Line
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Cell Nucleus / chemistry
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Cholesterol 7-alpha-Hydroxylase / genetics
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Chromatin Immunoprecipitation
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DNA-Binding Proteins / antagonists & inhibitors*
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism
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Down-Regulation / genetics
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Electrophoretic Mobility Shift Assay
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Glucose-6-Phosphatase / genetics
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Helix-Loop-Helix Motifs / genetics
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Hepatocyte Nuclear Factor 3-alpha
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Hepatocyte Nuclear Factor 3-beta
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Hepatocyte Nuclear Factor 3-gamma
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Humans
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Nuclear Proteins / antagonists & inhibitors*
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism
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Phosphoenolpyruvate Carboxykinase (GTP) / genetics
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Promoter Regions, Genetic / genetics
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Protein Interaction Mapping
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RNA, Small Interfering / genetics
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Receptors, Cytoplasmic and Nuclear / analysis
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Receptors, Cytoplasmic and Nuclear / metabolism
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Receptors, Cytoplasmic and Nuclear / physiology*
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Repressor Proteins / metabolism
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Repressor Proteins / physiology*
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Transcription Factors / antagonists & inhibitors*
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Transcription Factors / genetics
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Transcription Factors / metabolism
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Transcriptional Activation / genetics
Substances
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DNA-Binding Proteins
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FOXA1 protein, human
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FOXA2 protein, human
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FOXA3 protein, human
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Hepatocyte Nuclear Factor 3-alpha
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Nuclear Proteins
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RNA, Small Interfering
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Receptors, Cytoplasmic and Nuclear
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Repressor Proteins
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Transcription Factors
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nuclear receptor subfamily 0, group B, member 2
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Hepatocyte Nuclear Factor 3-gamma
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Hepatocyte Nuclear Factor 3-beta
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Cholesterol 7-alpha-Hydroxylase
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Glucose-6-Phosphatase
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Phosphoenolpyruvate Carboxykinase (GTP)