Differential regulation of constitutive androstane receptor expression by hepatocyte nuclear factor4α isoforms†
Copyright policy )Differential regulation of constitutive androstane receptor expression by hepatocyte nuclear factor4α isoforms†
Constitutive androstane receptor (CAR; NR1I3) controls the metabolism and elimination of endogenous and exogenous toxic compounds by up-regulating a battery of genes. In this work, we analyzed the expression of human CAR (hCAR) in normal liver during development and in hepatocellular carcinoma (HCC) and investigated the effect of hepatocyte nuclear factor 4alpha isoforms (HNF4alpha1 and HNF4alpha7) on the hCAR gene promoter. By performing functional analysis of hCAR 5'-deletions including mutants, chromatin immunoprecipitation in human hepatocytes, electromobility shift and cotransfection assays, we identified a functional and species-conserved HNF4alpha response element (DR1: ccAGGCCTtTGCCCTga) at nucleotide -144. Both HNF4alpha isoforms bind to this element with similar affinity. However, HNF4alpha1 strongly enhanced hCAR promoter activity whereas HNF4alpha7 was a poor activator and acted as a repressor of HNF4alpha1-mediated transactivation of the hCAR promoter. PGC1alpha stimulated both HNF4alpha1-mediated and HNF4alpha7-mediated hCAR transactivation to the same extent, whereas SRC1 exhibited a marked specificity for HNF4alpha1. Transduction of human hepatocytes by HNF4alpha7-expressing lentivirus confirmed this finding. In addition, we observed a positive correlation between CAR and HNF4alpha1 mRNA levels in human liver samples during development, and an inverse correlation between CAR and HNF4alpha7 mRNA levels in HCC. These observations suggest that HNF4alpha1 positively regulates hCAR expression in normal developing and adult livers, whereas HNF4alpha7 represses hCAR gene expression in HCC.
- University of Montpellier France
- University of Montpellier France
Carcinoma, Hepatocellular, Liver Neoplasms, Receptors, Cytoplasmic and Nuclear, Response Elements, Cell Line, Gene Expression Regulation, Hepatocyte Nuclear Factor 4, Liver, Humans, Protein Isoforms, Promoter Regions, Genetic, Constitutive Androstane Receptor, Transcription Factors
Carcinoma, Hepatocellular, Liver Neoplasms, Receptors, Cytoplasmic and Nuclear, Response Elements, Cell Line, Gene Expression Regulation, Hepatocyte Nuclear Factor 4, Liver, Humans, Protein Isoforms, Promoter Regions, Genetic, Constitutive Androstane Receptor, Transcription Factors
citations This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).35 popularity This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.Average influence This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).Top 10% impulse This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.Top 10%
Citations provided by BIP!Popularity provided by BIP!