Synergistic action of hepatocyte nuclear factors 3 and 6 on CYP2C12 gene expression and suppression by growth hormone-activated STAT5b. Proposed model for female specific expression of CYP2C12 in adult rat liver.
Growth hormone (GH) exerts sexually dimorphic effects on liver gene transcription through its sex-dependent temporal pattern of pituitary hormone secretion. CYP2C12 encodes a female-specific rat liver P450 steroid hydroxylase whose expression is activated by continuous GH stimulation of hepatocytes. Presently, we investigated the role of liver-enriched and GH-regulated transcription factors in the activation of CYP2C12 gene expression in GH-stimulated liver cells. Transcription of a CYP2C12 promoter-luciferase reporter gene in transfected HepG2 cells was activated 15-40-fold by the liver-enriched hepatocyte nuclear factor (HNF) 3 alpha, HNF3 beta, and HNF6. Synergistic interactions leading to an approximately 300-fold activation of the promoter by HNF3 beta in combination with HNF6 were observed. 5'-Deletion analysis localized the HNF6 response to a single 5'-proximal 96-nucleotide segment. By contrast, the stimulatory effects of HNF3 alpha and HNF3 beta were attributable to five distinct regions within the 1.6-kilobase CYP2C12 proximal promoter. GH activation of the signal transducer and transcriptional activator STAT5b, which proceeds efficiently in male but not female rat liver, inhibited CYP2C12 promoter activation by HNF3 beta and HNF6, despite the absence of a classical STAT5-binding site. The female-specific pattern of CYP2C12 expression is thus proposed to reflect the positive synergistic action in female liver of liver-enriched and GH-regulated transcription factors, such as HNF3 beta and HNF6, coupled with a dominant inhibitory effect of GH-activated STAT5b that is manifest in males.
Division of Cell and Molecular Biology, Department of Biology, Boston University, Boston, Massachusetts 02215, USA.
N
N
Delesque-Touchard
S H
SH
Park
D J
DJ
Waxman
D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D001483:Base Sequence; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000502:physiology*; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D013006:Growth Hormone / Q000502:physiology; D051541:Hepatocyte Nuclear Factor 3-alpha; D051543:Hepatocyte Nuclear Factor 3-gamma; D051559:Hepatocyte Nuclear Factor 6; D018398:Homeodomain Proteins / Q000502:physiology*; D006801:Humans; D008099:Liver / Q000201:enzymology; D008297:Male; D008894:Milk Proteins; D009687:Nuclear Proteins / Q000502:physiology*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D051381:Rats; D050799:STAT5 Transcription Factor; D012694:Serine; D013250:Steroid Hydroxylases / Q000235:genetics*; D015534:Trans-Activators / Q000502:physiology*; D014157:Transcription Factors; D015533:Transcriptional Activation / Q000502:physiology; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism
D017931:DNA Primers; D004268:DNA-Binding Proteins; C496499:FOXA1 protein, human; C496505:FOXA3 protein, human; C496501:Foxa1 protein, rat; C496507:Foxa3 protein, rat; D051541:Hepatocyte Nuclear Factor 3-alpha; D051559:Hepatocyte Nuclear Factor 6; D018398:Homeodomain Proteins; D008894:Milk Proteins; D009687:Nuclear Proteins; C496605:ONECUT1 protein, human; C496607:Onecut1 protein, rat; D050799:STAT5 Transcription Factor; C494095:STAT5B protein, human; C494097:Stat5b protein, rat; D015534:Trans-Activators; D014157:Transcription Factors; D051543:Hepatocyte Nuclear Factor 3-gamma; D014443:Tyrosine; D012694:Serine; D013006:Growth Hormone; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C034694:steroid 15-beta-hydroxylase