title: Role of hepatocyte nuclear factors in transcriptional regulation of male-specific CYP2A2.
abstract: Cytochrome P450 2A2 (CYP2A2) is an adult male-specific rat liver steroid hydroxylase whose sex-dependent expression is regulated at the transcriptional level by sexually dimorphic pituitary growth hormone (GH) secretory patterns. In contrast to CYP2C11 and other male-specific, plasma GH pulse-inducible liver genes, CYP2A2 is highly expressed in hypophysectomized rat liver, despite the absence of GH stimulation. CYP2A2 promoter fragments 0.9-6.2 kb long exhibited unusually high basal promoter activity when transfected into the liver cell line HepG2. A further approximately 2.5-fold increase in activity was obtained by cotransfection of hepatocyte nuclear factor (HNF) 3gamma or HNF4alpha. CYP2A2 promoter activity was inhibited approximately 85% by transfection of HNF3beta or HNF6, both of which are more highly expressed in female than male liver and can strongly trans-activate the female-specific CYP2C12 promoter. The male GH pulse-activated transcription factor STAT5b had no effect on CYP2A2 promoter activity, either alone or in combination with HNF3gamma and HNF4alpha, consistent with the GH pulse-independence of CYP2A2 expression. By contrast, STAT5b synergistically enhanced the transcriptional activity of HNF4alpha toward two other male-specific liver target genes, Cyp2d9 and CYP8B1. Furthermore, STAT5b in combination with the HNF4alpha coactivator peroxisome proliferator-activated receptor gamma coactivator-1alpha strongly enhanced the transcriptional activity of HNF4alpha toward CYP8B1 but not toward CYP2A2. These findings support the hypothesis that sex-dependent HNFs contribute to the sexually dimorphic expression of CYP2A2 and other liver CYPs and highlight the ability of STAT5b to act in concert with HNF4alpha to regulate select male-specific liver CYP genes.
authors.affiliation: Division of Cell and Molecular Biology, Department of Biology Boston University, Boston, Massachusetts 02215, USA.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Wiwi
authors.forename: David J
authors.initials: DJ
authors.lastname: Waxman
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics*; D019556:COS Cells; D006528:Carcinoma, Hepatocellular; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D003577:Cytochrome P-450 Enzyme System; D000072467:Cytochrome P450 Family 2; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005260:Female; D051542:Hepatocyte Nuclear Factor 3-beta; D051543:Hepatocyte Nuclear Factor 3-gamma; D051557:Hepatocyte Nuclear Factor 4; D051559:Hepatocyte Nuclear Factor 6; D022781:Hepatocytes / Q000502:physiology*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D008113:Liver Neoplasms; D008297:Male; D051379:Mice; D008894:Milk Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000502:physiology; D011817:Rabbits; D051381:Rats; D050799:STAT5 Transcription Factor; D012727:Sex Characteristics; D013253:Steroid 12-alpha-Hydroxylase / Q000235:genetics; D039181:Steroid 16-alpha-Hydroxylase / Q000235:genetics; D013250:Steroid Hydroxylases / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; C496503:Foxa2 protein, mouse; C496504:Foxa2 protein, rat; C496506:Foxa3 protein, mouse; C496507:Foxa3 protein, rat; D051557:Hepatocyte Nuclear Factor 4; D051559:Hepatocyte Nuclear Factor 6; C496593:Hnf4a protein, mouse; C496594:Hnf4a protein, rat; D018398:Homeodomain Proteins; D008894:Milk Proteins; D009687:Nuclear Proteins; C496606:Onecut1 protein, mouse; C496607:Onecut1 protein, rat; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D010750:Phosphoproteins; C485290:Ppargc1a protein, mouse; D050799:STAT5 Transcription Factor; C494096:Stat5b protein, mouse; C494097:Stat5b protein, rat; D015534:Trans-Activators; D014157:Transcription Factors; D051543:Hepatocyte Nuclear Factor 3-gamma; D051542:Hepatocyte Nuclear Factor 3-beta; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C450279:CYP2C11 protein, rat; C504575:CYP2D9 protein, mouse; D000072467:Cytochrome P450 Family 2; D039181:Steroid 16-alpha-Hydroxylase; C029009:steroid hormone 7-alpha-hydroxylase; D013253:Steroid 12-alpha-Hydroxylase