title: Inhibitory cross-talk between STAT5b and liver nuclear factor HNF3beta: impact on the regulation of growth hormone pulse-stimulated, male-specific liver cytochrome P-450 gene expression.
abstract: STAT5b is repeatedly activated in rodent liver by the male pattern of intermittent plasma growth hormone (GH) stimulation and is required to maintain the GH pulse-regulated, male-specific pattern of liver gene expression. We presently investigate the interactions between STAT5b and hepatocyte-enriched nuclear factors (HNFs) that contribute to regulation of GH pulse-inducible, male-specific liver cytochrome P-450 (CYP) genes. STAT5 binding sites were identified in the 5'-flank of the adult male-expressed genes CYP2A2 (nucleotides -2255 to -2247), CYP4A2 (nucleotides -1872 to -1864), and CYP2C11 (nucleotides -1150 to -1142). STAT5-DNA complexes were formed by each CYP sequence with nuclear extract from GH pulse-activated male, but not female, rat liver. The CYP2C11 STAT5 site, which is flanked by HNF3 consensus sequences, conferred STAT5b-inducible reporter gene activity in GH-treated HepG2 cells. trans-Activation of the intact CYP2C11 promoter (1.8-kilobase 5'-flank) was strongly induced by the liver nuclear factors HNF1alpha and HNF3beta but, unexpectedly, was inhibited by GH-activated STAT5b. This STAT5b inhibitory effect could be reversed by HNF1alpha and reflects a functional antagonism between STAT5b and HNF3beta, as evidenced by the inhibition of HNF3beta DNA binding and transcriptional activity by STAT5b. HNF3beta, in turn, inhibited STAT5b by a novel mechanism that leads to suppression of GH-inducible STAT5b tyrosine phosphorylation, DNA binding activity, and transcriptional activity. The potential for GH-activated STAT5b to stimulate male-specific liver CYP expression can thus be modulated by HNF3beta, highlighting the complex interrelationship between STAT5b and liver transcription factors controlling expression of GH-regulated CYP genes.
authors.affiliation: Division of Cell and Molecular Biology, Department of Biology, Boston University, Boston, Massachusetts 02215, USA.
authors.forename: S H
authors.initials: SH
authors.lastname: Park
authors.forename: D J
authors.initials: DJ
authors.lastname: Waxman
mesh_terms: D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002460:Cell Line; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005260:Female; D017353:Gene Deletion; D017930:Genes, Reporter; D013006:Growth Hormone / Q000097:blood; D051542:Hepatocyte Nuclear Factor 3-beta; D006801:Humans; D008099:Liver / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D008297:Male; D008894:Milk Proteins; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D051381:Rats; D050799:STAT5 Transcription Factor; D012737:Sex Factors; D015534:Trans-Activators / Q000737:chemistry* / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D004268:DNA-Binding Proteins; C496502:FOXA2 protein, human; C496504:Foxa2 protein, rat; D008894:Milk Proteins; D009687:Nuclear Proteins; D050799:STAT5 Transcription Factor; C494095:STAT5B protein, human; C494097:Stat5b protein, rat; D015534:Trans-Activators; D014157:Transcription Factors; D051542:Hepatocyte Nuclear Factor 3-beta; D013006:Growth Hormone; D004247:DNA; D003577:Cytochrome P-450 Enzyme System; D008156:Luciferases