Hepatocyte nuclear factor 1alpha gene inactivation impairs chromatin remodeling and demethylation of the phenylalanine hydroxylase gene.
Hepatocyte nuclear factor 1 alpha (HNF1alpha) is a homeoprotein that is expressed in the liver, kidney, pancreas, and digestive tract. Its inactivation in mouse resulted in decreased transcription of known target genes such as albumin and alpha1-antitrypsin. In contrast, the phenylalanine hydroxylase (PAH) gene was totally silent and unresponsive to normal inducers like glucocorticoids and cyclic AMP in the liver. DNase I and micrococcal nuclease digestion of liver nuclei showed that HNF1alpha inactivation had drastic effects on the chromatin structure of the PAH regulatory regions. Three DNase I-hypersensitive sites (HSSI, HSSII, and HSSIII), typical of the actively transcribed PAH gene, were undetectable in liver from HNF1alpha-deficient animals. Both HSSII and HSSIII elements harbor HNF1 sites, but only the latter has detectable enhancer activity in transient-transfection assays. In addition, the PAH promoter in livers of HNF1alpha-deficient animals was methylated. These results suggest that HNF1alpha could activate transcription through two mechanisms. One implies participation in the recruitment of the general transcription machinery to the promoter, and the second involves the remodeling of chromatin structure and demethylation that would allow transcription factors to interact with their cognate cis-acting elements.
Pontoglio
M
M
Unité des Virus Oncogènes, URA 1644 du Centre National de la Recherche Scientifique, Département des Biotechnologies, Institut Pasteur, Paris, France.
Faust
D M
DM
Doyen
A
A
Yaniv
M
M
Weiss
M C
MC
D000818:Animals; D001665:Binding Sites; D002843:Chromatin / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000235:genetics*; D003850:Deoxyribonuclease I / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D005938:Glucocorticoids / Q000378:metabolism; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D007668:Kidney / Q000201:enzymology; D008099:Liver / Q000196:embryology / Q000201:enzymology; D051379:Mice; D008836:Micrococcal Nuclease / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics*; D010651:Phenylalanine Hydroxylase / Q000235:genetics*; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic
D002843:Chromatin; D004268:DNA-Binding Proteins; D005938:Glucocorticoids; D051538:Hepatocyte Nuclear Factor 1-alpha; C496488:Hnf1a protein, mouse; C496496:Hnf1b protein, mouse; D009687:Nuclear Proteins; D014157:Transcription Factors; D051537:Hepatocyte Nuclear Factor 1; D051539:Hepatocyte Nuclear Factor 1-beta; D000242:Cyclic AMP; D010651:Phenylalanine Hydroxylase; D003850:Deoxyribonuclease I; D008836:Micrococcal Nuclease