Hepatic nuclear factor 3- and hormone-regulated expression of the phosphoenolpyruvate carboxykinase and insulin-like growth factor-binding protein 1 genes.
The rate of transcription of the hepatic phosphoenolpyruvate carboxykinase (PEPCK) and insulin-like growth factor-binding protein 1 (IGFBP-1) genes is stimulated by glucocorticoids and inhibited by insulin. In both cases, the effect of insulin is dominant, since it suppresses both basal and glucocorticoid-stimulated PEPCK or IGFBP-1 gene transcription. Analyses of both promoters by transfection of PEPCK or IGFBP-1-chloramphenicol acetyltransferase fusion genes into rat hepatoma cells has led to the identification of insulin response sequences (IRSs) in both genes. The core IRS, T(G/A)TTTTG, is the same in both genes, but the PEPCK promoter has a single copy of this element whereas the IGFBP-1 promoter has two copies arranged as an inverted palindrome. The IGFBP-1 IRS and PEPCK IRS both bind the alpha and beta forms of hepatic nuclear factor 3 (HNF-3), although the latter does so with a sixfold-lower relative affinity. Both the PEPCK and the IGFBP-1 IRSs also function as accessory factor binding sites required for the full induction of gene transcription by glucocorticoids. A combination of transient transfection and DNA binding studies suggests that HNF-3 is the accessory factor that supports glucocorticoid-induced gene transcription. In both genes, the HNF-3 binding site overlaps the IRS core motif(s). A model in which insulin is postulated to mediate its negative effect on glucocorticoid-induced PEPCK and IGFBP-1 gene transcription indirectly by inhibiting HNF-3 action is proposed.
O'Brien
R M
RM
Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, Tennessee 37232.
Noisin
E L
EL
Suwanichkul
A
A
Yamasaki
T
T
Lucas
P C
PC
Wang
J C
JC
Powell
D R
DR
Granner
D K
DK
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D006528:Carcinoma, Hepatocellular; D002352:Carrier Proteins / Q000096:biosynthesis*; D002460:Cell Line; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D051541:Hepatocyte Nuclear Factor 3-alpha; D051542:Hepatocyte Nuclear Factor 3-beta; D051543:Hepatocyte Nuclear Factor 3-gamma; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D018970:Insulin-Like Growth Factor Binding Protein 1; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008113:Liver Neoplasms; D008114:Liver Neoplasms, Experimental; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000096:biosynthesis / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012045:Regulatory Sequences, Nucleic Acid; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C496499:FOXA1 protein, human; C496502:FOXA2 protein, human; C496505:FOXA3 protein, human; C496501:Foxa1 protein, rat; C496504:Foxa2 protein, rat; C496507:Foxa3 protein, rat; D051541:Hepatocyte Nuclear Factor 3-alpha; D007328:Insulin; D018970:Insulin-Like Growth Factor Binding Protein 1; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D011965:Receptors, Glucocorticoid; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D051543:Hepatocyte Nuclear Factor 3-gamma; D051542:Hepatocyte Nuclear Factor 3-beta; D003907:Dexamethasone; D004247:DNA; D010729:Phosphoenolpyruvate Carboxykinase (GTP)