In vivo protein-DNA interactions on a glucocorticoid response unit of a liver-specific gene: hormone-induced transcription factor binding to constitutively open chromatin.
Transcription from the liver promoter of a 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2) gene depends on the presence of glucocorticoids that act via a glucocorticoid response unit (GRU) located in the first intron. The promoter and the GRU are in a constitutively open chromatin configuration. To determine how glucocorticoids would affect factor binding to the GRU in absence of chromatin remodeling, we have used a combination of in vitro DNA-binding assays and in vivo genomic footprinting in rat hepatocytes and hepatoma cells. We found that, in the absence of glucocorticoids, the GRU binds nuclear factor-I (NF-I). Glucocorticoid treatment modified factor binding to the NF-I site and induced the binding of hepatocyte nuclear factor-3 (HNF-3). Transfection assays showed that HNF-3 cooperates with the glucocorticoid receptor in stimulating transcription. In contrast with the lack of effect of glucocorticoids on factor binding to constitutively open GRUs of other genes, HNF-3 binding to the open PFK-2 GRU was hormone-dependent. Therefore, the PFK-2 GRU behaves as a novel type of GRU.
Zimmermann
P L
PL
Louvain University Medical School and International Institute of Cellular and Molecular Pathology, Brussels, Belgium.
Pierreux
C E
CE
Rigaud
G
G
Rousseau
G G
GG
Lemaigre
F P
FP
D000818:Animals; D001483:Base Sequence; D002843:Chromatin / Q000378:metabolism*; D004247:DNA; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D005938:Glucocorticoids / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D008969:Molecular Sequence Data; D010732:Phosphofructokinase-1 / Q000235:genetics*; D025481:Phosphofructokinase-2; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics*; D011485:Protein Binding; D051381:Rats; D017208:Rats, Wistar; D014157:Transcription Factors / Q000378:metabolism*
D002843:Chromatin; D004268:DNA-Binding Proteins; D005938:Glucocorticoids; D014157:Transcription Factors; D004247:DNA; D025481:Phosphofructokinase-2; D010732:Phosphofructokinase-1; D010744:Phosphoric Monoester Hydrolases