Characterization of adjacent E-box and nuclear factor 1-like DNA binding sequence in the human CYP1A2 promoter.
To better understand the molecular mechanisms of cytochrome P450 1A2 (CYP1A2) regulation, we have characterized a region of the promoter (+3 to -176) that contains a single E-box and an adjacent nuclear factor 1 (NF1)-like DNA binding site. The E-box was shown to specifically bind nuclear proteins that were recognized by antibodies against upstream stimulatory factor (USF) 1 and 2. Comparison of NF1 binding proteins in HepG2 cells and primary cultures of rat hepatocytes revealed different patterns of DNA-protein complexes, all of which were recognized by a general NF1 antibody. Mutations of the E-box resulted in substantial reduction of promoter activity in either primary hepatocytes or HepG2 cells regardless of the presence in the reporter constructs of other CYP1A2 regulatory elements, such as the hepatic nuclear factor 1 (HNF-1) binding site. In contrast, reporter gene activity of the promoter construct harboring the mutated NF1-like binding site was affected by upstream sequences when transfected into HepG2 cells, but not in primary hepatocytes. We conclude that both USF proteins and different isoforms of NF1 contribute to the constitutive expression of CYP1A2.
Narvaez
Marta J
MJ
Department of Medicine, Section of Medical Toxicology, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
Anderson
Garret R
GR
Pickwell
George V
GV
Quattrochi
Linda C
LC
D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D019388:Cytochrome P-450 CYP1A2 / Q000096:biosynthesis / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics* / Q000502:physiology; D006801:Humans; D009154:Mutation; D051839:NFI Transcription Factors; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
D022762:CCAAT-Enhancer-Binding Proteins; D051839:NFI Transcription Factors; D014157:Transcription Factors; D019388:Cytochrome P-450 CYP1A2