HNF4 and COUP-TFII interact to modulate transcription of the cholesterol 7alpha-hydroxylase gene (CYP7A1).

HNF4 and COUP-TFII interact to modulate transcription of the cholesterol 7alpha-hydroxylase gene (CYP7A1).

Stroup D; Chiang J Y

Journal of lipid research

2000

2000-01

The gene for cholesterol 7alpha-hydroxylase (CYP7A1) contains a sequence at nt -149 to -118 that was found to play a large role in determining the overall transcriptional activity and regulation of the promoter. Hepatocyte nuclear factor 4 (HNF4) and chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) synergistically activate transcription of the CYP7A1 promoter. Transactivation of CYP7A1 by HNF4 in the human hepatoma cell line, HepG2, was enhanced by cotransfection with COUP-TFII or the basal transcription element binding protein (BTEB). HNF4 prepared from rat liver nuclear extracts bound to oligomers homologous to the nt -146 to -134 sequences in electrophoretic mobility shift assays (EMSA), which corresponded to a conserved region containing a direct repeat of hormone response elements spaced by one nucleotide (DR1). The sequences surrounding this DR1 were found to be essential for the HNF4 transactivation. In vitro-translated COUP-TFII was found to bind the adjacent sequences from nt -139 to -128 (DR0), but COUP-TFII interacted with this region at a much lower affinity than to the COUP-TFII-site at nt -72 to -57 (DR4). Mutations at nt -139 to -128 or nt -72 to -57 reduced the COUP-TFII and HNF4 synergy; however, these

Humans; Animals; Rats; Liver/metabolism; Recombinant Proteins/metabolism; Base Sequence; Mutation; DNA Primers; Cholesterol 7-alpha-Hydroxylase/*genetics; Transcription Factors/*metabolism; Hepatocyte Nuclear Factor 4; DNA-Binding Proteins/*metabolism; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Luciferases/genetics; COUP Transcription Factor II; COUP Transcription Factors; Phosphoproteins/*metabolism; Genes; Sprague-Dawley; Cultured; Genetic; Tumor Cells; Reporter; Promoter Regions; *Transcription; *Receptors; Steroid

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