title: FoxO4 interacts with the sterol regulatory factor SREBP2 and the hypoxia inducible factor HIF2α at the CYP51 promoter.
abstract: The late steps of cholesterol biosynthesis are oxygen demanding, requiring eleven oxygen molecules per synthesized cholesterol molecule. A key enzymatic reaction, which occurs at the top of the Bloch and Kandutsch-Russell pathways, is the demethylation of lanosterol and dihydrolanosterol (DHL). This reaction is catalyzed by lanosterol 14α demethylase (CYP51) and requires three oxygen molecules. Thus, it is the first step in the distal pathway to be susceptible to oxygen deprivation. Having previously identified that the forkhead transcription factor 4 (FoxO4) represses CYP51 expression, we aimed to characterize its role at the CYP51 promoter. Hypoxia-treated 3T3L1 cells showed decreased cholesterol biosynthesis, accumulation of lanosterol/DHL, and stimulation of FoxO4 expression and its cytoplasmic translocation to the nucleus. Transfection assays with a CYP51 promoter reporter gene revealed that FoxO4 and sterol regulatory element binding protein (SREBP)2 exert a stimulatory effect, whereas FoxO4 and the hypoxia inducible factor (HIF)2α repress CYP51 promoter activity. Electromobility shift, chromatin immunoprecipitation, pull-down, and coimmunoprecipitation assays show that FoxO4 interacts with SREBP2 and HIF2α to modulate CYP51 promoter activity. We also show an inverse correlation between FoxO4 and CYP51 in adipose tissue of ob/ob mice and mouse fetal cortical neurons exposed to hypoxia. Overall, these studies demonstrate a role for FoxO4 in the regulation of CYP51 expression.
authors.affiliation: Departments of Laboratory Medicine University of California, San Francisco, CA 94143.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhu
authors.forename: Xiangning
authors.initials: X
authors.lastname: Jiang
authors.forename: Farid F
authors.initials: FF
authors.lastname: Chehab
mesh_terms: D041721:3T3-L1 Cells; D052436:Adipose Tissue, White / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D018797:Cell Cycle Proteins; D015687:Cell Hypoxia; D002478:Cells, Cultured; D005260:Female; D051858:Forkhead Transcription Factors; D015870:Gene Expression; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D058886:Sterol 14-Demethylase / Q000235:genetics*; D051782:Sterol Regulatory Element Binding Protein 2 / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D018797:Cell Cycle Proteins; D051858:Forkhead Transcription Factors; D058886:Sterol 14-Demethylase; D051782:Sterol Regulatory Element Binding Protein 2; D014157:Transcription Factors; D000099162:Endothelial PAS Domain-Containing Protein 1; C108803:FOXO4 protein, human
keywords: cholesterol; dihydrolanosterol; forkhead transcription factor 4; hypoxia-inducible factor 2α; lanosterol 14α demethylase; sterol regulatory element binding protein 2