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Temporal Analysis of Steroidogenic Factor‐1 Binding to the human CYP17 Promoter: Roles of Ligand Binding, Coactivator Recruitment, and Phosphorylation
Author(s) -
Dammer Eric,
Leon Adam,
Sewer Marion B.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a969
Subject(s) - coactivator , steroidogenic factor 1 , chromatin immunoprecipitation , dephosphorylation , transcription factor , nuclear receptor coactivator 1 , phosphorylation , promoter , biology , chemistry , microbiology and biotechnology , nuclear receptor , gene expression , biochemistry , gene , phosphatase
Steroidogenic factor (SF‐1) is a nuclear receptor that is essential for steroid hormone biosynthesis and endocrine development. Adrenocorticotropin (ACTH) acts via a cAMP‐dependent pathway to induce human CYP17 gene expression by promoting the binding of a protein complex containing SF‐1, p54 nrb , and polypyrimidine‐tract binding protein associated splicing factor. We have recently demonstrated that sphingosine (SPH) and phosphatidic acid (PA) are endogenous ligands for SF‐1. The aim of the current study was to further characterize the roles of ligand binding, coactivator recruitment, and phosphorylation in the transcription of CYP17. We used chromatin immunoprecipitation to analyze the temporal changes in the binding of SF‐1, p54 nrb , PSF, and several coactivators to the CYP17 promoter. Both dibutyryl cAMP (Bt 2 cAMP) and PA stimulate the binding of SRC‐1 and GCN5 to the CYP17 promoter and induce CYP17 mRNA expression. In contrast, SPH antagonizes the stimulatory effects of Bt 2 cAMP and PA on coactivator binding and CYP17 transcription. Mutation of putative phosphorylation sites on SF‐1 and inhibition of ERK and PP2A activity reveal that Bt 2 cAMP and PA promote SF‐1 binding to the promoter and coactivator recruitment by stimulating dephosphorylation of the receptor. These studies demonstrate that SF‐1 activates the transcription of CYP17 by the coordinate actions of ligand exchange (displacement of SPH by PA), dephosphorylation, and coactivator binding. This work is supported by NIH (GM073241), NSF (MCB‐0347682), and the Georgia Cancer Coalition.