HORMONAL REGULATION OF ANDROGEN RECEPTOR EXPRESSION

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The androgen receptor (AR) is a ligand-activated transcription factor that binds to androgen responsive elements (AREs) associated with androgen- regulated genes. AR is essential for androgen mediated male sexual development and plays a role in prostate cancer etiology and progression. Androgen promotes tissue-specific up- an down-regulation of AR mRNA, suggesting roles for both AR and cell-specific factors in AR mRNA autoregulation. Key goals of this proposal are to identify these non-AR factors and to define their contribution to AR mRNA up-regulation. Because androgen responsiveness is related to AR levels, autoregulation of AR mRNA may be critical in modulating hormonal sensitivity in normal and neoplastic cells. Consistent with this idea, we observed that androgen- mediated up-regulation of AR mRNA and protein is associated with enhanced cellular androgen sensitivity. The AR gene promoter and upstream region have not been demonstrated to contain the ARE and ARE-2, in exons of an internal 6.5 kb androgen responsive region of the AR gene. These Res are located on a 350 bp fragment of the R cDNA that consists of exons D and E. Both the 6.5 kb and 350 bp fragments exhibit cell-specific androgen regulation in reporter gene assays that mirrors up-regulation of the native AR gene. All four AREs are required for AR binding to the 350 bp region and for transcriptional up-regulation of AR mRNA. Furthermore, like the native gene, the 6.5 kb and 350 bp regions are not regulated by glucocorticoid and glucocorticoid receptor (GR) despite the presence of AREs. Resembling the hormone response element (HRE) consensus sequence. HREs are bound and regulated by GR in several other genes. The aims of this proposal are to utilize in vivo foot-printing techniques to examine binding of AR, GR and non-receptor factors to exons D and E of the 6.5 kb androgen responsive region present as stably integrated templates. We will determine whether the patterns of receptor and nuclear factor binding differ in response to androgen (and glucocorticoids) in cells in which the androgen responsive region is active versus inactive. We will identify and characterize the non-receptor factor(s) that binds differentially and determine the role of this factor(s) in cell- and androgen-specific AR mRNA up-regulation. The long term goal of these studies is to provide a comprehensive physical and functional characterization of R mRNA autoregulatory mechanisms and to relate these mechanisms to hormonal responsiveness in normal and neoplastic cells.