A coregulatory role for the TRAP-Mediator complex in androgen receptor-mediated gene expression

University of Maryland, Baltimore, Baltimore, Maryland, United States
Journal of Biological Chemistry (Impact Factor: 4.6). 12/2002; 277(45):42852-8. DOI: 10.1074/jbc.M206061200
Source: PubMed

ABSTRACT The human thyroid hormone receptor-associated protein (TRAP)-Mediator complex was originally identified as a large multimeric complex that copurifies with the thyroid hormone receptor (TR) from HeLa cells and markedly enhances TR-mediated transcription in vitro. More recent studies have implicated TRAP-Mediator as a coactivator for a broad range of nuclear hormone receptors as well as other classes of transcriptional activators. Here we present evidence that TRAP-Mediator plays a functional role in androgen receptor (AR)-mediated transcription. We show that several subunits of the complex ligand-dependently coimmunoprecipitate with AR from both prostate cancer LNCaP cells and from HeLa cells stably transfected with AR. The 220-kDa subunit of the complex (TRAP220) can contact the ligand-binding domain of AR in vitro, possibly implicating TRAP220 involvement in targeting AR to the holocomplex. Consistent with a TRAP-Mediator coactivator role, transient overexpression of the TRAP220, TRAP170, and TRAP100 subunits enhanced ligand-dependent transcription by AR in cultured cells. Finally, chromatin immunoprecipitation assays show that TRAP220 is recruited to the androgen-responsive prostate-specific antigen gene promoter in vivo in ligand-stimulated LNCaP cells. Collectively, these data suggest that TRAP-Mediator may play an important coregulatory role in AR-mediated gene expression.

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    • "Other coregulatory proteins possessing enzymatic activity have been identified that interact with AR or its associated p160 proteins including CARM1 (methyltransferase), LSD1 (lysine specific demethylase), and CBP/p300 (HAT activity) (Koh et al., 2002; Metzger et al., 2005; Wang et al., 2005). AR can also recruit TRAP220, a subunit of the mediator complex, to target genes providing a direct point of contact with components of the basal transcription machinery (Wang et al., 2002). More recently, the homeobox protein, HOXB13, has been shown to interact with and suppress AR transcriptional activity and androgen-mediated prostate cancer cell growth when overexpressed in cells (Jung et al., 2004). "
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    ABSTRACT: HOXB13 is a member of the homeodomain family of sequence-specific transcription factors and, together with the androgen receptor (AR), plays a critical role in the normal development of the prostate gland. We demonstrate here that, in prostate cancer cells, HOXB13 is a key determinant of the response to androgens. Specifically, it was determined that HOXB13 interacts with the DNA-binding domain of AR and inhibits the transcription of genes that contain an androgen-response element (ARE). In contrast, the AR:HOXB13 complex confers androgen responsiveness to promoters that contain a specific HOXB13-response element. Further, HOXB13 and AR synergize to enhance the transcription of genes that contain a HOX element juxtaposed to an ARE. The profound effects of HOXB13 knockdown on androgen-regulated proliferation, migration, and lipogenesis in prostate cancer cells highlight the importance of the observed changes in gene expression.
    Molecular cell 11/2009; 36(3):405-16. DOI:10.1016/j.molcel.2009.10.020 · 14.46 Impact Factor
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    • "Western blots were performed as previously described (Wang et al., 2002). Antibodies used are available in the Supplemental Experimental Procedures. "
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    • "The identity of the proteins corresponding to each clone and additional details of the screen are presented in supplemental Table S1 available online. Several previously identified AR and nuclear receptor (NR) interacting proteins were identified in this screen including ARA24, gelsolin, PTEN, TFIIF, supervillin, HOXB13, TRIP12, and PPARBP (Hsiao et al., 1999; Jung et al., 2004; Lee et al., 1995; Lin et al., 2004; McEwan and Gustafsson, 1997; Ting et al., 2002; Wang et al., 2002). The identification of multiple alleles of known AR and NR interacting proteins served as an initial validation of the approach we used to identify protein domains that were capable of highlighting functionally important protein-protein interactions surfaces on the receptor. "
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