Heitzer, Marjet Danteel
(2005)
Mechanism of Hic-5/ARA55 action, a novel stromal-specific nuclear receptor coactivator.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Hydrogen peroxide inducible clone-5/Androgen Receptor Activator 55 (Hic-5/ARA55) is a group III LIM domain protein that functions at focal adhesion complexes as well as in the nucleus as a nuclear receptor coactivator. Because the interaction of the androgen receptor (AR) with Hic-5/ARA55 results in enhanced androgen-induced transcription, we analyzed Hic-5/ARA55 expression in prostate tissue sections from normal human donors and prostate cancer patients. In each sample, Hic-5/ARA55 expression was confined to the stromal compartment of the prostate. Furthermore, in a human prostate stromal cell line (i.e. WPMY-1 cells) Hic-5/ARA55 was localized both at focal adhesion complexes and within the soluble cytoplasmic compartment. The ability of Hic-5/ARA55 to shuttle between the nuclear and cytoplasmic compartments within WPMY-1 cells was revealed upon inhibition of nuclear export with leptomycin B (LMB). siRNA ablation experiments established endogenous Hic-5/ARA55 as a coactivator for both viral and endogenous cellular AR-regulated genes. Furthermore, chromatin immunoprecipitation (ChIP) analysis showed androgen-dependent recruitment of Hic-/ARA55 to the promoter of the stromal androgen-responsive KGF gene. Using the A1-2 derivative of T47D breast cancer cells, we examined the mechanism by which Hic-5/ARA55 potentiates nuclear receptor transactivation. Hic-5/ARA55 was found to be an important component of glucocorticoid receptor (GR)-coactivator complexes in A1-2 cells since ablation of Hic-5/ARA55 expression by RNA interference-mediated silencing reduced GR transactivation. As shown by ChIP assays, Hic-5/ARA55 is recruited to glucocorticoid-responsive promoters of the MMTV, c-fos, and p21 genes in response to glucocorticoid treatment. Results from sequential ChIP assays established that Hic-5/ARA55 associates with the corepressor, NCoR, in the absence of glucocorticoids. However, upon glucocorticoid stimulation, Hic-5/ARA55 interacts with GR-coactivator containing complexes at these promoters. Ablation of Hic-5/ARA55 expression resulted in reduction of both TIF-2 and p300 recruitment to glucocorticoid-responsive promoters. These data provide the first demonstration of a stromal-specific AR coactivator that has an impact on an androgen regulated growth factor that is essential for stromal/epithelial cell communication in the prostate. Furthermore, these results suggest that Hic-5/ARA55 is required for optimal GR-mediated gene expression possibly by providing a scaffold that organizes or stabilizes coactivator complexes at some hormone-responsive promoters.
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Details
Item Type: |
University of Pittsburgh ETD
|
Status: |
Unpublished |
Creators/Authors: |
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ETD Committee: |
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Date: |
20 December 2005 |
Date Type: |
Completion |
Defense Date: |
26 September 2005 |
Approval Date: |
20 December 2005 |
Submission Date: |
19 December 2005 |
Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
Institution: |
University of Pittsburgh |
Schools and Programs: |
School of Medicine > Cell Biology and Molecular Physiology |
Degree: |
PhD - Doctor of Philosophy |
Thesis Type: |
Doctoral Dissertation |
Refereed: |
Yes |
Uncontrolled Keywords: |
coactivator; nuclear receptor; prostate; prostate cancer |
Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-12192005-155456/, etd-12192005-155456 |
Date Deposited: |
10 Nov 2011 20:11 |
Last Modified: |
19 Dec 2016 14:38 |
URI: |
http://d-scholarship.pitt.edu/id/eprint/10428 |
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