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Mechanism of Hic-5/ARA55 action, a novel stromal-specific nuclear receptor coactivator

Heitzer, Marjet Danteel (2005) Mechanism of Hic-5/ARA55 action, a novel stromal-specific nuclear receptor coactivator. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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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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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Heitzer, Marjet Danteelmdhst25@pitt.eduMDHST25
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairZeleznik, Anthonyzeleznik@pitt.eduZELEZNIK
Committee MemberWells, Alanwellsa@upmc.eduAHW6
Committee MemberDeFranco, Donalddod1@pitt.eduDOD1
Committee MemberNichols, Markmnichols@pitt.eduMNICHOLS
Committee MemberWalker, Williamwalkerw@pitt.eduWALKERW
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:, etd-12192005-155456
Date Deposited: 10 Nov 2011 20:11
Last Modified: 19 Dec 2016 14:38


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