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Acetylation of androgen receptor by ARD1 promotes dissociation from HSP90 complex and prostate tumorigenesis.

ABSTRACT: Prostate cancer is an androgen receptor (AR)-driven disease and post-translational modification of AR is critical for AR activation. We previously reported that Arrest-defective protein 1 (ARD1) is an oncoprotein in prostate cancer. It acetylates and activates AR to promote prostate tumorigenesis. However, the ARD1-targeted residue within AR and the mechanisms of the acetylation event in prostate tumorigenesis remained unknown. In this study, we show that ARD1 acetylates AR at lysine 618 (K618) in vitro and in vivo. An AR construct with the charged lysine substitution by arginine (AR-618R) reduces RNA Pol II binding, AR transcriptional activity, prostate cancer cell growth, and xenograft tumor formation due to attenuation of AR nuclear translocation, whereas, construct mimicking neutral polar substitution acetylation at K618 by glutamine (AR-618Q) enhanced these effects beyond that of the wild-type AR. Mechanistically, ARD1 forms a ternary complex with AR and HSP90 in vitro and in vivo. Expression of ARD1 increases levels of AR acetylation and AR-HSP90 dissociation in a dose dependent manner. Moreover, the AR acetylation defective K618R mutant is unable to dissociate from HSP90 while the HSP90-dissociated AR is acetylated following ligand exposure. This work identifies a new mechanism for ligand-induced AR-HSP90 dissociation and AR activation. Targeting ARD1-mediated AR acetylation may be a potent intervention for AR-dependent prostate cancer therapy.

SUBMITTER: DePaolo JS

PROVIDER: S-EPMC5342088 | biostudies-other | 2016 Nov

REPOSITORIES: biostudies-other

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Acetylation of androgen receptor by ARD1 promotes dissociation from HSP90 complex and prostate tumorigenesis.

DePaolo John S JS Wang Zehua Z Guo Jianhui J Zhang Guanyi G Qian Chiping C Zhang Haitao H Zabaleta Jovanny J Liu Wanguo W

Oncotarget 20161101 44

Prostate cancer is an androgen receptor (AR)-driven disease and post-translational modification of AR is critical for AR activation. We previously reported that Arrest-defective protein 1 (ARD1) is an oncoprotein in prostate cancer. It acetylates and activates AR to promote prostate tumorigenesis. However, the ARD1-targeted residue within AR and the mechanisms of the acetylation event in prostate tumorigenesis remained unknown. In this study, we show that ARD1 acetylates AR at lysine 618 (K618) ...[more]

PMID: 27659526

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Project description:Prostate cancers (PCs), initially responsive to anti-androgen therapies, often advance to a hormone-refractory 'castrate-resistant' PC (CRPC) stage. However, the androgen receptor (AR) pathway remains active and key for cell growth and gene expression within tumours, even in the apparent absence of hormone. Proposed mechanisms to explain progression, including AR amplification/mutation, are insufficient to completely explain CRPC and possible roles of AR cofactors such as prohibitin (PHB) are poorly understood. We investigated whether PHB loss could sensitise PC cells and tumours to adrenal gland-derived androgens, which persist even after androgen ablation, hence contribute to development of CRPC. Using a pair of PC cell lines, inducibly expressing ectopic cDNA or RNAi for PHB, responses to different androgens and hormone concentrations were studied both in vitro and in vivo. PHB was found at the promoters of several genes, both AR and non-AR-regulated, and knockdown increased histone acetylation at these promoters. Further, PHB knockdown increased the rate of AR ligand-induced chromatin binding, and binding rate and occupancy of AR upon the PSA promoter. This resulted in increased cell growth and AR activity in response to all androgens, including promoting a response to the weaker adrenal androgens previously absent at physiological concentrations. In vivo this had functional consequences such that PHB knockdown resulted in androstenedione being sufficient to promote tumour growth, under conditions mimicking those in patients undergoing androgen ablation therapy. We conclude that reduction in PHB levels is sufficient to lower the threshold of AR activity in vitro and in vivo; this may be via a general increase in histone acetylation that could potentially affect signalling by other transcription factors. PHB loss may provide a mechanism for progression to CRPC by sensitising PC cells to 'castrate' conditions-that is, low levels of testicular androgens in the continued presence of weak adrenal and dietary androgens.

Dataset Information

Acetylation of androgen receptor by ARD1 promotes dissociation from HSP90 complex and prostate tumorigenesis.

Publications

Acetylation of androgen receptor by ARD1 promotes dissociation from HSP90 complex and prostate tumorigenesis.

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