Identification of a novel K311 ubiquitination site critical for androgen receptor transcriptional activity

Abstract

The androgen receptor (AR) is the main driver of prostate cancer (PC) development and progression, and the primary therapeutic target in PC. To date, two functional ubiquitination sites have been identified on AR, both located in its C-terminal ligand binding domain (LBD). Recent reports highlight the emergence of AR splice variants lacking the LBD that can arise during disease progression and contribute to castrate resistance. Here, we report a novel N-terminal ubiquitination site at lysine 311. Ubiquitination of this site plays a role in AR stability and is critical for its transcriptional activity. Inactivation of this site causes AR to accumulate on chromatin and inactivates its transcriptional function as a consequence of inability to bind to p300. Additionally, mutation at lysine 311 affects cellular transcriptome altering the expression of genes involved in chromatin organization, signaling, adhesion, motility, development and metabolism. Even though this site is present in clinically relevant AR-variants it can only be ubiquitinated in cells when AR retains LBD suggesting a role for AR C-terminus in E2/E3 substrate recognition. We report that as a consequence AR variants lacking the LBD cannot be ubiquitinated in the cellular environment and their protein turnover must be regulated via an alternate pathway.

Targeting the KIF4A/AR Axis to Reverse Endocrine Therapy Resistance in Castration-resistant Prostate Cancer

“…Several studies have reported that AR levels are regulated by the ubiquitin-proteasome degradation pathway (24)(25)(26)(27). Several ubiquitin E3 ligases have also been implicated in AR-V7 degradation (28,29).…”

CNPY2 inhibits MYLIP-mediated AR protein degradation in prostate cancer cells

“…Three AR ubiquitination sites have been reported. K845 and K847 are in the AR C-terminal region (AF-2) [ 8 ], whereas K311 is in the AR N-terminal region (AF-1) [ 9 ]. K845 and K847 sites are ubiquitinated by several E3 ligases such as RNF6, Siah2, SKP2, CHIP and MDM2 [ 8 ].…”

“…Ubiquitination of the K845 and K847 by SKP2, CHIP and MDM2 induce ubiquitin-mediated AR protein degradation, while RNF6 and Siah2-mediated ubiquitination of the K845 and K857 enhance AR transcriptional activity [ 8 ]. The K311 site was recently reported to be ubiquitinated by SKP2 [ 9 ]. Ubiquitination of the K311 is critical for both AR protein stability and AR transcriptional activity [ 9 ].…”

Molecular mechanism of the TP53-MDM2-AR-AKT signalling network regulation by USP12

“…Nuclei were washed in 1 ml of buffer A without glycerol and resuspended in 1ml of buffer B (3 mM EDTA, 0.2 mM EGTA, 1 mM DTT and 1 x protease inhibitor cocktail) on ice for 30 min. Finally, sample was centrifuged at 1500 g for 5 min at 4°C and the chromatin pellet was washed in buffer B seven times (43). (7).…”