Identification of a novel cofactor, SH3YL1, that functions through interaction with the androgen receptor N-terminal polyproline domain

Nuclear receptor (NR)-mediated transcription is a dynamic process that is regulated by the binding of distinct ligands that induce conformational changes in the NR. These molecular alterations lead to the recruitment of unique cofactors (coactivators or corepressors) that control the expression of NR-regulated genes. Here, we show that a stretch of proline residues located within the N-terminus of AR is necessary for maximal androgen-mediated prostate cancer cell growth and migration. Furthermore, this polyproline domain is necessary for the expression of a subset of AR-target genes, but is dispensable for classical AR-mediated gene transcription. Using T7 phage display, we subsequently identified a novel AR-interacting protein, SH3YL1, whose interaction with AR is dependent upon this polyproline domain. Like the AR polyproline domain, SH3YL1 was required for maximal androgen-mediated cell growth and migration. Microarray analysis revealed that SH3YL1 also regulated a subset of AR-modulated genes. Correspondingly, we identified ubinuclein1 (UBN1), a key member of a histone H3.3 chaperone complex, as a transcriptional target of AR/SH3YL1. Moreover, UBN1 was necessary for maximal androgen-mediated proliferation and migration. Collectively, our data link a specific surface located within ARs N-terminus to the recruitment of a novel cofactor, SH3YL1, which is required for the androgen-mediated expression of UBN1. Importantly, this signaling network was important for both androgen-mediated prostate cancer cell growth and migration. This work is significant because it could aid in the development of selective androgen receptor modulators (SARMs) and have therapeutic implications for AR-driven diseases.

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Blessing AM, Ganesan S, Rajapakshe K, Ying Sung Y, Reddy Bollu L, Shi Y, Cheung E, Coarfa C, Chang JT, McDonnell DP, Frigo DE