The RNA Helicase p68 Is a Novel Androgen Receptor Coactivator Involved in Splicing and Is Overexpressed in Prostate Cancer

Abstract

The androgen receptor (AR) is a member of the nuclear steroid hormone receptor family and is thought to play an important role in the development of both androgendependent and androgen-independent prostatic malignancy. Elucidating roles by which cofactors regulate AR transcriptional activity may provide therapeutic advancement for prostate cancer (PCa). The DEAD box RNA helicase p68 (Ddx5) was identified as a novel AR-interacting protein by yeast two-hybrid screening, and we sought to examine the involvement of p68 in AR signaling and PCa. The p68-AR interaction was verified by colocalization of overexpressed protein by immunofluorescence and confirmed in vivo by coimmunoprecipitation in the PCa LNCaP cell line. Chromatin immunoprecipitation in the same cell line showed AR and p68 recruitment to the promoter region of the androgenresponsive prostate-specific antigen (PSA) gene. Luciferase reporter, minigene splicing assays, and RNA interference (RNAi) were used to examine a functional role of p68 in ARregulated gene expression, whereby p68 targeted RNAi reduced AR-regulated PSA expression, and p68 enhanced AR-regulated repression of CD44 splicing (P = 0.008). Tyrosine phosphorylation of p68 was found to enhance coactivation of ligand-dependent transcription of AR-regulated luciferase reporters independent of ATP-binding. Finally, we observe increased frequency and expression of p68 in PCa compared with benign tissue using a comprehensive prostate tissue microarray (P = 0.003; P = 0.008). These findings implicate p68 as a novel AR transcriptional coactivator that is significantly overexpressed in PCa with a possible role in progression to hormone-refractory disease.

RNA helicases in infection and disease

“…145 DDX5/p68, a helicase required for miRNA processing and maturation, 146 is upregulated in different cancer types, among them colorectal, 147 prostate 148 and breast virulence in a mouse model, 121 which can be restored in complementation experiments with wild-type Vad1. The Vad1 helicase core belongs to the RCK/p54 subfamily of DExD/H box proteins that are implicated in mRNA decapping and deadenylation.…”

Dual role of the ddx5/ddx17 RNA helicases in the control of the pro-migratory NFAT5 transcription factor

“…It is believed that ddx5 and ddx17 are recruited on target gene promoters by these transcriptional factors and in turn recruit the RNA polymerase II or enzymes with histone acetylase or deacetylase activities (Metivier et al, 2003;Rossow and Janknecht, 2003;Wilson et al, 2004;Janknecht, 2010;Dutertre et al, 2010a;Fuller-Pace and Moore, 2011). In addition, ddx5 and ddx17 copurify with the splicing machinery or spliceosome and can change alternative splicing-site selection in transcripts produced from the H-ras, CD44 and Tau genes Honig et al, 2002;Guil et al, 2003;Camats et al, 2008;Clark et al, 2008;Kar et al, 2011). There are now many reports indicating that these multifunctional proteins have important implications for cancer development, as recently reviewed (Janknecht, 2010;FullerPace and Moore, 2011).…”

MicroRNA: sex steroids, hormonal carcinogenesis, hormonal sensitivity of tumor tissue

“…Так, активность некоторых компонентов «ми-кропроцессорного» ядерного комплекса (РНКазы III Drosha, p68) регулируется андрогенами [33,42]. Инте-ресно, что активность одного из основных ферментов микроРНК-процессинга -РНКазы III Drosha -акти-вируется AR в клетках РПЖ [33], но ингибируется ERα в клетках РМЖ [20], что, несмотря на определенное сходство [2], свидетельствует и о несомненных разли-чиях между гормон-опосредованными процессами, лежащими в основе этих двух онкологических заболе-ваний.…”