title: 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 androgen-dependent 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 androgen-responsive prostate-specific antigen (PSA) gene. Luciferase reporter, minigene splicing assays, and RNA interference (RNAi) were used to examine a functional role of p68 in AR-regulated 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.
authors.affiliation: Northern Institute for Cancer Research and Institute of Human Genetics, Newcastle University, Newcastle-upon-Tyne, United Kingdom.
authors.forename: Emma L
authors.initials: EL
authors.lastname: Clark
authors.forename: Anne
authors.initials: A
authors.lastname: Coulson
authors.forename: Caroline
authors.initials: C
authors.lastname: Dalgliesh
authors.forename: Prabhakar
authors.initials: P
authors.lastname: Rajan
authors.forename: Samantha M
authors.initials: SM
authors.lastname: Nicol
authors.forename: Stewart
authors.initials: S
authors.lastname: Fleming
authors.forename: Rakesh
authors.initials: R
authors.lastname: Heer
authors.forename: Luke
authors.initials: L
authors.lastname: Gaughan
authors.forename: Hing Y
authors.initials: HY
authors.lastname: Leung
authors.forename: David J
authors.initials: DJ
authors.lastname: Elliott
authors.forename: Frances V
authors.initials: FV
authors.lastname: Fuller-Pace
authors.forename: Craig N
authors.initials: CN
authors.lastname: Robson
mesh_terms: D017398:Alternative Splicing / Q000235:genetics*; D000818:Animals; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000502:physiology*; D018450:Disease Progression; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008297:Male; D017430:Prostate-Specific Antigen / Q000235:genetics / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D034741:RNA, Small Interfering / Q000494:pharmacology; D011944:Receptors, Androgen / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism / Q000502:physiology; D015854:Up-Regulation
chemical_list: D034741:RNA, Small Interfering; D011944:Receptors, Androgen; D015534:Trans-Activators; D017430:Prostate-Specific Antigen; D053487:DEAD-box RNA Helicases