title: The RNA-binding protein Sam68 regulates expression and transcription function of the androgen receptor splice variant AR-V7.
abstract: Castration-resistant (CR) prostate cancer (PCa) partly arises due to persistence of androgen receptor (AR) transcriptional activity in the absence of cognate ligand. An emerging mechanism underlying the CRPCa phenotype and predicting response to therapy is the expression of the constitutively-active AR-V7 splice variant generated by AR cryptic exon 3b inclusion. Here, we explore the role of the RNA-binding protein (RBP) Sam68 (encoded by KHDRBS1), which is over-expressed in clinical PCa, on AR-V7 expression and transcription function. Using a minigene reporter, we show that Sam68 controls expression of exon 3b resulting in an increase in endogenous AR-V7 mRNA and protein expression in RNA-binding-dependent manner. We identify a novel protein-protein interaction between Sam68 and AR-V7 mediated by a common domain shared with full-length AR, and observe these proteins in the cell nucleoplasm. Using a luciferase reporter, we demonstrate that Sam68 co-activates ligand-independent AR-V7 transcriptional activity in an RNA-binding-independent manner, and controls expression of the endogenous AR-V7-specific gene target UBE2C. Our data suggest that Sam68 has separable effects on the regulation of AR-V7 expression and transcriptional activity, through its RNA-binding capacity. Sam68 and other RBPs may control expression of AR-V7 and other splice variants as well as their downstream functions in CRPCa.
authors: Institute of Cancer Sciences, University of Glasgow, Glasgow, UK.
authors: Jacqueline
authors: J
authors: Stockley
authors: Institute of Cancer Sciences, University of Glasgow, Glasgow, UK.
authors: Elke
authors: E
authors: Markert
authors: Cancer Research UK Beatson Institute, Glasgow, UK.
authors: Yan
authors: Y
authors: Zhou
authors: Northern Institute for Cancer Research, Newcastle University, Newcastle-upon-Tyne, UK.
authors: Craig N
authors: CN
authors: Robson
authors: Institute of Genetic Medicine, Newcastle University, Newcastle-upon-Tyne, UK.
authors: David J
authors: DJ
authors: Elliott
authors: Department of Molecular Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors: Johan
authors: J
authors: Lindberg
authors: Institute of Cancer Sciences, University of Glasgow, Glasgow, UK.|Cancer Research UK Beatson Institute, Glasgow, UK.
authors: Hing Y
authors: HY
authors: Leung
authors: Institute of Cancer Sciences, University of Glasgow, Glasgow, UK.
authors: Prabhakar
authors: P
authors: Rajan
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D017398:Alternative Splicing / Q000235:genetics*; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005091:Exons / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008954:Models, Biological; D011471:Prostatic Neoplasms / Q000235:genetics; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011944:Receptors, Androgen / Q000737:chemistry / Q000235:genetics*; D014158:Transcription, Genetic; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics / Q000378:metabolism
chemical_list: C410798:AR protein, human; D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; C489559:KHDRBS1 protein, human; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011944:Receptors, Androgen; C105156:UBE2C protein, human; D044763:Ubiquitin-Conjugating Enzymes