title: Consensus PP1 binding motifs regulate transcriptional corepression and alternative RNA splicing activities of the steroid receptor coregulators, p54nrb and PSF.
abstract: Originally identified as essential pre-mRNA splicing factors, non-POU-domain-containing, octamer binding protein (p54nrb) and PTB-associated RNA splicing factor (PSF) are also steroid receptor corepressors. The mechanisms by which p54nrb and PSF regulate gene transcription remain unclear. Both p54nrb and PSF contain protein phosphatase 1 (PP1) consensus binding RVxF motifs, suggesting that PP1 may regulate phosphorylation status of p54nrb and PSF and thus their function in gene transcription. In this report, we demonstrated that PP1 forms a protein complex with both p54nrb and PSF. PP1 interacts directly with the RVxF motif only in p54nrb, but not in PSF. Association with PP1 results in dephosphorylation of both p54nrb and PSF in vivo and the loss of their transcriptional corepressor activities. Using the CD44 minigene as a reporter, we showed that PP1 regulates p54nrb and PSF alternative splicing activities that determine exon skipping vs. inclusion in the final mature RNA for translation. In addition, changes in transcriptional corepression and RNA splicing activities of p54nrb and PSF are correlated with alterations in protein interactions of p54nrb and PSF with transcriptional corepressors such as Sin3A and histone deacetylase 1, and RNA splicing factors such as U1A and U2AF. Furthermore, we demonstrated a novel function of the RVxF motif within PSF that enhances its corepression and RNA splicing activities independent of PP1. We conclude that the RVxF motifs play an important role in controlling the multifunctional properties of p54nrb and PSF in the regulation of gene transcription.
authors.affiliation: Vancouver Prostate Center, Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Liangliang
authors.initials: L
authors.lastname: Liu
authors.forename: Ning
authors.initials: N
authors.lastname: Xie
authors.forename: Paul
authors.initials: P
authors.lastname: Rennie
authors.forename: John R G
authors.initials: JR
authors.lastname: Challis
authors.forename: Martin
authors.initials: M
authors.lastname: Gleave
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Lye
authors.forename: Xuesen
authors.initials: X
authors.lastname: Dong
mesh_terms: D017398:Alternative Splicing; D001665:Binding Sites; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D018960:Hyaluronan Receptors / Q000235:genetics / Q000378:metabolism; D047468:Immunoprecipitation; D034521:Nuclear Matrix-Associated Proteins / Q000378:metabolism*; D050810:Octamer Transcription Factors / Q000378:metabolism*; D000072670:PTB-Associated Splicing Factor; D010766:Phosphorylation; D011485:Protein Binding; D054645:Protein Phosphatase 1 / Q000737:chemistry* / Q000378:metabolism; D021381:Protein Transport; D016601:RNA-Binding Proteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; D018960:Hyaluronan Receptors; C083214:NONO protein, human; D034521:Nuclear Matrix-Associated Proteins; D050810:Octamer Transcription Factors; D000072670:PTB-Associated Splicing Factor; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D054645:Protein Phosphatase 1