title: Splicing and transcription-associated proteins PSF and p54nrb/nonO bind to the RNA polymerase II CTD.
abstract: The carboxyl-terminal domain (CTD) of the largest subunit of eukaryotic RNA polymerase II (pol II) plays an important role in promoting steps of pre-mRNA processing. To identify proteins in human cells that bind to the CTD and that could mediate its functions in pre-mRNA processing, we used the mouse CTD expressed in bacterial cells in affinity chromatography experiments. Two proteins present in HeLa cell extract, the splicing and transcription-associated factors, PSF and p54nrb/NonO, bound specifically and could be purified to virtual homogeneity by chromatography on immobilized CTD matrices. Both hypo- and hyperphosphorylated CTD matrices bound these proteins with similar selectivity. PSF and p54nrb/NonO also copurified with a holoenzyme form of pol II containing hypophosphorylated CTD and could be coimmunoprecipitated with antibodies specific for this and the hyperphosphorylated form of pol II. That PSF and p54nrb/NonO promoted the binding of RNA to immobilized CTD matrices suggested these proteins can interact with the CTD and RNA simultaneously. PSF and p54nrb/NonO may therefore provide a direct physical link between the pol II CTD and pre-mRNA processing components, at both the initiation and elongation phases of transcription.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D004268:DNA-Binding Proteins; D006367:HeLa Cells; D020035:Holoenzymes / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D008969:Molecular Sequence Data; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D050810:Octamer Transcription Factors; D000072670:PTB-Associated Splicing Factor; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D012319:RNA Polymerase II / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012322:RNA Precursors / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012326:RNA Splicing; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; D020035:Holoenzymes; C083214:NONO protein, human; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins; D050810:Octamer Transcription Factors; D000072670:PTB-Associated Splicing Factor; D012322:RNA Precursors; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D012319:RNA Polymerase II