title: Phosphorylated Ser/Arg-rich proteins: limiting factors in the assembly of 200S large nuclear ribonucleoprotein particles.
abstract: We have previously shown that specific nuclear pre-mRNA transcripts and their splicing products, as well as the general population of nuclear poly(A)+ RNA, are packaged in large nuclear ribonucleoprotein (InRNP) particles that sediment at the 200S region in sucrose gradients. The InRNP particles contain all uridine-rich small nuclear ribonucleoprotein complexes required for pre-mRNA splicing, as well as protein splicing factors. In this paper we show that all of the phosphorylated, mAb 104 detectable, Ser/Arg-rich essential splicing factors (SR proteins) in the nucleoplasm are integral components of the InRNP particles, whereas only part of the essential splicing factor U2AF65 (U2 snRNP auxiliary factor) and the polypyrimidine tract binding protein (PTB) are associated with these particles. This finding suggests a limiting role for SR proteins in the assembly of the InRNP particles. We further show that the structural integrity of InRNP particles is sensitive to variations in the phosphorylation levels of the SR proteins.
authors.affiliation: Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: S
authors.initials: S
authors.lastname: Yitzhaki
authors.forename: E
authors.initials: E
authors.lastname: Miriami
authors.forename: R
authors.initials: R
authors.lastname: Sperling
authors.forename: J
authors.initials: J
authors.lastname: Sperling
mesh_terms: D000818:Animals; D001221:Aspartate Carbamoyltransferase / Q000235:genetics; D002467:Cell Nucleus / Q000378:metabolism; D006224:Cricetinae; D004268:DNA-Binding Proteins / Q000032:analysis*; D004080:Dihydroorotase / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008025:Ligases / Q000235:genetics; D009687:Nuclear Proteins / Q000737:chemistry*; D010750:Phosphoproteins / Q000032:analysis*; D010766:Phosphorylation; D038941:Polypyrimidine Tract-Binding Protein; D011233:Precipitin Tests; D011485:Protein Binding; D012326:RNA Splicing; D016601:RNA-Binding Proteins / Q000032:analysis*; D012261:Ribonucleoproteins / Q000032:analysis* / Q000737:chemistry*; D017411:Ribonucleoproteins, Small Nuclear / Q000378:metabolism; D000072668:Splicing Factor U2AF
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D017411:Ribonucleoproteins, Small Nuclear; D000072668:Splicing Factor U2AF; C000607494:U2AF2 protein, human; D038941:Polypyrimidine Tract-Binding Protein; D001221:Aspartate Carbamoyltransferase; D004080:Dihydroorotase; D008025:Ligases