title: New proteins related to the Ser-Arg family of splicing factors.
abstract: A family of six highly conserved proteins that contain domains rich in alternating serine/arginine residues (SR proteins) function in the regulation of splice site selection and are required for splicing. Using a selective precipitation method, more than 35 proteins were detected in nuclear extracts of HeLa cells that co-fractionate with the defined SR family. Many of these proteins were recognized by three monoclonal antibodies that bind to distinct phosphoepitopes on SR proteins. Two of these SR-related proteins were identified as the nuclear matrix antigens B1C8 and B4A11, which previously have been implicated in splicing. A subset of SR proteins, in their phosphorylated state, are associated with spliceosome complexes through both steps of the splicing reaction, remaining preferentially bound to complexes containing the exon-product. In contrast, other SR-related proteins appear to remain specifically associated with the intron-Iariat complex. The results indicate the existence of a potentially large group of SR-related proteins, and also suggest possible additional functions of SR proteins at a post-splicing level.
mesh_terms: D000911:Antibodies, Monoclonal; D000941:Antigens / Q000737:chemistry / Q000302:isolation & purification; D034961:Antigens, Nuclear; D001120:Arginine; D011232:Chemical Precipitation; D000939:Epitopes; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D009687:Nuclear Proteins / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification; D010766:Phosphorylation; D012326:RNA Splicing; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D012694:Serine
chemical_list: D000911:Antibodies, Monoclonal; D000941:Antigens; D034961:Antigens, Nuclear; D000939:Epitopes; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; D012694:Serine; D001120:Arginine