title: Alternative RNA splicing complexes containing the scaffold attachment factor SAFB2.
abstract: The scaffold attachment factor SAFB1 and its recently discovered homologue SAFB2 might provide an important link between pre-mRNA splicing, intracellular signalling and transcription. Using novel mono-specific antisera, we found endogenous SAFB2 protein has a different spatial distribution from SAFB1 within the nucleus where it is found in much larger nuclear complexes (up to 670 kDa in size), and a distinct pattern of expression in adult human testis. By contrast, SAFB1 protein predominantly exists either as smaller complexes or as a monomeric protein. Our results suggest stable core complexes containing components comprised of SAFB1, SAFB2 and the RNA binding proteins Sam68 and hnRNPG exist in parallel with free SAFB1 protein. We found that SAFB2 protein, like SAFB1, acts as a negative regulator of a tra2beta variable exon. Despite showing an involvement in splicing, we detected no stable interaction between SAFB proteins and SR or SR-related splicing regulators, although these were also found in stable higher molecular mass complexes. Each of the detected alternative splicing regulator complexes exists independently of intact nucleic acids, suggesting they might be pre-assembled and recruited to nascent transcripts as modules to facilitate alternative splicing, and/or they represent nuclear storage compartments from which active proteins are recruited.
authors.affiliation: Institute of Human Genetics, University of Newcastle, International Centre for Life, Central Parkway, Newcastle, NE1 3BZ, UK.
authors.forename: Kate A
authors.initials: KA
authors.lastname: Sergeant
authors.forename: Cyril F
authors.initials: CF
authors.lastname: Bourgeois
authors.forename: Caroline
authors.initials: C
authors.lastname: Dalgliesh
authors.forename: Julian P
authors.initials: JP
authors.lastname: Venables
authors.forename: James
authors.initials: J
authors.lastname: Stevenin
authors.forename: David J
authors.initials: DJ
authors.lastname: Elliott
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D017398:Alternative Splicing; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D006367:HeLa Cells; D006801:Humans; D008297:Male; D036961:Matrix Attachment Region Binding Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D034521:Nuclear Matrix-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012319:RNA Polymerase II / Q000737:chemistry / Q000378:metabolism; D012326:RNA Splicing; D016601:RNA-Binding Proteins / Q000378:metabolism; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012708:Sertoli Cells / Q000166:cytology / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; C489559:KHDRBS1 protein, human; D036961:Matrix Attachment Region Binding Proteins; D034521:Nuclear Matrix-Associated Proteins; D016601:RNA-Binding Proteins; D011960:Receptors, Estrogen; D011993:Recombinant Fusion Proteins; C486369:SAFB2 protein, human; D012319:RNA Polymerase II