title: Co-localisation studies of Arabidopsis SR splicing factors reveal different types of speckles in plant cell nuclei.
abstract: SR proteins are multidomain splicing factors which are important for spliceosome assembly and for regulation of alternative splicing. In mammalian nuclei these proteins localise to speckles from where they are recruited to transcription sites. By using fluorescent protein fusion technology and different experimental approaches it has been shown that Arabidopsis SR proteins, in addition to diffuse nucleoplasmic staining, localise into an irregular nucleoplasmic network resembling speckles in mammalian cells. As Arabidopsis SR proteins fall into seven conserved sub-families we investigated co-localisation of members of the different sub-families in transiently transformed tobacco protoplast. Here we demonstrate the new finding that members of different SR protein sub-families localise into distinct populations of nuclear speckles with no, partial or complete co-localisation. This is particularly interesting as we also show that these proteins do interact in a yeast two-hybrid assay as well as in pull-down and in co-immunopreciptiation assays. Our data raise the interesting possibility that SR proteins are partitioned into distinct populations of nuclear speckles to allow a more specific recruitment to the transcription/pre-mRNA processing sites of particular genes depending on cell type and developmental stage.
authors.affiliation: Max F. Perutz Laboratories, Medical University of Vienna, Department of Medical Biochemistry, Vienna, Austria. zdravko.lorkovic@meduniwien.ac.at
authors.forename: Zdravko J
authors.initials: ZJ
authors.lastname: Lorković
authors.forename: Julia
authors.initials: J
authors.lastname: Hilscher
authors.forename: Andrea
authors.initials: A
authors.lastname: Barta
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D011523:Protoplasts / Q000166:cytology / Q000378:metabolism; D012326:RNA Splicing; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000235:genetics / Q000378:metabolism; D000068103:Serine-Arginine Splicing Factors; D014026:Nicotiana / Q000166:cytology / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; C469364:At2g37340 protein, Arabidopsis; D016601:RNA-Binding Proteins; C119299:RSZ protein, Arabidopsis; D011993:Recombinant Fusion Proteins; D017412:Ribonucleoprotein, U1 Small Nuclear; D000068103:Serine-Arginine Splicing Factors