title: Insights into nuclear organization in plants as revealed by the dynamic distribution of Arabidopsis SR splicing factors.
abstract: Serine/arginine-rich (SR) proteins are splicing regulators that share a modular structure consisting of one or two N-terminal RNA recognition motif domains and a C-terminal RS-rich domain. We investigated the dynamic localization of the Arabidopsis thaliana SR protein RSZp22, which, as we showed previously, distributes in predominant speckle-like structures and in the nucleolus. To determine the role of RSZp22 diverse domains in its nucleolar distribution, we investigated the subnuclear localization of domain-deleted mutant proteins. Our results suggest that the nucleolar localization of RSZp22 does not depend on a single targeting signal but likely involves different domains/motifs. Photobleaching experiments demonstrated the unrestricted dynamics of RSZp22 between nuclear compartments. Selective inhibitor experiments of ongoing cellular phosphorylation influenced the rates of exchange of RSZp22 between the different nuclear territories, indicating that SR protein mobility is dependent on the phosphorylation state of the cell. Furthermore, based on a leptomycin B- and fluorescence loss in photobleaching-based sensitive assay, we suggest that RSZp22 is a nucleocytoplasmic shuttling protein. Finally, with electron microscopy, we confirmed that RSp31, a plant-specific SR protein, is dynamically distributed in nucleolar cap-like structures upon phosphorylation inhibition. Our findings emphasize the high mobility of Arabidopsis SR splicing factors and provide insights into the dynamic relationships between the different nuclear compartments.
authors.affiliation: Laboratory of Plant Cell and Molecular Biology, Department of Life Sciences, Institute of Botany, University of Liège, B-4000 Liège, Belgium.
authors.forename: Vinciane
authors.initials: V
authors.lastname: Tillemans
authors.forename: Isabelle
authors.initials: I
authors.lastname: Leponce
authors.forename: Glwadys
authors.initials: G
authors.lastname: Rausin
authors.forename: Laurence
authors.initials: L
authors.lastname: Dispa
authors.forename: Patrick
authors.initials: P
authors.lastname: Motte
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D002451:Cell Compartmentation / Q000187:drug effects; D002466:Cell Nucleolus / Q000187:drug effects / Q000648:ultrastructure; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D036681:Fluorescence Recovery After Photobleaching; D007399:Interphase / Q000187:drug effects; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins / Q000378:metabolism; D010770:Phosphotransferases / Q000378:metabolism; D018515:Plant Leaves / Q000166:cytology / Q000187:drug effects; D017434:Protein Structure, Tertiary / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D000068103:Serine-Arginine Splicing Factors
chemical_list: D029681:Arabidopsis Proteins; D005231:Fatty Acids, Unsaturated; D050505:Mutant Proteins; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D016601:RNA-Binding Proteins; C119299:RSZ protein, Arabidopsis; C103793:RSp31 protein, Arabidopsis; D000068103:Serine-Arginine Splicing Factors; D010770:Phosphotransferases; C038753:leptomycin B