title: A novel nucleocytoplasmic traffic GTPase identified as a functional target of the bipartite geminivirus nuclear shuttle protein.
abstract: In contrast to the accumulated data on nuclear transport mechanisms of macromolecules, little is known concerning the regulated release of nuclear-exported complexes and their subsequent trans-cytoplasmic movement. The bipartite begomovirus nuclear shuttle protein (NSP) facilitates the nuclear export of viral DNA and cooperates with the movement protein (MP) to transport viral DNA across the plant cell wall. Here, we identified a cellular NSP-interacting GTPase (NIG) with biochemical properties consistent with a nucleocytoplasmic transport role. We show that NIG is a cytosolic GTP-binding protein that accumulates around the nuclear envelope and possesses intrinsic GTPase activity. NIG interacts with NSP in vitro and in vivo (under transient expression), and redirects the viral protein from the nucleus to the cytoplasm. We propose that NIG acts as a positive contributor to geminivirus infection by modulating NSP nucleocytoplasmic shuttling and hence facilitating MP-NSP interaction in the cortical cytoplasm. In support of this, overexpression of NIG in Arabidopsis enhances susceptibility to geminivirus infection. In addition to highlighting the relevance of NIG as a cellular co-factor for NSP function, our findings also have implications for general nucleocytoplasmic trafficking of cellular macromolecules.
authors.affiliation: Departamento de Bioquímica e Biologia Molecular, Vicosa, Minas Gerais, Brazil.
authors.forename: Claudine M
authors.initials: CM
authors.lastname: Carvalho
authors.forename: Mariana R
authors.initials: MR
authors.lastname: Fontenelle
authors.forename: Lílian H
authors.initials: LH
authors.lastname: Florentino
authors.forename: Anésia A
authors.initials: AA
authors.lastname: Santos
authors.forename: Francisco M
authors.initials: FM
authors.lastname: Zerbini
authors.forename: Elizabeth P B
authors.initials: EP
authors.lastname: Fontes
mesh_terms: D021581:Active Transport, Cell Nucleus; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000821:virology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D053839:Begomovirus / Q000235:genetics* / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D004279:DNA, Viral / Q000235:genetics; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D018613:Microscopy, Confocal; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010935:Plant Diseases / Q000821:virology; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D053830:Plant Viral Movement Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D010957:Plasmids; D011523:Protoplasts / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D004279:DNA, Viral; D009687:Nuclear Proteins; D053830:Plant Viral Movement Proteins; D018749:RNA, Plant; D020558:GTP Phosphohydrolases