Nuclear targeting of the cauliflower mosaic virus (CaMV) genomeThis review is one of a selection of papers published in the Special Issue on Plant Cell Biology.

2006 ◽  
Vol 84 (4) ◽  
pp. 565-571
Author(s):  
Julie Champagne ◽  
Denis Leclerc
Keyword(s):  
Mosaic Virus ◽  
Nuclear Localization ◽  
Nuclear Localization Signal ◽  
Cell Biology ◽  
Plant Viruses ◽  
Cauliflower Mosaic Virus ◽  
Nuclear Pore ◽  
Regulatory Sequences ◽  
Nuclear Targeting ◽  
Localization Signal

The delivery of the double-stranded DNA viral genome into the nucleus is a critical step for the type member of Caulimoviridae, cauliflower mosaic virus (CaMV). The nucleocapsid (NC) of CaMV is directly involved in this process. A nuclear localization signal located at the N-terminus of the NC was shown to be exposed at the surface of the virion. This nuclear localization signal appears to be important to direct the virus to the nuclear pore complex. The nuclear targeting of the NC needs to be tightly regulated because the process of virus assembly, which also involves the viral NC, occurs in the cytosol. It is now accepted that the N- and C-terminal extensions of the viral NC precursor are efficient regulatory sequences that determine the localization of the viral NC in infected leaves. Proteolytic maturation and phosphorylation of the N- and C-terminal extensions are also important in the regulation of this process. Despite these recent discoveries, the transport of CaMV toward and into the nucleus during early events in the infection cycle remains unclear. In this review, we summarize recent advances that explain the mechanisms of targeting of the CaMV genome to the nucleus and extract from other related animal and plant viruses mechanisms that could hint at the possible strategies used by CaMV to enter the nucleus.

scholarly journals Nuclear Targeting of the Cauliflower Mosaic Virus Coat Protein

1999 ◽  
Vol 73 (1) ◽  
pp. 553-560 ◽  
Author(s):  
Denis Leclerc ◽  
Yvan Chapdelaine ◽  
Thomas Hohn
Keyword(s):  
Coat Protein ◽  
Mosaic Virus ◽  
Nuclear Localization ◽  
Virus Assembly ◽  
Cauliflower Mosaic Virus ◽  
Nuclear Targeting ◽  
Reading Frame ◽  
Localization Signal ◽  
Viral Coat ◽  
Virus Coat

ABSTRACT The entry of the viral genomic DNA of cauliflower mosaic virus into the nucleus is a critical step of viral infection. We have shown by transient expression in plant protoplasts that the viral coat protein (CP), which is processed from the product of open reading frame IV, contains an N-terminal nuclear localization signal (NLS). The NLS is exposed on the surface of the virion and is thus available for interaction with a putative NLS receptor. Phosphorylation of the matured CP did not influence the nuclear localization of the protein but improved protein stability. Mutation of the NLS completely abolished viral infectivity, thus indicating its importance in the virus life cycle. The NLS seems to be regulated by the N terminus of the precapsid, which inhibits its nuclear targeting. This regulation could be important in allowing virus assembly in the cytoplasm.

scholarly journals Regulated nuclear targeting of cauliflower mosaic virus

2002 ◽  
Vol 83 (7) ◽  
pp. 1783-1790 ◽  
Author(s):  
Aletta Karsies ◽  
Thomas Merkle ◽  
Boris Szurek ◽  
Ulla Bonas ◽  
Thomas Hohn ◽  
...  
Keyword(s):  
Mosaic Virus ◽  
Control Mechanism ◽  
Virus Assembly ◽  
Cauliflower Mosaic Virus ◽  
Nuclear Pore ◽  
Nuclear Targeting ◽  
Virus Particles ◽  
Importin Α ◽  
Localization Signal ◽  
Mature Virus

The mature cauliflower mosaic virus (CaMV) capsid protein (CP), if expressed in the absence of other viral proteins, is transported into the plant cell nucleus by the action of a nuclear localization signal (NLS) close to the N terminus. In contrast, virus particles do not enter the nucleus, but dock at the nuclear membrane, a process inhibited by anti-NLS antibodies or by GTPγS, and apparently mediated by interaction of CP with host importin α. The very acidic N-terminal extension of the viral CP precursor inhibits nuclear targeting of the protein and hence the precursor is localized in the cytoplasm. We hypothesize that this provides a control mechanism which ensures that the CP precursor is used for virus assembly in the cytoplasm and that only mature virus particles reach the nuclear pore.

scholarly journals Coordinate Nuclear Targeting of the FANCD2 and FANCI Proteins via a FANCD2 Nuclear Localization Signal

PLoS ONE ◽  
2013 ◽  
Vol 8 (11) ◽  
pp. e81387 ◽  
Author(s):  
Rebecca A. Boisvert ◽  
Meghan A. Rego ◽  
Paul A. Azzinaro ◽  
Maurizio Mauro ◽  
Niall G. Howlett
Keyword(s):  
Nuclear Localization ◽  
Nuclear Localization Signal ◽  
Nuclear Targeting ◽  
Localization Signal

scholarly journals SUMO-1 Modification and Its Role in Targeting the Ran GTPase-activating Protein, RanGAP1, to the Nuclear Pore Complex

1998 ◽  
Vol 140 (3) ◽  
pp. 499-509 ◽  
Author(s):  
Michael J. Matunis ◽  
Jian Wu ◽  
Günter Blobel
Keyword(s):  
Nuclear Localization ◽  
Nuclear Localization Signal ◽  
Nuclear Export ◽  
Nuclear Export Signal ◽  
Nucleocytoplasmic Transport ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Gtpase Activating Protein ◽  
Terminal Domain ◽  
Localization Signal

RanGAP1 is the GTPase-activating protein for Ran, a small ras-like GTPase involved in regulating nucleocytoplasmic transport. In vertebrates, RanGAP1 is present in two forms: one that is cytoplasmic, and another that is concentrated at the cytoplasmic fibers of nuclear pore complexes (NPCs). The NPC-associated form of RanGAP1 is covalently modified by the small ubiquitin-like protein, SUMO-1, and we have recently proposed that SUMO-1 modification functions to target RanGAP1 to the NPC. Here, we identify the domain of RanGAP1 that specifies SUMO-1 modification and demonstrate that mutations in this domain that inhibit modification also inhibit targeting to the NPC. Targeting of a heterologous protein to the NPC depended on determinants specifying SUMO-1 modification and also on additional determinants in the COOH-terminal domain of RanGAP1. SUMO-1 modification and these additional determinants were found to specify interaction between the COOH-terminal domain of RanGAP1 and a region of the nucleoporin, Nup358, between Ran-binding domains three and four. Together, these findings indicate that SUMO-1 modification targets RanGAP1 to the NPC by exposing, or creating, a Nup358 binding site in the COOH-terminal domain of RanGAP1. Surprisingly, the COOH-terminal domain of RanGAP1 was also found to harbor a nuclear localization signal. This nuclear localization signal, and the presence of nine leucine-rich nuclear export signal motifs, suggests that RanGAP1 may shuttle between the nucleus and the cytoplasm.

Nuclear import of glycoconjugates is distinct from the classical NLS pathway

1995 ◽  
Vol 108 (4) ◽  
pp. 1325-1332 ◽  
Author(s):  
E. Duverger ◽  
C. Pellerin-Mendes ◽  
R. Mayer ◽  
A.C. Roche ◽  
M. Monsigny
Keyword(s):  
Nuclear Localization ◽  
Nuclear Import ◽  
Nuclear Localization Signal ◽  
Peptide Sequence ◽  
Nuclear Pore ◽  
Dependent Manner ◽  
Permeabilized Cells ◽  
Localization Signal ◽  
Energy Dependent ◽  
Cytosolic Factors

The nuclear import of many proteins depends on a short peptide sequence called the nuclear localization signal. However, glycosylated proteins, which lack such a nuclear localization signal, upon their injection into the cytosol by electroporation, enter the nucleus in a sugar-dependent manner. This paper brings new insights on the mechanism of this process, based on a study of neoglycoprotein nuclear uptake by digitonin-permeabilized cells. The nuclear import of neoglycoproteins is energy dependent: it does not occur when cells are maintained at 4 degrees C or when cells are ATP-depleted by treatment with apyrase. The nuclear import of neoglycoproteins occurs through the nuclear pore: it is inhibited by preincubation of cells with wheat germ agglutinin, a lectin which binds the nuclear pore glycoproteins and blocks the translocation step of nuclear localization signal bearing proteins through the nuclear pore. Furthermore, the nuclear import of neoglycoproteins does not use the pathway of nuclear localization signal bearing proteins: nuclear import of nuclear localization signal bearing proteins depends on cytosolic factors and is inhibited by treatment of cells with N-ethylmaleimide, while the nuclear import of neoglycoproteins neither requires added cytosolic factors nor is sensitive to alkylation by N-ethylmaleimide. In addition, upon incubation in the presence of a large excess of nuclear localization signal bearing protein, the nuclear import of neoglycoproteins is not inhibited.

Nuclear Localization Signal(s) Required for Nuclear Targeting of the Maize Regulatory Protein Opaque-2

1992 ◽  
Vol 4 (10) ◽  
pp. 1213
Author(s):  
Marguerite J. Varagona ◽  
Robert J. Schmidt ◽  
Natasha V. Raikhel
Keyword(s):  
Nuclear Localization ◽  
Nuclear Localization Signal ◽  
Regulatory Protein ◽  
Nuclear Targeting ◽  
Localization Signal

Nuclear import of protein kinase C occurs by a mechanism distinct from the mechanism used by proteins with a classical nuclear localization signal

1998 ◽  
Vol 111 (13) ◽  
pp. 1823-1830 ◽  
Author(s):  
D. Schmalz ◽  
F. Hucho ◽  
K. Buchner
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Nuclear Localization ◽  
Phorbol Ester ◽  
Nuclear Import ◽  
Nuclear Localization Signal ◽  
Nuclear Pore ◽  
Kinase C ◽  
Localization Signal ◽  
Protein Kinase C Alpha

Protein kinase C does not have any known nuclear localization signal but, nevertheless, is redistributed from the cytoplasm to the nucleus upon various stimuli. In NIH 3T3 fibroblasts stimulation with phorbol ester leads to a translocation of protein kinase C alpha to the plasma membrane and into the cell nucleus. We compared the mechanism of protein kinase C alpha's transport into the nucleus with the transport mechanism of a protein with a classical nuclear localization signal at several steps. To this end, we co-microinjected fluorescently labeled bovine serum albumin to which a nuclear localization signal peptide was coupled, together with substances interfering with conventional nuclear protein import. Thereafter, the distribution of both the nuclear localization signal-bearing reporter protein and protein kinase C alpha was analyzed in the same cells. We can show that, in contrast to the nuclear localization signal-dependent transport, the phorbol ester-induced transport of protein kinase C alpha is not affected by microinjection of antibodies against the nuclear import factor p97/importin/karyopherin beta or microinjection of non-hydrolyzable GTP-analogs. This suggests that nuclear import of protein kinase C alpha is independent of p97/importin/karyopherin beta and independent of GTP. At the nuclear pore there are differences between the mechanisms too, since nuclear transport of protein kinase C alpha cannot be inhibited by wheat germ agglutinin or an antibody against nuclear pore complex proteins. Together these findings demonstrate that the nuclear import of protein kinase C alpha occurs by a mechanism distinct from the one used by classical nuclear localization signal-bearing proteins at several stages.

scholarly journals Karyopherins regulate nuclear pore complex barrier and transport function

2017 ◽  
Vol 216 (11) ◽  
pp. 3609-3624 ◽  
Author(s):  
Larisa E. Kapinos ◽  
Binlu Huang ◽  
Chantal Rencurel ◽  
Roderick Y.H. Lim
Keyword(s):  
Nuclear Localization ◽  
Nuclear Pore Complex ◽  
Nuclear Localization Signal ◽  
Barrier Function ◽  
Nucleocytoplasmic Transport ◽  
Nuclear Pore ◽  
Dependent Manner ◽  
Transport Function ◽  
Guanosine Triphosphate ◽  
Localization Signal

Nucleocytoplasmic transport is sustained by karyopherins (Kaps) and a Ran guanosine triphosphate (RanGTP) gradient that imports nuclear localization signal (NLS)–specific cargoes (NLS-cargoes) into the nucleus. However, how nuclear pore complex (NPC) barrier selectivity, Kap traffic, and NLS-cargo release are systematically linked and simultaneously regulated remains incoherent. In this study, we show that Kapα facilitates Kapβ1 turnover and occupancy at the NPC in a RanGTP-dependent manner that is directly coupled to NLS-cargo release and NPC barrier function. This is underpinned by the binding affinity of Kapβ1 to phenylalanine–glycine nucleoporins (FG Nups), which is comparable with RanGTP·Kapβ1, but stronger for Kapα·Kapβ1. On this basis, RanGTP is ineffective at releasing standalone Kapβ1 from NPCs. Depleting Kapα·Kapβ1 by RanGTP further abrogates NPC barrier function, whereas adding back Kapβ1 rescues it while Kapβ1 turnover softens it. Therefore, the FG Nups are necessary but insufficient for NPC barrier function. We conclude that Kaps constitute integral constituents of the NPC whose barrier, transport, and cargo release functionalities establish a continuum under a mechanism of Kap-centric control.

scholarly journals The Novel Nuclear Targeting and BFRF1-Interacting Domains of BFLF2 Are Essential for Efficient Epstein-Barr Virus Virion Release

2019 ◽  
Vol 94 (3) ◽  
Author(s):  
Yu-Ching Dai ◽  
Yen-Tzu Liao ◽  
Yi-Ting Juan ◽  
Yi-Ying Cheng ◽  
Mei-Tzu Su ◽  
...  
Keyword(s):  
Amino Acids ◽  
Nuclear Localization ◽  
Nuclear Localization Signal ◽  
Epstein Barr Virus ◽  
The Novel ◽  
Nuclear Targeting ◽  
Barr Virus ◽  
Nuclear Egress ◽  
Localization Signal ◽  
Epstein Barr

ABSTRACT Epstein-Barr virus (EBV) genomic DNA is replicated and packaged into procapsids in the nucleus to form nucleocapsids, which are then transported into the cytoplasm for tegumentation and final maturation. The process is facilitated by the coordination of the viral nuclear egress complex (NEC), which consists of BFLF2 and BFRF1. By expression alone, BFLF2 is distributed mainly in the nucleus. However, it colocalizes with BFRF1 at the nuclear rim and in cytoplasmic nuclear envelope-derived vesicles in coexpressing cells, suggesting temporal control of the interaction between BFLF2 and BFRF1 is critical for their proper function. The N-terminal sequence of BFLF2 is less conserved than that of alpha- and betaherpesvirus homologs. Here, we found that BFLF2 amino acids (aa) 2 to 102 are required for both nuclear targeting and its interaction with BFRF1. Coimmunoprecipitation and confocal analysis indicated that aa 82 to 106 of BFLF2 are important for its interaction with BFRF1. Three crucial amino acids (R47, K50, and R52) and several noncontinuous arginine and histidine residues within aa 59 to 80 function together as a noncanonical nuclear localization signal (NLS), which can be transferred onto yellow fluorescent protein (YFP)-LacZ for nuclear targeting in an importin β-dependent manner. Virion secretion is defective in 293 cells harboring a BFLF2 knockout EBV bacmid upon lytic induction and is restored by trans-complementation of wild-type BFLF2, but not NLS or BFRF1-interacting defective mutants. In addition, multiple domains of BFRF1 were found to bind BFLF2, suggesting multiple contact regions within BFRF1 and BFLF2 are required for proper nuclear egress of EBV nucleocapsids. IMPORTANCE Although Epstein-Barr virus (EBV) BFRF1 and BFLF2 are homologs of conserved viral nuclear egress complex (NEC) in all human herpesviruses, unique amino acid sequences and functions were identified in both proteins. In this study, the nuclear targeting and BFRF1-interacting domains were found within the N terminus of BFLF2. We showed that amino acids (aa) 82 to 106 are the major region required for BFLF2 to interact with BFRF1. However, the coimmunoprecipitation (Co-IP) data and glutathione transferase (GST) pulldown experiments revealed that multiple regions of both proteins contribute to reciprocal interactions. Different from the canonical nuclear localization signal (NLS) in other herpes viral homologs, BFLF2 contains a novel importin-dependent nuclear localization signal, including R47, K50, and R52 and several neighboring discontinuous arginine and histidine residues. Using a bacmid complementation system, we show that both the nuclear targeting and the novel nuclear localization signal within aa 82 to 106 of BFLF2 are required for virion secretion.

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