scholarly journals Ciliary entry of KIF17 is dependent on its binding to the IFT-B complex via IFT46–IFT56 as well as on its nuclear localization signal

2017 ◽  
Vol 28 (5) ◽  
pp. 624-633 ◽  
Author(s):  
Teruki Funabashi ◽  
Yohei Katoh ◽  
Saki Michisaka ◽  
Masaya Terada ◽  
Maho Sugawa ◽  
...  
Keyword(s):  
Nuclear Localization ◽  
Protein Trafficking ◽  
Nuclear Localization Signal ◽  
Mammalian Cells ◽  
Permeability Barrier ◽  
Extracellular Signals ◽  
Ciliary Protein ◽  
Importin Α ◽  
Localization Signal

Cilia function as cellular antennae to sense and transduce extracellular signals. A number of proteins are specifically localized in cilia. Anterograde and retrograde ciliary protein trafficking are mediated by the IFT-B and IFT-A complexes in concert with kinesin-2 and dynein-2 motors, respectively. However, the role of KIF17, a homodimeric kinesin-2 protein, in protein trafficking has not been fully understood in vertebrate cilia. In this study, we demonstrated, by using the visible immunoprecipitation assay, that KIF17 interacts with the IFT46–IFT56 dimer in the IFT-B complex through its C-terminal sequence located immediately upstream of the nuclear localization signal (NLS). We then showed that KIF17 reaches the ciliary tip independently of its motor domain and requires IFT-B binding for its entry into cilia rather than for its intraciliary trafficking. We further showed that KIF17 ciliary entry depends not only on its binding to IFT-B but also on its NLS, to which importin α proteins bind. Taking the results together, we conclude that in mammalian cells, KIF17 is dispensable for ciliogenesis and IFT-B trafficking but requires IFT-B, as well as its NLS, for its ciliary entry across the permeability barrier located at the ciliary base.

scholarly journals Inhibition of Human Cytomegalovirus Replication via Peptide Aptamers Directed against the Nonconventional Nuclear Localization Signal of the Essential Viral Replication Factor pUL84

2009 ◽  
Vol 83 (22) ◽  
pp. 11902-11913 ◽  
Author(s):  
Nina Kaiser ◽  
Peter Lischka ◽  
Nadine Wagenknecht ◽  
Thomas Stamminger
Keyword(s):  
Viral Replication ◽  
Human Cytomegalovirus ◽  
Nuclear Localization ◽  
Nuclear Import ◽  
Nuclear Localization Signal ◽  
Mammalian Cells ◽  
Human Fibroblasts ◽  
Peptide Aptamers ◽  
Importin Α ◽  
Localization Signal

ABSTRACT The UL84 open reading frame of human cytomegalovirus encodes an essential multifunctional regulatory protein that is thought to act in the nucleus as an initiator of lytic viral replication. Nuclear trafficking of pUL84 is facilitated by a complex nonconventional nuclear localization signal (NLS) that mediates its interaction with the cellular importin-α/β pathway. Since binding of pUL84 to importin-α proteins mechanistically differs from that of cellular proteins containing a classical NLS, we assumed that specific interference with the nuclear import of pUL84 might be possible and that this could constitute a novel principle for antiviral therapy. In order to test this hypothesis, we employed peptide aptamer technology and isolated several peptide aptamers from a randomized peptide expression library that specifically bind with high affinity to the unconventional pUL84 NLS under intracellular conditions. Coimmunoprecipitation experiments confirmed these interactions in mammalian cells, and the antiviral potential of the identified peptide aptamers was determined using three independent experimental approaches. (i) Infection experiments with a recombinant human cytomegalovirus expressing green fluorescent protein demonstrated 50 to 60% decreased viral replication in primary human fibroblasts stably expressing pUL84-specific aptamers. (ii) A 50 to 70% reduction of viral plaque formation, as well as a 70 to 90% inhibition of virus release in the presence of pUL84-specific aptamers, was observed. (iii) Immunofluorescence analyses revealed a shift from an almost exclusively nuclear pUL84 staining pattern to a nucleocytoplasmic distribution upon coexpression of the identified molecules, indicating that interference with the nuclear import of pUL84 contributes to the observed antiviral activity of the identified pUL84-binding aptamer molecules.

scholarly journals Staufen1 is imported into the nucleolus via a bipartite nuclear localization signal and several modulatory determinants

2005 ◽  
Vol 393 (1) ◽  
pp. 245-254 ◽  
Author(s):  
Catherine Martel ◽  
Paolo Macchi ◽  
Luc Furic ◽  
Michael A. Kiebler ◽  
Luc Desgroseillers
Keyword(s):  
Nuclear Localization ◽  
Nuclear Localization Signal ◽  
Nuclear Export ◽  
Mammalian Cells ◽  
Rna Binding ◽  
Binding Activity ◽  
Nuclear Trafficking ◽  
Binding Domains ◽  
Bipartite Nuclear Localization Signal ◽  
Localization Signal

Mammalian Stau1 (Staufen1), a modular protein composed of several dsRBDs (double-stranded RNA-binding domains), is probably involved in mRNA localization. Although Stau1 is mostly described in association with the rough endoplasmic reticulum and ribosomes in the cytoplasm, recent studies suggest that it may transit through the nucleus/nucleolus. Using a sensitive yeast import assay, we show that Stau1 is actively imported into the nucleus through a newly identified bipartite nuclear localization signal. As in yeast, the bipartite nuclear localization signal is necessary for Stau1 nuclear import in mammalian cells. It is also required for Stau1 nucleolar trafficking. However, Stau1 nuclear transit seems to be regulated by mechanisms that involve cytoplasmic retention and/or facilitated nuclear export. Cytoplasmic retention is mainly achieved through the action of dsRBD3, with dsRBD2 playing a supporting role in this function. Similarly, dsRBD3, but not its RNA-binding activity, is critical for Stau1 nucleolar trafficking. The function of dsRBD3 is strengthened or stabilized by the presence of dsRBD4 but prevented by the interdomain between dsRBD2 and dsRBD3. Altogether, these results suggest that Stau1 nuclear trafficking is a highly regulated process involving several determinants. The presence of Stau1 in the nucleus/nucleolus suggests that it may be involved in ribonucleoprotein formation in the nucleus and/or in other nuclear functions not necessarily related to mRNA transport.

scholarly journals Evolutionary Selection of the Nuclear Localization Signal in the Viral Nucleoprotein Leads to Host Adaptation of the Genus Orthobornavirus

Viruses ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 1291
Author(s):  
Ryo Komorizono ◽  
Yukiko Sassa ◽  
Masayuki Horie ◽  
Akiko Makino ◽  
Keizo Tomonaga
Keyword(s):  
Host Range ◽  
Nuclear Localization ◽  
Nuclear Localization Signal ◽  
Mammalian Cells ◽  
Matrix Protein ◽  
Host Adaptation ◽  
Host Cells ◽  
Viral Glycoprotein ◽  
Mammalian Cell Lines ◽  
Localization Signal

Adaptation of the viral life cycle to host cells is necessary for efficient viral infection and replication. This evolutionary process has contributed to the mechanism for determining the host range of viruses. Orthobornaviruses, members of the family Bornaviridae, are non-segmented, negative-strand RNA viruses, and several genotypes have been isolated from different vertebrate species. Previous studies revealed that some genotypes isolated from avian species can replicate in mammalian cell lines, suggesting the zoonotic potential of avian orthobornaviruses. However, the mechanism by which the host specificity of orthobornaviruses is determined has not yet been identified. In this study, we found that the infectivity of orthobornaviruses is not determined at the viral entry step, mediated by the viral glycoprotein and matrix protein. Furthermore, we demonstrated that the nuclear localization signal (NLS) sequence in the viral nucleoprotein (N) has evolved under natural selection and determines the host-specific viral polymerase activity. A chimeric mammalian orthobornavirus, which has the NLS sequence of avian orthobornavirus N, exhibited a reduced propagation efficiency in mammalian cells. Our findings indicated that nuclear transport of the viral N is a determinant of the host range of orthobornaviruses, providing insights into the evolution and host adaptation of orthobornaviruses.

scholarly journals Dual role of the adenovirus pVI C terminus as a nuclear localization signal and activator of the viral protease

2004 ◽  
Vol 85 (11) ◽  
pp. 3367-3376 ◽  
Author(s):  
K. S. Honkavuori ◽  
B. D. Pollard ◽  
M. S. Rodriguez ◽  
R. T. Hay ◽  
G. D. Kemp
Keyword(s):  
Nuclear Localization ◽  
Nuclear Localization Signal ◽  
Human Adenovirus ◽  
Dual Role ◽  
Adenovirus Infection ◽  
Heterologous Proteins ◽  
Viral Protease ◽  
C Terminus ◽  
Localization Signal

Adenain, the protease produced by adenovirus, is regulated by formation of a heterodimer with an 11 aa peptide derived from the C terminus of another adenoviral protein, pVI. Here, the role of the basic motif KRRR, which is conserved in pVI sequences from human adenovirus serotypes, was investigated. It was shown that this motif is less important than the N- or C-terminal regions in the formation of the adenain–peptide heterodimer and in the activity of the subsequent complex. This motif, however, acted as a nuclear localization signal that was capable of targeting heterologous proteins to the nucleus, resulting in a distinctive intranuclear distribution consisting of discrete foci, which is similar to that found for pVI during adenovirus infection.

scholarly journals CRM1-mediated Recycling of Snurportin 1 to the Cytoplasm

1999 ◽  
Vol 145 (2) ◽  
pp. 255-264 ◽  
Author(s):  
Efrosyni Paraskeva ◽  
Elisa Izaurralde ◽  
F. Ralf Bischoff ◽  
Jochen Huber ◽  
Ulrike Kutay ◽  
...  
Keyword(s):  
Nuclear Localization ◽  
Nuclear Localization Signal ◽  
Nuclear Export ◽  
Activation Domain ◽  
Large Domain ◽  
High Affinity ◽  
Importin Α ◽  
Localization Signal ◽  
Major Mediator ◽  
Rev Protein

Importin β is a major mediator of import into the cell nucleus. Importin β binds cargo molecules either directly or via two types of adapter molecules, importin α, for import of proteins with a classical nuclear localization signal (NLS), or snurportin 1, for import of m3G-capped U snRNPs. Both adapters have an NH2-terminal importin β–binding domain for binding to, and import by, importin β, and both need to be returned to the cytoplasm after having delivered their cargoes to the nucleus. We have shown previously that CAS mediates export of importin α. Here we show that snurportin 1 is exported by CRM1, the receptor for leucine-rich nuclear export signals (NESs). However, the interaction of CRM1 with snurportin 1 differs from that with previously characterized NESs. First, CRM1 binds snurportin 1 50-fold stronger than the Rev protein and 5,000-fold stronger than the minimum Rev activation domain. Second, snurportin 1 interacts with CRM1 not through a short peptide but rather via a large domain that allows regulation of affinity. Strikingly, snurportin 1 has a low affinity for CRM1 when bound to its m3G-capped import substrate, and a high affinity when substrate-free. This mechanism appears crucial for productive import cycles as it can ensure that CRM1 only exports snurportin 1 that has already released its import substrate in the nucleus.

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