Location of Influenza Virus M, NP and NS1 Proteins in Microinjected Cells

Davey, John; Colman, Alan; Dimmock, Nigel J.

doi:10.1099/0022-1317-66-11-2319

Cited by 20 publications

(8 citation statements)

References 58 publications

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“…The second NLS is a bipartite signal located in the middle of NP between residues 198–216 which contributes less to the nuclear localization of NP than the unconventional NLS at the amino-terminus [ 26 ]. Furthermore, a nuclear accumulation site has been attributed to residues 336–345 in microinjection studies employing Xenopus oocytes and cells of rodent and primate origin [ 27 , 28 ]. None of these sites includes amino acid 319.…”

Section: Discussionmentioning

confidence: 99%

Interaction of Polymerase Subunit PB2 and NP with Importin α1 Is a Determinant of Host Range of Influenza A Virus

2008

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We have previously reported that mutations in the polymerase proteins PB1, PB2, PA, and the nucleocapsid protein NP resulting in enhanced transcription and replication activities in mammalian cells are responsible for the conversion of the avian influenza virus SC35 (H7N7) into the mouse-adapted variant SC35M. We show now that adaptive mutations D701N in PB2 and N319K in NP enhance binding of these proteins to importin α1 in mammalian cells. Enhanced binding was paralleled by transient nuclear accumulation and cytoplasmic depletion of importin α1 as well as increased transport of PB2 and NP into the nucleus of mammalian cells. In avian cells, enhancement of importin α1 binding and increased nuclear transport were not observed. These findings demonstrate that adaptation of the viral polymerase to the nuclear import machinery plays an important role in interspecies transmission of influenza virus.

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Section: Discussionmentioning

confidence: 99%

Interaction of Polymerase Subunit PB2 and NP with Importin α1 Is a Determinant of Host Range of Influenza A Virus

2008

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“…In all cases, NP was shown to be a nuclear protein, but the shuttling capacity of NP has not been studied. Interestingly, expressed NP was often found to be in a soluble fraction of the nucleus, (8,18), in contrast to influenza virus infection, in which NP was assembled into vRNPs and was insoluble. This difference in nuclear binding may well account for the NP shuttling seen in the 3PNP-4 cells.…”

Section: Discussionmentioning

confidence: 99%

Nuclear trafficking of influenza virus ribonuleoproteins in heterokaryons

Whittaker

Bui

Helenius

1996

J Virol

111

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The influenza virus nucleoprotein (NP), matrix protein (M1), and ribonucleoproteins (vRNPs) undergo regulated nuclear import and export during infection. Their trafficking was analyzed by using interspecies heterokaryons containing nuclei from infected and uninfected cells. Under normal conditions, it was demonstrated that the vRNPs which were assembled in the nucleus and transported to the cytosol were prevented from reimport into the nucleus. To be import competent, they must first assemble into virions and enter by the endosomal entry pathway. In influenza virus mutant ts51, in which M1 is defective, direct reimport took place but was inhibited by heterologous expression of wild-type M1. These data confirm M1's role as the inhibitor of premature nuclear import and as the main regulator of nuclear transport of vRNPs. In addition to this vRNP shuttling, M1 also shuttled between the nucleus and the cytoplasm in ts51-infected cells. When NP was expressed in the absence of virus infection, it was also found to be a shuttling protein.

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“…The nucleolus contains complexes of proteins and various types of RNA but is not separated by membranes from the surrounding nucleoplasm. Although nucleolar localization of NP was reported more than 20 years ago (7,8), the peptide motif for NP nucleolar localization remained unknown. Weber et al (30) proposed that the amino acid sequence (R/KR/K)X(R/K) functions as a nucleolar localization signal.…”

Section: Discussionmentioning

confidence: 99%

Contributions of Two Nuclear Localization Signals of Influenza A Virus Nucleoprotein to Viral Replication

Ozawa

Fujii

Muramoto

et al. 2007

J Virol

204

221

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The RNA genome of influenza A virus, which forms viral ribonucleoprotein complexes (vRNPs) with viral polymerase subunit proteins (PA, PB1, and PB2) and nucleoprotein (NP), is transcribed and replicated in the nucleus. NP, the major component of vRNPs, has at least two amino acid sequences that serve as nuclear localization signals (NLSs): an unconventional NLS (residues 3 to 13; NLS1) and a bipartite NLS (residues 198 to 216; NLS2). Although both NLSs are known to play a role in nuclear transport, their relative contributions to viral replication are poorly understood. We therefore investigated their contributions to NP subcellular/ subnuclear localization, viral RNA (vRNA) transcription, and viral replication. Abolishing the unconventional NLS caused NP to localize predominantly to the cytoplasm and affected its activity in vRNA transcription. However, we were able to create a virus whose NP contained amino acid substitutions in NLS1 known to abolish its nuclear localization function, although this virus was highly attenuated. These results indicate that while the unconventional NLS is not essential for viral replication, it is necessary for efficient viral mRNA synthesis. On the other hand, the bipartite NLS, whose contribution to the nuclear transport of NP is limited, was essential for vRNA transcription and NP's nucleolar accumulation. A virus with nonfunctional NLS2 could not be generated. Thus, the bipartite NLS, but not the unconventional NLS, of NP is essential for influenza A virus replication.Influenza A virus, a member of the family Orthomyxoviridae, is characterized by segmented RNA genomes of negative polarity (16). The viral genome encodes at least 11 proteins (4, 16) and consists of eight single-stranded RNA segments. These genomic RNAs are incorporated into virions as viral ribonucleoprotein complexes (vRNPs) that comprise viral RNA (vRNA), heterotrimeric viral polymerase subunit proteins (PA, PB1, and PB2), and nucleoprotein (NP). A unique property of influenza viruses among RNA viruses is that every step of vRNA synthesis take place in the nucleus by use of the nuclear machinery of the host cells (16). Therefore, newly synthesized proteins required for the vRNPs must be transported into the nuclei of the cells.The transport of proteins (larger than 50 kDa) from the cytoplasm into the nucleus is regulated by signal-mediated processes. Peptide motifs that allow the proteins to be imported through the nuclear pore complex are referred to as nuclear localization signals (NLSs). They are rich in basic amino acids and bind to NLS receptors (e.g., karyopherin family members), which are responsible for the nuclear translocation of target proteins (12,31). Of the influenza A virus proteins, NLSs have been found in three polymerase subunits, the matrix M1 protein (which associates with vRNP complexes), the nonstructural NS1 protein, and NP, the primary component of vRNPs (for a review, see reference 6).NP has at least two NLS sequences. An unconventional NLS (termed here NLS1) is located between residu...

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Location of Influenza Virus M, NP and NS1 Proteins in Microinjected Cells

Cited by 20 publications

References 58 publications

Interaction of Polymerase Subunit PB2 and NP with Importin α1 Is a Determinant of Host Range of Influenza A Virus

Interaction of Polymerase Subunit PB2 and NP with Importin α1 Is a Determinant of Host Range of Influenza A Virus

Nuclear trafficking of influenza virus ribonuleoproteins in heterokaryons

Contributions of Two Nuclear Localization Signals of Influenza A Virus Nucleoprotein to Viral Replication

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