Virions and intracellular nucleocapsids produced during mixed heterotypic influenza infection of MDCK cells

Sklyanskaya, E. I.; Varich, N. L.; Amvrosieva, T. V.; Каверин, Н. В.

doi:10.1128/jvi.53.2.679-683.1985

Cited by 7 publications

(3 citation statements)

References 12 publications

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“…It is possible that the N-terminal extension of type B virus NP has a role in the specific incorporation of vRNPs into influenza B virus particles. It has been reported that, while type A and B virus NPs may exist in the same RNP complex in vivo, these phenotypically mixed forms are not incorporated into virions (33). Since the NPs of type A and B viruses differ most at their N termini, the N-terminal extension may be involved in the selection of RNPs containing only type B virus NP.…”

Section: N-terminal Deletions In Influenza B Virus Np Do Not Affect Tmentioning

confidence: 99%

The N-Terminal Extension of the Influenza B Virus Nucleoprotein Is Not Required for Nuclear Accumulation or the Expression and Replication of a Model RNA

Stevens

Barclay

1998

J Virol

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The nucleoprotein (NP) of influenza B virus is 50 amino acids longer at the N-terminus than influenza A virus NP and lacks homology to the A virus protein over the first 69 residues. We have deleted the N-terminal 51 and 69 residues of the influenza B/Ann Arbor/1/66 virus NP and show that nuclear accumulation of the protein is unaffected. This indicates that the nuclear localization signal is not located at the extreme N terminus, as in influenza A virus NP. To determine if the N-terminal mutants could support the expression and replication of a model influenza B virus RNA, the genes encoding the subunits of the viral RNA-dependent RNA polymerase (PA, PB1, and PB2) were cloned. Coexpression of NP and the P proteins in 293 cells was found to permit the expression and replication of a transfected model RNA based on segment 4 of B/Maryland/59, in which the hemagglutinin-coding region was replaced by a chloramphenicol acetyltransferase gene. The expression and replication of the synthetic RNA were not affected by the replacement of NP with NP mutants lacking the N-terminal 51 or 69 residues, indicating that the N-terminal extension is not required for transcription or replication of the viral RNA. In addition, we report that the influenza B virus NP cannot be functionally replaced by type A virus NP in this system.

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Section: N-terminal Deletions In Influenza B Virus Np Do Not Affect Tmentioning

confidence: 99%

The N-Terminal Extension of the Influenza B Virus Nucleoprotein Is Not Required for Nuclear Accumulation or the Expression and Replication of a Model RNA

Stevens

Barclay

1998

J Virol

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“…In contrast, the cytoplasmic tails of the other two virion envelope proteins, haemagglutinin (HA) and neuraminidase (NA), can be deleted both individually or simultaneously without loss of virus viability (Garcia-Sastre and Palese, 1995;Jin et al, 1997). Incorporation of HA into influenza particles is not a type-specific event because influenza A virus HA proteins are incorporated into influenza B virus particles after double infection of cells (Sklyanskaya et al, 1985). Whether the NA proteins also show phenotypic mixing is not known, although it is noteworthy that an influenza A virus has been recovered in which the sequence of the cytoplasmic tail of NA was exchanged for that of an influenza B virus NA protein (Bilsel et al, 1993).…”

Section: Introductionmentioning

confidence: 99%

Phosphorylation of the M2 Protein of Influenza A Virus Is Not Essential for Virus Viability

et al. 1998

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M2 is a minor component of the influenza A virus envelope. The cytoplasmic tail of the M2 protein is posttranslationally modified in the infected cell by palmitylation and phosphorylation. The primary site for phosphorylation of the M2 cytoplasmic tail is serine 64, which is highly conserved yet not required for the activity of the M2 ion channel. Using an exogenous incorporation assay, we have shown that incorporation of M2 into virus particles is type-specific and does not require phosphorylation of the cytoplasmic tail. In addition, phosphorylation of the cytoplasmic tail is not required for the directional transport of M2 in polarized MDCK cells. Using a reverse genetics and reassortment procedure, we generated a virus (Ra) specifically mutated in segment 7 such that the M2 cytoplasmic tail could no longer be phosphorylated. The virus was found to grow as well as wild-type virus in tissue culture and in eggs, was stable on passage in these systems, and possessed no second-site mutations in the engineered RNA segment. In vivo Ra replicated in Balb/c mice at least as well as the parent strain A/WSN/33. These studies indicate that phosphorylation of the M2 cytoplasmic tail is not required for in vitro or in vivo replication of influenza A virus.

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“…Depending on the RNA length, each RNP segment contains from 30 to 100 molecules of the major nucleocapsid protein (NP) (19,45) and several molecules of three high-molecular-mass (ϳ90 kDa) polymerase proteins: PB1, PB2, and PA (10,40,50). The viral RNP structures mediate transcription and replication of the viral genome (13,25,30) and participate in the morphogenesis and assembly process of virus particles (37,54,60) in infected cells. NP plays significant roles in these events by regulating intracellular transport of viral RNPs (5,35,55) and metabolic processes of transcription and replication (6,9,28,53).…”

mentioning

confidence: 99%

Caspase-Dependent N-Terminal Cleavage of Influenza Virus Nucleocapsid Protein in Infected Cells

Жирнов

Конакова

Garten

et al. 1999

J Virol

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The nucleocapsid protein (NP) (56 kDa) of human influenza A viruses is cleaved in infected cells into a 53-kDa form. Likewise, influenza B virus NP (64 kDa) is cleaved into a 55-kDa protein with a 62-kDa intermediate (O. P. Zhirnov and A. G. Bukrinskaya, Virology 109:174–179, 1981). We show now that an antibody specific for the N terminus of influenza A virus NP reacted with the uncleaved 56-kDa form but not with the truncated NP53 form, indicating the removal of a 3-kDa peptide from the N terminus. Amino acid sequencing revealed the cleavage sites ETD16*G for A/Aichi/68 NP and sites DID7*G and EAD61*V for B/Hong Kong/72 NP. With D at position −1, acidic amino acids at position −3, and aliphatic ones at positions −2 and +1, the NP cleavage sites show a recognition motif typical for caspases, key enzymes of apoptosis. These caspase cleavage sites demonstrated evolutionary stability and were retained in NPs of all human influenza A and B viruses. NP of avian influenza viruses, which is not cleaved in infected cells, contains G instead of D at position 16. Oligopeptide DEVD derivatives, specific caspase inhibitors, were shown to prevent the intracellular cleavage of NP. All three events, the NP cleavage, the increase of caspase activity, and the development of apoptosis, coincide in cells infected with human influenza A and B viruses. The data suggest that intracellular cleavage of NP is exerted by host caspases and is associated with the development of apoptosis at the late stages of infection.

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Virions and intracellular nucleocapsids produced during mixed heterotypic influenza infection of MDCK cells

Cited by 7 publications

References 12 publications

The N-Terminal Extension of the Influenza B Virus Nucleoprotein Is Not Required for Nuclear Accumulation or the Expression and Replication of a Model RNA

The N-Terminal Extension of the Influenza B Virus Nucleoprotein Is Not Required for Nuclear Accumulation or the Expression and Replication of a Model RNA

Phosphorylation of the M2 Protein of Influenza A Virus Is Not Essential for Virus Viability

Caspase-Dependent N-Terminal Cleavage of Influenza Virus Nucleocapsid Protein in Infected Cells

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