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A conserved influenza A virus nucleoprotein code controls specific viral genome packaging

View Article: PubMed Central - PubMed

ABSTRACT

Packaging of the eight genomic RNA segments of influenza A viruses (IAV) into viral particles is coordinated by segment-specific packaging sequences. How the packaging signals regulate the specific incorporation of each RNA segment into virions and whether other viral or host factors are involved in this process is unknown. Here, we show that distinct amino acids of the viral nucleoprotein (NP) are required for packaging of specific RNA segments. This was determined by studying the NP of a bat influenza A-like virus, HL17NL10, in the context of a conventional IAV (SC35M). Replacement of conserved SC35M NP residues by those of HL17NL10 NP resulted in RNA packaging defective IAV. Surprisingly, substitution of these conserved SC35M amino acids with HL17NL10 NP residues led to IAV with altered packaging efficiencies for specific subsets of RNA segments. This suggests that NP harbours an amino acid code that dictates genome packaging into infectious virions.

No MeSH data available.


Related in: MedlinePlus

Genome packaging sequence or NP code mutations disrupt coordinated packaging of eight influenza genome segments into viral particles.Wt NP code and vRNA packaging sequences ensure coordinated incorporation of the eight different genome segments into influenza A virus particles, resulting in an equal ratio of the individual viral genome segments (left panel). As indicated by dashed lines, packaging could be coordinated by various interactions between segment-specific vRNPs, including interactions between vRNA packaging sequences, between vRNA packaging sequences in one vRNP and amino acids of the NP code (indicated in yellow) in a second vRNP, and direct interactions of the NP code amino acids. Mutations in the NP code and/or vRNA packaging sequence result in the loss of coordinated packaging of the eight different genome segments into viral particles and a disproportional ratio of the viral segments (right panel). Loss of coordinated packaging might be caused by impaired interactions between vRNPs mediated by amino acids of the NP code and/or nucleotides of the RNA packaging sequences.
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f6: Genome packaging sequence or NP code mutations disrupt coordinated packaging of eight influenza genome segments into viral particles.Wt NP code and vRNA packaging sequences ensure coordinated incorporation of the eight different genome segments into influenza A virus particles, resulting in an equal ratio of the individual viral genome segments (left panel). As indicated by dashed lines, packaging could be coordinated by various interactions between segment-specific vRNPs, including interactions between vRNA packaging sequences, between vRNA packaging sequences in one vRNP and amino acids of the NP code (indicated in yellow) in a second vRNP, and direct interactions of the NP code amino acids. Mutations in the NP code and/or vRNA packaging sequence result in the loss of coordinated packaging of the eight different genome segments into viral particles and a disproportional ratio of the viral segments (right panel). Loss of coordinated packaging might be caused by impaired interactions between vRNPs mediated by amino acids of the NP code and/or nucleotides of the RNA packaging sequences.

Mentions: Surprisingly, mutation of conserved amino acid residues in the NP body domain resulted in the incorporation of a different subset of viral genome segments than those seen with alteration of the NP head domain. Similarly, irregular genome packaging has been observed after mutating packaging signal sequences of IAV genomes1826272829303132. Depending on the nucleotide mutations introduced into individual packaging sequences, coordinated packaging was lost and different sets of viral genomes were incorporated into viral particles. Thus disruption of either the RNA packaging sequences or amino acids of the NP packaging code can block coordinated packaging of the eight genome segments and, as a consequence, may cause impaired release of infectious viral particles (Fig. 6). Although formal proof is still missing, this might suggest that the ‘NP packaging code' is complex and has to match to individual genome packaging sequences in order to coordinate the incorporation of a full complement of eight genome segments into budding viral particles. Since RNA loop regions are believed to interact with each other thereby orchestrating the coordinated packaging of the different genome segments14, it is tempting to speculate that the ‘NP packaging code' provides the required vRNP conformations that facilitate RNA loop interactions between different vRNPs.


A conserved influenza A virus nucleoprotein code controls specific viral genome packaging
Genome packaging sequence or NP code mutations disrupt coordinated packaging of eight influenza genome segments into viral particles.Wt NP code and vRNA packaging sequences ensure coordinated incorporation of the eight different genome segments into influenza A virus particles, resulting in an equal ratio of the individual viral genome segments (left panel). As indicated by dashed lines, packaging could be coordinated by various interactions between segment-specific vRNPs, including interactions between vRNA packaging sequences, between vRNA packaging sequences in one vRNP and amino acids of the NP code (indicated in yellow) in a second vRNP, and direct interactions of the NP code amino acids. Mutations in the NP code and/or vRNA packaging sequence result in the loss of coordinated packaging of the eight different genome segments into viral particles and a disproportional ratio of the viral segments (right panel). Loss of coordinated packaging might be caused by impaired interactions between vRNPs mediated by amino acids of the NP code and/or nucleotides of the RNA packaging sequences.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5035998&req=5

f6: Genome packaging sequence or NP code mutations disrupt coordinated packaging of eight influenza genome segments into viral particles.Wt NP code and vRNA packaging sequences ensure coordinated incorporation of the eight different genome segments into influenza A virus particles, resulting in an equal ratio of the individual viral genome segments (left panel). As indicated by dashed lines, packaging could be coordinated by various interactions between segment-specific vRNPs, including interactions between vRNA packaging sequences, between vRNA packaging sequences in one vRNP and amino acids of the NP code (indicated in yellow) in a second vRNP, and direct interactions of the NP code amino acids. Mutations in the NP code and/or vRNA packaging sequence result in the loss of coordinated packaging of the eight different genome segments into viral particles and a disproportional ratio of the viral segments (right panel). Loss of coordinated packaging might be caused by impaired interactions between vRNPs mediated by amino acids of the NP code and/or nucleotides of the RNA packaging sequences.
Mentions: Surprisingly, mutation of conserved amino acid residues in the NP body domain resulted in the incorporation of a different subset of viral genome segments than those seen with alteration of the NP head domain. Similarly, irregular genome packaging has been observed after mutating packaging signal sequences of IAV genomes1826272829303132. Depending on the nucleotide mutations introduced into individual packaging sequences, coordinated packaging was lost and different sets of viral genomes were incorporated into viral particles. Thus disruption of either the RNA packaging sequences or amino acids of the NP packaging code can block coordinated packaging of the eight genome segments and, as a consequence, may cause impaired release of infectious viral particles (Fig. 6). Although formal proof is still missing, this might suggest that the ‘NP packaging code' is complex and has to match to individual genome packaging sequences in order to coordinate the incorporation of a full complement of eight genome segments into budding viral particles. Since RNA loop regions are believed to interact with each other thereby orchestrating the coordinated packaging of the different genome segments14, it is tempting to speculate that the ‘NP packaging code' provides the required vRNP conformations that facilitate RNA loop interactions between different vRNPs.

View Article: PubMed Central - PubMed

ABSTRACT

Packaging of the eight genomic RNA segments of influenza A viruses (IAV) into viral particles is coordinated by segment-specific packaging sequences. How the packaging signals regulate the specific incorporation of each RNA segment into virions and whether other viral or host factors are involved in this process is unknown. Here, we show that distinct amino acids of the viral nucleoprotein (NP) are required for packaging of specific RNA segments. This was determined by studying the NP of a bat influenza A-like virus, HL17NL10, in the context of a conventional IAV (SC35M). Replacement of conserved SC35M NP residues by those of HL17NL10 NP resulted in RNA packaging defective IAV. Surprisingly, substitution of these conserved SC35M amino acids with HL17NL10 NP residues led to IAV with altered packaging efficiencies for specific subsets of RNA segments. This suggests that NP harbours an amino acid code that dictates genome packaging into infectious virions.

No MeSH data available.


Related in: MedlinePlus