Interaction network linking the human H3N2 influenza A virus genomic RNA segments

The 50-92 PB2 627K was genetically unstable during virus propagation, resulting in reversion to PB2 627E or the accumulation of the additional mutation PB2 628R and/or a synonymous mutation from an A to a G nucleotide at nucleotide position 1869 (PB2 A1869G). Intriguingly, PB2 628R and/or A1869G appeared to improve the genetic stability of 50-92 PB2 627K. However, the replication of 50-92 PB2 627K in conjunction with these stabilizing mutations was significantly restricted in experimentally infected chickens, where reversion to PB2 627E occurred. In contrast, no significant effects on viral fitness were observed for Ty/05 PB2 627E or 627K in in vitro or in vivo experiments. Our observations suggest that PB2 627K is supported in Eurasianlineage viruses; in contrast, PB2 627K carries a significant fitness cost in the historical pre-Asian 50-92 virus.

Section: Discussionmentioning

confidence: 86%

The Effect of the PB2 Mutation 627K on Highly Pathogenic H5N1 Avian Influenza Virus Is Dependent on the Virus Lineage

Long

Howard

Núñez

et al. 2013

“…In contrast, in the presence of the other seven vRNAs, the incorporation efficiency of the NP(120)GFP(120) vRNA was increased (Fig. 1), implying that the other vRNAs play a critical role in augmenting the packaging efficiency of the recombinant NP vRNA itself, possibly by direct or indirect interactions with the packaging signal of the recombinant NP vRNA (5,6,25).…”

Section: Discussionmentioning

confidence: 99%

“…1 and 3). This is likely because the bundling signal of one vRNA may interact with that of another vRNA (5,6,25), and vice versa, to mutually increase the incorporation efficiencies of the vRNAs. Previous studies have shown that a recombinant vRNA that possesses only the incorporation signal does not specifically compete with the other vRNAs in the genome-packaging process (8,28), whereas a defective-interference (DI) vRNA, which typically contains the bundling signal, competes with its parental vRNA specifically (32,33).…”

Section: Discussionmentioning

confidence: 99%

“…The introduction of mutations into the genomepackaging signal markedly reduces the packaging efficiency of the mutated vRNA into progeny virions (16)(17)(18)(19)(20)(21)(22)(23)(24), as well as that of the other vRNAs (14,18,21), demonstrating the significance of the genome-packaging signal for vRNA incorporation into virions. Recent electron microscopic and biochemical studies suggest that there should be interactions among the vRNAs, most likely in the form of RNPs (5,6,25); however, it remains unclear how these packaging signals function during vRNA incorporation into virions. Here, we used reverse genetics to clarify the role of the packaging signals.…”

mentioning

confidence: 99%

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The Genome-Packaging Signal of the Influenza A Virus Genome Comprises a Genome Incorporation Signal and a Genome-Bundling Signal

Goto

Muramoto

Noda

et al. 2013

The influenza A virus genome comprises eight single-stranded negative-sense RNA segments (vRNAs). All eight vRNAs are selectively packaged into each progeny virion via so-called segment-specific genome-packaging signal sequences that are located in the noncoding and terminal coding regions of both the 3= and the 5= ends of the vRNAs. However, it remains unclear how these signals ensure that eight different vRNAs are packaged. Here, by using a reverse genetics system, we demonstrated that, in the absence of the other seven vRNAs, a recombinant NP vRNA bearing only a reporter gene flanked by the noncoding NP regions was incorporated into virus-like particles (VLPs) as efficiently as a recombinant NP vRNA bearing the reporter gene flanked by the complete NP packaging signals (i.e., the noncoding sequences and the terminal coding regions). Viruses that comprised a recombinant NP vRNA whose packaging signal was disrupted, and the remaining seven authentic vRNAs, did not undergo multiple cycles of replication; however, a recombinant NP vRNA with only the noncoding regions was readily incorporated into VLPs, suggesting that the packaging signal as currently defined is not necessarily essential for the packaging of the vRNA in which it resides; rather, it is required for the packaging of the full set of vRNAs. We propose that the 3= and 5= noncoding regions of each vRNA bear a virion incorporation signal for that vRNA and that the terminal coding regions serve as a bundling signal that ensures the incorporation of the complete set of eight vRNAs into the virion.

“…Recent studies have shown that the eight unique vRNA segments that form RNPs are selectively packaged into each virion through segment-specific packaging signals that are present at the 5= and 3= ends of the vRNA segments (13)(14)(15)(16)(17). It has also been demonstrated by EM that the eight RNPs within the virions are arranged in a characteristic pattern-seven RNPs surround a central RNP-and that this set of eight RNPs associates vertically with an inner viral envelope at the tip of the budding virion (14,15).…”

mentioning

confidence: 99%

Configuration of Viral Ribonucleoprotein Complexes within the Influenza A Virion

Sugita

Sagara

Noda

et al. 2013

The influenza A virus possesses an eight-segmented, negative-sense, single-stranded RNA genome (vRNA). Each vRNA segment binds to multiple copies of viral nucleoproteins and a small number of heterotrimeric polymerase complexes to form a rod-like ribonucleoprotein complex (RNP), which is essential for the transcription and replication of the vRNAs. However, how the RNPs are organized within the progeny virion is not fully understood. Here, by focusing on polymerase complexes, we analyzed the fine structure of purified RNPs and their configuration within virions by using various electron microscopies (EM). We confirmed that the individual RNPs possess a single polymerase complex at one end of the rod-like structure and that, as determined using immune EM, some RNPs are incorporated into budding virions with their polymerase-binding ends at the budding tip, whereas others align with their polymerase-binding ends at the bottom of the virion. These data further our understanding of influenza virus virion morphogenesis.