Packaging signal of influenza A virus

Abstract

Influenza A virus (IAV) contains a genome with eight single-stranded, negative-sense RNA segments that encode 17 proteins. During its assembly, all eight separate viral RNA (vRNA) segments are incorporated into virions in a selective manner. Evidence suggested that the highly selective genome packaging mechanism relies on RNA-RNA or protein-RNA interactions. The specific structures of each vRNA that contribute to mediating the packaging of the vRNA into virions have been described and identified as packaging signals. Abundant research indicated that sequences required for genome incorporation are not series and are varied among virus genotypes. The packaging signals play important roles in determining the virus replication, genome incorporation and genetic reassortment of influenza A virus. In this review, we discuss recent studies on influenza A virus packaging signals to provide an overview of their characteristics and functions.

A Codon-Pair Bias Associated With Network Interactions in Influenza A, B, and C Genomes

“…There are limitations to this study. Viral genomes are tightly packed with information including overlapping ORFs, replication and packaging signals ( Li et al, 2021 ). These place constraints on different parts of the genome and, because of this, any analysis of the genome as a whole must be considered in this context.…”

“…The 5′ and 3′ non-coding portions of each segment of the genome are highly conserved where the RdRP interacts with these regions ( Murti et al, 1988 ; Krischuns et al, 2021 ). Some regions of the segment contain packaging signals or are more densely associated with nucleoprotein ( Li et al, 2021 ) and we did not analyze these separately. Future studies examining the relationship between codon-pair bias and specific coding regions will require the comparison of larger numbers of viruses.…”

Identification of the 5′-Terminal Packaging Signal of the H1N1 Influenza A Virus Neuraminidase Segment at Single-Nucleotide Resolution

“…This hypothesis is based on the observation that not all virus particles are infectious. The other is the selective packaging hypothesis, which considers that “the eight segments are selectively assembled and packaged” ( Li et al, 2021 ). The latter hypothesis is now considered the most plausible, and a variety of evidence exists, including the packaging competition phenomenon caused by defective interference (DI) vRNAs ( von Magnus, 1954 ; Nakajima et al, 1979 ; Jennings et al, 1983 ).…”

“…Vaccine seed strains are traditionally created by co-infection of a chicken egg with a vaccine parent strain and an antigen strain such as a field isolate, and the HA and NA segments are artificially exchanged ( Robertson et al, 2011 ). However, because the mechanisms of selective segment assembly and packaging are still unknown, it is not possible to know in advance whether the HA and NA segments used are interchangeable and whether the reassortant genome is stable ( Octaviani et al, 2010 ; Li et al, 2021 ). This sometimes leads to problems in vaccine development, such as the inability to prepare reassortant strains, or even if they can be prepared, they are not practical because of their poor proliferation ( Robertson et al, 2011 ).…”

“…The sixth segment (Seg.6) encodes NA, which is involved in various elementary processes of viral replication and is also important as a major antigen gene ( McAuley et al, 2019 ); however, it has been less analyzed for the selective packaging signal than the other segments ( Li et al, 2021 ). Seg.6 and Seg.2 (the PB1 segment) ( Cobbin et al, 2014 ) and Seg.6 and Seg.4 are often exchanged simultaneously when creating a reassortant virus ( Robertson et al, 2011 ) and are likely to physically interact.…”