Evolutionary conservation of the PA-X open reading frame in segment 3 of influenza A virus - PubMed (original) (raw)

Evolutionary conservation of the PA-X open reading frame in segment 3 of influenza A virus

Mang Shi et al. J Virol. 2012 Nov.

Abstract

PA-X is a fusion protein of influenza A virus encoded in part from a +1 frameshifted X open reading frame (X-ORF) in segment 3. We show that the X-ORFs of diverse influenza A viruses can be divided into two groups that differ in selection pressure and likely function, reflected in the presence of an internal stop codon and a change in synonymous diversity. Notably, truncated forms of PA-X evolved convergently in swine and dogs, suggesting a strong species-specific effect.

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Figures

Fig 1

Fig 1

Influenza A virus segment 3 showing open reading frames for PA (in frame 0) and for the PA-X ORF (in frame 1), with the frameshift motif shown. Yellow shading indicates the region of the X-ORF that is translated; blue shading indicates structural domains of PA (1, 4, 10). The PA-X open reading frame encodes either 61 or 41 amino acids as indicated. Note that the X-ORF product lies largely within a linker region between the PA N- and C-terminal domains. (Reprinted from reference with permission of the publisher).

Fig 2

Fig 2

Phylogenetic tree of the full-length PA gene (frame 0) of influenza A virus showing the occurrence of the stop codon mutation at codon 42 in the X-ORF. Because of the very large size of the data set, this tree was inferred using a subsample of 3,281 PA sequences that differed by at least 0.005 nucleotide substitution per site. Clusters are colored according to host species, with those containing the stop codon mutation at codon 42 marked by asterisks. All horizontal branch lengths are drawn to a scale of nucleotide substitutions per site.

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