The genome of influenza A virus consists of eight single-stranded negative-polarity RNA segments. The eighth segment (NS) encodes the anti-interferon protein NS1 (27 kDa) and the nuclear export protein NEP (14 kDa) via the classic negative-sense strategy. It also contains an additional positive-sense open reading frame that can be directly translated into the negative strand protein 8 (NSP8; 18–25 kDa in different strains). The existence of three or more genes of the opposite polarity in the same locus of a single-stranded RNA appears to be a unique (“economical”) type of gene architecture in living organisms. In silico analysis of genomes of human and animal influenza A viruses revealed that the NSP8 gene had emerged in the influenza A virus population about 100 years ago (“young” gene) and is highly evolutionary variable. The obtained experimental data suggest that NSP8 gene is expressed in the infected animals, which strengthens the concept of bipolar (ambisense) strategy of the influenza A virus genome. The high variability of the NSP8 protein suggests that the “young” NSP8 gene is in the process of functional optimization. Further accumulation of mutations may alter the functions of mature NSP8 protein and lead to the emergence of mature bipolar influenza A virus with unexpected properties that would be threatening for humans and animals.

中文翻译：

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甲型流感病毒 RNA 基因组中独特的双极基因结构

甲型流感病毒的基因组由八个单链负极性 RNA 片段组成。第八个片段 (NS) 通过经典的负义策略编码抗干扰素蛋白 NS1 (27 kDa) 和核输出蛋白 NEP (14 kDa)。它还包含一个额外的正义开放阅读框，可以直接翻译成负链蛋白 8（NSP8；在不同菌株中为 18-25 kDa）。在单链 RNA 的同一基因座中存在三个或更多极性相反的基因似乎是活生物体中一种独特（“经济”）的基因结构类型。人类和动物甲型流感病毒基因组的计算机分析显示，NSP8 基因大约在 100 年前出现在甲型流感病毒种群中（“年轻”基因），并且是高度进化变量。获得的实验数据表明，NSP8基因在受感染动物中表达，强化了甲型流感病毒基因组双极（ambisense）策略的概念。NSP8 蛋白的高变异性表明“年轻”的 NSP8 基因正处于功能优化的过程中。突变的进一步积累可能会改变成熟 NSP8 蛋白的功能，并导致成熟的双极型甲型流感病毒出现，其具有对人类和动物构成威胁的意想不到的特性。