The presence of multiple basic amino acids in the protease cleavage site of the hemagglutinin (HA) protein is the main molecular determinant of virulence of highly pathogenic avian influenza (HPAI) viruses. Recombination of HA RNA with other RNA molecules of host or virus origin is a dominant mechanism of multi basic cleavage site (MBCS) acquisition for H7 subtype HA. Using alignments of HA RNA sequences from documented cases of MBCS insertion due to recombination, we show that such recombination with host RNAs is most likely to occur at particular hotspots in ribosomal RNAs (rRNAs), transfer RNAs (tRNAs) and viral RNAs. The locations of these hotspots in highly abundant RNAs indicate that RNA recombination is facilitated by the binding of small nucleolar RNA (snoRNA) near the recombination points.

中文翻译：

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甲型流感病毒 H7 血凝素中编码碱性氨基酸的密码子的插入是通过在 snoRNA 结合位点附近的热点与 RNA 重组而发生的

血凝素（HA）蛋白的蛋白酶切割位点中存在多个碱性氨基酸是高致病性禽流感（HPAI）病毒毒力的主要分子决定因素。HA RNA 与宿主或病毒来源的其他 RNA 分子的重组是 H7 亚型 HA 获得多碱性切割位点 (MBCS) 的主要机制。通过对因重组而导致 MBCS 插入的记录案例中的 HA RNA 序列进行比对，我们发现这种与宿主 RNA 的重组最有可能发生在核糖体 RNA (rRNA)、转移 RNA (tRNA) 和病毒 RNA 的特定热点处。高丰度 RNA 中这些热点的位置表明，重组点附近的小核仁 RNA (snoRNA) 的结合促进了 RNA 重组。