Rapid fixation of a distinctive sequence motif in the 3' noncoding region of the clade of West Nile virus invading North America
Rapid fixation of a distinctive sequence motif in the 3' noncoding region of the clade of West Nile virus invading North America
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DOI：
10.1016/j.gene.2007.05.007
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发表时间：
2007-09-15
期刊：
影响因子：
3.5
通讯作者：
Foppa, Ivo
中科院分区：
文献类型：
--
作者：
Hughes, Austin L.;Piontkivska, Helen;Foppa, Ivo
通过多种方法对西尼罗河病毒（WNV）全基因组进行系统发育分析，支持了WNV北美分离株与以色列分离株和匈牙利分离株构成单系群的假设。我们使用祖先序列重建，以获得进化变化的证据，这些变化可能与该进化枝（命名为N.A.进化枝）。在N.A.的祖先中发生了一个氨基酸变化（NS 3蛋白的残基356处的I -> T）。进化枝，并保持保守的所有N.A.分析进化枝基因组。在N.A.的祖先中，在3'非编码区的上游部分（AT富集区）有四个变化。进化枝，并保持保守的所有N.A.进化枝基因组分析，预测改变RNA二级结构的变化。AT富集区在N. A祖先的分支中显示出较高的置换率。进化枝，相对于多态性，比其余的非编码区，编码区的同义位点，或编码区的非同义位点。该区域固定核苷酸置换的发生率较高，表明积极的达尔文选择可能对3 'NCR的这一部分起作用，并且这些固定变化（可能与NS 3中的氨基酸变化一致）可能是与北美WNV（c）2007 Elsevier B. V.中毒力增加相关的表型效应的基础。
Phylogenetic analysis of complete genomes of West Nile virus (WNV) by a variety of methods supported the hypothesis that North American isolates of WNV constitute a monophyletic group, together with an isolate from Israel and one from Hungary. We used ancestral sequence reconstruction in order to obtain evidence for evolutionary changes that might be correlated with increased virulence in this clade (designated the N.A. clade). There was one amino acid change (I -> T at residue 356 of the NS3 protein) that occurred in the ancestor of the N.A. clade and remained conserved in all N.A. clade genomes analyzed. There were four changes in the upstream portion of the 3' noncoding region (the AT-enriched region) that occurred in the ancestor of the N.A. clade and remained conserved in all N.A. clade genomes analyzed, changes predicted to alter RNA secondary structure. The AT-enriched region showed a higher rate of substitution in the branch ancestral to the N.A. clade, relative to polymorphism, than did the remainder of the noncoding regions, synonymous sites in coding regions, or nonsynonymous sites in coding regions. The high rate of occurrence of fixed nucleotide substitutions in this region suggests that positive Darwinian selection,may have acted on this portion of the 3'NCR and that these fixed changes, possibly in concert with the amino acid change in NS3, may underlie phenotypic effects associated with increased virulence in North American WNV (c) 2007 Elsevier B.V. All rights reserved.