Luque Daniel, Rivas Germán, Alfonso Carlos, Carrascosa José L, Rodríguez José F, Castón José R
Department of Structure of Macromolecules, Centro Nacional de Biotecnología/CSIC, Cantoblanco, 28049 Madrid, Spain.
Proc Natl Acad Sci U S A. 2009 Feb 17;106(7):2148-52. doi: 10.1073/pnas.0808498106. Epub 2009 Jan 21.
Viruses are a paradigm of the economy of genome resources, reflected in their multiplication strategy and for their own structure. Although there is enormous structural diversity, the viral genome is always enclosed within a proteinaceous coat, and most virus species are haploid; the only exception to this rule are the highly pleomorphic enveloped viruses. We performed an in-depth characterization of infectious bursal disease virus (IBDV), a non-enveloped icosahedral dsRNA virus with a bisegmented genome. Up to 6 natural populations can be purified, which share a similar protein composition but show higher sedimentation coefficients as particle density increases. Stoichiometry analysis of their genome indicated that these biophysical differences correlate with the copy number of dsRNA segments inside the viral capsid. This is a demonstration of a functional polyploid icosahedral dsRNA virus. We show that IBDV particles with greater genome copy number have higher infectivity rates. Our results show an unprecedented replicative strategy for dsRNA viruses and suggest that birnaviruses are living viral entities encompassing numerous functional and structural characteristics of positive and negative ssRNA viruses.
病毒是基因组资源经济性的典范，这体现在它们的增殖策略及其自身结构上。尽管病毒存在巨大的结构多样性，但病毒基因组总是被包裹在蛋白质衣壳内，并且大多数病毒种类是单倍体；这条规则的唯一例外是高度多形的包膜病毒。我们对传染性法氏囊病病毒（IBDV）进行了深入表征，它是一种具有双节段基因组的无包膜二十面体双链RNA病毒。可以纯化出多达6个自然群体，它们具有相似的蛋白质组成，但随着颗粒密度增加，沉降系数更高。对其基因组的化学计量分析表明，这些生物物理差异与病毒衣壳内双链RNA片段的拷贝数相关。这证明了一种功能性多倍体二十面体双链RNA病毒。我们表明，具有更高基因组拷贝数的IBDV颗粒具有更高的感染率。我们的结果展示了双链RNA病毒前所未有的复制策略，并表明双RNA病毒是包含正链和负链单链RNA病毒众多功能和结构特征的有生命的病毒实体。
