Structure-guided taxonomic placement of divergent RNA viruses with ViraClass
基于结构的RNA病毒分类定位:ViraClass
Sheng Xu, Wenxuan Huang, Shutong Yue, Weiqiang Bai, Shiyang Feng, Xiaohan He, Bo Zhang, Qiantai Feng, Edward C. Holmes, Weifeng Shi, Siqi Sun
AI总结 针对RNA病毒分类中RdRp序列相似性低的问题,提出基于蛋白质结构的ViraClass框架,实现从门到属的层级分类,在深度进化距离上优于序列方法。
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宏转录组测序扩展了我们对RNA病毒圈的认识,其速度远超新病毒的分类学鉴定。科级以上的分类尤为困难,因为RNA依赖的RNA聚合酶(RdRp)通常是RNA病毒中唯一保留的基因,但在高度分化的病毒中序列相似性极低。这里我们证明,在RdRp一级序列相似性基本消失的进化深度上,RdRp蛋白质结构保留了分类信号,且这些信号的组织方式与当前ICTV层级一致。基于此,我们开发了ViraClass,一个用于RNA病毒分类定位的层级框架,它利用RdRp结构进行从门到属的逐级分类,在置信阈值支持的最深等级停止,并对仍处于现有参考空间之外的病毒进行校准的结构聚类。在随机分割、前瞻性和分类学保留基准测试中,ViraClass优于基于序列和基因组内容的基线方法。最大的提升出现在深度进化距离上,在从参考中保留整个科、目或纲的基准测试中,基于序列的方法失去了大部分信号。在诸如黄病毒科等具有挑战性的边界案例中,ViraClass基于结构的分类定位捕捉到了近期系统发育研究强调的分类边界张力。当应用于大量先前未分类的RdRp序列时,ViraClass将高置信度查询归入现有门,并将剩余序列组织成紧凑的结构组。因此,ViraClass提供了一种可扩展的方法,从大规模病毒发现到层级分类解释,特别是在当前基于序列的流程无法达到的深度进化范围。
Metatranscriptomic sequencing has expanded our knowledge of the RNA virosphere far more rapidly than novel viruses can be taxonomically classified. Taxonomic assignment above the family level is particularly difficult because the RNA-dependent RNA polymerase (RdRp) is often the only gene retained across RNA viruses yet exhibits little sequence similarity among highly divergent viruses. Here we show that RdRp protein structure retains taxonomic signal at evolutionary depths where RdRp primary sequence similarity has largely collapsed, and that the organization of this signal is consistent with the current ICTV hierarchy. Based on this, we developed ViraClass, a hierarchical framework for RNA virus taxonomic placement that uses RdRp structure for rank-by-rank assignment from phylum to genus, stopping at the deepest rank supported by confidence thresholds, and calibrated structural clustering for viruses that remain outside existing reference space. Across random-split, prospective and taxonomic hold-out benchmarks, ViraClass outperforms sequence-based and genome-content baselines. The largest gains emerge at deep evolutionary distances, in benchmarks that withhold entire families, orders or classes from the reference, where sequence-based methods lose most of their signal. In challenging boundary cases such as the Flaviviridae, ViraClass's structure-based placements capture the taxonomic boundary tensions highlighted by recent phylogenetic studies. When applied to a large collection of previously unclassified RdRp sequences, ViraClass places high-confidence queries into existing phyla and organizes the remainder into compact structural groups. ViraClass therefore provides a scalable approach from large-scale virus discovery to hierarchical taxonomic interpretation, particularly at the deep evolutionary ranges that current sequence-based pipelines cannot reach.