Distant Mimivirus relative with a larger genome highlights the fundamental features of Megaviridae
Distant Mimivirus relative with a larger genome highlights the fundamental features of Megaviridae
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DOI：
10.1073/pnas.1110889108
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发表时间：
2011-10-18
影响因子：
11.1
通讯作者：
Claverie, Jean-Michel
中科院分区：
文献类型：
--
作者：
Arslan, Defne;Legendre, Matthieu;Claverie, Jean-Michel
拟菌病毒是一种感染棘阿米巴的DNA病毒，长期以来无论是颗粒大小还是基因含量都是已知最大的病毒。其基因组编码 979 种蛋白质，包括在细胞生物体外发现的前四种氨酰 tRNA 合成酶（ArgRS、CysRS、MetRS 和 TyrRS）。拟菌病毒编码标志性细胞功能的发现促使大量理论研究重新审视病毒的概念，并将大型 DNA 病毒与早期真核生物的出现联系起来。然而，在没有表现出适当进化分歧的拟菌病毒亲属的情况下，这些独特特征的进化意义仍然无法评估。在这里，我们介绍了智利巨病毒，这是一种在智利海岸分离出来的巨型病毒，但能够在淡水棘阿米巴中复制。其 1,259,197 bp 基因组是迄今为止已完全测序的最大病毒基因组。它编码 1,120 种推定蛋白质，其中 258 种 (23%) 没有拟菌病毒同源物。 594 个巨型病毒/拟菌病毒直系同源物平均有 50% 的相同残基。尽管存在这种差异，巨病毒保留了拟菌病毒的所有基因组特征，包括其细胞样基因。此外，Megavirus 还表现出三个额外的氨酰基-tRNA 合成酶基因（IleRS、TrpRS 和 AsnRS），这为之前的建议提供了强有力的支持，即 Mimivirus/Megavirus 谱系是通过还原进化从祖先细胞基因组进化而来的。拟菌病毒和巨病毒基因组之间基因内容的主要差异是由于（i）谱系特定基因的获得或丢失，（ii）谱系特定基因家族的扩展或删除，以及（iii）移动元件（内含子、内含子）的插入/迁移。
Mimivirus, a DNA virus infecting acanthamoeba, was for a long time the largest known virus both in terms of particle size and gene content. Its genome encodes 979 proteins, including the first four aminoacyl tRNA synthetases (ArgRS, CysRS, MetRS, and TyrRS) ever found outside of cellular organisms. The discovery that Mimivirus encoded trademark cellular functions prompted a wealth of theoretical studies revisiting the concept of virus and associated large DNA viruses with the emergence of early eukaryotes. However, the evolutionary significance of these unique features remained impossible to assess in absence of a Mimivirus relative exhibiting a suitable evolutionary divergence. Here, we present Megavirus chilensis, a giant virus isolated off the coast of Chile, but capable of replicating in fresh water acanthamoeba. Its 1,259,197-bp genome is the largest viral genome fully sequenced so far. It encodes 1,120 putative proteins, of which 258 (23%) have no Mimivirus homologs. The 594 Megavirus/Mimivirus orthologs share an average of 50% of identical residues. Despite this divergence, Megavirus retained all of the genomic features characteristic of Mimivirus, including its cellular-like genes. Moreover, Megavirus exhibits three additional aminoacyl-tRNA synthetase genes (IleRS, TrpRS, and AsnRS) adding strong support to the previous suggestion that the Mimivirus/Megavirus lineage evolved from an ancestral cellular genome by reductive evolution. The main differences in gene content between Mimivirus and Megavirus genomes are due to (i) lineages specific gains or losses of genes, (ii) lineage specific gene family expansion or deletion, and (iii) the insertion/migration of mobile elements (intron, intein).