Ruboyianes Ryan, Worobey Michael
Department of Ecology and Evolutionary Biology, University of Arizona, 1041 E Lowell St., Tucson, AZ 85721, USA.
Virus Evol. 2016 Oct 30;2(2):vew032. doi: 10.1093/ve/vew032. eCollection 2016 Jul.
Recent discoveries indicate that the foamy virus (FV) () ancestor may have been among the first retroviruses to appear during the evolution of vertebrates, demonstrated by foamy endogenous retroviruses present within deeply divergent hosts including mammals, coelacanth, and ray-finned fish. If they indeed existed in ancient marine environments hundreds of millions of years ago, significant undiscovered diversity of foamy-like endogenous retroviruses might be present in fish genomes. By screening published genomes and by applying PCR-based assays of preserved tissues, we discovered 23 novel foamy-like elements in teleost hosts. These viruses form a robust, reciprocally monophyletic sister clade with sarcopterygian host FV, with class III mammal endogenous retroviruses being the sister group to both clades. Some of these foamy-like retroviruses have larger genomes than any known retrovirus, exogenous or endogenous, due to unusually long -like genes and numerous accessory genes. The presence of genetic features conserved between mammalian FV and these novel retroviruses attests to a foamy-like replication biology conserved for hundreds of millions of years. We estimate that some of these viruses integrated recently into host genomes; exogenous forms of these viruses may still circulate.
最近的发现表明，泡沫病毒（FV）的祖先可能是脊椎动物进化过程中最早出现的逆转录病毒之一，这一点可由存在于包括哺乳动物、腔棘鱼和硬骨鱼等亲缘关系甚远的宿主中的泡沫内源性逆转录病毒证明。如果它们确实在数亿年前就存在于古代海洋环境中，那么鱼类基因组中可能存在大量未被发现的类似泡沫的内源性逆转录病毒多样性。通过筛选已发表的基因组并对保存的组织进行基于PCR的检测，我们在硬骨鱼宿主中发现了23种新的类似泡沫的元件。这些病毒与肉鳍鱼宿主FV形成了一个强大的、相互单系的姐妹分支，III类哺乳动物内源性逆转录病毒是这两个分支的姐妹群。由于存在异常长的类似基因和众多辅助基因，这些类似泡沫的逆转录病毒中的一些具有比任何已知的逆转录病毒（无论是外源性还是内源性）更大的基因组。哺乳动物FV与这些新型逆转录病毒之间保守的遗传特征的存在证明了一种类似泡沫的复制生物学已经保存了数亿年。我们估计这些病毒中的一些最近才整合到宿主基因组中；这些病毒的外源性形式可能仍在传播。
