Henzy Jamie E, Gifford Robert J, Kenaley Christopher P, Johnson Welkin E
Biology Department, Boston College, Chestnut Hill, MA.
MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom.
Mol Biol Evol. 2017 Mar 1;34(3):634-639. doi: 10.1093/molbev/msw262.
We have identified a retroviral envelope gene with a complete, intact open reading frame (ORF) in 20 species of spiny-rayed fishes (Acanthomorpha). The taxonomic distribution of the gene, "percomORF", indicates insertion into the ancestral lineage >110 Ma, making it the oldest known conserved gene of viral origin in a vertebrate genome. Underscoring its ancient provenence, percomORF exists as an isolated ORF within the intron of a widely conserved host gene, with no discernible proviral sequence nearby. Despite its remarkable age, percomORF retains canonical features of a retroviral glycoprotein, and tests for selection strongly suggest cooption for a host function. Retroviral envelope genes have been coopted for a role in placentogenesis by numerous lineages of mammals, including eutherians and marsupials, representing a variety of placental structures. Therefore percomORF's presence within the group Percomorpha-unique among spiny-finned fishes in having evolved placentation and live birth-is especially intriguing.
我们在20种棘鳍鱼类（棘鳍总目）中鉴定出一个具有完整开放阅读框（ORF）的逆转录病毒包膜基因。“鲈形目ORF”基因的分类分布表明其在超过1.1亿年前插入到祖先谱系中，这使其成为脊椎动物基因组中已知最古老的源自病毒的保守基因。“鲈形目ORF”存在于一个广泛保守的宿主基因的内含子中，作为一个孤立的开放阅读框，附近没有可识别的前病毒序列，这突出了其古老的起源。尽管其年代久远，“鲈形目ORF”仍保留了逆转录病毒糖蛋白的典型特征，选择测试强烈表明它已被用于宿主功能。包括真兽类和有袋类在内的许多哺乳动物谱系已将逆转录病毒包膜基因用于胎盘形成，代表了多种胎盘结构。因此，“鲈形目ORF”在鲈形目鱼类中的存在——在棘鳍鱼类中，鲈形目是唯一进化出胎盘和胎生的类群——尤其引人关注。
