原虫门(巴姆福德维拉王国,realmVaridnavria)是多种病毒的广泛组合,其双链DNA基因组相对较短(<50kbp),产生由双果冻卷主要衣壳蛋白构建的二十面体衣壳。前质粒病毒感染来自所有细胞域的宿主,证明了它们的古老起源,and,特别是,与七个真核生物超群中的六个相关。前质粒病毒包括四大类病毒,即,Polinton,类病毒(PLV),virophages,和腺病毒。我们使用蛋白质结构建模和分析表明,蛋白质引发的DNA聚合酶(pPolBs),virophages,和胞质线性质粒包含与原核PRD1样技术和真核腺病毒的末端蛋白(TP)同源的N末端结构域,这些蛋白参与蛋白引发的复制起始,其次是病毒性卵巢肿瘤样半胱氨酸去泛素化酶(vOTU)域。vOTU结构域可能负责从大型pPolB多肽中裂解TP,并在腺病毒中失活,其中TP是一种单独的蛋白质。许多PLV和transpovirons编码Polinton样pPolB的独特衍生物,保留了TP,vOTU,和pPolB聚合棕榈结构域,但缺乏外切核酸酶结构域,而是包含超家族1解旋酶结构域。对真核前质粒病毒中vOTU结构域的存在/不存在和失活以及用其他DNA聚合酶替换pPolB的分析使我们能够概述其起源和进化的完整方案。
The phylum Preplasmiviricota (kingdom Bamfordvirae, realm Varidnaviria) is a broad assemblage of diverse viruses with comparatively short double-stranded DNA genomes (<50 kbp) that produce icosahedral capsids built from double jelly-roll major capsid proteins. Preplasmiviricots infect hosts from all cellular domains, testifying to their ancient origin, and, in particular, are associated with six of the seven supergroups of eukaryotes. Preplasmiviricots comprise four major groups of viruses, namely, polintons, polinton-like viruses (PLVs), virophages, and adenovirids. We used protein structure modeling and analysis to show that protein-primed DNA polymerases (pPolBs) of polintons, virophages, and cytoplasmic linear plasmids encompass an N-terminal domain homologous to the terminal proteins (TPs) of prokaryotic PRD1-like tectivirids and eukaryotic adenovirids that are involved in protein-primed replication initiation, followed by a viral ovarian tumor-like cysteine deubiquitinylase (vOTU) domain. The vOTU domain is likely responsible for the cleavage of the TP from the large pPolB polypeptide and is inactivated in adenovirids, in which TP is a separate protein. Many PLVs and transpovirons encode a distinct derivative of polinton-like pPolB that retains the TP, vOTU, and pPolB polymerization palm domains but lacks the exonuclease domain and instead contains a superfamily 1 helicase domain. Analysis of the presence/absence and inactivation of the vOTU domains and replacement of pPolB with other DNA polymerases in eukaryotic preplasmiviricots enabled us to outline a complete scenario for their origin and evolution.