Phylogenetic analysis of the large family of poxvirus ankyrin-repeat proteins reveals orthologue groups within and across chordopoxvirus genera

Abstract

Ankyrin-repeat (ANK) protein-interaction domains are common in cellular proteins but are relatively rare in viruses. Chordopoxviruses, however, encode a large number of ANK domaincontaining ORFs of largely unknown function. Recently, a second protein-interaction domain, an F-box-like motif, was identified in several poxvirus ANK proteins. Cellular F-box proteins recruit substrates to the ubiquitination machinery of the cell, a putative function for ANK/poxviral F-box proteins. Using publicly available genome sequence data we examined all 328 predicted ANK proteins encoded by 27 chordopoxviruses that represented the eight vertebrate poxvirus genera whose members encode ANK proteins. Within these we identified 15 putative ANK protein orthologue groups within orthopoxviruses, five within parapoxviruses, 23 within avipoxviruses and seven across members of the genera Leporipoxvirus, Capripoxvirus, Yatapoxvirus, Suipoxvirus and Cervidpoxvirus. Sequence comparisons showed that members of each of these four clusters of orthologues were not closely related to members of any of the other clusters. Of these ORFs, 67 % encoded a C-terminal poxviral F-box-like motif, whose absence could largely be attributed to fragmentation of ORFs. Our findings suggest that the large family of poxvirus ANK proteins arose by extensive gene duplication and divergence that occurred independently in four major genus-based groups after the groups diverged from each other. It seems likely that the ancestor ANK proteins of poxviruses contained both the N-terminal ANK repeats and a C-terminal F-box-like domain, with the latter domain subsequently being lost in a small subset of these proteins. INTRODUCTIONChordopoxviruses, a diverse subfamily of the family Poxviridae of DNA viruses, infect a wide range of vertebrates (Moss, 2007). Terminal regions of their large linear genomes typically encode host regulating factors and multiple ankyrin-repeat (ANK) proteins (Damon, 2007). The ANK protein-interaction domain consists of two or more ankyrin motifs and is frequently found in cellular proteins, but relatively rarely in virally encoded proteins, with chordopoxviruses a notable exception (Bork, 1993;Li et al., 2006;Mosavi et al., 2004).The only classified chordopoxvirus not encoding ANK proteins is molluscum contagiosum virus, the sole member of the genus Molluscipoxvirus. Poxviruses of the remaining eight genera each encode numerous ANK proteins (Afonso et al., 2000(Afonso et al., , 2005 Cameron et al., 1999;Chen et al., 2003;Delhon et al., 2004;Gubser & Smith, 2002;Tulman et al., 2001Tulman et al., , 2002Tulman et al., , 2004Tulman et al., , 2006. Specific ANK proteins of cowpox virus (CPX), vaccinia virus (VACV) and myxoma virus (MYXV) have been shown to affect the viruses' host range and virulence, but the functions of the vast majority of poxvirus ANK proteins remain unknown (Bradley & Terajima, 2005;Hsiao et al., 2004 Hsiao et al., , 2006Perkus et al., 1990;Ramsey-Ewing & Moss, 1996). Recently, a second proteininteraction domain, a truncated F-b...

Genetic Screen of a Mutant Poxvirus Library Identifies an Ankyrin Repeat Protein Involved in Blocking Induction of Avian Type I Interferon

“…They also recognized that the expansion of the ANK genes in avipoxviruses is a "particularly clear example of such adaptive gene expansions" and, moreover, that it represents "an exceptional example" whereby multiple functional variants have been generated so that the accordion has not collapsed to a single copy. Our demonstration that fpv012 and cnpv030, which are an orthologous pair (41), share the ability to block induction of avian IFN-␤ provides a strong indication that ANK gene expansion in the avipoxviruses predates speciation of FWPV and CNPV, particularly as fpv012 and cnpv030 are far from basal to the avipoxvirus ANK phylogenetic tree (see the supplemental figure of Sonnberg et al [41]). Expansion of such a large complement of related genes to the extent seen for this viral gene accordion might initially have facilitated high-level expression of inhibitors of a limited number of targets by a gene dosage effect (59).…”

Orf128蛋白在调节nf-Kb活化和逃逸宿主免疫的作用机制*

“…【摘要】 通过分析羊口疮病毒 ORF128 蛋白在 NF-κB 信号通路中的作用机制来阐明 ORF128 蛋白是否是 ORFV 逃避宿主免疫 应答的重要蛋白，这对了解 ORFV 致病机制、理解宿主与病毒之间的抗病毒和抗病毒抑制的关系有重要的意义，为 ORFV 新 型抗病毒药物和疫苗的研制奠定了理论基础。 【关键词】羊口疮病毒；ORF128 蛋白；NF-κB "羊口疮"，是由痘病毒科脊椎动物痘病毒亚科，副痘病毒属的羊口疮病毒（Orf virus，ORFV）引起 的，在感染初期，ORFV 引起的病毒通过多个囊膜蛋白与细胞膜表面的信号传导和肌动蛋白重排相关分子 以 pH-依赖的方式融合，通过细胞内吞作用进入宿主细胞，在胞浆中完成病毒全部的增殖过程 [1] 。为在宿 主细胞中进行复制，病毒会主动采取多种策略，以逃避宿主的免疫应答 [2][3] 。与此同时，被感染的宿主细胞 通过活化抗病毒信号和炎症反应通路 [4] ， 来激活相应的免疫应答， 以阻止病毒的复制， 其中核因子κB （NF-κB）在炎症信号和免疫激活中起着至关重要的作用 [5] 。通过对 ORFV 全基因组分析发现：ORFV 编码具有 [5,14] 。NF-κB 活化形式主要是以 P50 或 P52 与 P65 亚基的结合为 主。在 NF-κB 活化状态下，NF-κB 二聚体（如 p65/p50）与 IκB 结合，这三者的晶体衍射结构表明在 I κ B 、NF-κB 、 ANK 之间有多个结合位点 [15] 。在正常的 NF-κB 信号通路中，例如在 TNF-α治疗中，受体 的活化发送胞内信号激活 IKK 复合物 [5] 。然后激活的 IKK 再磷酸化 IκBα复合物的 Ser32 和 Ser36 位点， 导致 IκBα在 48 位 Lys 泛素化，在此泛素复合物中包含有 F-Box 蛋白和βTrCP。IκBα磷酸化和泛素化 降解，有效地释放出了 NF-κB 二聚体。然后该二聚体游走至核内，与特定基因的启动子序列结合，通过 特异的κB 共有序列的识别提高基因的转录 [16] 。 几乎所有脊椎动物痘病毒都编码 ANK 蛋白，这类蛋白质数量众多，形成了一个大的家族 [17] 。这些蛋 白由大量的 ANK 基序组成，并在许多真核细胞中，介导蛋白-蛋白间的相互作用 [18] 。痘病毒编码的所有锚 蛋白在结构上是相似的， 并具有推断的多个 N 末端的 ANK 基序和 1 个 F-Box 样的 C 末端结构域。 这种 ANK 基序都存在于许多细胞蛋白，包括（NF-κB）结合蛋白中，可调节 NF-κB 信号途径 [19] 。但目前有关 ORFV…”

Innate immune activation of NFκB and its antagonism by poxviruses

“…All chordopoxviruses (with the notable exception of MCV and Crocodilepox virus) encode a family of proteins with multiple ankyrin repeats which, like the bcl-2 protein family described above, are involved in host-range and immunomodulation [25]. Some of these have also been shown to directly target NFkB, possibly by mimicking the ankyrin-repeats of the IkB family, which normally directly mediate the interaction of host IkB proteins with the nuclear localization sequence of p65 and the dimerization domains of both p50 and p65 [26,27].…”