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J Virol:中科院科学家揭示致瘤疱疹病毒形态学发生机制

来源:生物谷 2015-03-09 13:40

2015年3月9日讯 /生物谷BIOON/--2015年2月25日,中科院生物物理所邓红雨课题组在国际权威期刊J Virol在线发表了名为“Tegument protein ORF33 of a gammaherpesvirus is associated with intranuclear capsids at an early stage of tegumentation process”的研究论文,报道了间质蛋白ORF33在细胞核内就可以结合到病毒颗粒上的生物学现象。

人γ疱疹病毒因能够引发恶性肿瘤而被称为致瘤疱疹病毒。众所周知,病毒裂解期复制对其致病性至关重要。而病毒颗粒形态发生和释放是病毒裂解期复制的一个必要步骤。疱疹病毒具由内向外依次为病毒基因组、衣壳、间质蛋白层和囊膜的四层结构,其中间质是疱疹病毒的独特结构,包含多种间质蛋白。疱疹病毒的形态发生是从细胞核内开始进行的,经过初级囊膜化,突破内核膜,进入核周质,然后经过去囊膜化,突破外核膜,进入细胞质,在细胞质中获得大部分病毒结构蛋白,并借助细胞内的小泡系统运输到细胞膜,最终以成熟病毒颗粒的形式释放到细胞外。间质蛋白作为连接核衣壳和囊膜的结构成分,在疱疹病毒的包装释放过程中起关键作用。然而到目前为止,关于间质蛋白能否在病毒颗粒出核膜之前就可以结合到病毒颗粒上并发挥生物学功能,还尚未明了。ORF33是疱疹病毒家族中保守的一种间质蛋白。邓红雨课题组的前期研究发现,ORF33对病毒形态发生是必需的,并且在病毒颗粒核释放和间质化过程中起双重作用(Guo et al., J Virol, 2009)。为了进一步揭示ORF33参与病毒形态发生的分子机理,研究人员综合利用生物化学和生物成像等多种技术手段,发现ORF33最早在细胞核内就可以结合到病毒颗粒上,有力证明了间质化最早在病毒出核膜前就可以发生。(生物谷Bioon.com)

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生物谷推荐的英文摘要:

J. Virol. doi:10.1128/JVI.00079-15

Tegument protein ORF33 of a gammaherpesvirus is associated with intranuclear capsids at an early stage of tegumentation process.

Shen S, Jia X, Guo H, Deng H

Herpesvirus nascent capsids, after assembly in the nucleus, must acquire a variety of tegument proteins during maturation. However, little is known about the identity of the tegument proteins that are associated with capsids in the nucleus or the molecular mechanisms involved in nuclear egress of capsids into cytoplasm, especially for the two human gammaherpesviruses, Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV), due to lack of efficient lytic replication systems. Murine gammaherpesvirus 68 (MHV-68) is genetically related to human gammaherpesviruses and serves as an excellent model to study de novo lytic replication of gammaherpesviruses. We have previously shown that open reading frame 33 (ORF33) of MHV-68 is a tegument protein of mature virions and is essential for virion assembly and egress. However, it remained unclear how ORF33 is incorporated into virions. In this study, we first showed that the endogenous ORF33 protein co-localizes with capsid proteins at discrete areas in the nucleus during viral infection. Co-sedimentation analysis as well as immunoprecipitation assay demonstrated that ORF33 is associated with both nuclear and cytoplasmic capsids. Immunogold labeling experiment using an anti-ORF33 monoclonal antibody revealed that ORF33-rich areas in the nucleus are surrounded by immature capsids. Moreover, ORF33 is associated with nucleocapsids prior to primary envelopment as well as with mature virions in the cytoplasm. Finally, we showed that ORF33 interacts with two capsid proteins, suggesting that nucleocapsids may interact with ORF33 in a direct manner. In summary, we identified ORF33 as a tegument protein that is associated with intranuclear capsids prior to primary envelopment, likely through interacting with capsid proteins in a direct manner.

IMPORTANCE:

Morphogenesis is an essential step in virus propagation that leads to the generation of progeny virions. For herpesviruses, this is a complicated process that starts in the nucleus. Although capsid assembly and genome packaging is relatively well understood, how capsids acquire tegument (the layer between capsid and envelope in a herpesvirion) and whether the initial tegumentation process takes place in the nucleus remain unclear. We previously showed that ORF33 of MHV-68 is a tegument protein and functions both in the nuclear egress of capsids and final virion maturation in the cytoplasm. In the present study, we showed that ORF33 is associated with intranuclear capsids prior to primary envelopment and identified novel interactions between ORF33 and two capsid proteins. Our work provides new insights into the association between tegument proteins and nucleocapsids an early stage of virion maturation process for herpesviruses.

 

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