Reyda Sabine, Tenzer Stefan, Navarro Pedro, Gebauer Wolfgang, Saur Michael, Krauter Steffi, Büscher Nicole, Plachter Bodo
Institute for Virology, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany.
Institute for Immunology, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany Research Center Immunology, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany.
J Virol. 2014 Sep 1;88(17):9633-46. doi: 10.1128/JVI.01415-14. Epub 2014 Jun 11.
The mechanisms that lead to the tegumentation of herpesviral particles are only poorly defined. The phosphoprotein 65 (pp65) is the most abundant constituent of the virion tegument of human cytomegalovirus (HCMV). It is, however, nonessential for virion formation. This seeming discrepancy has not met with a satisfactory explanation regarding the role of pp65 in HCMV particle morphogenesis. Here, we addressed the question of how the overall tegument composition of the HCMV virion depended on pp65 and how the lack of pp65 influenced the packaging of particular tegument proteins. To investigate this, we analyzed the proteomes of pp65-positive (pp65pos) and pp65-negative (pp65neg) virions by label-free quantitative mass spectrometry and determined the relative abundances of tegument proteins. Surprisingly, only pUL35 was elevated in pp65neg virions. As the abundance of pUL35 in the HCMV tegument is low, it is unlikely that it replaced pp65 as a structural component in pp65neg virions. A subset of proteins, including the third most abundant tegument protein, pUL25, as well as pUL43, pUL45, and pUL71, were reduced in pp65neg or pp65low virions, indicating that the packaging of these proteins was related to pp65. The levels of tegument components, like pp28 and the capsid-associated tegument proteins pp150, pUL48, and pUL47, were unaffected by the lack of pp65. Our analyses demonstrate that deletion of pp65 is not compensated for by other viral proteins in the process of virion tegumentation. The results are concordant with a model of pp65 serving as an optional scaffold protein that facilitates protein upload into the outer tegument of HCMV particles.
The assembly of the tegument of herpesviruses is only poorly understood. Particular proteins, like HCMV pp65, are abundant tegument constituents. pp65 is thus considered to play a major role in tegument assembly in the process of virion morphogenesis. We show here that deletion of the pp65 gene leads to reduced packaging of a subset of viral proteins, indicating that pp65 acts as an optional scaffold protein mediating protein upload into the tegument.
导致疱疹病毒颗粒被膜形成的机制目前还不清楚。磷蛋白65（pp65）是人类巨细胞病毒（HCMV）病毒体被膜中含量最丰富的成分。然而，它对于病毒体的形成并非必需。关于pp65在HCMV颗粒形态发生中的作用，这种明显的差异尚未得到令人满意的解释。在这里，我们探讨了HCMV病毒体的整体被膜组成如何依赖于pp65，以及缺乏pp65如何影响特定被膜蛋白的包装。为了研究这一点，我们通过无标记定量质谱分析了pp65阳性（pp65pos）和pp65阴性（pp65neg）病毒体的蛋白质组，并确定了被膜蛋白的相对丰度。令人惊讶的是，只有pUL35在pp65neg病毒体中升高。由于pUL35在HCMV被膜中的丰度较低，它不太可能在pp65neg病毒体中取代pp65作为结构成分。包括第三丰富的被膜蛋白pUL25以及pUL43、pUL45和pUL71在内的一部分蛋白质在pp65neg或pp65低病毒体中减少，表明这些蛋白质的包装与pp65有关。被膜成分如pp28以及衣壳相关被膜蛋白pp150、pUL48和pUL47的水平不受缺乏pp65的影响。我们的分析表明，在病毒体被膜形成过程中，pp65的缺失不能被其他病毒蛋白所补偿。这些结果与pp65作为一种可选的支架蛋白促进蛋白质上传到HCMV颗粒外被膜的模型一致。
疱疹病毒被膜的组装目前了解甚少。特定的蛋白质，如HCMV pp65，是丰富的被膜成分。因此，pp65被认为在病毒体形态发生过程中的被膜组装中起主要作用。我们在这里表明，pp65基因的缺失导致一部分病毒蛋白的包装减少，表明pp65作为一种可选的支架蛋白介导蛋白质上传到被膜中。
