Arrangement of L2 within the papillomavirus capsid
Arrangement of L2 within the papillomavirus capsid
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DOI：
10.1128/jvi.02726-07
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发表时间：
2008-06-01
影响因子：
5.4
通讯作者：
Trus, Benes L.
中科院分区：
文献类型：
--
作者：
Buck, Christopher B.;Cheng, Naiqian;Trus, Benes L.
乳头瘤病毒是一类无包膜DNA肿瘤病毒。一些性传播的人乳头瘤病毒（HPV）类型，包括HPV 16型（HPV 16），会导致子宫颈癌。乳头瘤病毒编码两种衣壳蛋白，L1和L2。主要衣壳蛋白L1可以自发地组装成72-五聚体二十面体结构，其非常类似于天然病毒体。虽然次要衣壳蛋白L2不是衣壳形成所必需的，但认为其参与病毒基因组的衣壳化，并在病毒感染性进入途径中发挥许多重要作用。L2的丰度及其在病毒粒子内的排列仍不清楚。为了解决这些问题，我们开发了在培养的人细胞系中连续繁殖感染性HPV 16衣壳（假病毒）的方法。对使用各种方法产生的衣壳制剂的生化分析表明，每个衣壳可以掺入多达72个L2分子。冷冻电子显微镜和图像重建分析纯化的衣壳揭示了二十面体有序的U-特定的密度下的轴向管腔的每个L1壳粒。这些L2密度按钮彼此相对接近，提高了组装的病毒体内同型L2相互作用的可能性。使用双分子荧光互补或“分裂GFP”技术支持相邻L2分子的N和C末端可以在衣壳内紧密并置的概念。这一结构信息应有助于调查L2的功能，在装配和进入阶段的乳头瘤病毒的生命周期。
Papillomaviruses are a family of nonenveloped DNA tumor viruses. Some sexually transmitted human papillomavirus (HPV) types, including HPV type 16 (HPV16), cause cancer of the uterine cervix. Papillomaviruses encode two capsid proteins, L1 and L2. The major capsid protein, L1, can assemble spontaneously into a 72-pentamer icosahedral structure that closely resembles native virions. Although the minor capsid protein, L2, is not required for capsid formation, it is thought to participate in encapsidation of the viral genome and plays a number of essential roles in the viral infectious entry pathway. The abundance of L2 and its arrangement within the virion remain unclear. To address these questions, we developed methods for serial propagation of infectious HPV16 capsids (pseudoviruses) in cultured human cell lines. Biochemical analysis of capsid preparations produced using various methods showed that up to 72 molecules of L2 can be incorporated per capsid. Cryoelectron microscopy and image reconstruction analysis of purified capsids revealed an icosahedrally ordered U-specific density beneath the axial lumen of each L1 capsomer. The relatively close proximity of these L2 density buttons to one another raised the possibility of homotypic L2 interactions within assembled virions. The concept that the N and C termini of neighboring L2 molecules can be closely apposed within the capsid was supported using bimolecular fluorescence complementation or "split GFP" technology. This structural information should facilitate investigation of L2 function during the assembly and entry phases of the papillomavirus life cycle.