Herpes Simplex Virus 2 Expresses a Novel Form of ICP34.5, a Major Viral Neurovirulence Factor, through Regulated Alternative Splicing
Herpes Simplex Virus 2 Expresses a Novel Form of ICP34.5, a Major Viral Neurovirulence Factor, through Regulated Alternative Splicing
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DOI：
10.1128/jvi.03500-12
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发表时间：
2013-05-01
影响因子：
5.4
通讯作者：
Krause, Philip R.
中科院分区：
文献类型：
--
作者：
Tang, Shuang;Guo, Nini;Krause, Philip R.
单纯疱疹病毒1型(HSV-1)和单纯疱疹病毒2型(HSV-2)是两种关系密切的嗜神经性人类疱疹病毒，它们通过病毒神经毒力因子ICP34.5实现神经趋向性。在这份报告中，除了全长38 kDa的蛋白(ICP34.5α)外，我们在HSV-2感染的细胞中发现了一种28 kDa的新形式的ICP34.5(ICP34.5 beta)。ICP34.5β由未剪接的ICP34.5 mRNA翻译而来，保留的内含子引入了一个提前终止密码子。因此，ICP34.5β缺乏C末端保守的Gadd34结构域，但包括由内含子编码的19个额外氨基酸。虽然两种HSV-2 ICP34.5蛋白均在核仁中检测到，但ICP34.5α蛋白主要位于胞浆中，而ICP34.5β蛋白主要在细胞核中分布较广。ICP34.5β不能抵消PKR介导的eIF2磷酸化，但不干扰ICP34.5α在此过程中的作用。ICP34.5β在细胞培养中的有效表达取决于病毒感染或ICP27的表达，ICP27是一种多功能的即刻早期基因。ICP27对ICP34.5β蛋白水平的影响归因于其选择性地抑制ICP34.5剪接，导致ICP34.5β蛋白表达增加，而ICP34.5α蛋白水平降低。ICP27的C末端HH3结构域是特异性抑制ICP34.5剪接和促进ICP34.5β表达所必需的，而不是RNA结合域。我们的结果表明，ICP34.5α和ICP34.5β在HSV-2中的表达受到严格调控，可能参与了病毒的致病过程。
Herpes simplex virus 1 (HSV-1) and HSV-2, two closely related neurotropic human herpesviruses, achieve neurotropism through ICP34.5, a major viral neurovirulence factor. In this report, in addition to the full-length 38-kDa protein (ICP34.5 alpha), we identified a 28-kDa novel form of ICP34.5 (ICP34.5 beta) in HSV-2-infected cells. ICP34.5 beta is translated from unspliced ICP34.5 mRNA, with the retained intron introducing a premature stop codon. Thus, ICP34.5 beta lacks the C-terminal conserved GADD34 domain but includes 19 additional amino acids encoded by the intron. Although a fraction of both HSV-2 ICP34.5 proteins are detected in the nucleolus, ICP34.5 alpha is predominantly located in cytoplasm, and ICP34.5 beta is mainly detected more diffusely in the nucleus. ICP34.5 beta is unable to counteract PKR-mediated eIF2 phosphorylation but does not interfere with ICP34.5 alpha's function in this process. Efficient expression of ICP34.5 beta in cell culture assays is dependent on viral infection or expression of ICP27, a multifunctional immediate-early gene. The effect of ICP27 on the ICP34.5 beta protein level is attributed to its selective inhibition of ICP34.5 splicing, which results in increased expression of ICP34.5 beta but a reduced level of ICP34.5 alpha. The C-terminal KH3 domain but not the RNA binding domain of ICP27 is required for its specific inhibition of ICP34.5 splicing and promotion of ICP34.5 beta expression. Our results suggest that the expression of ICP34.5 alpha and ICP34.5 beta is tightly regulated in HSV-2 and likely contributes to viral pathogenesis.