Herpes Simplex Virus VP16, but Not ICP0, Is Required To Reduce Histone Occupancy and Enhance Histone Acetylation on Viral Genomes in U2OS Osteosarcoma Cells
Herpes Simplex Virus VP16, but Not ICP0, Is Required To Reduce Histone Occupancy and Enhance Histone Acetylation on Viral Genomes in U2OS Osteosarcoma Cells
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DOI：
10.1128/jvi.01727-09
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发表时间：
2010-02-01
影响因子：
5.4
通讯作者：
Smiley, James R.
中科院分区：
文献类型：
--
作者：
Hancock, Meaghan H.;Cliffe, Anna R.;Smiley, James R.
单纯疱疹病毒（HSV）基因组注射到宿主细胞核后迅速与组蛋白结合。病毒蛋白ICP 0和VP 16是有效的病毒基因表达所必需的，并且已经涉及降低病毒基因组上乙酰化不足的组蛋白的水平，提高了高水平的乙酰化不足的组蛋白抑制病毒基因表达的可能性。U2 OS骨肉瘤细胞系允许ICP 0和VP 16突变体的复制，并且似乎缺乏存在于其他细胞类型中的先天性抗病毒抑制机制。因此，我们使用染色质免疫沉淀来确定U2 OS细胞是否有能力将组蛋白加载到HSV DNA上，如果是这样，是否需要ICP 0和/或VP 16来减少组蛋白占用并增强这种细胞类型中的乙酰化。在没有VP 16激活功能的情况下，高水平的乙酰化不足的组蛋白H3在病毒基因组上的几个位置积累;相反，ICP 0突变体显示出明显降低的组蛋白水平和增强的乙酰化，类似于野生型HSV。这些结果表明，U2 OS细胞能够将乙酰化不足的组蛋白装载到HSV DNA上，并揭示了VP 16在病毒早期和晚期基因座调节染色质结构中的意想不到的作用。对这些发现的一种解释是，ICP 0和VP 16通过不同的途径影响病毒染色质结构，而ICP 0靶向的途径在U2 OS细胞中存在缺陷。我们还表明，HSV感染导致细胞基因组内一些活跃转录基因的组蛋白水平降低，表明病毒感染改变了细胞染色质结构。
The herpes simplex virus (HSV) genome rapidly becomes associated with histones after injection into the host cell nucleus. The viral proteins ICP0 and VP16 are required for efficient viral gene expression and have been implicated in reducing the levels of underacetylated histones on the viral genome, raising the possibility that high levels of underacetylated histones inhibit viral gene expression. The U2OS osteosarcoma cell line is permissive for replication of ICP0 and VP16 mutants and appears to lack an innate antiviral repression mechanism present in other cell types. We therefore used chromatin immunoprecipitation to determine whether U2OS cells are competent to load histones onto HSV DNA and, if so, whether ICP0 and/or VP16 are required to reduce histone occupancy and enhance acetylation in this cell type. High levels of underacetylated histone H3 accumulated at several locations on the viral genome in the absence of VP16 activation function; in contrast, an ICP0 mutant displayed markedly reduced histone levels and enhanced acetylation, similar to wild-type HSV. These results demonstrate that U2OS cells are competent to load underacetylated histones onto HSV DNA and uncover an unexpected role for VP16 in modulating chromatin structure at viral early and late loci. One interpretation of these findings is that ICP0 and VP16 affect viral chromatin structure through separate pathways, and the pathway targeted by ICP0 is defective in U2OS cells. We also show that HSV infection results in decreased histone levels on some actively transcribed genes within the cellular genome, demonstrating that viral infection alters cellular chromatin structure.