Repression of the major immediate early promoter of human cytomegalovirus allows transcription from an alternate promoter
Repression of the major immediate early promoter of human cytomegalovirus allows transcription from an alternate promoter
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抑制人巨细胞病毒的主要立即早期启动子允许从替代启动子进行转录
DOI：
10.1099/jgv.0.001894
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发表时间：
2023
影响因子：
3.8
通讯作者：
Mason R
中科院分区：
文献类型：
--
作者：
Mason R
感染后，人巨细胞病毒（HCMV）基因组迅速与宿主组蛋白相关，这有助于调节病毒基因表达。这在HCMV潜伏期可以清楚地看到，通常负责关键裂解蛋白IE72和IE86表达的主要直接早期启动子（MIEP）的沉默是由组蛋白甲基化和异染色质蛋白1的募集介导的。至关重要的是，这些组蛋白修饰的逆转加上组蛋白乙酰化驱动病毒再激活，这可以被特定的组蛋白乙酰转移酶抑制剂（HATi）阻断。在溶解性感染中，尽管组蛋白去乙酰化酶抑制剂已被证实能增强病毒复制，但HATi的作用尚不清楚。在这里，我们报告了许多不同的广谱作用的HATi在裂解感染期间对病毒感染和复制有轻微的影响，在感染的低多重性中观察到更明显的表型。然而，对主要即刻早期（MIE）基因表达调控的具体分析表明，以p300/CBP为靶点的HATi C646通过抑制MIEP暂时抑制MIE基因表达，但在感染后24小时，MIE基因表达因另一种IE启动子ip2的代偿激活而恢复。这表明沉默MIEP促进了溶解性感染中ip2启动子的活性，与此一致的是，在感染晚期不自动抑制MIEP的重组HCMV感染的细胞中，ip2转录受损。此外，在野生型感染细胞中，已知负责自我抑制的组蛋白甲基转移酶的抑制类似地抑制ip2转录。我们还观察到，MIEP和ip2启动子的这些离散转录活性也反映在再激活中；基本上，在MIEP沉默的细胞中，ip2活性在再激活后的早期更容易检测到，而在MIEP强劲激活的细胞中，ip2转录减少或延迟。最后，我们观察到对树突状细胞中HCMV再激活至关重要的途径的抑制，例如对IL-6的反应，优先对MIEP的激活而不是ip2启动子的激活重要。总之，这些数据增加了HCMV MIE区域内多个启动子的存在可以以细胞类型和配体特异性的方式驱动再激活的假设，也表明两个启动子之间存在相互依赖的调节活性。
Following infection, the human cytomegalovirus (HCMV) genome becomes rapidly associated with host histones which can contribute to the regulation of viral gene expression. This can be seen clearly during HCMV latency where silencing of the major immediate early promoter (MIEP), normally responsible for expression of the key lytic proteins IE72 and IE86, is mediated by histone methylation and recruitment of heterochromatin protein 1. Crucially, reversal of these histone modifications coupled with histone acetylation drives viral reactivation which can be blocked with specific histone acetyltransferase inhibitors (HATi). In lytic infection, a role for HATi is less clear despite the well-established enhancement of viral replication observed with histone deacetylase inhibitors. Here we report that a number of different broad-acting HATi have a minor impact on viral infection and replication during lytic infection with the more overt phenotypes observed at lower multiplicities of infection. However, specific analyses of the regulation of major immediate early (MIE) gene expression reveal that the HATi C646, which targets p300/CBP, transiently repressed MIE gene expression via inhibition of the MIEP but by 24 h post-infection MIE gene expression was rescued due to compensatory activation of an alternative IE promoter, ip2. This suggested that silencing of the MIEP promoted alternative ip2 promoter activity in lytic infection and, consistent with this, ip2 transcription is impaired in cells infected with a recombinant HCMV that does not auto-repress the MIEP at late times of infection. Furthermore, inhibition of the histone methyltransferases known to be responsible for auto-repression is similarly inhibitory to ip2 transcription in wild-type infected cells. We also observe that these discrete transcriptional activities of the MIEP and ip2 promoter are also reflected in reactivation; essentially in cells where the MIEP is silenced, ip2 activity is easier to detect at very early times post-reactivation whereas in cells where robust activation of the MIEP is observed ip2 transcription is reduced or delayed. Finally, we observe that inhibition of pathways demonstrated to be important for reactivation of HCMV in dendritic cells, e.g. in response to IL-6, are preferentially important for activation of the MIEP and not the ip2 promoter. Together, these data add to the hypothesis that the existence of multiple promoters within the MIE region of HCMV can drive reactivation in a cell type- and ligand-specific manner and also suggest that inter-dependent regulatory activity between the two promoters exists.