Department of Basic Pharmaceutical Sciences, University of Louisiana at Monroe College of Pharmacy, Monroe, LA 71209, USA.
J Neurovirol. 2010 Feb;16(1):13-24. doi: 10.3109/13550280903552412.
Herpes simplex virus type 1 (HSV-1) undergoes acute infection in epithelial cells followed by establishment of latency in the neurons of trigeminal ganglia. The latent virus maintains a dormant state and can recurs spontaneously, suggesting transcriptional silencing and reactivation occur in neurons. Computer data mining identified a nuclear hormone response element (NRE), the binding site for the thyroid hormone receptor (TR) or other nuclear hormone receptor, in the promoter of HSV-1 thymidine kinase (TK). TRs are transcription factors whose activity is dependent on their ligand thyroid hormone (T(3); triiodothyronine). We hypothesize that TR and T(3) exert regulation on HSV-1 gene expression in neurons. A neuroblastoma cell line expressing the TR isoform beta (N2aTRbeta) was utilized for in vitro investigation. Results showed that liganded TR repressed TK promoter activity but unliganded TR relieved the inhibition. The mutagenesis study demonstrated that one nucleotide mutation at the NRE abolished the T(3)/TR-mediated regulation. N2aTRbeta cells treated with T(3) were suppressive to TK expression and virus release but the removal of T(3) de-repressed TK expression and increased virus release, confirmed by reverse transcriptase-polymerase chain reaction (RT-PCR) and plaque assays, respectively. Chromatin immunoprecipitation (ChIP) assays showed that TRs were enriched at TK NRE in the presence of T(3). Additional results demonstrated that hyper acetylated histone H4 and monomethylated H3 modified at lysine 9 (H3K9me1) were enriched at transcriptionally active TK promoters but were dissociated from the NRE by T(3)/TR. These results suggest that T(3) could regulate HSV-1 gene expression through its receptor via histone modification in cultured neuronal cells.
单纯疱疹病毒 1 型（HSV-1）在表皮细胞中急性感染，随后在三叉神经节的神经元中建立潜伏。潜伏病毒保持休眠状态，并可能自发复发，这表明转录沉默和再激活发生在神经元中。计算机数据挖掘在 HSV-1 胸苷激酶（TK）启动子中鉴定出一个核激素反应元件（NRE），该元件是甲状腺激素受体（TR）或其他核激素受体的结合位点。TR 是转录因子，其活性依赖于其配体甲状腺激素（T3；三碘甲状腺原氨酸）。我们假设 TR 和 T3 对神经元中的 HSV-1 基因表达进行调节。利用表达 TR 同工型β的神经母细胞瘤细胞系（N2aTRβ）进行体外研究。结果表明，配体结合的 TR 抑制 TK 启动子活性，但未配体结合的 TR 则解除抑制。突变研究表明，NRE 处的一个核苷酸突变消除了 T3/TR 介导的调节。用 T3 处理的 N2aTRβ细胞对 TK 表达和病毒释放具有抑制作用，但 T3 的去除则使 TK 表达去抑制并增加病毒释放，这分别通过逆转录聚合酶链反应（RT-PCR）和噬菌斑分析得到证实。染色质免疫沉淀（ChIP）分析表明，在存在 T3 的情况下，TR 富集在 TK NRE 处。其他结果表明，组蛋白 H4 高度乙酰化和赖氨酸 9 处单甲基化的 H3（H3K9me1）修饰富集在转录活跃的 TK 启动子上，但 T3/TR 将其从 NRE 上分离。这些结果表明，T3 可通过其受体通过组蛋白修饰在培养的神经元细胞中调节 HSV-1 基因表达。
