An important site for bovine herpesvirus 1 (BoHV-1) latency is sensory neurons within trigeminal ganglia (TG). The synthetic corticosteroid dexamethasone consistently induces BoHV-1 reactivation from latency. Expression of four Krüppel-like transcription factors (KLF), i.e., KLF4, KLF6, PLZF (promyelocytic leukemia zinc finger), and KLF15, are induced in TG neurons early during dexamethasone-induced reactivation. The glucocorticoid receptor (GR) and KLF15 form a feed-forward transcription loop that cooperatively transactivates the BoHV-1 immediate early transcription unit 1 (IEtu1) promoter that drives bovine infected cell protein 0 (bICP0) and bICP4 expression. Since the bICP0 gene also contains a separate early (E) promoter, we tested the hypothesis that GR and KLF family members transactivate the bICP0 E promoter. GR and KLF4, both pioneer transcription factors, cooperated to stimulate bICP0 E promoter activity in a ligand-independent manner in mouse neuroblastoma cells (Neuro-2A). Furthermore, GR and KLF4 stimulated productive infection. Mutating both half GR binding sites did not significantly reduce GR- and KLF4-mediated transactivation of the bICP0 E promoter, suggesting that a novel mechanism exists for transactivation. GR and KLF15 cooperatively stimulated bICP0 activity less efficiently than GR and KL4: however, KLF6, PLZF, and GR had little effect on the bICP0 E promoter. GR, KLF4, and KLF15 occupied bICP0 E promoter sequences in transfected Neuro-2A cells. GR and KLF15, but not KLF4, occupied the bICP0 E promoter at late times during productive infection of bovine cells. Collectively, these studies suggest that cooperative transactivation of the bICP0 E promoter by two pioneer transcription factors (GR and KLF4) correlates with stimulating lytic cycle viral gene expression following stressful stimuli.IMPORTANCE Bovine herpesvirus 1 (BoHV-1), an important bovine pathogen, establishes lifelong latency in sensory neurons. Reactivation from latency is consistently induced by the synthetic corticosteroid dexamethasone. We predict that increased corticosteroid levels activate the glucocorticoid receptor (GR). Consequently, viral gene expression is stimulated by the activated GR. The immediate early transcription unit 1 promoter (IEtu1) drives expression of two viral transcriptional regulatory proteins, bovine infected cell protein 0 (bICP0) and bICP4. Interestingly, a separate early promoter also drives bICP0 expression. Two pioneer transcription factors, GR and Krüppel-like transcription factor 4 (KLF4), cooperatively transactivate the bICP0 early (E) promoter. GR and KLF15 cooperate to stimulate bICP0 E promoter activity but significantly less than GR and KLF4. The bICP0 E promoter contains enhancer-like domains necessary for GR- and KLF4-mediated transactivation that are distinct from those for GR and KLF15. Stress-induced pioneer transcription factors are proposed to activate key viral promoters, including the bICP0 E promoter, during early stages of reactivation from latency.

中文翻译：

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两种先驱转录因子，如Krüppel转录因子4和糖皮质激素受体，可协同激活牛疱疹病毒1 ICP0早期启动子并刺激生产性感染。

牛疱疹病毒1（BoHV-1）潜伏期的重要部位是三叉神经节（TG）中的感觉神经元。合成的皮质类固醇地塞米松可从潜伏期持续诱导BoHV-1重新激活。在地塞米松诱导的激活早期，TG神经元中诱导了四个Krüppel样转录因子（KLF），即KLF4，KLF6，PLZF（早幼粒细胞白血病锌指）和KLF15的表达。糖皮质激素受体（GR）和KLF15形成前馈转录环，该环协同激活BoHV-1立即早期转录单位1（IEtu1）启动子，该启动子驱动牛感染的细胞蛋白0（bICP0）和bICP4表达。由于bICP0基因还包含一个单独的早期（E）启动子，因此我们测试了GR和KLF家族成员激活bICP0 E启动子的假说。GR和KLF4，两种先驱转录因子均以不依赖配体的方式在小鼠神经母细胞瘤细胞（Neuro-2A）中协同刺激bICP0 E启动子活性。此外，GR和KLF4刺激了生产性感染。突变两个半个GR结合位点不会显着减少bICP0 E启动子的GR和KLF4介导的反式激活，这表明反式激活存在新的机制。GR和KLF15协同刺激bICP0活性的效率低于GR和KL4：但是，KLF6，PLZF和GR对bICP0 E启动子的影响很小。GR，KLF4和KLF15在转染的Neuro-2A细胞中占据了bICP0 E启动子序列。GR和KLF15，而不是KLF4，在生产性感染牛细胞的后期占据了bICP0 E启动子。总的来说，这些研究表明，在应激刺激后，两个先驱转录因子（GR和KLF4）对bICP0 E启动子的协同反式激活与刺激裂解周期病毒基因的表达有关。感觉神经元的潜伏期。合成皮质类固醇地塞米松持续诱导潜伏期恢复。我们预测皮质类固醇水平升高会激活糖皮质激素受体（GR）。因此，活化的GR刺激病毒基因表达。立即早期转录单元1启动子（IEtu1）驱动两种病毒转录调节蛋白的表达，牛感染的细胞蛋白0（bICP0）和bICP4。有趣的是，一个单独的早期启动子也驱动bICP0表达。两个先驱转录因子GR和Krüppel样转录因子4（KLF4）协同激活bICP0早期（E）启动子。GR和KLF15协同刺激bICP0 E启动子活性，但明显低于GR和KLF4。bICP0 E启动子包含GR和KLF4介导的反式激活所必需的增强子样结构域，与GR和KLF15不同。提出了应激诱导的先锋转录因子，以在从潜伏期重新激活的早期阶段激活关键的病毒启动子，包括bICP0 E启动子。bICP0 E启动子包含GR和KLF4介导的反式激活所必需的增强子样结构域，与GR和KLF15不同。提出了应激诱导的先锋转录因子，以在从潜伏期重新激活的早期阶段激活关键的病毒启动子，包括bICP0 E启动子。bICP0 E启动子包含GR和KLF4介导的反式激活所必需的增强子样结构域，与GR和KLF15不同。提出了应激诱导的先锋转录因子，以在从潜伏期重新激活的早期阶段激活关键的病毒启动子，包括bICP0 E启动子。