Horion Julie, Gloire Geoffrey, El Mjiyad Nadia, Quivy Vincent, Vermeulen Linda, Vanden Berghe Wim, Haegeman Guy, Van Lint Carine, Piette Jacques, Habraken Yvette
Laboratory of Virology and Immunology, GIGA-R, University of Liège, 4000 Liège, Belgium.
J Biol Chem. 2007 May 25;282(21):15383-93. doi: 10.1074/jbc.M609166200. Epub 2007 Apr 4.
NF-kappaB is a crucial transcription factor tightly regulated by protein interactions and post-translational modifications, like phosphorylation and acetylation. A previous study has shown that trichostatin A (TSA), a histone deacetylase inhibitor, potentiates tumor necrosis factor (TNF) alpha-elicited NF-kappaB activation and delays IkappaBalpha cytoplasmic reappearance. Here, we demonstrated that TSA also prolongs NF-kappaB activation when induced by the insulino-mimetic pervanadate (PV), a tyrosine phosphatase inhibitor that initiates an atypical NF-kappaB signaling. This extension is similarly correlated with delayed IkappaBalpha cytoplasmic reappearance. However, whereas TSA causes a prolonged IKK activity when added to TNFalpha, it does not when added to PV. Instead, quantitative reverse transcriptase-PCR revealed a decrease of ikappabalpha mRNA level after TSA addition to PV stimulation. This synthesis deficit of the inhibitor could explain the sustained NF-kappaB residence in the nucleus. In vivo analysis by chromatin immunoprecipitation assays uncovered that, for PV induction but not for TNFalpha, the presence of TSA provokes several impairments on the ikappabalpha promoter: (i) diminution of RNA Pol II recruitment; (ii) reduced acetylation and phosphorylation of histone H3-Lys(14) and -Ser(10), respectively; (iii) decreased presence of phosphorylated p65-Ser(536); and (iv) reduction of IKKalpha binding. The recruitment of these proteins on the icam-1 promoter, another NF-kappaB-regulated gene, is not equally affected, suggesting a promoter specificity of PV with TSA stimulation. Taken together, these data suggest that TSA acts differently depending on the NF-kappaB pathway and the targeted promoter in question. This indicates that one overall histone deacetylase role is to inhibit NF-kappaB activation by molecular mechanisms specific of the stimulus and the promoter.
核因子-κB（NF-κB）是一种关键的转录因子，受蛋白质相互作用和翻译后修饰（如磷酸化和乙酰化）的严格调控。先前的一项研究表明，组蛋白去乙酰化酶抑制剂曲古抑菌素A（TSA）可增强肿瘤坏死因子（TNF）α诱导的NF-κB激活，并延迟IκBα在细胞质中的重新出现。在此，我们证明，当由胰岛素模拟物过氧钒酸盐（PV，一种引发非典型NF-κB信号传导的酪氨酸磷酸酶抑制剂）诱导时，TSA也会延长NF-κB的激活。这种延长同样与IκBα在细胞质中的重新出现延迟相关。然而，虽然将TSA添加到TNFα中时会导致IKK活性延长，但添加到PV中时则不会。相反，定量逆转录聚合酶链反应显示，在TSA添加到PV刺激后，IκBα mRNA水平降低。抑制剂的这种合成缺陷可以解释NF-κB在细胞核中的持续存在。通过染色质免疫沉淀分析进行的体内分析发现，对于PV诱导而非TNFα诱导，TSA的存在会对IκBα启动子造成多种损害：（i）RNA聚合酶II募集减少；（ii）组蛋白H3-Lys(14)和-Ser(10)的乙酰化和磷酸化分别减少；（iii）磷酸化的p65-Ser(536)的存在减少；以及（iv）IKKα结合减少。这些蛋白质在另一个NF-κB调控基因icam-1启动子上的募集受到的影响并不相同，这表明PV与TSA刺激存在启动子特异性。综上所述，这些数据表明TSA的作用因NF-κB途径和相关的靶向启动子而异。这表明组蛋白去乙酰化酶的一个总体作用是通过特定于刺激和启动子的分子机制来抑制NF-κB激活。
