Primary activation of interferon A and interferon B gene transcription by interferon regulatory factor 3
Primary activation of interferon A and interferon B gene transcription by interferon regulatory factor 3
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DOI：
10.1073/pnas.95.17.9837
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发表时间：
1998-08-18
影响因子：
11.1
通讯作者：
Pitha, PM
中科院分区：
文献类型：
--
作者：
Juang, YT;Lowther, W;Pitha, PM
干扰素调节因子家族编码DNA结合转录因子，其中一些转录因子作为病毒诱导信号的调节器发挥作用。IRF-3基因在许多组织和细胞类型中都有结构性表达，病毒感染和干扰素处理都不能促进其转录。然而，在感染细胞中，IRF-3蛋白在羧基末端被磷酸化，这有助于其与CBP/p300共激活子的结合。在目前的研究中，我们证明了IRF-3的过表达显著增强了病毒介导的感染细胞中IFNA和IFNB基因的转录以及干扰素的合成。IRF-3介导的干扰素基因的激活部分依赖于一簇Ser/Thr残基的羧基末端磷酸化，因为带有Ser/Thr到Ala替换的突变体激活干扰素启动子的效率较低。然而，单独在人2FTGH细胞中过表达IRF-3会导致抗病毒状态的诱导，这依赖于功能上的干扰素信号，因为IRF-3不会在JAK-1或P48功能缺陷的突变2FTGH细胞中诱导抗病毒状态；也不能在缺乏IFNA和IFNB基因的Vero细胞中证明IRF-3的抗病毒作用。这一发现表明，在2FTGH细胞中观察到的IRF-3的抗病毒活性主要是通过诱导IFN来实现的。此外，在瞬时表达实验中，E1a蛋白抑制了IRF-3介导的对IFNA4启动子的刺激；这种抑制可以被CBP/p300的过度表达部分逆转，而不结合p300的E1a突变体不表现出这种抑制作用。这些结果表明，IRF-3和CBP/p300是病毒诱导的刺激1型干扰素基因转录的复合体的组成部分。腺病毒E1a拮抗IRF-3介导的激活，提示E1a和IRF-3可能竞争结合CBP/p300，这可能是腺病毒克服干扰素途径抗病毒作用的一种新机制。
The family of interferon (IFN) regulatory factors (IRFs) encodes DNA-binding transcription factors, some of which function as modulators of virus-induced signaling. The IRF-3 gene is constitutively expressed in many tissues and cell types, and neither virus infection nor IFN treatment enhances its transcription. In infected cells, however, IRF-3 protein is phosphorylated at the carboxyl terminus, which facilitates its binding to the CBP/p300 coactivator. In the present study, we demonstrate that overexpression of IRF-3 significantly enhances virus-mediated transcription of the IFNA and IFNB genes in infected cells as well as IFN synthesis. IRF-3-mediated activation of IFN genes depends in part on carboxyl-terminal phosphorylation of a cluster of Ser/Thr residues, because a mutant with Ser/Thr to Ala substitutions activates the IFN promoter less efficiently. However, overexpression of IRF-3 in human 2FTGH cells alone results in the induction of an antiviral state, which depends on functional IFN signaling, because IRF-3 does not induce an antiviral state in mutant 2FTGH cells defective in either JAK-1 or p48 functions; also no antiviral effect of IRF-3 could be demonstrated in Vero cells that lack the IFNA and IFNB genes. This finding indicates that the observed antiviral activity of IRF-3 in 2FTGH cells results mainly from the induction of IFNs. Furthermore, E1A protein inhibited IRF-3-mediated stimulation of the IFNA4 promoter in transient expression assays; this inhibition could be reversed partially by overexpression of CBP/p300 and was not demonstrated with the mutant of E1A that does not bind p300. These results identify IRF-3 and CBP/p300 as integral components of the virus-induced complex that stimulates type 1 IFN gene transcription. The observation that adenovirus E1A antagonizes IRF-3 mediated activation suggests that E1A and IRF-3 may compete for binding to CBP/p300 and implicates a novel mechanism by which adenovirus may overcome the antiviral effects of the IFN pathway.