Human Cytomegalovirus Immediate-Early 1 Protein Rewires Upstream STAT3 to Downstream STAT1 Signaling Switching an IL6-Type to an IFNγ-Like Response.
Human Cytomegalovirus Immediate-Early 1 Protein Rewires Upstream STAT3 to Downstream STAT1 Signaling Switching an IL6-Type to an IFNγ-Like Response.
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DOI：
10.1371/journal.ppat.1005748
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发表时间：
2016-07
期刊：
影响因子：
6.7
通讯作者：
Paulus C
中科院分区：
文献类型：
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作者：
Harwardt T;Lukas S;Zenger M;Reitberger T;Danzer D;Übner T;Munday DC;Nevels M;Paulus C
人巨细胞病毒（hCMV）主要的立即早期1蛋白（IE 1）是最有名的激活转录，以促进病毒复制。在这里，我们提供的转录组数据表明IE 1既是宿主基因表达的激活剂，又是重要的抑制剂。诱导表达IE 1的人细胞表现出对IL 6和抑瘤素M应答性STAT 3靶基因的全面抑制。这种抑制之后是通常由IFNγ诱导的STAT 1磷酸化和STAT 1靶基因的活化。观察到的抑制和随后的激活都是通过IE 1的C-末端结构域中的相同区域（氨基酸410至445）介导的，并且该区域作为STAT 3的结合位点。STAT 3的消耗表型模仿了对IE 1的STAT 1依赖性IFNγ样应答。相反，IL 6受体（IL 6ST）或STAT激酶JAK 1的耗竭阻止了这种反应。因此，在表达野生型IE 1的细胞中，用IL 6处理导致STAT 1而不是STAT 3活化延长，但在表达STAT 3结合缺陷的突变蛋白（IE 1d 1410 -420）的细胞中则不。非常相似的针对IL 6的STAT 1的应答也存在于用野生型或回复突变hCMV感染的细胞中，但不存在IE 1d 1410 -420突变病毒，并且这种应答导致病毒复制受限。我们的结论是，IE 1是足够的和必要的重新连接上游IL 6型到下游IFNγ样信号，两个途径链接到相反的行动，导致抑制STAT 3和激活STAT 1响应基因。这些发现涉及IE 1的转录抑制因子和激活因子功能，并提示了与病毒发病机制相关的意外结果，这些结果与hCMV感染细胞中通过IL 6ST-JAK 1-STAT 3轴发出信号的细胞因子或生长因子有关。我们的研究结果还表明，IE 1，被认为是一个关键的激活剂的hCMV生产周期的蛋白质，有一个意想不到的作用，在回火病毒复制。我们以前的工作表明，人巨细胞病毒（hCMV）的主要立即早期1蛋白（IE 1）调节宿主细胞信号转导通路，涉及信号转导和转录激活因子（STAT）家族的蛋白质。IE 1也早已被认为通过激活转录来促进病毒复制。在这份报告中，我们证明，IE 1是一个显着的阻遏物，因为它是一个激活宿主基因表达。许多被IE 1抑制的基因通常通过由白细胞介素6（IL 6）或相关细胞因子触发的STAT 3信号传导来诱导，而许多被IE 1激活的基因通常通过由干扰素γ（IFNγ）触发的STAT 1信号传导来诱导。我们的研究结果表明，抑制STAT 3-和激活STAT 1响应基因的IE 1耦合。通过靶向STAT 3，IE 1将上游STAT 3重新连接到下游STAT 1信号传导。因此，通常由IL 6诱导的基因被抑制，而通常由IFNγ诱导的基因在IE 1存在下对IL 6产生应答。我们还证明，通过将IL 6转换为IFNγ样应答，IE 1缓和了病毒复制。这些结果表明IE 1在促进或限制hCMV增殖中具有意想不到的双重作用，并证明了关键的病毒调节蛋白如何合并两个中心细胞信号传导途径以转移与hCMV发病机制相关的细胞因子应答。
The human cytomegalovirus (hCMV) major immediate-early 1 protein (IE1) is best known for activating transcription to facilitate viral replication. Here we present transcriptome data indicating that IE1 is as significant a repressor as it is an activator of host gene expression. Human cells induced to express IE1 exhibit global repression of IL6- and oncostatin M-responsive STAT3 target genes. This repression is followed by STAT1 phosphorylation and activation of STAT1 target genes normally induced by IFNγ. The observed repression and subsequent activation are both mediated through the same region (amino acids 410 to 445) in the C-terminal domain of IE1, and this region serves as a binding site for STAT3. Depletion of STAT3 phenocopies the STAT1-dependent IFNγ-like response to IE1. In contrast, depletion of the IL6 receptor (IL6ST) or the STAT kinase JAK1 prevents this response. Accordingly, treatment with IL6 leads to prolonged STAT1 instead of STAT3 activation in wild-type IE1 expressing cells, but not in cells expressing a mutant protein (IE1dl410-420) deficient for STAT3 binding. A very similar STAT1-directed response to IL6 is also present in cells infected with a wild-type or revertant hCMV, but not an IE1dl410-420 mutant virus, and this response results in restricted viral replication. We conclude that IE1 is sufficient and necessary to rewire upstream IL6-type to downstream IFNγ-like signaling, two pathways linked to opposing actions, resulting in repressed STAT3- and activated STAT1-responsive genes. These findings relate transcriptional repressor and activator functions of IE1 and suggest unexpected outcomes relevant to viral pathogenesis in response to cytokines or growth factors that signal through the IL6ST-JAK1-STAT3 axis in hCMV-infected cells. Our results also reveal that IE1, a protein considered to be a key activator of the hCMV productive cycle, has an unanticipated role in tempering viral replication. Our previous work has shown that the human cytomegalovirus (hCMV) major immediate-early 1 protein (IE1) modulates host cell signaling pathways involving proteins of the signal transducer and activator of transcription (STAT) family. IE1 has also long been known to facilitate viral replication by activating transcription. In this report we demonstrate that IE1 is as significant a repressor as it is an activator of host gene expression. Many genes repressed by IE1 are normally induced via STAT3 signaling triggered by interleukin 6 (IL6) or related cytokines, whereas many genes activated by IE1 are normally induced via STAT1 signaling triggered by interferon gamma (IFNγ). Our results suggest that the repression of STAT3- and the activation of STAT1-responsive genes by IE1 are coupled. By targeting STAT3, IE1 rewires upstream STAT3 to downstream STAT1 signaling. Consequently, genes normally induced by IL6 are repressed while genes normally induced by IFNγ become responsive to IL6 in the presence of IE1. We also demonstrate that, by switching an IL6 to an IFNγ-like response, IE1 tempers viral replication. These results suggest an unanticipated dual role for IE1 in either promoting or limiting hCMV propagation and demonstrate how a key viral regulatory protein merges two central cellular signaling pathways to divert cytokine responses relevant to hCMV pathogenesis.