Induction of the CTLA-4 gene in human lymphocytes is dependent on NFAT binding the proximal promoter
Induction of the CTLA-4 gene in human lymphocytes is dependent on NFAT binding the proximal promoter
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DOI：
10.4049/jimmunol.179.6.3831
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发表时间：
2007-09-15
影响因子：
4.4
通讯作者：
Wong, Henry K.
中科院分区：
文献类型：
--
作者：
Gibson, Heather M.;Hedgcock, Carrie J.;Wong, Henry K.
CTLA-4是共刺激家族的成员，与CD 28具有同源性，并结合B7配体家族。与CD 28不同，CTLA-4连接在T细胞中传递负信号。CTLA-4表达虽然在大多数T细胞中是可诱导的，但在具有调节表型的T细胞上组成型表达。控制CTLA-4在人T细胞中表达的机制表征不佳，因此我们试图更好地理解CTLA-4基因活化的机制。通过克隆5'上游启动子和创建启动子缺失报告构建体，我们表明，近端启动子是激活CTLA-4基因的关键。在该区域内，我们鉴定了以高亲和力结合NFAT的NFAT共有序列，其不同于其他NFAT序列并且不募集AP-1。在天然CTLA-4基因的染色质蛋白质的分析表明，该启动子区域成为与乙酰化组蛋白的染色质免疫沉淀测定。此外，NFAT 1在染色质免疫沉淀刺激后与CTLA-4基因的启动子结合。NFAT位点的突变消除了启动子的活性，证明了NFAT位点对CTLA-4转录的功能要求。此外，NFAT抑制剂抑制CTLA-4基因表达，表明NFAT在调节淋巴细胞中CTLA-4基因的诱导中起关键作用。NFAT作为CTLA-4基因的关键调节因子的鉴定表明，靶向NFAT功能可能导致调节CTLA-4基因以控制免疫应答的新方法。
CTLA-4 is a member of the costimulatory family, has homology to CD28, and binds the B7 family of ligands. Unlike CD28, CTLA-4 ligation transmits a negative signal in T cells. CTLA-4 expression, while inducible in most T cells, is expressed constitutively on T cells with a regulatory phenotype. The mechanism controlling CTLA-4 expression in human T cells is poorly characterized, thus we sought to better understand the mechanism of activation of the CTLA-4 gene. By cloning the 5' upstream promoter and creating promoter-deletion reporter constructs, we show that the proximal promoter is critical for activating the CTLA-4 gene. Within this region, we identify a NFAT consensus sequence that binds NFAT with high affinity that differs from other NFAT sequences and does not recruit AP-1. Analysis of the chromatin proteins in the native CTLA-4 gene shows that this promoter region becomes associated with acetylated histones by chromatin immunoprecipitation assays. In addition, NFAT1 binds to the promoter of the CTLA-4 gene after stimulation by chromatin immunoprecipitation. The functional requirement of the NFAT site for CTLA-4 transcription was demonstrated by mutations in the NFAT site that abolished the activity of the promoter. Furthermore, inhibitors of NFAT suppressed CTLA-4 gene expression, indicating that NFAT plays a critical role in regulating the induction of the CTLA-4 gene in lymphocytes. The identification of NFAT as a critical regulator of the CTLA-4 gene suggests that targeting NFAT function may lead to novel approaches to modulate the CTLA-4 gene to control the immune response.