Interferon regulatory factor 8 regulates caspase-1 expression to facilitate Epstein-Barr virus reactivation in response to B cell receptor stimulation and chemical induction.
Interferon regulatory factor 8 regulates caspase-1 expression to facilitate Epstein-Barr virus reactivation in response to B cell receptor stimulation and chemical induction.
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DOI：
10.1371/journal.ppat.1006868
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发表时间：
2018-01
期刊：
影响因子：
6.7
通讯作者：
Li R
中科院分区：
文献类型：
--
作者：
Lv DW;Zhang K;Li R
干扰素调节因子8（Interferon Regulatory Factor 8，IRF 8），又称干扰素共有序列结合蛋白（Interferon Consensus Sequence-binding protein，ICSBP），是IRF家族的一种转录因子。IRF 8在正常B细胞分化中起关键作用，正常B细胞分化是与EB病毒（EBV）再活化内在相关的细胞过程。然而，IRF 8是否调节EBV裂解性复制仍然未知。在这项研究中，我们利用CRISPR/Cas9基因组编辑方法来消耗IRF 8，并发现IRF 8消耗显著抑制了裂解诱导后EBV的再活化。我们证明，IRF 8耗竭抑制了一组参与凋亡的基因的表达，从而抑制了通过B细胞受体（BCR）刺激或化学诱导的裂解诱导后的凋亡诱导。caspase-1、caspase-3和caspase-8的蛋白水平在IRF 8耗尽的细胞中均显著降低，这导致caspase活化减少以及KAP 1、PAX 5和DNMT 3A在BCR刺激后的稳定。有趣的是，半胱天冬酶抑制阻断了KAP 1、PAX 5和DNMT 3A的降解，抑制了裂解诱导后的EBV裂解基因表达和病毒DNA复制，表明IRF 8耗尽细胞中半胱天冬酶表达的降低有助于抑制EBV裂解复制。我们进一步证明了IRF 8通过靶向其基因启动子直接调节CASP 1（半胱天冬酶-1）基因表达，并且半胱天冬酶-1的敲低部分通过稳定KAP 1消除了裂解诱导后的EBV再活化。总之，我们的研究表明，通过调节半胱天冬酶的激活和随后裂解诱导后的KAP 1裂解，IRF 8在EBV裂解再激活中起着关键作用。EB病毒（EBV）感染与B细胞和上皮细胞起源的人类癌症密切相关。EBV的生命周期受到病毒和细胞因子的严格调控。在这里，我们证明，干扰素调节因子8（IRF 8）是必需的EBV裂解复制。在机制上，IRF 8直接调节半胱天冬酶-1的表达，并因此在B细胞受体（BCR）刺激和化学诱导时调节半胱天冬酶的活化，这导致抑制裂解复制的几种宿主因子（包括KAP 1）的裂解和去稳定化。Caspase-1耗竭阻断EBV再活化，而KAP 1耗竭促进caspase-1耗竭细胞中的再活化。这些结果共同建立了对EBV再活化重要的IRF 8/caspase-1/KAP 1轴。
Interferon regulatory factor 8 (IRF8), also known as interferon consensus sequence-binding protein (ICSBP), is a transcription factor of the IRF family. IRF8 plays a key role in normal B cell differentiation, a cellular process that is intrinsically associated with Epstein-Barr virus (EBV) reactivation. However, whether IRF8 regulates EBV lytic replication remains unknown. In this study, we utilized a CRISPR/Cas9 genomic editing approach to deplete IRF8 and found that IRF8 depletion dramatically inhibits the reactivation of EBV upon lytic induction. We demonstrated that IRF8 depletion suppresses the expression of a group of genes involved in apoptosis and thus inhibits apoptosis induction upon lytic induction by B cell receptor (BCR) stimulation or chemical induction. The protein levels of caspase-1, caspase-3 and caspase-8 all dramatically decreased in IRF8-depleted cells, which led to reduced caspase activation and the stabilization of KAP1, PAX5 and DNMT3A upon BCR stimulation. Interestingly, caspase inhibition blocked the degradation of KAP1, PAX5 and DNMT3A, suppressed EBV lytic gene expression and viral DNA replication upon lytic induction, suggesting that the reduced caspase expression in IRF8-depleted cells contributes to the suppression of EBV lytic replication. We further demonstrated that IRF8 directly regulates CASP1 (caspase-1) gene expression through targeting its gene promoter and knockdown of caspase-1 abrogates EBV reactivation upon lytic induction, partially through the stabilization of KAP1. Together our study suggested that, by modulating the activation of caspases and the subsequent cleavage of KAP1 upon lytic induction, IRF8 plays a critical role in EBV lytic reactivation. Infection with Epstein-Barr virus (EBV) is closely associated with human cancers of both B cell and epithelial cell origin. The EBV life cycle is tightly regulated by both viral and cellular factors. Here, we demonstrate that interferon regulatory factor 8 (IRF8) is required for EBV lytic replication. Mechanistically, IRF8 directly regulates caspase-1 expression and hence caspase activation upon B cell receptor (BCR) stimulation and chemical induction, which leads to the cleavage and de-stabilization of several host factors suppressing lytic replication, including KAP1. Caspase-1 depletion blocks EBV reactivation while KAP1 depletion facilitates reactivation in caspase-1 depleted cells. These results together establish a IRF8/caspase-1/KAP1 axis important for EBV reactivation.
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