FACT (FAcilitates Chromatin Transcription) is a heterodimeric protein complex composed of SUPT16H and SSRP1, and a histone chaperone participating in chromatin remodeling during gene transcription. FACT complex is profoundly regulated, and contributes to both gene activation and suppression. Here we reported that SUPT16H, a subunit of FACT, is acetylated in both epithelial and natural killer (NK) cells. The histone acetyltransferase TIP60 contributes to the acetylation of SUPT16H middle domain (MD) at lysine 674 (K674). Such acetylation of SUPT16H is recognized by bromodomain protein BRD4, which promotes protein stability of SUPT16H in both epithelial and NK cells. We further demonstrated that SUPT16H-BRD4 associates with histone modification enzymes (HDAC1, EZH2), and further regulates their activation status and/or promoter association as well as affects the relevant histone marks (H3ac, H3K9me3 and H3K27me3). BRD4 is known to profoundly regulate interferon (IFN) signaling, while such function of SUPT16H has never been explored. Surprisingly, our results revealed that SUPT16H genetic knockdown via RNAi or pharmacological inhibition by using its inhibitor, curaxin 137 (CBL0137), results in the induction of IFNs and interferon-stimulated genes (ISGs). Through this mechanism, depletion or inhibition of SUPT16H is shown to efficiently inhibit infection of multiple viruses, including Zika, influenza, and SARS-CoV-2. Furthermore, we demonstrated that depletion or inhibition of SUPT16H also causes the remarkable activation of IFN signaling in NK cells, which promotes the NK-mediated killing of virus-infected cells in a co-culture system using human primary NK cells. Overall, our studies unraveled the previously un-appreciated role of FACT complex in coordinating with BRD4 and regulating IFN signaling in both epithelial and NK cells, and also proposed the novel application of the FACT inhibitor CBL0137 to treat viral infections.

中文翻译：

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FACT 亚基 SUPT16H 与 BRD4 关联并有助于干扰素信号传导的沉默


FACT（促进染色质转录）是由 SUPT16H 和 SSRP1 组成的异二聚体蛋白复合物，以及参与基因转录过程中染色质重塑的组蛋白伴侣。 FACT 复合物受到深刻调控，有助于基因激活和抑制。在这里，我们报道了 SUPT16H（FACT 的一个亚基）在上皮细胞和自然杀伤 (NK) 细胞中被乙酰化。组蛋白乙酰转移酶 TIP60 有助于 SUPT16H 中间结构域 (MD) 赖氨酸 674 (K674) 的乙酰化。 SUPT16H 的这种乙酰化可被溴结构域蛋白 BRD4 识别，从而促进 SUPT16H 在上皮细胞和 NK 细胞中的蛋白稳定性。我们进一步证明 SUPT16H-BRD4 与组蛋白修饰酶（HDAC1、EZH2）相关，并进一步调节其激活状态和/或启动子关联以及影响相关组蛋白标记（H3ac、H3K9me3 和 H3K27me3）。众所周知，BRD4 能够深刻调节干扰素 (IFN) 信号传导，而 SUPT16H 的这种功能从未被探索过。令人惊讶的是，我们的结果表明，通过 RNAi 或使用其抑制剂 curaxin 137 (CBL0137) 进行药理抑制来敲除 SUPT16H 基因，可诱导 IFN 和干扰素刺激基因 (ISG)。通过这种机制，消除或抑制 SUPT16H 可有效抑制多种病毒的感染，包括寨卡病毒、流感病毒和 SARS-CoV-2。此外，我们证明 SUPT16H 的消耗或抑制还会导致 NK 细胞中 IFN 信号的显着激活，从而促进使用人原代 NK 细胞的共培养系统中 NK 介导的病毒感染细胞的杀伤。 总体而言，我们的研究揭示了 FACT 复合物在与 BRD4 协调和调节上皮细胞和 NK 细胞中 IFN 信号传导方面先前未被认识到的作用，并提出了 FACT 抑制剂 CBL0137 治疗病毒感染的新应用。