Objective Facilitates Chromatin Transcription (FACT) complex is a histone chaperone participating in DNA repair-related and transcription-related chromatin dynamics. In this study, we investigated its oncogenic functions, underlying mechanisms and therapeutic implications in human hepatocellular carcinoma (HCC). Design We obtained HCC and its corresponding non-tumorous liver samples from 16 patients and identified FACT complex as the most upregulated histone chaperone by RNA-Seq. We further used CRISPR-based gene activation and knockout systems to demonstrate the functions of FACT complex in HCC growth and metastasis. Functional roles and mechanistic insights of FACT complex in oxidative stress response were investigated by ChIP assay, flow cytometry, gene expression assays and 4sU-DRB transcription elongation assay. Therapeutic effect of FACT complex inhibitor, Curaxin, was tested in both in vitro and in vivo models. Results We showed that FACT complex was remarkably upregulated in HCC and contributed to HCC progression. Importantly, we unprecedentedly revealed an indispensable role of FACT complex in NRF2-driven oxidative stress response. Oxidative stress prevented NRF2 and FACT complex from KEAP1-mediated protein ubiquitination and degradation. Stabilised NRF2 and FACT complex form a positive feedback loop; NRF2 transcriptionally activates the FACT complex, while FACT complex promotes the transcription elongation of NRF2 and its downstream antioxidant genes through facilitating rapid nucleosome disassembly for the passage of RNA polymerase. Therapeutically, Curaxin effectively suppressed HCC growth and sensitised HCC cell to sorafenib. Conclusion In conclusion, our findings demonstrated that FACT complex is essential for the expeditious HCC oxidative stress response and is a potential therapeutic target for HCC treatment.

中文翻译：

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组蛋白伴侣 FACT 复合物介导氧化应激反应以促进肝癌进展

目的促进染色质转录 (FACT) 复合物是参与 DNA 修复相关和转录相关染色质动力学的组蛋白伴侣。在这项研究中，我们研究了其在人类肝细胞癌 (HCC) 中的致癌功能、潜在机制和治疗意义。设计 我们从 16 名患者中获得了 HCC 及其相应的非肿瘤肝脏样本，并通过 RNA-Seq 将 FACT 复合物鉴定为上调最多的组蛋白伴侣。我们进一步使用基于 CRISPR 的基因激活和敲除系统来证明 FACT 复合物在 HCC 生长和转移中的功能。通过 ChIP 测定、流式细胞术、基因表达测定和 4sU-DRB 转录延伸测定研究了 FACT 复合物在氧化应激反应中的功能作用和机制见解。FACT 复合物抑制剂 Curaxin 的治疗效果在体外和体内模型中进行了测试。结果我们发现 FACT 复合物在 HCC 中显着上调并有助于 HCC 进展。重要的是，我们前所未有地揭示了 FACT 复合物在 NRF2 驱动的氧化应激反应中不可或缺的作用。氧化应激阻止了 NRF2 和 FACT 复合物免受 KEAP1 介导的蛋白质泛素化和降解。稳定的 NRF2 和 FACT 复合物形成正反馈回路；NRF2 转录激活 FACT 复合物，而 FACT 复合物通过促进核小体快速分解以供 RNA 聚合酶通过，从而促进 NRF2 及其下游抗氧化基因的转录延伸。在治疗上，Curaxin 有效抑制 HCC 生长并使 HCC 细胞对索拉非尼敏感。