Peking University People's Hospital, Peking University Hepatology Institute, Beijing Key Laboratory of Hepatitis C and Immunotherapy for Liver Disease, Beijing, 100044, China.
Department of Immunology, and the Key Laboratory of Laboratory Medicine of Jiangsu Province, School of Medicine, Jiangsu University, Zhenjiang, 212013, Jiangsu, China.
Sci Rep. 2020 Sep 3;10(1):14538. doi: 10.1038/s41598-020-71403-1.
Regulatory factor X-5 (RFX5) represents a key transcription regulator of MHCII gene expression in the immune system. This study aims to explore the molecular mechanisms and biological significance of RFX5. Firstly, by analyzing ENCODE chromatin immunoprecipitation (ChIP)-seq in HepG2 and TCGA RNA-seq data, we discovered lysine-specific demethylase 4A (KDM4A), also named JMJD2A, to be a major downstream target gene of RFX5. Moreover, RFX5 was verified to bind directly to the KDM4A's promoter region and sequentially promoted its transcription determined by the ChIP-PCR assay and luciferase assay. In addition, RFX5-dependent regulation of KDM4A was demonstrated in HCC. Compared with adjacent non-tumor tissues, the expression levels of KDM4A were significantly raised in HCC tumor tissues. Notably, elevated levels of KDM4A were strongly correlated with HCC patient prognosis. Functionally, KDM4A overexpression largely rescued the growth inhibitory effects of RFX5 deletion, highlighting KDM4A as a downstream effector of RFX5. Mechanistically, the RFX5-KDM4A pathway promoted the progression of the cell cycle from G0/G1 to S phase and was protective against cell apoptosis through regulation of p53 and its downstream genes in HCC. In conclusion, RFX5 could promote HCC progression via transcriptionally activating KDM4A expression.
调控因子 X-5（RFX5）是免疫系统中 MHCII 基因表达的关键转录调控因子。本研究旨在探讨 RFX5 的分子机制和生物学意义。首先，通过分析 HepG2 中的 ENCODE 染色质免疫沉淀（ChIP）-seq 和 TCGA RNA-seq 数据，我们发现赖氨酸特异性去甲基酶 4A（KDM4A），又名 JMJD2A，是 RFX5 的主要下游靶基因。此外，通过 ChIP-PCR 检测和荧光素酶检测证实 RFX5 可直接结合 KDM4A 的启动子区域并依次促进其转录。此外，在 HCC 中证实了 RFX5 对 KDM4A 的依赖性调节。与相邻非肿瘤组织相比，HCC 肿瘤组织中 KDM4A 的表达水平显著升高。值得注意的是，KDM4A 水平的升高与 HCC 患者的预后密切相关。功能上，KDM4A 的过表达在很大程度上挽救了 RFX5 缺失的生长抑制作用，突出了 KDM4A 作为 RFX5 的下游效应物。从机制上讲，RFX5-KDM4A 通路通过调节 HCC 中 p53 及其下游基因，促进细胞周期从 G0/G1 期向 S 期的进展，并防止细胞凋亡。综上所述，RFX5 可通过转录激活 KDM4A 的表达促进 HCC 的进展。
