Tumor-promoting functions of UHRF1 in retinoblastoma

UHRF1 (ubiquitin-like with PHD and ring finger domains 1) is an epigenetic regulator that is involved in the regulation of DNA and histone methylation and many other cellular events. The UHRF1 is frequently found to be overexpressed in various human cancers including retinoblastoma, and its overexpression has been associated with tumor-promoting effects such as inhibition of apoptosis and high metastatic potential. However, the detailed mechanisms underlying these tumor-promoting functions of UHRF1 in retinoblastoma still remain unclear. In this study, we uncovered that UHRF1 depletion in retinoblastoma cells sensitizes the cells to histone deacetylase (HDAC) inhibitors, augmenting apoptotic cell death. To understand the molecular mechanisms underlying the enhanced sensitivity to HDAC inhibitors in the UHRF1-depleted retinoblastoma cells, we performed the gene expression profiling in UHRF1-knockdown Y79 cells in comparison with control-knockdown cells by RNA-sequencing to identify differentially expressed genes. Our RNA-seq results revealed that UHRF1 depletion downregulates redox-responsive genes such as GSTA4 and TXN2, leading to increased intracellular oxidative stress and higher susceptibility to HDAC inhibitor treatment. Overall design: Gene expression profiling of control-knockdown (YT) and UHRF1-knockdown (YS) Y79 retinoblastoma cell line by RNA-seq; Identification of differentially expressed genes between control and UHRF-knockdown Y79 cells using two independent biological replicates

UHRF1（ubiquitin-like with PHD and ring finger domains 1，即含PHD结构域与环指结构域的泛素样蛋白1）是一类参与DNA与组蛋白甲基化调控及多种细胞事件的表观遗传调控因子。该蛋白在包括视网膜母细胞瘤在内的多种人类癌症中常出现过表达，其过表达与促肿瘤效应密切相关，例如抑制细胞凋亡、具备高转移潜能。然而，UHRF1在视网膜母细胞瘤中发挥促肿瘤功能的具体分子机制仍未阐明。本研究发现，在视网膜母细胞瘤细胞中敲低UHRF1可使细胞对组蛋白去乙酰化酶（HDAC，histone deacetylase）抑制剂敏感，增强细胞凋亡水平。为阐明UHRF1敲低的视网膜母细胞瘤细胞对HDAC抑制剂敏感性增强的分子机制，我们通过RNA测序对UHRF1敲低的Y79细胞与对照敲低细胞进行基因表达谱分析，以筛选差异表达基因。RNA测序结果显示，UHRF1敲低会下调GSTA4、TXN2等氧化应激响应基因，导致细胞内氧化应激水平升高，进而增强细胞对HDAC抑制剂治疗的易感性。总体实验设计：通过RNA测序对对照敲低（YT组）与UHRF1敲低（YS组）的Y79视网膜母细胞瘤细胞系开展基因表达谱分析；采用两组独立生物学重复，筛选对照敲低与UHRF1敲低Y79细胞间的差异表达基因。