WDR5 在沉默人胎儿珠蛋白基因表达中的作用。
The role of WDR5 in silencing human fetal globin gene expression.
机构信息
Molecular Immunology and Cancer Research Center, The State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing 210093, China.
出版信息
Haematologica. 2012 Nov;97(11):1632-40. doi: 10.3324/haematol.2012.061937. Epub 2012 Jun 11.
BACKGROUND
Histone H3 lysine 4 (K4) methylation has been linked with transcriptional activity in mammalian cells. The WD40-repeat protein, WDR5, is an essential component of the MLL complex that induces histone H3 K4 methylation, but the role of WDR5 in human globin gene regulation has not yet been established.
DESIGN AND METHODS
To study the role of WDR5 in human globin gene regulation, we performed knockdown experiments in both K562 cells and primary human bone marrow erythroid progenitor cells (BMC). The effects of WDR5 knockdown on γ-globin gene expression were determined. Biochemical approaches were also employed to investigate WDR5 interaction molecules. Chromosomal marks in the globin locus were analyzed by ChIP.
RESULTS
We found that WDR5 interacted with protein arginine methyltransferase 5 (PRMT5), a known repressor of γ-globin gene expression, and was essential for generating tri-methylated H3K4 (H3K4me3) at the γ-globin promoter in K562 cells. Enforced expression of WDR5 in K562 cells reduced γ-globin gene expression, whereas knockdown of WDR5 increased γ-globin gene expression in both K562 cells and primary human bone marrow erythroid progenitor cells. Consistent with this, both histone H3 and H4 acetylation at the γ-globin promoter were increased, while histone H4R3 and H3K9 methylation were decreased, in WDR5 knockdown cells compared to controls. We found that WDR5 interacted with HDAC1 and a PHD domaincontaining protein, ING2 (inhibitor of growth), an H3K4me3 mark reader, to enhance γ-globin gene transcriptional repression. In human BMC, levels of WDR5 were highly enriched on the γ-promoter relative to levels on other globin promoters and compared to the γ-promoter in cord blood erythroid progenitors, suggesting that WDR5 is important in the developmental globin gene expression program.
CONCLUSIONS
Our data are consistent with a model in which WDR5 binds the γ-globin promoter in a PRMT5-dependent manner; H3K4me3 induced at the γ-globin promoter by WDR5 may result in the recruitment of the ING2-associated HDAC1 component and consequent silencing of γ-globin gene expression.
背景
组蛋白 H3 赖氨酸 4（K4）甲基化与哺乳动物细胞中的转录活性有关。WD40 重复蛋白 WDR5 是诱导组蛋白 H3 K4 甲基化的 MLL 复合物的重要组成部分，但 WDR5 在人类珠蛋白基因调控中的作用尚未确定。
设计与方法
为了研究 WDR5 在人类珠蛋白基因调控中的作用，我们在 K562 细胞和原代人骨髓红系祖细胞（BMC）中进行了敲低实验。确定 WDR5 敲低对 γ-珠蛋白基因表达的影响。还采用生化方法研究 WDR5 相互作用分子。通过 ChIP 分析珠蛋白基因座中的染色质标记。
结果
我们发现 WDR5 与蛋白精氨酸甲基转移酶 5（PRMT5）相互作用，PRMT5 是 γ-珠蛋白基因表达的已知抑制剂，并且在 K562 细胞中产生 γ-珠蛋白启动子上的三甲基化 H3K4（H3K4me3）是必需的。在 K562 细胞中过表达 WDR5 可降低 γ-珠蛋白基因表达，而在 K562 细胞和原代人骨髓红系祖细胞中敲低 WDR5 可增加 γ-珠蛋白基因表达。与此一致的是，与对照相比，WDR5 敲低细胞中 γ-珠蛋白启动子处的组蛋白 H3 和 H4 乙酰化增加，而组蛋白 H4R3 和 H3K9 甲基化减少。我们发现 WDR5 与 HDAC1 和 PHD 结构域包含蛋白 ING2（生长抑制剂）相互作用，ING2 是 H3K4me3 标记读取器，以增强 γ-珠蛋白基因转录抑制。在人 BMC 中，与其他珠蛋白启动子相比，WDR5 在 γ-启动子上的水平高度富集，与脐带血红系祖细胞中的 γ-启动子相比，WDR5 水平更高，这表明 WDR5 在发育中的珠蛋白基因表达程序中很重要。
结论
我们的数据与以下模型一致：WDR5 以 PRMT5 依赖的方式结合 γ-珠蛋白启动子；WDR5 在 γ-珠蛋白启动子上诱导的 H3K4me3 可能导致 ING2 相关的 HDAC1 成分的募集，并导致 γ-珠蛋白基因表达沉默。
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