Zhai Peng-Fei, Wang Fang, Su Rui, Lin Hai-Shuang, Jiang Chong-Liang, Yang Gui-Hua, Yu Jia, Zhang Jun-Wu
Key State Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100005, China.
Key State Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100005, China.
J Biol Chem. 2014 Aug 15;289(33):22600-22613. doi: 10.1074/jbc.M114.547380. Epub 2014 Jun 30.
Emerging evidence has shown that microRNAs have key roles in regulating various normal physiological processes, whereas their deregulated expression is correlated with various diseases. The miR-146 family includes miR-146a and miR-146b, with a distinct expression spectrum in different hematopoietic cells. Recent work indicated that miR-146a has a close relationship with inflammation and autoimmune diseases. miR-146-deficient mice have developed some abnormal hematopoietic phenotypes, suggesting the potential functions of miR-146 in hematopoietic development. In this study, we found that miR-146b was consistently up-regulated in both K562 and CD34(+) hematopoietic stem/progenitor cells (HSPCs) undergoing either erythroid or megakaryocytic differentiation. Remarkably, erythroid and megakaryocytic maturation of K562 cells was induced by excess miR-146b but inhibited by decreased miR-146b levels. More importantly, an mRNA encoding receptor tyrosine kinase, namely platelet-derived growth factor receptor α (PDGFRA), was identified and validated as a direct target of miR-146b in hematopoietic cells. Gain-of-function and loss-of-function assays showed that PDGFRA functioned as a negative regulator in erythroid and megakaryocytic differentiation. miR-146b could ultimately affect the expression of the GATA-1 gene, which is regulated by HEY1 (Hairy/enhancer-of-split related with YRPW motif protein 1), a transcriptional repressor, via inhibition of the PDGFRA/JNK/JUN/HEY1 pathway. Lentivirus-mediated gene transfer also demonstrated that the overexpression of miR-146b promoted erythropoiesis and megakaryocytopoiesis of HSPCs via its regulation on the PDGFRA gene and effects on GATA-1 expression. Moreover, we confirmed that the binding of GATA-1 to the miR-146b promoter and induction of miR-146b during hematopoietic maturation were dependent on GATA-1. Therefore, miR-146b, PDGFRA, and GATA-1 formed a regulatory circuit to promote erythroid and megakaryocytic differentiation.
新出现的证据表明，微小RNA在调节各种正常生理过程中起关键作用，而其表达失调与多种疾病相关。miR-146家族包括miR-146a和miR-146b，在不同造血细胞中具有独特的表达谱。最近的研究表明，miR-146a与炎症和自身免疫性疾病密切相关。miR-146缺陷小鼠出现了一些异常的造血表型，提示miR-146在造血发育中的潜在功能。在本研究中，我们发现miR-146b在经历红系或巨核系分化的K562和CD34(+)造血干/祖细胞（HSPCs）中均持续上调。值得注意的是，过量的miR-146b可诱导K562细胞的红系和巨核系成熟，但miR-146b水平降低则会抑制其成熟。更重要的是，一种编码受体酪氨酸激酶的mRNA，即血小板衍生生长因子受体α（PDGFRA），被鉴定并验证为造血细胞中miR-146b的直接靶点。功能获得和功能丧失实验表明，PDGFRA在红系和巨核系分化中起负调节作用。miR-146b最终可影响GATA-1基因的表达，该基因受转录抑制因子HEY1（与YRPW基序蛋白1相关的毛状/分裂增强子）调控，通过抑制PDGFRA/JNK/JUN/HEY1通路实现。慢病毒介导的基因转移也表明，miR-146b的过表达通过其对PDGFRA基因的调控和对GATA-1表达的影响，促进了HSPCs的红细胞生成和巨核细胞生成。此外，我们证实GATA-1与miR-146b启动子的结合以及造血成熟过程中miR-146b的诱导均依赖于GATA-1。因此，miR-146b、PDGFRA和GATA-1形成了一个调节回路，以促进红系和巨核系分化。
