Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD.
Blood. 2022 Jun 16;139(24):3532-3545. doi: 10.1182/blood.2021014308.
Hemogen is a hematopoietic tissue-specific gene that regulates the proliferation and differentiation of hematopoietic cells; however, the mechanism underlying its function in erythropoiesis is unknown. We found that depletion of hemogen in human CD34+ erythroid progenitor cells and HUDEP2 cells significantly reduced the expression of genes associated with heme and hemoglobin synthesis, supporting a positive role for hemogen in erythroid maturation. In human K562 cells, hemogen antagonized the occupancy of corepressors nucleosome remodeling and histone deacetylase (NuRD) complex and facilitated LDB1 complex-mediated chromatin looping. Hemogen recruited SWI/SNF complex ATPase BRG1 as a coactivator to regulate nucleosome accessibility and H3K27ac enrichment for promoter and enhancer activity. To determine whether hemogen/BRG1 cooperativity is conserved in mammalian systems, we generated hemogen-knockout/knockin mice and investigated hemogen/BRG1 function in murine erythropoiesis. Loss of hemogen in embryonic days 12.5 to 16.5 fetal liver cells impeded erythroid differentiation through reducing the production of mature erythroblasts. Chromatin immunoprecipitation sequencing in wild-type and hemogen-knockout animals revealed that BRG1 is largely dependent on hemogen to regulate chromatin accessibility at erythroid gene promoters and enhancers. In summary, the hemogen/BRG1 interaction in mammals is essential for fetal erythroid maturation and hemoglobin production through its active role in promoter and enhancer activity and chromatin organization.
血球生成素是一种造血组织特异性基因，可调节造血细胞的增殖和分化；然而，其在红细胞生成中的功能机制尚不清楚。我们发现，在人类 CD34+红系祖细胞和 HUDEP2 细胞中耗尽血球生成素，显著降低了与血红素和血红蛋白合成相关的基因的表达，支持血球生成素在红细胞成熟中发挥积极作用。在人类 K562 细胞中，血球生成素拮抗核小体重塑和组蛋白去乙酰化酶 (NuRD) 复合物的核心抑制剂的占据，并促进 LDB1 复合物介导的染色质环化。血球生成素招募 SWI/SNF 复合物 ATP 酶 BRG1 作为共激活因子，以调节核小体可及性和 H3K27ac 对启动子和增强子活性的富集。为了确定血球生成素/BRG1 协同作用是否在哺乳动物系统中保守，我们生成了血球生成素敲除/敲入小鼠，并研究了血球生成素/BRG1 在小鼠红细胞生成中的功能。在胚胎第 12.5 天至 16.5 天的胎肝细胞中缺失血球生成素，通过减少成熟红细胞的产生来阻碍红细胞分化。在野生型和血球生成素敲除动物中的染色质免疫沉淀测序揭示，BRG1 在很大程度上依赖于血球生成素来调节红细胞基因启动子和增强子处的染色质可及性。总之，哺乳动物中的血球生成素/BRG1 相互作用对于胎儿红细胞成熟和血红蛋白产生是必不可少的，因为它在启动子和增强子活性以及染色质组织中发挥积极作用。
