Sustained expression of the Spi-1/PU.1 and Fli-1 oncoproteins blocks globin gene activation in mouse erythroleukemia cells; however, only Spi-1/PU.1 expression inhibits the inclusion of exon 16 in the mature 4.1R mRNA...Sustained expression of the Spi-1/PU.1 and Fli-1 oncoproteins blocks globin gene activation in mouse erythroleukemia cells; however, only Spi-1/PU.1 expression inhibits the inclusion of exon 16 in the mature 4.1R mRNA. This splicing event is crucial for a functional 4.1R protein and, therefore, for red blood cell membrane integrity. This report demonstrates that Spi-1/PU.1 downregulation induces the activation of TRIM10/hematopoietic RING finger 1 （HERF1）, a member of the tripartite motif （TRIM）/RBCC protein family needed for globin gene transcription. Additionally, we demonstrate that TRIM10/HERF1 is required for the regulated splicing of exon 16 during late erythroid differentia- tion. Using inducible overexpression and silencing approaches, we found that： （1） TRIM10/HERF1 knockdown inhibits hemoglobin production and exon splicing and triggers cell apoptosis in dimethylsulfoxide （DMSO）-induced cells; （2） TRIM10/HERF1 upregulation is required but is insufficient on its own to activate exon retention; （3） Fli-1 has no effect on TRIM10/HERFI expression, whereas either DMSO-induced downregulation or shRNA-knockdown of Spi-I/PU.I expression is sufficient to activate TRIM10/HERF1 expression; and （4） Spi-1/PU.1 knockdown triggers both the transcription and the splicing events independently of the chemical induction. Altogether, these data indicate that primary Spi-1/PU.1 downregulation acts on late erythroid differentiation through at least two pathways, one of which requires TRIM10/HERF1 upregulation and parallels the Spi-1/PU.1-induced Fli-1 shutoff regulatory cascade.展开更多
文摘目的利用CRISPR/Cas9系统构建稳定敲除4.1R基因的RAW264.7巨噬细胞株,为研究4.1R在巨噬细胞中的功能奠定基础。方法根据CRISPR/Cas9靶向原理设计并合成3个特异性识别4.1R基因的向导RNA(sgRNA),构建sgRNAlenti CRISPRv2重组质粒并转入293T细胞中制备sgRNA-Cas9慢病毒,慢病毒侵染RAW264.7细胞,嘌呤霉素筛选出阳性细胞并稀释至单克隆,Western blotting印记检测单克隆细胞中蛋白4.1R的表达,测序确认单克隆细胞中突变位点。结果 Western blotting印迹检测结果表明筛选出的1株单克隆细胞中蛋白4.1R的表达完全缺失;测序结果表明该细胞株中4.1R基因发生了19bp的缺失突变;并且4.1R基因敲除后,RAW264.7细胞的增殖能力显著增加。结论本研究利用CRISPR/Cas9系统成功的干扰了巨噬细胞系RAW264.7细胞中4.1R的表达,为研究4.1R在巨噬细胞中的功能提供了有效工具。
文摘Sustained expression of the Spi-1/PU.1 and Fli-1 oncoproteins blocks globin gene activation in mouse erythroleukemia cells; however, only Spi-1/PU.1 expression inhibits the inclusion of exon 16 in the mature 4.1R mRNA. This splicing event is crucial for a functional 4.1R protein and, therefore, for red blood cell membrane integrity. This report demonstrates that Spi-1/PU.1 downregulation induces the activation of TRIM10/hematopoietic RING finger 1 （HERF1）, a member of the tripartite motif （TRIM）/RBCC protein family needed for globin gene transcription. Additionally, we demonstrate that TRIM10/HERF1 is required for the regulated splicing of exon 16 during late erythroid differentia- tion. Using inducible overexpression and silencing approaches, we found that： （1） TRIM10/HERF1 knockdown inhibits hemoglobin production and exon splicing and triggers cell apoptosis in dimethylsulfoxide （DMSO）-induced cells; （2） TRIM10/HERF1 upregulation is required but is insufficient on its own to activate exon retention; （3） Fli-1 has no effect on TRIM10/HERFI expression, whereas either DMSO-induced downregulation or shRNA-knockdown of Spi-I/PU.I expression is sufficient to activate TRIM10/HERF1 expression; and （4） Spi-1/PU.1 knockdown triggers both the transcription and the splicing events independently of the chemical induction. Altogether, these data indicate that primary Spi-1/PU.1 downregulation acts on late erythroid differentiation through at least two pathways, one of which requires TRIM10/HERF1 upregulation and parallels the Spi-1/PU.1-induced Fli-1 shutoff regulatory cascade.
