Fujiwara Tohru, Sasaki Katsuyuki, Saito Kei, Hatta Shunsuke, Ichikawa Satoshi, Kobayashi Masahiro, Okitsu Yoko, Fukuhara Noriko, Onishi Yasushi, Harigae Hideo
Department of Hematology and Rheumatology, Tohoku University Graduate School, Sendai, 2-1 Seiryo-cho, Aoba-ku, Sendai 980-8575, Japan.
Department of Hematology and Rheumatology, Tohoku University Graduate School, Sendai, 2-1 Seiryo-cho, Aoba-ku, Sendai 980-8575, Japan; Department of Laboratory, Tohoku University Hospital, Sendai, 1-1 Seiryo-cho, Aoba-ku, Sendai 980-8574, Japan.
Biochem Biophys Res Commun. 2017 Apr 1;485(2):380-387. doi: 10.1016/j.bbrc.2017.02.068. Epub 2017 Feb 16.
The transcription factor GATA-1-interacting protein Friend of GATA-1 (FOG1) is essential for proper transcriptional activation and repression of GATA-1 target genes; yet, the mechanisms by which FOG1 exerts its activating and repressing functions remain unknown. Forced FOG1 expression in human K562 erythroleukemia cells induced the expression of erythroid genes (SLC4A1, globins) but repressed that of GATA-2 and PU.1. A quantitative chromatin immunoprecipitation (ChIP) analysis demonstrated increased GATA-1 chromatin occupancy at both FOG1-activated as well as FOG1-repressed gene loci. However, while TAL1 chromatin occupancy was significantly increased at FOG1-activated gene loci, it was significantly decreased at FOG1-repressed gene loci. When FOG1 was overexpressed in TAL1-knocked down K562 cells, FOG1-mediated activation of HBA, HBG, and SLC4A1 was significantly compromised by TAL1 knockdown, suggesting that FOG1 may require TAL1 to activate GATA-1 target genes. Promoter analysis and quantitative ChIP analysis demonstrated that FOG1-mediated transcriptional repression of PU.1 would be mediated through a GATA-binding element located at its promoter, accompanied by significantly decreased H3 acetylation at lysine 4 and 9 (K4 and K9) as well as H3K4 trimethylation. Our results provide important mechanistic insight into the role of FOG1 in the regulation of GATA-1-regulated genes and suggest that FOG1 has an important role in inducing cells to differentiate toward the erythroid lineage rather than the myelo-lymphoid one by repressing the expression of PU.1.
转录因子GATA-1相互作用蛋白GATA-1之友（FOG1）对于GATA-1靶基因的正常转录激活和抑制至关重要；然而，FOG1发挥其激活和抑制功能的机制仍不清楚。在人K562红白血病细胞中强制表达FOG1可诱导红系基因（SLC4A1、珠蛋白）的表达，但抑制GATA-2和PU.1的表达。定量染色质免疫沉淀（ChIP）分析表明，在FOG1激活以及FOG1抑制的基因位点，GATA-1在染色质上的占有率均增加。然而，虽然TAL1在染色质上的占有率在FOG1激活的基因位点显著增加，但在FOG1抑制的基因位点则显著降低。当在敲低TAL1的K562细胞中过表达FOG1时，TAL1敲低显著损害了FOG1介导的HBA、HBG和SLC4A1的激活，这表明FOG1可能需要TAL1来激活GATA-1靶基因。启动子分析和定量ChIP分析表明，FOG1介导的PU.1转录抑制将通过位于其启动子的GATA结合元件介导，同时赖氨酸4和9（K4和K9）处的H3乙酰化以及H3K4三甲基化显著降低。我们的结果为FOG1在GATA-1调控基因的调节中的作用提供了重要的机制见解，并表明FOG1通过抑制PU.1的表达在诱导细胞向红系谱系而非髓系-淋巴系谱系分化中起重要作用。
