1.Department of Medical Sciences, Faculty of Medicine, University of Miyazaki, 5200, Kihara, Kiyotake, Miyazaki 88-1692, Japan.
J Leukoc Biol. 2014 Mar;95(3):399-404. doi: 10.1189/jlb.0413232. Epub 2013 Sep 26.
During B-cell differentiation, the gene expression of B-cell differentiation-related transcription factors must be strictly controlled by epigenetic mechanisms including histone acetylation and deacetylation, to complete the differentiation pathway. GCN5, one of the most important histone acetyltransferases, is involved in epigenetic events for transcriptional regulation through alterations in the chromatin structure. In this study, by analyzing the homozygous DT40 mutants GCN5(-/-), generated with gene targeting techniques, we found that GCN5 was necessary for transcriptional activation of IRF-4, an essential transcription factor for plasma cell differentiation. GCN5 deficiency caused drastic decreases in both the mRNA and the protein levels of Blimp-1 and IRF-4. The ectopic expression of Blimp-1 and IRF-4 suggests that IRF-4, but not Blimp-1, is the target gene of GCN5 in immature B cells. Moreover, a chromatin immunoprecipitation assay showed that GCN5 bound to the IRF-4 gene around its 5'-flanking region and acetylated H3K9 residues within chromatin surrounding the region in vivo, suggesting that gene expression of IRF-4 is certainly regulated by GCN5. These results reveal that GCN5 is essential for IRF-4 gene expression, followed by transcriptional activation of Blimp-1, and plays a key role in epigenetic regulation of B-cell differentiation.
在 B 细胞分化过程中，B 细胞分化相关转录因子的基因表达必须受到表观遗传机制（包括组蛋白乙酰化和去乙酰化）的严格控制，以完成分化途径。GCN5 是最重要的组蛋白乙酰转移酶之一，通过改变染色质结构参与转录调控的表观遗传事件。在这项研究中，通过分析同源敲除 DT40 突变体 GCN5(-/-)，我们发现 GCN5 对于浆细胞分化所必需的转录因子 IRF-4 的转录激活是必需的。GCN5 缺陷导致 Blimp-1 和 IRF-4 的 mRNA 和蛋白水平均大幅下降。Blimp-1 和 IRF-4 的异位表达表明，IRF-4 而不是 Blimp-1 是 GCN5 在未成熟 B 细胞中的靶基因。此外，染色质免疫沉淀分析表明，GCN5 在体内结合到 IRF-4 基因的 5'-侧翼区域，并乙酰化该区域周围染色质中的 H3K9 残基，表明 IRF-4 的基因表达确实受到 GCN5 的调控。这些结果表明 GCN5 对于 IRF-4 基因表达、随后的 Blimp-1 转录激活以及 B 细胞分化的表观遗传调控至关重要。
