Genome-wide Repression of NF-κB Target Genes by Transcription Factor MIBP1 and Its Modulation by O-Linked β-N-Acetylglucosamine (O-GlcNAc) Transferase
Genome-wide Repression of NF-κB Target Genes by Transcription Factor MIBP1 and Its Modulation by O-Linked β-N-Acetylglucosamine (O-GlcNAc) Transferase
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DOI：
10.1074/jbc.m111.298521
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发表时间：
2012-03-23
影响因子：
4.8
通讯作者：
Tahira, Tomoko
中科院分区：
文献类型：
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作者：
Iwashita, Yuji;Fukuchi, Naruhiko;Tahira, Tomoko
转录因子c-myc内含子结合蛋白1(MIBP1)与多种基因组调控区域结合，包括c-myc的内含子1。该因子在胎儿大脑的有丝分裂后神经元中高度表达，并可能参与多种生物学步骤，如神经和免疫过程。在这项研究中，我们在全球范围内表征了MIBP1的转录靶标以及与MIBP1相互作用的蛋白质。基因芯片杂交和基因集浓缩分析表明，当HEK293细胞稳定过表达MIBP1时，参与MYC、核因子-kappa B和转化生长因子-β下游通路的基因下调。在电子转录因子结合位点分析中，这些下调基因的启动子区域显示，核因子-kappa B结合位点的表达最高。在HT1080细胞中，内源性MIBP1被敲除后，已知的NF-kappa B途径中已知基因的上调支持了MIBP1是NF-kappa B途径的下调的观点。我们还证实了MIBP1与NF-kappa B位点的结合。通过免疫沉淀和质谱法，我们检测到O-连接的β-N-乙酰氨基葡萄糖(O-GlcNAc)转移酶是MIBP1的主要结合伙伴。缺失突变体分析表明，MIBP1的154个氨基酸区域是其O-GlcNAc转移酶结合和O-GlcN酰化所必需的。荧光素酶报告实验表明，MIBP1抑制了NF-kappa B反应性表达，且缺失154个氨基酸区域的MIBP1抑制作用更强。我们的结果表明，MIBP1表达的主要作用是下调NF-kappa B通路，这一作用可被O-GlcNAc信号减弱。
The transcription factor c-MYC intron binding protein 1 (MIBP1) binds to various genomic regulatory regions, including intron 1 of c-MYC. This factor is highly expressed in postmitotic neurons in the fetal brain and may be involved in various biological steps, such as neurological and immunological processes. In this study, we globally characterized the transcriptional targets of MIBP1 and proteins that interact with MIBP1. Microarray hybridization followed by gene set enrichment analysis revealed that genes involved in the pathways downstream of MYC, NF-kappa B, and TGF-beta were down-regulated when HEK293 cells stably overexpressed MIBP1. In silico transcription factor binding site analysis of the promoter regions of these down-regulated genes showed that the NF-kappa B binding site was the most overrepresented. The up-regulation of genes known to be in the NF-kappa B pathway after the knockdown of endogenous MIBP1 in HT1080 cells supports the view that MIBP1 is a down-regulator of the NF-kappa B pathway. We also confirmed the binding of the MIBP1 to the NF-kappa B site. By immunoprecipitation and mass spectrometry, we detected O-linked beta-N-acetylglucosamine (O-GlcNAc) transferase as a prominent binding partner of MIBP1. Analyses using deletion mutants revealed that a 154-amino acid region of MIBP1 was necessary for its O-GlcNAc transferase binding and O-GlcNAcylation. A luciferase reporter assay showed that NF-kappa B-responsive expression was repressed by MIBP1, and stronger repression by MIBP1 lacking the 154-amino acid region was observed. Our results indicate that the primary effect of MIBP1 expression is the down-regulation of the NF-kappa B pathway and that this effect is attenuated by O-GlcNAc signaling.