Regulation of PPARgamma and Adipogenesis by MLL3/MLL4 complex

MLL3/MLL4 复合物对 PPARgamma 和脂肪生成的调节

• 批准号: 8939678
• 负责人: Kai Ge
• 金额: $ 72.5万
• 依托单位: NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8939678
• 关键词: Accounting; Binding; Biological; Biological Models; CCAAT-Enhancer-Binding Proteins; Cell Differentiation process; Cell Nucleus; Cells; Complex; Defect; Diabetes Mellitus; Embryo; Embryonic Development; Enhancers; Enzymes; Exhibits; Fatty acid glycerol esters; Gene Expression; Generations; Genomics; Histones; Knock-out; Lead; Ligands; Mediator of activation protein; Methyltransferase; Molecular; Mono-S; Morbidity - disease rate; Mus; Non-Insulin-Dependent Diabetes Mellitus; Nuclear Protein; Nuclear Receptors; Obesity; PPAR gamma; Peroxisome Proliferator-Activated Receptors; Physiological; Play; Polymerase; Proteins; Regulation; Risk Factors; Role; Staging; Tissues; activating transcription factor; cell type; embryonic stem cell; lipid biosynthesis; member; mortality; myogenesis; novel; novel strategies; obesity treatment; protein complex; stem cell differentiation; transcription factor

My lab previously identified H3K4 methyltransferases MLL3 and MLL4 (Cho YW, JBC 2007) and H3K27 demethylases UTX and JMJD3 (Hong S, PNAS 2007). Using a nuclear protein PTIP as the bait, we isolated from cell nuclei a protein complex that contains H3K4 methyltransferases MLL3/MLL4, H3K27 demethylase UTX, PTIP and a novel protein PA1 (Cho YW, JBC 2007). Further, we show that PTIP is required for PPARγ and C/EBPα expression and adipogenesis (Cho, YW, Cell Metab 2009). To understand the physiological roles of MLL3/MLL4 and associated factors, we have knocked out MLL3, MLL4, UTX and PA1 in mice. Because of their embryonic lethality, we have generated conditional knockout (KO) of MLL4, UTX and PA1. By crossing these conditional KO with Myf5-Cre mice, we found that MLL4, PTIP and PA1 are essential for adipogenesis while UTX is dispensable. To investigate UTX function, we turned to mouse embryonic stem (ES) cells. We found that UTX controls ES cell differentiation and early embryonic development independent of H3K27 demethylase activity (Wang C, PNAS 2012). To understand the biological role of the H3K27 demethylase activity of UTX, we have generated enzyme-dead UTX knockin mice. We recently identify MLL3/MLL4 as H3K4 mono- and di-methyltransferases that are essential for enhancer activation during cell differentiation (Lee JE, eLife 2013). Enhancers play a central role in cell-type-specific gene expression and are marked by H3K4me1/2. Active enhancers are further marked by H3K27ac. However, the methyltransferases responsible for H3K4me1/2 on enhancers remain elusive. Furthermore, how these enzymes function on enhancers to regulate cell-type-specific gene expression is unclear. We identify MLL4 as a major mammalian H3K4 mono- and di-methyltransferase with partial functional redundancy with MLL3. Using adipogenesis and myogenesis as model systems, we show that MLL4 exhibits cell-type- and differentiation-stage-specific genomic binding and is predominantly localized on enhancers. MLL4 co-localizes with lineage-determining transcription factors (TFs) on active enhancers during differentiation. Deletion of MLL4 markedly decreases H3K4me1/2, H3K27ac, Mediator and Polymerase II (Pol II) levels on enhancers and leads to severe defects in cell-type-specific gene expression and cell differentiation. Together, these findings identify MLL3/MLL4 as major mammalian H3K4 mono- and di-methyltransferases essential for enhancer activation during cell differentiation.

我的实验室先前鉴定出H3K4甲基转移酶MLL3和MLL4（Cho YW，JBC 2007）和H3K27脱甲基酶UTX和JMJD3（Hong S，PNAS 2007）。使用核蛋白PTIP作为诱饵，我们从包含H3K4甲基转移酶MLL3/MLL4，H3K27脱甲基酶UTX，PTIP和一种新型蛋白质PA1的蛋白质复合物中分离出来（Cho YW，JBC 2007）。此外，我们表明PTIP是PPARγ和C/EBPα表达和脂肪形成所必需的（Cho，YW，Cell Metab 2009）。为了了解MLL3/MLL4和相关因素的生理作用，我们在小鼠中淘汰了MLL3，MLL4，UTX和PA1。由于它们的胚胎致死性，我们产生了MLL4，UTX和PA1的条件敲除（KO）。通过将这些条件KO与MyF5-CRE小鼠跨越，我们发现MLL4，PTIP和PA1对于脂肪形成至关重要，而UTX是可分配的。为了研究UTX函数，我们转向小鼠胚胎茎（ES）细胞。我们发现，UTX控制ES细胞分化和早期胚胎发育，独立于H3K27脱甲基酶活性（Wang C，PNAS 2012）。为了了解UTX的H3K27脱甲基活性的生物学作用，我们已经产生了酶已导致的UTX敲击蛋白小鼠。最近，我们将MLL3/MLL4识别为H3K4单单和DI-甲基转移酶，对于在细胞分化过程中增强子激活至关重要（Lee JE，Elife，Elife 2013）。增强剂在细胞类型特异性基因表达中起着核心作用，并以H3K4ME1/2标记。主动增强子由H3K27AC进一步标记。但是，负责H3K4me1/2在增强子上的甲基转移酶仍然难以捉摸。此外，这些酶在增强剂中的作用如何调节细胞类型的基因表达尚不清楚。我们将MLL4鉴定为具有MLL3的部分功能冗余性的主要哺乳动物H3K4单甲基转移酶。使用脂肪形成和肌发生作为模型系统，我们表明MLL4表现出细胞类型和分化阶段特异性的基因组结合，并且主要位于增强子上。 MLL4在分化过程中与谱系确定的转录因子（TF）共定位。 MLL4的缺失显着降低了H3K4ME1/2，H3K27AC，介体和聚合酶II（POL II）水平（POL II）水平，并导致细胞型特异性基因表达和细胞分化的严重缺陷。总之，这些发现将MLL3/MLL4鉴定为主要的哺乳动物H3K4单单和DI-甲基转移酶，对于在细胞分化过程中增强激活所必需的必不可少。