Functional analysis of the TET2/OGT complex in epigenetic modifications

表观遗传修饰中 TET2/OGT 复合物的功能分析

基本信息

批准号：
9144495
负责人：
Xiaochun Yu
金额：
$ 22.1万
依托单位：
BECKMAN RESEARCH INSTITUTE/CITY OF HOPE
依托单位国家：
美国
项目类别：
财政年份：
2015
资助国家：
美国
起止时间：
2015-01-01 至 2018-12-31
项目状态：
已结题

项目摘要

Abstract: Epigenetic modifications play an important role in gene transcription regulation. One typical example of these epigenetic modifications is DNA methylation. Methylation of DNA is mainly occurred at the 5 position of the cytosine pyrimidine ring in a CpG dinucleotide context, which is catalyzed by DNA methyltransferases. DNA methylation at gene promoter region and transcription start sites regulates gene transcription. Recently, TET family enzymes were shown to oxidize the methylated cytosine in a step towards DNA demethylation. These enzymes specifically convert methylated cytosine (5mC) mainly into hydroxymethylated cytosine (5hmC). Interestingly, unlike DNA demethylation, TET enzymes-dependent oxidation of methylated cytosine is not only associated with transcription activation but also transcription repression. It has been reported that TET1 forms a complex with SIN3A and HDAC1/2, which is involved in transcription repression. To study the molecular mechanism of TET enzyme-dependent DNA demethylation, we examined the associated proteins of TET enzymes using an unbiased protein affinity purification approach, and found OGT as a functional partner of TET2 in mouse ES cells. OGT is the only enzyme that uses UDP-GlcNAc as the donor to catalyze protein O-GlcNAcylation. Our preliminary study shows that OGT interacts with TET2 to form a heterodimer and is targeted to chromatin for histone GlcNAcylation via TET2 in mouse ES cells. Genome- wide profiling of TET2 and OGT suggests that TET2, OGT and OGT-dependent histone GlcNAcylation are associated with active gene transcription in mouse ES cells. Moreover, OGT-dependent histone GlcNAcylation regulates histone H2B ubiquitiation, an active gene transcription mark. Thus, we hypothesize that the OGT/TET2 complex is involved in transcription activation and counteracts TET1-dependent gene silencing. We plan to perform following studies to test our hypothesis. Aim1: To examine the role of the TET2/OGT complex in H2B ubiquitination. Aim2: To investigate the role of the TET2/OGT complex in histone acetylation. Aim3: To study the functional interaction between the TET1 complex and the TET2 complex in transcription regulation. Taken together, the proposed study will comprehensively examine the function of TET enzyme-dependent gene transcription. It might provide novel molecular mechanisms of trans-tail histone modifications that are important for transcription activation.

抽象的：表观遗传修饰在基因转录调节中起重要作用。一个典型的例子这些表观遗传修饰是DNA甲基化。 DNA的甲基化主要发生在5位 CpG二核苷酸环境中的胞嘧啶嘧啶环，由DNA甲基转移酶催化。基因启动子区域和转录起始位点的DNA甲基化调节基因转录。最近，TET家族酶在朝着DNA的一步中显示出氧化甲基化的胞嘧啶脱甲基化。这些酶特异性转化甲基化的胞嘧啶（5MC）主要转化为羟甲基胞嘧啶（5HMC）。有趣的是，与DNA脱甲基化不同，TET酶依赖于甲基化的氧化胞嘧啶不仅与转录激活有关，而且与转录抑制有关。它一直报道TET1与SIN3A和HDAC1/2形成复合物，该复合物与转录抑制有关。为了研究TET酶依赖性DNA脱甲基化的分子机制，我们检查了使用无偏的蛋白亲和纯化方法的TET酶相关蛋白质，并发现OGT 作为小鼠ES细胞中TET2的功能合作伙伴。 OGT是唯一使用UDP-GLCNAC作为催化蛋白O-Glcnacylation的供体。我们的初步研究表明，OGT与TET2相互作用以形成异二聚体，并针对小鼠ES细胞中TET2的组蛋白Glcnacylation靶向染色质。基因组 TET2和OGT的广泛分析表明TET2，OGT和OGT依赖性组蛋白Glcnacylation是与小鼠ES细胞中的活性基因转录相关。此外，OGT依赖性组蛋白Glcnacylation 调节组蛋白H2b泛素化，一个活性基因转录标记。因此，我们假设 OGT/TET2复合物参与转录激活，并抵消TET1依赖性基因沉默。我们计划进行以下研究以检验我们的假设。 AIM1：检查TET2/OGT复合物在H2B泛素化中的作用。 AIM2：研究TET2/OGT复合物在组蛋白乙酰化中的作用。 AIM3：研究转录中TET1复合物与TET2复合物之间的功能相互作用规定。综上所述，拟议的研究将全面研究TET酶依赖性的功能基因转录。它可能会提供新型的分子机制，用于跨尾组蛋白修饰对于转录激活很重要。