组蛋白赖氨酸甲基转移酶2D调控H9c2细胞中HIF-1α/VEGF通路

组蛋白赖氨酸甲基转移酶2D (histone-lysine N-methyltransferase 2D, KMT2D) 作为主要的组蛋白3第4位赖氨酸 (H3K4) 甲基转移酶,在调控胚胎发育、组织分化、代谢和肿瘤抑制方面发挥重要作用。在小鼠体内,敲除Kmt2d会导致严重的心脏发育缺陷最终造成胚胎期死亡。低氧诱导因子-1α (hypoxia-inducible factor 1α, HIF-1α) 作为调节细胞应对低氧的关键转录因子,能够调控多种下游基因转录。有相关研究揭示,表观遗传调控者能够调节HIF-1α的稳定性和活性。同样,作为表观遗传调控者的组蛋白甲基转移酶KMT2D是否参与低氧条件下HIF-1α对下游基因的调控,目前仍未知。在本研究中,观察在Kmt2d正常或缺乏的情况下,心肌细胞H9c2对低氧环境的应答反应。结果显示,与常氧条件相比,低氧状态下HIF-1α、组蛋白乙酰化酶P300、KMT2D及其介导的H3K4一甲基化 (H3K4 mono-methylation, H3K4me1)的蛋白质水平增加 (P<0.05);HIF-1α下游基因血管内皮生长因子 (vascular endothelial growth factor, Vegf) 的mRNA表达水平明显上调 (P<0.01)。染色质免疫共沉淀实验 (chromatin immunoprecipitation assay, ChIP-qPCR) 检测结果显示,H3K4me1和组蛋白3第27位赖氨酸乙酰化 (histone 3 lysine 27 acetylation, H3K27ac) 在Vegf基因启动子区域的结合丰度明显增加 (P<0.05)。低氧条件下沉默Kmt2d之后,H3K4me1蛋白水平和Vegf的mRNA表达下降 (P<0.05)。本研究表明,低氧条件下KMT2D参与调控HIF-1α和下游基因Vegf的表达。     

组蛋白赖氨酸甲基转移酶2D调控H9c2细胞中HIF-1α/VEGF通路（英文）

组蛋白赖氨酸甲基转移酶2D (histone-lysine N-methyltransferase 2D, KMT2D)作为主要的组蛋白3第4位赖氨酸(H3K4)甲基转移酶,在调控胚胎发育、组织分化、代谢和肿瘤抑制方面发挥重要作用。在小鼠体内,敲除Kmt2d会导致严重的心脏发育缺陷最终造成胚胎期死亡。低氧诱导因子-1α(hypoxia-inducible factor 1α, HIF-1α)作为调节细胞应对低氧的关键转录因子,能够调控多种下游基因转录。有相关研究揭示,表观遗传调控者能够调节HIF-1α的稳定性和活性。同样,作为表观遗传调控者的组蛋白甲基转移酶KMT2D是否参与低氧条件下HIF-1α对下游基因的调控,目前仍未知。在本研究中,观察在Kmt2d正常或缺乏的情况下,心肌细胞H9c2对低氧环境的应答反应。结果显示,与常氧条件相比,低氧状态下HIF-1α、组蛋白乙酰化酶P300、KMT2D及其介导的H3K4一甲基化(H3K4 mono-methylation, H3K4me1)的蛋白质水平增加(P0.05);HIF-1α下游基因血管内皮生长因子(vascular endothelial growth factor, Vegf)的mRNA表达水平明显上调(P0.01)。染色质免疫共沉淀实验(chromatin immunoprecipitation assay, ChIP-qPCR)检测结果显示,H3K4me1和组蛋白3第27位赖氨酸乙酰化(histone 3 lysine 27 acetylation, H3K27ac)在Vegf基因启动子区域的结合丰度明显增加(P0.05)。低氧条件下沉默Kmt2d之后,H3K4me1蛋白水平和Vegf的mRNA表达下降(P0.05)。本研究表明,低氧条件下KMT2D参与调控HIF-1α和下游基因Vegf的表达。     

组蛋白赖氨酸甲基化在表观遗传调控中的作用

组蛋白赖氨酸的甲基化在表观遗传调控中起着关键作用。组蛋白H3的K4、K9、K27、K36、K79和H4的K20均可被甲基化。组蛋白H3第9位赖氨酸的甲基化与基因的失活相关连; 组蛋白H3第4位赖氨酸和第36位赖氨酸的甲基化与基因的激活相关连; 组蛋白H3第27位赖氨酸的甲基化与同源盒基因沉默、X染色体失活、基因印记等基因沉默现象有关; 组蛋白H3第79位赖氨酸的甲基化与防止基因失活和DNA修复有关。与此同时, 组蛋白的去甲基化也受到更为广泛的关注。 关键词: 组蛋白赖氨酸甲基转移酶; 组蛋白赖氨酸甲基化; 组蛋白去甲基化     

水稻SDG736抑制拟南芥FLC表达调控开花时间

130～150个氨基酸组成SET (Su (var) 3-9, Enhancer-of-zeste, Trithorax)结构域构成了组蛋白赖氨酸甲基转移酶特异性催化位点。SET结构域蛋白在进化上高度保守,广泛调控植物的生长发育。进化分析结果显示水稻SET结构域家族成员可分为7个不同的亚家族(KMT1, KMT2, KMT3, KMT6, KMT7, S-ET和RMT)。KMT3亚家族可能涉及开花调控或花的发育,其中包含5个拟南芥基因和5个水稻同源基因。拟南芥SDG4通过H3K4/K36甲基化的活性调控花发育,结果表明水稻同源基因SDG736超量表达,可促进拟南芥开花。对拟南芥开花途径相关的基因进行定量分析显示,超量表达的SDG736拟南芥植株中FLC基因表达量降低,而SCO1基因的表达量增加。     

组蛋白去甲基化酶KDM5A调控H3K4me3参与神经管畸形发生的分子机制

神经管畸形(NTDs)的病因与防治是出生缺陷领域研究的重点,叶酸可以预防神经管畸形但其机制不明。本文借助低叶酸细胞模型和低叶酸NTDs小鼠模型通过染色质免疫共沉淀、Cut&Tag等技术,探讨了组蛋白去甲基化酶lysine demethylase 5A(KDM5A)及其调控的下游组蛋白H3K4me3修饰在叶酸缺乏导致的NTDs发生中的潜在分子机制。结果显示,低叶酸的细胞模型中,qRT-PCR、Western印迹结果显示,KDM5A分子表达明显下降(P<0.05)。作为组蛋白H3K4me3调控的上游关键酶,进一步通过染色质免疫共沉淀ChIP、ChIP-qPCR实验证实,叶酸缺乏下组蛋白H3K4me3在神经发育基因Axin2和Atoh1基因启动子区富集增加(P<0.05)。通过构建KDM5A基因敲除细胞模型,借助Cut&Tag试验证实,KDM5A基因敲除后H3K4me3主要富集在神经发育基因上。最后在低叶酸导致的NTDs小鼠模型的脑组织中,RT-qPCR、Western印迹以及ChIP-qPCR实验显示,E9.5 d的NTDs胎鼠脑组织中KDM5A表达下降(P&l...     

植物组蛋白赖氨酸甲基化建立过程及其遗传性研究进展

表观遗传学主要包括DNA甲基化、组蛋白修饰和非编码RNA,组蛋白甲基化作为组蛋白修饰中的一种重要修饰,在植物体的发育和环境适应中发挥着重要作用。组蛋白甲基化主要发生在赖氨酸残基上,同时根据不同的赖氨酸位点和每个赖氨酸位点甲基化程度的不同,形成了不同的赖氨酸甲基化修饰。根据对基因的不同功能,通常将组蛋白赖氨酸甲基化修饰分为2大类:(1)能够促进基因表达的,如H3K4me3和H3K36me3;(2)能够抑制基因表达的,如H3K9me2和H3K27me3。不同的组蛋白赖氨酸甲基化去甲基化过程需要相应的阅读(reader)、书写(writer)和擦除(eraser)3种蛋白。同时,组蛋白赖氨酸甲基化的遗传性质目前还不是很清楚。综述了植物中组蛋白赖氨酸甲基化建立与去除过程,以及对组蛋白赖氨酸甲基化可遗传性的探讨。     

植物组蛋白赖氨酸化修饰参与基因表达调控的机理

组蛋白共价修饰作为表观遗传修饰的重要部分,主要包括乙酰化和甲酰化、甲基化、磷酸化、泛素化和SUMO化等,它们形成一个复杂的网络共同调控基因的表达,其中组蛋白甲基化修饰成为研究的热点,甲基化主要发生在赖氨酸残基上。近年来,随着有关植物组蛋白赖氨酸甲基化修饰研究的不断深入,发现其通过改变自身赖氨酸残基的甲基化状态和甲基化程度,形成转录激活或者转录抑制标记,调控基因的表达,在植物开花和逆境胁迫的响应过程中起着至关重要的作用。H3组蛋白的赖氨酸甲基化修饰能够调控FLC基因和有关抗性基因的表达,具体表现为:H3K4的三甲基化促进FLC的表达,H3K27的三甲基化则抑制FLC的表达;H3K4me3作为转录激活标记,可激活PtdIns5P基因的表达,启动响应干旱的脂质合成信号通路,响应干旱胁迫;相反,H3K27me3作为一种转录抑制标记,低水平的H3K27me3诱导COR15A和ATGOLS3基因表达,它们分别编码叶绿体低温保护蛋白Cor15am和肌醇半乳糖合成酶GOLS,以抵抗寒冷胁迫。文章主要综述了植物组蛋白赖氨酸甲基化修饰参与DNA甲基化、开花过程以及应答逆境胁迫的分子机制。     

Ezh2与G9a在Msx1抑制成肌细胞分化过程中的协同作用

组蛋白H3第27位赖氨酸的三甲基化(H3K27me3)和第9位赖氨酸的二甲基化(H3K9me2)参与很多重要的生物学过程,如与基因转录调控和细胞分化密切相关。H3K27me3和H3K9me2分别由赖氨酸甲基转移酶(KMTs)Ezh2和G9a催化形成。在基因转录调控和细胞分化调控过程中Ezh2和G9a之间是否存在协同,目前还不清楚。我们的前期研究表明,在成肌细胞中,同源异型框蛋白(homeoprotein)Msx1可分别招募Ezh2和G9a到其抑制靶标基因,通过影响其靶标基因的H3K27me3和H3K9me2的状态来抑制靶基因的表达,从而抑制肌肉细胞的分化。为了进一步探究Ezh2和G9a在Msx1介导的抑制成肌细胞分化过程中是否具有协同作用,我们对比了同时敲低Ezh2和G9a与分别敲低Ezh2或G9a对Msx1抑制成肌细胞分化、结合并抑制靶标基因能力的影响,研究显示双敲的影响更大。我们的研究表明,在Msx1抑制成肌细胞分化的过程中,Ezh2和G9a具有协同作用。另外,我们的研究为基因转录调控和细胞分化提供了新的分子机制。     

DOT1—— 一类新的组蛋白赖氨酸甲基转移酶

组蛋白甲基化是一种重要的组蛋白共价修饰, 在染色质结构和基因表达的调控过程中起着重要的、多样化的作用。DOT1催化核心球体部位的组蛋白H3第79位赖氨酸(H3K79)使其发生甲基化, 是首个被发现的无SET结构域的组蛋白赖氨酸甲基转移酶, 代表了一类新的组蛋白赖氨酸甲基转移酶。DOT1及H3K79甲基化的特点决定了其可能具有重要的、特殊的生物学功能。文章重点综述了DOT1蛋白的结构及特点, DOT1及H3K79甲基化的生物学功能以及组蛋白泛素化修饰对H3K79甲基化的反式调控。     

组蛋白甲基转移酶G9a在表观遗传调控中的作用

组蛋白赖氨酸甲基化在表观遗传调控中起着关键作用。组蛋白甲基转移酶G9a(又称作常染色质组蛋白赖氨酸N-甲基转移酶2(euchromatic histone-lysine N-methyltransferase 2,EHMT2))含经典的SET结构域,是常染色质主要的甲基转移酶之一,可以甲基化组蛋白H3K9、H3K27和H1bK26等。此外,G9a也可以直接甲基化一些非组蛋白,并与DNA甲基化密切相关。G9a功能紊乱可以导致胚胎发育异常、免疫系统及神经系统发育障碍、甚至癌症的发生发展。     

KMT2D deficiency disturbs the proliferation and cell cycle activity of dental epithelial cell line (LS8) partially via Wnt signaling

Lysine methyltransferase 2D (KMT2D), as one of the key histone methyltransferases responsible for histone 3 lysine 4 methylation (H3K4me), has been proved to be the main pathogenic gene of Kabuki syndrome disease. Kabuki patients with KMT2D mutation frequently present various dental abnormalities, including abnormal tooth number and crown morphology. However, the exact function of KMT2D in tooth development remains unclear. In this report, we systematically elucidate the expression pattern of KMT2D in early tooth development and outline the molecular mechanism of KMT2D in dental epithelial cell line. KMT2D and H3K4me mainly expressed in enamel organ and Kmt2d knockdown led to the reduction in cell proliferation activity and cell cycling activity in dental epithelial cell line (LS8). RNA-sequencing (RNA-seq) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis screened out several important pathways affected by Kmt2d knockdown including Wnt signaling. Consistently, Top/Fop assay confirmed the reduction in Wnt signaling activity in Kmt2d knockdown cells. Nuclear translocation of β-catenin was significantly reduced by Kmt2d knockdown, while lithium chloride (LiCl) partially reversed this phenomenon. Moreover, LiCl partially reversed the decrease in cell proliferation activity and G₁ arrest, and the down-regulation of Wnt-related genes in Kmt2d knockdown cells. In summary, the present study uncovered a pivotal role of histone methyltransferase KMT2D in dental epithelium proliferation and cell cycle homeostasis partially through regulating Wnt/β-catenin signaling. The findings are important for understanding the role of KMT2D and histone methylation in tooth development.     

A lesson learned from the H3.3K27M mutation found in pediatric glioma

Glioblastoma (GBM) is the most aggressive primary brain tumor in human. Recent studies on high-grade pediatric GBM have identified two recurrent mutations (K27M and G34R/V) in genes encoding histone H3 (H3F3A for H3.3 and HIST1H3B for H3.1).^1,2 The two histone H3 mutations are mutually exclusive and give rise to tumors in different brain compartments.³ Recently, we⁴ and others⁵ have shown that the histone H3 K27M mutation specifically altered the di- and tri-methylation of endogenous histone H3 at Lys27. Genome-wide studies using ChIP-seq on H3.3K27M patient samples indicate a global reduction of H3K27me3 on chromatin. Remarkably, we also found a dramatic enrichment of H3K27me3 and EZH2 (the catalytic subunit H3K27 methyltransferase) at hundreds of gene loci in H3.3K27M patient cells. Here, we discuss potential mechanisms whereby H3K27me3 is enriched at chromatin loci in cells expressing the H3.3K27M mutation and report effects of Lys-to-Met mutations of other well-studied lysine residues of histone H3.1/H3.3 and H4 on the corresponding endogenous lysine methylation. We suggest that mutation(s) on histones may be found in a variety of human diseases, and the expression of mutant histones may help to address the function of histone lysine methylation and possibly other modifications in mammalian cells.     

The histone methyltransferase Dot1 is required for DNA damage repair and proper development in Dictyostelium

Posttranslational histone modifications play an important role in modulating gene expression and chromatin structure. Here we report the identification of histone H3K79 dimethylation in the simple eukaryote Dictyostelium discoideum. We have deleted the D. discoideum Dot1/KMT4 homologue and demonstrate that it is the sole enzyme responsible for histone H3K79me2. Cells lacking Dot1 are reduced in growth and delayed in development, but do not show apparent changes in cell cycle regulation. Furthermore, our results indicate that Dot1 contributes to UV damage resistance and DNA repair in D. discoideum. In summary, the data support the view that the machinery controlling the setting of histone marks is evolutionary highly conserved and provide evidence that D. discoideum is a suitable model system to analyze these modifications and their functions during development and differentiation.     

Postnatal expression of the lysine methyltransferase SETD1B is essential for learning and the regulation of neuron‐enriched genes

In mammals, histone 3 lysine 4 methylation (H3K4me) is mediated by six different lysine methyltransferases. Among these enzymes, SETD1B (SET domain containing 1b) has been linked to syndromic intellectual disability in human subjects, but its role in the mammalian postnatal brain has not been studied yet. Here, we employ mice deficient for Setd1b in excitatory neurons of the postnatal forebrain, and combine neuron‐specific ChIP‐seq and RNA‐seq approaches to elucidate its role in neuronal gene expression. We observe that Setd1b controls the expression of a set of genes with a broad H3K4me3 peak at their promoters, enriched for neuron‐specific genes linked to learning and memory function. Comparative analyses in mice with conditional deletion of Kmt2a and Kmt2b histone methyltransferases show that SETD1B plays a more pronounced and potent role in regulating such genes. Moreover, postnatal loss of Setd1b leads to severe learning impairment, suggesting that SETD1B‐dependent regulation of H3K4me levels in postnatal neurons is critical for cognitive function.     

HIF-1-Dependent Induction of Jumonji Domain-Containing Protein (JMJD) 3 under Hypoxic Conditions

Jumonji domain-containing proteins (JMJD) catalyze the oxidative demethylation of a methylated lysine residue of histones by using O₂, α-ketoglutarate, vitamin C, and Fe(II). Several JMJDs are induced by hypoxic stress to compensate their presumed reduction in catalytic activity under hypoxia. In this study, we showed that an H3K27me3 specific histone demethylase, JMJD3 was induced by hypoxia-inducible factor (HIF)-1α/β under hypoxia and that treatment with Clioquinol, a HIF-1α activator, increased JMJD3 expression even under normoxia. Chromatin immunoprecipitation (ChIP) analyses showed that both HIF-1α and its dimerization partner HIF-1β/Arnt occupied the first intron region of the mouse JMJD3 gene, whereas the HIF-1α/β heterodimer bound to the upstream region of the human JMJD3, indicating that human and mouse JMJD3 have hypoxia-responsive regulatory regions in different locations. This study shows that both mouse and human JMJD3 are induced by HIF-1.     

Mitotic Accumulation of Dimethylated Lysine 79 of Histone H3 Is Important for Maintaining Genome Integrity During Mitosis in Human Cells

The loss of genome stability is an early event that drives the development and progression of virtually all tumor types. Recent studies have revealed that certain histone post-translational modifications exhibit dynamic and global increases in abundance that coincide with mitosis and exhibit essential roles in maintaining genomic stability. Histone H2B ubiquitination at lysine 120 (H2Bub1) is regulated by RNF20, an E3 ubiquitin ligase that is altered in many tumor types. Through an evolutionarily conserved trans-histone pathway, H2Bub1 is an essential prerequisite for subsequent downstream dimethylation events at lysines 4 (H3K4me2) and 79 (H3K79me2) of histone H3. Although the role that RNF20 plays in tumorigenesis has garnered much attention, the downstream components of the trans-histone pathway, H3K4me2 and H3K79me2, and their potential contributions to genome stability remain largely overlooked. In this study, we employ single-cell imaging and biochemical approaches to investigate the spatial and temporal patterning of RNF20, H2Bub1, H3K4me2, and H3K79me2 throughout the cell cycle, with a particular focus on mitosis. We show that H2Bub1, H3K4me2, and H3K79me2 exhibit distinct temporal progression patterns throughout the cell cycle. Most notably, we demonstrate that H3K79me2 is a highly dynamic histone post-translational modification that reaches maximal abundance during mitosis in an H2Bub1-independent manner. Using RNAi and chemical genetic approaches, we identify DOT1L as a histone methyltransferase required for the mitotic-associated increases in H3K79me2. We also demonstrate that the loss of mitotic H3K79me2 levels correlates with increases in chromosome numbers and increases in mitotic defects. Collectively, these data suggest that H3K79me2 dynamics during mitosis are normally required to maintain genome stability and further implicate the loss of H3K79me2 during mitosis as a pathogenic event that contributes to the development and progression of tumors.     

NSD2 promotes ventricular remodelling mediated by the regulation of H3K36me2

Histone lysine methylation plays an important role in the regulation of ventricular remodelling. NSD2 is involved in many types of tumours through enhancing H3K36me2 expression. However, the role of NSD2 in the regulation of histone lysine methylation during ventricular remodelling remains unclear. In this study, we established cardiac hypertrophy model in C57BL/6 mice by transverse aortic constriction and found that histone lysine methylation participated in ventricular remodelling regulation via the up‐regulation of H3K27me2 and H3K36me2 expression. In addition, we constructed transgenic C57BL/6 mice with conditional knockout of NSD2 (NSD2^?/?) in the myocardium. NSD2^?/? C57BL/6 mice had milder ventricular remodelling and significantly improved cardiac function compared with wild‐type mice, and the expression of H3K36me2 but not H3K27me2 was down‐regulated. In conclusion, NSD2 promotes ventricular remodelling mediated by the regulation of H3K36me2.