In vivo targeting of de novo DNA methylation by histone modifications in yeast and mouse.
In vivo targeting of de novo DNA methylation by histone modifications in yeast and mouse.
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DOI：
10.7554/elife.06205
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发表时间：
2015-04-07
期刊：
影响因子：
7.7
通讯作者：
Pellegrini M
中科院分区：
文献类型：
--
作者：
Morselli M;Pastor WA;Montanini B;Nee K;Ferrari R;Fu K;Bonora G;Rubbi L;Clark AT;Ottonello S;Jacobsen SE;Pellegrini M
胞嘧啶甲基化（5meC）是一种广泛遗传的DNA修饰。在哺乳动物的发育过程中，两个全球性的去甲基化事件之后是一波又一波的从头DNA甲基化。DNA甲基化建立的体内机制在很大程度上是未知的。在这里，我们使用酿酒酵母作为缺乏DNA甲基化的系统来定义影响小鼠DNMT3B活性的染色质特征。我们的数据表明，DNMT3B和H3K4甲基化是相互排斥的，并且DNMT3B与H3K36甲基化区域共定位。为了支持这一观察结果，在没有Set1和Set2的酵母菌株中的DNA甲基化分析分别显示转录起始位点处的相对5meC水平增加和基因体中的相对5meC水平减少。我们将我们的观察扩展到小鼠雄性生殖系，其中H3K4me3是强反相关的，而H3K36me3与加速的DNA甲基化相关。这些结果表明H3K36甲基化对于体内基因体DNA甲基化的重要性。DOI：http://dx.doi.org/10.7554/eLife.06205.001在动物和其他多细胞生物中，有许多不同类型的细胞，每种细胞在体内扮演特定的角色。这是可能的，因为遗传信息在所有细胞中都是相同的，它是受控的，因此在一个特定的时间，单个细胞中只有一部分基因被“打开”。遗传信息包含在DNA分子中，DNA分子包裹在被称为组蛋白的蛋白质周围。在DNA中，组蛋白紧密堆积的区域的基因倾向于关闭，而松散堆积的区域的基因则倾向于开启。堆积的程度由在组蛋白上添加“甲基”标签来控制。这些标签也可以在称为DNA甲基化的过程中直接添加到DNA中。一种叫做甲基转移酶的酶将标签添加到DNA上，这往往会关闭基因。当DNA在细胞分裂前复制时，甲基标签的位置可以被复制，这样DNA甲基化的模式就可以传递给它的子细胞。然而，甲基转移酶如何能够靶向特定区域进行甲基化尚不清楚。为了解决这个问题，Morselli等人将一种名为DNMT 3b的甲基转移酶引入酵母中，酵母是一种单细胞生物，通常不会在其DNA中添加甲基标签。实验表明，该酶的活性受到某些组蛋白上甲基标签的影响。例如，组蛋白上一个特定位点的甲基标签（称为H3K4）可以阻止DNMT3b酶将甲基标签添加到DNA中。然而，在另一个称为H3K36的位点上的甲基标签促进DNA甲基化。Morselli等人发现，这两个组蛋白位点对小鼠精子细胞中DNA甲基化的影响相似。Morselli等人的发现可能对未来开发癌症和其他由DNA甲基化缺陷引起的疾病的治疗方法有用。DOI：http://dx.doi.org/10.7554/eLife.06205.002网站
Methylation of cytosines (5meC) is a widespread heritable DNA modification. During mammalian development, two global demethylation events are followed by waves of de novo DNA methylation. In vivo mechanisms of DNA methylation establishment are largely uncharacterized. Here, we use Saccharomyces cerevisiae as a system lacking DNA methylation to define the chromatin features influencing the activity of the murine DNMT3B. Our data demonstrate that DNMT3B and H3K4 methylation are mutually exclusive and that DNMT3B is co-localized with H3K36 methylated regions. In support of this observation, DNA methylation analysis in yeast strains without Set1 and Set2 shows an increase of relative 5meC levels at the transcription start site and a decrease in the gene-body, respectively. We extend our observation to the murine male germline, where H3K4me3 is strongly anti-correlated while H3K36me3 correlates with accelerated DNA methylation. These results show the importance of H3K36 methylation for gene-body DNA methylation in vivo. DOI: http://dx.doi.org/10.7554/eLife.06205.001 In animals and other multicellular organisms, there are many different types of cells that each perform particular roles in the body. This is possible because the genetic information—which is the same in all cells—is controlled so that only a subset of all the genes within an individual cell are ‘switched on’ at a particular time. Genetic information is contained within molecules of DNA, which are wrapped around proteins called histones. The genes in regions of DNA where these histones are packed tightly together tend to be switched off, while genes in regions of DNA that are loosely packed tend to be switched on. The level of packaging is controlled by the addition of ‘methyl’ tags to the histone proteins. These tags can also be added directly to the DNA in a process called DNA methylation. Enzymes called methyltransferases add the tags to the DNA, which tends to switch off the gene. The locations of the methyl tags can be copied when the DNA replicates before the cell divides so that the pattern of DNA methylation can be passed on to its daughter cells. However, it is not clear how the methyltransferases are able to target particular regions for methylation. To address this question, Morselli et al. introduced a methyltransferase called DNMT3b into yeast, a single-celled organism that does not normally add methyl tags to its DNA. The experiments show that the activity of the enzyme is affected by the presence of methyl tags on certain histone proteins. For example, a methyl tag at one particular site on a histone, called H3K4, prevents the DNMT3b enzyme from adding methyl tags to DNA. However, a methyl tag at another site called H3K36 promotes DNA methylation. Morselli et al. found that these two histone sites had similar effects on DNA methylation in mouse sperm cells. Morselli et al.'s findings may be useful in the future development of treatments for cancer and other diseases that are caused by defects in DNA methylation. DOI: http://dx.doi.org/10.7554/eLife.06205.002