Study the effects of metallic ions on the combination of DNA and histones with molecular combing technique

The effects of monovalent (Na^ , K^ ) and divalent (Mg^2 , Ca^2 , Mn^2 ) ions on the interaction between DNA and histone are studied using the molecular combing technique. λ-DNA molecules and DNA-histone complexes incubated with metal cations (Na^ , K^ , Mg^2 , Ca^2 , Mn^2 ) are stretched on hydrophobic surfaces, and directly observed by fluorescence microscopy. The results indicate that when these cations are added into the DNA solution, the fluorescence intensities of the stained DNA are reduced differently. The monovalent cations (Na^ , K^ ) inhibit binding of histone to DNA. The divalent cations (Mg^2 , Ca^2 , Mn^2 ) enhance significantly the binding of histone to DNA and the binding of the DNA-histone complex to the hydrophobic surface. Mn^2 also induces condensation and aggregation of the DNA- histone complex.     

Study the effects of divalent metallic ions on the combination of DNA and histones with fluorescence anisotropy assays

The effects of divalent ions(Mn2 ,Mg2 ,Ca2 ) on the interaction between DNA and histone are studied using a fluorescence anisotropy assay. Fluorescence anisotropies of DNA and DNA-histone in the presence of divalent ions(Mn2 ,Mg2 ,Ca2 ) are measured. The results indicate that histone reduces the fluorescence anisotropy of lambda DNA while the divalent ions(Mn2 ,Mg2 ,Ca2 ) significantly enhance the fluorescence anisotropy. Compared to the case of DNA incubated with histone alone,there are more histones binding to DNA when divalent ion,histone and DNA are incubated together. We also find that Mn2 makes the DNA-histone complexes more condensed than the other ions do.     

组蛋白甲基化酶Set2片段调控SET结构域催化活性的探讨

以酿酒酵母为研究材料,通过体外甲基化、体内免疫共沉淀等一系列实验,研究了酵母组蛋白甲基转移酶Set2片段调控SET结构域催化活性的机制。发现将SRI 结构域敲除后（1─618片段）,仅催化产生H3K36的单甲基化,将其WW结构域、CC结构域敲除后（1─475片段）,H3K36无法被甲基化。将Set2截取到仅剩SET催化结构域（1─261片段）,H3K36又可被一甲基化和部分的二甲基化修饰。研究结果表明SET结构域的催化活性并非由Set2蛋白自身折叠调控。     

黑腹果蝇种组组蛋白基因间内含子区的分子进化

通过分析黑腹果蝇种组(Drosophila melanogasterspecies group)9个种亚组代表种和D.pseudoobscura的组蛋白基因H2A和H2B的内含子的碱基组成、替换速率、转换/颠换比、二级结构和系统发育关系等发现:整个序列长度变异范围在201 bp(ficusphila)到232 bp(takahashii)之间,替换速率为0.82,转换明显高于颠换,内含子和外显子结合区不遵循“GT-AG”和“AT-AC”模式,而是“TT-AG”模式,二级结构与系统分化关系具有相关性.我们认为组蛋白基因H2A和H2B的内含子是先起源的,在进化过程中由于承受的选择压力不同而发生了变异.     

The conformation alteration of mouse hepatic histones after reacting with nicotinein vitro

UV differential spectroscopy, fluorescence spectroscopy and circular dichroism (CD) spectroscopy assays have been applied to studying the conformation alteration of mouse hepatic histones H1 and H3 after reacting with nicotinein vitro. The results indicate that their conformation changes from regular form to random form with the increasing reaction dose of nicotine. The adduction of nicotine or its metabolites with histones H1 and H3 accounts for the conformation alteration. Nicotine may affect the structure, function and expression of genes of chromosome by changing the conformation of histones.     

Endothelial nitric oxide synthase: insight into cell-specific gene regulation in the vascular endothelium

The vascular endothelium plays a crucial role in regulating normal blood vessel physiology. The gene products responsible are commonly expressed exclusively, or preferentially, in this cell type. However, despite the importance of regulated gene expression in the vascular endothelium, relatively little is known about the mechanisms that restrict endothelial-specific gene expression to this cell type. While significant progress has been made towards understanding the regulation of endothelial genes through cis/trans paradigms, it has become apparent that additional mechanisms must also be operative. For example, chromatin-based mechanisms, including cell-specific DNA methylation patterns and post-translational histone modifications, have recently been demonstrated to play important roles in the cell-specific expression of endothelial nitric oxide synthase (eNOS). This review investigates the involvement of epigenetic regulatory mechanisms in vascular endothelial cell-specific gene expression using eNOS as a prototypical model, and will address the possible contributions of these pathways to diseases of the vasculature. Received 13 September 2005; received after revision 13 October 2005; accepted 19 October 2005     

水稻组蛋白单泛素化连接酶基因(OsHUB1)的克隆及其表达分析

对模式植物拟南芥的研究发现,AtHUB1基因参与调控植物对灰霉病的抗性.为了研究水稻的抗病机理,笔者利用同源搜索从水稻数据库中获得了目标基因的序列,并通过RT-PCR技术从水稻中克隆了组蛋白单泛素化连接酶基因,命名为OsHUB1.该片段包含1个2 655 bp的开放阅读框,编码了1个885氨基酸的多肽.与NCBI数据库的比对结果表明:OsHUB1的氨基酸序列与短柄草(Brachypodium distachyon)、葡萄(Vitis vinifera)、杨树(Populus tomentosa)、大豆(Glycine max)和拟南芥(Arabidopsis thaliana)的泛素E3连接酶的同源性分别为78%,68%,68%,67%和62%.这些不同来源的组蛋白单泛素化连接酶都含有一个高度保守的RING指结构域.半定量表达分析结果表明:OsHUB1基因能够被水杨酸(SA)和茉莉酸(JA)诱导表达,说明OsHUB1基因可能通过SA和JA介导的信号转导途径参与水稻的抗病反应.     

水稻表观遗传的研究进展

从DNA甲基化、组蛋白修饰的形成条件及其作用机制等方面,对表观遗传学的一些常见的发生机制进行了简要综述,并对表观遗传在水稻中研究的前景作了展望．     

Study of the interaction of DNA and histones by spin-stretching and droplet evaporation

Molecular combing is a powerful and simple method for aligning DNA molecules onto a surface. Using this technique combined with fluorescence microscopy, DNA-histone complexes are stretched on a hydrophobic polymethyl methacrylate (PMMA) surface and observed directly. We have developed a new method to stretch single DNA-histone complexes, termed spin-stretching. The results show that the histones markedly enhance DNA binding to the PMMA surface. DNA winds around the histones and therefore decreases in length. The number of histones that bind to each DNA molecule is found to correlate with the histone concentration. The combed DNA-histone complexes are found to depend on two factors: the binding force on the surface and the centrifugal force at its local position. Na+ ions should compete with histones for binding to DNA; however, the observed competitive binding effect of Na+ ions at low concentrations was negligible.     

大鲵鸣叫语图的初步分析

对我国特有两栖动物大鲵的自然鸣叫和电刺激中脑诱发鸣叫进行录音，然后回放至语图仪进行窄带语图分析。结果显示不同状态下的鸣叫在频率、能量和谐波方面均存在差异。