DNA repair mechanisms in dividing and non-dividing cells

DNA damage created by endogenous or exogenous genotoxic agents can exist in multiple forms, and if allowed to persist, can promote genome instability and directly lead to various human diseases, particularly cancer, neurological abnormalities, immunodeficiency and premature aging. To avoid such deleterious outcomes, cells have evolved an array of DNA repair pathways, which carry out what is typically a multiple-step process to resolve specific DNA lesions and maintain genome integrity. To fully appreciate the biological contributions of the different DNA repair systems, one must keep in mind the cellular context within which they operate. For example, the human body is composed of non-dividing and dividing cell types, including, in the brain, neurons and glial cells. We describe herein the molecular mechanisms of the different DNA repair pathways, and review their roles in non-dividing and dividing cells, with an eye toward how these pathways may regulate the development of neurological disease.     

Backbone dynamics of alamethicin bound to lipid membranes: spin-echo electron paramagnetic resonance of TOAC-spin labels

Alamethicin F50/5 is a hydrophobic peptide that is devoid of charged residues and that induces voltage-dependent ion channels in lipid membranes. The peptide backbone is likely to be involved in the ion conduction pathway. Electron spin-echo spectroscopy of alamethicin F50/5 analogs in which a selected Aib residue (at position n = 1, 8, or 16) is replaced by the TOAC amino-acid spin label was used to study torsional dynamics of the peptide backbone in association with phosphatidylcholine bilayer membranes. Rapid librational motions of limited angular amplitude were observed at each of the three TOAC sites by recording echo-detected spectra as a function of echo delay time, 2τ. Simulation of the time-resolved spectra, combined with conventional EPR measurements of the librational amplitude, shows that torsional fluctuations of the peptide backbone take place on the subnanosecond to nanosecond timescale, with little temperature dependence. Associated fluctuations in polar fields from the peptide could facilitate ion permeation.     

新疆艾比湖湿地自然保护区植物的生态分组

应用列联表的χ~2检验和Spearman相关系数研究了艾比湖湿地自然保护区植物的种间联结性和相关性.依据测定结果,将艾比湖湿地自然保护区的植物划分为4个生态种组:梭梭+盐节木+白麻+盐爪爪+琵琶柴+碱蓬+花花柴+骆驼刺+绢蒿+白刺+芦苇、小獐茅+多枝柽柳+滨藜+小叶碱蓬+盐豆木+鹅绒藤+盐穗木、胡杨+白梭梭、奶浆草+甘草+西北天门冬+赖草+罗布麻.各生态种组内,物种间具备最大的种问联结性和相关性.长期的演替过程使各生态种组对生境有最大的适应能力,各自分别生活于过渡带的盐化平原低地、湖滨盐沼地、荒漠和荒漠优势种间的阳斑.今后在艾比湖湿地自然保护区植物的保护和恢复中,以整个生态种组的角度出发较单个植物的保护和恢复更为有效.     

Tuning of the Zernike phase-plate for visualization of detailed ultrastructure in complex biological specimens

In order to acquire phase-contrast images with adequate contrast, conventional TEM requires large amount of defocus. Increasing the defocus improves the low-frequency components but attenuates the high-frequency ones. On the other hand, Zernike phase-contrast TEM (ZPC-TEM) can recover low-frequency components without losing the high-frequency ones under in-focus conditions. ZPC-TEM however, has another problem, especially in imaging of complex biological specimens such as cells and tissues; strong halos appear around specimen structures, and these halos hinder the interpretation of images. Due to this problem, the application of ZPC-TEM has been restricted to imaging of smaller particles. In order to improve the halo appearance, we fabricated a new quarter-wave thin film phase-plate with a smaller central hole and tested it on vitreous biological specimens. ZPC-TEM with the new plate could successfully visualize, in in-focus images, the intracellular fine features of cultured cells and brain tissues. This result indicates that reduction of the central hole diameter makes ZPC-TEM applicable on size scales ranging from protein particles to tissue sections. The application of ZPC-TEM to vitreous biological specimens will be a powerful method to advance the new field of imaging science for ultrastructures in close-to-physiological state.     

8-氯腺苷诱导的组蛋白H3K79双甲基化促进NBS1和p21的基因转录激活

组蛋白H3第79位赖氨酸甲基化（H3K79me）修饰有单甲基、双甲基及三甲基3种形式,是常染色质的标志.然而,对于组蛋白H3K79三种甲基化各自在基因转录、DNA损伤修复中所起的作用尚不十分清楚.本研究以8-氯腺苷（8-Cl-Ado）为DNA双链断裂（DNA double-stranded breaks,DSB）诱导剂,采用Western 印迹,在人肺癌细胞H1299检测出了DNA修复分子NBS1、细胞周期检验点相关分子p21,并发现H3K79me1、H3K79me2和H3K79me3三种甲基化修饰的组蛋白明显增加;染色质免疫共沉淀结合实时定量PCR实验显示,只H3K79me2与DNA损伤检验点分子p21、DNA修复分子NBS1的启动子区域相结合,说明H3K79双甲基化修饰与这些基因的转录激活有关.结果提示,在8-氯腺苷引起 DSB时,是H3K79me2、而不是H3K79me1和H3K79me3参与NBS1和p21基因转录激活时的染色质重塑.8-氯腺苷诱导H3K79双甲基化增强、促进H3K79me2所在染色质区域的NBS1和p21基因转录激活可能是8-Cl-Ado抑制肿瘤细胞生长作用机制之一.     

Mechanisms of cohesin-mediated gene regulation and lessons learned from cohesinopathies

Cohesins are conserved and essential Structural Maintenance of Chromosomes (SMC) protein-containing complexes that physically interact with chromatin and modulate higher-order chromatin organization. Cohesins mediate sister chromatid cohesion and cellular long-distance chromatin interactions affecting genome maintenance and gene expression. Discoveries of mutations in cohesin's subunits and its regulator proteins in human developmental disorders, so-called “cohesinopathies,” reveal crucial roles for cohesins in development and cellular growth and differentiation. In this review, we discuss the latest findings concerning cohesin's functions in higher-order chromatin architecture organization and gene regulation and new insight gained from studies of cohesinopathies. This article is part of a Special Issue entitled: Chromatin and epigenetic regulation of animal development.     

Kidney proteome responses in the teleost fish Paralichthys olivaceus indicate a putative immune response against Streptococcus parauberis

The proteomic response to bacterial infection in a teleost fish (Paralichthys olivaceus) infected with Streptococcus parauberis was analyzed using label-free protein quantitation coupled with LC-MS(E) tandem mass spectrometry. A total of 82 proteins from whole kidney, a major lymphoid organ in this fish, were found to be differentially expressed between healthy and diseased fish analyzed 6, 24, 72 and 120 h post-infection. Among the differentially expressed proteins, those involved in mediating immune responses (e.g., heat shock proteins, cathepsins, goose-type lysozyme and complement components) were most significantly up-regulated by infection. In addition, cell division cycle 48 (CDC48) and calreticulin, which are associated with cellular recovery and glycoprotein synthesis, were up-regulated in the universal protein group, whereas the other proteins in that group were down-regulated. There was continuous activation of expression of immune-associated proteins during infection, but there was also loss of expression of proteins not involved in immune function. We expect that our findings regarding immune response at the protein level would offer new insight into the systemic response to bacterial infection of a major immune organ in teleost fish.     

The Presence of (+)-S-Adenosyl-l-Methionine in the Rat Brain and Its Lack of Effect on Phenylethanolamine N-Methyltransferase Activity

Abstract: (+)-S-Adenosyl- l -methionine [(+)-SAM] was isolated from rat brain and was quantified by HPLC followed by UV spectrophotometric measurements and by ¹H-NMR. Its estimated ratio in brain is 3% of total SAM. Because of its commercial unavailability, (+)-SAM was also prepared from chemically synthesized SAM by separation of the two diastereoisomers on a preparative reverse-phase Nucleosil C8 column. The (+) diastereoisomer thus obtained was then assayed in vitro both as an inhibitor and a substrate of phenylethanolamine N -methyltransferase. Enzymatic activity was measured by HPLC analysis. It was shown that (+)-SAM has no effect on phenylethanolamine N -methyltransferase activity; therefore, it is unlikely that (+)-SAM plays any possible role in regulation of adrenaline synthesis in the brain.     

利用秆维管束进行中国散生竹类的聚类分析

本文是应用模糊聚类分析方法研究中国散生竹类分类的一次尝试。分类特征采用了竹秆上、中、下三段各类型维管束数,方法上使用了模糊(Fuzzy)直接聚类分析进行综合分析。经电子计算机运算后,不仅取得了与传统分类基本一致的分类结果,同时也表明这种方法较之其它一些植物数量分类方法简便易行,此外还讨论了一些中国散生竹类分类上的问题。