AUF1在病毒感染及相关炎症反应中的调控作用

富含AU元件的RNA结合蛋白1(AU-rich element binding factor 1,AUF1)具有剪接加工前体mRNA、转运和降解成熟mRNA的功能,同时调节带有富含AU元件(AU-rich element,ARE)的mRNA翻新。AUF1通过介导炎性细胞因子及其反应从而控制炎症进程。研究表明,AUF1与肠道病毒71型的内部核糖体进入位点(internal ribosome entry site,IRES)结合并与其交互负性调节病毒翻译与复制,它还可被募集到柯萨奇病毒B3型和肠道病毒71型诱导的应激颗粒中。     

Enhancement of metal bioremediation by use of microbial surfactants

Metal pollution all around the globe, especially in the mining and plating areas of the world, has been found to have grave consequences. An excellent option for enhanced metal contaminated site bioremediation is the use of microbial products viz. microbial surfactants and extracellular polymers which would increase the efficiency of metal reducing/sequestering organisms for field bioremediation. Important here is the advantage of such compounds at metal and organic compound co-contaminated site since microorganisms have long been found to produce surface-active compounds when grown on hydrocarbons. Other options capable of proving efficient enhancers include exploiting the chemotactic potential and biofilm forming ability of the relevant microorganisms. Chemotaxis towards environmental pollutants has excellent potential to enhance the biodegradation of many contaminants and biofilm offers them a better survival niche even in the presence of high levels of toxic compounds.     

DAZAP1 interacts via its RNA-recognition motifs with the C-termini of other RNA-binding proteins

The turnover and translation of many human mRNAs is regulated by AU-rich elements present in their 3′untranslated region, which bind various trans acting factors. We previously identified a trans acting factor that interacts with these cis elements as DAZAP1 (deleted in Azoospermia (DAZ)-Associated Protein 1), whose interaction with the germ cell-specific protein DAZ was disrupted by the phosphorylation of DAZAP1. Here we have identified several other RNA-binding proteins as binding partners for DAZAP1 in non-germinal cells. Unlike DAZ, these interactions occur between the RNA recognition motifs of DAZAP1 and the C-termini of the binding partners and in a phosphorylation-independent manner. The results suggest that DAZAP1 is a component of complexes that are crucial for the degradation and silencing of mRNA.     

免疫系统在病毒性心肌炎发病中的作用

心肌炎通常由病毒感染引起,有证据表明心肌炎最终发展成扩张性心肌病,是发达国家主要致死的原因,越来越多的人认为细胞因子在心肌炎和心肌病发病中起重要作用,心力衰竭病人血循环中细胞因子水平较正常人高。已证明多种细胞因子能在体内外抑制心肌收缩,细胞因子由活化的免疫细胞产生,它可诱生NO合酶,继而产生NO,已证明NO既有利又有害,关键在于产生NO量的多少,NO能抑制病毒复制,而保护心脏抗柯萨奇B病毒感染,无论是病毒感染对心脏的直接作用,还是免疫应答的利弊平衡,对此两者分子机制的了解都将是掌握人类心肌炎发病的关键。     

Chenodeoxycholic acid stabilization of LDL receptor mRNA depends on 3'-untranslated region and AU-rich element-binding protein

Human low-density lipoprotein receptor (LDLR) mRNA is unstable and contains four AU-rich elements (AREs) in the 3′-untranslated region (3′-UTR). The aim of this study was to verify the involvement of the 3′-UTR in the rapid degradation of LDLR mRNA. This study revealed that the 3′-UTR is necessary and sufficient for the degradation, and that the 1st ARE (ARE1) close to the stop codon associates with cytoplasmic proteins, and is primarily responsible for the degradation. Chenodeoxycholic acid (CDCA) treatment stabilized chimeric GFP-LDLR 3′-UTR mRNA and accompanied mitogen-activated protein kinase (MAPK) activation. The UV cross-linking assays showed that a protein of 80 kDa increasingly binds to the region including the ARE1 in response to CDCA-mediated MAPK activation.     

Mitochondrial localization of viral proteins as a means to subvert host defense

Viruses have developed a battery of distinct strategies to overcome the very sophisticated defense mechanisms of the infected host. Throughout the process of pathogen-host co-evolution, viruses have therefore acquired the capability to prevent host cell apoptosis because elimination of infected cells via apoptosis is one of the most ancestral defense mechanism against infection. Conversely, induction of apoptosis may favor viral dissemination as a result of the dismantlement of the infected cells. Mitochondria have been long recognized for their key role in the modulation of apoptosis but more recently, mitochondria have been shown to serve as a crucial platform for innate immune signaling as illustrated by the identification of MAVS. Thus, it is therefore not surprising that this organelle represents a recurrent target for viruses, aiming to manipulate the fate of the infected host cell or to inhibit innate immune response. In this review, we highlight the viral proteins that are specifically targeted to the mitochondria to subvert host defense. This article is part of a Special Issue entitled Mitochondria: the deadly organelle.     

Generation of a recombinant reporter hepatitis C virus useful for the analyses of virus entry, intra-cellular replication and virion production

The lack of a culture system that efficiently produces progeny virus has hampered hepatitis C virus (HCV) research. Recently, the discovery of a novel HCV isolate JFH1 and its chimeric derivative J6/JFH1 has led to the development of an efficient virus productive culture system. To construct an easy monitoring system for the viral life cycle of HCV, we generated bicistronic luciferase reporter virus genomes based on the JFH1 and J6/JFH1 isolates, respectively. Transfection of the J6/JFH1-based reporter genome to Huh7.5 cells produced significantly greater levels of progeny virus than transfection of the JFH1 genome. Furthermore, the expression of dominant-negative Vps4, a key molecule of the endosomal sorting complex required for transport machinery, inhibited the virus production of JFH1, but not that of J6/JFH1. These results may account for the different abilities to produce progeny virus between JFH1 and J6/JFH1. Using the J6/JFH1/Luc system, we showed that the two polyanions heparin and polyvinyl sulfate decreased the infectivity of J6/JFH1/Luc virus in a dose-dependent manner. We also analyzed the function of microRNA on HCV replication and found that miR-34b could affect the replication of HCV. The reporter virus generated in this study will be useful for investigating the nature of the HCV life cycle and for identification of HCV inhibitors.     

Production of a reporter transgenic pig for monitoring Cre recombinase activity

The pig is thought to be the most suitable non-human source of organs for xenotransplantation and is widely used as a model of human disease. Using pigs as disease models requires the design of conditional Cre recombinase-loxP gene modifications, which, in turn, requires a Cre-expressing pig with defined patterns of expression controlled by the use of a tissue-specific promoter. In order to monitor Cre recombinant expression in vivo, it is important to create a reporter strain. We have generated reporter a pig that is based on a single vector that drives the ubiquitous expression of the enhanced green fluorescent protein (EGFP). The EGFP gene is expressed only after Cre-mediated excision of loxP-flanked stop sequences. These reporter transgenic pigs will be of great value for monitoring Cre recombinase activity in vivo.     

病毒持续性感染难治愈的因素及对策

病毒持续性感染引起的病程多为慢性或反复发作,难以治愈,在部分患者甚至可引发肿瘤或自身免疫性疾病等,是严重危害人类健康及造成社会重大经济负担的常见病及多发病。持续性感染难以治愈的原因涉及病毒基因组与宿主细胞染色体整合,或以附加体的形式长期存在,以及病毒的酶或蛋白抑制机体的免疫应答等特性。此外,机体天然免疫或获得性免疫低下、免疫网络失调及感染微环境改变等,也是病毒建立并维持持续性感染的原因。本文根据持续性感染难以治愈的原因,从病原学与机体免疫应答两方面研讨一些对策,希望以此为切入点,为治疗持续性感染提供新思路与新策略。     

Affinity purification of ARE-binding proteins identifies polyA-binding protein 1 as a potential substrate in MK2-induced mRNA stabilization

An important determinant for the expression level of cytokines and proto-oncogenes is the rate of degradation of their mRNAs. AU-rich sequence elements (AREs) in the 3(') untranslated regions have been found to impose rapid decay of these mRNAs. ARE-containing mRNAs can be stabilized in response to external signals which activate the p38 MAP kinase cascade including the p38 MAP kinase substrate MAPKAP kinase 2 (MK2). In an attempt to identify components downstream of MK2 in this pathway we analyzed several proteins which selectively interact with the ARE of GM-CSF mRNA. One of them, the cytoplasmic poly(A)-binding protein PABP1, co-migrated with a protein that showed prominent phosphorylation by recombinant MK2. Phosphorylation by MK2 was confirmed using PABP1 purified by affinity chromatography on poly(A) RNA. The selective interaction with an ARE-containing RNA and the phosphorylation by MK2 suggest that PABP1 plays a regulatory role in ARE-dependent mRNA decay and its modulation by the p38 MAP kinase cascade.     

Probability of resistance evolution for exponentially growing virus in the host

Chemotherapy for tumor and pathogenic virus often faces an emergence of resistant mutants, which may lead to medication failure. Here we study the risk of resistance to evolve in a virus population which grows exponentially. We assume that infected cells experience a "proliferation event" of virus at a random time and that the number of newly infected cells from an infected cell follows a Poisson distribution. Virus starts from a single infected cell and the virus infection is detected when the number of infected cells reaches a detection size. Initially virus is sensitive to a drug but later acquires resistance by mutations. We ask the probability that one or more cells infected with drug-resistant virus exist at the time of detection. We derive a formula for the probability of resistance and confirm its accuracy by direct computer simulations. The probability of resistance increases with detection size and mutation rate but decreases with the population growth rate of sensitive virus. The risk of resistance is smaller when more cells are newly infected by viral particles from a single infected cell if the viral growth rate is the same.     

The structural basis of recognition and removal of cellular mRNA 7-methyl G 'caps' by a viral capsid protein: a unique viral response to host defense

The single segment, double-stranded RNA genome of the L-A virus (L-A) of yeast encodes two proteins: the major coat protein Gag (76 kDa) and the Gag-Pol fusion protein (180 kDa). The icosahedral L-A capsid is formed by 120 copies of Gag and has architecture similar to that seen in the reovirus, blue tongue virus and rice dwarf virus inner protein shells. Gag chemically removes the m7GMP caps from host cellular mRNAs. Previously we identified a trench on the outer surface of Gag that included His154, to which caps are covalently attached. Here we report the refined L-A coordinates at 3.4 angstroms resolution with additional structural features and the structure of L-A with bound m7GDP at 6.5 angstroms resolution, which shows the conformational change of the virus upon ligand binding. Based on site-directed mutations, residues in or adjacent to the trench that are essential (or dispensable) for the decapping reaction are described here. Along with His154, the reaction requires a cluster of positive charge adjoining the trench and residues Tyr 452, Tyr150 and either Tyr or Phe at position 538. A tentative mechanism for decapping is proposed.     

Genetic diversity and models of viral evolution for the hepatitis C virus

In this review we discuss the application of theoretical frameworks to the interpretation of viral gene sequence data, with particular reference to the hepatitis C virus (HCV). The increasing availability of such data means that it is now possible (and necessary) to proceed from simple qualitative models of viral evolution, to more quantitative frameworks based on statistical inference, notably population genetics and molecular phylogenetics. We argue that these approaches are invaluable tools to the virologist and are essential for understanding the dynamics of viral infection and the outcome of therapeutic strategies. We use several recent HCV data-sets to illustrate the methods.     

HPLC法测定病毒性疫苗中EDTA二钠残余量

实验中用高效液相色谱法测定病毒性疫苗中乙二胺四乙酸二钠残余量。EDTA二钠与FeCl3反应生成的络合物NaFeEDTA在257nm波长处有明显吸收,以C18柱将它与其余组分分开后,用外标法建立五级校正曲线可测定制品中EDTA-2Na含量。该方法准确,快速,可用于检测病毒性疫苗中残余乙二胺四乙酸二钠。