Antiviral properties of milk proteins and peptides

A substantial body of evidence, primarily from in vitro studies, suggests that some milk proteins interfere with viral infections. Lactoferrin (LF) has been the protein most comprehensively studied for its antiviral effects. Interference with viral infections is primarily based on adsorption of LF to receptors on the host cell's surface or on binding to viral particles, both enveloped and non-enveloped. In either mechanism, viral particles are prevented from attaching to host cells. Electrostatic attraction seems to play an important role in both mechanisms. In general, bovine LF is more effective against viral infections than human LF. Apo-LF is less effective than the iron-saturated LF. Antiviral effects of lactoferricin and other peptides liberated from LF are weaker than those of intact LF. Proteins other than LF, such as lactadherin, and peptides such as glycomacropeptide, also interfere with infection by some viruses. Chemical modifications of milk proteins that lead to changes in charges on proteins, and in charge distribution, enhance their effects against certain viruses.     

应用Illumina Miseq测序分析饮用水源水中病毒多样性

以东太湖水源水为研究对象,应用梯度-串联-循环-切向流超滤技术对水体中病毒进行分离浓缩,使用非序列依赖性单引物扩增技术扩增源水中病毒基因组,采用Illumina Miseq进行测序,与NCBI基因数据库进行比对,质控后获得1?190?914?928?bp基因数据,可组装成5?554?条scaffolds序列,获知病毒基因组功能,经比对可注释到尾噬菌体目（Caudovirales）、疱疹病毒目（Herpesvirales）、线状病毒目（Ligamenvirales）,在科的水平上,注释到40?个科病毒的同源序列,其中含量较高的病毒科为Microviridae占27.590?1%,Siphoviridae占23.010?7%,Phycodnaviridae占5.322?2%,Retroviridae占1.691?2%,Mimiviridae占1.960?8%,其中无法注释（norank）占21.572?8%,102?112?条reads在科水平上norank,研究可以高通量的获得水源水中病毒多样性信息,并为水体中病毒的检测提供理论参考依据。     

Genome mapping and gene analysis of Antheraea pernyi nucleopolyhedrovirus for improvement of baculovirus expression vector system

We have constructed a genome DNA map of the Antheraea pernyi nucleopolyhedrovirus (AnpeNPV) and used it to identify target genes for deletion in order to improve the newly developed baculovirus expression vector system. Initially, 50 independent PstI fragments of viral DNA were obtained by shotgun cloning, and both termini of each cloned fragment were sequenced. Then, the sequence data were used for homology search against both nucleotide and amino acid sequences of other NPVs in databases. This homology search allowed us to construct a nearly complete restriction map of a viral DNA with several assumed gaps. Four additional PstI fragments covering the gaps were obtained by PCR amplification, and a complete map of a circular viral DNA, which consisted of 54 PstI fragments, was constructed. The map indicated that the AnpeNPV genome is approximately 130.2 kbp in size and possesses high similarity to the Orgyia pseudotsugata multicapsid NPV (OpMNPV) genome in both sequence and arrangement of genes. Utilizing the genome-wide high similarity between AnpeNPV and OpMNPV, we identified two target genes on the map, namely, cathepsin and chitinase genes, whose products have been proved to be involved in the degradation of recombinant proteins and the liquefaction of virus-infected insect tissues. Comparative sequence analysis of the map also revealed the lack of certain OpMNPV open reading frame (ORF) homologs and the presence of ORFs, whose homologs do not exist in OpMNPV but in other group I NPVs, providing an insight into the position of AnpeNPV in the baculovirus phylogeny.     

Ribosomal frameshifting in yeast viruses

Proper maintenance of translational reading frame by ribosomes is essential for cell growth and viability. In the last 10 years it has been shown that a number of viruses induce ribosomes to shift reading frame in order to regulate the expression of gene products having enzymatic functions. Studies on ribosomal frameshifting in viruses of yeast have been particularly enlightening. The roles of viral mRNA sequences and secondary structures have been elucidated and a picture of how these interact with host chromosomal gene products is beginning to emerge. The efficiency of ribosomal frameshifting is important for viral particle assembly, and has identified ribosomal frameshifting as a potential target for antiviral agents. The availability of mutants of host chromosomal gene products involved in maintaining the efficiency of ribosomal frameshifting bodes well for the use of yeast in future studies of ribosomal frameshifting.     

蜂胶提取物对诺如病毒的体外抑制作用研究

为研究蜂胶提取物对人源诺如病毒的体外抑制作用,采用小鼠诺如病毒和噬菌体MS2病毒为替代病毒,研究蜂胶水提物和醇提物随浓度及时间变化对小鼠诺如病毒和噬菌体MS2病毒的抑制作用及其机制.浓度相关性实验表明:随着蜂胶醇提物浓度增加,小鼠诺如病毒和MS2病毒滴度呈显著下降趋势,当醇提物质量浓度达到500μg/mL时,小鼠诺如病...     

The frenemies within: viruses,retrotransposons and plasmids that naturally infect Saccharomyces yeasts

Viruses are a major focus of current research efforts because of their detrimental impact on humanity and their ubiquity within the environment. Bacteriophages have long been used to study host–virus interactions within microbes, but it is often forgotten that the single‐celled eukaryote Saccharomyces cerevisiae and related species are infected with double‐stranded RNA viruses, single‐stranded RNA viruses, LTR‐retrotransposons and double‐stranded DNA plasmids. These intracellular nucleic acid elements have some similarities to higher eukaryotic viruses, i.e. yeast retrotransposons have an analogous lifecycle to retroviruses, the particle structure of yeast totiviruses resembles the capsid of reoviruses and segregation of yeast plasmids is analogous to segregation strategies used by viral episomes. The powerful experimental tools available to study the genetics, cell biology and evolution of S. cerevisiae are well suited to further our understanding of how cellular processes are hijacked by eukaryotic viruses, retrotransposons and plasmids. This article has been written to briefly introduce viruses, retrotransposons and plasmids that infect Saccharomyces yeasts, emphasize some important cellular proteins and machineries with which they interact, and suggest the evolutionary consequences of these interactions. Copyright © 2017 John Wiley & Sons, Ltd.     

Adhesion of Lactobacilli and their anti-infectivity potential

The probiotic potential of lactic acid bacteria primarily point toward colonizing ability of Lactobacilli as the most important attribute for endowing all the known beneficial effects in a host. Lactobacillus species exert health-promoting function in the gastrointestinal tract through various mechanisms such as pathogen exclusion, maintenance of microbial balance, immunomodulation, and other crucial functions. It has been seen that many surface layer proteins are involved in host adhesion, and play significant role in the modification of some signaling pathways within the host cells. Interaction between different bacterial cell surface proteins and host receptor has been imperative for a better understanding of the mechanism through which Lactobacilli exert their health-promoting functions.     

A tomato stem cell extract, containing antioxidant compounds and metal chelating factors, protects skin cells from heavy metal-induced damages

Heavy metals can cause several genotoxic effects on cells, including oxidative stress, DNA sequence breakage and protein modification. Among the body organs, skin is certainly the most exposed to heavy metal stress and thus the most damaged by the toxic effects that these chemicals cause. Moreover, heavy metals, in particular nickel, can induce the over-expression of collagenases (enzymes responsible for collagen degradation), leading to weakening of the skin extracellular matrix. Plants have evolved sophisticated mechanisms to protect their cells from heavy metal toxicity, including the synthesis of metal chelating proteins and peptides, such as metallothioneins and phytochelatins (PC), which capture the metals and prevent the damages on the cellular structures. To protect human skin cells from heavy metal toxicity, we developed a new cosmetic active ingredient from Lycopersicon esculentum (tomato) cultured stem cells. This product, besides its high content of antioxidant compounds, contained PC, effective in the protection of skin cells towards heavy metal toxicity. We have demonstrated that this new product preserves nuclear DNA integrity from heavy metal damages, by inducing genes responsible for DNA repair and protection, and neutralizes the effect of heavy metals on collagen degradation, by inhibiting collagenase expression and inducing the synthesis of new collagen.     

Inactivation of food-borne viruses using natural biochemical substances

Food-borne viruses such as human Noroviruses (NoVs), hepatitis A virus (HAV), Rotaviruses (RoVs) are a public health concern worldwide. Biochemical substances, which occur naturally in plants, animals or microorganisms, might possess considerable antimicrobial properties. In this study, the reported effects of biochemical substances on food-borne viruses are reviewed. The biochemical substances are grouped into several categories including (i) polyphenols and proanthocyanins, (ii) saponin, (iii) polysaccharides, (iv) organic acids, (v) proteins and polypeptides, (vi) essential oils. Although not fully understood, the mechanism of action for the antiviral activity of the natural compounds is presented. Generally, it is thought to be the prevention of the viral attachment to host cells, either by causing damage on the viral capsids or change of the receptors on the cell membranes. It is recommended that further studies are undertaken not only on the wide-range screening for novel antiviral substances, but also on the mechanism in-depth as well as the exploration for their potential application in controlling virus contamination in foods or food processing.     

The dual origin of the yeast mitochondrial proteome

We propose a scheme for the origin of mitochondria based on phylogenetic reconstructions with more than 400 yeast nuclear genes that encode mitochondrial proteins. Half of the yeast mitochondrial proteins have no discernable bacterial homologues, while one-tenth are unequivocally of alpha-proteobacterial origin. These data suggest that the majority of genes encoding yeast mitochondrial proteins are descendants of two different genomic lineages that have evolved in different modes. First, the ancestral free-living alpha-proteobacterium evolved into an endosymbiont of an anaerobic host. Most of the ancestral bacterial genes were lost, but a small fraction of genes supporting bioenergetic and translational processes were retained and eventually transferred to what became the host nuclear genome. In a second, parallel mode, a larger number of novel mitochondrial genes were recruited from the nuclear genome to complement the remaining genes from the bacterial ancestor. These eukaryotic genes, which are primarily involved in transport and regulatory functions, transformed the endosymbiont into an ATP-exporting organelle.     

PHYTOCYSTATINS AND THEIR TARGET ENZYMES: FROM MOLECULAR BIOLOGY TO PRACTICAL APPLICATION: A REVIEW

Cystatins are protein inhibitors of cysteine proteinases. Oryzacystatin I (OC-I) has been cloned and is apparently the first well-defined cystatin of plant origin (phytocystatin). Besides OC-I, various other phytocystatins occur in rice, corn, wheat and soybean. Phytocystatins have endogenous target enzymes whose expression is induced by gibberellin, and also exogenous target enzymes from viruses and insects. It is thus likely that phytocystatins are involved in the regulation of intracellular protein catabolism as well as in the defense from infection. Better understanding of this phenomenon and cloning of appropriate genes will facilitate the creation of transgenic crops with enhanced resistance to viruses and insects.     

Accumulative gene integration into a pre-determined site using Cre/loxP

Site-specific gene recombination systems, such as Cre/loxP, have been used for genetic modification of cells and organisms in both basic and applied research. We previously developed an accumulative gene integration system (AGIS), in which target gene cassettes could be repeatedly integrated into a pre-determined site on a plasmid or cellular genome by recombinase-mediated cassette exchange (RMCE), using Cre and mutated loxPs. In the present study, we designed a simplified AGIS. For gene integration into a target site, the previous system used two loxP sites in the acceptor DNA, whereas the new system uses a single loxP site. The gene integration reactions were repeated four times in vitro using Cre protein and specific plasmids. The expected integration reactions mediated by Cre occurred at the loxP sites, resulting in integration of four target genes. The system was also used for genomic integration of reporter genes using Chinese hamster ovary (CHO) cells. The reporter genes were efficiently introduced into the CHO genome in a Cre-dependent manner, and transgene expression was detected after the integration reaction. The expression levels of the reporter genes were enhanced, corresponding to the increase of transgene copy number. Recombinase-mediated AGIS provides a useful tool for the modification of cellular genomes.     

Cloning,Sequencing and Expression of a Full-Length cDNA Copy of the M1 Double-Stranded RNA Virus from the Yeast,Saccharomyces cerevisiae

Strains of the budding yeast, Saccharomyces cerevisiae, may contain one or more cytoplasmic viruses with double-stranded RNA (dsRNA) genomes. The killer phenomenon in yeast, in which one cell secretes a killer toxin that is lethal to another cell, is dependent upon the presence of the L-A and M1 dsRNA viruses. The L-A viral genome encodes proteins for the viral capsid, and for synthesis and encapsidation of single-stranded RNA replication cycle intermediates. The M1 virus depends upon the L-A-encoded proteins for its capsid and for the replication of its killer-toxin-encoding genome. A full-length cDNA clone of an M1 genome has been made from a single dsRNA molecule and shown to encode functional killer and killer-immunity functions. The sequence of the clone indicates minor differences from previously published sequences of parts of the M1 genome and of the complete genome of S14 (an internal deletion derivative of M1) but no unreported amino acid variants and no changes in putative secondary structures of the single-stranded RNA. A 118-nucleotide contiguous segment of the M1 genome has not previously been reported; 92 of those nucleotides comprise a segment of A nucleotides in the AU-rich bubble that follows the toxin-encoding reading frame. The GenBank Accession Number for the sequence is U78817; the locus is SCU78817. © 1997 John Wiley & Sons, Ltd.     

Excision of selectable marker genes from transgenic crops as a concern for environmental biosafety

The main task in the development of transgenic plants is the capability to distinguish between plant cells with an integrated transgene and the bulk of non‐transformed cells. Selectable marker genes are required to achieve this goal within the transgene, and to select for their expression. These selectable markers are mostly based on genes conferring antibiotic or herbicide resistance. The presence of the marker gene will lead to unpredictable environmental hazards, so on the basis of economic incentives and safety concerns, several methods, such as site‐specific recombination, homologous recombination and co‐transformation, have been developed to eliminate these genes from the genome after successful transformation has been achieved. Gene transfer without the incorporation of an antibiotic‐resistance marker or herbicide‐resistance marker in the host genome should convince the public with regard to the field release of transgenic organisms. Moreover, it would obviate the need for different selectable markers in subsequent rounds of gene transfer into the same host. Copyright © 2007 Society of Chemical Industry