Collective cell motion in endothelial monolayers

Collective cell motility is an important aspect of several developmental and pathophysiological processes. Despite its importance, the mechanisms that allow cells to be both motile and adhere to one another are poorly understood. In this study we establish statistical properties of the random streaming behavior of endothelial monolayer cultures. To understand the reported empirical findings, we expand the widely used cellular Potts model to include active cell motility. For spontaneous directed motility we assume a positive feedback between cell displacements and cell polarity. The resulting model is studied with computer simulations and is shown to exhibit behavior compatible with experimental findings. In particular, in monolayer cultures both the speed and persistence of cell motion decreases, transient cell chains move together as groups and velocity correlations extend over several cell diameters. As active cell motility is ubiquitous both in vitro and in vivo, our model is expected to be a generally applicable representation of cellular behavior.     

Accumulation and oxidative stress biomarkers in Japanese flounder larvae and juveniles under chronic cadmium exposure

This study investigated how Cd exposure affected oxidative biomarkers in Japanese flounder, Paralichthys olivaceus, at early life stages (ELS). Fish were exposed to waterborne Cd (0–48 µg L^− 1) from embryonic to juvenile stages for 80 days. Growth, Cd accumulation, activities of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), glutathione S-transferase (GST, EC 2.5.1.18), and levels of glutathione (GSH) and lipid peroxidation (LPO) were investigated at three developmental stages. Flounder growth decreased and Cd accumulation increased with increasing Cd concentration. In metamorphosing larvae, CAT and SOD activities were inhibited and GSH level was elevated, while LPO was enhanced by increasing Cd concentrations. CAT and GST activities of settling larvae were inhibited but GSH level was elevated at high Cd concentrations. In juveniles, SOD activity and LPO level were increased but GST activity was inhibited as Cd concentration increased. Antioxidants in flounder at ELS were able to develop ductile responses to defend against oxidative stress, but LPO fatally occurred due to Cd exposure. These biochemical parameters could be used as effective oxidative biomarkers for evaluating Cd contamination and toxicity in marine environments: CAT, SOD, GSH, and LPO for metamorphosing stage; CAT, GSH, and GST for settling stage; and SOD, GST, and LPO for juvenile stage.     

Chromatin unfolding by Cdt1 regulates MCM loading via opposing functions of HBO1 and HDAC11-geminin

The efficiency of metazoan origins of DNA replication is known to be enhanced by histone acetylation near origins. Although this correlates with increased MCM recruitment, the mechanism by which such acetylation regulates MCM loading is unknown. We show here that Cdt1 induces large-scale chromatin decondensation that is required for MCM recruitment. This process occurs in G₁, is suppressed by Geminin and requires HBO1 HAT activity and histone H4 modifications. HDAC11, which binds Cdt1 and replication origins during S phase, potently inhibits Cdt1-induced chromatin unfolding and re-replication, suppresses MCM loading and binds Cdt1 more efficiently in the presence of Geminin. We also demonstrate that chromatin at endogenous origins is more accessible in G₁ relative to S phase. These results provide evidence that histone acetylation promotes MCM loading via enhanced chromatin accessibility. This process is regulated positively by Cdt1 and HBO1 in G₁ and repressed by Geminin-HDAC11 association with Cdt1 in S phase and represents a novel form of replication licensing control.Key words: Cdt1, HBO1, HDAC11, chromatin, DNA replication     

HIV capsid is a tractable target for small molecule therapeutic intervention

Despite a high current standard of care in antiretroviral therapy for HIV, multidrug-resistant strains continue to emerge, underscoring the need for additional novel mechanism inhibitors that will offer expanded therapeutic options in the clinic. We report a new class of small molecule antiretroviral compounds that directly target HIV-1 capsid (CA) via a novel mechanism of action. The compounds exhibit potent antiviral activity against HIV-1 laboratory strains, clinical isolates, and HIV-2, and inhibit both early and late events in the viral replication cycle. We present mechanistic studies indicating that these early and late activities result from the compound affecting viral uncoating and assembly, respectively. We show that amino acid substitutions in the N-terminal domain of HIV-1 CA are sufficient to confer resistance to this class of compounds, identifying CA as the target in infected cells. A high-resolution co-crystal structure of the compound bound to HIV-1 CA reveals a novel binding pocket in the N-terminal domain of the protein. Our data demonstrate that broad-spectrum antiviral activity can be achieved by targeting this new binding site and reveal HIV CA as a tractable drug target for HIV therapy.     

Effects of Acacia (Acacia auriculaeformis A. Cunn)‐associated fungi on mustard (Brassica juncea (L.) Coss. var. foliosa Bailey) growth in Cd‐ and Ni‐contaminated soils

Aims: To evaluate the effect of Acacia auriculaeformis‐associated fungi on the growth of mustard [Brassica juncea (L.) Coss. var. foliosa Bailey] in Cd‐ and Ni‐contaminated soils and design novel plant–fungi associations for bioremediation purpose. Methods and Results: Endophytic Trichoderma H8 and rhizosphere Aspergillus G16 were applied for rhizoremediation of Cd‐, Ni‐, and Cd–Ni combination‐contaminated soils through association with B. juncea (L.) Coss. var. foliosa. Compared with the noninoculated control plants, inoculation with Trichoderma H8 produced 109%, 41% and 167% more fresh weight (FW) plant yields in the Cd‐, Ni‐, and Cd–Ni‐contaminated soils, respectively (P < 0·05). Similarly, plants inoculated with Aspergillus G16 produced 109%, 47% and 44% more FW plant yields in these contaminated soils, respectively. Plants co‐inoculated with these two strains produced 118%, 100% and 178% more FW plant yields, respectively. The inoculations also increased the translocation factors and metal bioconcentration factors. Conclusions: The efficiency of phytoextraction for B. juncea (L.) Coss. var. foliosa was enhanced after inoculating with Acacia‐associated fungi. Significance and Impact of the study: The use of plant–fungi association may be a promising strategy to remediate metal‐contaminated soils.     

Structural basis for the inhibition of tyrosine kinase activity of ZAP-70

ZAP-70, a cytoplasmic tyrosine kinase required for T cell antigen receptor signaling, is controlled by a regulatory segment that includes a tandem SH2 unit responsible for binding to immunoreceptor tyrosine-based activation motifs (ITAMs). The crystal structure of autoinhibited ZAP-70 reveals that the inactive kinase domain adopts a conformation similar to that of cyclin-dependent kinases and Src kinases. The autoinhibitory mechanism of ZAP-70 is, however, distinct and involves interactions between the regulatory segment and the hinge region of the kinase domain that reduce its flexibility. Two tyrosine residues in the SH2-kinase linker that activate ZAP-70 when phosphorylated are involved in aromatic-aromatic interactions that connect the linker to the kinase domain. These interactions are inconsistent with ITAM binding, suggesting that destabilization of this autoinhibited ZAP-70 conformation is the first step in kinase activation.     

General Information

A novel cDNA clone encoding a COR413-like gene was isolated by suppression subtraction hybridization and cDNA library screening from sea-island cotton (Gossypium barbadense). This gene (designated as GbCOR413, Accession number: AY761065) has a total length of 893 bp with an open reading frame of 600 bp, encoding a predicated polypeptide of 200 amino acids with a molecular weight of 22.74 kDa and a predicated pI of 9.2. Bioinformatics analyses revealed that this gene belonged to a novel stress-regulated multi-spanning transmembrane protein family without signal peptide. By means of semi-quantities RT-PCR analysis, the expression of GbCOR413 under short-term cold treatment at 4°C, water submergence and abscic acid treatment was investigated. Our studies suggested that the cloned gene was a new member of COR gene family which was slowly responsive to cold stress in cotton. Jin Wang and Kai-Jing Zuo are co-first authors of this paper.     

Development of a DNA microarray to identify the Streptococcus pneumoniae serotypes contained in the 23-valent pneumococcal polysaccharide vaccine and closely related serotypes

Streptococcus pneumoniae is a major worldwide human pathogen. This investigation has developed a reliable and accurate DNA microarray method for inter-species differentiation of S. pneumoniae and intra-species differentiation of the 23 groups of S. pneumoniae including serotypes represented in the 23-valent pneumococcal vaccine and the other 20 closely related serotypes. In addition to 16S rDNA probes, serotype- or serogroup-specific probes targeting the capsular polysaccharide synthesis (cps) genes, wzy or capA were generated. We adopted a two-step multiplex PCR to improve the sensitivity of detection to a level of 10(5) cfu/ml in pure culture or 50 ng DNA. A total of 169 isolates (from China, Australia, Canada and New Zealand) including 147 belonging to 23-valent vaccine and closely related serotypes of S. pneumoniae, 11 belonging to other serotypes and 11 of different species commonly isolated from respiratory tract were tested to verify the method. The DNA microarray method developed provides a sensitive means to rapidly identify the members of the most common S. pneumoniae serotypes in patients and to monitor their distribution in different patient groups and geographic locations. Such information is needed for disease surveillance and to monitor vaccine efficacy.     

Chromatin reorganization and endogenous auxin/cytokinin dynamic activity during somatic embryogenesis of cultured cotton cell

We conducted a systematic assessment and comparative study on the biochemical and cellular characteristics of cultured cotton cells during the entire process of somatic embryogenesis (SE). All staged cultures were widely investigated in this assay. Cell and tissue ectogenesis manipulation combined with flow cytometry (FCM) was employed to cellular study during the whole totipotency process of dedifferentiation and redifferentiation. We identified two phases of chromatin decondensation during the dedifferentiation and redifferentiation. At the same time, sharp increase in the ratio of indoleacetic acid (IAA), isopentenyladenosine group (iPAs) at the same stage of cell dedifferentiation and redifferentiation process serve as distinct biochemical maker of dedifferentiation and SE initiation with the unique feature. Our results suggest the two phases of chromatin reorganization associated with endogenous auxin/cytokinin dynamic activity may underlie dedifferentiation and redifferentiation during the entire SE process in cotton.     

Genotoxic effect and nitrative DNA damage in HepG2 cells exposed to aristolochic acid

Aristolochic acid (AA), extensively used as a traditional herbal medicine, was withdrawn from the market in the last century because it was found to be a potent carcinogen in humans and animals. The aim of this study was to evaluate the genotoxic effect of AA and obtain further insight into whether the nitrative DNA damage can be induced by reactive nitrogen species (RNS), including nitric oxide (NO) and its derivative peroxynitrite (ONOO(-)) using human hepatoma HepG2 cells. To identify the genotoxic effect, the comet assay and micronucleus test (MNT) were performed. In the comet assay, 25-200microM of AA caused a significant increase of DNA migration in a dose-dependent manner. A significant increase of the frequency of micronuclei was found in the range between 12.5 and 50microM in the MNT. The results showed that AA caused DNA and chromosome damages. To elucidate the nitrative DNA damage mechanism, the level of nitrite and 8-hydroxydeoxyguanosine (8-OHdG), which can be generated by ONOO(-), were monitored with the 2,3-diaminonaphthalene (DAN) assay and immunoperoxidase staining, respectively. The results showed that AA causes a significant increase in the levels of NO and formation of 8-OHdG at concentrations >/=50microM. This observation supports the assumption that AA could exert genotoxicity probably via NO and its derivatives at higher concentrations in HepG2 cells.