Histone Chaperone NAP1 Mediates Sister Chromatid Resolution by Counteracting Protein Phosphatase 2A

Chromosome duplication and transmission into daughter cells requires the precisely orchestrated binding and release of cohesin. We found that the Drosophila histone chaperone NAP1 is required for cohesin release and sister chromatid resolution during mitosis. Genome-wide surveys revealed that NAP1 and cohesin co-localize at multiple genomic loci. Proteomic and biochemical analysis established that NAP1 associates with the full cohesin complex, but it also forms a separate complex with the cohesin subunit stromalin (SA). NAP1 binding to cohesin is cell-cycle regulated and increases during G2/M phase. This causes the dissociation of protein phosphatase 2A (PP2A) from cohesin, increased phosphorylation of SA and cohesin removal in early mitosis. PP2A depletion led to a loss of centromeric cohesion. The distinct mitotic phenotypes caused by the loss of either PP2A or NAP1, were both rescued by their concomitant depletion. We conclude that the balanced antagonism between NAP1 and PP2A controls cohesin dissociation during mitosis.     

Whole-Exome Sequencing Identifies Mutated C12orf57 in Recessive Corpus Callosum Hypoplasia

The corpus callosum is the principal cerebral commissure connecting the right and left hemispheres. The development of the corpus callosum is under tight genetic control, as demonstrated by abnormalities in its development in more than 1,000 genetic syndromes. We recruited more than 25 families in which members affected with corpus callosum hypoplasia (CCH) lacked syndromic features and had consanguineous parents, suggesting recessive causes. Exome sequence analysis identified C12orf57 mutations at the initiator methionine codon in four different families. C12orf57 is ubiquitously expressed and encodes a poorly annotated 126 amino acid protein of unknown function. This protein is without significant paralogs but has been tightly conserved across evolution. Our data suggest that this conserved gene is required for development of the human corpus callosum.     

Modeling Social Transmission Dynamics of Unhealthy Behaviors for Evaluating Prevention and Treatment Interventions on Childhood Obesity

Research evidence indicates that obesity has spread through social networks, but lever points for interventions based on overlapping networks are not well studied. The objective of our research was to construct and parameterize a system dynamics model of the social transmission of behaviors through adult and youth influence in order to explore hypotheses and identify plausible lever points for future childhood obesity intervention research. Our objectives were: (1) to assess the sensitivity of childhood overweight and obesity prevalence to peer and adult social transmission rates, and (2) to test the effect of combinations of prevention and treatment interventions on the prevalence of childhood overweight and obesity. To address the first objective, we conducted two-way sensitivity analyses of adult-to-child and child-to-child social transmission in relation to childhood overweight and obesity prevalence. For the second objective, alternative combinations of prevention and treatment interventions were tested by varying model parameters of social transmission and weight loss behavior rates. Our results indicated child overweight and obesity prevalence might be slightly more sensitive to the same relative change in the adult-to-child compared to the child-to-child social transmission rate. In our simulations, alternatives with treatment alone, compared to prevention alone, reduced the prevalence of childhood overweight and obesity more after 10 years (1.2–1.8% and 0.2–1.0% greater reduction when targeted at children and adults respectively). Also, as the impact of adult interventions on children was increased, the rank of six alternatives that included adults became better (i.e., resulting in lower 10 year childhood overweight and obesity prevalence) than alternatives that only involved children. The findings imply that social transmission dynamics should be considered when designing both prevention and treatment intervention approaches. Finally, targeting adults may be more efficient, and research should strengthen and expand adult-focused interventions that have a high residual impact on children.     

Resveratrol protects against 4-HNE induced oxidative stress and apoptosis in Swiss 3T3 fibroblasts

Here we report on the marked protective effect of resveratrol on 4-hydroxynonenal (4-HNE) induced oxidative stress and apoptotic death in Swiss 3T3 fibroblasts. 4-HNE, one of the major aldehydic products of the peroxidation of membrane w-6 polyunsaturated fatty acids, has been suggested to contribute to oxidant stress mediated cell injury. Indeed, in vitro treatment of 3T3 fibroblasts with 4-HNE induced a condition of oxidative stress as monitored by the oxidation of dichlorofluorescein diacetate; this reaction was prevented when cells were pretreated with resveratrol. Further, 4-HNE-treated fibroblasts eventually underwent apoptotic death as determined by differential staining and internucleosomal DNA fragmentation. Resveratrol pretreatment also prevented 4-HNE induced DNA fragmentation and apoptosis. These observations are consistent with a potential role of lipid peroxidation-derived products in programmed cell death and demonstrate that resveratrol can counteract this effect by quenching cell oxidative stress.     

Improved thermostability of Clostridium thermocellum endoglucanase Cel8A by using consensus-guided mutagenesis

The use of thermostable cellulases is advantageous for the breakdown of lignocellulosic biomass toward the commercial production of biofuels. Previously, we have demonstrated the engineering of an enhanced thermostable family 8 cellulosomal endoglucanase (EC 3.2.1.4), Cel8A, from Clostridium thermocellum, using random error-prone PCR and a combination of three beneficial mutations, dominated by an intriguing serine-to-glycine substitution (M. Anbar, R. Lamed, E. A. Bayer, ChemCatChem 2:997-1003, 2010). In the present study, we used a bioinformatics-based approach involving sequence alignment of homologous family 8 glycoside hydrolases to create a library of consensus mutations in which residues of the catalytic module are replaced at specific positions with the most prevalent amino acids in the family. One of the mutants (G283P) displayed a higher thermal stability than the wild-type enzyme. Introducing this mutation into the previously engineered Cel8A triple mutant resulted in an optimized enzyme, increasing the half-life of activity by 14-fold at 85°C. Remarkably, no loss of catalytic activity was observed compared to that of the wild-type endoglucanase. The structural changes were simulated by molecular dynamics analysis, and specific regions were identified that contributed to the observed thermostability. Intriguingly, most of the proteins used for sequence alignment in determining the consensus residues were derived from mesophilic bacteria, with optimal temperatures well below that of C. thermocellum Cel8A.     

A Primer to Molecular Phylogenetic Analysis in Plants

Reconstructing a tree of life by inferring evolutionary history is an important focus of evolutionary biology. Phylogenetic reconstructions also provide useful information for a range of scientific disciplines such as botany, zoology, phylogeography, archaeology and biological anthropology. Until the development of protein and DNA sequencing techniques in the 1960s and 1970s, phylogenetic reconstructions were based on fossil records and comparative morphological/physiological analyses. Since then, progress in molecular phylogenetics has compensated for some of the shortcomings of phenotype-based comparisons. Comparisons at the molecular level increase the accuracy of phylogenetic inference because there is no environmental influence on DNA/peptide sequences and evaluation of sequence similarity is not subjective. While the number of morphological/physiological characters that are sufficiently conserved for phylogenetic inference is limited, molecular data provide a large number of datapoints and enable comparisons from diverse taxa. Over the last 20 years, developments in molecular phylogenetics have greatly contributed to our understanding of plant evolutionary relationships. Regions in the plant nuclear and organellar genomes that are optimal for phylogenetic inference have been determined and recent advances in DNA sequencing techniques have enabled comparisons at the whole genome level. Sequences from the nuclear and organellar genomes of thousands of plant species are readily available in public databases, enabling researchers without access to molecular biology tools to investigate phylogenetic relationships by sequence comparisons using the appropriate nucleotide substitution models and tree building algorithms. In the present review, the statistical models and algorithms used to reconstruct phylogenetic trees are introduced and advances in the exploration and utilization of plant genomes for molecular phylogenetic analyses are discussed.     

Protective role of zinc in liver damage in experimental diabetes demonstrated via different biochemical parameters

Diabetes mellitus is a serious worldwide metabolic disease, which is accompanied by hyperglycaemia and affects all organs and body system. Zinc (Zn) is a basic cofactor for many enzymes, which also plays an important role in stabilising the structure of insulin. Liver is the most important target organ after pancreas in diabetic complications. In this study, we aimed to investigate the protective role of Zn in liver damage in streptozotocin (STZ)‐induced diabetes mellitus. There are four experimental groups of female Swiss albino rats: group I: control; group II: control + ZnSO₄; group III: STZ‐induced diabetic animals and group IV: STZ‐diabetic + ZnSO₄. To induce diabetes, STZ was injected intraperitoneally (65 mg/kg). ZnSO₄ (100 mg/kg) was given daily to groups II and IV by gavage for 60 days. At the end of the experiment, rats were killed under anaesthesia and liver tissues were collected. In the diabetic group, hexose, hexosamine, fucose, sialic acid levels, arginase, adenosine deaminase, tissue factor activities and protein carbonyl levels increased, whereas catalase, superoxide dismutase, glutathione‐S‐transferase, glutathione peroxidase, glutathione reductase and Na⁺/K⁺‐ATPase activities decreased. The administration of Zn to the diabetic group reversed all the negative effects/activities. According to these results, we can suggest that Zn has a protective role against STZ‐induced diabetic liver damage.     

Uncovering hidden genetic variation in photosynthesis of field‐grown maize under ozone pollution

Ozone is the most damaging air pollutant to crops, currently reducing Midwest US maize production by up to 10%, yet there has been very little effort to adapt germplasm for ozone tolerance. Ozone enters plants through stomata, reacts to form reactive oxygen species in the apoplast and ultimately decreases photosynthetic C gain. In this study, 10 diverse inbred parents were crossed in a half‐diallel design to create 45 F₁ hybrids, which were tested for ozone response in the field using free air concentration enrichment (FACE). Ozone stress increased the heritability of photosynthetic traits and altered genetic correlations among traits. Hybrids from parents Hp301 and NC338 showed greater sensitivity to ozone stress, and disrupted relationships among photosynthetic traits. The physiological responses underlying sensitivity to ozone differed in hybrids from the two parents, suggesting multiple mechanisms of response to oxidative stress. FACE technology was essential to this evaluation because genetic variation in photosynthesis under elevated ozone was not predictable based on performance at ambient ozone. These findings suggest that selection under elevated ozone is needed to identify deleterious alleles in the world's largest commodity crop.     

In vitro antimicrobial activity of propolis samples from different geographical origins against certain oral pathogens

Propolis is an agent having antimicrobial properties, however, its composition can vary depending on the area where it is collected. In the present study, the antimicrobial activity of five propolis samples, collected from four different regions in Turkey and from Brazil, against nine anaerobic strains was evaluated. Ethanol extracts of propolis (EEP) were prepared from propolis samples and we determined minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of EEP on the growth of test microorganisms by using agar dilution method. All strains were susceptible and MIC values ranged from 4 to 512 microg/ml for propolis activity. Propolis from Kazan-Ankara showed most effective MIC values to the studied microorganisms. MBC values of Kazan-Ankara EEP samples were ranged from 8 to 512 microg/ml. Death was observed within 4 h of incubation for Peptostreptococcus anaerobius and micros and Lactobacillus acidophilus and Actinomyces naeslundii, while 8 h for Prevotella oralis and Prevotella melaninogenica and Porphyromonas gingivalis, 12 h for Fusobacterium nucleatum, 16 h for Veillonella parvula. It was shown that propolis samples were more effective against Gram positive anaerobic bacteria than Gram negative ones. The organic chemical compositions of EEPs were determined by high-resolution gas chromatography coupled to mass spectrometry (GC-MS). The main compounds of EEPs were flavonoids such as pinobanksin, quercetin, naringenin, galangine, chrysin and aromatic acids such as cafeic acid. Because of increased antimicrobial resistance, propolis may be kept in mind in the treatment of oral cavity diseases.