Genotoxic and cytotoxic effects induced by aluminum in the lymphocytes of the common carp (Cyprinus carpio)

Few studies have been made in regard to the effect of aluminum on the molecular and cellular structure and function of aquatic organisms; therefore, in the present report we determined the genotoxic and cytotoxic effects induced by the metal on the lymphocytes of carp (Cyprinus carpio). Three groups of fish were exposed to 0.05, 120, and 239 mg/L of aluminum (Al), respectively, by using Al₂ (SO₄)₃·7H₂O, and another group was included as control. The cells obtained were studied with the comet assay, flow cytometry, and the TUNEL method. With the first method we found a concentration and time dependent, significant increase in the amount of DNA damage induced by Al, and a higher damage when we evaluated the level of oxidized DNA. By applying flow cytometry we established that the metal induced a DNA content increase and ploidy modifications as well as apoptosis and disturbances of the cell cycle progression. With the last method we determined a significant increase in the amount of apoptotic cells, mainly in the 72–96 h period. Our results established that Al caused deleterious DNA and cellular effects in the tested organism, and they suggested the pertinence of evaluating toxicity induced by the metal in organisms living in contaminated water bodies.     

Deoxyhypusine synthase haploinsufficiency attenuates acute cytokine signaling

Deoxyhypusine synthase (DHS) catalyzes the post-translational formation of the amino acid hypusine. Hypusine is unique to the eukaryotic translational initiation factor 5A (eIF5A), and is required for its functions in mRNA shuttling, translational elongation and stress granule formation. In recent studies, we showed that DHS promotes cytokine and ER stress signaling in the islet β cell and thereby contributes to its dysfunction in the setting of diabetes mellitus. Here, we review the evidence supporting a role for DHS (and hypusinated eIF5A) in cellular stress responses, and provide new data on the phenotype of DHS knockout mice. We show that homozygous knockout mice are embryonic lethal, but heterozygous knockout mice appear normal with no evidence of growth or metabolic deficiencies. Mouse embryonic fibroblasts from heterozygous knockout mice attenuate acute cytokine signaling, as evidenced by reduced production of inducible nitric oxide synthase, but show no statistically significant defects in proliferation or cell cycle progression. Our data are discussed with respect to the utility of sub- maximal inhibition of DHS in the setting of inflammatory states, such as diabetes mellitus.Key words: inflammation, post-translational modification, cytokine, diabetes, mRNA translation, hypusine     

Defining salivary biomarkers using mass spectrometry-based proteomics: a systematic review

Recent advancements in mass spectrometric proteomics provide a promising result in utilizing saliva to explore biomarkers for diagnostic purposes. However, the issues of specificity or redundancy of disease-associated salivary biomarkers have not been described. This systematic review was therefore aimed to define and summarize disease-related salivary biomarkers identified by mass spectrometry proteomics. Peer-reviewed articles published through July 2009 within three databases were reviewed. Out of 243 articles, 21 studies were selected in this systematic review with conditions including Sj?gren's syndrome, squamous cell carcinoma, dental caries, diabetes, breast cancer, periodontitis, gastric cancer, systemic sclerosis, oral lichen planus, bleeding oral cavity, and graft-versus-host disease. The sample size ranged from 3-41 in both diseased and control subjects, with no consensus on sample collection protocol. One hundred eighty biomarkers were identified in total; 87 upregulated, 63 downregulated, and 30 varying based on disease. Except for Sj?gren's syndrome, the majority of studies with the same disease produce inconsistent biomarkers. Larger sample size and standardization of sample collection/treatment protocol may improve future studies.     

Auxin acts independently of DELLA proteins in regulating gibberellin levels

Shoot elongation is a vital process for plant development and productivity, in both ecological and economic contexts. Auxin and bioactive gibberellins (GAs), such as GA₁, play critical roles in the control of elongation,^1–3 along with environmental and endogenous factors, including other hormones such as the brassinosteroids.^4,5 The effect of auxins, such as indole-3-acetic acid (IAA), is at least in part mediated by its effect on GA metabolism,⁶ since auxin upregulates biosynthesis genes such as GA 3-oxidase and GA 20-oxidase and downregulates GA catabolism genes such as GA 2-oxidases, leading to elevated levels of bioactive GA₁.⁷ In our recent paper,¹ we have provided evidence that this action of IAA is largely independent of DELLA proteins, the negative regulators of GA action,^8,9 since the auxin effects are still present in the DELLA-deficient la cry-s genotype of pea. This was a crucial issue to resolve, since like auxin, the DELLAs also promote GA₁ synthesis and inhibit its deactivation. DELLAs are deactivated by GA, and thereby mediate a feedback system by which bioactive GA regulates its own level.¹⁰ However, our recent results,¹ in themselves, do not show the generality of the auxin-GA relationship across species and phylogenetic groups or across different tissue types and responses. Further, they do not touch on the ecological benefits of the auxin-GA interaction. These issues are discussed below as well as the need for the development of suitable experimental systems to allow this process to be examined.Key words: auxin, gibberellins, DELLA proteins, interactions, elongation     

Ku must load directly onto the chromosome end in order to mediate its telomeric functions

The Ku heterodimer associates with the Saccharomyces cerevisiae telomere, where it impacts several aspects of telomere structure and function. Although Ku avidly binds DNA ends via a preformed channel, its ability to associate with telomeres via this mechanism could be challenged by factors known to bind directly to the chromosome terminus. This has led to uncertainty as to whether Ku itself binds directly to telomeric ends and whether end association is crucial for Ku's telomeric functions. To address these questions, we constructed DNA end binding-defective Ku heterodimers by altering amino acid residues in Ku70 and Ku80 that were predicted to contact DNA. These mutants continued to associate with their known telomere-related partners, such as Sir4, a factor required for telomeric silencing, and TLC1, the RNA component of telomerase. Despite these interactions, we found that the Ku mutants had markedly reduced association with telomeric chromatin and null-like deficiencies for telomere end protection, length regulation, and silencing functions. In contrast to Ku null strains, the DNA end binding defective Ku mutants resulted in increased, rather than markedly decreased, imprecise end-joining proficiency at an induced double-strand break. This result further supports that it was the specific loss of Ku's telomere end binding that resulted in telomeric defects rather than global loss of Ku's functions. The extensive telomere defects observed in these mutants lead us to propose that Ku is an integral component of the terminal telomeric cap, where it promotes a specific architecture that is central to telomere function and maintenance.     

Coronavirus nsp6 proteins generate autophagosomes from the endoplasmic reticulum via an omegasome intermediate

Autophagy is a cellular response to starvation which generates autophagosomes to carry cellular organelles and long-lived proteins to lysosomes for degradation. Degradation through autophagy can provide an innate defence against virus infection, or conversely autophagosomes can promote infection by facilitating assembly of replicase proteins. We demonstrate that the avian coronavirus, Infectious Bronchitis Virus (IBV) activates autophagy. A screen of individual IBV non-structural proteins (nsps) showed that autophagy was activated by IBV nsp6. This property was shared with nsp6 of mammalian coronaviruses Mouse Hepatitis Virus, and Severe Acute Respiratory Syndrome Virus, and the equivalent nsp5-7 of the arterivirus Porcine Reproductive and Respiratory Syndrome Virus. These multiple-spanning transmembrane proteins located to the endoplasmic reticulum (ER) where they generated Atg5 and LC3II-positive vesicles, and vesicle formation was dependent on Atg5 and class III PI3 kinase. The vesicles recruited double FYVE-domain containing protein (DFCP) indicating localised concentration of phosphatidylinositol 3 phosphate, and therefore shared many features with omegasomes formed from the ER in response to starvation. Omegasomes induced by viral nsp6 matured into autophagosomes that delivered LC3 to lysosomes and therefore recruited and recycled the proteins needed for autophagosome nucleation, expansion, cellular trafficking and delivery of cargo to lysosomes. The coronavirus nsp6 proteins activated omegasome and autophagosome formation independently of starvation, but activation did not involve direct inhibition of mTOR signalling, activation of sirtuin1 or induction of ER stress.     

Identification, replication, and fine-mapping of Loci associated with adult height in individuals of african ancestry

Adult height is a classic polygenic trait of high heritability (h ² ∼0.8). More than 180 single nucleotide polymorphisms (SNPs), identified mostly in populations of European descent, are associated with height. These variants convey modest effects and explain ∼10% of the variance in height. Discovery efforts in other populations, while limited, have revealed loci for height not previously implicated in individuals of European ancestry. Here, we performed a meta-analysis of genome-wide association (GWA) results for adult height in 20,427 individuals of African ancestry with replication in up to 16,436 African Americans. We found two novel height loci (Xp22-rs12393627, P = 3.4×10⁻¹² and 2p14-rs4315565, P = 1.2×10⁻⁸). As a group, height associations discovered in European-ancestry samples replicate in individuals of African ancestry (P = 1.7×10⁻⁴ for overall replication). Fine-mapping of the European height loci in African-ancestry individuals showed an enrichment of SNPs that are associated with expression of nearby genes when compared to the index European height SNPs (P<0.01). Our results highlight the utility of genetic studies in non-European populations to understand the etiology of complex human diseases and traits.     

Pervasive sign epistasis between conjugative plasmids and drug-resistance chromosomal mutations

Multidrug-resistant bacteria arise mostly by the accumulation of plasmids and chromosomal mutations. Typically, these resistant determinants are costly to the bacterial cell. Yet, recently, it has been found that, in Escherichia coli bacterial cells, a mutation conferring resistance to an antibiotic can be advantageous to the bacterial cell if another antibiotic-resistance mutation is already present, a phenomenon called sign epistasis. Here we study the interaction between antibiotic-resistance chromosomal mutations and conjugative (i.e., self-transmissible) plasmids and find many cases of sign epistasis (40%)--including one of reciprocal sign epistasis where the strain carrying both resistance determinants is fitter than the two strains carrying only one of the determinants. This implies that the acquisition of an additional resistance plasmid or of a resistance mutation often increases the fitness of a bacterial strain already resistant to antibiotics. We further show that there is an overall antagonistic interaction between mutations and plasmids (52%). These results further complicate expectations of resistance reversal by interdiction of antibiotic use.     

The RecRO pathway of DNA recombinational repair in Helicobacter pylori and its role in bacterial survival in the host

Two pathways for DNA recombination, AddAB (RecBCD-like) and RecRO, were identified in Helicobacter pylori, a pathogenic bacterium that colonizes human stomachs resulting in a series of gastric diseases. In this study, we examined the physiological roles of H. pylori RecRO pathway in DNA recombinational repair. We characterized H. pylori single mutants in recR and in recO, genes in the putative gap repair recombination pathway, and an addA recO double mutant that is thus deficient in both pathways that initiate DNA recombinational repair. The recR or recO single mutants showed the same level of sensitivity to mitomycin C as the parent strain, suggesting that the RecRO pathway is not responsible for the repair of DNA double strand breaks. However, H. pylori recR and recO mutants are highly sensitive to oxidative stress and separately to acid stress, two major stress conditions that H. pylori encounters in its physiological niche. The complementation of the recR mutant restored the sensitivity to oxidative and acid stress to the wild type level. By measuring DNA transformation frequencies, the recR and recO single mutants were shown to have no effect on inter-genomic recombination, whereas the addA recO double mutant had a greatly (～12-fold) reduced transformation frequency. On the other hand, the RecRO pathway was shown to play a significant role in intra-genomic recombination with direct repeat sequences. Whereas the recA strain had a deletion frequency 35-fold lower than that of background level, inactivation of recR resulted in a 4-fold decrease in deletion frequency. In a mouse infection model, the three mutant strains displayed a greatly reduced ability to colonize the host stomachs. The geometric means of colonization number for the wild type, recR, recO, and addA recO strains were 6 x 10?, 1.6 x 10?, 1.4 x 10? and 4 x 103 CFU/g stomach, respectively. H. pylori RecRO-mediated DNA recombinational repair (intra-genomic recombination) is thus involved in repairing DNA damage induced by oxidative and acid stresses and plays an important role in bacterial survival and persistent colonization in the host.