Dephosphorylation of West Nile virus capsid protein enhances the processes of nucleocapsid assembly

West Nile virus (WNV) capsid (C) protein is one of the three viral structural proteins and it encapsidates the viral RNA to form the nucleocapsid. It is known to be a multifunctional protein involved in assembly and apoptosis. WNV C protein was previously found to be phosphorylated in infected cells and bioinformatic analysis revealed 5 putative phosphorylation sites at serine 26, 36, 83, 99 and threonine 100. Phosphorylation was abolished through mutagenesis of these putative phosphorylation sites to investigate how phosphorylation could affect the processes of nucleocapsid assembly like RNA binding, oligomerization and cellular localization. It was found that phosphorylation attenuated its RNA binding activity. Although oligomerization was not inhibited by mutagenesis of the putative phosphorylation sites, the rate of dimerization and oligomerization was affected. Hypophosphorylation of C protein reduced its nuclear localization efficiency and hence enhanced cytoplasmic localization. This study also revealed that although WNV C is phosphorylated in infected cells, the relative level of phosphorylation is reduced over the course of an infection to promote RNA binding and nucleocapsid formation in the cytoplasm. This is the first report to describe how dynamic phosphorylation of WNV C protein modulates the processes involved in nucleocapsid assembly.     

The genetic effect of copy number variations on the risk of type 2 diabetes in a Korean population

Background

Unlike Caucasian populations, genetic factors contributing to the risk of type 2 diabetes mellitus (T2DM) are not well studied in Asian populations. In light of this, and the fact that copy number variation (CNV) is emerging as a new way to understand human genomic variation, the objective of this study was to identify type 2 diabetes–associated CNV in a Korean cohort.

Methodology/Principal Findings

Using the Illumina HumanHap300 BeadChip (317,503 markers), genome-wide genotyping was performed to obtain signal and allelic intensities from 275 patients with type 2 diabetes mellitus (T2DM) and 496 nondiabetic subjects (Total n = 771). To increase the sensitivity of CNV identification, we incorporated multiple factors using PennCNV, a program that is based on the hidden Markov model (HMM). To assess the genetic effect of CNV on T2DM, a multivariate logistic regression model controlling for age and gender was used. We identified a total of 7,478 CNVs (average of 9.7 CNVs per individual) and 2,554 CNV regions (CNVRs; 164 common CNVRs for frequency>1%) in this study. Although we failed to demonstrate robust associations between CNVs and the risk of T2DM, our results revealed a putative association between several CNVRs including chr15:45994758–45999227 (P = 8.6E-04, P^corr = 0.01) and the risk of T2DM. The identified CNVs in this study were validated using overlapping analysis with the Database of Genomic Variants (DGV; 71.7% overlap), and quantitative PCR (qPCR). The identified variations, which encompassed functional genes, were significantly enriched in the cellular part, in the membrane-bound organelle, in the development process, in cell communication, in signal transduction, and in biological regulation.

Conclusion/Significance

We expect that the methods and findings in this study will contribute in particular to genome studies of Asian populations.     

Preparation of cyclodextrin chiral stationary phases by organic soluble catalytic 'click' chemistry

We describe an effective and simple protocol that uses click chemistry to attach native β-cyclodextrin (β-CD) to silica particles, resulting in a chiral stationary phase (CCNCSP) that can be used for the enantioseparation of chiral drugs by high-performance liquid chromatography (HPLC). Starting from β-CD, the CCNCSP is prepared in several steps: (i) reaction of β-CD with 1-(p-toluenesulfonyl)-imidazole to afford mono-6-toluenesulfonyl-β-CD; (ii) azidolysis of mono-6-toluenesulfonyl-β-CD in dimethylformamide to give mono-6-azido-β-CD (N(3)-CD); (iii) reaction of cuprous iodide with triphenylphosphine to form an organic soluble catalyst CuI(PPh(3)); (iv) preparation of alkynyl-modified silica particles; and (v) click chemistry immobilization of N(3)-CD onto alkynyl-modified silica to afford the desired chiral stationary phase. Synthesis of the stationary phase and column packing takes ～1 week.     

Mitochondrial Changes in Ageing Caenorhabditis elegans – What Do We Learn from Superoxide Dismutase Knockouts?

One of the most popular damage accumulation theories of ageing is the mitochondrial free radical theory of ageing (mFRTA). The mFRTA proposes that ageing is due to the accumulation of unrepaired oxidative damage, in particular damage to mitochondrial DNA (mtDNA). Within the mFRTA, the "vicious cycle" theory further proposes that reactive oxygen species (ROS) promote mtDNA mutations, which then lead to a further increase in ROS production. Recently, data have been published on Caenorhabditis elegans mutants deficient in one or both forms of mitochondrial superoxide dismutase (SOD). Surprisingly, even double mutants, lacking both mitochondrial forms of SOD, show no reduction in lifespan. This has been interpreted as evidence against the mFRTA because it is assumed that these mutants suffer from significantly elevated oxidative damage to their mitochondria. Here, using a novel mtDNA damage assay in conjunction with related, well established damage and metabolic markers, we first investigate the age-dependent mitochondrial decline in a cohort of ageing wild-type nematodes, in particular testing the plausibility of the "vicious cycle" theory. We then apply the methods and insights gained from this investigation to a mutant strain for C. elegans that lacks both forms of mitochondrial SOD. While we show a clear age-dependent, linear increase in oxidative damage in WT nematodes, we find no evidence for autocatalytic damage amplification as proposed by the "vicious cycle" theory. Comparing the SOD mutants with wild-type animals, we further show that oxidative damage levels in the mtDNA of SOD mutants are not significantly different from those in wild-type animals, i.e. even the total loss of mitochondrial SOD did not significantly increase oxidative damage to mtDNA. Possible reasons for this unexpected result and some implications for the mFRTA are discussed.