A chimeric MERS-CoV virus-like particle vaccine protects mice against MERS-CoV challenge.

BACKGROUND: Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe respiratory disease in humans, with a case fatality rate of approximately 35%, thus posing a considerable threat to public health. The lack of approved vaccines or antivirals currently constitutes a barrier in controlling disease outbreaks and spread. METHODS: In this study, using a mammalian expression system, which is advantageous for maintaining correct protein glycosylation patterns, we constructed chimeric MERS-CoV virus-like particles (VLPs) and determined their immunogenicity and protective efficacy in mice. RESULTS: Western blot and cryo-electron microscopy analyses demonstrated that MERS-CoV VLPs were efficiently produced in cells co-transfected with MERS-CoV spike (S), envelope, membrane and murine hepatitis virus nucleocapsid genes. We examined their ability as a vaccine in a human dipeptidyl peptidase 4 knock-in C57BL/6 congenic mouse model. Mice immunized with MERS VLPs produced S-specific antibodies with virus neutralization activity. Furthermore, MERS-CoV VLP immunization provided complete protection against a lethal challenge with mouse-adapted MERS-CoV and improved virus clearance in the lung. CONCLUSIONS: Overall, these data demonstrate that MERS-CoV VLPs have excellent immunogenicity and represent a promising vaccine candidate.

Archaeal RNA polymerase and transcription regulation.

To elucidate the mechanism of transcription by cellular RNA polymerases (RNAPs), high-resolution X-ray crystal structures together with structure-guided biochemical, biophysical, and genetics studies are essential. The recently solved X-ray crystal structures of archaeal RNAP allow a structural comparison of the transcription machinery among all three domains of life. The archaea were once thought of closely related to bacteria, but they are now considered to be more closely related to the eukaryote at the molecular level than bacteria. According to these structures, the archaeal transcription apparatus, which includes RNAP and general transcription factors (GTFs), is similar to the eukaryotic transcription machinery. Yet, the transcription regulators, activators and repressors, encoded by archaeal genomes are closely related to bacterial factors. Therefore, archaeal transcription appears to possess an intriguing hybrid of eukaryotic-type transcription apparatus and bacterial-like regulatory mechanisms. Elucidating the transcription mechanism in archaea, which possesses a combination of bacterial and eukaryotic transcription mechanisms that are commonly regarded as separate and mutually exclusive, can provide data that will bring basic transcription mechanisms across all life forms.

Insights into the Pathogenesis and Development of Recombinant Japanese Encephalitis Virus Genotype 3 as a Vaccine.

Japanese encephalitis virus (JEV), a flavivirus transmitted by mosquitoes, has caused epidemics and severe neurological diseases in Asian countries. In this study, we developed a cDNA infectious clone, pBAC JYJEV3, of the JEV genotype 3 strain (EF571853.1) using a bacterial artificial chromosome (BAC) vector. The constructed infectious clone was transfected into Vero cells, where it exhibited infectivity and induced cytopathic effects akin to those of the parent virus. Confocal microscopy confirmed the expression of the JEV envelope protein. Comparative analysis of growth kinetics revealed similar replication dynamics between the parental and recombinant viruses, with peak titers observed 72 h post-infection (hpi). Furthermore, plaque assays demonstrated comparable plaque sizes and morphologies between the viruses. Cryo-electron microscopy confirmed the production of recombinant virus particles with a morphology identical to that of the parent virus. Immunization studies in mice using inactivated parental and recombinant viruses revealed robust IgG responses, with neutralizing antibody production increasing over time. These results showcase the successful generation and characterization of a recombinant JEV3 virus and provide a platform for further investigations into JEV pathogenesis and vaccine development.

Cryo-EM structures of the plant anion channel SLAC1 from Arabidopsis thaliana suggest a combined activation model.

The anion channel SLAC1 functions as a crucial effector in the ABA signaling, leading to stomata closure. SLAC1 is activated by phosphorylation in its intracellular domains. Both a binding-activation model and an inhibition-release model for activation have been proposed based on only the closed structures of SLAC1, rendering the structure-based activation mechanism controversial. Here we report cryo-EM structures of Arabidopsis SLAC1 WT and its phosphomimetic mutants in open and closed states. Comparison of the open structure with the closed ones reveals the structural basis for opening of the conductance pore. Multiple phosphorylation of an intracellular domain (ICD) causes dissociation of ICD from the transmembrane domain. A conserved, positively-charged sequence motif in the intracellular loop 2 (ICL2) seems to be capable of sensing of the negatively charged phosphorylated ICD. Interactions between ICL2 and ICD drive drastic conformational changes, thereby widening the pore. From our results we propose that SLAC1 operates by a mechanism combining the binding-activation and inhibition-release models.

Cryo-EM structures of GroEL:ES2 with RuBisCO visualize molecular contacts of encapsulated substrates in a double-cage chaperonin.

The GroEL/GroES chaperonin system assists the folding of many proteins, through conformational transitions driven by ATP hydrolysis. Although structural information about bullet-shaped GroEL:ES1 complexes has been extensively reported, the substrate interactions of another functional complex, the football-shaped GroEL:ES2, remain elusive. Here, we report single-particle cryo-EM structures of reconstituted wild-type GroEL:ES2 complexes with a chemically denatured substrate, ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO). Our structures demonstrate that native-like folded RuBisCO density is captured at the lower part of the GroEL chamber and that GroEL's bulky hydrophobic residues Phe281, Tyr360, and Phe44 contribute to direct contact with RuBisCO density. In addition, our analysis found that GroEL:ES2 can be occupied by two substrates simultaneously, one in each chamber. Together, these observations provide insights to the football-shaped GroEL:ES2 complex as a functional state to assist the substrate folding with visualization.

Structure of the DNA-binding domain of NgTRF1 reveals unique features of plant telomere-binding proteins.

Telomeres are protein-DNA elements that are located at the ends of linear eukaryotic chromosomes. In concert with various telomere-binding proteins, they play an essential role in genome stability. We determined the structure of the DNA-binding domain of NgTRF1, a double-stranded telomere-binding protein of tobacco, using multidimensional NMR spectroscopy and X-ray crystallography. The DNA-binding domain of NgTRF1 contained the Myb-like domain and C-terminal Myb-extension that is characteristic of plant double-stranded telomere-binding proteins. It encompassed amino acids 561-681 (NgTRF1(561-681)), and was composed of 4 alpha-helices. We also determined the structure of NgTRF1(561-681) bound to plant telomeric DNA. We identified several amino acid residues that interacted directly with DNA, and confirmed their role in the binding of NgTRF1 to telomere using site-directed mutagenesis. Based on a structural comparison of the DNA-binding domains of NgTRF1 and human TRF1 (hTRF1), NgTRF1 has both common and unique DNA-binding properties. Interaction of Myb-like domain with telomeric sequences is almost identical in NgTRF1(561-681) with the DNA-binding domain of hTRF1. The interaction of Arg-638 with the telomeric DNA, which is unique in NgTRF1(561-681), may provide the structural explanation for the specificity of NgTRF1 to the plant telomere sequences, (TTTAGGG)(n).

Omega Rhodopsins: A Versatile Class of Microbial Rhodopsins.

Microbial rhodopsins are a superfamily of photoactive membrane proteins with covalently bound retinal cofactor. Isomerization of the retinal chromophore upon absorption of a photon triggers conformational changes of the protein to function as ion pumps or sensors. After the discovery of proteorhodopsin in an uncultivated γ-proteobacterium, light-activated proton pumps have been widely detected among marine bacteria and, together with chlorophyll-based photosynthesis, are considered as an important axis responsible for primary production in the biosphere. Rhodopsins and related proteins show a high level of phylogenetic diversity; we focus on a specific class of bacterial rhodopsins containing the 3 omega motif. This motif forms a stack of three nonconsecutive aromatic amino acids that correlates with the B-C loop orientation, and is shared among the phylogenetically close ion pumps such as the NDQ motif-containing sodium-pumping rhodopsin, the NTQ motif-containing chloride-pumping rhodopsin, and some proton-pumping rhodopsins including xanthorhodopsin. Here, we reviewed the recent research progress on these omega rhodopsins, and speculated on their evolutionary origin of functional diversity..

Transcriptome Analysis of Genes Involved in Cold Hardiness of Peach Tree (Prunus persica) Shoots during Cold Acclimation and Deacclimation.

We analyzed the transcriptomes in the shoots of five-year-old 'Soomee' peach trees (Prunus persica) during cold acclimation (CA), from early CA (end of October) to late CA (middle of January), and deacclimation (DA), from late CA to late DA (middle of March), to identify the genes involved in cold hardiness. Cold hardiness of the shoots increased from early to late CA, but decreased from late CA to late DA, as indicated by decreased and increased the median lethal temperature (LT50), respectively. Transcriptome analysis identified 17,208 assembled transcripts during all three stages. In total, 1891 and 3008 transcripts were differentially expressed with a |fold change| > 2 (p < 0.05) between early and late CA, and between late CA and late DA, respectively. Among them, 1522 and 2830, respectively, were functionally annotated with gene ontology (GO) terms having a greater proportion of differentially expressed genes (DEGs) associated with molecular function than biological process or cellular component categories. The biochemical pathways best represented both periods from early to late CA and from late CA to late DA were 'metabolic pathway' and 'biosynthesis of secondary metabolites'. We validated these transcriptomic results by performing reverse transcription quantitative polymerase chain reaction on the selected DEGs showing significant fold changes. The relative expressions of the selected DEGs were closely related to the LT50 values of the peach tree shoots: 'Soomee' shoots exhibited higher relative expressions of the selected DEGs than shoots of the less cold-hardy 'Odoroki' peach trees. Irrespective of the cultivar, the relative expressions of the DEGs that were up- and then down-regulated during CA, from early to late CA, and DA, from late CA to late DA, were more closely correlated with cold hardiness than those of the DEGs that were down- and then up-regulated. Therefore, our results suggest that the significantly up- and then down-regulated DEGs are associated with cold hardiness in peach tree shoots. These DEGs, including early light-induced protein 1, chloroplastic, 14-kDa proline-rich protein DC2.15, glutamate dehydrogenase 2, and triacylglycerol lipase 2, could be candidate genes to determine cold hardiness.

Direct binding of TFEα opens DNA binding cleft of RNA polymerase.

Opening of the DNA binding cleft of cellular RNA polymerase (RNAP) is necessary for transcription initiation but the underlying molecular mechanism is not known. Here, we report on the cryo-electron microscopy structures of the RNAP, RNAP-TFEα binary, and RNAP-TFEα-promoter DNA ternary complexes from archaea, Thermococcus kodakarensis (Tko). The structures reveal that TFEα bridges the RNAP clamp and stalk domains to open the DNA binding cleft. Positioning of promoter DNA into the cleft closes it while maintaining the TFEα interactions with the RNAP mobile modules. The structures and photo-crosslinking results also suggest that the conserved aromatic residue in the extended winged-helix domain of TFEα interacts with promoter DNA to stabilize the transcription bubble. This study provides a structural basis for the functions of TFEα and elucidates the mechanism by which the DNA binding cleft is opened during transcription initiation in the stalk-containing RNAPs, including archaeal and eukaryotic RNAPs.

Structural basis for arginine glycosylation of host substrates by bacterial effector proteins.

The bacterial effector proteins SseK and NleB glycosylate host proteins on arginine residues, leading to reduced NF-κB-dependent responses to infection. Salmonella SseK1 and SseK2 are E. coli NleB1 orthologs that behave as NleB1-like GTs, although they differ in protein substrate specificity. Here we report that these enzymes are retaining glycosyltransferases composed of a helix-loop-helix (HLH) domain, a lid domain, and a catalytic domain. A conserved HEN motif (His-Glu-Asn) in the active site is important for enzyme catalysis and bacterial virulence. We observe differences between SseK1 and SseK2 in interactions with substrates and identify substrate residues that are critical for enzyme recognition. Long Molecular Dynamics simulations suggest that the HLH domain determines substrate specificity and the lid-domain regulates the opening of the active site. Overall, our data suggest a front-face SNi mechanism, explain differences in activities among these effectors, and have implications for future drug development against enteric pathogens.

In-vitro and in-vivo anti-inflammatory action of the ethanol extract of Trachelospermi caulis.

In this study, we aimed to investigate the anti-inflammatory activity, antinociceptive activity and the action mechanism of Trachelospermi caulis extract. The anti-inflammatory effects were investigated using arachidonic acid, 12-O-tetradecanoylphorbol 13-acetate or carrageenan-induced oedema assays. Antinociceptive activity, using the acetic acid-induced writhing model, was also tested in mice. The extract exhibited dose-dependent and significant (P<0.05 at 100-400 mg kg-1) anti-inflammatory and antinociceptive activity in the animals. To further understand the mechanism of activity, we investigated whether the extract inhibited the expression of inducible nitric oxide synthase (iNOS), the production of nitric oxide (NO) and the expression of TNF-alpha from murine macrophage RAW 264.7 cells. Similar to the in-vivo activity, the iNOS expression, NO production and TNF-alpha expression were found to be dose dependent and significantly suppressed by the extract through the inhibition of the p38 MAP kinase/NF-kappaB pathway. Taken together, the results presented here suggest that T. caulis extract may be useful for the treatment of various inflammatory diseases.

The anti-inflammatory effects of Pyrolae herba extract through the inhibition of the expression of inducible nitric oxide synthase (iNOS) and NO production.

The extract of Pyrolae herba (PH), which has been used as an anti-inflammatory folk remedy in Korea and China, was investigated for its anti-inflammatory action using arachidonic acid, 12-O-tetradecanoylphorbol 13-acetate or carrageenan-induced edema assays. The anti-nociceptive activity of PH was also tested in mice using the acetic acid-induced writhing model. PH showed dose-dependent and significant (P<0.05 at 100-400mg/kg) anti-inflammatory and anti-nociceptive activities in the animal assays. The mechanism of the activities of PH was examined by testing the extract to determine if it inhibits the expression of inducible nitric oxide synthase (iNOS) and the production of nitric oxide (NO) from the murine macrophages, RAW 264.7 cells. Similar to the in vivo activities, both the iNOS expression and NO production were significantly suppressed by PH in a dose-dependent manner. PH also inhibited the activating phosphorylation of p38 MAP kinase and NF-kappaB in these cells. These results provide a scientific basis to explain the effects of PH as an anti-inflammatory folk remedy in Asian countries.

DNA mismatch repair system. Classical and fresh roles.

The molecular mechanisms of the DNA mismatch repair (MMR) system have been uncovered over the last decade, especially in prokaryotes. The results obtained for prokaryotic MMR proteins have provided a framework for the study of the MMR system in eukaryotic organisms, such as yeast, mouse and human, because the functions of MMR proteins have been conserved during evolution from bacteria to humans. However, mutations in eukaryotic MMR genes result in pleiotropic phenotypes in addition to MMR defects, suggesting that eukaryotic MMR proteins have evolved to gain more diverse and specific roles in multicellular organisms. Here, we summarize recent advances in the understanding of both prokaryotic and eukaryotic MMR systems and describe various new functions of MMR proteins that have been intensively researched during the last few years, including DNA damage surveillance and diversification of antibodies.

Crystal structure and functional characterization of a light-driven chloride pump having an NTQ motif.

A novel light-driven chloride-pumping rhodopsin (ClR) containing an 'NTQ motif' in its putative ion conduction pathway has been discovered and functionally characterized in a genomic analysis study of a marine bacterium. Here we report the crystal structure of ClR from the flavobacterium Nonlabens marinus S1-08(T) determined under two conditions at 2.0 and 1.56 Å resolutions. The structures reveal two chloride-binding sites, one around the protonated Schiff base and the other on a cytoplasmic loop. We identify a '3 omega motif' formed by three non-consecutive aromatic amino acids that is correlated with the B-C loop orientation. Detailed ClR structural analyses with functional studies in E. coli reveal the chloride ion transduction pathway. Our results help understand the molecular mechanism and physiological role of ClR and provide a structural basis for optogenetic applications.

Characterization of an abiotic stress-inducible dehydrin gene, OsDhn1, in rice (Oryza sativa L.).

A full-length 1.1 kb cDNA, designated Oryza sativa Dehydrin 1 (OsDhn1), was isolated from the seed coat of rice. The deduced protein is hydrophilic and has three K-type and one S-type motifs (SK3-type), indicating that OsDhn1 belongs to the acidic dehydrin family, which includes wheat WCOR410 and Arabidopsis COR47. Expression of OsDhn1 was strongly induced by low temperature as well as by drought. Induction of OsDhn1 by cold stress was clearcut in the roots of seedlings and the epidermis of palea and lemma. OsDhn1 was also up-regulated in UBI::CBF1/DREB1b transgenic plants indicating that it is regulated by the CBF/DREB stress signaling pathway.

Molecular characterization of a GA-inducible gene, Cvsus1, in developing watermelon seeds.

To understand the molecular mechanisms that control seed development, we isolated a seed-preferential gene from ESTs of developing watermelon seeds. The gene Cvsus1 encodes a protein that is 86% identical to the Vicia faba sucrose synthase expressed in developing seeds. RNA blot analysis showed that Cvsus1 was preferentially expressed in watermelon seeds. We also investigated gene expression levels both in pollinated seeds and in parthenocarpic seeds, which lack zygotic tissues. Whereas the transcript level of Cvsus1 was rapidly increased during normal seed development, the expression was not significantly increased in the parthenocarpic seeds. However, treating the parthenocarpic fruits with GA3 strongly induced Cvsus1 expression, up to the level accumulated in pollinated seeds. These results suggest that Cvsus1 is induced in maternal tissues via signals from the zygotic tissues, and that GA may be one of those signals.

The X-ray crystal structure of the euryarchaeal RNA polymerase in an open-clamp configuration.

The archaeal transcription apparatus is closely related to the eukaryotic RNA polymerase II (Pol II) system. Archaeal RNA polymerase (RNAP) and Pol II evolved from a common ancestral structure and the euryarchaeal RNAP is the simplest member of the extant archaeal-eukaryotic RNAP family. Here we report the first crystal structure of euryarchaeal RNAP from Thermococcus kodakarensis (Tko). This structure reveals that the clamp domain is able to swing away from the main body of RNAP in the presence of the Rpo4/Rpo7 stalk by coordinated movements of these domains. More detailed structure-function analysis of yeast Pol II and Tko RNAP identifies structural additions to Pol II that correspond to the binding sites of Pol II-specific general transcription factors including TFIIF, TFIIH and Mediator. Such comparisons provide a framework for dissecting interactions between RNAP and these factors during formation of the pre-initiation complex.

Treatment with SI000413, a new herbal formula, ameliorates murine collagen-induced arthritis.

We tested the effects of SI000413, a new formula, consisting of Pyrolae herba and Trachelospermi caulis, on type II collagen-induced arthritis (CIA). CIA was induced in DBA/1J mice by immunization with bovine type II collagen (CII) on days 1 and 21. SI000413 was orally administered 3 times per week throughout the experiment and indomethacin was served as a positive control. Clinical scores, the count of arthritic legs, levels of interleukin 6 (IL-6) and anti-CII antibody, and lymphocyte subsets in blood were examined. SI000413 suppressed CIA development in a dose dependent manner and reduced the incidence of arthritic legs in mice. Histological analysis showed administration of SI000413 reduced inflammatory signs and cartilage destruction. Serum levels of IL-6 and anti-CII antibody were significantly decreased in SI000413-treated mice and the percentages of CD4 T cell, CD8 T cell and B cell in blood were restored to normal levels. In conclusion, we demonstrate that SI000413 ameliorates CIA both clinically and histologically and inhibits the production of anti-CII antibody and pro-inflammatory cytokine in the CIA mouse. These findings suggest that SI000413 is a potential new therapeutic herbal formula for the treatment of RA.

Molecular cloning and expression analysis of the cell-wall invertase gene family in rice (Oryza sativa L.).

Cell-wall invertase (CIN) catalyzes the hydrolysis of sucrose into glucose and fructose for the supply of carbohydrates to sink organs via an apoplastic pathway. To study the CIN genes in rice (Oryza sativa L.), we isolated cDNA clones showing amino acid similarity to the plant cell wall invertase proteins from a search of rice sequence databases. Profile analyses revealed that the cloned genes are expressed in unique patterns in various organs. For example, transcripts of OsCIN1, OsCIN2, OsCIN4, and OsCIN7 were detected in immature seeds whereas OsCIN3 gene expression was flower-specific. Further transcript analysis of these genes expressed in developing seeds indicated that OsCIN1, OsCIN2, and OsCIN7 might play an important role involving sucrose partitioning to the embryo and endosperm. Sucrose, a substrate of CINs, induced the accumulation of OsCIN1 transcripts in excised leaves and OsCIN2 in immature seeds, while the level of OsCIN5 was significantly down-regulated in excised leaves treated with sucrose. Infecting the tissues with rice blast (Magnaporthe grisea) as a biotic stressor increased the expression of OsCIN1, OsCIN4, and OsCIN5, suggesting that these genes may participate in a switch in metabolism to resist pathogen invasion. These results demonstrate that OsCIN genes play diverse roles involving the regulation of metabolism, growth, development, and stress responses.

CvADH1, a member of short-chain alcohol dehydrogenase family, is inducible by gibberellin and sucrose in developing watermelon seeds.

To understand the molecular mechanisms that control seed formation, we selected a seed-preferential gene (CvADH1) from the ESTs of developing watermelon seeds. RNA blot analysis and in situ localization showed that CvADH1 was preferentially expressed in the nucellar tissue. The CvADH1 protein shared about 50% homology with short-chain alcohol dehydrogenase including ABA2 in Arabidopsis thaliana, stem secoisolariciresinol dehydrogenase in Forsythia intermedia, and 3beta-hydroxysterol dehydrogenase in Digitalis lanata. We investigated gene-expression levels in seeds from both normally pollinated fruits and those made parthenocarpic via N-(2-chloro-4-pyridyl)-N'-phenylurea treatment, the latter of which lack zygotic tissues. Whereas the transcripts of CvADH1 rapidly started to accumulate from about the pre-heart stage in normal seeds, they were not detectable in the parthenocarpic seeds. Treating the parthenogenic fruit with GA(3) strongly induced gene expression, up to the level accumulated in pollinated seeds. These results suggest that the CvADH1 gene is induced in maternal tissues by signals made in the zygotic tissues, and that gibberellin might be one of those signals. We also observed that CvADH1 expression was induced by sucrose in the parthenocarpic seeds. Therefore, we propose that the CvADH1 gene is inducible by gibberellin, and that sucrose plays an important role in the maternal tissues of watermelon during early seed development.