Thesis (Ph.D.)--University of Alabama at Birmingham, 2008. / Title from PDF title page (viewed on July 13, 2010). Includes bibliographical references.

No description available.

Tombusviruses are single, positive strand RNA viruses of plants, often associated with parasitic defective interfering (DI) RNAs. Two viral- coded gene products, namely p33 and p92, are required for tombusvirus replication. The overlapping domains of p33 and p92 contain an arginine/proline-rich (RPR) RNA binding motif. In this study, the role of RPR motif and viral RNA in tombusvirus replication and recombination, as well as involvement of viral RNA in tombusvirus replicase assembly was examined. Using site-directed mutagenesis I generated a series of RPR mutants of Cucumber necrosis tombusvirus (CNV). Analysis of RPR mutants defined that wild type RPR motif, especially two of the four arginines, were required for efficient RNA binding in vitro, for replication of tombusviruses, their associated DI RNAs, subgenomic (sg)RNA synthesis and DI RNA recombination in vivo. Experiments using a two-component tombusvirus replication system showed that RPR motif is critical for functions of both p33 and p92 in replication, but its role in these proteins might not be identical. Recombination studies using a novel tombusvirus three-component system revealed that mutations in RPR motif of p33 replicase protein resulted in an altered viral RNA recombination rate. Identified DI RNA recombinants were mostly imprecise, with recombination sites clustered around a replication enchancer and an additional putative cis-acting element that might facilitate the template switching events by the tombusvirus replicase. To study the role of RNA during the assembly of functional tombusvirus replicase, recombinant CNV replicase that showed similar properties to plant-derived CNV replicase was purified from Saccharomyces cerevisiae. When in addition to p33 and p92 proteins DI RNA was co-expressed in yeast cells, the isolated replicase activity was increased ~40 fold. Further studies defined RNA motifs within two short DI RNA regions that enhanced active CNV replicase formation. In summary, this study showed that the conserved RNA binding motif of the tombusvirus replicase proteins and viral RNA are involved in replicase assembly, viral RNA replication, subgenomic RNA synthesis and RNA recombination. This data shed new light on the complex roles of the viral elements in replication, and will help future studies aimed at interfering with viral infections.

Two thirds of plant viruses are positive-strand RNA viruses including the family Tombusviridae. One of the best-studied members of this family is Tomato bushy stunt virus (TBSV). Like many other viruses, TBSV has much fewer genes when compared to its hosts’ genome. Nevertheless, TBSV utilizes its genome very judiciously. To compensate for a lack of many proteins of its own, it codes for multi-functional replication protein p33 and also co-opts host factors to facilitate its replication. By using recombinant replication proteins p33 and p92 containing single amino acid changes in protein-protein interaction domains (S1 and S2), I demonstrated that the replication proteins are required in sequential steps during virus replication. The in vitro cell-free extract(CFE) based TBSV replication assays revealed that mutations in S1 and S2 domains affected RNA template selection, recruitment and assembly of replicase complex. TBSV replicates on the cytosolic surface of peroxisomal membranes. To identify the host factor involved in this process of transporting viral replication proteins to peroxisome, I tested the peroxisomal transporter proteins for their ability to bind to p33 in vitro, which led to the discovery of Pex19p. Pull-down and co-purification experiments revealed transient nature of p33-Pex19p binding as expected from a transporter. When pex19p was retargeted to mitochondria, a large fraction of p33 was also re-distributed to the mitochondria validating the importance of Pex19p in p33 localization. TBSV also utilizes its genomic RNA for non-template activities during its replication. Accordingly, TBSV RNA serves as a platform for the assembly of replicase complex. To further characterize the regulatory cis-elements involved in this process, I utilized CFE and different TBSV RNA mutants together with recombinant p33 and p92 in vitro replication assays. These experiments revealed the role of RNA recruitment element [RIISL(+)] and 3’ non-coding regions as minimal cis-elements required to assemble functional replicase complex. The experiments also indicated that the RIISL(+) and 3’ non coding regions could be physically separated on two different RNA molecules to assemble TBSV replicase, suggesting insights into viral evolution.

Ho Hei Ming. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 189-199). / Abstracts in English and Chinese. / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Epidemiology of the Severe Acute Respiratory Syndrome (SARS) Outbreak --- p.2 / Chapter 1.2 --- The SARS Coronavirus --- p.3 / Chapter 1.2.1 --- Genome organization --- p.7 / Chapter 1.2.2 --- Structural proteins --- p.9 / Chapter 1.2.3 --- Non-structural proteins --- p.11 / Chapter 1.3 --- Introduction to SARS-CoV nsp10 Protein --- p.14 / Chapter 1.4 --- Introduction to SARS-CoV RNA-dependent RNA Polymerase (RdRp) Protein --- p.17 / Chapter 1.5 --- Objectives of the Present Study --- p.25 / Chapter Chapter 2 --- Materials and Methods / Chapter 2.1 --- Construction of Glutathione S-Transferase (GST) Fusion/Green Fluorescence Protein (GFP) N1 and C1 Fusion nsplO --- p.26 / Chapter 2.1.1 --- Primer design --- p.26 / Chapter 2.1.2 --- Gene amplification by PCR --- p.28 / Chapter 2.1.3 --- Purification of PCR product --- p.30 / Chapter 2.1.4 --- Enzyme restriction --- p.31 / Chapter 2.1.5 --- Ligation --- p.33 / Chapter 2.1.6 --- Transformation --- p.34 / Chapter 2.1.6.1 --- Preparation of competent cell DH5α --- p.34 / Chapter 2.1.7 --- Mini scale plasmid preparation --- p.36 / Chapter 2.2 --- Subcellular Localization Study --- p.39 / Chapter 2.2.1 --- Midi scale plasmid preparation --- p.39 / Chapter 2.2.2 --- Transfection of GFP recombinant plasmids --- p.41 / Chapter 2.2.2.1 --- Cell culture of Vero E6 cell line --- p.41 / Chapter 2.2.2.2 --- Lipofectamine based transfection --- p.41 / Chapter 2.2.3 --- Fluorescent microscopic visualization --- p.42 / Chapter 2.2.4 --- Western blotting for GFP fusion protein expression --- p.43 / Chapter 2.2.4.1 --- Protein extraction --- p.43 / Chapter 2.2.4.2 --- Protein quantification --- p.44 / Chapter 2.2.3.4 --- SDS-PAGE analysis --- p.45 / Chapter 2.3 --- "Expression of GFP-nsp10 in Vero E6 cells, SARS-CoV Infected Vero E6 Cells and Convalescent Patients' Serum" --- p.47 / Chapter 2.3.1 --- Cell-based immunostaining of VeroE6 cells and SARS-CoV infected Vero E6 cells --- p.47 / Chapter 2.3.1.1 --- Immobilization of Vero E6 cells and SARS-CoV infected Vero E6 cells --- p.47 / Chapter 2.3.1.2 --- Preparation of monoclonal antibodies against SARS-CoV nsp10 --- p.48 / Chapter 2.3.1.3 --- Immunostaining of SARS-CoV nsp10 in Vero E6 cells and SARS-CoV VeroE6 cells --- p.48 / Chapter 2.3.1.4 --- Fluorescent microscopic visualization --- p.49 / Chapter 2.3.2 --- Detection of SARS-CoV nsplO expression in SARS-CoV infected convalescent patients' serum --- p.50 / Chapter 2.3.2.1 --- Western blotting of SARS-CoV nsp10 by SARS-CoV infected convalescent patients' serum --- p.50 / Chapter 2.4 --- Expression of GST fusion SARS-CoV nsp10 in E.coli --- p.51 / Chapter 2.4.1 --- Preparation of competent cells --- p.51 / Chapter 2.4.2 --- Small scale expression --- p.51 / Chapter 2.4.3 --- Large scale expression of GST-nsp10 in optimized conditions --- p.54 / Chapter 2.5 --- Purification of GST fusion SARS-CoV nsp10 --- p.55 / Chapter 2.5.1 --- Glutathione Sepharose 4B affinity chromatography --- p.55 / Chapter 2.5.2 --- Superdex 75 gel filtration chromatography --- p.56 / Chapter 2.6 --- "CD Measurement, NMR and Crystallization Study of SARS-CoV nsp10" --- p.57 / Chapter 2.6.1 --- CD measurement --- p.57 / Chapter 2.6.2 --- NMR spectroscopy --- p.58 / Chapter 2.6.3 --- Crystallization of nsp10 --- p.58 / Chapter 2.7 --- "Glutathione-S-Sepharose Pull-down assay, 2D Gel Electrophoresis and Mass Spectrometry" --- p.59 / Chapter 2.7.1 --- GST pull-down assay --- p.59 / Chapter 2.7.2 --- Two-dimension gel electrophoresis --- p.59 / Chapter 2.7.2.1 --- First dimensional isoelectric focusing (IEF) --- p.59 / Chapter 2.7.2.2 --- Second dimension SDS-PAGE --- p.60 / Chapter 2.7.2.3 --- Silver staining --- p.61 / Chapter 2.7.3 --- Protein identification by mass spectrometry --- p.63 / Chapter 2.7.3.1 --- Data acquisition --- p.65 / Chapter 2.8 --- Proliferative study of SARS-CoV nsp10 in VeroE6 Cell Line and Mouse Splenocytes --- p.66 / Chapter 2.8.1 --- Assay of mitogenic activity by 3H-thymidine incorporation --- p.66 / Chapter 2.9 --- "Cloning, Expression and Purification of GST fusion SARS-CoV RNA-dependent RNA Polymerase (RdRp) Full- length Protein" --- p.67 / Chapter 2.9.1 --- Construction of GST-RdRp-full length expression plasmid --- p.67 / Chapter 2.9.2 --- Expression and purification of GST-RdRp full-length protein --- p.68 / Chapter 2.10 --- "Cloning, Expression and Purification of GST Fusion SARS-CoV RNA-dependent RNA Polymerase (RdRp) Catalytic Domain" --- p.70 / Chapter 2.10.1 --- Construction of GST-RdRp Catalytic Domain (p64) and MBP-RdRp-p64 expression plasmids --- p.70 / Chapter 2.10.2 --- Expression and purification of GST fusion catalytic domain of SARS-CoV RdRp (GST-p64) --- p.71 / Chapter 2.10.3 --- Expression and purification of MBP fusion catalytic domain of SARS-CoV RdRp --- p.72 / Chapter 2.11 --- "Cloning, Expression and Purification of the His-thioredoxin Fusion N-terminal Domain of SARS-CoV RdRp (pET32h-pl2)" --- p.74 / Chapter 2.11.1 --- Construction of His-thioredoxin fusion N-terminal domain of SARS-CoV RdRp (pET32h-pl2) expression plasmid --- p.74 / Chapter 2.11.2 --- Expression and purification of His- thioredoxin fusion N-terminal domain of SARS-CoV RdRp (pET32h-pl2) --- p.74 / Chapter 2.12 --- Interaction Study of RdRp Catalytic Domain and N-terminal Domain --- p.76 / Chapter 2.13 --- Electrophoretic Mobility Shift Assay of SARS-CoV Genomic RNA Strands with RdRp Full-length sequence --- p.76 / Chapter 2.13.1 --- Preparation of RNA transcripts --- p.76 / Chapter 2.13.2 --- EMSA --- p.77 / Chapter 2.14 --- Non-radiometric and Radiometric RdRp Assays --- p.78 / Chapter 2.14.1 --- Non-radiometric RdRp assay--luciferase coupled enzyme assay --- p.78 / Chapter 2.14.2 --- Radiometric RdRp assay ´ؤ filter-binding enzyme assay --- p.79 / Chapter 2.15 --- Western Blot Analysis for Interaction Study --- p.80 / Chapter Chapter 3 --- Results and Discussion on SARS-CoV nsplO --- p.81 / Chapter 3.1 --- "Cloning, Expression and Purification of SARS-CoV nsp10 in Prokaryotic Expression System" --- p.81 / Chapter 3.1.1 --- Cloning and expression of SARS-CoV nsp 10 --- p.81 / Chapter 3.1.2 --- Purification of GST-nsp10 by GST affinity chromatography --- p.84 / Chapter 3.1.3 --- Purification of nsp10 by size exclusion chromatography --- p.85 / Chapter 3.1.4. --- "Yield, purity and stability of SARS-CoV nsp 10" --- p.88 / Chapter 3.2 --- SARS-CoV nsp10 Sequence Alignment and Protein Structure Prediction --- p.89 / Chapter 3.2.1. --- Sequence alignment of SAR-CoV nsp10 with known viral proteins --- p.91 / Chapter 3.2.2 --- Protein structure prediction - homology modeling --- p.93 / Chapter 3.3 --- Circular Dichroism Analysis of nsp10 --- p.96 / Chapter 3.3.1 --- CD spectrum of SARS-CoV nsp10 --- p.98 / Chapter 3.3.2. --- Effect of divalent metal ions on SARS-CoV nsp10 --- p.99 / Chapter 3.4 --- Nuclear Magnetic Resonance Analysis of nsp10 --- p.101 / Chapter 3.4.1 --- Sample preparation for NMR Experiment --- p.102 / Chapter 3.4.2 --- Protein structure determination by NMR --- p.103 / Chapter 3.5 --- Crystallization of SARS-CoV nsp10 --- p.105 / Chapter 3.5.1 --- Sample preparation of nsp10 for crystallization --- p.105 / Chapter 3.5.2 --- Screening conditions for crystallization --- p.106 / Chapter 3.6 --- "Antigenic, Immunofluorescene and Subcellular Localization Studies on the SARS-CoV nsp10" --- p.110 / Chapter 3.6.1 --- Antigenic and immunofluorescene studies on the SARS-CoV nsp10 --- p.110 / Chapter 3.6.2 --- Subcellular localization of SARS-CoV nsp10 --- p.115 / Chapter 3.7 --- Proliferative Study of nsp10 --- p.120 / Chapter 3.7.1. --- Influence of proliferative effect on the host cell --- p.121 / Chapter 3.8 --- A Proteomics Strategy for Interaction Study of nsp10 --- p.124 / Chapter 3.8.1 --- 2D SDS-PAGE analysis of proteins associating with the nsp10 bait --- p.125 / Chapter 3.8.2 --- Silver staining of proteins associating with the nsp10 bait and their identification by mass spectrometry --- p.127 / Chapter 3.9 --- Discussion on SARS-CoV nsp10 --- p.129 / Chapter Chapter 4 --- Results and Discussion on SARS-CoV RdRp / Chapter 4.1 --- "Cloning, Expression and Purification of SARS-CoV RdRp Full-length, Catalytic Domain and N-terminal Domain" --- p.139 / Chapter 4.2 --- Interaction Study of RdRp Catalytic Domain and its N-terminal Domain --- p.147 / Chapter 4.3 --- Functional Analysis of RNA Binding by the SARS-CoV RdRp --- p.149 / Chapter 4.4 --- Characterization of RdRp by Non-radioactive RdRp Assay ´ؤ Luciferase-coupled Enzyme Assay --- p.152 / Chapter 4.5 --- Characterization of RdRp by Radioactive RdRp Assay ´ؤ 32P Incorporation Assay --- p.157 / Chapter 4.6 --- Discussion on SARS-CoV RdRp --- p.161 / Chapter Chapter 5 --- General Discussion / General Discussion --- p.170 / Appendix --- p.172 / References --- p.189

Over the past several decades, there have been numerous attempts to utilize synthetic dsRNA to control tumor growth in animal models and clinical trials. Recently, it has become clear that intracellular dsRNA is more effective than extracellular dsRNA in promoting apoptosis and orchestrating adaptive immune response. To overcome the difficulty in delivering a large dose of synthetic dsRNA into tumors, while avoiding systemic toxicity we propose to deliver a RNA replicase-based plasmid DNA, hypothesizing that the dsRNA generated by the replicase-based plasmid in tumor cells will inhibit tumor growth. We evaluated the anti-tumor activity of a plasmid (pSIN-beta) that encodes the sindbis RNA replicase genes in mice with model tumors (TC-1 lung cancer cells or B16 melanoma cells) and compared it to a traditional pCMV-beta plasmid. In cell culture, transfection of tumor cells with pSIN-beta generated dsRNA. In mice with model tumors, pSIN-beta more effectively inhibited tumor growth than pCMV-beta, and in some cases, eradicated the tumors. RNA replicase-based plasmid may be exploited to generate intracellular dsRNA to control tumor growth. The feasibility of further improving the antitumor activity of the RNA replicase-based plasmid by targeting it into tumors cells was also evaluated. An epidermal growth factor (EGF)-conjugated, PEGylated cationic liposome was developed to deliver the RNA replicase-based plasmid, pSIN-beta, into EGFR-over-expressing human breast cancer cells (MDA-MB-468) in vitro and in vivo. Delivery of the pSIN-beta using the EGF receptor-targeted liposome more effectively controlled the growth of MDA-MB-468 tumors in mice than using un-targeted liposome. Finally the potential of further improving the antitumor activity of the pSIN-beta plasmid by incorporating interleukin-2 (IL2) gene into the plasmid was investigated. The resultant pSIN-IL2 plasmid was delivered to mouse melanoma cells that over-express the sigma receptor. The pSIN-IL2 plasmid was more effective at controlling the growth of B16 melanoma in mice when complexed with sigma receptor targeted AA-PEG-liposomes than with the untargeted liposomes. Importantly, the pSIN-IL2 plasmid was more effective than pSIN-beta plasmid at controlling the growth of B16 melanoma in mice, and B16-bearing mice that were treated with pSIN-IL2 had an elevated number of activated CD4+, CD8+, and natural killer cells, compared to those treated with pSIN-beta. / text

Les Flavivirus transmis par les moustiques comme le virus du Nil occidental, le virus de la dengue, le virus de la fièvre jaune, le virus de l’encéphalite japonaise et le virus Zika constituent des préoccupations croissantes de santé publique. Ils se sont répandus dans le monde au cours des dernières décennies, et les épidémies sont devenues plus fréquentes et plus sévères. Chaque année, des millions de personnes sont infectées et environ 50 000 patients décèdent d’infections à Flavivirus. Malgré les nombreux efforts de recherche, il n’y a actuellement aucun médicament antiviral spécifique disponible, et des nouvelles stratégies antivirales sont indispensables. Comprendre comment les Flavivirus fonctionnent au niveau moléculaire aidera à découvrir des nouvelles cibles pour l'intervention thérapeutique. Les Flavivirus ont un génome d'ARN simple brin de polarité positive qui code pour trois protéines structurales et huit protéines non structurales. Seules deux des huit protéines non structurales ont des activités enzymatiques. NS3 possède un domaine protéase et un domaine hélicase, et NS5 a un domaine méthyl- et guanylyltransférase et un domaine ARN polymérase ARN-dépendante. Ensemble, ils répliquent le génome viral. Ici, nous caractérisons l'interaction entre NS3 et NS5 dans le complexe de réplication du virus du Nil occidental pendant la synthèse d’ARN de polarité positive. Un modèle d'interaction comprenant NS3, NS5 et l’ARN viral a été développé basé sur des structures cristallines connues ainsi que des activités enzymatiques des deux protéines individuelles, et ce modèle a été soumis à des simulations de dynamique moléculaire. Les interactions potentielles entre les protéines NS3 et NS5 ont été identifiées. Les résidus impliqués dans ces interactions ont été mutés dans un réplicon du virus du Nil occidental et les effets de ces mutations sur la réplication virale ont été évalués. Une région particulière à la surface de la protéine NS3 a été identifiée comme étant cruciale pour la réplication virale, très probablement parce qu'elle interagit avec NS5. Cette région pourrait être une cible attrayante pour la recherche de composés qui pourraient interférer avec l'interaction entre NS3 et NS5 et donc posséder un potentiel antiviral intéressant. / Abstract : Mosquito-borne Flaviviruses like West Nile virus, Dengue virus, Yellow Fever virus, Japanese encephalitis virus, and Zika virus are increasing public health concerns. They have spread globally during the past decades, and outbreaks have recently become more frequent and more severe. Every year, millions of people are infected, and approximately 50,000 patients die from Flavivirus infections. Despite extensive research efforts, there are currently no specific antiviral drugs available, and new antiviral strategies are greatly needed. Understanding how Flaviviruses work on a molecular level will help in uncovering new points for therapeutic intervention. Flaviviruses have a single-stranded RNA genome of positive polarity that encodes three structural and eight non-structural proteins. Only two of the eight non-structural proteins have enzymatic activities. NS3 has an N-terminal protease domain and a C-terminal helicase domain, and NS5 has an N-terminal capping enzyme domain and a C-terminal RNA-dependent RNA polymerase domain. Together, they replicate the viral genome. Here we characterize the NS3:NS5 interaction within the West Nile virus RNA replicase complex during positive strand synthesis. An interaction model including NS3, NS5 and viral RNA was developed based on the known crystal structures as well as enzymatic activities of the two individual proteins, and this model was subjected to molecular dynamics simulations. Potential interactions between the NS3 and NS5 proteins were identified. Residues involved in these interactions were mutated in a West Nile virus replicon, and the effects of these mutations on viral replication were evaluated. One particular region on the surface of the NS3 protein was identified to be crucial for viral replication, most likely because it mediates the interaction with NS5. This region might be an attractive target for the search of compounds that could interfere with the NS3:NS5 interaction and therefore possess an interesting antiviral potential.

No description available.