Soluble egg antigen of Schistosoma Haematobium induces HCV replication in PBMC from patients with chronic HCV infection

BACKGROUND: This study was conducted to examine, in vitro , the effect of soluble egg antigen (SEA) of S. haematobium on intracellular HCV RNA load in peripheral mononuclear cells (PBMC) as well as on cell proliferation in patients with chronic HCV infection. METHODS: PBMC from 26 patients with chronic HCV infection were cultured for 72 hours in presence and absence of 50 μg SEA/ml medium. Intracellular HCV RNA quantification of plus and minus strands was assessed before and after stimulation. PBMC from five healthy subjects were cultured for 7 days, flow cytometric analysis of DNA content was used to assess the mitogenic effect of SEA on PBMC proliferation compared to phytoheamaglutinine (PHA). RESULTS: Quantification of the intracellular viral load showed increased copy number/cell of both or either viral strands after induction with SEA in 18 of 26 patients (69.2%) thus indicating stimulation of viral replication. Flow cytometric analysis showed that mean ± S.D. of percent values of cell proliferation was induced from 3.2 ± 1.5% in un-stimulated cells to 16.7 ± 2.5 % and 16.84 ± 1.7 % in cells stimulated with PHA and SEA respectively. CONCLUSION: the present study supports earlier reports on SEA proliferative activity on PBMC and provides a strong evidence that the higher morbidity observed in patients co-infected with schistosomiasis and HCV is related, at least in part, to direct stimulation of viral replication by SEA

Two RNA-binding motifs in eIF3 direct HCV IRES-dependent translation.

The initiation of protein synthesis plays an essential regulatory role in human biology. At the center of the initiation pathway, the 13-subunit eukaryotic translation initiation factor 3 (eIF3) controls access of other initiation factors and mRNA to the ribosome by unknown mechanisms. Using electron microscopy (EM), bioinformatics and biochemical experiments, we identify two highly conserved RNA-binding motifs in eIF3 that direct translation initiation from the hepatitis C virus internal ribosome entry site (HCV IRES) RNA. Mutations in the RNA-binding motif of subunit eIF3a weaken eIF3 binding to the HCV IRES and the 40S ribosomal subunit, thereby suppressing eIF2-dependent recognition of the start codon. Mutations in the eIF3c RNA-binding motif also reduce 40S ribosomal subunit binding to eIF3, and inhibit eIF5B-dependent steps downstream of start codon recognition. These results provide the first connection between the structure of the central translation initiation factor eIF3 and recognition of the HCV genomic RNA start codon, molecular interactions that likely extend to the human transcriptome

A novel role for Gemin5 in mRNA translation

In eukaryotic cells translation initiation occurs through two alternative mechanisms, a cap-dependent operating in the majority of mRNAs, and a 5′-end-independent driven by internal ribosome entry site (IRES) elements, specific for a subset of mRNAs. IRES elements recruit the translation machinery to an internal position in the mRNA through a mechanism involving the IRES structure and several trans-acting factors. Here, we identified Gemin5 protein bound to the foot-and-mouth disease virus (FMDV) and hepatitis C virus (HCV) IRES using two independent approaches, riboproteomic analysis and immunoprecipitation of photocroslinked factors. Functional analysis performed in Gemin5 shRNA-depleted cells, or in in vitro translation reactions, revealed an unanticipated role of Gemin5 in translation control as a down-regulator of cap-dependent and IRES-driven translation initiation. Consistent with this, pull-down assays showed that Gemin5 forms part of two distinct complexes, a specific IRES-ribonucleoprotein complex and an IRES-independent protein complex containing eIF4E. Thus, beyond its role in snRNPs biogenesis, Gemin5 also functions as a modulator of translation activity

A conserved structure within the HIV gag open reading frame that controls translation initiation directly recruits the 40S subunit and eIF3

Translation initiation on HIV genomic RNA relies on both cap and Internal Ribosome Entry Site (IRES) dependant mechanisms that are regulated throughout the cell cycle. During a unique phenomenon, the virus recruits initiation complexes through RNA structures located within Gag coding sequence, downstream of the initiation codon. We analyzed initiation complexes paused on the HIV-2 gag IRES and revealed that they contain all the canonical initiation factors except eIF4E and eIF1. We report that eIF3 and the small ribosomal subunit bind HIV RNA within gag open reading frame. We thus propose a novel two step model whereby the initial event is the formation of a ternary eIF3/40S/IRES complex. In a second step, dependent on most of the canonical initiation factors, the complex is rearranged to transfer the ribosome on the initiation codons. The absolute requirement of this large structure for HIV translation defines a new function for a coding region. Moreover, the level of information compaction within this viral genome reveals an additional level of evolutionary constraint on the coding sequence. The conservation of this IRES and its properties in rapidly evolving viruses suggest an important role in the virus life cycle and highlight an attractive new therapeutic target

Analysis of natural variants of the hepatitis C virus internal ribosome entry site reveals that primary sequence plays a key role in cap-independent translation

The HCV internal ribosome entry site (IRES) spans a region of ∼340 nt that encompasses most of the 5′ untranslated region (5′UTR) of the viral mRNA and the first 24–40 nt of the core-coding region. To investigate the implication of altering the primary sequence of the 5′UTR on IRES activity, naturally occurring variants of the 5′UTR were isolated from clinical samples and analyzed. The impact of the identified mutations on translation was evaluated in the context of RLuc/FLuc bicistronic RNAs. Results show that depending on their location within the RNA structure, these naturally occurring mutations cause a range of effects on IRES activity. However, mutations within subdomain IIId hinder HCV IRES-mediated translation. In an attempt to explain these data, the dynamic behavior of the subdomain IIId was analyzed by means of molecular dynamics (MD) simulations. Despite the loss of function, MD simulations predicted that mutant G266A/G268U possesses a structure similar to the wt-RNA. This prediction was validated by analyzing the secondary structure of the isolated IIId RNAs by circular dichroism spectroscopy in the presence or absence of Mg2+ ions. These data strongly suggest that the primary sequence of subdomain IIId plays a key role in HCV IRES-mediated translation

Molecular cloning and characterization of the common 1b subtype of HCV from Turkey

Ankara : Department of Molecular Biology and Genetics and Institute of Engineering and Science, Bilkent University, 1999.Thesis (Master's) -- Bilkent University, 1999.Includes bibliographical references leaves 64-71.Hepatitis C Virus is a major cause of acute and chronic hepatitis worldwide. 80-90% of Hepatitis C Virus infections become chronic and 75% of these cases lead to liver disease, including cirrhosis, liver failure and hepatocellular carcinoma. Hepatitis C Virus was first identified by molecular cloning of the viral genome in 1989. Hepatitis C Virus is an enveloped virus containing a positive stranded RNA genome with a size of around 9.5 kilobases. In terms of genomic organization, it was accepted as a member of Flaviviridae family as a new genus named Hepaciviruses. The single-stranded RNA genome encodes a single open reading frame, which is transcribed into a single polypeptide of 3010 or 3030 amino acids and cleaved into viral proteins Core, E l, E2/p7, NS2, NS3, NS4A, NS4B, NS5A, NS5B by host and viral proteases. Sequencing, serotyping and RFLP studies indicate that Hepatitis C Virus genome is highly variable. There are six distinct genotypes and at least 74 subtypes with different distributions between the geographic areas. Variability is not equally distributed throughout the genome. 5' UTR, some parts of the 3' UTR and capsid protein are the most conserved regions. The predominant genotype in the Turkish population was found to be lb by sequencing of the 5-UTR. In this study, the entire sequence encompassing the complete coding region and partial non coding regions of the genotype lb obtained from a HCV-infected Turkish patient was cloned to investigate its evolutionary relationship with other genotypes and to study its overall genome organization,. In order to characterize the viral genome, viral RNA was extracted from the serum, cDNA was synthesized, the HCV genome was amplified by PCR in 7 overlapping fragments, PCR fragments were cloned into bacterial vectors and cloned inserts were sequenced by automated sequencing methodology. The partial sequence data covering 70% of the cloned HCV genome indicate that the Turkish lb genotype displays high homology to other lb genotypes, but differs from others by distinct amino acid changes. To our knowledge, this is the first report about the HCV genome structure from Turkey. The HCV subgenomic fragments obtained here will serve to further molecular and immunologic studies on this dominant form of HCV found in Turkish patients.Öztan, AslıM.S

Screening for the HCV IRES interacting proteins

Virus žloutenky typu C (HCV) představuje celosvětově rozšířený patogen infikující až 3 % lidské populace. V posledních letech se výzkum nových léčiv proti tomuto viru zaměřuje na jednotlivé kroky v jeho životním cyklu, mimo jiné na iniciaci translace. V případě HCV je iniciace translace závislá na vnitřním vazebném místě pro ribozóm (IRES) a kromě složek translačního aparátu se na ní podílí i další buněčné komponenty tzv. IRES trans-účinkující faktory (ITAF). Tato práce navazuje na předchozí výzkum naší laboratoře zaměřený na hledání nových ITAF. Pro hledání potenciálních ITAF zvyšujících aktivitu IRES HCV byly připraveny nové rekombinantní plazmidové vektory, nové referenční kvasinkové kmeny a byly optimalizovány selekční podmínky připraveného sytému. Rozdíly v růstových vlastnostech referenčních kmenů byly zkoumány a kvantifikovány v selekčních i neselekčních podmínkách. Dále byla provedena série pilotních vysokovýtěžkových transformací kvasinkového kmene pJ69-4A, nesoucího bicistronní konstrukt s IRES HCV, lidskou expresní cDNA knihovnou s cílem optimalizovat transformační účinnost a selekční podmínky a v neposlední řadě i s cílem pokusit se identifikovat nové ITAF. Několik desítek náhodně vybraných klonů získaných v selekčních podmínkách z těchto transformací bylo podrobeno analýze růstových vlastností,...Hepatitis C virus (HCV) is a worldwide spread pathogen infecting up to 3 % of the human population. Nowadays, research of new drugs against this virus is focused on the individual steps in its life cycle, including the translation initiation. In the case of HCV translation initiation is dependent on the internal ribosome entry site (IRES). Besides of components of the translational machinery also other components of the cell, so called IRES trans-acting factors (ITAF), contribute to its proper progress. This work continues in previous research of our laboratory focused on searching for new ITAF. In order to search for potential ITAF increasing HCV IRES activity new recombinant plasmid vectors and reference strains were prepared and selection conditions of the selection system were optimized. The differences in the growth characteristics of the reference strains were analyzed and quantified under selective and non-selective conditions. A set of pilot high efficiency transformations of the yeast strain pJ69-4A carrying bicistronic construct with HCV IRES were conducted using human expression cDNA library in order to optimize the efficiency of transformation and selection conditions and to attempt to identify new ITAF. Several dozens of randomly selected clones from these transformations obtained under...Department of Genetics and MicrobiologyKatedra genetiky a mikrobiologieFaculty of SciencePřírodovědecká fakult

Exploration of new uracil-based compounds as novel inhibitors of Hepatitis C Virus replication

Hepatitis C Virus (HCV) is a major public health problem worldwide. While highly efficacious directly-acting antiviral agents have been developed in recent years, their high costs and relative inaccessibility make their use limited. In this thesis, new uracil-based compounds have been evaluated as potential antiviral drugs against HCV. Using several biochemical and virological assays to investigate virus infection and replication, it has been shown that these compounds are able to significantly reduce viral genomic replication with their IC50 values in the nanomolar range. Finally, these compounds have been shown to block the de novo RNA synthesis and that effect is dependent on a chemical structure of the compounds

Interaction of NS3 with viral and host proteins and RNA during hepatitis C virus replication

Hepatitis C virus (HCV) is a major cause of viral hepatitis. The World Health Organiz a- tion (WHO) estimates the global prevalence of HCV to be approximately 2.2–3.0% with 130– 170 million infected individuals worldwide. HCV has the ability to evade the i m- m une system and to establish persistent infections, which often result in chronic liver di s- ease. HCV encodes a long polyprotein which contain structural and non-structural pr o- teins. The Non-structural protein NS3 is likely to be involved in viral RNA replication by interacting with viral and host components. In this study, a purified recombinant full- length NS3 protein expressed in E. coli was examined for its ability to interact with bi otinylated full length HCV JFH-1 genomic RNA and the 3’ terminal of HCV negative strand RNA. The results showed that NS3 could bind to both full length and the 3’ end negative strand RNAs. RNA interference (siRNA) studies were also carried out to inve s- tigate the role of host genes RAB40B, RAB27B, TXNIP and Staufen 1, which had prev i- ously been shown to be important for HCV replication, on NS3 and NS3/4A proteins e x- pressed by adenovirus vectors using quantitative real-time polymerase chain reaction (qRT-PCR) and FACS analysis. While there were reductions in the levels of the NS3 and NS3/4A transcripts when the expression of these host genes was knocked down by siRNAs, the NS3 and NS3/4A proteins appeared to be more stable when RAB40B, RAB27B, but not TXNIP or Staufen 1, were knocked. One possibility is that although s i- lencing of these host genes may reduce HCV replication, this may also increase in the stability of NS3 or NS3/4A proteins by altering their location within the cell due to the absence of these host proteins. Previously it has been shown that NS3 and NS3/4A pr o- tein expression decreased the level of expression of several proteins, which were part of the innate immune response, leading to interferon production. In this study, it was found that the expression of NS3 and NS3/4A proteins, using adenovirus vectors, restored RIG- I, MDA5 and MAVS expression levels in response to dsRNA stimulation, indicating that the NS3 protein may have a role in regulating the expression of these host genes.Open Acces