Screening of cellular proteins that interact with the classical swine fever virus non-structural protein 5A by yeast two-hybrid analysis.

Classical swine fever virus (CSFV), the pathogen of classical swine fever (CSF), causes severe hemorrhagic fever and vascular necrosis in domestic pigs and wild boar. A large number of evidence has proven that non-structural 5A (NS5A) is not only a very important part of viral replication complex, but also can regulate host cell’s function; however, the underlying mechanisms remain poorly understood. In the current study, aiming to find more clues in understanding the molecular mechanisms of CSFV NS5A’s function, the yeast two-hybrid (Y2H) system was adopted to screen for CSFV NS5A interactive proteins in the cDNA library of the swine umbilical vein endothelial cell (SUVEC). Alignment with the NCBI database revealed 16 interactive proteins: DDX5, PSMC3, NAV1, PHF5A, GNB2L1, CSDE1, HSPA8, BRMS1, PPP2R3C, AIP, TMED10, POLR1C, TMEM70, METAP2, CHORDC1 and COPS6. These proteins are mostly related to gene transcription, protein folding, protein degradation and metabolism. The interactions detected by the Y2H system should be considered as preliminary results. Since identifying novel pathways and host targets, which play essential roles during infection, may provide potential targets for therapeutic development. The finding of proteins obtained from the SUVEC cDNA library that interact with the CSFV NS5A protein provide valuable information for better understanding the interactions between this viral protein and the host target proteins.

Sequencing of E2 and NS5A regions of HCV genotype 3a in Brazilian patients with chronic hepatitis

Hepatitis C virus (HCV) is a major cause of liver disease throughout the world. The NS5A and E2 proteins of HCV genotype 1 were reported to inhibit the double-stranded (ds) RNA-dependent protein kinase (PKR), which is involved in the cellular antiviral response induced by interferon (IFN). The response to IFN therapy is quite different between genotypes, with response rates among patients infected with types 2 and 3 that are two-three-fold higher than in patients infected with type 1. Interestingly, a significant percentage of HCV genotype 3-infected patients do not respond to treatment at all. The aim of this paper was to analyse the sequences of fragments of the E2 and NS5A regions from 33 outpatients infected with genotype 3a, including patients that have responded (SVR) or not responded (NR) to treatment. HCV RNA was extracted and amplified with specific primers for the NS5A and E2 regions and the PCR products were then sequenced. The sequences obtained covered amino acids (aa) 636-708 in E2 and in NS5A [including the IFN sensitivity determining region (ISDR), PKR-binding domain and extended V3 region)]. In the E2 and NS5A regions, we did observe aa changes among patients, but these changes were not statistically significant between the SVR and NR groups. In conclusion, our results suggest that the ISDR domain is not predictive of treatment success in patients infected with HCV genotype 3a.

Cloning and identification of human gene 3 transactivated by nonstructural protein 5A of hepatitis C virus / 解放军医学杂志

Objective To screen and clone the target genes transactivated by nonstructural protein 5A (NS5A) of hepatitis C virus (HCV). Methods The mRNA was isolated from HepG2 cells transfected with pcDNA3.1(-)-NS5A and pcDNA3.1(-) empty vector, respectively. Suppression subtractive hybridization (SSH) method was employed to analyze the differentially expressed DNA sequence between the two groups. The obtained sequences were searched for homologous DNA sequence from GenBank. The new gene with no homology with known genes in this database was confirmed, and electric polymerase chain reaction was conducted for cloning the full-length DNA of the new gene and in conjunction with Kozak rule and the terminus of polyadenyl signal sequence. The reverse transcription PCR (RT-PCR) was used to amplify the new gene from mRNA of HepG2 cell as the template. The coding sequence of the new gene was deduced according to the nucleotide sequence. Results A new gene with unknown function was named as NS5ATP3. The nucleotide sequence of the NS5ATP3 gene and its corresponding amino acid have been determined, which contained 1 572nt and 524aa. The sequence of the NS5ATP3 gene was deposited into GenBank, with the accession number AF529364. Conclusions NS5ATP3 gene transactivated by HCV NS5A protein was cloned and identified successfully by combining molecular biological technology and bioinformatics technique. These results will pave the way for the study of the molecular mechanism of the transactivating effects of HCV NA5A protein and the development of new therapy for chronic hepatitis C.

SUPPRESSION SUBTRACTIVE HYBRIDIZATION FOR CLONING OF GENES TRANSACTIVATED BY NS5A PROTEIN OF HEPATITIS C VIRUS / 解放军医学杂志

To construct a subtractive cDNA library of genes transactivated by NS5A protein of hepatitis C virus with suppression subtractive hybridization technique, the mRNA was isolated from HepG2 cells transfected with pcDNA3 1(-) NS5A and pcDNA3 1(-) empty vector, respectively, then the cDNA was synthesized. After restriction enzyme RsaI digestion, small sized cDNAs were obtained. Then the tester cDNA was divided into two groups and ligated to the specific adaptor 1 and adaptor 2, respectively. After the tester cDNA was hybridized with the driver cDNA twice and underwent two times of nested PCR, it was then subcloned into T/A plasmid vectors to set up the subtractive library. Amplification of the library was carried out with E. coli strain JM109. The cDNA was sequenced and analyzed in GenBank with Blast search after PCR. The amplified library contained 121 positive clones. Colony PCR showed that 115 clones contained 200- 1 000 bp inserts. Sequence analysis was performed in 90 clones, and the full length sequences were obtained with bioinformatics method. Altogether 46 kinds of coding sequences were acquired, which consisted of 31 kinds of known and 15 kinds of unknown ones. The obtained sequences might be target genes transactivated by NS5A protein of HCV, among which some genes coding proteins involved in cell cycle regulation, cell apoptosis, signal transduction pathway and tumour development. The results indicated that the subtractive library of genes transactivated by NS5A protein of HCV was constructed successfully, which brought some new clues for studying the biological functions and pathogenesis of the viral proteins