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Title: Interaction of NS3 with viral and host proteins and RNA during hepatitis C virus replication
Author: Sifennasr, Nadia
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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Hepatitis C virus (HCV) is a major cause of viral hepatitis. The World Health Organization (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 immune system and to establish persistent infections, which often result in chronic liver disease. HCV encodes a long polyprotein which contain structural and non-structural proteins. 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 biotinylated 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 investigate the role of host genes RAB40B, RAB27B, TXNIP and Staufen 1, which had previously been shown to be important for HCV replication, on NS3 and NS3/4A proteins expressed 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 silencing 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 protein 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.
Supervisor: Karayiannis, Peter ; McGarvey, Michael Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available